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Sample records for chromophoric substrate analogue

  1. Substrate analogues for isoprenoid enzymes

    Energy Technology Data Exchange (ETDEWEB)

    Stremler, K.E.

    1987-01-01

    Diphosphonate analogues of geranyl diphosphate, resistant to degradation by phosphatases, were found to be alternate substrates for the reaction with farnesyl diphosphate synthetase isolated from avian liver. The difluoromethane analogue was shown to be the better alternate substrate, in agreement with solvolysis results which indicate that the electronegativity of the difluoromethylene unit more closely approximates that of the normal bridging oxygen. The usefulness of the C/sub 10/ difluoro analogue, for detecting low levels of isoprenoid enzymes in the presence of high levels of phosphatase activity, was demonstrated with a cell-free preparation from lemon peel. A series of C/sub 5/ through C/sub 15/ homoallylic and allylic diphosphonates, as well as two 5'-nucleotide diphosphonates, was prepared in high overall yield using the activation-displacement sequence. Radiolabeled samples of several of the allylic diphosphonates were prepared with tritium located at C1. A series of geraniols, stereospecifically deuterated at C1, was prepared. The enantiomeric purities and absolute configurations were determined by derivatization as the mandelate esters for analysis by /sup 1/H NMR. The stereochemistry of the activation-displacement sequence was examined using C1-deuterated substrates.

  2. Dual Fluorescence in GFP Chromophore Analogues: Chemical Modulation of Charge Transfer and Proton Transfer Bands.

    Science.gov (United States)

    Chatterjee, Tanmay; Mandal, Mrinal; Das, Ananya; Bhattacharyya, Kalishankar; Datta, Ayan; Mandal, Prasun K

    2016-04-14

    Dual fluorescence of GFP chromophore analogues has been observed for the first time. OHIM (o-hydroxy imidazolidinone) shows only a charge transfer (CT) band, CHBDI (p-cyclicamino o-hydroxy benzimidazolidinone) shows a comparable intensity CT and PT (proton transfer) band, and MHBDI (p-methoxy o-hydroxy benzimidazolidinone) shows a higher intensity PT band. It could be shown that the differential optical behavior is not due to conformational variation in the solid or solution phase. Rather, control of the excited state electronic energy level and excited state acidity constant by functional group modification could be shown to be responsible for the differential optical behavior. Chemical modification-induced electronic control over the relative intensity of the charge transfer and proton transfer bands could thus be evidenced. Support from single-crystal X-ray structure, NMR, femtosecond to nanosecond fluorescence decay analysis, and TDDFT-based calculation provided important information and thus helped us understand the photophysics better.

  3. Highly Fluorescent Green Fluorescent Protein Chromophore Analogues Made by Decorating the Imidazolone Ring.

    Science.gov (United States)

    Gutiérrez, Sara; Martínez-López, David; Morón, María; Sucunza, David; Sampedro, Diego; Domingo, Alberto; Salgado, Antonio; Vaquero, Juan J

    2015-12-14

    The synthesis and photophysical behavior of an unexplored family of green fluorescent protein (GFP)-like chromophore analogues is reported. The compound (Z)-4-(4-hydroxybenzylidene)-1-propyl-2-(propylamino)-1H-imidazol-5(4 H)-one (p-HBDNI, 2 a) exhibits significantly enhanced fluorescence properties relative to the parent compound (Z)-5-(4-hydroxybenzylidene)-2,3-dimethyl-3,5-dihydro-4H-imidazol-4-one (p-HBDI, 1). p-HBDNI was considered as a model system and the photophysical properties of other novel 2-amino-3,5-dihydro-4H-imidazol-4-one derivatives were evaluated. Time-dependent DFT calculations were carried out to rationalize the results. The analogue AIDNI (2 c), in which the 4-hydroxybenzyl group of p-HBDNI was replaced by an azaindole group, showed improved photophysical properties and potential for cell staining. The uptake and intracellular distribution of 2 c in living cells was investigated by confocal microscopy imaging.

  4. Ultrafast excited state dynamics of the green fluorescent protein chromophore and its kindling fluorescent protein analogue.

    Science.gov (United States)

    Addison, Kiri; Heisler, Ismael A; Conyard, Jamie; Dixon, Tara; Page, Philip C Bulman; Meech, Stephen R

    2013-01-01

    Fluorescent proteins exhibit a very diverse range of photochemical behaviour, from efficient fluorescence through photochromism to photochemical reactivity. Remarkably this diverse behaviour arises from chromophores which have very similar structures. Here we describe measurements and modelling of the excited state dynamics in the chromophores of GFP (HBDI) and the kindling fluorescent protein, KFP (FHBMI). The methods are ultrafast fluorescence spectroscopy with sub 50 fs time resolution and the modelling is based on the Smoluchowski equation. The excited state decays of both chromophores are very fast, longer for their anions than for the neutral form and independent of wavelength. Detailed studies show the mean fluorescence wavelength to be independent of time. The excited state decay times are also observed to be a very weak function of solvent polarity and viscosity. These results are modelled utilising recently calculated potential energy surfaces for the ground and excited states as a function of the twist coordinates about the two bridging bonds of the chromophore. For FHBMI and the scarce data on the neutral HBDI the calculations are not successful suggesting the need for refinement of these potential energy surfaces. For HBDI in methanol the simulation is successful provided a strong dependence of the radiationless decay rate on the coordinate is assumed. Such dependence should be included in future calculations of excited state dynamics. When the simulations are extended to more viscous solvents they fail to reproduce the observed weak viscosity dependence. The implications of these results for the nature of the coordinate leading to radiationless decay in the chromophore and for the photodynamics of fluorescent proteins are discussed.

  5. Excited-state intramolecular proton transfer molecules bearing o-hydroxy analogues of green fluorescent protein chromophore.

    Science.gov (United States)

    Chuang, Wei-Ti; Hsieh, Cheng-Chih; Lai, Chin-Hung; Lai, Cheng-Hsuan; Shih, Chun-Wei; Chen, Kew-Yu; Hung, Wen-Yi; Hsu, Yu-Hsiang; Chou, Pi-Tai

    2011-10-21

    o-Hydroxy analogues, 1a-g, of the green fluorescent protein chromophore have been synthesized. Their structures and electronic properties were investigated by X-ray single-crystal analyses, electrochemistry, and luminescence properties. In solid and nonpolar solvents 1a-g exist mainly as Z conformers that possess a seven-membered-ring hydrogen bond and undergo excited-state intramolecular proton transfer (ESIPT) reactions, resulting in a proton-transfer tautomer emission. Fluorescence upconversion dynamics have revealed a coherent type of ESIPT, followed by a fast vibrational/solvent relaxation (decay of a few to several tens of picoseconds was resolved in cyclohexane. Accordingly, the proton-transfer tautomer emission intensity is moderate (0.08 in 1e) to weak (∼10(-4) in 1a) in cyclohexane. The stronger intramolecular hydrogen bonding in 1g suppresses the rotation of the aryl-alkene bond, resulting in a high yield of tautomer emission (Φ(f) ≈ 0.2). In the solid state, due to the inhibition of exo-C(5)-C(4)-C(3) rotation, intense tautomer emission with a quantum yield of 0.1-0.9 was obtained for 1a-g. Depending on the electronic donor or acceptor strength of the substituent in either the HOMO or LUMO site, a broad tuning range of the emission from 560 (1g) to 670 nm (1a) has been achieved.

  6. Introduction of an electron push-pull system yields a planar Red Kaede fluorescence protein chromophore analogue stabilized by a C = O… interaction

    Indian Academy of Sciences (India)

    Ashish Singh; Basanta Kumar Rajbongshi; Gurunath Ramanathan

    2015-05-01

    Crystal structures of four red kaede fluorescence protein chromophore analogues are reported here. Molecules I-III adopt a non-planar geometry stabilized by … stacking and hydrogen bonding. Introduction of an electron push-pull system induces molecule IV to be planar and a C = O… supramolecular interaction is observed as well. Strong electron withdrawing and donating groups also ensure formation of a higher order two and three dimensional supramolecular architecture through hydrogen bonds in molecules I and IV. All the analogues exhibit good photoluminescence properties and emit in the red region with excellent quantum yields.

  7. Structure of human aspartyl aminopeptidase complexed with substrate analogue: insight into catalytic mechanism, substrate specificity and M18 peptidase family

    Directory of Open Access Journals (Sweden)

    Chaikuad Apirat

    2012-06-01

    Full Text Available Abstract Backround Aspartyl aminopeptidase (DNPEP, with specificity towards an acidic amino acid at the N-terminus, is the only mammalian member among the poorly understood M18 peptidases. DNPEP has implicated roles in protein and peptide metabolism, as well as the renin-angiotensin system in blood pressure regulation. Despite previous enzyme and substrate characterization, structural details of DNPEP regarding ligand recognition and catalytic mechanism remain to be delineated. Results The crystal structure of human DNPEP complexed with zinc and a substrate analogue aspartate-β-hydroxamate reveals a dodecameric machinery built by domain-swapped dimers, in agreement with electron microscopy data. A structural comparison with bacterial homologues identifies unifying catalytic features among the poorly understood M18 enzymes. The bound ligands in the active site also reveal the coordination mode of the binuclear zinc centre and a substrate specificity pocket for acidic amino acids. Conclusions The DNPEP structure provides a molecular framework to understand its catalysis that is mediated by active site loop swapping, a mechanism likely adopted in other M18 and M42 metallopeptidases that form dodecameric complexes as a self-compartmentalization strategy. Small differences in the substrate binding pocket such as shape and positive charges, the latter conferred by a basic lysine residue, further provide the key to distinguishing substrate preference. Together, the structural knowledge will aid in the development of enzyme-/family-specific aminopeptidase inhibitors.

  8. Substrate profiling of glutathione S-transferase with engineered enzymes and matched glutathione analogues.

    Science.gov (United States)

    Feng, Shan; Zhang, Lei; Adilijiang, Gulishana; Liu, Jieyuan; Luo, Minkui; Deng, Haiteng

    2014-07-01

    The identification of specific substrates of glutathione S-transferases (GSTs) is important for understanding drug metabolism. A method termed bioorthogonal identification of GST substrates (BIGS) was developed, in which a reduced glutathione (GSH) analogue was developed for recognition by a rationally engineered GST to label the substrates of the corresponding native GST. A K44G-W40A-R41A mutant (GST-KWR) of the mu-class glutathione S-transferases GSTM1 was shown to be active with a clickable GSH analogue (GSH-R1) as the cosubstrate. The GSH-R1 conjugation products can react with an azido-based biotin probe for ready enrichment and MS identification. Proof-of-principle studies were carried to detect the products of GSH-R1 conjugation to 1-chloro-2,4-dinitrobenzene (CDNB) and dopamine quinone. The BIGS technology was then used to identify GSTM1 substrates in the Chinese herbal medicine Ganmaocongji.

  9. Catalytic irreversible inhibition of bacterial and plant arginine decarboxylase activities by novel substrate and product analogues.

    Science.gov (United States)

    Bitonti, A J; Casara, P J; McCann, P P; Bey, P

    1987-02-15

    Arginine decarboxylase (ADC) activity from Escherichia coli and two plant species (oats and barley) was inhibited by five new substrate (arginine) and product (agmatine) analogues. The five compounds, (E)-alpha-monofluoromethyldehydroarginine (delta-MFMA), alpha-monofluoromethylarginine (MFMA), alpha-monofluoromethylagatine (FMA), alpha-ethynylagmatine (EA) and alpha-allenylagmatine (AA), were all more potent inhibitors of ADC activity than was alpha-difluoromethylarginine (DFMA), the only irreversible inhibitor of this enzyme described previously. The inhibition caused by the five compounds was apparently enzyme-activated and irreversible, since the loss of enzyme activity followed pseudo-first-order kinetics, was time-dependent, the natural substrate of ADC (arginine) blocked the effects of the inhibitors, and the inhibition remained after chromatography of inhibited ADC on Sephadex G-25 or on overnight dialysis of the enzyme. DFMA, FMA, delta-MFMA and MFMA were effective at very low concentrations (10 nM-10 microM) at inhibiting ADC activity in growing E. coli. FMA was also shown to deplete putrescine effectively in E. coli, particularly when combined with an inhibitor of ornithine decarboxylase, alpha-monofluoromethyl-putrescine. The potential uses of the compounds for the study of the role of polyamine biosynthesis in bacteria and plants is discussed.

  10. 4-Oxalocrotonate tautomerase, its homologue YwhB, and active vinylpyruvate hydratase : Synthesis and evaluation of 2-fluoro substrate analogues

    NARCIS (Netherlands)

    Johnson, William H; Wang, Susan C; Stanley, Thanuja M; Czerwinski, Robert M; Almrud, Jeffrey J; Poelarends, Gerrit J; Murzin, Alexey G; Whitman, Christian P

    2004-01-01

    A series of 2-fluoro-4-alkene and 2-fluoro-4-alkyne substrate analogues were synthesized and examined as potential inhibitors of three enzymes: 4-oxalocrotonate tautomerase (4-OT) and vinylpyruvate hydratase (VPH) from the catechol meta-fission pathway and a closely related 4-OT homologue found in B

  11. Evaluation of analogues of GalNAc as substrates for enzymes of the mammalian GalNAc salvage pathway.

    Science.gov (United States)

    Pouilly, Sabrina; Bourgeaux, Vanessa; Piller, Friedrich; Piller, Véronique

    2012-04-20

    Changes in glycosylation are correlated to disease and associated with differentiation processes. Experimental tools are needed to investigate the physiological implications of these changes either by labeling of the modified glycans or by blocking their biosynthesis. N-Acetylgalactosamine (GalNAc) is a monosaccharide widely encountered in glycolipids, proteoglycans, and glycoproteins; once taken up by cells it can be converted through a salvage pathway to UDP-GalNAc, which is further used by glycosyltransferases to build glycans. In order to find new reporter molecules able to integrate into cellular glycans, synthetic analogues of GalNAc were prepared and tested as substrates of both enzymes acting sequentially in the GalNAc salvage pathway, galactokinase 2 (GK2) and uridylpyrophosphorylase AGX1. Detailed in vitro assays identified the GalNAc analogues that can be transformed into sugar nucleotides and revealed several bottlenecks in the pathway: a modification on C6 is not tolerated by GK2; AGX1 can use all products of GK2 although with various efficiencies; and all analogues transformed into UDP-GalNAc analogues except those with alterations on C4 are substrates for the polypeptide GalNAc transferase T1. Besides, all analogues that could be incorporated in vitro into O-glycans were also integrated into cellular O-glycans as attested by their detection on the cell surface of CHO-ldlD cells. Altogether our results show that GalNAc analogues can help to better define structural requirements of the donor substrates for the enzymes involved in GalNAc metabolism, and those that are incorporated into cells will prove valuable for the development of novel diagnostic and therapeutic tools.

  12. ()-Garner aldehyde derived Baylis-Hillman adduct: A potential substrate for the synthesis of D- phytosphinosine analogue

    Indian Academy of Sciences (India)

    Gulshan Kumar; Amanpreet Kaur; Vasundhara Singh

    2014-11-01

    A short, facile and efficient synthesis of D-lyxo-phytosphingosine analogue has been achieved. The key steps involved are the Baylis-Hillman reaction of (S)-Garner aldehyde with methyl acrylate to obtain the corresponding adduct as the potential substrate, to which was added decylmagnesium bromide to obtain the E-trisubstituted alkene followed by OsO4/NMO mediated dihydroxylation gave the desired D-lyxophytosphingosine analogue intermediate diol which on acid hydrolysis resulted in the formation of the target molecule in good yield.

  13. A biocatalytic approach to capuramycin analogues by exploiting a substrate permissive N-transacylase CapW.

    Science.gov (United States)

    Liu, Xiaodong; Jin, Yuanyuan; Cai, Wenlong; Green, Keith D; Goswami, Anwesha; Garneau-Tsodikova, Sylvie; Nonaka, Koichi; Baba, Satoshi; Funabashi, Masanori; Yang, Zhaoyong; Van Lanen, Steven G

    2016-04-28

    Using the ATP-independent transacylase CapW required for the biosynthesis of capuramycin-type antibiotics, we developed a biocatalytic approach for the synthesis of 43 analogues via a one-step aminolysis reaction from a methyl ester precursor as an acyl donor and various nonnative amines as acyl acceptors. Further examination of the donor substrate scope for CapW revealed that this enzyme can also catalyze a direct transamidation reaction using the major capuramycin congener as a semisynthetic precursor. Biological activity tests revealed that a few of the new capuramycin analogues have significantly improved antibiotic activity against Mycobacterium smegmatis MC2 155 and Mycobacterium tuberculosis H37Rv. Furthermore, most of the analogues are able to be covalently modified by the phosphotransferase CapP/Cpr17 involved in self resistance, providing critical insight for future studies regarding clinical development of the capuramycin antimycobacterial antibiotics.

  14. The catalytic mechanism of indole-3-glycerol phosphate synthase: crystal structures of complexes of the enzyme from Sulfolobus solfataricus with substrate analogue, substrate, and product.

    Science.gov (United States)

    Hennig, Michael; Darimont, B D; Jansonius, J N; Kirschner, K

    2002-06-07

    Indoleglycerol phosphate synthase catalyzes the ring closure of an N-alkylated anthranilate to a 3-alkyl indole derivative, a reaction requiring Lewis acid catalysis in vitro. Here, we investigated the enzymatic reaction mechanism through X-ray crystallography of complexes of the hyperthermostable enzyme from Sulfolobus solfataricus with the substrate 1-(o-carboxyphenylamino) 1-deoxyribulose 5-phosphate, a substrate analogue and the product indole-3-glycerol phosphate. The substrate and the substrate analogue are bound to the active site in a similar, extended conformation between the previously identified phosphate binding site and a hydrophobic pocket for the anthranilate moiety. This binding mode is unproductive, because the carbon atoms that are to be joined are too far apart. The indole ring of the bound product resides in a second hydrophobic pocket adjacent to that of the anthranilate moiety of the substrate. Although the hydrophobic moiety of the substrate moves during catalysis from one hydrophobic pocket to the other, the triosephosphate moiety remains rigidly bound to the same set of hydrogen-bonding residues. Simultaneously, the catalytically important residues Lys53, Lys110 and Glu159 maintain favourable distances to the atoms of the ligand undergoing covalent changes. On the basis of these data, the structures of two putative catalytic intermediates were modelled into the active site. This new structural information and the modelling studies provide further insight into the mechanism of enzyme-catalyzed indole synthesis. The charged epsilon-amino group of Lys110 is the general acid, and the carboxylate group of Glu159 is the general base. Lys53 guides the substrate undergoing conformational transitions during catalysis, by forming a salt-bridge to the carboxylate group of its anthranilate moiety.

  15. Crystallization of proteinase K complexed with substrate analogue peptides on US space missions STS-91 and STS-95

    Science.gov (United States)

    Eschenburg, Susanne; Degenhardt, Michael; Moore, Karen; DeLucas, Lawrence J.; Peters, Klaus; Fittkau, Siegfried; Weber, Wolfgang; Betzel, Christian

    2000-01-01

    Crystals of proteinase K in complex with synthetic substrate analogues have been grown under microgravity on the US space shuttle missions STS-91 and STS-95 using the vapor diffusion apparatus (c-VDA) supplied by the Center for Macromolecular Crystallography at the University of Alabama at Birmingham. The crystals obtained under microgravity are compared with those grown simultanously on ground in identical c-VDA reactors and in conventional hanging-drop set-ups. The diffraction quality of space- and ground-grown crystals has been assessed by collecting complete data sets with a conventional X-ray source and with synchrotron radiation. Crystals grown in microgravity are clearly superior to those grown in the identical hardware on earth in terms of crystal habit and diffraction power. In comparison to best terrestrial crystals obtained in conventional hanging-drop set-ups the differences in crystal size and diffraction quality are less, but still confirm the benefit of microgravity for the crystallization of proteinase K-substrate analogue complexes.

  16. Glucose as substrate and signal in priming: Results from experiments with non-metabolizable glucose analogues

    Science.gov (United States)

    Mason-Jones, Kyle; Kuzyakov, Yakov

    2016-04-01

    Priming of soil organic matter remains the subject of intense research, but a mechanistic explanation of the phenomenon remains to be demonstrated. This is largely due to the multiple effects of easily available carbon on the soil microbial community, and the challenge of separating these influences from one another. Several glucose analogues can be taken up by microbial glucose transporters and have similar regulatory effects on metabolism. These substances are, however, not easily catabolized by the common glycolytic pathway, limiting their energy value. Therefore, they can be used to distinguish between the action of glucose as a metabolic signal, and its influence as an energy source. We incubated an agricultural Haplic Luvisol under controlled conditions for 24 days after addition of: 1) glucose, 2) 3-O-methyl-glucose, 3) α-methylglucoside or 4) 2-deoxyglucose, at three concentration levels, along with a control treatment of water addition. CO2 efflux from soil was monitored by trapping evolved CO2 in NaOH and back-titration with HCl. On the first day after amendment, CO2 efflux from soil increased strongly for glucose and much less for the analogues, relative to the control. Only glucose caused a peak in efflux within the first two days. Peak mineralization of 2-deoxyglucose and α-methylglucoside was delayed until the third day, while CO2 from 3-O-methyl-glucose increased gradually, with a peak delayed by approximately a week. For glucose, the immediate increase in respiration was strongly dependent on the amount of glucose added, but this was not the case for the analogues, indicating that the catabolic potential for these substances was saturated. This is consistent with only a small part of the microbial community being capable of utilizing these carbon sources. In a subsequent experiment, 14C-labelled glucose or 14C-labelled 3-O-methyl-glucose were added to the same soil, enabling quantification of the priming effect. For 3-O-methyl-glucose, priming was

  17. Bradykinin and its gly sup 6 analogue are substrates of cyclophilin: A fluorine-19 magnetization transfer study

    Energy Technology Data Exchange (ETDEWEB)

    London, R.E.; Davis, D.G. (NIEHS, NC (USA)); Vavrek, R.J.; Stewart, J.M. (Univ. of Colorado Health Sciences Center, Denver, CO (USA)); Handschumacher, R.E. (Yale Univ., New Haven, CT (USA))

    1990-11-01

    Fluorine-19 magnetization transfer experiments have been used to determine the rates of cis/trans isomerization about the X-Pro{sup 7} peptide bond in (p-fluoro-Phe{sup 8})bradykinin and its Gly{sup 6} analogue. The measurements were carried out both prior to and after the addition of cyclophilin, which has recently been shown to have peptidyl-proline cis/trans isomerase activity and is the apparent target enzyme of the immunosuppressive agent cyclosporin A. Magnetization transfer measurements over the temperature range 40-75 {degree}C in the absence of enzyme give activation energies of 22.8 and 23.0 kcal/mol for (p-fluoro-Phe{sup 8})bradykinin and its Gly{sup 6} analogue, respectively. The values for the uncatalyzed cis {r arrow} trans rate constant, k{sub c}, are determined by extrapolation to be 4.8 {times} 10{sup {minus}2} and 2.1 {times} 10{sup {minus}2} s{sup {minus}1} for the two peptides at 25 {degree}C. The enzyme-catalyzed enhancement of the cis/trans interconversion rate was proportional to added cyclophilin concentration and was strongly sequence specific, with bradykinin a much better substrate than (Gly{sup 6})bradykinin. At a peptide concentration of 2.2 mM, the catalytic activity expressed as k{sub c} per micromolar cyclophilin was determined to be 1.2 s{sup {minus}1}/{mu}M for (p-fluoro-Phe{sup 8})bradykinin and 0.13 s{sup {minus}1}/{mu}M for the Gly{sup 6}analogue. The increased cis {r arrow} trans interconversion rates were strongly inhibited by cyclosporin A and the 6-(methylalanine) derivative, which bind to cyclophilin, but not by the 1-(tetrahydrofurfuryl) derivative of cyclosporin that binds weakly.

  18. Probing the Catalytic Mechanism of S-Ribosylhomocysteinase (LuxS) with Catalytic Intermediates and Substrate Analogues

    Energy Technology Data Exchange (ETDEWEB)

    Gopishetty, Bhaskar; Zhu, Jinge; Rajan, Rakhi; Sobczak, Adam J.; Wnuk, Stanislaw F.; Bell, Charles E.; Pei, Dehua; (OSU); (FIU)

    2009-05-12

    S-Ribosylhomocysteinase (LuxS) cleaves the thioether bond in S-ribosylhomocysteine (SRH) to produce homocysteine (Hcys) and 4,5-dihydroxy-2,3-pentanedione (DPD), the precursor of the type II bacterial quorum sensing molecule (AI-2). The catalytic mechanism of LuxS comprises three distinct reaction steps. The first step involves carbonyl migration from the C1 carbon of ribose to C2 and the formation of a 2-ketone intermediate. The second step shifts the C=O group from the C2 to C3 position to produce a 3-ketone intermediate. In the final step, the 3-ketone intermediate undergoes a {beta}-elimination reaction resulting in the cleavage of the thioether bond. In this work, the 3-ketone intermediate was chemically synthesized and shown to be chemically and kinetically competent in the LuxS catalytic pathway. Substrate analogues halogenated at the C3 position of ribose were synthesized and reacted as time-dependent inhibitors of LuxS. The time dependence was caused by enzyme-catalyzed elimination of halide ions. Examination of the kinetics of halide release and decay of the 3-ketone intermediate catalyzed by wild-type and mutant LuxS enzymes revealed that Cys-84 is the general base responsible for proton abstraction in the three reaction steps, whereas Glu-57 likely facilitates substrate binding and proton transfer during catalysis.

  19. High Resolution Nuclear Magnetic Resonance Studies of the Active Site of Chymotrypsin. II. Polarization of Histidine 57 by Substrate Analogues and Competitive Inhibitors

    NARCIS (Netherlands)

    Robillard, G.; Shulman, R.G.

    1974-01-01

    The proton nuclear magnetic resonance signal of the His57-Asp102 hydrogen bonded proton in the charge relay system of chymotrypsinogen A and chymotrypsin Aδ has been monitored to determine the influence of substrate analogues and competitive inhibitors on the electronic state of the active site regi

  20. Patterning human neuronal networks on photolithographically engineered silicon dioxide substrates functionalized with glial analogues.

    Science.gov (United States)

    Hughes, Mark A; Brennan, Paul M; Bunting, Andrew S; Cameron, Katherine; Murray, Alan F; Shipston, Mike J

    2014-05-01

    Interfacing neurons with silicon semiconductors is a challenge being tackled through various bioengineering approaches. Such constructs inform our understanding of neuronal coding and learning and ultimately guide us toward creating intelligent neuroprostheses. A fundamental prerequisite is to dictate the spatial organization of neuronal cells. We sought to pattern neurons using photolithographically defined arrays of polymer parylene-C, activated with fetal calf serum. We used a purified human neuronal cell line [Lund human mesencephalic (LUHMES)] to establish whether neurons remain viable when isolated on-chip or whether they require a supporting cell substrate. When cultured in isolation, LUHMES neurons failed to pattern and did not show any morphological signs of differentiation. We therefore sought a cell type with which to prepattern parylene regions, hypothesizing that this cellular template would enable secondary neuronal adhesion and network formation. From a range of cell lines tested, human embryonal kidney (HEK) 293 cells patterned with highest accuracy. LUHMES neurons adhered to pre-established HEK 293 cell clusters and this coculture environment promoted morphological differentiation of neurons. Neurites extended between islands of adherent cell somata, creating an orthogonally arranged neuronal network. HEK 293 cells appear to fulfill a role analogous to glia, dictating cell adhesion, and generating an environment conducive to neuronal survival. We next replaced HEK 293 cells with slower growing glioma-derived precursors. These primary human cells patterned accurately on parylene and provided a similarly effective scaffold for neuronal adhesion. These findings advance the use of this microfabrication-compatible platform for neuronal patterning.

  1. Structural studies on the reaction of isopenicillin N synthase with the substrate analogue delta-(l-alpha-aminoadipoyl)-l-cysteinyl-d-alpha-aminobutyrate.

    Science.gov (United States)

    Long, Alexandra J; Clifton, Ian J; Roach, Peter L; Baldwin, Jack E; Schofield, Christopher J; Rutledge, Peter J

    2003-06-15

    Isopenicillin N synthase (IPNS) is a non-haem iron(II) oxidase which catalyses the biosynthesis of isopenicillin N from the tripeptide delta-(L-alpha-aminoadipoyl)-L-cysteinyl-D-valine (ACV). Herein we report crystallographic studies to investigate the reaction of IPNS with the truncated substrate analogue delta-(L-alpha-aminoadipoyl)-L-cysteinyl-D-alpha-aminobutyrate (ACAb). It has been reported previously that this analogue gives rise to three beta-lactam products when incubated with IPNS: two methyl penams and a cepham. Crystal structures of the IPNS-Fe(II)-ACAb and IPNS-Fe(II)-ACAb-NO complexes have now been solved and are reported herein. These structures and modelling studies based on them shed light on the diminished product selectivity shown by IPNS in its reaction with ACAb and further rationalize the presence of certain key residues at the IPNS active site.

  2. Effects of modified chromophores on the spectral sensitivity of salamander, squirrel and macaque cones.

    Science.gov (United States)

    Makino, C L; Kraft, T W; Mathies, R A; Lugtenburg, J; Miley, M E; van der Steen, R; Baylor, D A

    1990-05-01

    1. Chemically modified retinal chromophores were used to investigate the mechanisms that produce the characteristic spectral absorptions of cone pigments. Spectral sensitivities of single cones from the salamander, squirrel and macaque retina were determined by electrical recording. The chromophore was then replaced by bleaching the pigment and regenerating it with a retinal analogue. 2. Exposing a bleached cone to 9-cis-retinal for a brief period (less than 20 min) caused its flash sensitivity to recover to about 0.2 of the pre-bleach value. Similar exposure to a locked 6-s-cis, 9-cis analogue gave a recovery to about 0.03 of the pre-bleach value. 3. Unlike the flash sensitivity, the saturating photocurrent amplitude often recovered completely after bleaching and regenerating the pigment. 4. When the 3-dehydroretinal chromophore in the salamander long-wavelength-sensitive (red) cone was replaced with 11-cis-retinal, shortening the conjugated chain in the chromophore, the spectral sensitivity underwent a blue shift of 67 nm. 5. Pigments containing the planar-locked 6-s-cis.9-cis-retinal analogue absorbed at substantially longer wavelength than those containing unmodified 9-cis-retinal. The opsin shift, a measure of the protein's ability to modify the chromophore's absorption was larger for the locked analogue than for 9-cis-retinal. This suggests that the native chromophore assumes a twisted 6-s-cis conformation in these pigments. 6. The spectral sensitivities of red and green macaque cones containing 9-cis-retinal or planar-locked 6-s-cis.9-cis-retinal retained the 30 nm separation characteristic of the native pigments. This suggests that the different absorptions of of the 6-7 carbon bond in the retinal chromophore.

  3. Dissecting the chemical interactions and substrate structural signatures governing RNA polymerase II trigger loop closure by synthetic nucleic acid analogues

    DEFF Research Database (Denmark)

    Xu, Liang; Butler, Kyle Vincent; Chong, Jenny;

    2014-01-01

    The trigger loop (TL) of RNA polymerase II (Pol II) is a conserved structural motif that is crucial for Pol II catalytic activity and transcriptional fidelity. The TL remains in an inactive open conformation when the mismatched substrate is bound. In contrast, TL switches from an inactive open...... state to a closed active state to facilitate nucleotide addition upon the binding of the cognate substrate to the Pol II active site. However, a comprehensive understanding of the specific chemical interactions and substrate structural signatures that are essential to this TL conformational change...... II. This study reveals novel insights into understanding the molecular basis of TL conformational transition upon substrate binding during Pol II transcription. This synthetic chemical biology approach may be extended to understand the mechanisms of other RNA polymerases as well as other nucleic acid...

  4. Enzymatic synthesis of RNAs capped with nucleotide analogues reveals the molecular basis for substrate selectivity of RNA capping enzyme: impacts on RNA metabolism.

    Directory of Open Access Journals (Sweden)

    Moheshwarnath Issur

    Full Text Available RNA cap binding proteins have evolved to specifically bind to the N7-methyl guanosine cap structure found at the 5' ends of eukaryotic mRNAs. The specificity of RNA capping enzymes towards GTP for the synthesis of this structure is therefore crucial for mRNA metabolism. The fact that ribavirin triphosphate was described as a substrate of a viral RNA capping enzyme, raised the possibility that RNAs capped with nucleotide analogues could be generated in cellulo. Owing to the fact that this prospect potentially has wide pharmacological implications, we decided to investigate whether the active site of the model Paramecium bursaria Chlorella virus-1 RNA capping enzyme was flexible enough to accommodate various purine analogues. Using this approach, we identified several key structural determinants at each step of the RNA capping reaction and generated RNAs harboring various different cap analogues. Moreover, we monitored the binding affinity of these novel capped RNAs to the eIF4E protein and evaluated their translational properties in cellulo. Overall, this study establishes a molecular rationale for the specific selection of GTP over other NTPs by RNA capping enzyme It also demonstrates that RNAs can be enzymatically capped with certain purine nucleotide analogs, and it also describes the impacts of modified RNA caps on specific steps involved in mRNA metabolism. For instance, our results indicate that the N7-methyl group of the classical N7-methyl guanosine cap is not always indispensable for binding to eIF4E and subsequently for translation when compensatory modifications are present on the capped residue. Overall, these findings have important implications for our understanding of the molecular determinants involved in both RNA capping and RNA metabolism.

  5. Adsorption mechanism of physiologically active L-phenylalanine phosphonodipeptide analogues: Comparison of colloidal silver and macroscopic silver substrates

    Science.gov (United States)

    Podstawka, E.; Kudelski, A.; Proniewicz, L. M.

    2007-11-01

    Here we present SERS spectra of several L-phenylalanine (Phe) phosphonodipeptides, i.e., L-Phe- L-Ala-PO 3H 2 ( MD1), L-Phe- L-Va L-PO 3H 2 ( MD2), L-Phe-β-Ala-CH(OH)-PO 3H 2 ( MD3), L-Phe- L-Ala-CH(OH)-PO 3H 2 ( MD4), L-Ala-(3,4-dimethoxy)- L-Phe-PO 3H 2 ( MD5), and L-Ala-(3,4-dimethoxy)-(des-CH 2)- L-Phe-PO 3H 2 ( MD6), immobilized on electrochemically roughened silver electrodes. These spectra are analyzed by theoretical calculations using density functional theory (DFT) at the B3LYP level with 6-31++G∗∗ basis set. In addition, these spectra are compared with SERS spectra of these species adsorbed on a colloidal silver surface. We showed that on the macroscopic silver substrate, the Phe aromatic ring of MD3 and MD4 is oriented vertically, while for MD1 it almost "stands up" on this surface. In the other three cases, the Phe ring adopts a tilted orientation in regard to the substrate. We also find that the phosphonate (-PO32-), methyl/methane, or dimethoxy groups of MD1, MD2, MD3, MD5, and MD6 are involved in the interaction of these phosphonodipeptides with the electrochemically roughened surface. This phenomenon is clearly seen for -CH 2-/-CH 3/-OCH 3 moieties as well as for the PO32- group that adsorbs on the macroscopic silver substrates mainly via the P dbnd O fragment. We also showed that MD4 binds to the macroscopic silver substrate through the hydroxyl, amine, and phosphonate groups, while the methylene/methane moieties are remote from this surface. We found that studied phosphonodipeptides often adsorb differently on the macroscopic silver substrate and on the colloidal silver nanoparticles. For example, MD1 adopts an almost vertical orientation on the electrochemically roughened silver substrate and is tilted or close to flat on the silver nanoparticles.

  6. Insights into the substrate specificity of the MutT pyrophosphohydrolase using structural analogues of 8-oxo-2'-deoxyguanosine nucleotide.

    Science.gov (United States)

    Hamm, Michelle L; McFadden, Emily J; Ghio, Michael; Lindell, Maria A M; Gerien, Kenneth S; O'Handley, Suzanne F

    2016-04-15

    The bacterial repair enzyme MutT hydrolyzes the damaged nucleotide OdGTP (the 5'-triphosphate derivative of 8-oxo-2'-deoxyguanosine; OdG), which is a known mutagen and has been linked to antibacterial action. Previous work has indicated important roles for the C8-oxygen, N7-hydrogen, and C2-exocyclic amine during OdGTP recognition by MutT. In order to gain a more nuanced understanding of the contribution of these three sites to the overall activity of MutT, we determined the reaction parameters for dGTP, OdGTP, and nine of their analogues using steady state kinetics. Our results indicate that overall high reaction efficiencies can be achieved despite altering any one of these sites. However, altering two or more sites leads to a significant decrease in efficiency. The data also suggest that, similar to another bacterial OdG repair enzyme, MutM, a specific carbonyl in the enzyme can not only promote activity by forming an active site hydrogen bond with the N7-hydrogen of OdGTP, but can also hinder activity through electrostatic repulsion with the N7-lone pair of dGTP.

  7. Search for Singlet Fission Chromophores

    Energy Technology Data Exchange (ETDEWEB)

    Havlas, Z.; Akdag, A.; Smith, M. B.; Dron, P.; Johnson, J. C.; Nozik, A. J.; Michl, J.

    2012-01-01

    Singlet fission, in which a singlet excited chromophore shares its energy with a ground-state neighbor and both end up in their triplet states, is of potential interest for solar cells. Only a handful of compounds, mostly alternant hydrocarbons, are known to perform efficiently. In view of the large number of conditions that a successful candidate for a practical cell has to meet, it appears desirable to extend the present list of high performers to additional classes of compounds. We have (i) identified design rules for new singlet fission chromophores and for their coupling to covalent dimers, (ii) synthesized them, and (iii) evaluated their performance as neat solids or covalent dimers.

  8. Synthesis of Methylerythritol Phosphate Analogues and Their Evaluation as Alternate Substrates for IspDF and IspE from Agrobacterium tumefaciens

    Science.gov (United States)

    2015-01-01

    The methylerythritol phosphate biosynthetic pathway, found in most Bacteria, some parasitic protists, and plant chloroplasts, converts d-glyceraldehyde phosphate and pyruvate to isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP), where it intersects with the mevalonate pathway found in some Bacteria, Archaea, and Eukarya, including the cytosol of plants. d-3-Methylerythritol-4-phosphate (MEP), the first pathway-specific intermediate in the pathway, is converted to IPP and DMAPP by the consecutive action of the IspD-H proteins. We synthesized five d-MEP analogues—d-erythritol-4-phosphate (EP), d-3-methylthrietol-4-phosphate (MTP), d-3-ethylerythritol-4-phosphate (EEP), d-1-amino-3-methylerythritol-4-phosphate (NMEP), and d-3-methylerythritol-4-thiolophosphate (MESP)—and studied their ability to function as alternative substrates for the reactions catalyzed by the IspDF fusion and IspE proteins from Agrobacterium tumefaciens, which covert MEP to the corresponding eight-membered cyclic diphosphate. All of the analogues, except MTP, and their products were substrates for the three consecutive enzymes. PMID:25184438

  9. Phosphorylation substrates for protein kinase C in intact pituitary cells: characterization of a receptor-mediated event using novel gonadotropin-releasing hormone analogues

    Energy Technology Data Exchange (ETDEWEB)

    Strulovici, B.; Tahilramani, R.; Nestor, J.J. Jr.

    1987-09-22

    The involvement of protein kinase C in the signal transduction of gonadotropin-releasing hormone (GnRH) action was investigated with a GnRH superagonist, partial agonists, and antagonists in intact rat pituitary cells. Exposure of /sup 32/P-labeled cells to GnRH or to the superagonist (D-Nal(2)/sup 6/)GnRH induced the enhanced phosphorylation of 42-, 34-, 11-, and 10-kDa proteins and the dephosphorylation of a 15-kDa protein as assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis/autoradiography. This effect was blocked in a dose-dependent manner by potent GnRG antagonists. Downregulation of protein kinase C by prolonged incubation of the pituitary cells with high concentrations of active phorbol esters abolished protein kinase C activity and also prevented the phosphorylation induced by GnRN, or (D-Nal(2)/sup 6/)GnRH. The same effect was obtained by preincubating the cells with the protein kinase C inhibitor H-7. In this study the authors identify for the first time physiological substrates for protein kinase C in intact pituitary cells. They demonstrate a close quantitative correlation between the extent of translocation of protein kinase C, levels of phosphorylation of specific substrates in the intact cells, and the biological activity of the GnRH analogues with varying affinity for the GnRH receptor. These data strengthen the contention that the physiological effects of GnRH are primarily mediated via the phosphatidylinositol/Ca/sup 2 +/ signal transfer system and represent a first step toward defining the physiological substrates of protein kinase C and their role in the cascade of events that starts upon binding of GnRH to its receptor.

  10. A microenvironment-sensitive fluorescent pyrimidine ribonucleoside analogue: synthesis, enzymatic incorporation, and fluorescence detection of a DNA abasic site.

    Science.gov (United States)

    Tanpure, Arun A; Srivatsan, Seergazhi G

    2011-11-04

    Base-modified fluorescent ribonucleoside-analogue probes are valuable tools in monitoring RNA structure and function because they closely resemble the structure of natural nucleobases. Especially, 2-aminopurine, a highly environment-sensitive adenosine analogue, is the most extensively utilized fluorescent nucleoside analogue. However, only a few isosteric pyrimidine ribonucleoside analogues that are suitable for probing the structure and recognition properties of RNA molecules are available. Herein, we describe the synthesis and photophysical characterization of a small series of base-modified pyrimidine ribonucleoside analogues derived from tagging indole, N-methylindole, and benzofuran onto the 5-position of uracil. One of the analogues, based on a 5-(benzofuran-2-yl)pyrimidine core, shows emission in the visible region with a reasonable quantum yield and, importantly, displays excellent solvatochromism. The corresponding triphosphate substrate is effectively incorporated into oligoribonucleotides by T7 RNA polymerase to produce fluorescent oligoribonucleotide constructs. Steady-state and time-resolved spectroscopic studies with fluorescent oligoribonucleotide constructs demonstrate that the fluorescent ribonucleoside photophysically responds to subtle changes in its environment brought about by the interaction of the chromophore with neighboring bases. In particular, the emissive ribonucleoside, if incorporated into an oligoribonucleotide, positively reports the presence of a DNA abasic site with an appreciable enhancement in fluorescence intensity. The straightforward synthesis, amicability to enzymatic incorporation, and sensitivity to changes in the microenvironment highlight the potential of the benzofuran-conjugated pyrimidine ribonucleoside as an efficient fluorescent probe to investigate nucleic acid structure, dynamics, and recognition events.

  11. Relation between the catalytic efficiency of the synthetic analogues of catechol oxidase with their electrochemical property in the free state and substrate-bound state.

    Science.gov (United States)

    Chakraborty, Prateeti; Adhikary, Jaydeep; Ghosh, Bipinbihari; Sanyal, Ria; Chattopadhyay, Shyamal Kumar; Bauzá, Antonio; Frontera, Antonio; Zangrando, Ennio; Das, Debasis

    2014-08-18

    A library of 15 dicopper complexes as synthetic analogues of catechol oxidase has been synthesized with the aim to determine the relationship between the electrochemical behavior of the dicopper(II) species in the absence as well as in the presence of 3,5-di-tert-butylcatechol (3,5-DTBC) as model substrate and the catalytic activity, kcat, in DMSO medium. The complexes have been characterized by routine physicochemical techniques as well as by X-ray single-crystal structure analysis in some cases. Fifteen "end-off" compartmental ligands have been designed as 1 + 2 Schiff-base condensation product of 2,6-diformyl-4-R-phenol (R = Me, (t)Bu, and Cl) and five different amines, N-(2-aminoethyl)piperazine, N-(2-aminoethyl)pyrrolidine, N-(2-aminoethyl)morpholine, N-(3-aminopropyl)morpholine, and N-(2-aminoethyl)piperidine. Interestingly, in case of the combination of 2,6-diformyl-4-methylphenol and N-(2-aminoethyl)morpholine/N-(3-aminopropyl)morpholine/N-(2-aminoethyl)piperidine 1 + 1 condensation becomes the reality and the ligands are denoted as L2(1-3). On reaction of copper(II) nitrate with L2(1-3) in situ complexes 3, 12, and 13 are formed having general formula Cu2(L2(1-3))2(NO3)2. The remaining 12 ligands obtained as 1 + 2 condensation products are denoted as L1(1-12), which produce complexes having general formula Cu2(L1(1-12))(NO3)2. Catecholase activity of all 15 complexes has been investigated in DMSO medium using 3,5-DTBC as model substrate. Treatment on the basis of Michaelis-Menten model has been applied for kinetic study, and thereby turnover number, kcat, values have been evaluated. Cyclic voltametric (CV) and differential pulse voltametric (DPV) studies of the complexes in the presence as well as in the absence of 3,5-DTBC have been thoroughly investigated in DMSO medium. From those studies it is evident that oxidation of 3,5-DTBC catalyzed by dicopper(II) complexes proceed via two steps: first, semibenzoquinone followed by benzoquinone with concomitant

  12. Biliprotein maturation: the chromophore attachment.

    Science.gov (United States)

    Scheer, H; Zhao, K-H

    2008-04-01

    Biliproteins are a widespread group of brilliantly coloured photoreceptors characterized by linear tetrapyrrolic chromophores, bilins, which are covalently bound to the apoproteins via relatively stable thioether bonds. Covalent binding stabilizes the chromoproteins and is mandatory for phycobilisome assembly; and, it is also important in biliprotein applications such as fluorescence labelling. Covalent binding has, on the other hand, also considerably hindered biliprotein research because autocatalytic chromophore additions are rare, and information on enzymatic addition by lyases was limited to a single example, an EF-type lyase attaching phycocyanobilin to cysteine-alpha84 of C-phycocyanin. The discovery of new activities for the latter lyases, and of new types of lyases, have reinvigorated research activities in the subject. So far, work has mainly concentrated on cyanobacterial phycobiliproteins. Methodological advances in the process, however, as well as the finding of often large numbers of homologues, opens new possibilities for research on the subsequent assembly/disassembly of the phycobilisome in cyanobacteria and red algae, on the assembly and organization of the cryptophyte light-harvesting system, on applications in basic research such as protein folding, and on the use of phycobiliproteins for labelling.

  13. Towards a wearable near infrared spectroscopic probe for monitoring concentrations of multiple chromophores in biological tissue in vivo

    Science.gov (United States)

    Chitnis, Danial; Airantzis, Dimitrios; Highton, David; Williams, Rhys; Phan, Phong; Giagka, Vasiliki; Powell, Samuel; Cooper, Robert J.; Tachtsidis, Ilias; Smith, Martin; Elwell, Clare E.; Hebden, Jeremy C.; Everdell, Nicholas

    2016-06-01

    The first wearable multi-wavelength technology for functional near-infrared spectroscopy has been developed, based on a custom-built 8-wavelength light emitting diode (LED) source. A lightweight fibreless probe is designed to monitor changes in the concentrations of multiple absorbers (chromophores) in biological tissue, the most dominant of which at near-infrared wavelengths are oxyhemoglobin and deoxyhemoglobin. The use of multiple wavelengths enables signals due to the less dominant chromophores to be more easily distinguished from those due to hemoglobin and thus provides more complete and accurate information about tissue oxygenation, hemodynamics, and metabolism. The spectroscopic probe employs four photodiode detectors coupled to a four-channel charge-to-digital converter which includes a charge integration amplifier and an analogue-to-digital converter (ADC). Use of two parallel charge integrators per detector enables one to accumulate charge while the other is being read out by the ADC, thus facilitating continuous operation without dead time. The detector system has a dynamic range of about 80 dB. The customized source consists of eight LED dies attached to a 2 mm × 2 mm substrate and encapsulated in UV-cured epoxy resin. Switching between dies is performed every 20 ms, synchronized to the detector integration period to within 100 ns. The spectroscopic probe has been designed to be fully compatible with simultaneous electroencephalography measurements. Results are presented from measurements on a phantom and a functional brain activation study on an adult volunteer, and the performance of the spectroscopic probe is shown to be very similar to that of a benchtop broadband spectroscopy system. The multi-wavelength capabilities and portability of this spectroscopic probe will create significant opportunities for in vivo studies in a range of clinical and life science applications.

  14. Synthesis and Nonlinear Optical Property of a Series of New Chromophores Containing Furan Ring as the Only Conjugation Bridge

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    This paper reports the synthesis and the nonlinear optical property of a series of new chromophores which contain furan ring as the only conjugation bridge for the first time. They are characterized by UV-VIS, FT-IR, 1H NMR, MS and elemental analysis. Their dipole moment and the first-order molecular hyperpolarizability (β) are calculated and compared with those of the analogues containing either benzene or thiophene as the conjugation bridge.

  15. Initial-rate kinetics of human NMN-adenylyltransferases: substrate and metal ion specificity, inhibition by products and multisubstrate analogues, and isozyme contributions to NAD+ biosynthesis.

    Science.gov (United States)

    Sorci, Leonardo; Cimadamore, Flavio; Scotti, Stefania; Petrelli, Riccardo; Cappellacci, Loredana; Franchetti, Palmarisa; Orsomando, Giuseppe; Magni, Giulio

    2007-04-24

    Initial-rate and product inhibition studies revealed distinctive ordered ternary complex kinetic mechanisms, substrate specificities, and metal ion preferences for the three isozymes of human nicotinamide mononucleotide adenylyl-transferase (NMNAT, EC 2.7.7.1). ATP binds before NMN with nuclear isozyme NMNAT1 and Golgi apparatus NMNAT2, but the opposite order is observed with the mitochondrial isozyme NMNAT3. Only the latter utilizes ITP efficiently in place of ATP, and while NMNH conversion to NADH by NMNAT1 and NMNAT3 occurs at similar rates, conversion by NMNAT2 is much slower. These isozymes can also be discriminated by their action on tiazofurin monophosphate (TrMP), a metabolite of the antineoplastic prodrug tiazofurin. Our finding that TrMP is only a substrate with NMNAT1 and NMNAT3 reveals for the first time an organelle selectivity in the metabolism of this important drug. In search of additional ways to discriminate these isozymes, we synthesized and tested the P1-(nicotinamide/nicotinate-riboside-5')-Pn-(adenosine-5') dinucleotides Np3AD, Np4AD, and Nap4AD. In addition to being highly effective inhibitors, these multisubstrate geometric inhibitors gave inhibition patterns that are consistent with the aforementioned isozyme differences in substrate binding order. Distinctive differences in their substrate specificity and metal ion selectivity also permitted us to quantify individual isozyme contributions to NAD+ formation in human cell extracts.

  16. Molecular Selectivity of Brown Carbon Chromophores

    Energy Technology Data Exchange (ETDEWEB)

    Laskin, Julia; Laskin, Alexander; Nizkorodov, Sergey; Roach, Patrick J.; Eckert, Peter A.; Gilles, Mary K.; Wang, Bingbing; Lee, Hyun Ji; Hu, Qichi

    2014-10-21

    Complementary methods of high-resolution mass spectrometry and micro-spectroscopy were utilized for molecular analysis of secondary organic aerosol (SOA) generated from ozonolysis of two structural monoterpene isomers: D-limonene (LSOA) and a-pinene (PSOA). Laboratory simulated aging of LSOA and PSOA, through conversion of carbonyls into imines mediated by NH3 vapors in humid air, resulted in selective browning of the LSOA sample, while the PSOA sample remained white. Comparative analysis of the reaction products in the aged LSOA and PSOA samples provided insights into chemistry relevant to formation of brown carbon chromophores. A significant fraction of carbonyl-imine conversion products with identical molecular formulas were detected in both samples. This reflects the high level of similarity in the molecular composition of these two closely related SOA materials. Several highly conjugated products were detected exclusively in the brown LSOA sample and were identified as potential chromophores responsible for the observed color change. The majority of the unique products in the aged LSOA sample with the highest number of double bonds contain two nitrogen atoms. We conclude that chromophores characteristic of the carbonyl- imine chemistry in LSOA are highly conjugated oligomers of secondary imines (Schiff bases) present at relatively low concentrations. Formation of this type of conjugated compounds in PSOA is hindered by the structural rigidity of the a-pinene oxidation products. Our results suggest that the overall light-absorbing properties of SOA may be determined by trace amounts of strong brown carbon chromophores.

  17. Platinum Acetylide Two-Photon Chromophores (Postprint)

    Science.gov (United States)

    2007-01-01

    advantageous for two reasons. First, by using lower-energy photons, a material will be protected from photodegradation effects. Second, the quadratic...absorbing dyes .19,20,33-39 We show the chromophores depicted in Figure 1 exhibit a remarkable increase in the 2PA cross-section (σ2) over PE2 mentioned

  18. A Possibly Universal Red Chromophore for Jupiter

    Science.gov (United States)

    Sromovsky, Lawrence A.; Baines, Kevin; Fry, Patrick M.

    2016-10-01

    A new laboratory-generated chemical compound made from photodissociated ammonia (NH3) molecules reacting with acetylene (C2H2) was suggested as a possible coloring agent for Jupiter's Great Red Spot (GRS) by Carlson et al. (2016, Icarus 274, 106-115). Baines et al. (2016, AAS/DPS Meeting abstract) showed that the GRS spectrum measured by the visual channels of the Cassini VIMS instrument in 2000 could be accurately fit by a cloud model in which the chromophore appeared as small particles in a physically thin layer immediately above the main cloud layer of the GRS. Here we show that the same chromophore and similar layer structure can also provide close matches to the 0.4-1 micron spectra of many other cloud features on Jupiter, suggesting that this material may be a nearly universal chromophore responsible for the various degrees of red coloration on Jupiter. This is a robust conclusion, even for 12 percent changes in VIMS calibration and large uncertainties in the refractive index of the main cloud layer due to uncertain fractions of NH4SH and NH3 in its cloud particles. The chromophore layer can account for color variations among north and south equatorial belts, equatorial zone, and the Great Red Spot, by varying particle size from 0.12 to 0.29 micron and optical depth from 0.06 to 0.76. The total mass of the chromophore layer is much less variable than its optical depth, staying mainly within 6-10 micrograms/cm2 range, but is only about half that amount in the equatorial zone. We also found a depression of the ammonia volume mixing ratio in the two belt regions, which averaged 0.4-0.5 × 10-4 immediately below the ammonia condensation level, while the other regions averaged twice that value.LAS and PMF acknowledge support from NASA Grant NNX14AH40G.

  19. Modern analogues for Miocene to Pleistocene alkali basaltic phreatomagmatic fields in the Pannonian Basin: "soft-substrate" to "combined" aquifer controlled phreatomagmatism in intraplate volcanic fields Research Article

    Science.gov (United States)

    Németh, Károly; Cronin, Shane; Haller, Miguel; Brenna, Marco; Csillag, Gabor

    2010-09-01

    The Pannonian Basin (Central Europe) hosts numerous alkali basaltic volcanic fields in an area similar to 200 000 km2. These volcanic fields were formed in an approximate time span of 8 million years producing smallvolume volcanoes typically considered to be monogenetic. Polycyclic monogenetic volcanic complexes are also common in each field however. The original morphology of volcanic landforms, especially phreatomagmatic volcanoes, is commonly modified. by erosion, commonly aided by tectonic uplift. The phreatomagmatic volcanoes eroded to the level of their sub-surface architecture expose crater to conduit filling as well as diatreme facies of pyroclastic rock assemblages. Uncertainties due to the strong erosion influenced by tectonic uplifts, fast and broad climatic changes, vegetation cover variations, and rapidly changing fluvio-lacustrine events in the past 8 million years in the Pannonian Basin have created a need to reconstruct and visualise the paleoenvironment into which the monogenetic volcanoes erupted. Here phreatomagmatic volcanic fields of the Miocene to Pleistocene western Hungarian alkali basaltic province have been selected and compared with modern phreatomagmatic fields. It has been concluded that the Auckland Volcanic Field (AVF) in New Zealand could be viewed as a prime modern analogue for the western Hungarian phreatomagmatic fields by sharing similarities in their pyroclastic successions textures such as pyroclast morphology, type, juvenile particle ratio to accidental lithics. Beside the AVF two other, morphologically more modified volcanic fields (Pali Aike, Argentina and Jeju, Korea) show similar features to the western Hungarian examples, highlighting issues such as preservation potential of pyroclastic successions of phreatomagmatic volcanoes.

  20. Synthesis of screening substrates for the directed evolution of sialic acid aldolase: towards tailored enzymes for the preparation of influenza A sialidase inhibitor analogues.

    Science.gov (United States)

    Woodhall, Thomas; Williams, Gavin; Berry, Alan; Nelson, Adam

    2005-05-01

    The stereoselective synthesis of two epimeric screening substrates, (4R, 5R, 6R)- and (4S, 5R, 6R)-6-dipropylcarbamoyl-2-oxo-4,5,6-trihydroxy-hexanoic acid, for the directed evolution of sialic acid aldolase is described. The complementary methods relied on stereoselective indium-mediated additions of ethyl alpha-bromomethyl acrylate to functionalised aldehydes. With an alpha-hydroxy aldehyde, (2R, 3R)-2,3-dihydroxy-4-oxo butanoic acid dipropylamide, the addition was chelation controlled, and the syn product, (6R, 5R, 4S)-6-dipropylcarbamoyl-2-methylidene-4,5,6-trihydroxy-hexanoic acid ethyl ester, was obtained. In contrast, the stereochemical outcome of the addition to (2R, 3R)-N,N-dipropyl-2,3-O-isopropylidene-4-oxobutyramide was consistent with Felkin-Anh control, and the anti adduct, (4R, 5R, 6R)-6-dipropylcarbamoyl-2-methylidene-4-hydroxy-5,6-O-isopropylidene-hexanoic acid ethyl ester, was the major product. Ozonolysis and deprotection gave the screening substrates as mixtures of furanose and pyranose forms, in good yields.

  1. Sulfur analogues of psychotomimetic agents. Monothio analogues of mescaline and isomescaline.

    Science.gov (United States)

    Jacob, P; Shulgin, A T

    1981-11-01

    Two monothio analogues of mescaline and three monothio analogues of 2,3,4-trimethoxyphenethylamine (isomescaline) have been synthesized and characterized. Only the two mescaline analogues (3-and 4-thiomescaline) were found to be psychotomimetics in man, being 6 and 12 times more potent than mescaline, respectively. All five compounds can serve as substrates for bovine plasma monoamine oxidase in vitro, but no positive correlation is apparent between the extent of enzymatic degradation and human psychotomimetic potency.

  2. Molecular selectivity of brown carbon chromophores.

    Science.gov (United States)

    Laskin, Julia; Laskin, Alexander; Nizkorodov, Sergey A; Roach, Patrick; Eckert, Peter; Gilles, Mary K; Wang, Bingbing; Lee, Hyun Ji Julie; Hu, Qichi

    2014-10-21

    Complementary methods of high-resolution mass spectrometry and microspectroscopy were utilized for molecular analysis of secondary organic aerosol (SOA) generated from ozonolysis of two structural monoterpene isomers: D-limonene SOA (LSOA) and α-pinene SOA (PSOA). The LSOA compounds readily formed adducts with Na(+) under electrospray ionization conditions, with only a small fraction of compounds detected in the protonated form. In contrast, a significant fraction of PSOA compounds appeared in the protonated form because of their increased molecular rigidity. Laboratory simulated aging of LSOA and PSOA, through conversion of carbonyls into imines mediated by NH3 vapors in humid air, resulted in selective browning of the LSOA sample, while the PSOA sample remained white. Comparative analysis of the reaction products in the aged LSOA and PSOA samples provided insights into chemistry relevant to formation of brown carbon chromophores. A significant fraction of carbonyl-imine conversion products with identical molecular formulas was detected in both samples. This reflects the high level of similarity in the molecular composition of these two closely related SOA materials. Several highly conjugated products were detected exclusively in the brown LSOA sample and were identified as potential chromophores responsible for the observed color change. The majority of the unique products in the aged LSOA sample with the highest number of double bonds contain two nitrogen atoms. We conclude that chromophores characteristic of the carbonyl-imine chemistry in LSOA are highly conjugated oligomers of secondary imines (Schiff bases) present at relatively low concentrations. Formation of this type of conjugated compounds in PSOA is hindered by the structural rigidity of the α-pinene oxidation products. Our results suggest that the overall light-absorbing properties of SOA may be determined by trace amounts of strong brown carbon chromophores.

  3. Analogues of uracil nucleosides with intrinsic fluorescence (NIF-analogues): synthesis and photophysical properties.

    Science.gov (United States)

    Segal, Meirav; Fischer, Bilha

    2012-02-28

    Uridine cannot be utilized as fluorescent probe due to its extremely low quantum yield. For improving the uracil fluorescence characteristics we extended the natural chromophore at the C5 position by coupling substituted aromatic rings directly or via an alkenyl or alkynyl linker to create fluorophores. Extension of the uracil base was achieved by treating 5-I-uridine with the appropriate boronic acid under the Suzuki coupling conditions. Analogues containing an alkynyl linker were obtained from 5-I-uridine and the suitable boronic acid in a Sonogashira coupling reaction. The uracil fluorescent analogues proposed here were designed to satisfy the following requirements: a minimal chemical modification at a position not involved in base-pairing, resulting in relatively long absorption and emission wavelengths and high quantum yield. 5-((4-Methoxy-phenyl)-trans-vinyl)-2'-deoxy-uridine, 6b, was found to be a promising fluorescent probe. Probe 6b exhibits a quantum yield that is 3000-fold larger than that of the natural chromophore (Φ 0.12), maximum emission (478 nm) which is 170 nm red shifted as compared to uridine, and a Stokes shift of 143 nm. In addition, since probe 6b adopts the anti conformation and S sugar puckering favored by B-DNA, it makes a promising nucleoside analogue to be incorporated in an oligonucleotide probe for detection of genetic material.

  4. Effect of chromophore-chromophore electrostatic interactions in the NLO response of functionalized organic-inorganic sol-gel materials

    Science.gov (United States)

    Reyes-Esqueda, J.; Darracq, B.; García-Macedo, J.; Canva, M.; Blanchard-Desce, M.; Chaput, F.; Lahlil, K.; Boilot, J. P.; Brun, A.; Lévy, Y.

    2001-10-01

    In the last years, important non-linear optical (NLO) results on sol-gel and polymeric materials have been reported, with values comparable to those found in crystals. These new materials contain push-pull chromophores either incorporated as guest in a high Tg polymeric matrix (doped polymers) or grafted onto the polymeric matrix. These systems present several advantages, however they require significant improvement at the molecular level—by designing optimized chromophores with very large molecular figure of merit, specific to each application targeted. Besides, it was recently stated in polymers that the chromophore-chromophore electrostatic interactions, which are dependent of chromophore concentration, have a strong effect into their NLO properties. This has not been explored at all in sol-gel systems. In this work, the sol-gel route was used to prepare hybrid organic-inorganic thin films with different NLO chromophores grafted into the skeleton matrix. Combining a molecular engineering strategy for getting a larger molecular figure of merit and by controlling the intermolecular dipole-dipole interactions through both: the tuning of the push-pull chromophore concentration and the control of tetraethoxysilane concentration, we have obtained a r33 coefficient around 15 pm/V at 633 nm for the classical DR1 azo-chromophore and a r33 around 50 pm/V at 831 nm for a new optimized chromophore structure.

  5. Active site directed irreversible inactivation of brewers' yeast pyruvate decarboxylase by the conjugated substrate analogue (E)-4-(4-chlorophenyl)-2-oxo-3-butenoic acid: development of a suicide substrate.

    Science.gov (United States)

    Kuo, D J; Jordan, F

    1983-08-01

    (E)-4-(4-Chlorophenyl)-2-oxo-3-butenoic acid (CPB) was found to irreversibly inactivate brewers' yeast pyruvate decarboxylase (PDC, EC 4.1.1.1) in a biphasic, sigmoidal manner, as is found for the kinetic behavior of substrate. An expression was derived for two-site irreversible inhibition of allosteric enzymes, and the kinetic behavior of CPB fit the expression for two-site binding. The calculated Ki's of 0.7 mM and 0.3 mM for CPB were assigned to the catalytic site and the regulatory site, respectively. The presence of pyruvic acid at high concentrations protected PDC from inactivation, whereas low concentrations of pyruvic acid accelerated inactivation by CPB. Pyruvamide, a known allosteric activator of PDC, was found to enhance inactivation by CPB. The results can be explained if pyruvamide binds only to a regulatory site, but CPB and pyruvic acid compete for both the regulatory and the catalytic centers. [1-14C]CPB was found to lose 14CO2 concurrently with the inactivation of the enzyme. Therefore, CPB was being turned over by PDC, in addition to inactivating it. CPB can be labeled a suicide-type inactivator for PDC.

  6. Analogue computing methods

    CERN Document Server

    Welbourne, D

    1965-01-01

    Analogue Computing Methods presents the field of analogue computation and simulation in a compact and convenient form, providing an outline of models and analogues that have been produced to solve physical problems for the engineer and how to use and program the electronic analogue computer. This book consists of six chapters. The first chapter provides an introduction to analogue computation and discusses certain mathematical techniques. The electronic equipment of an analogue computer is covered in Chapter 2, while its use to solve simple problems, including the method of scaling is elaborat

  7. Development of bacteriorhodopsin analogues and studies of charge separated excited states in the photoprocesses of linear polyenes.

    Science.gov (United States)

    Singh, Anil K; Hota, Prasanta K

    2007-01-01

    Development of bacteriorhodopsin (bR) analogues employing chromophore substitution technique for the purpose of characterizing the binding site of bR and generating bR analogues with novel opto-electronic properties for applications as photoactive element in nanotechnical devices are described. Additionally, the photophysical and photochemical properties of variously substituted diarylpolyenes as models of photobiologically relevant linear polyenes are discussed. The role of charge separated dipolar excited states in the photoprocesses of linear polyenes is highlighted.

  8. Investigation into chromophore excited-state coupling in allophycocyanin

    Science.gov (United States)

    Zheng, Xiguang; Zhao, Fuli; Wang, He Z.; Gao, Zhaolan; Yu, Zhenxin; Zhu, Jinchang; Xia, Andong; Jiang, Lijin

    1994-08-01

    Both theoretical and experimental studies are presented on chromophore excited-state coupling in linker-free allophycocyanin (APC), one of the antenna phycobiliproteins in algal photosynthesis. A three-site-coupling model has been introduced to describe the exciton interaction mechanism amoung the excited (beta) chromophore in APC, and the exciton energy splitting is estimated. Picosecond polarized fluorescence experiments both on monomeric and trimeric APC isolated from alga Spirulina platensis have been performed. The experimental results show that APC monomer and trimer exhibit remarkedly different spectropic characteristics, and satisfy the suggestion of strong excited- state coupling among chromophores in APC.

  9. Chromophore design for large two-photon absorption

    Science.gov (United States)

    Dudley, Christopher

    2014-11-01

    Conjugated oligothiophene chromophores are compared and studied for designing large linear and nonlinear absorption cross-sections. Optical properties of chromophores synthesized by the Naval Research Laboratory are modeled to construct a design factor of merit to predict and understand two-photon absorption (TPA) designs. Computer modeling to optimize parameters to produce photo active chromophores is conducted. Geometry, π-center (electron relay) and the electron donor or acceptor groups attached to the π-centers are considered for importance in TPA. This work could serve equally well as guide for quick back of the envelop research or industrial design verifications as well as an outline for introducing computation methods to students.

  10. Analogue MIMO Detection

    Directory of Open Access Journals (Sweden)

    McNamara Darren

    2006-01-01

    Full Text Available In this contribution we propose an analogue receiver that can perform turbo detection in MIMO systems. We present the case for a receiver that is built from nonlinear analogue devices, which perform detection in a "free-flow" network (no notion of iterations. This contribution can be viewed as an extension of analogue turbo decoder concepts to include MIMO detection. These first analogue implementations report reductions of few orders of magnitude in the number of required transistors and in consumed energy, and the same order of improvement in processing speed. It is anticipated that such analogue MIMO decoder could bring about the same advantages, when compared to traditional digital implementations.

  11. Unraveling the chromophoric disorder of poly(3-hexylthiophene)

    CERN Document Server

    Thiessen, Alexander; Adachi, Takuji; Steiner, Florian; Bout, David Vanden; Lupton, John M

    2015-01-01

    The spectral breadth of conjugated polymers gives these materials a clear advantage over other molecular compounds for organic photovoltaic applications and is a key factor in recent efficiencies topping 10%. But why do excitonic transitions, which are inherently narrow, lead to absorption over such a broad range of wavelengths in the first place? Using single-molecule spectroscopy, we address this fundamental question in a model material, poly(3-hexylthiophene). Narrow zero-phonon lines from single chromophores are found to scatter over 200nm, an unprecedented inhomogeneous broadening which maps the ensemble. The giant red-shift between solution and bulk films arises from energy transfer to the lowest-energy chromophores in collapsed polymer chains which adopt a highly-ordered morphology. We propose that the extreme energetic disorder of chromophores is structural in origin. This structural disorder on the single-chromophore level may actually enable the high degree of polymer chain ordering found in bulk fi...

  12. Highly fluorescent benzofuran derivatives of the GFP chromophore

    DEFF Research Database (Denmark)

    Christensen, Mikkel Andreas; Jennum, Karsten Stein; Abrahamsen, Peter Bæch;

    2012-01-01

    Intramolecular cyclization reactions of Green Fluorescent Protein chromophores (GFPc) containing an arylethynyl ortho-substituent at the phenol ring provide new aryl-substituted benzofuran derivatives of the GFPc. Some of these heteroaromatic compounds exhibit significantly enhanced fluorescence ...

  13. Relating Chromophoric and Structural Disorder in Conjugated Polymers

    CERN Document Server

    Simine, Lena

    2016-01-01

    The optoelectronic properties of amorphous conjugated polymers are sensitive to conformational disorder and spectroscopy provides the means for structural characterization of the fragments of the chain which interact with light - "chromophores". A faithful interpretation of spectroscopic conformational signatures, however, presents a key challenge. We investigate the relationship between the ground state optical gaps, the properties of the excited states, and the structural features of chromophores of a single molecule poly(3-hexyl)-thiophene (P3HT), using quantum-classical atomistic simulations. Our results demonstrate that chromophoric disorder reflects an interplay between excited state de-localization and electron-hole polarization, and is controlled by torsional disorder that is specifically associated with the presence of side chains. Within this conceptual framework, we predict and explain a counter-intuitive spectral signature of P3HT: a red-shifted absorption, despite shortening of chromophores, with...

  14. Fluorescence of Phytochrome Adducts with Synthetic Locked Chromophores*

    OpenAIRE

    Zienicke, Benjamin; Chen, Li-Yi; Khawn, Htoi; Hammam, Mostafa A. S.; Kinoshita, Hideki; Reichert, Johannes; Ulrich, Anne S.; Inomata, Katsuhiko; Lamparter, Tilman

    2010-01-01

    We performed steady state fluorescence measurements with phytochromes Agp1 and Agp2 of Agrobacterium tumefaciens and three mutants in which photoconversion is inhibited. These proteins were assembled with the natural chromophore biliverdin (BV), with phycoerythrobilin (PEB), which lacks a double bond in the ring C-D-connecting methine bridge, and with synthetic bilin derivatives in which the ring C-D-connecting methine bridge is locked. All PEB and locked chromophore adducts are photoinactive...

  15. Fluorescence of Phytochrome Adducts with Synthetic Locked Chromophores*

    Science.gov (United States)

    Zienicke, Benjamin; Chen, Li-Yi; Khawn, Htoi; Hammam, Mostafa A. S.; Kinoshita, Hideki; Reichert, Johannes; Ulrich, Anne S.; Inomata, Katsuhiko; Lamparter, Tilman

    2011-01-01

    We performed steady state fluorescence measurements with phytochromes Agp1 and Agp2 of Agrobacterium tumefaciens and three mutants in which photoconversion is inhibited. These proteins were assembled with the natural chromophore biliverdin (BV), with phycoerythrobilin (PEB), which lacks a double bond in the ring C-D-connecting methine bridge, and with synthetic bilin derivatives in which the ring C-D-connecting methine bridge is locked. All PEB and locked chromophore adducts are photoinactive. According to fluorescence quantum yields, the adducts may be divided into four different groups: wild type BV adducts exhibiting a weak fluorescence, mutant BV adducts with about 10-fold enhanced fluorescence, adducts with locked chromophores in which the fluorescence quantum yields are around 0.02, and PEB adducts with a high quantum yield of around 0.5. Thus, the strong fluorescence of the PEB adducts is not reached by the locked chromophore adducts, although the photoconversion energy dissipation pathway is blocked. We therefore suggest that ring D of the bilin chromophore, which contributes to the extended π-electron system of the locked chromophores, provides an energy dissipation pathway that is independent on photoconversion. PMID:21071442

  16. Fluorescence of phytochrome adducts with synthetic locked chromophores.

    Science.gov (United States)

    Zienicke, Benjamin; Chen, Li-Yi; Khawn, Htoi; Hammam, Mostafa A S; Kinoshita, Hideki; Reichert, Johannes; Ulrich, Anne S; Inomata, Katsuhiko; Lamparter, Tilman

    2011-01-14

    We performed steady state fluorescence measurements with phytochromes Agp1 and Agp2 of Agrobacterium tumefaciens and three mutants in which photoconversion is inhibited. These proteins were assembled with the natural chromophore biliverdin (BV), with phycoerythrobilin (PEB), which lacks a double bond in the ring C-D-connecting methine bridge, and with synthetic bilin derivatives in which the ring C-D-connecting methine bridge is locked. All PEB and locked chromophore adducts are photoinactive. According to fluorescence quantum yields, the adducts may be divided into four different groups: wild type BV adducts exhibiting a weak fluorescence, mutant BV adducts with about 10-fold enhanced fluorescence, adducts with locked chromophores in which the fluorescence quantum yields are around 0.02, and PEB adducts with a high quantum yield of around 0.5. Thus, the strong fluorescence of the PEB adducts is not reached by the locked chromophore adducts, although the photoconversion energy dissipation pathway is blocked. We therefore suggest that ring D of the bilin chromophore, which contributes to the extended π-electron system of the locked chromophores, provides an energy dissipation pathway that is independent on photoconversion.

  17. Factors affecting the estimation of the relative amount of chromophore and chromophore area by the two-wavelength method of Patau and Ornstein.

    Science.gov (United States)

    Van Oostveldt, P; Boeken, G

    1976-05-28

    Factors influencing the calculation of the relative amount of chromophore and the chromophore area by the two-wavelength method are examined. The study was carried out with the help of models and further tested on Feulgen stained preparations. Except for certain restrictions the difference between the chromophore area as calculated from the two transmissions measurements and the chromophore area obtained by planimetry can be used as a guide for determining the proper measuring conditions, including the choise of the two wavelengths.

  18. Large negative hyperpolariza-bilities (b) of the protonated Schiff bases of the azulenic retinal analogues

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The molecular first hyperpolarizabilities (b) and electronic properties of some azulenic retinal analogues and their derivatives have been investigated theoretically by employing semiempirical approaches. The results indicate that the protonated Schiff bases (PSB) of the 2-substituted azulenic retinal analogues possess extremely large negative b values and very good transparency. These can be attributed to the large difference between the ground state dipole moment and the first excited state dipole moment according to the electronic property analysis. The characteristic blue- shifted absorption in polar solvents of the 2-substituted PSB chromophores can be well explained by the negative solvato-chromic effects. The largest calculated |mb | value can reach the magnitude of 10-44 esu, which is close to the highest re-ported values of synthesized chromophores.

  19. Spectral diffusion and drift: single chromophore and en masse.

    Science.gov (United States)

    Lubchenko, Vassiliy; Silbey, Robert J

    2007-02-14

    We develop a systematic description of spectral diffusion of ideal chromophores interacting with incoherently relaxing two-state, localized environmental degrees of freedom ("spins") for general initial environment configurations. We remedy the existing, incomplete treatments by formulating the problem in terms of the proper correlation function and by obtaining an accurate solution for generic aperiodic arrangements of environmental spins, nearly free of the customary simplifying assumptions on the multiparticle spin coordinate distribution. We report and estimate, for the first time, the effects of the drift and distortion of a narrow spectral line that arise when the line is not in the center of the inhomogeneous band. While the drift turns out to be modest in most ensemble measurements, accounting for its effects is imperative in analyzing single chromophore spectral jumps, to which end the authors propose a novel experiment. Further, we argue that by employing a sufficiently large chromophore one can decouple the concentration of the fluctuating centers from the strength of their interaction with the chromophore. Finally, the additional line broadening, owing to a distribution of the central chromophore frequencies, is evaluated. Upper estimates for an analogous broadening stemming from a nonequilibrium environment are made.

  20. Photostability of amino acids: photodissociation dynamics of phenylalanine chromophores.

    Science.gov (United States)

    Tseng, Chien-Ming; Lin, Ming-Fu; Yang, Yi Lin; Ho, Yu Chieh; Ni, Chi-Kung; Chang, Jia-Lin

    2010-05-21

    The theoretical prediction of H atom elimination on the excited state of phenol, imidazole and indole, the respective chromophores for the amino acids tyrosine, histidine and tryptophan, and the confirmation of theoretical prediction by experimental observations have a great impact on the explanation of photostability of amino acids upon irradiation with UV photons. On the other hand, no theoretical prediction of the excited state photodissociation dynamics has been made on the other aromatic amino acid, phenylalanine. In this work, photodissociation dynamics for various phenylalanine chromophores, including, phenylethylamine, N-methyl-phenylethylamine, and N-acetyl phenylalanine methyl ester was investigated in a molecular beam at 248 and 193 nm using multimass ion imaging techniques. The major dissociation channel for these compounds is the C-C bond cleavage. However, the photofragment translational energy distribution of phenylethylamine contains two components. The slow component corresponds to the dissociation on the ground state surface after internal conversion, and the fast component represents the dissociation from an excited state with a large exit barrier. The competition between the dissociation on the ground state and on the excited state changes as the size of chromophores increases. Internal conversion to the ground state prior to dissociation becomes the major nonradiative process for large chromophores. This study reveals the size-dependent photostability for these amino acid chromophores.

  1. Substrates and method for determining enzymes

    Science.gov (United States)

    Smith, Robert E.; Bissell, Eugene R.

    1981-01-01

    A method is disclosed for determining the presence of an enzyme in a biological fluid, which includes the steps of contacting the fluid with a synthetic chromogenic substrate, which is an amino acid derivative of 7-amino-4-trifluoromethylcoumarin; incubating the substrate-containing fluid to effect enzymatic hydrolysis; and fluorometrically determining the presence of the free 7-amino-4-trifluoromethylcoumarin chromophore in the hydrolyzate.

  2. Photophysical properties of a synthetic, carbonyl-containing (N = 6+Cdbnd O) carotenoid analogue

    Science.gov (United States)

    Niedzwiedzki, Dariusz M.

    2014-05-01

    Retinyl-1 is a synthetic carotenoid analogue belonging to the retinal analogues family. It has six conjugated carbon-carbon double bonds with a carbonyl group conjugated to the π-electron system. Presence of the carbonyl group in vicinity of the conjugated carbon-carbon backbone leads to unique excited state properties that are extremely sensitive to solvent polarity and temperature. The simplicity of the synthesis of Retinyl-1 and ease of attachment to synthetic tetrapyrrole chromophores make Retinyl-1 attractive for use in artificial photosynthetic systems.

  3. Photophysical properties of a synthetic, carbonyl-containing (N=6+CO) carotenoid analogue

    Energy Technology Data Exchange (ETDEWEB)

    Niedzwiedzki, Dariusz M. [Washington Univ., St. Louis, MO (United States)

    2014-05-01

    Retinyl-1 is a synthetic carotenoid analogue belonging to the retinal analogues family. It has six conjugated carbon–carbon double bonds with a carbonyl group conjugated to the π-electron system. Presence of the carbonyl group in vicinity of the conjugated carbon–carbon backbone leads to unique excited state properties that are extremely sensitive to solvent polarity and temperature. The simplicity of the synthesis of Retinyl-1 and ease of attachment to synthetic tetrapyrrole chromophores make Retinyl-1 attractive for use in artificial photosynthetic systems.

  4. Carcinogenicity of insulin analogues

    NARCIS (Netherlands)

    Braak, Sebastiaan Johannes ter

    2015-01-01

    There is epidemiological evidence that the use of some insulin analogues by diabetic patients is correlated with an increased cancer risk. In vitro exposure experiments revealed that insulin glargine (LANTUS) was the only commercial insulin analogue with an increased mitogenic potential. In the huma

  5. Survey of analogue spacetimes

    CERN Document Server

    Visser, Matt

    2013-01-01

    Analogue spacetimes, (and more boldly, analogue models both of and for gravity), have attracted significant and increasing attention over the last decade and a half. Perhaps the most straightforward physical example, which serves as a template for most of the others, is Bill Unruh's model for a dumb hole, (mute black hole, acoustic black hole), wherein sound is dragged along by a moving fluid --- and can even be trapped behind an acoustic horizon. This and related analogue models for curved spacetimes are useful in many ways: Analogue spacetimes provide general relativists with extremely concrete physical models to help focus their thinking, and conversely the techniques of curved spacetime can sometimes help improve our understanding of condensed matter and/or optical systems by providing an unexpected and countervailing viewpoint. In this introductory chapter, I shall provide a few simple examples of analogue spacetimes as general background for the rest of the contributions.

  6. Theoretical investigation of nonlinear properties of electrooptical chromophores

    Institute of Scientific and Technical Information of China (English)

    Zhou Yu-fang; Zhuang De-xin

    2004-01-01

    Organic electrooptical (EO) chromophores are now gaining more attention because the property of organic photorefrative (PR) materials could be controlled by doped EO chromophores. In this paper, nonlinear optical (NLO) properties of a new group of organic electrooptical chromophores, synthesized recently in our laboratory, were elucidated theoretically with the quantum chemical density functional theory (DFT) and the intermediate neglect of differential overlap Hamilton and the configuration interaction (INDO/CI), as well as semiemperical Austin Model 1 (AM1) methods. The electronic transition intensity, dipole moment and the second- order polarizability were obtained. The results show this group of chrormophores possess appropriate optical absorption property and good electrooptical property and optical activity. The second-order polarizabilities βare as large as the order of 10-29 to 10-28 ESU, indicating the promising applications in the future. The physical mechanism of NLO is discussed by means of molecular orbital and electronic charge distribution.

  7. Molecular design of new chromophores for high performance poled polymers

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Based on the principles of molecular engineering, a series of new chromophores with high second-or der nonlinear optical(NLO)activities have been designed for achieving a trade-off of the nonlinearity-transparency-ther mal stability. The NLO properties of these chromophores have been investigated theoretically by employing the AMI/Fi nite Field approach. It is found that the calculated μβ0 values of some designed chromophores can reach the magnitude of 10-45 esu, and the highest decomposition temperature Td can be as high as 377℃, the highest glass transition tem perature Ts of their donor-embedded addition-type polyimides can be as high as 324℃.

  8. Supramolecular clippers for controlling photophysical processes through preorganized chromophores.

    Science.gov (United States)

    Kumar, Mohit; Ushie, Onumashi Afi; George, Subi J

    2014-04-22

    A novel supramolecular clipping design for influencing the photophysical properties of functional molecular assemblies, by the preorganization (clipping) of chromophores, is described. Several chromophores end functionalized with molecular recognition units were designed. These molecular recognition units serve as handles to appropriately position these systems upon noncovalent interactions with multivalent guest molecules (supramolecular clippers). Towards this goal, we have synthesized 1,5-dialkoxynaphthalene (DAN) and naphthalenediimide (NDI) functionalized with dipicolylethylenediamine (DPA) motifs. These molecules could preorganize upon noncovalent clipping with adenosine di- or triphosphates, which resulted in preassociated excimers and mixed (cofacial) charge-transfer (CT) assemblies. Chiral guest binding could also induce supramolecular chirality, not only into the individual chromophoric assembly but also into the heteromeric CT organization, as seen from the strong circular dichroism (CD) signal of the CT transition. The unique ability of this design to influence the intermolecular interactions by changing the binding strength of the clippers furthermore makes it very attractive for controlling the bimolecular photophysical processes.

  9. Synthesis of Polymers Containing Covalently Bonded NLO Chromophores

    Science.gov (United States)

    Denga, Xiao-Hua; Sanghadasa, Mohan; Walton, Connie; Penn, Benjamin B.; Amai, Robert L. S.; Clark, Ronald D.

    1998-01-01

    Polymers containing covalently bonded nonlinear optical (NLO) chromophores are expected to possess special properties such as greater stability, better mechanical processing, and easier film formation than their non-polymeric equivalent. For the present work, polymethylmethacrylate (PMMA) was selected as the basic polymer unit on which to incorporate different NLO chromophores. The NLO components were variations of DIVA {[2-methoxyphenyl methylidene]-propanedinitrile} which we prepared from vanillin derivatives and malononitrile. These were esterified with methacrylic acid and polymerized either directly or with methyl methacrylate to form homopolymers or copolymers respectively. Characterization of the polymers and NLO property studies are underway.

  10. Chromophore Deprotonation State Alters the Optical Properties of Blue Chromoprotein.

    Directory of Open Access Journals (Sweden)

    Cheng-Yi Chiang

    Full Text Available Chromoproteins (CPs have unique colors and can be used in biological applications. In this work, a novel blue CP with a maximum absorption peak (λmax at 608 nm was identified from the carpet anemone Stichodactyla gigantea (sgBP. In vivo expression of sgBP in zebrafish would change the appearance of the fishes to have a blue color, indicating the potential biomarker function. To enhance the color properties, the crystal structure of sgBP at 2.25 Å resolution was determined to allow structure-based protein engineering. Among the mutations conducted in the Gln-Tyr-Gly chromophore and chromophore environment, a S157C mutation shifted the λmax to 604 nm with an extinction coefficient (ε of 58,029 M-1·cm-1 and darkened the blue color expression. The S157C mutation in the sgBP chromophore environment could affect the color expression by altering the deprotonation state of the phenolic group in the chromophore. Our results provide a structural basis for the blue color enhancement of the biomarker development.

  11. Photonic engineering of hybrid metal-organic chromophores

    CERN Document Server

    Busson, Mickaël P; Stout, Brian; Bonod, Nicolas; Wenger, Jérôme; Bidault, Sébastien; 10.1002/anie.201205995

    2012-01-01

    We experimentally demonstrate control of the absorption and emission properties of individual emitters by photonic antennas in suspension. The method results in a new class of water-soluble chromophores with unprecedented photophysical properties, such as short lifetime, low quantum yield but high brightness.

  12. The Structure of the Chromophore within a Red Fluorescent Protein from Zoanthus sp.

    Science.gov (United States)

    2006-05-01

    chromophore interacts with a protein environment. In the denatured state chromophore interactions with aminoacid side chains do not contribute...of aminoacid sequence of the chromopeptide The zFP576 chromophore-bearing peptide derived from extensive chymotryptic digestion was subjected to

  13. Synthesis of Tonghaosu Analogues

    Institute of Scientific and Technical Information of China (English)

    SUN Hai; LIN Yingjie; WU Yulin; WU Yikang

    2009-01-01

    Several new analogues of natural antifeedant tonghaosu were synthesized via m-CPBA (m-chloroperoxybenzoic acid) oxidation of corresponding 3-(a-furyl)propanols, Luche reduction of the resulting enone, epoxidation, acid-mediated spiroketalization, and radical mediated dehydration.

  14. Two-Photon Absorption of Metal-Assisted Chromophores.

    Science.gov (United States)

    Li, Xin; Rinkevicius, Zilvinas; Ågren, Hans

    2014-12-09

    Aiming to understand the effect of a metal surface on nonlinear optical properties and the combined effects of surface and solvent environments on such properties, we present a multiscale response theory study, integrated with dynamics of the two-photon absorption of 4-nitro-4'-amino-trans-stilbene physisorbed on noble metal surfaces, considering two such surfaces, Ag(111) and Au(111), and two solvents, cyclohexane and water, as cases for demonstration. A few conclusions of general character could be drawn: While the geometrical change of the chromophore induced by the environment was found to notably alter (diminish) the two-photon absorption cross section in the polar medium, the effects of the metal surface and solvent on the electronic structure of the chromophore surpasses the geometrical effects and leads to a considerably enhanced two-photon absorption cross section in the polar solvent. This enhancement of two-photon absorption arises essentially from the metal charge image induced enlargement of the difference between the dipole moment of the excited state and the ground state. The orientation-dependence of the two-photon absorption is found to connect with the lateral rotation of the chromophore, where the two-photon absorption reaches its maximum when the polarization of the incident light coincides with the long-axis of the chromophore. Our results demonstrate a distinct enhancement of the two-photon absorption by a metal surface and a polar medium and envisage the employment of metal-chromophore composite materials for future development of nonlinear optical materials with desirable properties.

  15. The electronic excited states of green fluorescent protein chromophore models

    Science.gov (United States)

    Olsen, Seth Carlton

    We explore the properties of quantum chemical approximations to the excited states of model chromophores of the green fluorescent protein of A. victoria. We calculate several low-lying states by several methods of quantum chemical calculation, including state-averaged complete active space SCF (CASSCF) methods, time dependent density functional theory (TDDFT), equation-of motion coupled cluster (EOM-CCSD) and multireference perturbation theory (MRPT). Amongst the low-lying states we identify the optically bright pipi* state of the molecules and examine its properties. We demonstrate that the state is dominated by a single configuration function. We calculate zero-time approximations to the resonance Raman spectrum of GFP chromophore models, and assign published spectra based upon these.

  16. DNA-Conjugated Organic Chromophores in DNA Stacking Interactions

    DEFF Research Database (Denmark)

    Filichev, Vyacheslav V.; Pedersen, Erik Bjerregaard

    2009-01-01

    Since the discovery of the intercalation of acridine derivatives into DNA (1961), chemists have synthesized many intercalators tethered to DNA. Advances in the chemical synthesis of modified nucleosides along with progress in oligonucleotide synthesis have made it possible to introduce organic ch...... review presents those efforts in the design of intercalators/organic chromophores as oligonucleotide conjugates that form a foundation for the generation of novel nucleic acid architectures...

  17. The Biogeochemistry of Chromophoric Dissolved Organic Matter in Coastal Waters

    Science.gov (United States)

    2016-06-07

    The Biogeochemistry of Chromophoric Dissolved Organic Matter in Coastal Waters Robert F. Chen Environmental , Coastal and Ocean Sciences University of...properties to governing physical processes in high energy environments such as coastal seas. In addition, large spatial coverage over a wide range of...optical measurements of CDOM. In order to reliably predict the important photochemical, biological, and chemical processes governing CDOM, and hence its

  18. Method Of Signal Amplification In Multi-Chromophore Luminescence Sensors

    Energy Technology Data Exchange (ETDEWEB)

    Levitsky, Igor A. (Fall River, MA); Krivoshlykov, Sergei G. (Shrewsbury, MA)

    2004-02-03

    A fluorescence-based method for highly sensitive and selective detection of analyte molecules is proposed. The method employs the energy transfer between two or more fluorescent chromophores in a carefully selected polymer matrix. In one preferred embodiment, signal amplification has been achieved in the fluorescent sensing of dimethyl methylphosphonate (DMMP) using two dyes, 3-aminofluoranthene (AM) and Nile Red (NR), in a hydrogen bond acidic polymer matrix. The selected polymer matrix quenches the fluorescence of both dyes and shifts dye emission and absorption spectra relative to more inert matrices. Upon DMMP sorption, the AM fluorescence shifts to the red at the same time the NR absorption shifts to the blue, resulting in better band overlap and increased energy transfer between chromophores. In another preferred embodiment, the sensitive material is incorporated into an optical fiber system enabling efficient excitation of the dye and collecting the fluorescent signal form the sensitive material on the remote end of the system. The proposed method can be applied to multichromophore luminescence sensor systems incorporating N-chromophores leading to N-fold signal amplification and improved selectivity. The method can be used in all applications where highly sensitive detection of basic gases, such as dimethyl methylphosphonate (DMMP), Sarin, Soman and other chemical warfare agents having basic properties, is required, including environmental monitoring, chemical industry and medicine.

  19. ACTINOMYCIN D ANALOGUES

    DEFF Research Database (Denmark)

    1997-01-01

    The present invention relates to new compounds being structurally and functionally similar to Actinomycin D and to combinatorial libraries of such compounds. The Actinomycin D analogues according to the present invention comprise two linear or cyclic peptide moieties constituted by $g...

  20. Synthesis and physicochemical characterization of copolymers of 3-octylthiophene and thiophene functionalized with azo chromophore

    Energy Technology Data Exchange (ETDEWEB)

    Nicho, M.E., E-mail: menicho@uaem.mx [Centro de Investigacion en Ingenieria y Ciencias Aplicadas, Universidad Autonoma del Estado de Morelos (UAEM), Av. Universidad 1001, Col. Chamilpa, C.P. 62209, Cuernavaca, Morelos (Mexico); Garcia-Carvajal, S.; Marquez-Aguilar, P.A.; Gueizado-Rodriguez, M. [Centro de Investigacion en Ingenieria y Ciencias Aplicadas, Universidad Autonoma del Estado de Morelos (UAEM), Av. Universidad 1001, Col. Chamilpa, C.P. 62209, Cuernavaca, Morelos (Mexico); Escalante-Garcia, J. [Centro de Investigaciones Quimicas, UAEM, C.P. 62210, Cuernavaca, Morelos (Mexico); Medrano-Baca, G. [Centro de Investigacion en Ingenieria y Ciencias Aplicadas, Universidad Autonoma del Estado de Morelos (UAEM), Av. Universidad 1001, Col. Chamilpa, C.P. 62209, Cuernavaca, Morelos (Mexico)

    2011-10-03

    Highlights: {yields} Azo chromophore in the copolymer showed an additional color to the P3OT. {yields} Non-linear optical properties by Z-scan technique in states: neutral and oxidized. {yields} The copolymers showed a change of non-linearity sign when the films were doped. {yields} We determined that the nonlinearity of the polymer films was a Kerr type. {yields} This study is the first report of NLO characterization of this material. - Abstract: Polythiophene derivatives with azo chromophore were synthesized via copolymerization of 3-octylthiophene (3OT) and 2-[N-ethyl-N-[4-[(4-nitrophenyl)azo]phenyl]amino]ethyl 3-thienylacetate (3-DRT). This copolymer has interesting optoelectronic properties and a variety of applications such as electrochromic and electronic devices. The polymerization process of 3OT and the functionalized thiophene was carried out via FeCl{sub 3} oxidative polymerization. Thin films of poly(3OT-co-3-DRT) copolymer were prepared by spin-coating technique from toluene. FTIR and {sup 1}H NMR spectroscopy revealed the presence of chromophore groups in the copolymer chain. Molecular weight and polydispersity of the polymers were measured by size exclusion chromatography. Changes in the surface topography of copolymers were analyzed by atomic force microscopy; the results showed that the copolymers presented some protuberances of variable size unlike the homogeneous granular morphology of P3OT. It is believed that these changes appeared by the incorporation of 3-DRT in the polymer. P3ATs are electrochromic materials that show color change upon oxidation-reduction process. We report that electrochemical characterization of poly(3OT-co-3-DRT) copolymer films synthesized chemically on indium-tin oxide (ITO) glass substrates showed an additional color to the P3OT homopolymer. Optical absorption properties of the polymer films were analyzed in the undoped and doped states and as a function of 3-DRT concentration in the copolymer. The nonlinear optical

  1. Highly efficient and selective photocatalytic oxidation of sulfide by a chromophore-catalyst dyad of ruthenium-based complexes.

    Science.gov (United States)

    Li, Ting-Ting; Li, Fu-Min; Zhao, Wei-Liang; Tian, Yong-Hua; Chen, Yong; Cai, Rong; Fu, Wen-Fu

    2015-01-05

    Electronic coupling across a bridging ligand between a chromophore and a catalyst center has an important influence on biological and synthetic photocatalytic processes. Structural and associated electronic modifications of ligands may improve the efficiency of photocatalytic transformations of organic substrates. Two ruthenium-based supramolecular assemblies based on a chromophore-catalyst dyad containing a Ru-aqua complex and its chloro form as the catalytic components were synthesized and structurally characterized, and their spectroscopic and electrochemical properties were investigated. Under visible light irradiation and in the presence of [Co(NH3)5Cl]Cl2 as a sacrificial electron acceptor, both complexes exhibited good photocatalytic activity toward oxidation of sulfide into the corresponding sulfoxide with high efficiency and >99% product selectivity in neutral aqueous solution. The Ru-aqua complex assembly was more efficient than the chloro complex. Isotopic labeling experiments using (18)O-labeled water demonstrated the oxygen atom transfer from the water to the organic substrate, likely through the formation of an active intermediate, Ru(IV)═O.

  2. LDRD final report : energy conversion using chromophore-functionalized carbon nanotubes.

    Energy Technology Data Exchange (ETDEWEB)

    Vance, Andrew L.; Zifer, Thomas; Zhou, Xinjian; Leonard, Francois Leonard; Wong, Bryan Matthew; Kane, Alexander; Katzenmeyer, Aaron Michael; Krafcik, Karen Lee

    2010-09-01

    With the goal of studying the conversion of optical energy to electrical energy at the nanoscale, we developed and tested devices based on single-walled carbon nanotubes functionalized with azobenzene chromophores, where the chromophores serve as photoabsorbers and the nanotube as the electronic read-out. By synthesizing chromophores with specific absorption windows in the visible spectrum and anchoring them to the nanotube surface, we demonstrated the controlled detection of visible light of low intensity in narrow ranges of wavelengths. Our measurements suggested that upon photoabsorption, the chromophores isomerize to give a large change in dipole moment, changing the electrostatic environment of the nanotube. All-electron ab initio calculations were used to study the chromophore-nanotube hybrids, and show that the chromophores bind strongly to the nanotubes without disturbing the electronic structure of either species. Calculated values of the dipole moments supported the notion of dipole changes as the optical detection mechanism.

  3. Photoresponse of the protonated Schiff-base retinal chromophore in the gas phase

    DEFF Research Database (Denmark)

    Toker, Jonathan; Rahbek, Dennis Bo; Kiefer, H V

    2013-01-01

    The fragmentation, initiated by photoexcitation as well as collisionally-induced excitation, of several retinal chromophores was studied in the gas phase. The chromophore in the protonated Schiff-base form (RPSB), essential for mammalian vision, shows a remarkably selective photoresponse. The sel......The fragmentation, initiated by photoexcitation as well as collisionally-induced excitation, of several retinal chromophores was studied in the gas phase. The chromophore in the protonated Schiff-base form (RPSB), essential for mammalian vision, shows a remarkably selective photoresponse...... modifications of the chromophore. We propose that isomerizations play an important role in the photoresponse of gas-phase retinal chromophores and guide internal conversion through conical intersections. The role of protein interactions is then to control the specificity of the photoisomerization in the primary...

  4. Gastric inhibitory polypeptide analogues

    DEFF Research Database (Denmark)

    Holst, Jens Juul

    2002-01-01

    of GIP and GLP-1 receptors, the incretin effect is essential for normal glucose tolerance. In patients with type 2 diabetes mellitus it turns out that the incretin effect is severely impaired or abolished. The explanation seems to be that both the secretion of GLP-1 and the effect of GIP are impaired...... (whereas both the secretion of GIP and the effect of GLP-1 are near normal). The impaired GLP-1 secretion is probably a consequence of diabetic metabolic disturbances. The known genetic variations in the GIP receptor sequence are not associated with type 2 diabetes mellitus, but a defective insulinotropic...... and its analogues are attractive as therapeutic agents for type 2 diabetes mellitus, analogues of GIP are unlikely to be effective. On the other hand, GIP seems to play an important role in lipid metabolism, promoting the disposal of ingested lipids, and mice with a targeted deletion of the GIP receptor...

  5. trans and cis Chromophore structures in the kindling fluorescent protein asFP595

    Science.gov (United States)

    Grigorenko, Bella; Savitsky, Alexander; Topol, Igor; Burt, Stanley; Nemukhin, Alexander

    2006-06-01

    The ab initio QM/MM calculations are used to optimize geometry configurations of the chromophore and surrounding residues for the kindling protein asFP595. The time-dependent DFT method is applied to estimate parameters of the S 0-S 1 vertical transition of the chromophore at the protein geometry taking into account effects from the nearest residues. The results of simulations provide a theoretical support to the hypothesis on the possibility of trans-cis izomerization of the chromophore in the mechanism of kindling. The system can absorb light in the trans anion form of the chromophore and emit at longer wavelength in the cis anion form.

  6. Aspartame and Its Analogues

    Science.gov (United States)

    Pavlova, L. A.; Komarova, T. V.; Davidovich, Yurii A.; Rogozhin, S. V.

    1981-04-01

    The results of studies on the biochemistry of the sweet taste are briefly reviewed. The methods of synthesis of "aspartame" — a sweet dipeptide — are considered, its structural analogues are described, and quantitative estimates are made of the degree of sweetness relative to sucrose. Attention is concentrated mainly on problems of the relation between the structure of the substance and its taste in the series of aspartyl derivatives. The bibliography includes 118 references.

  7. H- and J-aggregation of fluorene-based chromophores.

    Science.gov (United States)

    Deng, Yonghong; Yuan, Wen; Jia, Zhe; Liu, Gao

    2014-12-11

    Understanding of H- and J-aggregation behaviors in fluorene-based polymers is significant both for determining the origin of various red-shifted emissions occurring in blue-emitting polyfluorenes and for developing polyfluorene-based device performance. In this contribution, we demonstrate a new theory of the H- and J-aggregation of polyfluorenes and oligofluorenes, and understand the influence of chromosphere aggregation on their photoluminescent properties. H- and J-aggregates are induced by a continuous increasing concentration of the oligofluorene or polyfluorene solution. A relaxed molecular configuration is simulated to illustrate the spatial arrangement of the bonding of fluorenes. It is indicated that the relaxed state adopts a 21 helical backbone conformation with a torsion angle of 18° between two connected repeat units. This configuration makes the formation of H- and J-aggregates through the strong π-π interaction between the backbone rings. A critical aggregation concentration is observed to form H- and J-aggregates for both polyfluorenes and oligofluorenes. These aggregates show large spectral shifts and distinct shape changes in photoluminescent excitation (PLE) and emission (PL) spectroscopy. Compared with "isolated" chromophores, H-aggregates induce absorption spectral blue-shift and fluorescence spectral red-shift but largely reduce fluorescence efficiency. "Isolated" chromophores not only refer to "isolated molecules" but also include those associated molecules if their conjugated backbones are not compact enough to exhibit perturbed absorption and emission. J-aggregates induce absorption spectral red-shift and fluorescence spectral red-shift but largely enhance fluorescence efficiency. The PLE and PL spectra also show that J-aggregates dominate in concentrated solutions. Different from the excimers, the H- and J-aggregate formation changes the ground-state absorption of fluorene-based chromophores. H- and J-aggregates show changeable

  8. Quantum analogue computing.

    Science.gov (United States)

    Kendon, Vivien M; Nemoto, Kae; Munro, William J

    2010-08-13

    We briefly review what a quantum computer is, what it promises to do for us and why it is so hard to build one. Among the first applications anticipated to bear fruit is the quantum simulation of quantum systems. While most quantum computation is an extension of classical digital computation, quantum simulation differs fundamentally in how the data are encoded in the quantum computer. To perform a quantum simulation, the Hilbert space of the system to be simulated is mapped directly onto the Hilbert space of the (logical) qubits in the quantum computer. This type of direct correspondence is how data are encoded in a classical analogue computer. There is no binary encoding, and increasing precision becomes exponentially costly: an extra bit of precision doubles the size of the computer. This has important consequences for both the precision and error-correction requirements of quantum simulation, and significant open questions remain about its practicality. It also means that the quantum version of analogue computers, continuous-variable quantum computers, becomes an equally efficient architecture for quantum simulation. Lessons from past use of classical analogue computers can help us to build better quantum simulators in future.

  9. Analogue Methods in Palaeoecology: Using the analogue Package

    OpenAIRE

    Simpson, Gavin L.

    2007-01-01

    Palaeoecology is an important branch of ecology that uses the subfossil remains of organisms preserved in lake, ocean and bog sediments to inform on changes in ecosystems and the environment through time. The analogue package contains functions to perform modern analogue technique (MAT) transfer functions, which can be used to predict past changes in the environment, such as climate or lake-water pH from species data. A related technique is that of analogue matching, which is concerned with i...

  10. Recovery of red fluorescent protein chromophore maturation deficiency through rational design.

    Directory of Open Access Journals (Sweden)

    Matthew M Moore

    Full Text Available Red fluorescent proteins (RFPs derived from organisms in the class Anthozoa have found widespread application as imaging tools in biological research. For most imaging experiments, RFPs that mature quickly to the red chromophore and produce little or no green chromophore are most useful. In this study, we used rational design to convert a yellow fluorescent mPlum mutant to a red-emitting RFP without reverting any of the mutations causing the maturation deficiency and without altering the red chromophore's covalent structure. We also created an optimized mPlum mutant (mPlum-E16P that matures almost exclusively to the red chromophore. Analysis of the structure/function relationships in these proteins revealed two structural characteristics that are important for efficient red chromophore maturation in DsRed-derived RFPs. The first is the presence of a lysine residue at position 70 that is able to interact directly with the chromophore. The second is an absence of non-bonding interactions limiting the conformational flexibility at the peptide backbone that is oxidized during red chromophore formation. Satisfying or improving these structural features in other maturation-deficient RFPs may result in RFPs with faster and more complete maturation to the red chromophore.

  11. Direct Measurement of the Isomerization Barrier of the Isolated Retinal Chromophore

    DEFF Research Database (Denmark)

    Dilger, Jonathan; Musbat, Lihi; Sheves, Mordechai;

    2015-01-01

    Isomerizations of the retinal chromophore were investigated using the IMS-IMS technique. Four different structural features of the chromophore were observed, isolated, excited collisionally, and the resulting isomer and fragment distributions were measured. By establishing the threshold activatio......V, which is significantly lower than that observed for the reaction within opsin proteins....

  12. Binding, tuning and mechanical function of the 4-hydroxy-cinnamic acid chromophore in photoactive yellow protein

    NARCIS (Netherlands)

    Horst, M.A. van der; Arents, J.C.; Kort, R.; Hellingwerf, K.J.

    2007-01-01

    The bacterial photoreceptor protein photoactive yellow protein (PYP) covalently binds the chromophore 4-hydroxy coumaric acid, tuning (spectral) characteristics of this cofactor. Here, we study this binding and tuning using a combination of pointmutations and chromophore analogs. In all photosensor

  13. Derivatisable Cyanobactin Analogues: A Semisynthetic Approach.

    Science.gov (United States)

    Oueis, Emilia; Adamson, Catherine; Mann, Greg; Ludewig, Hannes; Redpath, Philip; Migaud, Marie; Westwood, Nicholas J; Naismith, James H

    2015-12-01

    Many natural cyclic peptides have potent and potentially useful biological activities. Their use as therapeutic starting points is often limited by the quantities available, the lack of known biological targets and the practical limits on diversification to fine-tune their properties. We report the use of enzymes from the cyanobactin family to heterocyclise and macrocyclise chemically synthesised substrates so as to allow larger-scale syntheses and better control over derivatisation. We have made cyclic peptides containing orthogonal reactive groups, azide or dehydroalanine, that allow chemical diversification, including the use of fluorescent labels that can help in target identification. We show that the enzymes are compatible and efficient with such unnatural substrates. The combination of chemical synthesis and enzymatic transformation could help renew interest in investigating natural cyclic peptides with biological activity, as well as their unnatural analogues, as therapeutics.

  14. The photochemical determinants of color vision: revealing how opsins tune their chromophore's absorption wavelength.

    Science.gov (United States)

    Wang, Wenjing; Geiger, James H; Borhan, Babak

    2014-01-01

    The evolution of a variety of important chromophore-dependent biological processes, including microbial light sensing and mammalian color vision, relies on protein modifications that alter the spectral characteristics of a bound chromophore. Three different color opsins share the same chromophore, but have three distinct absorptions that together cover the entire visible spectrum, giving rise to trichromatic vision. The influence of opsins on the absorbance of the chromophore has been studied through methods such as model compounds, opsin mutagenesis, and computational modeling. The recent development of rhodopsin mimic that uses small soluble proteins to recapitulate the binding and wavelength tuning of the native opsins provides a new platform for studying protein-regulated spectral tuning. The ability to achieve far-red shifted absorption in the rhodopsin mimic system was attributed to a combination of the lack of a counteranion proximal to the iminium, and a uniformly neutral electrostatic environment surrounding the chromophore.

  15. Primary Role of the Chromophore Bond Length Alternation in Reversible Photoconversion of Red Fluorescence Proteins

    Science.gov (United States)

    Drobizhev, Mikhail; Hughes, Thomas E.; Stepanenko, Yuriy; Wnuk, Pawel; O'Donnell, Kieran; Scott, J. Nathan; Callis, Patrik R.; Mikhaylov, Alexander; Dokken, Leslie; Rebane, Aleksander

    2012-01-01

    Rapid photobleaching of fluorescent proteins can limit their use in imaging applications. The underlying kinetics is multi-exponential and strongly depends on the local chromophore environment. The first, reversible, step may be attributed to a rotation around one of the two exocyclic C-C bonds bridging phenol and imidazolinone groups in the chromophore. However it is not clear how the protein environment controls this motion - either by steric hindrances or by modulating the electronic structure of the chromophore through electrostatic interactions. Here we study the first step of the photobleaching kinetics in 13 red fluorescent proteins (RFPs) with different chromophore environment and show that the associated rate strongly correlates with the bond length alternation (BLA) of the two bridge bonds. The sign of the BLA appears to determine which rotation is activated. Our results present experimental evidence for the dominance of electronic effects in the conformational dynamics of the RFP chromophore. PMID:23008753

  16. Primary Role of the Chromophore Bond Length Alternation in Reversible Photoconversion of Red Fluorescence Proteins

    Science.gov (United States)

    Drobizhev, Mikhail; Hughes, Thomas E.; Stepanenko, Yuriy; Wnuk, Pawel; O'Donnell, Kieran; Scott, J. Nathan; Callis, Patrik R.; Mikhaylov, Alexander; Dokken, Leslie; Rebane, Aleksander

    2012-09-01

    Rapid photobleaching of fluorescent proteins can limit their use in imaging applications. The underlying kinetics is multi-exponential and strongly depends on the local chromophore environment. The first, reversible, step may be attributed to a rotation around one of the two exocyclic C-C bonds bridging phenol and imidazolinone groups in the chromophore. However it is not clear how the protein environment controls this motion - either by steric hindrances or by modulating the electronic structure of the chromophore through electrostatic interactions. Here we study the first step of the photobleaching kinetics in 13 red fluorescent proteins (RFPs) with different chromophore environment and show that the associated rate strongly correlates with the bond length alternation (BLA) of the two bridge bonds. The sign of the BLA appears to determine which rotation is activated. Our results present experimental evidence for the dominance of electronic effects in the conformational dynamics of the RFP chromophore.

  17. Chromophore Structure of Photochromic Fluorescent Protein Dronpa: Acid-Base Equilibrium of Two Cis Configurations.

    Science.gov (United States)

    Higashino, Asuka; Mizuno, Misao; Mizutani, Yasuhisa

    2016-04-07

    Dronpa is a novel photochromic fluorescent protein that exhibits fast response to light. The present article is the first report of the resonance and preresonance Raman spectra of Dronpa. We used the intensity and frequency of Raman bands to determine the structure of the Dronpa chromophore in two thermally stable photochromic states. The acid-base equilibrium in one photochromic state was observed by spectroscopic pH titration. The Raman spectra revealed that the chromophore in this state shows a protonation/deprotonation transition with a pKa of 5.2 ± 0.3 and maintains the cis configuration. The observed resonance Raman bands showed that the other photochromic state of the chromophore is in a trans configuration. The results demonstrate that Raman bands selectively enhanced for the chromophore yield valuable information on the molecular structure of the chromophore in photochromic fluorescent proteins after careful elimination of the fluorescence background.

  18. Influence of Architecture, Concentration, and Thermal History on the Poling of Nonlinear Optical Chromophores in Block Copolymer Domains

    Energy Technology Data Exchange (ETDEWEB)

    Leolukman, Melvina; Paoprasert, Peerasak; Wang, Yao; Makhija, Varun; McGee, David J.; Gopalan, Padma (UW)

    2008-10-02

    Factors affecting the electric-field-induced poling of nonlinear optical chromophores in block copolymer domains were investigated by encapsulating the chromophores in a linear-diblock copolymer [poly(styrene-b-4-vinylpyridine)] and linear-dendritic (poly(methyl methacrylate)-dendron) block copolymer via hydrogen bonding. Temperature-dependent Fourier transform infrared spectroscopy and morphology evaluation by X-ray scattering and transmission electron microscopy were used with in situ second harmonic generation to correlate domain architectures, processing conditions such as thermal history, and chromophore concentrations with poling efficiency. Poling of chromophores encapsulated in the minority domain (spheres or cylinders) of a linear-diblock copolymer was inhibited by the increasing chromophore concentration within the domain and the chemical nature of the majority domain. Chromophore encapsulation in the majority domain produced the most favorable conditions for poling as measured by in situ second harmonic generation. Thermal annealing of the linear-diblock copolymer/chromophore composites resulted in chromophore aggregation with a corresponding decrease in nonlinear optical activity. The linear-dendron/chromophore system presented the most effective architecture for spatially dispersing chromophores. These findings suggest that while well-ordered phase-separated systems such as block copolymers enhance chromophore isolation over homopolymer systems, a more effective approach is to explore polymer chains end functionalized with chromophores.

  19. Photochromic gratings in sol gel films containing diazo sulfonamide chromophore

    Science.gov (United States)

    Kucharski, Stanisław; Janik, Ryszard

    2005-09-01

    The photochromic sol-gel hybrid materials were prepared by incorporation of an azo chromophore containing sulfonamide fragment into polysiloxane cross-linked network. The materials were used to form transparent films on glass by spin-coating and/or casting. The reversible change of refraction index of the films on illumination with white light was observed by ellipsometry. The experiments with two beam coupling (TBC) and four wave mixing (4 WM) arrangement with green or blue laser beams as writing beams showed formation of a diffraction grating. The diffraction efficiency of the first order was 0.025-0.038 which yielded refraction index modulation in the range of up to 0.0066.

  20. Figures of merit of nonlinear optical chromophores in photorefractive polymers

    Science.gov (United States)

    Barzoukas, Marguerite; Blanchard-Desce, Mireille H.; Wortmann, Ruediger W.

    1999-05-01

    A pre-requisite to obtain polymers with a large photorefractive response is to design non-linear optical chromophores with a large figure of merit. This figure depends on the glass transition temperature of the material. We present a theoretical investigation that shows which are the important molecular parameters that control the magnitude of the figure of merit either in a low-Tg or in a high-Tg polymer. Derivation of the figures of merit for various push-pull molecules show a molecular engineering strategy can be successfully implemented to yield very large figures of merit. This approach is supported by an experimental investigation based on electro-optical absorption measurements.

  1. Development and Characterization of Reactive Triangulenium Chromophores for Bioconjugation Applications

    DEFF Research Database (Denmark)

    Bora, Ilkay

    With the continuing development of advanced fluorescence techniques such as single-molecule fluorescence, time-gated detection, multiple laser pulse excitation, anisotropy decay assays and quenching experiments, fluorescent dyes are needed whose focus does not only lie on classic emission amplitude.......66 in acetonitrile. Their saliently high lifetimes of up to 23 ns in acetonitrile allow for autofluorescence eliminating time-gated measurements; combined with their strongly polarized transitions they enable the measurement of slow protein dynamics. Synthetic strategies developed by Laursen and Krebs allow...... maleimides were introduced into the azadioxa- and diazaoxa-triangulenium chromophores. The effect of the linker rigidity on the local mobility of the fluorophore on protein surfaces and the resulting retardation of initial emission anisotropy loss in time-resolved experiments were then investigated...

  2. Chromophore-assisted laser inactivation in neural development

    Institute of Scientific and Technical Information of China (English)

    Wei Li; Nico Stuurman; Guangshuo Ou

    2012-01-01

    Chromophore-assisted laser inactivation (CALI) is a technique that uses photochemically-generated reactive oxygen species to acutely inactivate target proteins in living cells.Neural development includes highly dynamic cellular processes such as asymmetric cell division,migration,axon and dendrite outgrowth and synaptogenesis.Although many key molecules of neural development have been identified since the past decades,their spatiotemporal contributions to these cellular events are not well understood.CALI provides an appealing tool for elucidating the precise functions of these molecules during neural development.In this review,we summarize the principles of CALI,a recent microscopic setup to perform CALI experiments,and the application of CALI to the study of growth-cone motility and neuroblast asymmetric division.

  3. A Short Term Analogue Memory

    DEFF Research Database (Denmark)

    Shah, Peter Jivan

    1992-01-01

    A short term analogue memory is described. It is based on a well-known sample-hold topology in which leakage currents have been minimized partly by circuit design and partly by layout techniques. Measurements on a test chip implemented in a standard 2.4 micron analogue CMOS process show a droop...

  4. Vorticity in analogue gravity

    CERN Document Server

    Cropp, Bethan; Turcati, Rodrigo

    2015-01-01

    In the analogue gravity framework, the acoustic disturbances in a moving fluid can be described by an equation of motion identical to a relativistic scalar massless field propagating in a curved spacetime. This description is possible only when the fluid under consideration is barotropic, inviscid and irrotational. In this case, the propagation of the perturbations is governed by an acoustic metric which depends algebrically on the local speed of sound, density and the background flow velocity, the latter assumed to be vorticity free. In this work we provide an straightforward extension in order to go beyond the irrotational constraint. Using a charged --- relativistic and non-relativistic --- Bose--Einstein condensate as a physical system, we show that in the low momentum limit and performing the eikonal approximation we can derive a d'Alembertian equation of motion for the charged phonons where the emergent acoustic metric depends on a flow velocity in the presence of vorticity.

  5. Chromophore incorporation, Pr to Pfr kinetics, and Pfr thermal reversion of recombinant N-terminal fragments of phytochrome A and B chromoproteins.

    Science.gov (United States)

    Remberg, A; Ruddat, A; Braslavsky, S E; Gärtner, W; Schaffner, K

    1998-07-14

    N-Terminal apoprotein fragments of oat phytochrome A (phyA) of 65 kDa (amino acids 1-595) and potato phyB of 66 kDa (1-596) were heterologously expressed in Escherichia coli and in the yeasts Saccharomyces cerevisiae and Pichia pastoris, and assembled with phytochromobilin (PthetaB; native chromophore) and phycocyanobilin (PCB). The phyA65 apoprotein from yeast showed a monoexponential assembly kinetics after an initial steep rise, whereas the corresponding apoprotein from E. coli showed only a slow monoexponential assembly. The phyB66 apoprotein incorporated either chromophore more slowly than the phyA65s, with biexponential kinetics. With all apoproteins, PthetaB was incorporated faster than PCB. The thermal stabilities of the Pfr forms of the N-terminal halves are similar to those known for the full-length recombinant phytochromes: oat phyA65 Pfr is highly stable, whereas potato phyB66 Pfr is rapidly converted into Pr. Thus, neither the C-terminal domain nor homodimer formation regulates this property. Rather, it is a characteristic of the phytochrome indicating its origin from mono- or dicots. The Pr to Pfr kinetics of the N-terminal phyA65 and phyB66 are different. The primary photoproduct I700 of phyA65-PCB decayed monoexponentially and the PthetaB analogue biexponentially, whereas the phyB66 I700 decayed monoexponentially irrespective of the chromophore incorporated. The formation of Pfr from Pr is faster with the N-terminal halves than with the full-length phytochromes, indicating an involvement of the C-terminal domain in the relatively slow protein conformational changes.

  6. Excitation Emission Matrix Spectra (EEMS) of Chromophoric Dissolved Organic Matter Produced during Microbial Incubation

    Science.gov (United States)

    McDonald, N.; Nelson, N. B.; Parsons, R.

    2013-12-01

    The chromophoric or light-absorbing fraction of dissolved organic matter (CDOM) is present ubiquitously in natural waters and has a significant impact on ocean biogeochemistry, affecting photosynthesis and primary production as well direct and indirect photochemical reactions (Siegel et al., 2002; Nelson et al., 2007). It has been largely researched in the past few decades, however the exact chemical composition remains unknown. Instrumental methods of analysis including simultaneous excitation-emission fluorescence spectra have allowed for further insight into source and chemical composition. While certain excitation-emission peaks have been associated with ';marine' sources, they have not been exclusively linked to bacterial production of CDOM (Coble, 1996; Zepp et al., 2004). In this study, ';grazer diluted' seawater samples (70% 0.2μm filtered water; 30% whole water) were collected at the Bermuda Atlantic Time Series (BATS) site in the Sargasso Sea (31° 41' N; 64° 10' W) and incubated with an amendment of labile dissolved organic carbon (10μM C6H12O6), ammonium (1μM NH4Cl) and phosphate (0.1μM K2HPO4) to facilitate bacterial production. These substrates and concentrations have been previously shown to facilitate optimum bacterial and CDOM production (Nelson et al., 2004). Sample depths were chosen at 1m and 200m as water at these depths has been exposed to UV light (the Subtropical Mode Water at 200m has been subducted from the surface) and therefore has low initial concentrations of CDOM. After the samples were amended, they were incubated at in-situ temperatures in the dark for 72 hours, with bacteria counts, UV-Vis absorption and EEMS measurements taken at 6-8 hour intervals. Dissolved organic carbon (DOC) measurements were collected daily. For the surface water experiment specific bacteria populations were investigated using Fluorescence In-Situ Hybridization (FISH) analysis. Results showed a clear production of bacteria and production of CDOM, which

  7. Chromophore composition of the phycobiliprotein Cr-PC577 from the cryptophyte Hemiselmis pacifica.

    Science.gov (United States)

    Overkamp, Kristina E; Langklotz, Sina; Aras, Marco; Helling, Stefan; Marcus, Katrin; Bandow, Julia E; Hoef-Emden, Kerstin; Frankenberg-Dinkel, Nicole

    2014-12-01

    The cryptophyte phycocyanin Cr-PC577 from Hemiselmis pacifica is a close relative of Cr-PC612 found in Hemiselmis virescens and Hemiselmis tepida. The two biliproteins differ in that Cr-PC577 lacks the major peak at around 612 nm in the absorption spectrum. Cr-PC577 was thus purified and characterized with respect to its bilin chromophore composition. Like other cryptophyte phycobiliproteins, Cr-PC577 is an (αβ)(α'β) heterodimer with phycocyanobilin (PCB) bound to the α-subunits. While one chromophore of the β-subunit is also PCB, mass spectrometry identified an additional chromophore with a mass of 585 Da at position β-Cys-158. This mass can be attributed to either a dihydrobiliverdin (DHBV), mesobiliverdin (MBV), or bilin584 chromophore. The doubly linked bilin at position β-Cys-50 and β-Cys-61 could not be identified unequivocally but shares spectral features with DHBV. We found that Cr-PC577 possesses a novel chromophore composition with at least two different chromophores bound to the β-subunit. Overall, our data contribute to a better understanding of cryptophyte phycobiliproteins and furthermore raise the question on the biosynthetic pathway of cryptophyte chromophores.

  8. NASA/ESMD Analogue Mission Plans

    Science.gov (United States)

    Hoffman, Stephen J.

    2007-01-01

    A viewgraph presentation exploring Earth and its analogues is shown. The topics include: 1) ESMD Goals for the Use of Earth Analogues; 2) Stakeholders Summary; 3) Issues with Current Analogue Situation; 4) Current state of Analogues; 5) External Implementation Plan (Second Step); 6) Recent Progress in Utilizing Analogues; 7) Website Layout Example-Home Page; 8) Website Layout Example-Analogue Site; 9) Website Layout Example-Analogue Mission; 10) Objectives of ARDIG Analog Initiatives; 11) Future Plans; 12) Example: Cold-Trap Sample Return; 13) Example: Site Characterization Matrix; 14) Integrated Analogue Studies-Prerequisites for Human Exploration; and 15) Rating Scale Definitions.

  9. Role of the conjugated spacer in the optimization of second-order nonlinear chromophores

    Science.gov (United States)

    Pérez-Moreno, Javier; Clays, Koen; Kuzyk, Mark G.

    2009-08-01

    We investigate the role of the conjugated spacer in the optimization of the first hyperpolarizability of organic chromophores. We propose a novel strategy for the optimization of the first hyperpolarizability that is based on the variation of the degree of conjugation for the bridge that separates the donor and acceptors at the end of push-pull type chromophores. The correlation between the type of conjugated spacer and the experimental nonlinear performance of the chromophores is investigated and interpreted in the context of the quantum limits.

  10. Photo-fragmentation and electron-detachment studies of gas-phase chromophore ions

    DEFF Research Database (Denmark)

    Rahbek, Dennis Bo

    During my time as a PhD-student I have worked on increasing our knowledge of biologically relevant photoactive proteins. More specifically, I have studied chromophores that are found within some of these proteins. Upon absorbing a photon, the chromophore initiates a process within the protein....... Depending on the function of the protein, this may result in human vision, emission of light at a higher wavelength, fluorescence, or harvesting of energy used as an energy source by bacteria, algae or plants. The interaction between these chromophores and the surrounding protein is crucial for fine...

  11. Inhibition of Human Arginase I by Substrate adn Product Analogues

    Energy Technology Data Exchange (ETDEWEB)

    L Di Costanzo; M Ilies; K Thorn; D Christianson

    2011-12-31

    Human arginase I is a binuclear manganese metalloenzyme that catalyzes the hydrolysis of L-arginine to generate L-ornithine and urea. We demonstrate that N-hydroxy-L-arginine (NOHA) binds to this enzyme with K(d)=3.6 microM, and nor-N-hydroxy-L-arginine (nor-NOHA) binds with K(d)=517 nM (surface plasmon resonance) or K(d) approximately 50 nM (isothermal titration calorimetry). Crystals of human arginase I complexed with NOHA and nor-NOHA afford 2.04 and 1.55 A resolution structures, respectively, which are significantly improved in comparison with previously-determined structures of the corresponding complexes with rat arginase I. Higher resolution structures clarify the binding interactions of the inhibitors. Finally, the crystal structure of the complex with L-lysine (K(d)=13 microM) is reported at 1.90 A resolution. This structure confirms the importance of hydrogen bond interactions with inhibitor alpha-carboxylate and alpha-amino groups as key specificity determinants of amino acid recognition in the arginase active site.

  12. Chromophoric Dissolved Organic Material, Aqua MODIS, NPP, 0.125 degrees, East US

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — MODIS data is used to develop an index of the amount of chromophoric dissolved organic material (CDOM) in the surface waters. CDOM absorbs heavily in the blue...

  13. Photobleaching Kinetics of Chromophoric Dissolved Organic Matter Derived from Mangrove Leaf Litter and Floating Sargassum Colonies

    Science.gov (United States)

    We examined the photoreactivity of chromophoric dissolved organic matter (CDOM) derived from Rhizophora mangle (red mangrove) leaf litter and floating Sargassum colonies as these marine plants can be important contributors to coastal and open ocean CDOM pools, respectively. Mangr...

  14. Chromophoric Dissolved Organic Material, Aqua MODIS, NPP, 0.125 degrees, West US

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — MODIS data is used to develop an index of the amount of chromophoric dissolved organic material (CDOM) in the surface waters. CDOM absorbs heavily in the blue...

  15. Mechanisms of Formation and Structure of Chromophores of Fluorescent Proteins from Anthoza Species

    Science.gov (United States)

    2005-03-01

    chromophore structure……………………....……………20 Task 6. Isolation of chromophore-bearing peptides from cgCP and gtCP…………………..20 Task 7. Aminoacid ...22 Concluding remarks on gtCP chromophore structure……………………………………………24 Task 7. Aminoacid sequence determination of cgCP chromophore-bearing...side chain by A65G substitution………………....26 The nature of the side chain of aminoacid 65 determines the extent of fragmentation…….........27 Task 9

  16. Chromophoric Dissolved Organic Material, Aqua MODIS, NPP, 0.125 degrees, Gulf of Mexico

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — MODIS data is used to develop an index of the amount of chromophoric dissolved organic material (CDOM) in the surface waters. CDOM absorbs heavily in the blue...

  17. Chromophoric Dissolved Organic Material, Aqua MODIS, NPP, 0.05 degrees, Global, Science Quality

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — MODIS data is used to develop an index of the amount of chromophoric dissolved organic material (CDOM) in the surface waters. CDOM absorbs heavily in the blue...

  18. Bioheterojunction Effect on Fluorescence Origin and Efficiency Improvement of Firefly Chromophores

    CERN Document Server

    Cai, Duanjun; Milne, Bruce F; Nogueira, Fernando; 10.1021/jz1009532

    2010-01-01

    We propose the heterojunction effect in the analysis of the fluorescence mechanism of the firefly chromophore. Following this analysis, and with respect to the HOMO-LUMO gap alignment between the chromophore's functional fragments, three main heterojunction types (I, II, and I*) are identified. Time-dependent density-functional theory optical absorption calculations for the firefly chromophore show that the strongest excitation appears in the deprotonated anion state of the keto form. This can be explained by its high HOMO-LUMO overlap due to strong bio-heterojunction confinement. It is also found that the nitrogen atom in the thiazolyl rings, due to its larger electronegativity, plays a key role in the emission process, its importance growing when HOMO and LUMO overlap at its location. This principle is applied to enhance the chromophore's fluorescence efficiency and to guide the functionalization of molecular optoelectronic devices.

  19. Photo-fragmentation and electron-detachment studies of gas-phase chromophore ions

    DEFF Research Database (Denmark)

    Rahbek, Dennis Bo

    -physical properties of two important bio-chromophores by investigating the properties of structural isomers of these molecules. The chromophores are the ones found in the green fluorescent protein and the photoactive yellow protein. The photo-physical properties have been studied experimentally in the gas phase...... excitation energy. This results in a competition between de-excitation by internal conversion and electron emission. Both of these processes are of non-adiabatic character as they rely on coupling between electronic energy and energy in nuclear motion. Moreover, it is found that higher-lying states...... in the anionic forms serves as ‘doorway’- states into the continuum of the neutral radical. Regarding the structural isomeric forms of each of the chromophores we find that the degree of electronic coupling between the subunitsmaking up the chromophores is crucial for the tuning the absorption properties, both...

  20. Temporal fluctuations in excimer-like interactions between pi-conjugated chromophores

    CERN Document Server

    Stangl, Thomas; Schmitz, Daniela; Remmerssen, Klaas; Henzel, Sebastian; Hoeger, Sigurd; Vogelsang, Jan; Lupton, John M

    2015-01-01

    Inter- or intramolecular coupling processes between chromophores such as excimer formation or H- and J-aggregation are crucial to describing the photophysics of closely packed films of conjugated polymers. Such coupling is highly distance dependent, and should be sensitive to both fluctuations in the spacing between chromophores as well as the actual position on the chromophore where the exciton localizes. Single-molecule spectroscopy reveals these intrinsic fluctuations in well-defined bi-chromophoric model systems of cofacial oligomers. Signatures of interchromophoric interactions in the excited state - spectral red-shifting and broadening, and a slowing of photoluminescence decay - correlate with each other but scatter strongly between single molecules, implying an extraordinary distribution in coupling strengths. Furthermore, these excimer-like spectral fingerprints vary with time, revealing intrinsic dynamics in the coupling strength within one single dimer molecule, which constitutes the starting point ...

  1. Quantum dynamics of electronic excitations in biomolecular chromophores: role of the protein environment and solvent

    CERN Document Server

    Gilmore, J; Gilmore, Joel; Kenzie, Ross H. Mc

    2006-01-01

    We consider continuum dielectric models as minimal models to understand the effect of the surrounding protein and solvent on the quantum dynamics of electronic excitations in a biological chromophore. For these models we describe expressions for the frequency dependent spectral density which describes the coupling of the electronic levels in the chromophore to its environment. We find the contributions to the spectral density from each component of the chromophore environment: the bulk solvent, protein, and water bound to the protein. The relative importance of each component is determined by the time scale on which one is considering the quantum dynamics of the chromophore. Our results provide a natural explanation and model for the different time scales observed in the spectral density extracted from the solvation dynamics probed by ultra-fast laser spectroscopy techniques such as the dynamic Stokes shift and three pulse photon echo spectroscopy. Our results can be used to define under what conditions the d...

  2. Assembly of Agrobacterium phytochromes Agp1 and Agp2 with doubly locked bilin chromophores.

    Science.gov (United States)

    Inomata, Katsuhiko; Khawn, Htoi; Chen, Li-Yi; Kinoshita, Hideki; Zienicke, Benjamin; Molina, Isabel; Lamparter, Tilman

    2009-03-31

    The natural chromophore of most bacterial and fungal phytochromes is biliverdin (BV), which is incorporated in a covalent manner into the protein. Upon photoconversion between the red light-absorbing form Pr and the far-red light-absorbing form Pfr, the stereochemistry of the chromophore around the C15 methine bridge changes from Z anti to E anti. Recombinant phytochromes Agp1 and Agp2 from Agrobacterium tumefaciens were assembled with a set of synthetic chromophores, including 2,18-Et-BV, 3,18-Et-BV, and the doubly locked 5Ea15Ea-BV, 5Es15Ea-BV, 5Za15Ea-BV, and 5Zs15Ea-BV. In all chromophores, covalent bond formation is restricted. As shown by spectral changes and desalting column separation, all chromophores are bound to Agp1 and Agp2. Adducts with 2,18-Et-BV and 3,18-Et-BV undergo normal photoconversion between Pr and Pfr. As opposed to typical phytochromes, the BV-Agp2 adduct converts from Pr to Pfr in darkness. However, the 2,18-Et-BV-Agp2 and 3,18-Et-BV-Agp2 adducts can undergo dark conversion from Pr to Pfr and Pfr to Pr, showing that ring A of the chromophore has a direct impact on the direction of dark conversion. The doubly locked chromophores were designed to probe for the stereochemistry of the C5 methine bridge in the Pfr form. The adducts with 5Es15Ea-BV and 5Zs15Ea-BV absorbed in the blue spectral range only. Therefore, the C5 E syn and Z syn stereochemistries are unlikely for the Pfr chromophore of Agp1 and Agp2. According to our spectra, the Agp2 chromophore most likely adopts an E anti stereochemistry at its C5 methine bridge. Thus, during Pr to Pfr conversion, the C5 methine bridge of the chromophore might undergo a Hula-twist isomerization. In Agp1, the Pfr chromophore is most likely in the C5 Z anti stereochemistry. We propose that the stereochemistry of the C5 methine bridge might differ between different phytochromes, most particularly in the Pfr form.

  3. Assembly of synthetic locked chromophores with agrobacterium phytochromes Agp1 and Agp2.

    Science.gov (United States)

    Inomata, Katsuhiko; Noack, Steffi; Hammam, Mostafa A S; Khawn, Htoi; Kinoshita, Hideki; Murata, Yasue; Michael, Norbert; Scheerer, Patrick; Krauss, Norbert; Lamparter, Tilman

    2006-09-22

    Phytochromes are photoreceptors with a bilin chromophore in which light triggers the conversion between the red-absorbing form Pr and the far-red-absorbing form Pfr. Agrobacterium tumefaciens has two phytochromes, Agp1 and Agp2, with antagonistic properties: in darkness, Agp1 converts slowly from Pfr to Pr, whereas Agp2 converts slowly from Pr to Pfr. In a previous study, we have assembled Agp1 with synthetic locked chromophores 15Za, 15Zs, 15Ea, and 15Es in which the C15=C16 double bond is fixed in either the E or Z configuration and the C14-C15 single bond is fixed in either the syn (s) or anti (a) conformation. In the present study, the locked chromophores 5Za and 5Zs were used for assembly with Agp1; in these chromophores, the C4=C5 double bond is fixed in the Z configuration, and the C5-C6 single bond is fixed in either the syn or anti conformation. All locked chromophores were also assembled with Agp2. The data showed that in both phytochromes the Pr chromophore adopts a C4=C5 Z C5-C6 syn C15=C16 Z C14-C15 anti stereochemistry and that in the Pfr chromophore the C15=C16 double bond has isomerized to the E configuration, whereas the C14-C15 single bond remains in the anti conformation. Photoconversion shifted the absorption maxima of the 5Zs adducts to shorter wavelengths, whereas the 5Za adducts were shifted to longer wavelengths. Thus, the C5-C6 single bond of the Pfr chromophore is rather in an anti conformation, supporting the previous suggestion that during photoconversion of phytochromes, a rotation around the ring A-B connecting single bond occurs.

  4. Primary steps of the photoactive yellow protein: Isolated chromophore dynamics and protein directed function

    OpenAIRE

    Lee, I-Ren; Lee, Wonchul; Zewail, Ahmed H.

    2006-01-01

    The cycle of the photoactive yellow protein (PYP) has been extensively studied, but the dynamics of the isolated chromophore responsible for transduction is unknown. Here, we present real-time observation of the dynamics of the negatively charged chromophore and detection of intermediates along the path of trans-to-cis isomerization using femtosecond mass selection/electron detachment techniques. The results show that the role of the protein environment is not in the first step of double-bond...

  5. Chromophoric dissolved organic matter export from U.S. rivers

    Science.gov (United States)

    Spencer, Robert G. M.; Aiken, George R.; Dornblaser, Mark M.; Butler, Kenna D.; Holmes, R. Max; Fiske, Greg; Mann, Paul J.; Stubbins, Aron

    2013-01-01

    Chromophoric dissolved organic matter (CDOM) fluxes and yields from 15 major U.S. rivers draining an assortment of terrestrial biomes are presented. A robust relationship between CDOM and dissolved organic carbon (DOC) loads is established (e.g., a350 versus DOC; r2 = 0.96, p export from ungauged watersheds. A large variation in CDOM yields was found across the rivers. The two rivers in the north-eastern U.S. (Androscoggin and Penobscot), the Edisto draining into the South Atlantic Bight, and some rivers draining into the Gulf of Mexico (Atchafalaya and Mobile) exhibit the highest CDOM yields, linked to extensive wetlands in these watersheds. If the Edisto CDOM yield is representative of other rivers draining into the South Atlantic Bight, this would result in a CDOM load equivalent to that of the Mississippi from a region of approximately 10% of the Mississippi watershed, indicating the importance of certain regions with respect to the role of terrigenous CDOM in ocean color budgets.

  6. Nuclear Wavepacket Propogation Model for the Retinal Chromophore in Rhodopsin

    Science.gov (United States)

    Corn, Brittany; Malinovskaya, Svetlana

    2009-05-01

    Rhodopsin, consisting of a retinal chromophore and a protein opsin, is responsible for the first steps in the vision process through a cis to trans photoisomerization, which is completed within 200 fs[1]. Efforts to control the ultrafast dynamics of this molecule have been carried out experimentally[2] as well as through quantum mechanical modeling of nuclear wave packet propagation[3]. We propose a two state model in which the ground electronic Potential Energy Surface (PES) is made up of two adjacent harmonic potentials, representing the cis and trans retinal saddle points, as well as an excited PES, characterized by the Morse potential, which meets the ground PES at a conical intersection. We explore the achievement of a high quantum yield of the trans retinal configuration by varying parameters of the external field and choosing the most adequate shape. Another investigation is presented in which we compare the charge distribution of cis and trans retinal in order to reveal a charge transfer mechanism behind the isomerization of rhodopsin. The results of the Lowdin and Natural Population Analyses demonstrate a significant transfer of charge in and around the isomerization region. [1] RW Schoenlein, LA Peteanu, RA Mathies, CV Shank, Science 254, 412 (1991) [2] VI Prokhorenko, AM Nagy, SA Waschuk, LS Brown, RR Birge, RJD Miller, Science 313, 1257 (2006) [3] S Hahn, G Stock, Chem Phys 259, 297-312 (2000)

  7. PbBr-Based Layered Perovskite Organic-Inorganic Superlattice Having Carbazole Chromophore; Hole-Mobility and Quantum Mechanical Calculation.

    Science.gov (United States)

    Era, Masanao; Yasuda, Takeshi; Mori, Kento; Tomotsu, Norio; Kawano, Naoki; Koshimizu, Masanori; Asai, Keisuke

    2016-04-01

    We have successfully evaluated hole mobility in a spin-coated film of a lead-bromide based layered perovskite having carbazole chromophore-linked ammonium molecules as organic layer by using FET measurement. The values of hole mobility, threshold voltage and on/off ratio at room temperature were evaluated.to.be 1.7 x 10(-6) cm2 V-1 s-1, 27 V and 28 V, respectively. However, the spin-coated films on Si substrates were not so uniform compared with those on fused quartz substrates. To improve the film uniformity, we examined the relationship between substrate temperature during spin-coating and film morphology in the layered perovskite spin-coated films. The mean roughness of the spin-coated films on Si substrates was dependent on the substrate temperature. At 353 K, the mean roughness was minimized and the carrier mobility was enhanced by one order of magnitude; the values of hole mobility and threshold voltage were .estimated to be 3.4 x 10(-5) cm2 V-1 s-1, and 22 V at room temperature in a preliminary FET evaluation, respectively. In addition, we determined a crystal structure of the layered perovskite by X-ray diffraction analysis. To gain a better understanding of the observed hole transports, we conducted quantum mechanical calculations using the obtained crystal structure information. The calculated band structure of the layered organic perovskite showed that the valence band is composed of the organic carbazole layer, which confirms that.the measured hole mobility is mainly derived from the organic part of the layered perovskite. Band and hopping transport mechanisms were discussed by calculating the effective masses and transfer integrals for the 2D periodic system of the organic layer in isolation.

  8. Investigation of chromophore-chromophore interaction by electro-optic measurements, linear dichroism, x-ray scattering, and density-functional calculations

    DEFF Research Database (Denmark)

    Apitz, Dirk; Bertram, R.P.; Benter, N.;

    2005-01-01

    Free-beam interferometry and angle-resolved absorption spectra are used to investigate the linear electro-optic coefficients and the linear dichroism in photoaddressable bis-azo copolymer thin films. From the first- and second order parameters deduced, the chromophore orientation distribution is ...

  9. Synthesis and electrocatalytic water oxidation by electrode-bound helical peptide chromophore-catalyst assemblies.

    Science.gov (United States)

    Ryan, Derek M; Coggins, Michael K; Concepcion, Javier J; Ashford, Dennis L; Fang, Zhen; Alibabaei, Leila; Ma, Da; Meyer, Thomas J; Waters, Marcey L

    2014-08-01

    Artificial photosynthesis based on dye-sensitized photoelectrosynthesis cells requires the assembly of a chromophore and catalyst in close proximity on the surface of a transparent, high band gap oxide semiconductor for integrated light absorption and catalysis. While there are a number of approaches to assemble mixtures of chromophores and catalysts on a surface for use in artificial photosynthesis based on dye-sensitized photoelectrosynthesis cells, the synthesis of discrete surface-bound chromophore-catalyst conjugates is a challenging task with few examples to date. Herein, a versatile synthetic approach and electrochemical characterization of a series of oligoproline-based light-harvesting chromophore-water-oxidation catalyst assemblies is described. This approach combines solid-phase peptide synthesis for systematic variation of the backbone, copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) as an orthogonal approach to install the chromophore, and assembly of the water-oxidation catalyst in the final step. Importantly, the catalyst was found to be incompatible with the conditions both for amide bond formation and for the CuAAC reaction. The modular nature of the synthesis with late-stage assembly of the catalyst allows for systematic variation in the spatial arrangement of light-harvesting chromophore and water-oxidation catalyst and the role of intrastrand distance on chromophore-catalyst assembly properties. Controlled potential electrolysis experiments verified that the surface-bound assemblies function as water-oxidation electrocatalysts, and electrochemical kinetics data demonstrate that the assemblies exhibit greater than 10-fold rate enhancements compared to the homogeneous catalyst alone.

  10. Introduction to electronic analogue computers

    CERN Document Server

    Wass, C A A

    1965-01-01

    Introduction to Electronic Analogue Computers, Second Revised Edition is based on the ideas and experience of a group of workers at the Royal Aircraft Establishment, Farnborough, Hants. This edition is almost entirely the work of Mr. K. C. Garner, of the College of Aeronautics, Cranfield. As various advances have been made in the technology involving electronic analogue computers, this book presents discussions on the said progress, including some acquaintance with the capabilities of electronic circuits and equipment. This text also provides a mathematical background including simple differen

  11. Analogue Methods in Palaeoecology: Using the analogue Package

    Directory of Open Access Journals (Sweden)

    Gavin L. Simpson

    2007-08-01

    Full Text Available Palaeoecology is an important branch of ecology that uses the subfossil remains of organisms preserved in lake, ocean and bog sediments to inform on changes in ecosystems and the environment through time. The analogue package contains functions to perform modern analogue technique (MAT transfer functions, which can be used to predict past changes in the environment, such as climate or lake-water pH from species data. A related technique is that of analogue matching, which is concerned with identifying modern sites that are floristically and faunistically similar to fossil samples. These techniques, and others, are increasingly being used to inform public policy on environmental pollution and conservation practices. These methods and other functionality in analogue are illustrated using the Surface Waters Acidification Project diatom:pH training set and diatom counts on samples of a sediment core from the Round Loch of Glenhead, Galloway, Scotland. The paper is aimed at palaeoecologists who are familiar with the techniques described but not with R.

  12. The terminal phycobilisome emitter, LCM: A light-harvesting pigment with a phytochrome chromophore.

    Science.gov (United States)

    Tang, Kun; Ding, Wen-Long; Höppner, Astrid; Zhao, Cheng; Zhang, Lun; Hontani, Yusaku; Kennis, John T M; Gärtner, Wolfgang; Scheer, Hugo; Zhou, Ming; Zhao, Kai-Hong

    2015-12-29

    Photosynthesis relies on energy transfer from light-harvesting complexes to reaction centers. Phycobilisomes, the light-harvesting antennas in cyanobacteria and red algae, attach to the membrane via the multidomain core-membrane linker, L(CM). The chromophore domain of L(CM) forms a bottleneck for funneling the harvested energy either productively to reaction centers or, in case of light overload, to quenchers like orange carotenoid protein (OCP) that prevent photodamage. The crystal structure of the solubly modified chromophore domain from Nostoc sp. PCC7120 was resolved at 2.2 Å. Although its protein fold is similar to the protein folds of phycobiliproteins, the phycocyanobilin (PCB) chromophore adopts ZZZssa geometry, which is unknown among phycobiliproteins but characteristic for sensory photoreceptors (phytochromes and cyanobacteriochromes). However, chromophore photoisomerization is inhibited in L(CM) by tight packing. The ZZZssa geometry of the chromophore and π-π stacking with a neighboring Trp account for the functionally relevant extreme spectral red shift of L(CM). Exciton coupling is excluded by the large distance between two PCBs in a homodimer and by preservation of the spectral features in monomers. The structure also indicates a distinct flexibility that could be involved in quenching. The conclusions from the crystal structure are supported by femtosecond transient absorption spectra in solution.

  13. Plasmon Resonance Energy Transfer: Coupling between Chromophore Molecules and Metallic Nanoparticles.

    Science.gov (United States)

    Cao, Yue; Xie, Tao; Qian, Ruo-Can; Long, Yi-Tao

    2017-01-01

    Plasmon resonance energy transfer (PRET) from a single metallic nanoparticle to the molecules adsorbed on its surface has attracted more and more attentions in recent years. Here, a molecular beacon (MB)-regulated PRET coupling system composed of gold nanoparticles (GNPs) and chromophore molecules has been designed to study the influence of PRET effect on the scattering spectra of GNPs. In this system, the chromophore molecules are tagged to the 5'-end of MB, which can form a hairpin structure and modified on the surface of GNPs by its thiol-labeled 3'-end. Therefore, the distance between GNPs and chromophore molecules can be adjusted through the open and close of the MB loop. From the peak shift, the PRET interactions of different GNPs-chromophore molecules coupling pairs have been calculated by discrete dipole approximation and the fitting results match well with the experimental data. Therefore, the proposed system has been successfully applied for the analysis of PRET situation between various metallic nanoparticles and chromophore molecules, and provides a useful tool for the potential application in screening the PRET-based nanoplasmonic sensors.

  14. Cooperative TPA enhancement via through-space interactions in organic nanodots built from dipolar chromophores

    Science.gov (United States)

    Robin, Anne-Claire; Parthasarathy, Venkatakrishnan; Pla-Quintana, Anna; Mongin, Olivier; Terenziani, Francesca; Caminade, Anne-Marie; Majoral, Jean-Pierre; Blanchard-Desce, Mireille

    2010-08-01

    Whereas structure-properties relationships have been widely investigated at the molecular level, supramolecular structure-property relationships have been somewhat overlooked. In many cases, interchromophoric interactions are found to be detrimental (in particular in second-order NLO) and a lot of efforts have been devoted to circumvent and control these effects to achieve efficient NLO materials for electrooptics. At opposite, we have implemented a countermainstream route based on the confinement of push-pull chromophores in close proximity within organic nanodots where both their number and relative position/distance are controlled by covalent attachment onto appropriate organic scaffolds. In such multichromophoric organic superstructures (namely covalent nanoclusters), dipole-dipole interactions can be tuned by playing on the internal architecture (topology, number of chromophoric subunits, length of the covalent linkers) and on the nature and properties (polarity, polarizability) of the chromophoric subunits. Following this strategy, we present the investigation of two series of such organic nanoclusters built from push-pull chromophores where through-space interactions are shown to modify both one-photon (OPA) and two-photon absorption (TPA) of each chromophoric subunits leading to cooperative enhancement of TPA properties and improved transparency.

  15. Simulation of femtosecond “double-slit” experiments for a chromophore in a dissipative environment

    Energy Technology Data Exchange (ETDEWEB)

    Gelin, M. F.; Domcke, W. [Department of Chemistry, Technische Universität München, Garching D-85747 (Germany); Tanimura, Y. [Department of Chemistry, Technische Universität München, Garching D-85747 (Germany); Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan)

    2013-12-07

    We performed simulations of the prototypical femtosecond “double-slit” experiment with strong pulsed laser fields for a chromophore in solution. The chromophore is modeled as a system with two electronic levels and a single Franck-Condon active underdamped vibrational mode. All other (intra- and inter-molecular) vibrational modes are accounted for as a thermal bath. The system-bath coupling is treated in a computationally accurate manner using the hierarchy equations of motion approach. The double-slit signal is evaluated numerically exactly without invoking perturbation theory in the matter-field interaction. We show that the strong-pulse double-slit signal consists of a superposition of N-wave-mixing (N = 2, 4, 6…) responses and can be split into population and coherence contributions. The former reveals the dynamics of vibrational wave packets in the ground state and the excited electronic state of the chromophore, while the latter contains information on the dephasing of electronic coherences of the chromophore density matrix. We studied the influence of heat baths with different coupling strengths and memories on the double-slit signal. Our results show that the double-slit experiment performed with strong (nonperturbative) pulses yields substantially more information on the photoinduced dynamics of the chromophore than the weak-pulse experiment, in particular, if the bath-induced dephasings are fast.

  16. Revealing Brown Carbon Chromophores Produced in Reactions of Methylglyoxal with Ammonium Sulfate

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Peng; Laskin, Julia; Nizkorodov, Sergey A.; Laskin, Alexander

    2015-12-15

    Atmospheric brown carbon (BrC) is an important contributor to light absorption and climate forcing by aerosols. Reactions between small water-soluble carbonyls and ammonia or amines have been identified as one of the potential pathways of BrC formation. However, detailed chemical characterization of BrC chromophores has been challenging and their formation mechanisms are still poorly understood. Understanding BrC formation is impeded by the lack of suitable methods which can unravel the variability and complexity of BrC mixtures. This study applies high performance liquid chromatography (HPLC) coupled to photodiode array (PDA) detector and high resolution mass spectrometry (HRMS) to investigate optical properties and chemical composition of individual BrC components produced through reactions of methylglyoxal (MG) and ammonium sulfate (AS), both of which are abundant in the atmospheric environment. A direct relationship between optical properties and chemical composition of 30 major BrC chromophores was established. Nearly all of these chromophores are nitrogen-containing compounds that account for >70% of the overall light absorption by the MG+AS system in the 300-500 nm range. These results suggest that reduced-nitrogen organic compounds formed in reactions between atmospheric carbonyls and ammonia/amines are important BrC chromophores. It is also demonstrated that improved separation of BrC chromophores by HPLC will significantly advance understanding of BrC chemistry.

  17. Photophysics of organometallic platinum(II) derivatives of the diketopyrrolopyrrole chromophore

    KAUST Repository

    Goswami, Subhadip

    2014-12-18

    A pair of diketopyrrolopyrrole (DPP) chromophores that are end-functionalized with platinum containing "auxochromes" were subjected to electrochemical and photophysical study. The chromophores contain either platinum acetylide or ortho-metalated 2-thienylpyridinyl(platinum) end-groups (DPP-Pt(CC) and DPP-Pt(acac), respectively). The ground state redox potentials of the chromophores were determined by solution electrochemistry, and the HOMO and LUMO levels were estimated. The chromophores\\' photophysical properties were characterized by absorption, photoluminescence, and time-resolved absorption spectroscopy on time scales from sub-picoseconds to microseconds. Density functional theory (DFT) computations were performed to understand the molecular orbitals involved in both the singlet and triplet excited state photophysics. The results reveal that in both platinum DPP derivatives the organometallic auxochromes have a significant effect on the chromophores\\' photophysics. The most profound effect is a reduction in the fluorescence yields accompanied by enhanced triplet yields due to spin-orbit coupling induced by the metal centers. The effects are most pronounced in DPP-Pt(acac), indicating that the orthometalated platinum auxochrome is able to induce spin-orbital coupling to a greater extent compared to the platinum acetylide units. (Figure Presented).

  18. Synthesis of Dendrimer Containing Carbazole Unit as a Core Chromophore

    Energy Technology Data Exchange (ETDEWEB)

    Han, Seung Choul; Lee, Jae Wook [Dong-A Univ., Busan (Korea, Republic of); Jin, Sungho [Pusan National Univ., Busan (Korea, Republic of)

    2012-10-15

    Dendrimers, which are prepared by repetition of a given set of reactions using either divergent or convergent strategies, are highly branched and regular macromolecules with well-defined structures and have served as functional objects in nanotechnology and nano-materials science. Following conventional organic small molecules and polymers, dendrimers are now regarded as the third class of materials for use in organic light-emitting diodes (OLEDs) and have attracted much attention due to their distinguished properties. Dendrimers contain three distinct structural parts that are the core, end-groups, and branched units connecting core and periphery. For light-emitting dendrimers, the core is usually selected as the luminescent chromophore, and the dendrons and their periphery are charge transporting units and can also tune the solubility. In contrast to linear polymers, dendrimers are sphere-like with dimensions of the order of nanometers depending on the generation number. By careful structural design, dendrimers combine the potential advantages of both small molecules and polymers. Therefore, the innovative strategy different from conventional convergent and divergent routes has been required to simplify dendrimer synthesis. Recent solid chemistry is the click chemistry which is the copper-catalyzed 1,3-dipolar cycloaddition reaction between alkyne and azide developed by Sharpless and Tornφe. This reaction has many advantages: very high yields, mild and simple reaction conditions, oxygen and water tolerance, and easy isolation of product. This reaction is clearly a breakthrough in the synthesis of dendrimers and dendritic and polymer materials. We have developed the fusion and stitching methods for the synthesis of various dendrimers using click chemistry between an alkyne and an azide. Overall, this method was found to be a straightforward strategy for the synthesis of triazole-based dendrimers. Taking advantage of this fact, herein we report a feasible route

  19. A Diabatic Three-State Representation of Photoisomerization in the Green Fluorescent Protein Chromophore

    CERN Document Server

    Olsen, Seth

    2009-01-01

    We give a quantum chemical description of bridge photoisomerization reaction of green fluorescent protein (GFP) chromophores using a representation over three diabatic states. Bridge photoisomerization leads to non-radiative decay, and competes with fluorescence in these systems. In the protein, this pathway is suppressed, leading to fluorescence. Understanding the electronic structure of the photoisomerization is a prerequisite to understanding how the protein suppresses this pathway and preserves the emitting state of the chromophore. We present a solution to the state-averaged complete active space problem, which is spanned at convergence by three fragment-localized orbitals. We generate the diabatic-state representation by applying a block diagonalization transformation to the Hamiltonian calculated for the anionic chromophore model HBDI with multi-reference, multi-state perturbation theory. The diabatic states that emerge are charge-localized structures with a natural valence-bond interpretation. At plan...

  20. Offshore Substrate

    Data.gov (United States)

    California Department of Resources — This shapefile displays the distribution of substrate types from Pt. Arena to Pt. Sal in central/northern California. Originally this data consisted of seven paper...

  1. Measuring Mental Imagery with Visual Analogue Scales.

    Science.gov (United States)

    Quilter, Shawn M.; Band, Jennie P.; Miller, Gary M.

    1999-01-01

    Investigates some of the psychometric characteristics of the results from visual-analogue scales used to measure mental imagery. Reports that the scores from visual-analogue scales are positively related to scores from longer pencil-and-paper measures of mental imagery. Implications and limitations for the use of visual-analogue scales to measure…

  2. Assembly of synthetic locked chromophores with Agrobacterium phytochromes Agp1 and Agp2

    OpenAIRE

    Inomata, Katsuhiko; Noack, Steffi; Hammam, Mostafa A. S.; Khawn, Htoi; Kinoshita, Hideki

    2006-01-01

    Phytochromes are photoreceptors with a bilin chromophore in which light triggers the conversion between the red-absorbing form Pr and the far-red-absorbing form Pfr. Agrobacterium tumefaciens has two phytochromes, Agp1 and Agp2, with antagonistic properties: in darkness, Agp1 converts slowly from Pfr to Pr, whereas Agp2 converts slowly from Pr to Pfr. In a previous study, we have assembled Agp1 with synthetic locked chromophores 15Za, 15Zs, 15Ea, and 15Es in which the C15=C16 double bond is f...

  3. Synthesis,structure and nonlinear optical properties of two novel two-photon absorption chromophores

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Two triphenylamine-based derivatives that can be used as two-photon absorption chromophore,tris{4-[4-(3-trifluoromethyl-3-oxopanoyl)]phenyl}amine (1) and tris{4-[4-(3-phenyl-3-oxopanoyl)] phenyl} amine (2) were successfully synthesized and fully characterized by elemental analysis,IR,1H NMR and MS. The single crystal X-ray diffraction analysis showed that the molecules possess D-(π-A)3 structures. One-and two-photon absorption and fluorescence in various solvents were experimentally investigated. A data recording experiment proved the potential application of these chromophores.

  4. Chromopeptides from phytochrome. The structure and linkage of the PR form of the phytochrome chromophore

    Energy Technology Data Exchange (ETDEWEB)

    Lagarias, J. Clark [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States); Rapoport, Henry [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States)

    1980-07-01

    The isolation and chromatographic purification of chromophore-containing peptides from the PR form of phytochrome treated with pepsin and thermolysin are described. From the amino acid sequence and 1H NMR spectral analysis of phytochromobiliundeca peptide (2), the structure of the PR phytochrome chromophore and the nature of the thioether linkage joining pigment to peptide have been established. Furthermore, confirmatory evidence was obtained from similar analysis of phytochromobilioctapeptide (3). The implications of this structural assignment with respect to the mechanism of the PR to PFR phototransformation are considered.

  5. Absorption tuning of the green fluorescent protein chromophore: synthesis and studies of model compounds

    DEFF Research Database (Denmark)

    Brøndsted Nielsen, Mogens; Andersen, Lars Henrik; Rinza, Tomás Rocha

    2011-01-01

    The green fluorescent protein (GFP) chromophore is a heterocyclic compound containing a p-hydroxybenzylidine attached to an imidazol-5(4H)-one ring. This review covers the synthesis of a variety of model systems for elucidating the intrinsic optical properties of the chromophore in the gas phase...... and its response in particular to hydrogen bond interactions. The overall goal is to understand how the protein binding pocket influences the absorption behavior, and the current status of our ongoing efforts is presented....

  6. Photochemical stability of nonlinear optical chromophores in polymeric and crystalline materials.

    Science.gov (United States)

    Rezzonico, Daniele; Kwon, Seong-Ji; Figi, Harry; Kwon, O-Pil; Jazbinsek, Mojca; Günter, Peter

    2008-03-28

    We compare the photochemical stability of the nonlinear optical chromophore configurationally locked polyene 2-{3-[2-(4-dimethylaminophenyl)vinyl]-5,5-dimethylcyclohex-2-enylidene} malononitrile (DAT2) embedded in a polymeric matrix and in a single-crystalline configuration. The results show that, under resonant light excitations, the polymeric compound degrades through an indirect process, while the DAT2 crystal follows a slow direct process. We show that chromophores in a crystalline environment exhibit three orders of magnitude better photostability as compared to guest-host polymer composites.

  7. Comprehensive studies on an overall proton transfer cycle of the ortho-green fluorescent protein chromophore.

    Science.gov (United States)

    Hsieh, Cheng-Chih; Chou, Pi-Tai; Shih, Chun-Wei; Chuang, Wei-Ti; Chung, Min-Wen; Lee, Junghwa; Joo, Taiha

    2011-03-09

    Initiated by excited-state intramolecular proton transfer (ESIPT) reaction, an overall reaction cycle of 4-(2-hydroxybenzylidene)-1,2-dimethyl-1H-imidazol-5(4H)-one (o-HBDI), an analogue of the core chromophore of the green fluorescent protein (GFP), has been investigated. In contrast to the native GFP core, 4-(4-hydroxybenzylidene)-1,2-dimethyl-1H-imidazol-5(4H)-one (p-HBDI), which requires hydrogen-bonding relay to accomplish proton transfer in vivo, o-HBDI possesses a seven-membered-ring intramolecular hydrogen bond and thus provides an ideal system for mimicking an intrinsic proton-transfer reaction. Upon excitation, ESIPT takes place in o-HBDI, resulting in a ∼600 nm proton-transfer tautomer emission. The o-HBDI tautomer emission, resolved by fluorescence upconversion, is comprised of an instantaneous rise to a few hundred femtosecond oscillation in the early relaxation stage. Frequency analysis derived from ultrashort pulse gives two low-frequency vibrations at 115 and 236 cm(-1), corresponding to skeletal deformation motions associated with the hydrogen bond. The results further conclude that ESIPT in o-HBDI is essentially triggered by low-frequency motions and may be barrierless along the reaction coordinate. Femtosecond UV/vis transient absorption spectra also provide supplementary evidence for the structural evolution during the reaction. In CH(3)CN, an instant rise of a 530 nm transient is resolved, which then undergoes 7.8 ps decay, accompanied by the growth of a rather long-lived 580 nm transient species. It is thus concluded that following ESIPT the cis-proton transfer isomer undergoes cis-trans-isomerization. The results of viscosity-dependent dynamics are in favor of the one-bond-flip mechanism, which is in contrast to the volume-conserving isomerization behavior for cis-stilbene and p-HBDI. Further confirmation is given by the picosecond-femtosecond transient IR absorption spectra, where several new and long-lived IR bands in the range of 1400

  8. Neuronal Analogues of Conditioning Paradigms

    Science.gov (United States)

    1984-04-24

    Although the mechanisms of interneuronal communication have been well established, the changes underlying most forms of learning have thus far eluded...stimulating electrodes on one of the connectives was adjusted so as to produce a small excitatory postsynaptic potential ( EPSP ) in the impaled cell...two stimuli would constitute a neuronal analogue of conditioning by producing an increased EPSP in response to the test stimulus alone. If so, then

  9. Novel acetylcholine and carbamoylcholine analogues

    DEFF Research Database (Denmark)

    Hansen, Camilla Petrycer; Jensen, Anders Asbjørn; Christensen, Jeppe K.;

    2008-01-01

    A series of carbamoylcholine and acetylcholine analogues were synthesized and characterized pharmacologically at neuronal nicotinic acetylcholine receptors (nAChRs). Several of the compounds displayed low nanomolar binding affinities to the alpha 4beta 2 nAChR and pronounced selectivity for this ......A series of carbamoylcholine and acetylcholine analogues were synthesized and characterized pharmacologically at neuronal nicotinic acetylcholine receptors (nAChRs). Several of the compounds displayed low nanomolar binding affinities to the alpha 4beta 2 nAChR and pronounced selectivity...... for this subtype over alpha 3beta 4, alpha 4beta 4, and alpha 7 nAChRs. The high nAChR activity of carbamoylcholine analogue 5d was found to reside in its R-enantiomer, a characteristic most likely true for all other compounds in the series. Interestingly, the pronounced alpha 4beta 2 selectivities exhibited......AChR agonists published to date. Ligand-protein docking experiments using homology models of the amino-terminal domains of alpha 4beta 2 and alpha 3beta 4 nAChRs identified residues Val111(beta 2)/Ile113(beta 4), Phe119(beta 2)/Gln121(beta 4), and Thr155(alpha 4)/Ser150(alpha 3) as possible key determinants...

  10. Spontaneous activation of visual pigments in relation to openness/closedness of chromophore-binding pocket

    Science.gov (United States)

    Yue, Wendy Wing Sze; Frederiksen, Rikard; Ren, Xiaozhi; Luo, Dong-Gen; Yamashita, Takahiro; Shichida, Yoshinori; Cornwall, M Carter; Yau, King-Wai

    2017-01-01

    Visual pigments can be spontaneously activated by internal thermal energy, generating noise that interferes with real-light detection. Recently, we developed a physicochemical theory that successfully predicts the rate of spontaneous activity of representative rod and cone pigments from their peak-absorption wavelength (λmax), with pigments having longer λmax being noisier. Interestingly, cone pigments may generally be ~25 fold noisier than rod pigments of the same λmax, possibly ascribed to an ‘open’ chromophore-binding pocket in cone pigments defined by the capability of chromophore-exchange in darkness. Here, we show in mice that the λmax-dependence of pigment noise could be extended even to a mutant pigment, E122Q-rhodopsin. Moreover, although E122Q-rhodopsin shows some cone-pigment-like characteristics, its noise remained quantitatively predictable by the ‘non-open’ nature of its chromophore-binding pocket as in wild-type rhodopsin. The openness/closedness of the chromophore-binding pocket is potentially a useful indicator of whether a pigment is intended for detecting dim or bright light. DOI: http://dx.doi.org/10.7554/eLife.18492.001 PMID:28186874

  11. Production of Chromophoric Dissolved Organic Matter from Mangrove Leaf Litter and Floating Sargassum Colonies

    Science.gov (United States)

    Chromophoric dissolved organic matter (CDOM) strongly absorbs solar radiation in the blue-green and serves as the primary attenuator of water column ultraviolet radiation (UV-R). CDOM interferes with remote sensing of ocean chlorophyll and can control UV-R-induced damage to light...

  12. Design, synthesis and characterization of novel nonlinear optical chromophores for electro-optical applications

    Science.gov (United States)

    Liu, Feng

    This dissertation involves the design, synthesis and characterization of second order nonlinear optical chromophores for electro-optic applications. The design concept, that poling efficiency and macroscopic nonlinearities can be improved by modifying a chromophore's shape, has been explored. Chapter 1 gives an introduction into theoretical background of nonlinear optics and electro-optic phenomenon in organic molecules and poled polymers. Chapter 2 involves the design and synthesis of GLD-2 and GLD-3 chromophores, both with bulky substituents on the ring-fused bridge. The optical studies and HRS measurement show that the two alkyl groups on the bridge blueshift the lambdamax in chloroform by 20 nm and decrease the beta values. DSC and TGA thermal analysis show Td of GLD-2 and GLD-3 over 240°C. The maximum achievable r33 of GLD-2/PMMA is 61 pm/V, compared to the 92.4 pm/V of GLD-1/PMMA. But GLD-2/APC shows r33 of 45.2pm/V, higher than GLD-1/APC due to the improved compatibility with APC. The optical loss of 13 wt% GLD-2/PMMA at 1.55mum is 1.4 dB compared to the 2.3 dB of 17 wt% GLD-1/PMMA. Optical loss studies prove that adding two bulky substituents on bridge help attenuate electrostatic interactions. GLD-3 show deteriorated solubility in common used organic solvents, probably due to the combination of two TBDMS and two lengthy alkyl groups. Chapter 3 presents synthesis of thiophene-based chromophores with variously positioned TBDMS groups. The optical studies of these chromophores show one TBDMSO substitution on the thiophene bridge yields little influence on the lambda max in chloroform. FTCDS chromophore with two TBDMS groups, one on donor and one on thiophene bridge, shows to be the best structure with regards the thermal stability and achievable maximum EO coefficient value, 65.9 pm/V, at only 24 wt% loading density at 1.3 mum. Chapter 4 deals with three novel bridges for NLO chromophores. Synthetic methodologies of the diketone precursor of rigidified

  13. Aromatic A-ring analogues of orobanchol, new germination stimulants for seeds of parasitic weeds

    NARCIS (Netherlands)

    Malik, H.; Kohlen, W.; Jamil, M.; Rutjes, F.P.J.T.; Zwanenburg, B.

    2011-01-01

    Strigolactones are signaling compounds in plants of increasing importance. In this paper the focus is on their activity as germinating agents for seeds of parasitic weeds. The syntheses of aromatic A-ring analogues of the germination stimulant orobanchol have been described. Starting substrate is th

  14. Simultaneous control of emission localization and two-photon absorption efficiency in dissymmetrical chromophores

    Energy Technology Data Exchange (ETDEWEB)

    Tretiak, Sergei [Los Alamos National Laboratory

    2009-01-01

    The aim of the present work is to demonstrate that combined spectral tuning of fluorescence and two-photon absorption (TPA) properties of multipolar chromophores can be achieved by introduction of slight electronic chemical dissymmetry. In that perspective, two novel series of structurally related chromophores have been designed and studied: a first series based on rod-like quadrupolar chromophores bearing different electron-donating (D) end groups and a second series based on three-branched octupolar chromophores built from a trigonal donating moiety and bearing various acceptor (A) peripheral groups. The influence of the electronic dissymmetry is investigated by combined experimental and theoretical studies of the linear and nonlinear optical properties of dissymmetric chromophores compared to their symmetrical counterparts. In both types of systems (i.e. quadrupoles and octupoles) experiments and theory reveal that excitation is essentially delocalized and that excitation involves synchronized charge redistribution between the different D and A moieties within the multipolar structure (i.e. concerted intramolecular charge transfer). In contrast, the emission stems only from a particular dipolar subunit bearing the strongest D or A moieties due to fast excitation localization after excitation prior to emission. Hence control of emission characteristics (polarization and emission spectrum) in addition to localization can be achieved by controlled introduction of electronic dissymmetry (i.e. replacement of one of the D or A end-groups by a slightly stronger D{prime} or A{prime} units). Interestingly dissymmetrical functionalization of both quadrupolar and octupolar compounds does not lead to significant loss in TPA responses and can even be beneficial due to the spectral broadening and peak position tuning that it allows. This study thus reveals an original molecular engineering route strategy allowing major TPA enhancement in multipolar structures due to concerted

  15. Triplet excited state properties in variable gap π-conjugated donor–acceptor–donor chromophores

    KAUST Repository

    Cekli, Seda

    2016-02-12

    A series of variable band-gap donor–acceptor–donor (DAD) chromophores capped with platinum(II) acetylide units has been synthesized and fully characterized by electrochemical and photophysical methods, with particular emphasis placed on probing triplet excited state properties. A counter-intuitive trend of increasing fluorescence quantum efficiency and lifetime with decreasing excited state energy (optical gap) is observed across the series of DAD chromophores. Careful study of the excited state dynamics, including triplet yields (as inferred from singlet oxygen sensitization), reveals that the underlying origin of the unusual trend in the fluorescence parameters is that the singlet–triplet intersystem crossing rate and yield decrease with decreasing optical gap. It is concluded that the rate of intersystem crossing decreases as the LUMO is increasingly localized on the acceptor unit in the DAD chromophore, and this result is interpreted as arising because the extent of spin–orbit coupling induced by the platinum heavy metal centers decreases as the LUMO is more localized on the acceptor. In addition to the trend in intersystem crossing, the results show that the triplet decay rates follow the Energy Gap Law correlation over a 1.8 eV range of triplet energy and 1000-fold range of triplet decay rates. Finally, femtosecond transient absorption studies for the DAD chromophores reveals a strong absorption in the near-infrared region which is attributed to the singlet excited state. This spectral band appears to be general for DAD chromophores, and may be a signature of the charge transfer (CT) singlet excited state.

  16. EPOXY-BASED AZO POLYMERS WITH HIGH CHROMOPHORE DENSITY:SYNTHESIS, CHARACTERIZATION AND PHOTOINDUCED BIREFRINGENCE

    Institute of Scientific and Technical Information of China (English)

    Xiao-lin Wang; Xiao-gong Wang

    2012-01-01

    Three epoxy-based azo polymers (PEP-AZ-C1,PEP-AZ-CN and PEP-AZ-NT) with high chromophore density were synthesized by using post-polymerization azo-coupling reactions between epoxy-bascd precursor polymer (PEP-AN)and diazonium salts of 4-chloroaniline,4-aminobenzonitrile and 4-nitroaniline,respectively.The structures and properties of the azo polymers were characterized by using 1H-NMR,FT-IR,UV-Vis and thermal analyses.The photoinduced birefringence of the azo polymers was studied by irradiating spin-coated films of the polymers with laser beam at three different wavelengths (488,532,and 589 nm).The results indicate that the photoinduced birefringence of the azo polymers is related with the electron-withdrawing group on azo chromophores and the excitation wavelength.The excitation wavelength that can cause the efficient responses is determined by the absorption band positions of the azo chromophores,which are mainly affected by the electron-withdrawing group on the chromophores.Therefore,the azo polymers containing chromophores with different electron-withdrawing groups show different responsive behavior to the irradiation light at different wavelengths.When irradiated with 488 nm light,PEP-AZ-Cl shows the shortest time to reach the saturated birefringence but with the lowest saturation birefringence level compared with the other two azo polymers.When irradiated with 532 nm light,PEP-AZ-CN shows the shortest time to reach the saturated birefringence.When irradiated with 532 and 589 nm light,PEP-AZ-NT shows the highest saturation birefringence level.

  17. Theoretical description of protein field effects on electronic excitations of biological chromophores

    Science.gov (United States)

    Varsano, Daniele; Caprasecca, Stefano; Coccia, Emanuele

    2017-01-01

    Photoinitiated phenomena play a crucial role in many living organisms. Plants, algae, and bacteria absorb sunlight to perform photosynthesis, and convert water and carbon dioxide into molecular oxygen and carbohydrates, thus forming the basis for life on Earth. The vision of vertebrates is accomplished in the eye by a protein called rhodopsin, which upon photon absorption performs an ultrafast isomerisation of the retinal chromophore, triggering the signal cascade. Many other biological functions start with the photoexcitation of a protein-embedded pigment, followed by complex processes comprising, for example, electron or excitation energy transfer in photosynthetic complexes. The optical properties of chromophores in living systems are strongly dependent on the interaction with the surrounding environment (nearby protein residues, membrane, water), and the complexity of such interplay is, in most cases, at the origin of the functional diversity of the photoactive proteins. The specific interactions with the environment often lead to a significant shift of the chromophore excitation energies, compared with their absorption in solution or gas phase. The investigation of the optical response of chromophores is generally not straightforward, from both experimental and theoretical standpoints; this is due to the difficulty in understanding diverse behaviours and effects, occurring at different scales, with a single technique. In particular, the role played by ab initio calculations in assisting and guiding experiments, as well as in understanding the physics of photoactive proteins, is fundamental. At the same time, owing to the large size of the systems, more approximate strategies which take into account the environmental effects on the absorption spectra are also of paramount importance. Here we review the recent advances in the first-principle description of electronic and optical properties of biological chromophores embedded in a protein environment. We show

  18. Synthesis of a Nitro Analogue of Plakoric Acid

    Institute of Scientific and Technical Information of China (English)

    ZHANG,Qi; JIN,Hong-Xia; LIU,He-Hua; WU,Yi-Kang

    2006-01-01

    Synthesis of a nitro analogue of plakoric acid is presented. The peroxy bond was incorporated into the substrate structure through a boron trifluoride etherate catalyzed methoxy-hydroperoxy group partial exchange reaction in djethyl ether with urea-hydrogen peroxide complex (UHP, a commercially available solid reagent) as the source of the hydrogen peroxide. Under the given conditions, only one of the two methoxyl groups underwent the MeO-OOH exchange and the resulting hydroperoxy hemiketal proceeded directly to the end product through an intramolecular Michael addition of the hydroperoxyl group to the nitro group activated carbon-carbon double bond.

  19. Chromophore fluorination enhances crystallization and stability of soluble anthradithiophene semiconductors.

    Science.gov (United States)

    Subramanian, Sankar; Park, Sung Kyu; Parkin, Sean R; Podzorov, Vitaly; Jackson, Thomas N; Anthony, John E

    2008-03-05

    We report dramatic improvements in the stability and crystallinity arising from partial fluorination of soluble anthradithiophene derivatives. These fluorinated materials still behave as p-type semiconductors but with dramatic increases in thermal and photostability compared to the non-fluorinated derivatives. The triethylsilyl-substituted material forms highly crystalline films even from spin-cast solutions, leading to devices with maximum hole mobility greater than 1.0 cm(2)/V s. In contrast, the triisopropylsilyl derivative forms large, high-quality crystals that could serve as the substrate for transistor fabrication. For this compound, mobility as high as 0.1 cm(2)/V s was measured on the free-standing crystal.

  20. Donor-Acceptor Chromophores based on Acetylenic Scaffolds and Indenofluorenes

    DEFF Research Database (Denmark)

    Christensen, Mikkel Andreas

    in conjugation with a nitrobenzene unit. Five nitrophenols were synthesized with different π-bridges covering the features of cross-conjugation, linear conjugation, planarity, and non-planarity. I was hoping to elucidate the intrinsic properties of the π-bridges via comparison of the charge-transfer absorptions......-electron events and was fully reversible. This made it possible to prepare the singly oxidized compound D+-π-D by electrolysis. This species showed two charge-transfer absorptions in the near infra-red region. One of these appeared to arise from a complex between a neutral molecule and the radical cation (a mixed...... cross-coupling. The reactivity of chloroalkynes was compared to that of Sonogashira substrates and the chloroalkynes turned out to react as fast as an aryl iodide. Some of the couplings gave reductive homo-coupling of the chloroalkyne as a byproducts. This was avoided by using a large copper...

  1. Enhanced light-harvesting capacity by micellar assembly of free accessory chromophores and LH1-like antennas.

    Science.gov (United States)

    Harris, Michelle A; Sahin, Tuba; Jiang, Jianbing; Vairaprakash, Pothiappan; Parkes-Loach, Pamela S; Niedzwiedzki, Dariusz M; Kirmaier, Christine; Loach, Paul A; Bocian, David F; Holten, Dewey; Lindsey, Jonathan S

    2014-01-01

    Biohybrid light-harvesting antennas are an emerging platform technology with versatile tailorability for solar-energy conversion. These systems combine the proven peptide scaffold unit utilized for light harvesting by purple photosynthetic bacteria with attached synthetic chromophores to extend solar coverage beyond that of the natural systems. Herein, synthetic unattached chromophores are employed that partition into the organized milieu (e.g. detergent micelles) that house the LH1-like biohybrid architectures. The synthetic chromophores include a hydrophobic boron-dipyrrin dye (A1) and an amphiphilic bacteriochlorin (A2), which transfer energy with reasonable efficiency to the bacteriochlorophyll acceptor array (B875) of the LH1-like cyclic oligomers. The energy-transfer efficiencies are markedly increased upon covalent attachment of a bacteriochlorin (B1 or B2) to the peptide scaffold, where the latter likely acts as an energy-transfer relay site for the (potentially diffusing) free chromophores. The efficiencies are consistent with a Förster (through-space) mechanism for energy transfer. The overall energy-transfer efficiency from the free chromophores via the relay to the target site can approach those obtained previously by relay-assisted energy transfer from chromophores attached at distant sites on the peptides. Thus, the use of free accessory chromophores affords a simple design to enhance the overall light-harvesting capacity of biohybrid LH1-like architectures.

  2. Development and Experimental Study of Phantoms for Mapping Skin Chromophores

    Science.gov (United States)

    Silapetere, A.; Spigulis, J.; Saknite, I.

    2014-06-01

    Skin chromophore phantoms are widely used for better understanding of the light interaction with tissue and for calibration of skin diagnostic imaging techniques. In this work, different phantoms were examined and compared in order to find biologically equivalent substances that are the most promising for this purpose. For mimicking the skin medium and layered structure, a fibrin matrix with epidermal and dermal cell inclusion was used. Synthesized bilirubin, red blood cells and nigrosin were taken as absorbers. For spectral analysis of the developed phantoms a computer-aided multispectral imaging system Nuance 2.4 (Cambridge Research & Instrumentation, Inc., USA) was used. In this study, skin phantoms were created using such substances as bilirubin, melanin, haemoglobin and nigrosin Mūsdienās multispektrālās attēlošanas iekārtas izmanto ādas parametru un fizioloģisko procesu aprakstīšanai gan pētniecības, gan diagnostikas nolūkiem. Iekārtu darbības uzlabošanai ir nepieciešams labāk saprast gaismas mijiedarbību ar audiem, kā arī veikt šo iekārtu kalibrēšanu ar ādas maketu. Redzamā un tuvā infrasarkanā optiskā diapazona spektroskopijā ir svarīgi ādas maketi, kas simulē audu slāņaino struktūru un ķīmiskās īpašības, kā arī maketi, kas ir bioloģiski līdzvērtīgi. Šajā pētījumā tika izveidots ādas makets no bioloģiskām un ķīmiski sintezētām struktūrām. Ādas maketa izveidei tika izmantota fibrīna matrica ar dermālo un epidermālo šūnu piejaukumu, lai imitētu ādas slāņaino struktūru. Fibrīna matrica tiek veidota no 0,47 ml asins plazmas, 0,4 ml fizioloģiskā šķīduma, 0,8 μl treneksāmskābes un 89,4 μl kalcija glukanāta. Izveidoto matricu ievieto šūnu inkubatorā, lai tā polimerizētos. Nākošais slānis tiek veidots ar dermālo šūnu piejaukumu (180-270 šūnas), un pēdējais fibrīna matriksa slānis tiek veidots ar epidermālo šūnu piejaukumu (270 šūnas) un šūnu aug

  3. Ecstasy analogues found in cacti.

    Science.gov (United States)

    Bruhn, Jan G; El-Seedi, Hesham R; Stephanson, Nikolai; Beck, Olof; Shulgin, Alexander T

    2008-06-01

    Human interest in psychoactive phenethylamines is known from the use of mescaline-containing cacti and designer drugs such as Ecstasy. From the alkaloid composition of cacti we hypothesized that substances resembling Ecstasy might occur naturally. In this article we show that lophophine, homopiperonylamine and lobivine are new minor constituents of two cactus species, Lophophora williamsii (peyote) and Trichocereus pachanoi (San Pedro). This is the first report of putatively psychoactive phenethylamines besides mescaline in these cacti. A search for further biosynthetic analogues may provide new insights into the structure-activity relationships of mescaline. An intriguing question is whether the new natural compounds can be called "designer drugs."

  4. Antimicrobial evaluation of mangiferin analogues

    Directory of Open Access Journals (Sweden)

    Singh S

    2009-01-01

    Full Text Available The naturally occurring xanthone glycoside mangiferin has been isolated by column chromatography from the ethanol extract of stem bark of Mangifera indica. Mangiferin was further converted to 5-(N-phenylaminomethylenomangiferin, 5-(N-p-chlorophenylaminomethyleno mangiferin, 5-(N-2-methylphenylaminomethyleno mangiferin, 5-(N-p-methoxyphenylaminomethyleno mangiferin, 5-(N,N-diphenylaminomethyleno mangiferin, 5-(N--napthylaminomethyleno mangiferin and 5-(N-4-methylphenylaminomethyleno mangiferin. Mangiferin and its analogues were characterized by melting point and R f value determination and through spectral technique like UV, IR, and NMR spectral analysis. The synthesized compounds were screened for antimicrobial activity.

  5. Antimicrobial Evaluation of Mangiferin Analogues

    Science.gov (United States)

    Singh, S. K.; Kumar, Y.; Kumar, S. Sadish; Sharma, V. K.; Dua, K.; Samad, A.

    2009-01-01

    The naturally occurring xanthone glycoside mangiferin has been isolated by column chromatography from the ethanol extract of stem bark of Mangifera indica. Mangiferin was further converted to 5-(N-phenylaminomethyleno)mangiferin, 5-(N-p-chlorophenylaminomethyleno) mangiferin, 5-(N-2-methylphenylaminomethyleno) mangiferin, 5-(N-p-methoxyphenylaminomethyleno) mangiferin, 5-(N, N-diphenylaminomethyleno) mangiferin, 5-(N--napthylaminomethyleno) mangiferin and 5-(N-4-methylphenylaminomethyleno) mangiferin. Mangiferin and its analogues were characterized by melting point and Rf value determination and through spectral technique like UV, IR, and NMR spectral analysis. The synthesized compounds were screened for antimicrobial activity. PMID:20490307

  6. Effects of chromophore concentration and film thickness on thermo-optic properties of electro-optic fluorinated polyimide films

    Institute of Scientific and Technical Information of China (English)

    Hongxiang Song; Chengxun Wu

    2007-01-01

    Electro-optic (EO) effect and thermo-optic (TO) effect are jointly considered on the basis of field-induced and temperature-affected perturbations of the operating point in waveguide components. TO coefficients of EO fluorinated polyimide films with side-chain azobenzene chromophore were measured by attenuatedtotal-reflection (ATR) technique at different temperatures with TE- and TM-polarized lights, respectively.It is found that the absolute values of TO coefficients increase with the increments of both chromophore concentration and film thickness, but the polarization dependence of TO coefficients increases with the increment of chromophore concentration and decreases with the increment of film thickness.

  7. A graphical approach to analogue behavioural modelling

    OpenAIRE

    Moser, Vincent; Nussbaum, Pascal; Amann, Hans-Peter; Astier, Luc; Pellandini, Fausto

    2007-01-01

    In order to master the growing complexity of analogue electronic systems, modelling and simulation of analogue hardware at various levels is absolutely necessary. This paper presents an original modelling method based on the graphical description of analogue electronic functional blocks. This method is intended to be automated and integrated into a design framework: specialists create behavioural models of existing functional blocks, that can then be used through high-level selection and spec...

  8. What Can We Learn From Analogue Experiments?

    CERN Document Server

    Thebault, Karim P Y

    2016-01-01

    In 1981 Unruh proposed that fluid mechanical experiments could be used to probe key aspects of the quantum phenomenology of black holes. In particular, he claimed that an analogue to Hawking radiation could be created within a fluid mechanical `dumb hole', with the event horizon replaced by a sonic horizon. Since then an entire sub-field of `analogue gravity' has been created. In 2016 Steinhauer reported the experimental observation of quantum Hawking radiation and its entanglement in a Bose-Einstein condensate analogue black hole. What can we learn from such analogue experiments? In particular, in what sense can they provide evidence of novel phenomena such as black hole Hawking radiation?

  9. Synthesis and antioxidant activity of peptide-based ebselen analogues.

    Science.gov (United States)

    Satheeshkumar, Kandhan; Mugesh, Govindasamy

    2011-04-18

    A series of di- and tripeptide-based ebselen analogues has been synthesized. The compounds were characterized by (1)H, (13)C, and (77)Se NMR spectroscopy and mass spectral techniques. The glutathione peroxidase (GPx)-like antioxidant activity has been studied by using H(2)O(2) , tert-butyl hydroperoxide (tBuOOH), and cumene hydroperoxide (Cum-OOH) as substrates, and glutathione (GSH) as a cosubstrate. Although all the peptide-based compounds have a selenazole ring similar to that of ebselen, the GPx activity of these compounds highly depends on the nature of the peptide moiety attached to the nitrogen atom of the selenazole ring. It was observed that the introduction of a phenylalanine (Phe) amino acid residue in the N-terminal reduces the activity in all three peroxide systems. On the other hand, the introduction of aliphatic amino acid residues such as valine (Val) significantly enhances the GPx activity of the ebselen analogues. The difference in the catalytic activity of dipeptide-based ebselen derivatives can be ascribed mainly to the change in the reactivity of these compounds toward GSH and peroxide. Although the presence of the Val-Ala-CO(2) Me moiety facilitates the formation of a catalytically active selenol species, the reaction of ebselen analogues that has a Phe-Ile-CO(2) Me residue with GSH does not generate the corresponding selenol. To understand the antioxidant activity of the peptide-based ebselen analogues in the absence of GSH, these compounds were studied for their ability to inhibit peroxynitrite (PN)-mediated nitration of bovine serum albumin (BSA) and oxidation of dihydrorhodamine 123. In contrast to the GPx activity, the PN-scavenging activity of the Phe-based peptide analogues was found to be comparable to that of the Val-based compounds. However, the introduction of an additional Phe residue to the ebselen analogue that had a Val-Ala dipeptide significantly reduced the potency of the parent compound in PN-mediated nitration.

  10. Luminescent Polymers Containing Unconventional Chromophores%含非典型性生色团的发光聚合物

    Institute of Scientific and Technical Information of China (English)

    黄田; 汪昭旸; 秦安军; 孙景志; 唐本忠

    2013-01-01

    Luminescent polymers are referred to as conjugated polymers,which are constructed by π-aromatic building blocks functioning as emitting units.But in recent years,it has been found that a few kinds of polymers only containing auxochromophores or unconventional chromophores such as aliphatic tertiary amine,carbonyl,ester,and amide demonstrate strong luminescence under proper conditions.Poly(amido amine) (PAMAM) dendrimers and hyperbranched poly(amido amine)s are the first reported and most investigated luminescent polymers containing unconventional chromophores.Lately,this kind of polymers have been extended to hyperbranched poly(amino ester)s (hb-PAEs),hyperbranched poly(ether amide)s (hb-PEAs),and polyurea dendrimers (PUREs) containing tertiary amine moieties.The luminogen of PAMAMs,hb-PAEs,hb-PEAs and PUREs is associated with the N-branched tertiary amine moiety and the oxidation of the tertiary amine is assigned to the emitting source.Meanwhile,some distinct polymers had been also reported to be luminescent.Poly[(maleic anhydride)-alt-(vinyl acetate)],polyisobutene succinic anhydrides,glycodynamer analogues of poly(acrylhydrazone)s and multiblock polymer derived by poly(trithiocarbonate) mediated reversible addition-fragmentation chain transfer (RAFT) polymerization of N-isopropyl-acrylamide.A common feature of these polymers is that only carbonyl and ester groups rather than tertiary amine are involved in the polymer structure.Aggregation of multiple carbonyl groups induced emission is usually adopted to explain the mechanism of the emission,and the interaction between carbonyl and phenyl groups was also used to explain the unconventional emission.%发光聚合物一般是由具有大π电子系统的共轭基元作为发光单元,通过共价键连接而成的高分子.近年来,研究者发现:另一类仅含有脂肪胺、羰基、酯基、酰胺等传统意义上的助色团的聚合物在适当条件下也能发射强的荧光.树枝状聚酰胺胺(PAMAM)

  11. A photoactive isoprenoid diphosphate analogue containing a stable phosphonate linkage: synthesis and biochemical studies with prenyltransferases

    Science.gov (United States)

    DeGraw, Amanda J.; Zhao, Zongbao; Strickland, Corey L.; Taban, A. Huma; Hsieh, John; Michael, Jefferies; Xie, Wenshuang; Shintani, David; McMahan, Colleen; Cornish, Katrina; Distefano, Mark D.

    2008-01-01

    A number of biochemical processes rely on isoprenoids, including the post-translational modification of signaling proteins and the biosynthesis of a wide array of compounds. Photoactivatable analogues have been developed to study isoprenoid utilizing enzymes such as the isoprenoid synthases and prenyltransferases. While these initial analogues proved to be excellent structural analogues with good cross linking capability, they lack the stability needed when the goals include isolation of cross-linked species, tryptic digestion, and subsequent peptide sequencing. Here, the synthesis of a benzophenone-based farnesyl diphosphate analogue containing a stable phosphonophosphate group is described. Inhibition kinetics, photolabeling experiments, as well as x-ray crystallographic analysis with a protein prenyltransferase are described, verifying this compound as a good isoprenoid mimetic. In addition, the utility of this new analogue was explored by using it to photoaffinity label crude protein extracts obtained from Hevea brasiliensis latex. Those experiments suggest that a small protein, Rubber Elongation Factor, interacts directly with farnesyl diphosphate during rubber biosynthesis. These results indicate that this benzophenone-based isoprenoid analogue will be useful for identifying enzymes that utilize farnesyl diphosphate as a substrate. PMID:17477573

  12. The Valles natural analogue project

    Energy Technology Data Exchange (ETDEWEB)

    Stockman, H.; Krumhansl, J.; Ho, C. [Sandia National Labs., Albuquerque, NM (United States); McConnell, V. [Alaska Univ., Fairbanks, AK (United States). Geophysical Inst.

    1994-12-01

    The contact between an obsidian flow and a steep-walled tuff canyon was examined as an analogue for a highlevel waste repository. The analogue site is located in the Valles Caldera in New Mexico, where a massive obsidian flow filled a paleocanyon in the Battleship Rock tuff. The obsidian flow provided a heat source, analogous to waste panels or an igneous intrusion in a repository, and caused evaporation and migration of water. The tuff and obsidian samples were analyzed for major and trace elements and mineralogy by INAA, XRF, X-ray diffraction; and scanning electron microscopy and electron microprobe. Samples were also analyzed for D/H and {sup 39}Ar/{sup 4O} isotopic composition. Overall,the effects of the heating event seem to have been slight and limited to the tuff nearest the contact. There is some evidence of devitrification and migration of volatiles in the tuff within 10 meters of the contact, but variations in major and trace element chemistry are small and difficult to distinguish from the natural (pre-heating) variability of the rocks.

  13. Photo-initiated dynamics and spectroscopy of the deprotonated Green Fluorescent Protein chromophore

    DEFF Research Database (Denmark)

    Bochenkova, Anastasia; Andersen, Lars Henrik

    2013-01-01

    . Knowledge of intrinsic properties of the GFP photoabsorbing molecular unit is a prerequisite in understanding the atomic-scale interactions that play a key role for the diverse functioning of these proteins. Here, we show how recent developments in action and photoelectron spectroscopy combined with state......-of-the-art electronic structure theory provide valuable insights into photo-initiated quantum dynamics and enable to disclose mechanisms of multiple intrinsic excited-state decay channels in the bare GFP chromophore anion. When taken out of the protein, the deprotonated chromophore exhibits the ultrafast excited state...... efficiently compete with each other in spite of their inherently different intrinsic timescales. The reason behind this is an efficient coupling between the nuclear and electronic motion in the photo-initiated dynamics, where the energy may be transferred from nuclei to electrons and from electrons to nuclei...

  14. High diffraction efficiency at low electric field in photorefractive polymers doped with arylimine chromophores

    Energy Technology Data Exchange (ETDEWEB)

    Maldonado, J L; Ponce-de-Leon, Y; Ramos-Ortiz, G; RodrIguez, M; Meneses-Nava, M A; Barbosa-Garcia, O [Centro de Investigaciones en Optica A.P. 1-948, 37000 Leon, Gto. (Mexico); Santillan, R [Departamento de Quimica, Centro de Investigacion y de Estudios Avanzados del IPN, A.P. 14-740, 07000 Mexico D.F. (Mexico); Farfan, N, E-mail: jlmr@cio.m [Facultad de QuImica, Departamento de QuImica Organica, Universidad Nacional Autonoma de Mexico, Mexico, D.F., 04510 (Mexico)

    2009-04-07

    We report on the high photorefractive performance of organic polymers doped with arylimine chromophore (diethylaminosalicylaldiminato)nitrobenzene (H1) and its derivative (diethylaminophenylaldiminato)nitrophenol (H2). Polymer blends of H1 and H2 with PVK : ECZ : C{sub 60} at 25 : 49 : 25 : 1 wt% and H2 : PVK : ECZ : PC{sub 61}BM at the same concentration were fabricated. The electric field (E) steady-state diffraction efficiency dependence and the optical gain were measured through holographic experiments at room temperature. For polymers based on chromophore H2, overmodulation of the diffraction efficiency was measured at just E = 32 V {mu}m{sup -1} obtaining 75%, and for polymers based on H1, diffraction of 87% (overmodulation) at E = 48 V {mu}m{sup -1} was observed. Holographic recording imaging was demonstrated at an electric field of just 10-14 V {mu}m{sup -1}.

  15. Low dipole moment large β electrooptic chromophores based on exocyclic double bond conjugated bridge

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Novel low dipole moment (μ) and large first hyperpolarizability (β) electrooptic chromophores have been designed based on the special characteristic of reversed dipole moment in the excited state of exocyclic double bond (ECDB) conjugated bridge by the optimization of the substituted method, and their electronic and second-order nonlinear optical properties have been theoretically investigated by employing the AM1/FF and ZINDO/S-CI approaches. By extending the conjugation length and optimizing the donor/acceptor strength, the oscillator strength of the excited transition that contributes to the molecular nonlinearity can be further enhanced. The designed chromophores possess a larger figure of merit (FOM) than that of D) ground state dipole moment.``

  16. Novel multi-chromophor light absorber concepts for DSSCs for efficient electron injection

    Energy Technology Data Exchange (ETDEWEB)

    Schuetz, Robert; Strothkaemper, Christian; Bartelt, Andreas; Hannappel, Thomas; Eichberger, Rainer [Helmholtz-Zentrum Berlin fuer Materialien und Energie, Hahn-Meitner-Platz 1, 14109 Berlin (Germany); Fasting, Carlo [Institut fuer Organische Chemie, Freie Universitaet Berlin, Takustrasse 3, 14195 Berlin (Germany); Thomas, Inara [Helmholtz-Zentrum Berlin fuer Materialien und Energie, Hahn-Meitner-Platz 1, 14109 Berlin (Germany); Institut fuer Organische Chemie, Freie Universitaet Berlin, Takustrasse 3, 14195 Berlin (Germany)

    2011-07-01

    Dye sensitized solar cells (DSSCs) operate by injecting electrons from the excited state of a light-harvesting dye into the continuum of conduction band states of a wide bandgap semiconductor. The light harvesting efficiency of pure organic dyes is limited by a narrow spectral electronic transition. A beneficial broad ground state absorption in the VIS region can be achieved by applying a single molecular dye system with multiple chromophors involving a Foerster resonance energy transfer (FRET) mechanism for an efficient electron injection. A model donor acceptor dye system capable for FRET chemically linked to colloidal TiO{sub 2} and ZnO nanorod surfaces was investigated in UHV environment. We used VIS/NIR femtosecond transient absorption spectroscopy and optical pump terahertz probe spectroscopy to study the charge injection dynamics of the antenna system. Different chromophors attached to a novel scaffold/anchor system connecting the organic absorber unit to the metal oxide semiconductor were probed.

  17. Investigation of two-photon absorption induced excited state absorption in a fluorenyl-based chromophore.

    Science.gov (United States)

    Li, Changwei; Yang, Kun; Feng, Yan; Su, Xinyan; Yang, Junyi; Jin, Xiao; Shui, Min; Wang, Yuxiao; Zhang, Xueru; Song, Yinglin; Xu, Hongyao

    2009-12-03

    Two-photon absorption induced excited state absorption in the solution of a new fluorenyl-based chromophore is investigated by a time-resolved pump-probe technique using femtosecond pulses. With the help of an additional femtosecond open-aperture Z-scan technique, numerical simulations based on a three-energy level model are used to interpret the experimental results, and we determine the nonlinear optical parameters of this new chromophore uniquely. Large two-photon absorption cross section and excited state absorption cross section for singlet excited state are obtained, indicating a good candidate for optical limiting devices. Moreover, the influence of two-beam coupling induced energy transfer in neat N,N'-dimethylformamide solvent is also considered, although this effect is strongly restrained by the instantaneous two-photon absorption.

  18. Direct Measurement of the Isomerization Barrier of the Isolated Retinal Chromophore

    Science.gov (United States)

    2015-11-03

    mobility spectroscopy (IMS) allows one to differentiate between different isomers of a given molecular ion according to their collisional cross-section...Physics and Astronomy , Aarhus Universi-ty, DK-8000 Aarhus C, Denmark Synopsis Energy barrier Heights for isomerization of the isolated retinal...chromophore were measured using two stages of ion mobility spectroscopy (IMS-IMS). Ion mobility spectroscopy (IMS) allows one to differentiate between

  19. Phytochrome from Agrobacterium tumefaciens has unusual spectral properties and reveals an N-terminal chromophore attachment site

    OpenAIRE

    Lamparter, Tilman; Michael, Norbert; Mittmann, Franz; Esteban, Berta

    2002-01-01

    Phytochromes are photochromic photoreceptors with a bilin chromophore that are found in plants and bacteria. The soil bacterium Agrobacterium tumefaciens contains two genes that code for phytochrome-homologous proteins, termed Agrobacterium phytochrome 1 and 2 (Agp1 and Agp2). To analyze its biochemical and spectral properties, Agp1 was purified from the clone of an E. coli overexpressor. The protein was assembled with the chromophores phycocyanobilin and biliverdin, which is the putative nat...

  20. Minimal domain of bacterial phytochrome required for chromophore binding and fluorescence

    Science.gov (United States)

    Rumyantsev, Konstantin A.; Shcherbakova, Daria M.; Zakharova, Natalia I.; Emelyanov, Alexander V.; Turoverov, Konstantin K.; Verkhusha, Vladislav V.

    2015-12-01

    Fluorescent proteins (FP) are used to study various biological processes. Recently, a series of near-infrared (NIR) FPs based on bacterial phytochromes was developed. Finding ways to improve NIR FPs is becoming progressively important. By applying rational design and molecular evolution we have engineered R. palustris bacterial phytochrome into a single-domain NIR FP of 19.6 kDa, termed GAF-FP, which is 2-fold and 1.4-fold smaller than bacterial phytochrome-based NIR FPs and GFP-like proteins, respectively. Engineering of GAF-FP involved a substitution of 15% of its amino acids and a deletion of the knot structure. GAF-FP covalently binds two tetrapyrrole chromophores, biliverdin (BV) and phycocyanobilin (PCB). With the BV chromophore GAF-FP absorbs at 635 nm and fluoresces at 670 nm. With the PCB chromophore GAF-FP becomes blue-shifted and absorbs at 625 nm and fluoresces at 657 nm. The GAF-FP structure has a high tolerance to small peptide insertions. The small size of GAF-FP and its additional absorbance band in the violet range has allowed for designing a chimeric protein with Renilla luciferase. The chimera exhibits efficient non-radiative energy transfer from luciferase to GAF-FP, resulting in NIR bioluminescence. This study opens the way for engineering of small NIR FPs and NIR luciferases from bacterial phytochromes.

  1. Eumelanin broadband absorption develops from aggregation-modulated chromophore interactions under structural and redox control

    Science.gov (United States)

    Micillo, Raffaella; Panzella, Lucia; Iacomino, Mariagrazia; Prampolini, Giacomo; Cacelli, Ivo; Ferretti, Alessandro; Crescenzi, Orlando; Koike, Kenzo; Napolitano, Alessandra; d’Ischia, Marco

    2017-01-01

    Eumelanins, the chief photoprotective pigments in man and mammals, owe their black color to an unusual broadband absorption spectrum whose origin is still a conundrum. Excitonic effects from the interplay of geometric order and disorder in 5,6-dihydroxyindole (DHI)-based oligomeric/polymeric structures play a central role, however the contributions of structural (scaffold-controlled) and redox (π-electron-controlled) disorder have remained uncharted. Herein, we report an integrated experimental-theoretical entry to eumelanin chromophore dynamics based on poly(vinyl alcohol)-controlled polymerization of a large set of 5,6-dihydroxyindoles and related dimers. The results a) uncover the impact of the structural scaffold on eumelanin optical properties, disproving the widespread assumption of a universal monotonic chromophore; b) delineate eumelanin chromophore buildup as a three-step dynamic process involving the rapid generation of oxidized oligomers, termed melanochromes (phase I), followed by a slow oxidant-independent band broadening (phase II) leading eventually to scattering (phase III); c) point to a slow reorganization-stabilization of melanochromes via intermolecular redox interactions as the main determinant of visible broadband absorption. PMID:28150707

  2. Fiber optic-based fluorescence detection system for in vivo studies of exogenous chromophore pharmacokinetics

    Science.gov (United States)

    Doiron, Daniel R.; Dunn, J. B.; Mitchell, W. L.; Dalton, Brian K.; Garbo, Greta M.; Warner, Jon A.

    1995-05-01

    The detection and quantification of the concentration of exogenous chromophores in-vivo by their fluorescence is complicated by many physical and geometrical parameters. Measurement of such signals is advantageous in determining the pharmacokinetics of photosensitizers such as those used in photodynamic therapy (PDT) or to assist in the diagnosis of tissue histological state. To overcome these difficulties a ratio based fiber optic contact fluorometer has been developed. This fluorescence detection system (FDS) uses the ratio of the fluorescence emission peak of the exogenous chromophore to that of endogenous chromophores, i.e. autofluorescence, to correct for a variety of parameters affecting the magnitude of the measured signals. By doing so it also minimizes the range of baseline measurements prior to exogenous drug injection, for various tissue types. Design of the FDS and results of its testing in animals and patients using the second generation photosensitizer Tin ethyletiopurpurin (SnET2) are presented. These results support the feasibility and usefulness of the Ratio FDS system.

  3. Chromophores from photolyzed ammonia reacting with acetylene: Application to Jupiter's Great Red Spot

    Science.gov (United States)

    Carlson, R. W.; Baines, K. H.; Anderson, M. S.; Filacchione, G.; Simon, A. A.

    2016-08-01

    The high altitude of Jupiter's Great Red Spot (GRS) may enhance the upward flux of gaseous ammonia (NH3) into the high troposphere, where NH3 molecules can be photodissociated and initiate a chain of chemical reactions with downwelling acetylene molecules (C2H2). These reactions, experimentally studied earlier by (Ferris and Ishikawa [1987] Nature 326, 777-778) and (Ferris and Ishikawa [1988] J. Amer. Chem. Soc. 110, 4306-4312), produce chromophores that absorb in the visible and ultraviolet regions. In this work we photolyzed mixtures of NH3 and C2H2 using ultraviolet radiation with a wavelength of 214 nm and measured the spectral transmission of the deposited films in the visible region (400-740 nm). From these transmission data we estimated the imaginary indices of refraction. Assuming that ammonia grains at the top of the GRS clouds are coated with this material, we performed layered sphere and radiative transfer calculations to predict GRS reflection spectra. Comparison of those results with observed and previously unreported Cassini visible spectra and with true-color images of the GRS show that the unknown GRS chromophore is spectrally consistent with the coupled NH3-C2H2 photochemical products produced in our laboratory experiments. Using high-resolution mass spectrometry and infrared spectroscopy we infer that the chromophore-containing residue is composed of aliphatic azine, azo, and diazo compounds.

  4. Modeling trans-cis chromophore isomerization for the asFP595 kindling protein

    Science.gov (United States)

    Grigorenko, Bella L.; Nemukhin, Alexander V.

    2007-02-01

    We present the results of modeling properties of the chromophore, 2-acetyl-4-(p-hydroxybenzylidene)-1-methyl-5- imidazolone (AHBMI), from the newly discovered fluorescent protein asFP595 inside the protein environment by using the combined quantum mechanical - molecular mechanical (QM/MM) method. In this approach, the chromophore unit and the side chains of the nearest amino acid residues are assigned to the quantum subsystem. The starting coordinates of heavy atoms were taken from the relevant crystal structures of the protein. Hydrogen atoms were added manually, and the structure of the model protein system was optimized by using QM/MM energy minimization for the trans-form of the chromophore. The Hartree-Fock/6-31G quantum chemical approximation and the AMBER force field parameters were employed in geometry optimization. The points on potential energy surfaces of the ground and first and second excited electronic states were computed with the complete active space self-consistent field approximation in the quantum subsystem under different choices of the QM/MM partitioning. Possible pathways for the trans-cis photo isomerization presumably responsible for the kindling properties of asFP595 as well as other mechanisms of photo excitation are discussed.

  5. Chromophores from photolyzed ammonia reacting with acetylene: Application to Jupiters Great Red Spot

    Science.gov (United States)

    Carlson, Robert W.; Baines, Kevin H.; Anderson, M. S.; Filacchione, G.; Simon, A. A.

    2016-01-01

    The high altitude of Jupiter's Great Red Spot (GRS) may enhance the upward flux of gaseous ammonia (NH3 ) into the high troposphere, where NH3 molecules can be photodissociated and initiate a chain of chemical reactions with downwelling acetylene molecules (C2H2 ). These reactions, experimentally studied earlier by (Ferris and Ishikawa [1987] Nature 326, 777-778) and (Ferris and Ishikawa [1988] J. Amer. Chem. Soc. 110, 4306-4312), produce chromophores that absorb in the visible and ultraviolet regions. In this work we photolyzed mixtures of NH3 and C2H2 using ultraviolet radiation with a wavelength of 214 nm and measured the spectral transmission of the deposited films in the visible region (400-740 nm). From these transmission data we estimated the imaginary indices of refraction. Assuming that ammonia grains at the top of the GRS clouds are coated with this material, we performed layered sphere and radiative transfer calculations to predict GRS reflection spectra. Comparison of those results with observed and previously unreported Cassini visible spectra and with true-color images of the GRS show that the unknown GRS chromophore is spectrally consistent with the coupled NH3-C2H2 photochemical products produced in our laboratory experiments. Using high-resolution mass spectrometry and infrared spectroscopy we infer that the chromophore-containing residue is composed of aliphatic azine, azo, and diazo compounds.

  6. Strategy and methodology of dynamical analogue prediction

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In order to effectively improve numerical prediction level by using current models and data, the strategy and methodology of dynamical analogue prediction (DAP) is deeply studied in the present paper. A new idea to predict the prediction errors of dynamical model on the basis of historical analogue information is put forward so as to transform the dynamical prediction problem into the estimation problem of prediction errors. In terms of such an idea, a new prediction method of final analogue correction of errors (FACE) is developed. Furthermore, the FACE is applied to extra-seasonal prediction experiments on an operational atmosphere-ocean coupled general circulation model. Prediction results of summer mean circulation and total precipitation show that the FACE can to some extent reduce prediction errors, recover prediction variances, and improve prediction skills. Besides, sensitive experiments also show that predictions based on the FACE are evidently influenced by the number of analogues, analogue-selected variables and analogy metric.

  7. The future of somatostatin analogue therapy.

    Science.gov (United States)

    Stewart, P M; James, R A

    1999-10-01

    Since its discovery almost 30 years ago, the mode of action and therapeutic applications of somatostatin have been defined. In particular the cloning and characterization of somatostatin receptor subtypes has facilitated the development of high affinity analogues. In the context of pituitary disease, long-acting somatostatin analogues (octreotide, lanreotide) have been used to treat a variety of pituitary tumours but are most efficacious for the treatment of GH and TSH-secreting adenomas. In patients with acromegaly, depot preparations of these analogues are administered intramuscularly every 10-28 days and provide consistent suppression of GH levels to < 5 mU/l in approximately 50-65% of all cases. Even more specific somatostatin receptor analogues are under development. Finally, radiolabelled somatostatin analogue scintigraphy and, in larger doses, therapy, are now established tools in the evaluation and treatment of neuroendocrine tumours.

  8. Significant Improvement of Optoelectronic and Photovoltaic Properties by Incorporating Thiophene in a Solution-Processable D–A–D Modular Chromophore

    Directory of Open Access Journals (Sweden)

    Aaron M. Raynor

    2015-12-01

    Full Text Available Through the incorporation of a thiophene functionality, a novel solution-processable small organic chromophore was designed, synthesized and characterized for application in bulk-heterojunction solar cells. The new chromophore, (2Z,2′Z-2,2′-(1,4-phenylenebis(3-(5-(4-(diphenylaminophenylthiophen-2-ylacrylonitrile (coded as AS2, was based on a donor–acceptor–donor (D–A–D module where a simple triphenylamine unit served as an electron donor, 1,4-phenylenediacetonitrile as an electron acceptor, and a thiophene ring as the π-bridge embedded between the donor and acceptor functionalities. AS2 was isolated as brick-red, needle-shaped crystals, and was fully characterized by 1H- and 13C-NMR, IR, mass spectrometry and single crystal X-ray diffraction. The optoelectronic and photovoltaic properties of AS2 were compared with those of a structural analogue, (2Z,2′Z-2,2′-(1,4-phenylenebis(3-(4-(diphenylaminophenyl-acrylonitrile (AS1. Benefiting from the covalent thiophene bridges, compared to AS1 thin solid film, the AS2 film showed: (1 an enhancement of light-harvesting ability by 20%; (2 an increase in wavelength of the longest wavelength absorption maximum (497 nm vs. 470 nm and (3 a narrower optical band-gap (1.93 eV vs. 2.17 eV. Studies on the photovoltaic properties revealed that the best AS2-[6,6]-phenyl-C61-butyric acid methyl ester (PC61BM-based device showed an impressive enhanced power conversion efficiency of 4.10%, an approx. 3-fold increase with respect to the efficiency of the best AS1-based device (1.23%. These results clearly indicated that embodiment of thiophene functionality extended the molecular conjugation, thus enhancing the light-harvesting ability and short-circuit current density, while further improving the bulk-heterojunction device performance. To our knowledge, AS2 is the first example in the literature where a thiophene unit has been used in conjunction with a 1,4-phenylenediacetonitrile accepting

  9. Vibrational and quantum-chemical study of push-pull chromophores for second-order nonlinear optics from rigidified thiophene-based pi-conjugating spacers.

    Science.gov (United States)

    Ruiz Delgado, Mari Carmen; Hernández, Víctor; Casado, Juan; López Navarrete, Juan T; Raimundo, Jean-Manuel; Blanchard, Philippe; Roncali, Jean

    2003-08-01

    Two types of push-pull chromophores built around thiophene-based pi-conjugating spacers rigidified by either covalent bonds or noncovalent intramolecular interactions have been analysed by means of IR and Raman spectroscopical measurements in the solid state as well as in a variety of solvents. Comparison of the Raman features of NLO-phores based on a covalently rigidified dithienylene (DTE) spacer with those of their open chain DTE analogues shows that the bridging of the central double bond of DTE with the nearest beta-positions of the thienyl units through two ethylene bridges significantly improves the intramolecular charge transfer. This also occurs for NLO-phores based on a 2,2'-bi(3,4-ethylenedioxythiophene) (BEDOT) spacer as compared with their corresponding parent compounds based on an unsubstituted bithiophene (BT) spacer. For NLO-phores based on a BEDOT spacer, noncovalent intramolecular interactions between sulfur and oxygen atoms are responsible for the rigidification of the spacer. The Raman spectra of these NLO-phores obtained in the form of solutes in dilute solutions reveal two different behaviours: i) chromophores based on covalently bridged or open chain DTE spacers display Raman spectral profiles in solution quite similar to those of the corresponding solids, with a very little dependence on the polarity of the solvent, while ii) larger spectral changes are noticed for NLO-phores built around BEDOT or BT spacers on going from solids to solutions. In the second case, spectral changes must be ascribed not solely to conformational distortions of the donor and acceptor end groups with respect to the pi-conjugated backbone mean-square-plane (as for the DTE-based NLO-phores) but also to distortions of the thienyl units of the pi-conjugating spacer from coplanarity. The insertion of vinylenic bridges between the thienyl units of the pi-conjugating spacer and between the spacer and the donor and acceptor end groups is a suitable strategy to reach a

  10. A new bis-tetraamine ligand with a chromophoric 4-(9-anthracenyl)-2,6-dimethylpyridinyl linker for glyphosate and ATP sensing.

    Science.gov (United States)

    Pouessel, Jacky; Abada, Sabah; Le Bris, Nathalie; Elhabiri, Mourad; Charbonnière, Loïc J; Tripier, Raphaël

    2013-04-14

    The synthesis of a new linear bis-tetraamine ligand L1, based on two 1,4,8,11-tetraazaundecane units grafted at the 2 and 6 positions of a pyridinyl linker substituted by an anthracenyl fluorophore in the para position, is described and anion complexation studies of L1 with anionic substrates are reported. The protonation pattern and the study of the binding properties of L1 in an aqueous medium with two anionic substrates, the nucleotide adenosine triphosphate (ATP) and the herbicide glyphosate (N-(phosphonomethyl)glycine, PMG), were investigated by means of potentiometry, NMR spectroscopy and absorption and emission spectroscopic techniques. To decipher the impact of the chromophoric linker on the complexation process and to highlight its optical properties, a comparison is established with its previously reported analog L2 devoid of the anthracenyl group. The results unambiguously show that the protonation and complexation properties are preserved despite the presence of the bulky linker, allowing for the use of L1 as a fluorescent sensor for ATP and PMG.

  11. Space analogue studies in Antarctica

    Science.gov (United States)

    Lugg, D.; Shepanek, M.

    1999-01-01

    Medical research has been carried out on the Australian National Antarctic Research Expeditions (ANARE) for 50 years. As an extension of this program collaborative Australian/United States research on immunology, microbiology, psychology and remote medicine has produced important data and insight on how humans adapt to the stress of extreme isolation, confinement and the harsh environment of Antarctica. An outstanding analogue for the isolation and confinement of space missions (especially planetary outposts), ANARE has been used as an international research platform by Australia and the United States since 1993. Collaborative research has demonstrated a lowered responsiveness of the immune system under the isolation and confinement of Antarctic winter-over; a reduction of almost 50% in T cell proliferation to mitogen phytohaemogglutinin, as well as changes in latent herpesvirus states and the expansion of the polyclonal latent Epstein-Barr virus infected B cell populations. Although no clinically significant disease has been found to result from these immune changes, research is currently assessing the effects of psychological factors on the immune system. This and associated research performed to date and its relevance to both organisations is discussed, and comment made on possible extensions to the program in both medical and other fields.

  12. Condensed matter analogues of cosmology

    Science.gov (United States)

    Kibble, Tom; Srivastava, Ajit

    2013-10-01

    It is always exciting when developments in one branch of physics turn out to have relevance in a quite different branch. It would be hard to find two branches farther apart in terms of energy scales than early-universe cosmology and low-temperature condensed matter physics. Nevertheless ideas about the formation of topological defects during rapid phase transitions that originated in the context of the very early universe have proved remarkably fruitful when applied to a variety of condensed matter systems. The mathematical frameworks for describing these systems can be very similar. This interconnection has led to a deeper understanding of the phenomena in condensed matter systems utilizing ideas from cosmology. At the same time, one can view these condensed matter analogues as providing, at least in a limited sense, experimental access to the phenomena of the early universe for which no direct probe is possible. As this special issue well illustrates, this remains a dynamic and exciting field. The basic idea is that when a system goes through a rapid symmetry-breaking phase transition from a symmetric phase into one with spontaneously broken symmetry, the order parameter may make different choices in different regions, creating domains that when they meet can trap defects. The scale of those domains, and hence the density of defects, is constrained by the rate at which the system goes through the transition and the speed with which order parameter information propagates. This is what has come to be known as the Kibble-Zurek mechanism. The resultant scaling laws have now been tested in a considerable variety of different systems. The earliest experiments illustrating the analogy between cosmology and condensed matter were in liquid crystals, in particular on the isotropic-to-nematic transition, primarily because it is very easy to induce the phase transition (typically at room temperature) and to image precisely what is going on. This field remains one of the

  13. Antimicrobial Activity of Resveratrol Analogues

    Directory of Open Access Journals (Sweden)

    Malik Chalal

    2014-06-01

    Full Text Available Stilbenes, especially resveratrol and its derivatives, have become famous for their positive effects on a wide range of medical disorders, as indicated by a huge number of published studies. A less investigated area of research is their antimicrobial properties. A series of 13 trans-resveratrol analogues was synthesized via Wittig or Heck reactions, and their antimicrobial activity assessed on two different grapevine pathogens responsible for severe diseases in the vineyard. The entire series, together with resveratrol, was first evaluated on the zoospore mobility and sporulation level of Plasmopara viticola (the oomycete responsible for downy mildew. Stilbenes displayed a spectrum of activity ranging from low to high. Six of them, including the most active ones, were subsequently tested on the development of Botrytis cinerea (fungus responsible for grey mold. The results obtained allowed us to identify the most active stilbenes against both grapevine pathogens, to compare the antimicrobial activity of the evaluated series of stilbenes, and to discuss the relationship between their chemical structure (number and position of methoxy and hydroxy groups and antimicrobial activity.

  14. Enzymatic tRNA acylation by acid and alpha-hydroxy acid analogues of amino acids.

    Science.gov (United States)

    Owczarek, Alina; Safro, Mark; Wolfson, Alexey D

    2008-01-08

    Incorporation of unnatural amino acids with unique chemical functionalities has proven to be a valuable tool for expansion of the functional repertoire and properties of proteins as well as for structure-function analysis. Incorporation of alpha-hydroxy acids (primary amino group is substituted with hydroxyl) leads to the synthesis of proteins with peptide bonds being substituted by ester bonds. Practical application of this modification is limited by the necessity to prepare corresponding acylated tRNA by chemical synthesis. We investigated the possibility of enzymatic incorporation of alpha-hydroxy acid and acid analogues (lacking amino group) of amino acids into tRNA using aminoacyl-tRNA synthetases (aaRSs). We studied direct acylation of tRNAs by alpha-hydroxy acid and acid analogues of amino acids and corresponding chemically synthesized analogues of aminoacyl-adenylates. Using adenylate analogues we were able to enzymatically acylate tRNA with amino acid analogues which were otherwise completely inactive in direct aminoacylation reaction, thus bypassing the natural mechanisms ensuring the selectivity of tRNA aminoacylation. Our results are the first demonstration that the use of synthetic aminoacyl-adenylates as substrates in tRNA aminoacylation reaction may provide a way for incorporation of unnatural amino acids into tRNA, and consequently into proteins.

  15. Heterocyclic chalcone analogues as potential anticancer agents.

    Science.gov (United States)

    Sharma, Vikas; Kumar, Vipin; Kumar, Pradeep

    2013-03-01

    Chalcones, aromatic ketones and enones acting as the precursor for flavonoids such as Quercetin, are known for their anticancer effects. Although, parent chalcones consist of two aromatic rings joined by a three-carbon α,β-unsaturated carbonyl system, various synthetic compounds possessing heterocyclic rings like pyrazole, indole etc. are well known and proved to be effective anticancer agents. In addition to their use as anticancer agents in cancer cell lines, heterocyclic analogues are reported to be effective even against resistant cell lines. In this connection, we hereby highlight the potential of various heterocyclic chalcone analogues as anticancer agents with a brief summary about therapeutic potential of chalcones, mechanism of anticancer action of various chalcone analogues, and current and future prospects related to the chalcones-derived anticancer research. Furthermore, some key points regarding chalcone analogues have been reviewed by analyzing their medicinal properties.

  16. Total Synthesis of the Analogue of Icogenin

    Institute of Scientific and Technical Information of China (English)

    Shu Jie HOU; Peng XU; Liang ZHOU; De Quan YU; Ping Sheng LEI; Chuan Chun ZOU

    2006-01-01

    One of the analogues of icogenin, a natural furostanol saponin showing strong cytotoxic effect on cancer cell, was first synthesized via convergent strategy by using diosgenin and available monosaccharides as starting materials,

  17. Second-Generation Fluorescent Quadracyclic Adenine Analogues

    DEFF Research Database (Denmark)

    Dumat, Blaise; Bood, Mattias; Wranne, Moa S.;

    2015-01-01

    Fluorescent base analogues comprise a group of increasingly important molecules for the investigation of nucleic acid structure, dynamics, and interactions with other molecules. Herein, we report on the quantum chemical calculation aided design, synthesis, and characterization of four new putativ...

  18. Associated depression in pseudophakic patients with intraocular lens with and without chromophore

    Science.gov (United States)

    Mendoza-Mendieta, María Elena; Lorenzo-Mejía, Ana Aurora

    2016-01-01

    Background With aging, the crystalline lens turns yellowish, which increases the absorption of wavelengths in the blue electromagnetic spectrum, reducing their photoreception in the retina. Since these wavelengths are the main stimulus in the regulation of the circadian rhythm, progressive reduction in their transmission is associated with chronic sleep disturbances and depression in elderly patients. Cataract extraction improves circadian photoreception at any age. However, lenses that block blue waves have 27% to 38% less melatonin suppression than lenses that block only ultraviolet (UV) rays. Purpose To assess the depression symptoms in subjects who have had bilateral phacoemul-sification and intraocular lens (IOL) implants, one group with yellow chromophore IOLs and the other group with transparent IOLs were compared. Setting Association to Prevent Blindness in Mexico (APEC), Hospital “Dr Luis Sánchez Bulnes”. Design This was an observational, cross-sectional, and single-center study. Materials and methods Twenty-six subjects between 60 and 80 years of age, with a history of bilateral phacoemulsification and placement of the same type of IOL in both eyes from 4 to 12 months prior to the study, who attended the follow-up visits and agreed to participate in this study, and provided signed informed consent were included in the study. They were asked to answer the short version of the 15-item Geriatric Depression Scale. Results The average age of the study participants was 72.5±5.94 years. The group without chromophore included 46.1% (n=12) of the patients and the group with chromophore included 53.9% (n=14) of the patients (P=0.088). Conclusion In the group of patients with IOLs that block the passage of blue light, the depression rate was 21.4%, a rate similar to that observed in the elderly population, whereas no patients in the group with transparent IOLs had depression. PMID:27099465

  19. Chromophore photophysics and dynamics in fluorescent proteins of the GFP family

    Science.gov (United States)

    Nienhaus, Karin; Nienhaus, G. Ulrich

    2016-11-01

    Proteins of the green fluorescent protein (GFP) family are indispensable for fluorescence imaging experiments in the life sciences, particularly of living specimens. Their essential role as genetically encoded fluorescence markers has motivated many researchers over the last 20 years to further advance and optimize these proteins by using protein engineering. Amino acids can be exchanged by site-specific mutagenesis, starting with naturally occurring proteins as templates. Optical properties of the fluorescent chromophore are strongly tuned by the surrounding protein environment, and a targeted modification of chromophore-protein interactions requires a profound knowledge of the underlying photophysics and photochemistry, which has by now been well established from a large number of structural and spectroscopic experiments and molecular-mechanical and quantum-mechanical computations on many variants of fluorescent proteins. Nevertheless, such rational engineering often does not meet with success and thus is complemented by random mutagenesis and selection based on the optical properties. In this topical review, we present an overview of the key structural and spectroscopic properties of fluorescent proteins. We address protein-chromophore interactions that govern ground state optical properties as well as processes occurring in the electronically excited state. Special emphasis is placed on photoactivation of fluorescent proteins. These light-induced reactions result in large structural changes that drastically alter the fluorescence properties of the protein, which enables some of the most exciting applications, including single particle tracking, pulse chase imaging and super-resolution imaging. We also present a few examples of fluorescent protein application in live-cell imaging experiments.

  20. Molecular Biodynamers: Dynamic Covalent Analogues of Biopolymers

    Science.gov (United States)

    2017-01-01

    Conspectus Constitutional dynamic chemistry (CDC) features the use of reversible linkages at both molecular and supramolecular levels, including reversible covalent bonds (dynamic covalent chemistry, DCC) and noncovalent interactions (dynamic noncovalent chemistry, DNCC). Due to its inherent reversibility and stimuli-responsiveness, CDC has been widely utilized as a powerful tool for the screening of bioactive compounds, the exploitation of receptors or substrates driven by molecular recognition, and the fabrication of constitutionally dynamic materials. Implementation of CDC in biopolymer science leads to the generation of constitutionally dynamic analogues of biopolymers, biodynamers, at the molecular level (molecular biodynamers) through DCC or at the supramolecular level (supramolecular biodynamers) via DNCC. Therefore, biodynamers are prepared by reversible covalent polymerization or noncovalent polyassociation of biorelevant monomers. In particular, molecular biodynamers, biodynamers of the covalent type whose monomeric units are connected by reversible covalent bonds, are generated by reversible polymerization of bio-based monomers and can be seen as a combination of biopolymers with DCC. Owing to the reversible covalent bonds used in DCC, molecular biodynamers can undergo continuous and spontaneous constitutional modifications via incorporation/decorporation and exchange of biorelevant monomers in response to internal or external stimuli. As a result, they behave as adaptive materials with novel properties, such as self-healing, stimuli-responsiveness, and tunable mechanical and optical character. More specifically, molecular biodynamers combine the biorelevant characters (e.g., biocompatibility, biodegradability, biofunctionality) of bioactive monomers with the dynamic features of reversible covalent bonds (e.g., changeable, tunable, controllable, self-healing, and stimuli-responsive capacities), to realize synergistic properties in one system. In addition

  1. The structure activity relationship of discodermolide analogues.

    Science.gov (United States)

    Shaw, Simon J

    2008-03-01

    The marine polyketide discodermolide is a member of a class of natural products that stabilize microtubules. Many analogues have been synthesized suggesting that few changes can be made to the internal carbon backbone. Both ends of the molecule, however, can be modified. The majority of analogues have been generated via modification of the lactone region. This suggests that significant simplifications can be made in this region provided that the lactone moiety is maintained.

  2. Construction of Multi-Chromophoric Spectra from Monomer Data: Applications to Resonant Energy Transfer

    CERN Document Server

    Chenu, Aurélia

    2016-01-01

    We develop a model that establishes a quantitative link between the physical properties of molecular aggregates and their constituent building blocks. The relation is built on the coherent potential approximation, calibrated against exact results, and proven reliable for a wide range of parameters. It provides a practical method to compute spectra and transfer rates in multi-chromophoric systems from experimentally accessible monomer data. Applications to F\\"orster energy transfer reveal optimal transfer rates as functions of both the system-bath coupling and intra-aggregate coherence.

  3. Criteria for quantum coherent transfer of excitons between chromophores in a polar solvent

    CERN Document Server

    Gilmore, J; Gilmore, Joel; Kenzie, Ross H. Mc

    2004-01-01

    We show that the quantum decoherence of Forster resonant energy transfer between two optically active molecules can be described by a spin-boson model. This allows us to give quantitative criteria, in terms of experimentally measurable system parameters, that are necessary for coherent Bloch oscillations of excitons between the chromophores. Experimental tests of our results should be possible with Flourescent Resonant Energy Transfer (FRET) spectroscopy. Although we focus on the case of protein-pigment complexes our results are also relevant to quantum dots and organic molecules in a dielectric medium.

  4. A novel fluorescent turn-on probe for bisulfite based on NBD chromophore

    Indian Academy of Sciences (India)

    Puhui Xie; Guangqin Gao; Wenjie Zhang; Guoyu Yang; Qiu Jin

    2015-07-01

    A novel fluorescent turn-on probe (compound 1) for bisulfite based on 7-nitrobenz-2-oxa-1,3-diazole (NBD) chromophore has been developed. Its sensing behavior toward various anions was investigated by absorption and fluorescence techniques. This probe shows a selective, turn-on fluorescent response and ratiometric colorimetric response toward bisulfite in aqueous acetonitrile solutions. The possible recognition mechanism of probe 1 toward bisulfite was illustrated by MS spectra analysis and DFT calculations Probe 1 was used to determine bisulfite in real-life samples with good recoveries.

  5. Decoupling Electronic versus Nuclear Photoresponse of Isolated Green Fluorescent Protein Chromophores Using Short Laser Pulses

    Science.gov (United States)

    Kiefer, Hjalte V.; Pedersen, Henrik B.; Bochenkova, Anastasia V.; Andersen, Lars H.

    2016-12-01

    The photophysics of a deprotonated model chromophore for the green fluorescent protein is studied by femtosecond laser pulses in an electrostatic ion-storage ring. The laser-pulse duration is much shorter than the time for internal conversion, and, hence, contributions from sequential multiphoton absorption, typically encountered with ns-laser pulses, are avoided. Following single-photon excitation, the action-absorption maximum is shown to be shifted within the S0 to S1 band from its origin at about 490 to 450 nm, which is explained by the different photophysics involved in the detected action.

  6. Associated depression in pseudophakic patients with intraocular lens with and without chromophore

    Directory of Open Access Journals (Sweden)

    Mendoza-Mendieta ME

    2016-03-01

    Full Text Available María Elena Mendoza-Mendieta, Ana Aurora Lorenzo-Mejía Association to Prevent Blindness in Mexico (APEC, Hospital “Dr Luis Sánchez Bulnes”, Mexico City, Mexico Background: With aging, the crystalline lens turns yellowish, which increases the absorption of wavelengths in the blue electromagnetic spectrum, reducing their photoreception in the retina. Since these wavelengths are the main stimulus in the regulation of the circadian rhythm, progressive reduction in their transmission is associated with chronic sleep disturbances and depression in elderly patients. Cataract extraction improves circadian photoreception at any age. However, lenses that block blue waves have 27% to 38% less melatonin suppression than lenses that block only ultraviolet (UV rays. Purpose: To assess the depression symptoms in subjects who have had bilateral phacoemulsification and intraocular lens (IOL implants, one group with yellow chromophore IOLs and the other group with transparent IOLs were compared. Setting: Association to Prevent Blindness in Mexico (APEC, Hospital “Dr Luis Sánchez Bulnes”. Design: This was an observational, cross-sectional, and single-center study. Materials and methods: Twenty-six subjects between 60 and 80 years of age, with a history of bilateral phacoemulsification and placement of the same type of IOL in both eyes from 4 to 12 months prior to the study, who attended the follow-up visits and agreed to participate in this study, and provided signed informed consent were included in the study. They were asked to answer the short version of the 15-item Geriatric Depression Scale. Results: The average age of the study participants was 72.5±5.94 years. The group without chromophore included 46.1% (n=12 of the patients and the group with chromophore included 53.9% (n=14 of the patients (P=0.088. Conclusion: In the group of patients with IOLs that block the passage of blue light, the depression rate was 21.4%, a rate similar to that

  7. The radial distribution of water ice and chromophores across Saturn's system

    CERN Document Server

    Filacchione, G; Clark, R N; Nicholson, P D; Cruikshank, D P; Cuzzi, J N; Lunine, J I; Brown, R H; Cerroni, P; Tosi, F; Ciarniello, M; Buratti, B J; Hedman, M M; Flamini, E

    2013-01-01

    Over the last eight years, the Visual and Infrared Mapping Spectrometer (VIMS) aboard the Cassini orbiter has returned hyperspectral images in the 0.35-5.1 micron range of the icy satellites and rings of Saturn. These very different objects show significant variations in surface composition, roughness and regolith grain size as a result of their evolutionary histories, endogenic processes and interactions with exogenic particles. The distributions of surface water ice and chromophores, i.e. organic and non-icy materials, across the saturnian system, are traced using specific spectral indicators (spectral slopes and absorption band depths) obtained from rings mosaics and disk-integrated satellites observations by VIMS.

  8. Terrestrial research in Mars analogue environments

    Science.gov (United States)

    Osipov, G.

    Fatty acids (FA) content was measured by GC-MS SIM technique in Sulfide ores of present day (Mid-Atlantic Ridge and others) and ancient (Ural Paleocene, Russia) black smokers; Early Proterozoic kerites of Volyn; Siberian, Canadian and Antarctic permafrosts and also in rocks of East-European platform Achaean crystalline basement. Analysis was shown presence those and only those fatty acids which are specific to microorganisms. FA with 12 up 19 of carbon atoms are thought to be a bacterial biomass sign. 3-Hydroxy fatty acids also found in samples and are strong specific markers of gram-negative bacteria. Cultivation yield living bacteria in some cases. The East-European platform Achaean crystalline basement rocks opened by Vorotilov Deep Well (VDW) drilled through Puchezh-Katunski impact structure were studied within depths 2575 - 2805 m. 34 microbial lipid markers were detected by GC-MS and 22 species were identified. Bacteria of g. Bacillus reached 6,8 % in subsurface communities. However, members of gg. Clostridium (37,1 - 33,2 %) and Rhodococcus (27,6 - 33,7 %) were absolute dominants within studied depth interval. Some lipid patterns of kerite samples could be assessed to definite genera or, in special cases, to species of contemporary microorganisms. For instance, 2-hydroxylauric acid is specific to Pseudomonas putida group or Acinetobacter spp., and hydroxymyristic together with hydroxypalmitic are specific to P.cepacea and cyanobacteria. 3-hydroxystearic acid was known as component of Acetobacter diazothrophycus and Gloebacter violaceous cyanobacterium. 10-hydroxystearic acid associated with Nocardia spp., which oxidizes oleic acid in organic substrates. 10-methylhexadecanoic (10Me16) acid together with 10Me14, 10Me15 and 10Me17 analogues are markers of actinomycetes. Significant part of Black Smokers organic matter is probably biogenic. Fatty acid features strongly assigns it to bacterial, microeucariotic and planta cells. Par example 3-hydroxy acids are

  9. Light-induced conformational changes of the chromophore and the protein in phytochromes: bacterial phytochromes as model systems.

    Science.gov (United States)

    Scheerer, Patrick; Michael, Norbert; Park, Jung Hee; Nagano, Soshichiro; Choe, Hui-Woog; Inomata, Katsuhiko; Borucki, Berthold; Krauss, Norbert; Lamparter, Tilman

    2010-04-26

    Recombinant phytochromes Agp1 and Agp2 from Agrobacterium tumefaciens are used as model phytochromes for biochemical and biophysical studies. In biliverdin binding phytochromes the site for covalent attachment of the chromophore lies in the N-terminal region of the protein, different from plant phytochromes. The issue which stereochemistry the chromophore adopts in the so-called Pr and Pfr forms is addressed by using a series of locked chromophores which form spectrally characteristic adducts with Agp1 and Agp2. Studies on light-induced conformational changes of Agp1 give an insight into how the intrinsic histidine kinase is modulated by light. Comparison of the crystal structure of an Agp1 fragment with other phytochrome crystal structures supports the idea that a light induced rearrangement of subunits within the homodimer modulates the activity of the kinase.

  10. Active and silent chromophore isoforms for phytochrome Pr photoisomerization: An alternative evolutionary strategy to optimize photoreaction quantum yields

    Directory of Open Access Journals (Sweden)

    Yang Yang

    2014-01-01

    Full Text Available Photoisomerization of a protein bound chromophore is the basis of light sensing of many photoreceptors. We tracked Z-to-E photoisomerization of Cph1 phytochrome chromophore PCB in the Pr form in real-time. Two different phycocyanobilin (PCB ground state geometries with different ring D orientations have been identified. The pre-twisted and hydrogen bonded PCBa geometry exhibits a time constant of 30 ps and a quantum yield of photoproduct formation of 29%, about six times slower and ten times higher than that for the non-hydrogen bonded PCBb geometry. This new mechanism of pre-twisting the chromophore by protein-cofactor interaction optimizes yields of slow photoreactions and provides a scaffold for photoreceptor engineering.

  11. Power electronics substrate for direct substrate cooling

    Science.gov (United States)

    Le, Khiet [Mission Viejo, CA; Ward, Terence G [Redondo Beach, CA; Mann, Brooks S [Redondo Beach, CA; Yankoski, Edward P [Corona, CA; Smith, Gregory S [Woodland Hills, CA

    2012-05-01

    Systems and apparatus are provided for power electronics substrates adapted for direct substrate cooling. A power electronics substrate comprises a first surface configured to have electrical circuitry disposed thereon, a second surface, and a plurality of physical features on the second surface. The physical features are configured to promote a turbulent boundary layer in a coolant impinged upon the second surface.

  12. Multichromic Bis-Axially Extended Perylene Chromophore with Schiff Bases: Synthesis, Characterization and Electrochemical Studies.

    Science.gov (United States)

    Shabir, Ghulam; Saeed, Aamer; Arshad, Muhammad; Zahid, Muhammad

    2016-11-01

    In the present paper a novel way of symmetric conjugation extension along molecular axes of perylene dianhydride chromophore has been devised to achieve lengthy delocalized electronic species exhibiting red shifted absorption and emission of UV-Visible radiations. During synthetic pathway free amino Schiff bases of novel aldehydes with 4-amino acetanilide have been condensed with perylene dianhydride in quinoline at high temperature. Bis perylene diimide Schiff bases (5a-e) have been synthesized which showed absorption λmax at 461-526 nm and emission at 525-550 nm. Structures of newly obtained compounds have been confirmed by (1)H and (13)C-NMR studies. Cyclic voltammetric analysis of these dyes exhibited oxidation and reduction peaks which provide indirect evidence for their potential utility as n-type material for sensitization of semiconductors in solar cells. LUMO and HOMO energy levels were found in the range of -4.21 to -5.20 and -6.75 to -7.57 eV, respectively. Graphical Abstract Multi chromic bis-axially extended perylene chromophore with Schiff bases, synthesis characterization and electrochemical studies. Ghulam Shabir, Aamer Saeed, Muhammad Arshad and Muhammad Zahid.

  13. From gold nanoparticles to luminescent nano-objects: experimental aspects for better gold-chromophore interactions

    Science.gov (United States)

    Navarro, Julien R. G.; Lerouge, Frederic

    2017-01-01

    Gold nanoparticles have been the center of interest for scientists since many decades. Within the last 20 years, the research in that field has soared with the possibility to design and study nanoparticles with controlled shapes. From spheres to more complex shapes such as stars, or anisotropic architectures like rods or bipyramids, these new systems feature plasmonic properties making them the tools of choice for studies on light-matter interactions. In that context, fluorescence quenching and enhancement by gold nanostructures is a growing field of research. In this review, we report a non-exhaustive summary of the synthetic modes for various shapes and sizes of isotropic and anisotropic nanoparticles. We then focus on fluorescent studies of these gold nano-objects, either considering "bare" particles (without modifications) or hybrid particles (surface interaction with a chromophore). In the latter case, the well-known metal-enhanced fluorescence (MEF) is more particularly developed; the mechanisms of MEF are discussed in terms of the additional radiative and non-radiative decay rates caused by several parameters such as the vicinity of the chromophore to the metal or the size and shape of the nanostructures.

  14. New chromophores based on combination of ethylenedioxythiophene and carbazole fragments: synthesis and optoelectronic properties

    Science.gov (United States)

    Bakiev, A. N.; Mayorova, O. A.; Gorbunov, A. A.; Lunegov, I. V.; Shklyaeva, E. V.; Abashev, G. G.

    2016-12-01

    Two new D-π-A chromophores composed of an electron-donating carbazole unit linked through π- bridges, bearing 3,4-ethylenedioxythiophene (EDOT) moiety, with an electron withdrawing dicyanovinyl group (DCV) were successfully synthesized involving Suzuki or Heck cross-coupling and Knöevenagel reactions as the key steps. The obtained compounds absorb light over a broad spectral range, including the visible spectrum. The HOMO/LUMO energies and band gap energy values (Eg) were calculated on the basis of the experimental optical and electrochemical data: HOMO, LUMO, Eg (eV), -5.51, -3.14, 2.37 (4), -5.34, -3.14, 2.20 (7). The presence of the HC=CH unit in compound 7 resulted in the increase of the HOMO energy level, the decrease of a band gap value and red shifts of the absorption and emission bands in comparison with those of 4. Large Stokes shifts and broadband luminescence inherent to both chromophores suggest their use as materials for luminescent solar collectors (LSCs). The obtained compounds demonstrated good solubility and suitable thin-film forming properties. For this reason, they may be suitable for solution-processable photovoltaic applications.

  15. Unmixing chromophores in human skin with a 3D multispectral optoacoustic mesoscopy system

    Science.gov (United States)

    Schwarz, Mathias; Aguirre, Juan; Soliman, Dominik; Buehler, Andreas; Ntziachristos, Vasilis

    2016-03-01

    The absorption of visible light by human skin is governed by a number of natural chromophores: Eumelanin, pheomelanin, oxyhemoglobin, and deoxyhemoglobin are the major absorbers in the visible range in cutaneous tissue. Label-free quantification of these tissue chromophores is an important step of optoacoustic (photoacoustic) imaging towards clinical application, since it provides relevant information in diseases. In tumor cells, for instance, there are metabolic changes (Warburg effect) compared to healthy cells, leading to changes in oxygenation in the environment of tumors. In malignant melanoma changes in the absorption spectrum have been observed compared to the spectrum of nonmalignant nevi. So far, optoacoustic imaging has been applied to human skin mostly in single-wavelength mode, providing anatomical information but no functional information. In this work, we excited the tissue by a tunable laser source in the spectral range from 413-680 nm with a repetition rate of 50 Hz. The laser was operated in wavelengthsweep mode emitting consecutive pulses at various wavelengths that allowed for automatic co-registration of the multispectral datasets. The multispectral raster-scan optoacoustic mesoscopy (MSOM) system provides a lateral resolution of <60 μm independent of wavelength. Based on the known absorption spectra of melanin, oxyhemoglobin, and deoxyhemoglobin, three-dimensional absorption maps of all three absorbers were calculated from the multispectral dataset.

  16. Using NIR spatial illumination for detection and mapping chromophore changes during cerebral edema

    Science.gov (United States)

    Abookasis, David; Mathews, Marlon S.; Owen, Christopher M.; Binder, Devin K.; Linskey, Mark E.; Frostig, Ron D.; Tromberg, Bruce J.

    2008-02-01

    We used spatially modulated near-infrared (NIR) light to detect and map chromophore changes during cerebral edema in the rat neocortex. Cerebral edema was induced by intraperitoneal injections of free water (35% of body weight). Intracranial pressure (ICP) was measured with an optical fiber based Fabry-Perot interferometer sensor inserted into the parenchyma of the right frontal lobe during water administration. Increase in ICP from a baseline value of 10 cm-water to 145 cm-water was observed. Following induction of cerebral edema, there was a 26+/-1.7% increase in tissue concentration of deoxyhemoglobin and a 47+/-4.7%, 17+/-3% and 37+/-3.7% decrease in oxyhemoglobin, total hemoglobin concentration and cerebral tissue oxygen saturation levels, respectively. To the best of our knowledge, this is the first report describing the use of NIR spatial modulation of light for detecting and mapping changes in tissue concentrations of physiologic chromophores over time in response to cerebral edema.

  17. The Origin of Bond Selectivity and Excited-State Reactivity in Retinal Analogues.

    Science.gov (United States)

    Schapiro, Igor

    2016-05-19

    The effect of different conformations and substitutions on the photoisomerization of a retinal protonated Schiff base model is investigated by nonadiabatic molecular dynamics simulations. Three groups of retinal analogues are studied: (i) conformational isomers, (ii) methyl-substituted retinals, and (iii) C11-C12 bond locked retinals. In total 259 trajectories are calculated in the gas phase starting from different initial conditions. The effect on bond selectivity, the directionality of the isomerization, excited-state lifetime, and product distribution is derived from the ensemble of trajectories. Among the group of four isomers (9-, 11-, 13-cis, and all-trans) the 11-cis analogue is the most selective in terms of isomerizing double bond, while the other three produce a mixture of isomers. However, there is no preference for isomerization directionality and the product formation for the 11-cis isomer. In the group of analogues with different methylation patterns, it is found that a methyl group at position C10 can introduce unidirectionality. This methyl group also speeds the photoisomerization. In case of the analogue that is demethylated at the positions C10 and C13, all trajectories isomerize successfully from cis to trans conformation. The three C11-C12 bond locked retinals are found to have very different properties, which depend on the number of methylene units bridging this bond. The five-membered ring imposes a too-large restriction; hence, all trajectories remain on the excited state in the simulation time of 300 fs. The seven-membered ring is more flexible with preference for isomerization of the C9-C10 bond. Interestingly, the eight-membered ring leads to the fastest isomerization time and full directionality of C11-C12 bond isomerization. The trends observed in these simulations can help to understand whether the effects are intrinsic to the chromophore or are induced by the protein environment, by comparing to the trends from experiment. Furthermore

  18. Between Analogue and Digital Diagrams

    Directory of Open Access Journals (Sweden)

    Zoltan Bun

    2012-10-01

    Full Text Available This essay is about the interstitial. About how the diagram, as a method of design, has lead fromthe analogue deconstruction of the eighties to the digital processes of the turn of the millennium.Specifically, the main topic of the text is the interpretation and the critique of folding (as a diagramin the beginning of the nineties. It is necessary then to unfold its relationship with immediatelypreceding and following architectural trends, that is to say we have to look both backwards andforwards by about a decade. The question is the context of folding, the exchange of the analogueworld for the digital. To understand the process it is easier to investigate from the fields of artand culture, rather than from the intentionally perplicated1 thoughts of Gilles Deleuze. Both fieldsare relevant here because they can similarly be used as the yardstick against which the era itselfit measured. The cultural scene of the eighties and nineties, including performing arts, movies,literature and philosophy, is a wide milieu of architecture. Architecture responds parallel to itsera; it reacts to it, and changes with it and within it. Architecture is a medium, it has always beena medium, yet the relations are transformed. That’s not to say that technical progress, for exampleusing CAD-software and CNC-s, has led to the digital thinking of certain movements ofarchitecture, (it is at most an indirect tool. But the ‘up-to-dateness’ of the discipline, however,a kind of non-servile reading of an ‘applied culture’ or ‘used philosophy’2 could be the key.(We might recall here, parenthetically, the fortunes of the artistic in contemporary mass society.The proliferation of museums, the magnification of the figure of the artist, the existence of amassive consumption of printed and televised artistic images, the widespread appetite for informationabout the arts, all reflect, of course, an increasingly leisured society, but also relateprecisely to the fact

  19. Performance of popular XC-functionals for the description of excitation energies in GFP-like chromophore models

    DEFF Research Database (Denmark)

    List, Nanna Holmegaard; Olsen, Jógvan Magnus; Rocha-Rinza, Tomás

    2012-01-01

    Understanding and rationalization of the optical properties of fluorescent proteins are of great importance for life sciences due to their numerous applications as fluorescent biomarkers. Time-dependent density functional theory (TD-DFT) is a computationally appealing approach to accomplish...... this task. We present an evaluation of the performance of commonly used XC-functionals for the prediction of excitation energies of GFP-like chromophores. In particular, we have considered the TD-DFT vertical excitation energies of chromophores displaying different charge states. We compare the quality...

  20. Synthesis and NLO Properties of Chromophores with 1,8-Dimethoxy-9,10-dihydroanthracene and Thiobarbituric acid Moieties

    Institute of Scientific and Technical Information of China (English)

    WU De-Lin; JIA Zhao-Li; SHI Jie-Ping; SHI Zheng-Wei; LU Guo-Yuan

    2008-01-01

    The new chromophore molecules with nonlinear optical (NLO) properties were prepared by Knoevenagel condensation from 4,5-diformyl-1,8-dimethoxy-9,10-dihydroanthracene and thiobarbituric acid derivatives in the presence of piperidine and acetic acid. In these chromophores, the ring-locked triene employed as a conjugation bridge and the thiobarbituric acid moiety was as an electron acceptor in a D-π-A units. The solvatochromism and UV spectra indicate that they have higher second-order nonlinear polarizability μβ values than the corresponding reference compound, without causing a large red shift of the charge transfer band.

  1. Synthesis, photophysical properties of triazolyl-donor/acceptor chromophores decorated unnatural amino acids: Incorporation of a pair into Leu-enkephalin peptide and application of triazolylperylene amino acid in sensing BSA.

    Science.gov (United States)

    Bag, Subhendu Sekhar; Jana, Subhashis; Pradhan, Manoj Kumar

    2016-08-15

    The research in the field of design and synthesis of unnatural amino acids is growing at a fast space for the increasing demand of proteins of potential therapeutics and many other diversified novel functional applications. Thus, we report herein the design and synthesis of microenvironment sensitive fluorescent triazolyl unnatural amino acids (UNAA) decorated with donor and/or acceptor aromatic chromophores via click chemistry. The synthesized fluorescent amino acids show interesting solvatochromic characteristic and/or intramolecular charge transfer (ICT) feature as is revealed from the UV-visible, fluorescence photophysical properties and DFT/TDDFT calculation. HOMO-LUMO distribution shows that the emissive states of some of the amino acids are characterized with more significant electron redistribution between the triazolyl moiety and the aromatic chromophores linked to it leading to modulated emission property. A pair of donor-acceptor amino acid shows interesting photophysical interaction property indicating a FRET quenching event. Furthermore, one of the amino acid, triazolyl-perylene amino acid, has been exploited for studying interaction with BSA and found that it is able to sense BSA with an enhancement of fluorescence intensity. Finally, we incorporated a pair of donor/acceptor amino acids into a Leu-enkephalin analogue pentapeptide which was found to adopt predominantly type II β-turn conformation. We envisage that our investigation is of importance for the development of new fluorescent donor-acceptor unnatural amino acids a pair of which can be exploited for generating fluorescent peptidomimetic probe of interesting photophysical property for applications in studying peptide-protein interaction.

  2. Geomagnetic properties of Proxima Centauri b analogues

    CERN Document Server

    Zuluaga, Jorge I

    2016-01-01

    The recent discovery of a planet around the closest star, Proxima Centauri, could represent a quantum leap on the testability of models in exoplanet sciences. Unlike any other discovered exoplanet, models of planetary processes in Proxima b could be contrasted against near future telescopic observations and far future in-situ measurements. In this paper we study the geomagnetic properties of Proxima b analogues, namely, solid planets with masses close but larger than Earth's mass, periods of rotation of several days and habitable surface conditions. Assuming different planetary masses, bulk compositions and periods of rotations, we calculate for each planetary analogue its radius, heat flux, time of inner core formation, dynamo lifetime and minimum dipole magnetic moment. We find that most ($\\gtrsim$70\\%) Proxima b analogues develop intrinsic dynamos that last at least 3 Gyr, although only half of them are older than the present age of the host star ($4-6$ Gyr). Relying in our planetary evolution models, we p...

  3. Synthesis and anticancer evaluation of spermatinamine analogues

    KAUST Repository

    Moosa, Basem

    2016-02-04

    Spermatinamine was isolated from an Australian marine sponge, Pseudoceratina sp. as an inhibitor of isoprenylcystiene carboxyl methyltransferase (Icmt), an attractive and novel anticancer target. Herein, we report the synthesis of spermatinamine analogues and their cytotoxic evaluation against three human cancer cell lines i.e. cervix adenocarcinoma (HeLa), breast adenocarcinoma (MCF-7), and prostate carcinoma (DU145). Analogues 12, 14 and 15 were found to be the most potent against one or more cell lines with the IC50 values in the range of 5 - 10 μM. The obtained results suggested that longer polyamine linker along with aromatic oxime substitution provided the most potent analogue compounds against cancer cell lines.

  4. Benzoylphenylurea sulfur analogues with potent antitumor activity.

    Science.gov (United States)

    Hallur, Gurulingappa; Jimeno, Antonio; Dalrymple, Susan; Zhu, Tao; Jung, M Katherine; Hidalgo, Manuel; Isaacs, John T; Sukumar, Saraswati; Hamel, Ernest; Khan, Saeed R

    2006-04-06

    A novel series of BPU analogues were synthesized and evaluated for antitumor activity. In particular, BPU sulfur analogues 6n and 7d were shown to possess up to 10-fold increased potency, when compared to 1 (NSC-639829), against cancer cell lines. 6n was more effective than 1 in causing apoptosis of MCF-7 cells. When compared to other drugs with a similar mechanism of action, 6n retained significant ability to inhibit tubulin assembly, with an IC(50) of 2.1 microM.

  5. Theoretical Study of the Photophysics of 8-Vinylguanine, an Isomorphic Fluorescent Analogue of Guanine.

    Science.gov (United States)

    Kochman, Michał A; Pola, Martina; Miller, R J Dwayne

    2016-08-11

    Paving the way for the application of the algebraic-diagrammatic construction scheme of second-order (ADC(2)) to systems based on the guanine chromophore, we demonstrate the this excited-state electronic structure method provides a realistic description of the photochemistry of 9H-guanine, in close agreement with the benchmark provided by the CASPT2 method. We then proceed to apply the ADC(2) method to the photochemistry of 8-vinylguanine (8vG), a minimally modified analogue of guanine which, unlike the naturally occurring nucleobase, displays intense fluorescence, indicative of a much longer-lived excited electronic state. The emissive electronic state of 8vG is identified as an ππ*-type intramolecular charge transfer (ICT) state, in which a charge of roughly -0.2 e is transferred from the guanine moiety onto the vinyl substituent. The main radiationless deactivation pathway competing with fluorescence is predicted to involve the molecule leaving the minimum on the ICT ππ* state, and reaching a region of the S1 adiabatic state where it resembles the La ππ* state of unmodified 9H-guanine. The topology of the La ππ* region of the S1 state favors subsequent internal conversion at a crossing seam with the ground electronic state. The sensitivity of this process to environment polarity may explain the experimentally observed fluorescence quenching of 8vG upon incorporation in single- and double-stranded DNA.

  6. Photochemical degradation of chromophoric-dissolved organic matter exposed to simulated UV-B and natural solar radiation

    NARCIS (Netherlands)

    Zhang, Y.; Liu, M.; Qin, B.; Feng, S.

    2009-01-01

    Photochemical degradation of chromophoric-dissolved organic matter (CDOM) by UV-B radiation decreases CDOM absorption in the UV region and fluorescence intensity, and alters CDOM composition. CDOM absorption, fluorescence, and the spectral slope indicating the CDOM composition were studied using 0.2

  7. Phytochrome from Agrobacterium tumefaciens has unusual spectral properties and reveals an N-terminal chromophore attachment site.

    Science.gov (United States)

    Lamparter, Tilman; Michael, Norbert; Mittmann, Franz; Esteban, Berta

    2002-09-03

    Phytochromes are photochromic photoreceptors with a bilin chromophore that are found in plants and bacteria. The soil bacterium Agrobacterium tumefaciens contains two genes that code for phytochrome-homologous proteins, termed Agrobacterium phytochrome 1 and 2 (Agp1 and Agp2). To analyze its biochemical and spectral properties, Agp1 was purified from the clone of an E. coli overexpressor. The protein was assembled with the chromophores phycocyanobilin and biliverdin, which is the putative natural chromophore, to photoactive holoprotein species. Like other bacterial phytochromes, Agp1 acts as light-regulated His kinase. The biliverdin adduct of Agp1 represents a previously uncharacterized type of phytochrome photoreceptor, because photoreversion from the far-red absorbing form to the red-absorbing form is very inefficient, a feature that is combined with a rapid dark reversion. Biliverdin bound covalently to the protein; blocking experiments and site-directed mutagenesis identified a Cys at position 20 as the binding site. This particular position is outside the region where plant and some cyanobacterial phytochromes attach their chromophore and thus represents a previously uncharacterized binding site. Sequence comparisons imply that the region around Cys-20 is a ring D binding motif in phytochromes.

  8. Dynamics of chromophoric dissolved organic matter in Mandovi and Zuari estuaries — A study through in situ and satellite data

    Digital Repository Service at National Institute of Oceanography (India)

    Menon, H.B.; Sangekar, N.P.; Lotliker, A.A; Vethamony, P.

    The spatial and temporal distribution of absorption of chromophoric dissolved organic matter at 440 nm (a sub (CDOM) (440)) in the Mandovi and Zuari estuaries situated along the west coast of India, has been analysed. The study was carried out using...

  9. Catalytic effect of free iron ions and heme-iron on chromophore oxidation of a polyene antibiotic amphotericin B

    Science.gov (United States)

    Czernel, Grzegorz; Typek, Rafał; Klimek, Katarzyna; Czuryło, Aleksandra; Dawidowicz, Andrzej L.; Gagoś, Mariusz

    2016-05-01

    Owing to the presence of a chromophore in the amphotericin B (AmB) structure, the molecule can undergo the oxidation process. In this research, AmB chromophore oxidation was catalysed by iron ions (iron(III) chloride (FeCl3), pH 2.5) and by heme-iron (methemoglobin (HbFe(III)), and hemin (heme-Fe(III)) at pH 7.0). Additionally, we compared oxidation processes induced by the aforementioned oxidizing agents with autoxidation by dioxygen (O2) naturally occurring in a sample. The effects of the interaction of the oxidizing agents with AmB were analysed using molecular spectroscopies (electronic absorption (UV-Vis), fluorescence) and LC-MS. The use of a 1,10-phenanthroline (phen) chelator facilitated unambiguous determination of the oxidative effect of free iron(III) ions (FeIII) in an acidic solution on the AmB molecules. Also, the changes in the spectra of fluorescence emission centred at ∼470 nm indicate iron-catalysed processes of AmB chromophore oxidation. Unexpectedly, we found a similar spectroscopic effect for AmB induced by methemoglobin and hemin at pH 7.0. Methemoglobin and hemin at a concentration of 8 × 10-7 M (physiological) significantly increases the rate of the processes of AmB chromophore oxidation relative to the process of autoxidation.

  10. Synthesis and near-infrared characteristics of novel perylene bisimide dyes bay-functionalized with naphthalimide chromophores

    Institute of Scientific and Technical Information of China (English)

    Bo Gao; Yang Li; He Tian

    2007-01-01

    Novel perylene bisimide dyes bay-functionalized with naphthalimide chromophores have been prepared conveniently by coupling of 1,8-naphthalimide and dibromoperylene bisimides. Their optical properties were investigated by UV-vis and fluorescence spectroscopy. The absorption spectra of these compounds showed wide spectral responses from 300 to 700 nm,which would be potentials for application as organic solar cells.

  11. Synthesis, crystals of centrosymmetric triphenylamine chromophores bearing prodigious two-photon absorption cross-section and biological imaging

    Science.gov (United States)

    Wang, Shichao; Xu, Shasha; Wang, Yiming; Tian, Xiaohe; Zhang, Yujin; Wang, Chuankui; Wu, Jieying; Yang, Jiaxiang; Tian, Yupeng

    2017-02-01

    Two centrosymmetric D-π-D type triphenylamine chromophores with long π-conjugated bridge and strong electron-donating moiety were designed, synthesized and fully characterized. The crystal analysis revealed that multiple Csbnd H ⋯ π interactions existed in two chromophores, which played a crucial role in generating molecular 1D chains and 2D layers structures. Linear and nonlinear optical properties of the chromophores were systematically investigated with the aid of theoretical calculations. Two chromophores both exhibited intense and wide-dispersed one-photon/two-photon excited fluorescence, bear prodigious 2PA cross section (δ). Especially for Dye2, with ethyoxyl groups, displayed the strong 2PA activity, large cross-sections (δmax > 16,000 GM) and high NLO efficiency (δmax/MW > 16 GM/(g·mol)) in the range of 680-830 nm in DMF. In addition, one- and two-photon fluorescence microscopy images of HepG2 cells incubated with Dye2 were obtained and found that Dye2 could effectively uptake toward living cells and display a uniformly localized in cytosolic space.

  12. Ultrafast dual photoresponse of isolated biological chromophores: link to the photoinduced mode-specific non-adiabatic dynamics in proteins.

    Science.gov (United States)

    Bochenkova, Anastasia V; Andersen, Lars H

    2013-01-01

    The anionic wild-type Green Fluorescent Protein (GFP) chromophore defines an entire class of naturally occurring chromophores, which are based on the oxydized tyrosine side chain. The GFP chromophore exhibits an enriched photoinduced non-adiabatic dynamics in the multiple excited-state decay channels. Deactivation includes vibrational resonant photodetachment and internal conversion. Here, we provide detailed insight into the efficiency of different vibrational modes in promoting a selective photoresponse in the bare GFP chromophore anion. We introduce a general theoretical model that is capable of accounting for the alternative non-equivalent pathways in internal conversion, and we outline the factors, by which the photo-initiated response may be altered in this channel. The topography around the planar minimum in S1 and the two distinct types of the S1/S0 conical intersections obtained through high-level ab initio calculations provide direct support to the proposed model. There are mode-selective ways to control the photoresponse and to direct it towards a single excited-state decay channel. By tuning the excitation wavelength, the photoresponse may be directed towards the ultrafast non-statistical electron emission coupled with vibrational (de)coherence, whereas a vibrational pre-excitation in the ground state may lead to the ultrafast non-statistical internal conversion through a conical intersection. We also discuss the implication of our results to the photo-initiated non-adiabatic dynamics in the proteins.

  13. Analogue alternative the electronic analogue computer in Britain and the USA, 1930-1975

    CERN Document Server

    Small, James S

    2013-01-01

    We are in the midst of a digital revolution - until recently, the majority of appliances used in everyday life have been developed with analogue technology. Now, either at home or out and about, we are surrounded by digital technology such as digital 'film', audio systems, computers and telephones. From the late 1940s until the 1970s, analogue technology was a genuine alternative to digital, and the two competing technologies ran parallel with each other. During this period, a community of engineers, scientists, academics and businessmen continued to develop and promote the analogue computer.

  14. Determination of optimal source-detector separation in measuring chromophores in layered tissue with diffuse reflectance

    Institute of Scientific and Technical Information of China (English)

    Yunhan Luo; Houxin Cui; Xiaoyu Gu; Rong Liu; Kexin Xu

    2005-01-01

    Based on analysis of the relation between mean penetration depth and source-detector separation in a threelayer model with the method of Monte-Carlo simulation, an optimal source-detector separation is derived from the mean penetration depth referring to monitoring the change of chromophores concentration of the sandwiched layer. In order to verify the separation, we perform Monte-Carlo simulations with varied absorption coefficient of the sandwiched layer. All these diffuse reflectances are used to construct a calibration model with the method of partial least square (PLS). High correlation coefficients and low root mean square error of prediction (RMSEP) at the optimal separation have confirmed correctness of the selection. This technique is expected to show light on noninvasive diagnosis of near-infrared spectroscopy.

  15. Synthesis of Dendrimer Containing Dialkylated-fluorene Unit as a Core Chromophore via Click Chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Han, Seung Choul; Lee, Jae Wook [Dong-A University, Busan (Korea, Republic of); Jin, Sung Ho [Pusan National University, Busan (Korea, Republic of)

    2012-01-15

    The convergent synthetic strategy for the emissive dendrimers having the chromophore at core via the coppercatalyzed 1,3-dipolar cycloaddition reaction between alkyne and azide was described. 2,7-Diazido-9,9-dioctyl- 9H-fluorene, designed to serve as the core in dendrimer, was stitched with the alkyne-functionalized Frechettype and PAMAM dendrons by the click chemistry leading to the formation of the corresponding fluorescent dendrimers in high yields. The preliminary photoluminescence studies indicated that 2,7-diazido-9,9-dioctyl- 9H-fluorene showed no fluorescence due to the quenching effect from the electron-rich α-nitrogen of the azido group but the dendrimers fluoresced due to the elimination of the quenching through the formation of the triazole ring.

  16. PHOTOCHROMISM AND LUMINESCENCE OF DOPANT CHROMOPHORES THROUGH TWO-PHOTON IONIZATION IN POLYMER FILMS

    Institute of Scientific and Technical Information of China (English)

    Masahide Yamamoto; Hideo Ohkita; Shinzaburo Ito

    2001-01-01

    Two-photon ionization and recombination processes of an aromatic chromophore doped in polymer films were studied and the features of these processes were discussed in relation to photofunctional polymers. An aromatic molecule having low ionization potential, e.g., N,N,N',N'-tetramethyl-p-phenylene diamine doped in poly(methyl methacrylate)(PMMA) film was easily photoionized by intense laser light excitation, giving a colored radical cation (photochromism) and a trapped electron in PMMA matrix. As a reversed process, the radical cation recombined with the trapped electron, showing discoloration and emitting luminescence, either isothermal luminescence (ITL), or thermoluminescence (TL). In this report,ITL and TL through the charge recombination process were studied and the luminescence was suggested as a mean of the read-out of photorecording.

  17. Analysis of an algebraic model for the chromophore vibrations of CF$_3$CHFI

    CERN Document Server

    Jung, C; Taylor, H S

    2004-01-01

    We extract the dynamics implicit in an algebraic fitted model Hamiltonian for the hydrogen chromophore's vibrational motion in the molecule $CF_3CHFI$. The original model has 4 degrees of freedom, three positions and one representing interbond couplings. A conserved polyad allows the reduction to 3 degrees of freedom. For most quantum states we can identify the underlying motion that when quantized gives the said state. Most of the classifications, identifications and assignments are done by visual inspection of the already available wave function semiclassically transformed from the number representation to a representation on the reduced dimension toroidal configuration space corresponding to the classical action and angle variables. The concentration of the wave function density to lower dimensional subsets centered on idealized simple lower dimensional organizing structures and the behavior of the phase along such organizing centers already reveals the atomic motion. Extremely little computational work is...

  18. Alphabet-Inspired Design of (Hetero)Aromatic Push-Pull Chromophores.

    Science.gov (United States)

    Klikar, Milan; Solanke, Parmeshwar; Tydlitát, Jiří; Bureš, Filip

    2016-08-01

    Push-pull molecules represent a unique and fascinating class of organic π-conjugated materials. Herein, we provide a summary of their recent extraordinary design inspired by letters of the alphabet, especially focusing on H-, L-, T-, V-, X-, and Y-shaped molecules. Representative structures from each class were presented and their fundamental properties and prospective applications were discussed. In particular, emphasis is given to molecules recently prepared in our laboratory with T-, X-, and Y-shaped arrangements based on indan-1,3-dione, benzene, pyridine, pyrazine, imidazole, and triphenylamine. These push-pull molecules turned out to be very efficient charge-transfer chromophores with tunable properties suitable for second-order nonlinear optics, two-photon absorption, reversible pH-induced and photochromic switching, photocatalysis, and intercalation.

  19. Synthesis and nonlinear optical properties of copolymers of fluoro-containing bisphenol A and chromophores

    Institute of Scientific and Technical Information of China (English)

    Jie Ping Shi; Hui Yang; Li Wei; Hong Wen Hu; Guo Yuan Lu

    2011-01-01

    A series of new fluoro-containing copolymers have been synthesized by a Mitsunobu reaction with 4,4'-(hexafluoro-isopropylidene)bisphenol A (6FBPA) and the corresponding N, N-dihydroxyethylaminoaryl azo or ring-locked triene compounds, which have high thermal stability and good solubility in organic solvents. The nonlinear optical (NLO) measurements made by Marker fringe method at 1064 nm indicate that the copolymers embedded with the ring-locked triene and azo chromophores exhibit higher macroscopic nonlinear optical coefficient (70.2 pm/V and 26.5-34.6 pm/V, respectively). Thermal analysis and UV-visible absorption spectra show that the copolymers have good thermal stability (Td = 264-319 ℃) and optical transparency (λmax<500nm).

  20. Three-photon absorption in a push-pull type chromophore containing tricyanofuran acceptor

    Institute of Scientific and Technical Information of China (English)

    Yan Ji; Ying Qian; Zhi Qiang Zhou; Wei Lu; Yi Ping Cui

    2012-01-01

    Three-photon absorption (3PA) of a push-pull chromophore,2-(3-cyano-(3-(4-(dimethylamino)styryl)-5,5-dimethylcyclohex-2-enylidene)methyl)-5,5-dimethylfuran-2-ylidene) malononitrile (CFM) including TCF group was measured by the nonlinear transmission method using a femto-second Ti:Sapphire oscillator-amplifier laser system.Its three-photon absorption cross-sections at 1300 nm were 36.8 × 10-79 cm6 s2 in the solution of DMF and 12.3 × 10-79 cm6 s2 in the solution of CH2Cl2,respectively.The large values were got by experiments in this paper,which is a new exploration for these kinds of materials.The molecule has the potential application foreground of 3PA areas and optical power limiting.

  1. Detailed theoretical investigation of excited-state intramolecular proton transfer mechanism of a new chromophore II

    Science.gov (United States)

    Cui, Yanling; Li, Yafei; Dai, Yumei; Verpoort, Francis; Song, Peng; Xia, Lixin

    2016-02-01

    In the present work, TDDFT has been used to investigate the excited state intramolecular proton transfer (ESIPT) mechanism of a new chromophore II [Sensors and Actuators B: Chemical. 202 (2014) 1190]. The calculated absorption and fluorescence spectra agree well with experimental results. In addition, two types of II configurations are found in the first excited state (S1), which can be ascribed to the ESIPT reaction. Based on analysis of the calculated infrared (IR) spectra of O-H stretching vibration as well as the hydrogen bonding energies, the strengthening of the hydrogen bond in the S1 state has been confirmed. The frontier molecular orbitals (MOs), Hirshfeld charge distribution and the Natural bond orbital (NBO) have also been analyzed, which displays the tendency of the ESIPT process. Finally, potential energy curves of the S0 and S1 states were constructed, demonstrating that the ESIPT reaction can be facilitated based on the photo-excitation.

  2. Ochres and earths: Matrix and chromophores characterization of 19th and 20th century artist materials

    Science.gov (United States)

    Montagner, Cristina; Sanches, Diogo; Pedroso, Joana; Melo, Maria João; Vilarigues, Márcia

    2013-02-01

    The present paper describes the main results obtained from the characterization of a wide range of natural and synthetic ochre samples used in Portugal from the 19th to the 20th century, including powder and oil painting samples. The powder ochre samples came from several commercial distributors and from the collection of Joaquim Rodrigo (1912-1997), a leading Portuguese artist, particularly active during the sixties and seventies. The micro-samples of oil painting tubes came from the Museu Nacional de Arte Contemporânea-Museu do Chiado (National Museum of Contemporary Art-Chiado Museum) in Lisbon and were used by Columbano Bordalo Pinheiro (1857-1929), one of the most prominent naturalist Portuguese painters. These tubes were produced by the main 19th century colourmen: Winsor & Newton, Morin et Janet, Maison Merlin, and Lefranc. The samples have been studied using μ-Fourier Transform Infrared Spectroscopy (μ-FTIR), Raman microscopy, μ-Energy Dispersive X-ray fluorescence (μ-EDXRF), and X-ray diffraction (XRD). The analyzed ochres were found to be a mixture of several components: iron oxides and hydroxides in matrixes with kaolinite, gypsum and chalk. The results obtained allowed to identify and characterize the ochres according to their matrix and chromophores. The main chromophores where identified by Raman microscopy as being hematite, goethite and magnetite. The infrared analysis of the ochre samples allowed to divide them into groups, according to the composition of the matrix. It was possible to separate ochres containing kaolinite matrix and/or sulfate matrix from ochres where only iron oxides and/or hydroxides were detected. μ-EDXRF and Raman were the best techniques to identify umber, since the presence of elements such as manganese is characteristic of these pigments. μ-EDXRF also revealed the presence of significant amounts of arsenic in all Sienna tube paints.

  3. Chromophore dynamics in the PYP photocycle from femtosecond stimulated Raman spectroscopy.

    Science.gov (United States)

    Creelman, Mark; Kumauchi, Masato; Hoff, Wouter D; Mathies, Richard A

    2014-01-23

    Femtosecond stimulated Raman spectroscopy (FSRS) is used to examine the structural dynamics of the para-hydroxycinnamic acid (HCA) chromophore during the first 300 ps of the photoactive yellow protein (PYP) photocycle, as the system transitions from its vertically excited state to the early ground state cis intermediate, I0. A downshift in both the C7═C8 and C1═O stretches upon photoexcitation reveals that the chromophore has shifted to an increasingly quinonic form in the excited state, indicating a charge shift from the phenolate moiety toward the C9═O carbonyl, which continues to increase for 170 fs. In addition, there is a downshift in the C9═O carbonyl out-of-plane vibration on an 800 fs time scale as PYP transitions from its excited state to I0, indicating that weakening of the hydrogen bond with Cys69 and out-of-plane rotation of the C9═O carbonyl are key steps leading to photoproduct formation. HOOP intensity increases on a 3 ps time scale during the formation of I0, signifying distortion about the C7═C8 bond. Once on the I0 surface, the C7═C8 and C1═O stretches blue shift, indicating recovery of charge to the phenolate, while persistent intensity in the HOOP and carbonyl out-of-plane modes reveal HCA to be a cissoid structure with significant distortion about the C7═C8 bond and of C9═O out of the molecular plane.

  4. Differential effects of mutations in the chromophore pocket of recombinant phytochrome on chromoprotein assembly and Pr-to-Pfr photoconversion.

    Science.gov (United States)

    Remberg, A; Schmidt, P; Braslavsky, S E; Gärtner, W; Schaffner, K

    1999-11-01

    Site-directed mutagenesis was performed with the chromophore-bearing N-terminal domain of oat phytochrome A apoprotein (amino acid residues 1-595). Except for Trp366, which was replaced by Phe (W366F), all the residues exchanged are in close proximity to the chromophore-binding Cys321 (i.e. P318A, P318K, H319L, S320K, H322L and the double mutant L323R/Q324D). The mutants were characterized by their absorption maxima, and the kinetics of chromophore-binding and the Pr-->Pfr conversion. The strongest effect of mutation on the chromoprotein assembly, leading to an almost complete loss of the chromophore binding capability, was found for the exchanges of His322 by Leu (H322L) and Pro318 by Lys (P318K), whereas a corresponding alanine mutant (P318A) showed wild-type behavior. The second histidine (H319) is also involved in chromophore fixation, as indicated by a slower assembly rate upon mutation (H319L). For the other mutants, an assembly process very similar to that of the wild-type protein was found. The light-induced Pr-->Pfr conversion kinetics is altered in the mutations H319L and S320K and in the double mutant L323R/Q324D, all of which exhibited a significantly faster I700 decay and accelerated Pfr formation. P318 is also involved in the Pr-->Pfr conversion, the millisecond steps (formation of Pfr) being significantly slower for P318A. Lacking sufficient amounts of W366F, assembly kinetics could not be determined in this case, while the fully assembled mutant underwent the Pr-->Pfr conversion with kinetics similar to wild-type protein.

  5. Synthesis and antimicrobial activity of squalamine analogue.

    Science.gov (United States)

    Kim, H S; Choi, B S; Kwon, K C; Lee, S O; Kwak, H J; Lee, C H

    2000-08-01

    Synthesis and antimicrobial activity of squalamine analogue 2 are reported. The synthesis of 2 was accomplished from bisnoralcohol 3. The spermidine moiety was introduced via reductive amination of an appropriately functionalized 3beta-aminosterol with spermidinyl aldehyde 17 utilizing sodium triacetoxyborohydride as the reducing agent. Compound 2 shows weaker antimicrobial activity than squalamine.

  6. Dumb holes: analogues for black holes.

    Science.gov (United States)

    Unruh, W G

    2008-08-28

    The use of sonic analogues to black and white holes, called dumb or deaf holes, to understand the particle production by black holes is reviewed. The results suggest that the black hole particle production is a low-frequency and low-wavenumber process.

  7. Solanapyrone analogues from a Hawaiian fungicolous fungus

    Science.gov (United States)

    Four new solanayrone analogues (solanapyrones J-M; 1-4) have been isolated from an unidentified fungicolous fungus collected in Hawaii. The structures and relative configurations of these compounds were determined by analysis of ID NMR, 2D NMR, and MS data. Solanapyrone J(1) showed antifungal acti...

  8. Prussian Blue Analogues of Reduced Dimensionality

    NARCIS (Netherlands)

    Gengler, Regis Y. N.; Toma, Luminita M.; Pardo, Emilio; Lloret, Francesc; Ke, Xiaoxing; Van Tendeloo, Gustaaf; Gournis, Dimitrios; Rudolf, Petra

    2012-01-01

    Mixed-valence polycyanides (Prussian Blue analogues) possess a rich palette of properties spanning from room-temperature ferromagnetism to zero thermal expansion, which can be tuned by chemical modifications or the application of external stimuli (temperature, pressure, light irradiation). While mol

  9. [Dmt(1)]DALDA analogues modified with tyrosine analogues at position 1.

    Science.gov (United States)

    Cai, Yunxin; Lu, Dandan; Chen, Zhen; Ding, Yi; Chung, Nga N; Li, Tingyou; Schiller, Peter W

    2016-08-01

    Analogues of [Dmt(1)]DALDA (H-Dmt-d-Arg-Phe-Lys-NH2; Dmt=2',6'-dimethyltyrosine), a potent μ opioid agonist peptide with mitochondria-targeted antioxidant activity were prepared by replacing Dmt with various 2',6'-dialkylated Tyr analogues, including 2',4',6'-trimethyltyrosine (Tmt), 2'-ethyl-6'-methyltyrosine (Emt), 2'-isopropyl-6'-methyltyrosine (Imt) and 2',6'-diethyltyrosine (Det). All compounds were selective μ opioid agonists and the Tmt(1)-, Emt(1) and Det(1)-analogues showed subnanomolar μ opioid receptor binding affinities. The Tmt(1)- and Emt(1)-analogues showed improved antioxidant activity compared to the Dmt(1)-parent peptide in the DPPH radical-scavenging capacity assay, and thus are of interest as drug candidates for neuropathic pain treatment.

  10. Design of Thymidine Analogues Targeting Thymidilate Kinase of Mycobacterium tuberculosis

    Directory of Open Access Journals (Sweden)

    Luc Calvin Owono Owono

    2013-01-01

    Full Text Available We design here new nanomolar antituberculotics, inhibitors of Mycobacterium tuberculosis thymidine monophosphate kinase (TMPKmt, by means of structure-based molecular design. 3D models of TMPKmt-inhibitor complexes have been prepared from the crystal structure of TMPKmt cocrystallized with the natural substrate deoxythymidine monophosphate (dTMP (1GSI for a training set of 15 thymidine analogues (TMDs with known activity to prepare a QSAR model of interaction establishing a correlation between the free energy of complexation and the biological activity. Subsequent validation of the predictability of the model has been performed with a 3D QSAR pharmacophore generation. The structural information derived from the model served to design new subnanomolar thymidine analogues. From molecular modeling investigations, the agreement between free energy of complexation (ΔΔGcom and Ki values explains 94% of the TMPKmt inhibition (pKi=-0.2924ΔΔGcom+3.234;R2=0.94 by variation of the computed ΔΔGcom and 92% for the pharmacophore (PH4 model (pKi=1.0206×pKipred-0.0832,  R2=0.92. The analysis of contributions from active site residues suggested substitution at the 5-position of pyrimidine ring and various groups at the 5′-position of the ribose. The best inhibitor reached a predicted Ki of 0.155 nM. The computational approach through the combined use of molecular modeling and PH4 pharmacophore is helpful in targeted drug design, providing valuable information for the synthesis and prediction of activity of novel antituberculotic agents.

  11. A q-analogue of the four functions theorem

    OpenAIRE

    Christofides, Demetres

    2009-01-01

    In this article we give a proof of a q-analogue of the celebrated four functions theorem. This analogue was conjectured by Bjorner and includes as special cases both the four functions theorem and also Bjorner's q-analogue of the FKG inequality.

  12. Tryptophan analogues. 1. Synthesis and antihypertensive activity of positional isomers.

    Science.gov (United States)

    Safdy, M E; Kurchacova, E; Schut, R N; Vidrio, H; Hong, E

    1982-06-01

    A series of tryptophan analogues having the carboxyl function at the beta-position was synthesized and tested for antihypertensive activity. The 5-methoxy analogue 46 exhibited antihypertensive activity in the rat via the oral route and was much more potent than the normal tryptophan analogue. The methyl ester was found to be a critical structural feature for activity.

  13. Analogue VLSI for probabilistic networks and spike-time computation.

    Science.gov (United States)

    Murray, A

    2001-02-01

    The history and some of the methods of analogue neural VLSI are described. The strengths of analogue techniques are described, along with residual problems to be solved. The nature of hardware-friendly and hardware-appropriate algorithms is reviewed and suggestions are offered as to where analogue neural VLSI's future lies.

  14. Investigation of Serine-Proteinase-Catalyzed Peptide Splicing in Analogues of Sunflower Trypsin Inhibitor 1 (SFTI-1).

    Science.gov (United States)

    Karna, Natalia; Łęgowska, Anna; Malicki, Stanisław; Dębowski, Dawid; Golik, Przemysław; Gitlin, Agata; Grudnik, Przemysław; Wladyka, Benedykt; Brzozowski, Krzysztof; Dubin, Grzegorz; Rolka, Krzysztof

    2015-09-21

    Serine-proteinase-catalyzed peptide splicing was demonstrated in analogues of the trypsin inhibitor SFTI-1: both single peptides and two-peptide chains (C- and N-terminal peptide chains linked by a disulfide bridge). In the second series, peptide splicing with catalytic amount of proteinase was observed only when formation of acyl-enzyme intermediate was preceded by hydrolysis of the substrate Lys-Ser peptide bond. Here we demonstrate that with an equimolar amount of the proteinase, splicing occurs in all the two-peptide-chain analogues. This conclusion was supported by high resolution crystal structures of selected analogues in complex with trypsin. We showed that the process followed a direct transpeptidation mechanism. Thus, the acyl-enzyme intermediate was formed and was immediately used for a new peptide bond formation; products associated with the hydrolysis of the acyl-enzyme were not observed. The peptide splicing was sequence- not structure-specific.

  15. Heat Capacity Changes for Transition-State Analogue Binding and Catalysis with Human 5'-Methylthioadenosine Phosphorylase.

    Science.gov (United States)

    Firestone, Ross S; Cameron, Scott A; Karp, Jerome M; Arcus, Vickery L; Schramm, Vern L

    2017-02-17

    Human 5'-methylthioadenosine phosphorylase (MTAP) catalyzes the phosphorolysis of 5'-methylthioadenosine (MTA). Its action regulates cellular MTA and links polyamine synthesis to S-adenosylmethionine (AdoMet) salvage. Transition state analogues with picomolar dissociation constants bind to MTAP in an entropically driven process at physiological temperatures, suggesting increased hydrophobic character or dynamic structure for the complexes. Inhibitor binding exhibits a negative heat capacity change (-ΔCp), and thus the changes in enthalpy and entropy upon binding are strongly temperature-dependent. The ΔCp of inhibitor binding by isothermal titration calorimetry does not follow conventional trends and is contrary to that expected from the hydrophobic effect. Thus, ligands of increasing hydrophobicity bind with increasing values of ΔCp. Crystal structures of MTAP complexed to transition-state analogues MT-DADMe-ImmA, BT-DADMe-ImmA, PrT-ImmA, and a substrate analogue, MT-tubercidin, reveal similar active site contacts and overall protein structural parameters, despite large differences in ΔCp for binding. In addition, ΔCp values are not correlated with Kd values. Temperature dependence of presteady state kinetics revealed the chemical step for the MTAP reaction to have a negative heat capacity for transition state formation (-ΔCp(‡)). A comparison of the ΔCp(‡) for MTAP presteady state chemistry and ΔCp for inhibitor binding revealed those transition-state analogues most structurally and thermodynamically similar to the transition state. Molecular dynamics simulations of MTAP apoenzyme and complexes with MT-DADMe-ImmA and MT-tubercidin show small, but increased dynamic motion in the inhibited complexes. Variable temperature CD spectroscopy studies for MTAP-inhibitor complexes indicate remarkable protein thermal stability (to Tm = 99 °C) in complexes with transition-state analogues.

  16. Fe(II)-Polypyridines as Chromophores in Dye-Sensitized Solar Cells: A Computational Perspective.

    Science.gov (United States)

    Jakubikova, Elena; Bowman, David N

    2015-05-19

    Over the past two decades, dye-sensitized solar cells (DSSCs) have become a viable and relatively cheap alternative to conventional crystalline silicon-based systems. At the heart of a DSSC is a wide band gap semiconductor, typically a TiO2 nanoparticle network, sensitized with a visible light absorbing chromophore. Ru(II)-polypyridines are often utilized as chromophores thanks to their chemical stability, long-lived metal-to-ligand charge transfer (MLCT) excited states, tunable redox potentials, and near perfect quantum efficiency of interfacial electron transfer (IET) into TiO2. More recently, coordination compounds based on first row transition metals, such as Fe(II)-polypyridines, gained some attention as potential sensitizers in DSSCs due to their low cost and abundance. While such complexes can in principle sensitize TiO2, they do so very inefficiently since their photoactive MLCT states undergo intersystem crossing (ISC) into low-lying metal-centered states on a subpicosecond time scale. Competition between the ultrafast ISC events and IET upon initial excitation of Fe(II)-polypyridines is the main obstacle to their utilization in DSSCs. Suitability of Fe(II)-polypyridines to serve as sensitizers could therefore be improved by adjusting relative rates of the ISC and IET processes, with the goal of making the IET more competitive with ISC. Our research program in computational inorganic chemistry utilizes a variety of tools based on density functional theory (DFT), time-dependent density functional theory (TD-DFT) and quantum dynamics to investigate structure-property relationships in Fe(II)-polypyridines, specifically focusing on their function as chromophores. One of the difficult problems is the accurate determination of energy differences between electronic states with various spin multiplicities (i.e., (1)A, (1,3)MLCT, (3)T, (5)T) in the ISC cascade. We have shown that DFT is capable of predicting the trends in the energy ordering of these electronic

  17. Optimization of propafenone analogues as antimalarial leads.

    Science.gov (United States)

    Lowes, David J; Guiguemde, W Armand; Connelly, Michele C; Zhu, Fangyi; Sigal, Martina S; Clark, Julie A; Lemoff, Andrew S; Derisi, Joseph L; Wilson, Emily B; Guy, R Kiplin

    2011-11-10

    Propafenone, a class Ic antiarrythmic drug, inhibits growth of cultured Plasmodium falciparum. While the drug's potency is significant, further development of propafenone as an antimalarial would require divorcing the antimalarial and cardiac activities as well as improving the pharmacokinetic profile of the drug. A small array of propafenone analogues was designed and synthesized to address the cardiac ion channel and PK liabilities. Testing of this array revealed potent inhibitors of the 3D7 (drug sensitive) and K1 (drug resistant) strains of P. falciparum that possessed significantly reduced ion channel effects and improved metabolic stability. Propafenone analogues are unusual among antimalarial leads in that they are more potent against the multidrug resistant K1 strain of P. falciparum compared to the 3D7 strain.

  18. Spectroscopic study of solar twins and analogues

    CERN Document Server

    Datson, Juliet; Portinari, Laura

    2014-01-01

    Context. Many large stellar surveys have been and are still being carried out, providing huge amounts of data, for which stellar physical parameters will be derived. Solar twins and analogues provide a means to test the calibration of these stellar catalogues because the Sun is the best-studied star and provides precise fundamental parameters. Solar twins should be centred on the solar values. Aims. This spectroscopic study of solar analogues selected from the Geneva-Copenhagen Survey (GCS) at a resolution of 48,000 provides effective temperatures and metallicities for these stars. We test whether our spectroscopic parameters, as well as the previous photometric calibrations, are properly centred on the Sun. In addition, we search for more solar twins in our sample. Methods. The methods used in this work are based on literature methods for solar twin searches and on methods we developed in previous work to distinguish the metallicity-temperature degeneracies in the differential comparison of spectra of solar ...

  19. Holographic Fluids with Vorticity and Analogue Gravity

    CERN Document Server

    Leigh, Robert G; Petropoulos, P Marios

    2012-01-01

    We study holographic three-dimensional fluids with vorticity in local equilibrium and discuss their relevance to analogue gravity systems. The Fefferman-Graham expansion leads to the fluid's description in terms of a comoving and rotating Papapetrou-Randers frame. A suitable Lorentz transformation brings the fluid to the non-inertial Zermelo frame, which clarifies its interpretation as moving media for light/sound propagation. We apply our general results to the Lorentzian Kerr-AdS_4 and Taub-NUT-AdS_4 geometries that describe fluids in cyclonic and vortex flows respectively. In the latter case we associate the appearance of closed timelike curves to analogue optical horizons. In addition, we derive the classical rotational Hall viscosity of three-dimensional fluids with vorticity. Our formula remarkably resembles the corresponding result in magnetized plasmas.

  20. Confirmation via Analogue Simulation: A Bayesian Analysis

    CERN Document Server

    Dardashti, Radin; Thebault, Karim P Y; Winsberg, Eric

    2016-01-01

    Analogue simulation is a novel mode of scientific inference found increasingly within modern physics, and yet all but neglected in the philosophical literature. Experiments conducted upon a table-top 'source system' are taken to provide insight into features of an inaccessible 'target system', based upon a syntactic isomorphism between the relevant modelling frameworks. An important example is the use of acoustic 'dumb hole' systems to simulate gravitational black holes. In a recent paper it was argued that there exists circumstances in which confirmation via analogue simulation can obtain; in particular when the robustness of the isomorphism is established via universality arguments. The current paper supports these claims via an analysis in terms of Bayesian confirmation theory.

  1. Polyamine analogues targeting epigenetic gene regulation.

    Science.gov (United States)

    Huang, Yi; Marton, Laurence J; Woster, Patrick M; Casero, Robert A

    2009-11-04

    Over the past three decades the metabolism and functions of the polyamines have been actively pursued as targets for antineoplastic therapy. Interactions between cationic polyamines and negatively charged nucleic acids play a pivotal role in DNA stabilization and RNA processing that may affect gene expression, translation and protein activity. Our growing understanding of the unique roles that the polyamines play in chromatin regulation, and the discovery of novel proteins homologous with specific regulatory enzymes in polyamine metabolism, have led to our interest in exploring chromatin remodelling enzymes as potential therapeutic targets for specific polyamine analogues. One of our initial efforts focused on utilizing the strong affinity that the polyamines have for chromatin to create a backbone structure, which could be combined with active-site-directed inhibitor moieties of HDACs (histone deacetylases). Specific PAHAs (polyaminohydroxamic acids) and PABAs (polyaminobenzamides) polyamine analogues have demonstrated potent inhibition of the HDACs, re-expression of p21 and significant inhibition of tumour growth. A second means of targeting the chromatin-remodelling enzymes with polyamine analogues was facilitated by the recent identification of flavin-dependent LSD1 (lysine-specific demethylase 1). The existence of this enzyme demonstrated that histone lysine methylation is a dynamic process similar to other histone post-translational modifications. LSD1 specifically catalyses demethylation of mono- and di-methyl Lys4 of histone 3, key positive chromatin marks associated with transcriptional activation. Structural and catalytic similarities between LSD1 and polyamine oxidases facilitated the identification of biguanide, bisguanidine and oligoamine polyamine analogues that are potent inhibitors of LSD1. Cellular inhibition of LSD1 by these unique compounds led to the re-activation of multiple epigenetically silenced genes important in tumorigenesis. The use of

  2. Benchmarking analogue models of brittle thrust wedges

    Science.gov (United States)

    Schreurs, Guido; Buiter, Susanne J. H.; Boutelier, Jennifer; Burberry, Caroline; Callot, Jean-Paul; Cavozzi, Cristian; Cerca, Mariano; Chen, Jian-Hong; Cristallini, Ernesto; Cruden, Alexander R.; Cruz, Leonardo; Daniel, Jean-Marc; Da Poian, Gabriela; Garcia, Victor H.; Gomes, Caroline J. S.; Grall, Céline; Guillot, Yannick; Guzmán, Cecilia; Hidayah, Triyani Nur; Hilley, George; Klinkmüller, Matthias; Koyi, Hemin A.; Lu, Chia-Yu; Maillot, Bertrand; Meriaux, Catherine; Nilfouroushan, Faramarz; Pan, Chang-Chih; Pillot, Daniel; Portillo, Rodrigo; Rosenau, Matthias; Schellart, Wouter P.; Schlische, Roy W.; Take, Andy; Vendeville, Bruno; Vergnaud, Marine; Vettori, Matteo; Wang, Shih-Hsien; Withjack, Martha O.; Yagupsky, Daniel; Yamada, Yasuhiro

    2016-11-01

    We performed a quantitative comparison of brittle thrust wedge experiments to evaluate the variability among analogue models and to appraise the reproducibility and limits of model interpretation. Fifteen analogue modeling laboratories participated in this benchmark initiative. Each laboratory received a shipment of the same type of quartz and corundum sand and all laboratories adhered to a stringent model building protocol and used the same type of foil to cover base and sidewalls of the sandbox. Sieve structure, sifting height, filling rate, and details on off-scraping of excess sand followed prescribed procedures. Our analogue benchmark shows that even for simple plane-strain experiments with prescribed stringent model construction techniques, quantitative model results show variability, most notably for surface slope, thrust spacing and number of forward and backthrusts. One of the sources of the variability in model results is related to slight variations in how sand is deposited in the sandbox. Small changes in sifting height, sifting rate, and scraping will result in slightly heterogeneous material bulk densities, which will affect the mechanical properties of the sand, and will result in lateral and vertical differences in peak and boundary friction angles, as well as cohesion values once the model is constructed. Initial variations in basal friction are inferred to play the most important role in causing model variability. Our comparison shows that the human factor plays a decisive role, and even when one modeler repeats the same experiment, quantitative model results still show variability. Our observations highlight the limits of up-scaling quantitative analogue model results to nature or for making comparisons with numerical models. The frictional behavior of sand is highly sensitive to small variations in material state or experimental set-up, and hence, it will remain difficult to scale quantitative results such as number of thrusts, thrust spacing

  3. Electromagnetic wave analogue of electronic diode

    OpenAIRE

    Shadrivov, Ilya V.; Powell, David A.; Kivshar, Yuri S.; Fedotov, Vassili A.; Zheludev, Nikolay I.

    2010-01-01

    An electronic diode is a nonlinear semiconductor circuit component that allows conduction of electrical current in one direction only. A component with similar functionality for electromagnetic waves, an electromagnetic isolator, is based on the Faraday effect of the polarization state rotation and is also a key component of optical and microwave systems. Here we demonstrate a chiral electromagnetic diode, which is a direct analogue of an electronic diode: its functionality is underpinned by ...

  4. Synthesis of constrained analogues of tryptophan

    Directory of Open Access Journals (Sweden)

    Elisabetta Rossi

    2015-10-01

    Full Text Available A Lewis acid-catalysed diastereoselective [4 + 2] cycloaddition of vinylindoles and methyl 2-acetamidoacrylate, leading to methyl 3-acetamido-1,2,3,4-tetrahydrocarbazole-3-carboxylate derivatives, is described. Treatment of the obtained cycloadducts under hydrolytic conditions results in the preparation of a small library of compounds bearing the free amino acid function at C-3 and pertaining to the class of constrained tryptophan analogues.

  5. The Brookhaven electron analogue, 1953--1957

    Energy Technology Data Exchange (ETDEWEB)

    Plotkin, M.

    1991-12-18

    The following topics are discussed on the Brookhaven electron analogue: L.J. Haworth and E.L. VanHorn letters; Original G.K. Green outline for report; General description; Parameter list; Mechanical Assembly; Alignment; Degaussing; Vacuum System; Injection System; The pulsed inflector; RF System; Ferrite Cavity; Pick-up electrodes and preamplifiers; Radio Frequency power amplifier; Lens supply; Controls and Power; and RF acceleration summary.

  6. Synthesis of a Cyclic Analogue of Galardin

    Institute of Scientific and Technical Information of China (English)

    马大为; 吴问根; 钱静; 郎深慧; 叶其壮

    2001-01-01

    A cyclic analogue 4 of galardin,a known MMP inhibitor,is designed to improve its selectivity.The synthesis of 4starts from dimethyl(S)-malate using diaselective alkylation and subsequent cyclization and amide formation as key steps.The compound 4 showed MMP inhibitory activity on all MMPs tested with IC50 ranging from 20.1 μM to 104 μM.

  7. Thymidine analogues for tracking DNA synthesis.

    Science.gov (United States)

    Cavanagh, Brenton L; Walker, Tom; Norazit, Anwar; Meedeniya, Adrian C B

    2011-09-15

    Replicating cells undergo DNA synthesis in the highly regulated, S-phase of the cell cycle. Analogues of the pyrimidine deoxynucleoside thymidine may be inserted into replicating DNA, effectively tagging dividing cells allowing their characterisation. Tritiated thymidine, targeted using autoradiography was technically demanding and superseded by 5-bromo-2-deoxyuridine (BrdU) and related halogenated analogues, detected using antibodies. Their detection required the denaturation of DNA, often constraining the outcome of investigations. Despite these limitations BrdU alone has been used to target newly synthesised DNA in over 20,000 reviewed biomedical studies. A recent breakthrough in "tagging DNA synthesis" is the thymidine analogue 5-ethynyl-2'-deoxyuridine (EdU). The alkyne group in EdU is readily detected using a fluorescent azide probe and copper catalysis using 'Huisgen's reaction' (1,3-dipolar cycloaddition or 'click chemistry'). This rapid, two-step biolabelling approach allows the tagging and imaging of DNA within cells whilst preserving the structural and molecular integrity of the cells. The bio-orthogonal detection of EdU allows its application in more experimental assays than previously possible with other "unnatural bases". These include physiological, anatomical and molecular biological experimentation in multiple fields including, stem cell research, cancer biology, and parasitology. The full potential of EdU and related molecules in biomedical research remains to be explored.

  8. Thymidine Analogues for Tracking DNA Synthesis

    Directory of Open Access Journals (Sweden)

    Brenton L. Cavanagh

    2011-09-01

    Full Text Available Replicating cells undergo DNA synthesis in the highly regulated, S-phase of the cell cycle. Analogues of the pyrimidine deoxynucleoside thymidine may be inserted into replicating DNA, effectively tagging dividing cells allowing their characterisation. Tritiated thymidine, targeted using autoradiography was technically demanding and superseded by 5-bromo-2-deoxyuridine (BrdU and related halogenated analogues, detected using antibodies. Their detection required the denaturation of DNA, often constraining the outcome of investigations. Despite these limitations BrdU alone has been used to target newly synthesised DNA in over 20,000 reviewed biomedical studies. A recent breakthrough in “tagging DNA synthesis” is the thymidine analogue 5-ethynyl-2′-deoxyuridine (EdU. The alkyne group in EdU is readily detected using a fluorescent azide probe and copper catalysis using ‘Huisgen’s reaction’ (1,3-dipolar cycloaddition or ‘click chemistry’. This rapid, two-step biolabelling approach allows the tagging and imaging of DNA within cells whilst preserving the structural and molecular integrity of the cells. The bio-orthogonal detection of EdU allows its application in more experimental assays than previously possible with other “unnatural bases”. These include physiological, anatomical and molecular biological experimentation in multiple fields including, stem cell research, cancer biology, and parasitology. The full potential of EdU and related molecules in biomedical research remains to be explored.

  9. Rational Design of Dipolar Chromophore as an Efficient Dopant-Free Hole-Transporting Material for Perovskite Solar Cells.

    Science.gov (United States)

    Li, Zhong'an; Zhu, Zonglong; Chueh, Chu-Chen; Jo, Sae Byeok; Luo, Jingdong; Jang, Sei-Hum; Jen, Alex K-Y

    2016-09-14

    In this paper, an electron donor-acceptor (D-A) substituted dipolar chromophore (BTPA-TCNE) is developed to serve as an efficient dopant-free hole-transporting material (HTM) for perovskite solar cells (PVSCs). BTPA-TCNE is synthesized via a simple reaction between a triphenylamine-based Michler's base and tetracyanoethylene. This chromophore possesses a zwitterionic resonance structure in the ground state, as evidenced by X-ray crystallography and transient absorption spectroscopies. Moreover, BTPA-TCNE shows an antiparallel molecular packing (i.e., centrosymmetric dimers) in its crystalline state, which cancels out its overall molecular dipole moment to facilitate charge transport. As a result, BTPA-TCNE can be employed as an effective dopant-free HTM to realize an efficient (PCE ≈ 17.0%) PVSC in the conventional n-i-p configuration, outperforming the control device with doped spiro-OMeTAD HTM.

  10. A theoretical study on the structural dependences of third-order optical nonlinearities of heterocycle-substituted polymethine cyanine chromophores

    Science.gov (United States)

    Wang, Chao; Yuan, Yizhong; Tian, Xiaohui; Sun, Jinyu; Shao, Hongjuan; Sun, Zhenrong

    2013-09-01

    The linear and third-order nonlinear optical properties of four polymethine cyanines (PC-1-PC-4) were investigated by UV-visible absorption spectroscopy and degenerate four-wave mixing (DFWM) technique. The second-order hyperpolarizabilities γ of the four chromophores achieve 10-31 esu. The dependence of their third-order optical nonlinearities on the molecular structure was discussed based on density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations. The calculated second-order hyperpolarizabilities γ well-reproduce the experimental trends. The results show that the third-order optical nonlinearities of the chromophores can be drastically enhanced by bulky heteroatom (such as selenium) with low electro-negativity, or extended π-conjugated terminal group.

  11. Probing ultrafast \\pi\\pi*/n\\pi* internal conversion in organic chromophores via K-edge resonant absorption

    CERN Document Server

    Wolf, T J A; Cryan, J P; Coriani, S; Squibb, R J; Battistoni, A; Berrah, N; Bostedt, C; Bucksbaum, P; Coslovich, G; Feifel, R; Gaffney, K J; Grilj, J; Martinez, T J; Miyabe, S; Moeller, S P; Mucke, M; Natan, A; Obaid, R; Osipov, T; Plekan, O; Wang, S; Koch, H; Gühr, M

    2016-01-01

    Organic chromophores with heteroatoms possess an important excited state relaxation channel from an optically allowed {\\pi}{\\pi}* to a dark n{\\pi}*state. We exploit the element and site specificity of soft x-ray absorption spectroscopy to selectively follow the electronic change during the {\\pi}{\\pi}*/n{\\pi}* internal conversion. As a hole forms in the n orbital during {\\pi}{\\pi}*/n{\\pi}* internal conversion, the near edge x-ray absorption fine structure (NEXAFS) spectrum at the heteroatom K-edge exhibits an additional resonance. We demonstrate the concept with the nucleobase thymine, a prototypical heteroatomic chromophore. With the help of time resolved NEXAFS spectroscopy at the oxygen K-edge, we unambiguously show that {\\pi}{\\pi}*/n{\\pi}* internal conversion takes place within (60 \\pm 30) fs. High-level coupled cluster calculations on the isolated molecules used in the experiment confirm the superb electronic structure sensitivity of this new method for excited state investigations.

  12. Design, synthesis, and characterization of a novel class of tunable chromophores for second- and third-order NLO applications

    Science.gov (United States)

    Attias, Andre-Jean; Leclerc, Nicolas; Chen, Qiying; Sargent, Edward H.; Schull, Guillaume; Charra, Fabrice

    2004-10-01

    We describe a general approach for the synthesis of 6,6'-(disubstituted)-3,3'-bipyridine based chromophores. This combinatorial type strategy is based on (i) the synthesis of a library of conjugated building blocks end-capped with electron donor or acceptor groups, and (ii) their homo- or cross-coupling. The compounds are either dipolar (push-pull molecules) or apolar (symmetric D-A-A-D) molecules. Depending on the building blocks, we are able to tune both the structural and NLO properties of the chromophores. For example, the D-A-A-D structure possesses ultrafast nonresonant nonlinearity around 1550 nm with excellent figures of merit, as well as TPA in the visible and NIR ranges.

  13. Computational Study of Linear and Nonlinear Optical Properties of Single Molecules and Clusters of Organic Electro-Optic Chromophores

    Science.gov (United States)

    Garrett, Kerry

    Organic electro-optic (OEO) materials integrated into silicon-organic hybrid (SOH) devices afford significant improvements in size, weight, power, and bandwidth (SWAP) performance of integrated electronic/photonic systems critical for current and next generation telecommunication, computer, sensor, transportation, and defense technologies. Improvement in molecular first hyperpolarizability, and in turn electro-optic activity, is crucial to further improvement in the performance of SOH devices. The timely preparation of new chromophores with improved molecular first hyperpolarizability requires theoretical guidance; however, common density functional theory (DFT) methods often perform poorly for optical properties in systems with substantial intramolecular charge transfer character. The first part of this dissertation describes the careful evaluation of popular long-range correction (LC) and range-separated hybrid (RSH) density functional theory (DFT) for definition of structure/function relationships crucial for the optimization of molecular first hyperpolarizability, beta. In particular, a benchmark set of well-characterized OEO chromophores is used to compare calculated results with the corresponding experimentally measured linear and nonlinear optical properties; respectively, the wavelength of the peak one-photon absorption energy, lambdamax, and beta. A goal of this work is to systematically determine the amount of exact exchange in LC/RSH-DFT methods required for accurately computing these properties for a variety OEO chromophores. High-level electron correlation (post-Hartree-Fock) methods are also investigated and compared with DFT. Included are results for the computation of beta using second-order Moller-Plesset perturbation theory (MP2) and the double-hybrid method, B2PLYP. The second part of this work transitions from single-molecule studies to computing bulk electronic and nonlinear optical properties of molecular crystals and isotropic ensembles of a

  14. Design, Synthesis and Evaluation of Organic Non-linear Optical Chromophores with Configurationally and Conformationally Locked Polyene Bridges

    Science.gov (United States)

    2007-11-02

    A modular, synthetic scheme was developed for versatile variation of donors, acceptors and polyene bridge length of NLO-chromophores. Configurational...and conformational rigidity of the polyene bridges were realized by making each set of adjacent double and single bond pair part of a fused...cylohexene ring. Substituent effects on the reactions leading to the establishment of the donor, elongation of the fused polyene bridge and the final

  15. Preorganized Chromophores Facilitate Triplet Energy Migration, Annihilation and Upconverted Singlet Energy Collection.

    Science.gov (United States)

    Mahato, Prasenjit; Yanai, Nobuhiro; Sindoro, Melinda; Granick, Steve; Kimizuka, Nobuo

    2016-05-25

    Photon upconversion (UC) based on triplet-triplet annihilation (TTA) has the potential to enhance significantly photovoltaic and photocatalytic efficiencies by harnessing sub-bandgap photons, but the progress of this field is held back by the chemistry problem of how to preorganize multiple chromophores for efficient UC under weak solar irradiance. Recently, the first maximization of UC quantum yield at solar irradiance was achieved using fast triplet energy migration (TEM) in metal-organic frameworks (MOFs) with ordered acceptor arrays, but at the same time, a trade-off between fast TEM and high fluorescence efficiency was also found. Here, we provide a solution for this trade-off issue by developing a new strategy, triplet energy migration, annihilation and upconverted singlet energy collection (TEM-UPCON). The porous structure of acceptor-based MOF crystals allows triplet donor molecules to be accommodated without aggregation. The surface of donor-doped MOF nanocrystals is modified with highly fluorescent energy collectors through coordination bond formation. Thanks to the higher fluorescence quantum yield of surface-bound collectors than parent MOFs, the implementation of the energy collector greatly improves the total UC quantum yield. The UC quantum yield maximization behavior at ultralow excitation intensity was retained because the TTA events take place only in the MOF acceptors. The TEM-UPCON concept may be generalized to collectors with various functions and would lead to quantitative harvesting of upconverted energy, which is difficult to achieve in common molecular diffusion-based systems.

  16. Features of the alkynyl ruthenium chromophore with modified anionic subsystem UV absorption.

    Science.gov (United States)

    Migalska-Zalas, A; Kityk, I V; Bakasse, M; Sahraoui, B

    2008-01-01

    Theoretical simulation of UV-vis absorption for a new series of alkynyl ruthenium chromophores spectra and investigations the influence of anionic substituence on a spectral shift of UV absorption was presented. The MM(+) molecular force field method was used for total energy minimization and for building of the molecular optimized geometry [S.J. Weiner, P.A. Kollman, D.A. Case, U.C. Ghio, G. Alagona, J.S. Profeta, P. Weiner, J. Am. Chem. Soc. 106 (1984) 765; S.J. Weiner, P.A. Kollman, D.T. Nguyen, D.A. Case, J. Comput. Chem. 7 (1986) 230]. All quantum chemical calculations were performed by semi-empirical ZINDO/1 method within a framework of the restricted Hartree-Fock approach and convergence limit up to 10(-6)eV after 500 iterations was achieved. Good agreement between the theoretically calculated and experimentally measured spectra was observed. The largest spectral shift in position of absorption peaks was observed for compound containing the anionic (Cl), substituent. The theoretically calculated absorption maximum is blue shifted with respect to the experimental spectra for all compounds what is connected with the changes of the charge transfer determining the corresponding state dipole moments. Analysis of the theoretical spectra shows a substantial sensitivity to the backside groups.

  17. Thermodynamic origin of selective binding of β-cyclodextrin derivatives with chiral chromophoric substituents toward steroids.

    Science.gov (United States)

    Chen, Yong; Li, Fang; Liu, Bo-Wen; Jiang, Bang-Ping; Zhang, Heng-Yi; Wang, Li-Hua; Liu, Yu

    2010-12-16

    Two β-cyclodextrin derivatives with chiral chromophoric substituents, that is, L- (1) and D-tyrosine-modified β-cyclodextrin (2), were synthesized and fully characterized. Their inclusion modes, binding abilities, and molecular selectivities with four steroid guests, that is, cholic acid sodium salt (CA), deoxycholic acid sodium salt (DCA), glycochoic acid sodium salt (GCA), and taurocholic acid sodium salt (TCA), were investigated by the circular dichroism, 2D NMR, and isothermal titration microcalorimetry (ITC). The results obtained from the circular dichroism and 2D NMR showed that two hosts adopted the different binding geometry, and these differences subsequently resulted in the significant differences of molecular binding abilities and selectivities. As compared with native β-cyclodextrin and tryptophan-modified β-cyclodextrin, host 2 showed the enhanced binding abilities for CA and DCA but the decreased binding abilities for GCA and TCA; however, host 1 showed the decreased binding abilities for all four bile salts. The best guest selectivity and the best host selectivity were K(S)(2-DCA)/K(S)(2-TCA) = 12.6 and K(S)(2-CA)/K(S)(1-CA) = 10, respectively, both exhibiting great enhancement as compared with the corresponding values of the previously reported L- and D-tryptophan-modified β-cyclodextrins. Thermodynamically, it was the favorable enthalpic gain that led to the high guest selectivity and host selectivity.

  18. Optogenetic inhibition of synaptic release with chromophore-assisted light inactivation (CALI).

    Science.gov (United States)

    Lin, John Y; Sann, Sharon B; Zhou, Keming; Nabavi, Sadegh; Proulx, Christophe D; Malinow, Roberto; Jin, Yishi; Tsien, Roger Y

    2013-07-24

    Optogenetic techniques provide effective ways of manipulating the functions of selected neurons with light. In the current study, we engineered an optogenetic technique that directly inhibits neurotransmitter release. We used a genetically encoded singlet oxygen generator, miniSOG, to conduct chromophore assisted light inactivation (CALI) of synaptic proteins. Fusions of miniSOG to VAMP2 and synaptophysin enabled disruption of presynaptic vesicular release upon illumination with blue light. In cultured neurons and hippocampal organotypic slices, synaptic release was reduced up to 100%. Such inhibition lasted >1 hr and had minimal effects on membrane electrical properties. When miniSOG-VAMP2 was expressed panneuronally in Caenorhabditis elegans, movement of the worms was reduced after illumination, and paralysis was often observed. The movement of the worms recovered overnight. We name this technique Inhibition of Synapses with CALI (InSynC). InSynC is a powerful way to silence genetically specified synapses with light in a spatially and temporally precise manner.

  19. Effect of chromophore elongation on linear and nonlinear optical properties of merocyanines derivatives of diethylaminocoumarin

    Science.gov (United States)

    Gayvoronsky, V. Ya.; Uklein, A. V.; Gerasov, A. O.; Garashchenko, V. V.; Kovtun, Yu. P.; Shandura, M. P.; Kachkovsky, O. D.

    2013-08-01

    A series of the merocyanines containing the aminocoumarin as an acceptor terminal group and typical donor residues with different length of the polymethine chain were studied in detail. Joint spectral and quantum-chemical analysis of their molecular geometries and electronic structures as well as origin of their lowest electron transitions have been performed. It was shown that the electronic and spectral properties of the neutral merocyanines are similar to the well-known cationic cyanine dyes, being determined by the same structure of the lowest electron transitions in molecule. The elongation of the chromophore chain of the studied merocyanines leads to the significant bathochromic shift of the long wavelength band in their absorption spectra, approximately to that in the symmetrical cyanines. The calculated third hyperpolarizability increases for the higher merocyanine vinylog due to the dependence of the energy of the excited state on the elongation of the conjugated chain. It was confirmed by nonlinear optical (NLO) study performed within the picosecond range pulsed laser excitation at 532 nm.

  20. SuperNova, a monomeric photosensitizing fluorescent protein for chromophore-assisted light inactivation.

    Science.gov (United States)

    Takemoto, Kiwamu; Matsuda, Tomoki; Sakai, Naoki; Fu, Donald; Noda, Masanori; Uchiyama, Susumu; Kotera, Ippei; Arai, Yoshiyuki; Horiuchi, Masataka; Fukui, Kiichi; Ayabe, Tokiyoshi; Inagaki, Fuyuhiko; Suzuki, Hiroshi; Nagai, Takeharu

    2013-01-01

    Chromophore-assisted light inactivation (CALI) is a powerful technique for acute perturbation of biomolecules in a spatio-temporally defined manner in living specimen with reactive oxygen species (ROS). Whereas a chemical photosensitizer including fluorescein must be added to specimens exogenously and cannot be restricted to particular cells or sub-cellular compartments, a genetically-encoded photosensitizer, KillerRed, can be controlled in its expression by tissue specific promoters or subcellular localization tags. Despite of this superiority, KillerRed hasn't yet become a versatile tool because its dimerization tendency prevents fusion with proteins of interest. Here, we report the development of monomeric variant of KillerRed (SuperNova) by direct evolution using random mutagenesis. In contrast to KillerRed, SuperNova in fusion with target proteins shows proper localization. Furthermore, unlike KillerRed, SuperNova expression alone doesn't perturb mitotic cell division. Supernova retains the ability to generate ROS, and hence promote CALI-based functional analysis of target proteins overcoming the major drawbacks of KillerRed.

  1. Third-Order Nonlinear Optical Behavior of Novel Polythiophene Derivatives Functionalized with Disperse Red 19 Chromophore

    Directory of Open Access Journals (Sweden)

    Marilú Chávez-Castillo

    2015-01-01

    Full Text Available Two copolymers of 3-alkylthiophene (alkyl = hexyl, octyl and a thiophene functionalized with disperse red 19 (TDR19 as chromophore side chain were synthesized by oxidative polymerization. The synthetic procedure was easy to perform, cost-effective, and highly versatile. The molecular structure, molecular weight distribution, film morphology, and optical and thermal properties of these polythiophene derivatives were determined by NMR, FT-IR, UV-Vis GPC, DSC-TGA, and AFM. The third-order nonlinear optical response of these materials was performed with nanosecond and femtosecond laser pulses by using the third-harmonic generation (THG and Z-scan techniques at infrared wavelengths of 1300 and 800 nm, respectively. From these experiments it was observed that although the TRD19 incorporation into the side chain of the copolymers was lower than 5%, it was sufficient to increase their nonlinear response in solid state. For instance, the third-order nonlinear electric susceptibility (χ3 of solid thin films made of these copolymers exhibited an increment of nearly 60% when TDR19 incorporation increased from 3% to 5%. In solution, the copolymers exhibited similar two-photon absorption cross sections σ2PA with a maximum value of 8545 GM and 233 GM (1 GM = 10−50 cm4 s per repeated monomeric unit.

  2. New Homogeneous Chromophore/Catalyst Concepts for the Solar-Driven Reduction of Carbon Dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Hopkins, Michael D. [The University of Chicago, Chicago, IL (United States)

    2015-06-22

    One of the major scientific and technical challenges of this century is to develop chemical means to store solar energy in the form of fuels. This can be accomplished by developing light-absorbing and catalytic compounds that function cooperatively to rearrange the chemical bonds of feedstocks in a way that allows solar energy to be stored and released on demand. The research conducted during this project was directed toward addressing fundamental questions that underlie the conversion of CO2 to a solar fuel using homogeneous molecular systems. The research focused particularly on developing methods for extracting the reducing equivalents for these photochemical conversions from H2, which is a renewable molecule sourced to water. The research followed two main lines. One effort focused on understanding the general principles that govern how light-absorbing molecules interact with independent H2 oxidation and CO2 reduction catalysts to produce a functional cycle for driving the energy-storing reverse water-gas-shift reaction with light. The second effort centered on developing the excited-state properties and H2 activation chemistry of tungsten–alkylidyne complexes. These chromophores were found to be powerful excited-state reducing agents, which could be incorporated into light-light-harvesting assemblies, and to hold the potential to be regenerated using H2.

  3. Photoproduction of hydrogen peroxide in aqueous solution from model compounds for chromophoric dissolved organic matter (CDOM).

    Science.gov (United States)

    Clark, Catherine D; de Bruyn, Warren; Jones, Joshua G

    2014-02-15

    To explore whether quinone moieties are important in chromophoric dissolved organic matter (CDOM) photochemistry in natural waters, hydrogen peroxide (H2O2) production and associated optical property changes were measured in aqueous solutions irradiated with a Xenon lamp for CDOM model compounds (dihydroquinone, benzoquinone, anthraquinone, napthoquinone, ubiquinone, humic acid HA, fulvic acid FA). All compounds produced H2O2 with concentrations ranging from 15 to 500 μM. Production rates were higher for HA vs. FA (1.32 vs. 0.176 mM h(-1)); values ranged from 6.99 to 0.137 mM h(-1) for quinones. Apparent quantum yields (Θ app; measure of photochemical production efficiency) were higher for HA vs. FA (0.113 vs. 0.016) and ranged from 0.0018 to 0.083 for quinones. Dihydroquinone, the reduced form of benzoquinone, had a higher production rate and efficiency than its oxidized form. Post-irradiation, quinone compounds had absorption spectra similar to HA and FA and 3D-excitation-emission matrix fluorescence spectra (EEMs) with fluorescent peaks in regions associated with CDOM.

  4. Chromophore-Assisted Light Inactivation of Mitochondrial Electron Transport Chain Complex II in Caenorhabditis elegans

    Science.gov (United States)

    Wojtovich, Andrew P.; Wei, Alicia Y.; Sherman, Teresa A.; Foster, Thomas H.; Nehrke, Keith

    2016-01-01

    Mitochondria play critical roles in meeting cellular energy demand, in cell death, and in reactive oxygen species (ROS) and stress signaling. Most Caenorhabditis elegans loss-of-function (lf) mutants in nuclear-encoded components of the respiratory chain are non-viable, emphasizing the importance of respiratory function. Chromophore-Assisted Light Inactivation (CALI) using genetically-encoded photosensitizers provides an opportunity to determine how individual respiratory chain components contribute to physiology following acute lf. As proof-of-concept, we expressed the ‘singlet oxygen generator’ miniSOG as a fusion with the SDHC subunit of respiratory complex II, encoded by mev-1 in C. elegans, using Mos1-mediated Single Copy Insertion. The resulting mev-1::miniSOG transgene complemented mev-1 mutant phenotypes in kn1 missense and tm1081(lf) deletion mutants. Complex II activity was inactivated by blue light in mitochondria from strains expressing active miniSOG fusions, but not those from inactive fusions. Moreover, light-inducible phenotypes in vivo demonstrated that complex II activity is important under conditions of high energy demand, and that specific cell types are uniquely susceptible to loss of complex II. In conclusion, miniSOG-mediated CALI is a novel genetic platform for acute inactivation of respiratory chain components. Spatio-temporally controlled ROS generation will expand our understanding of how the respiratory chain and mitochondrial ROS influence whole organism physiology. PMID:27440050

  5. Molecular hyperpolarizabilities of push–pull chromophores: A comparison between theoretical and experimental results

    Energy Technology Data Exchange (ETDEWEB)

    Capobianco, A. [Dipartimento di Fisica E.R. Caianiello, Università di Salerno, via ponte don Melillo, I-84084 Fisciano (Italy); Centore, R. [Dipartimento di Chimica P. Corradini, Università di Napoli, via Cintia, I-80126 Napoli (Italy); Noce, C. [Dipartimento di Fisica E.R. Caianiello, Università di Salerno, via ponte don Melillo, I-84084 Fisciano (Italy); Peluso, A., E-mail: apeluso@unisa.it [Dipartimento di Chimica e Biologia, Università di Salerno, via ponte don Melillo, I-84084 Fisciano (Italy)

    2013-01-16

    Highlights: ► Electro-optical determined and MP2/DFT computed NLO properties have been compared. ► Significant dependence of dipole moments of elongated NLO chromophores on conformations has been found. ► A thorough comparison between MP2 and DFT/TD-DFT computational approaches has been carried out. ► The two-state model overestimates hyperpolarizability. - Abstract: Electric dipole moments and static first order hyperpolarizabilities of two push–pull molecules with an extended π electron systems have been evaluated at different computational levels and compared with the results of electro-optical absorption measurements, based on the two state model. Calculations show that: (i) the dipole moments of such elongated systems depend significantly on conformation, a thorough conformational search is necessary for a meaningful comparison between theoretical and experimental results; (ii) DFT methods, in particular CAM-B3LYP and M05-2X, yield dipole moments which compare well with those obtained by post Hartree–Fock methods (MP2) and by EOA measurements; (iii) theoretical first order hyperpolarizabilities are largely underestimated, both by MP2 and DFT methods, possibly because of the failure of two state model used in electro-optical measurements.

  6. Photophysics of the Red Chromophore of HcRed: Evidence for Cis-Trans Isomerization and Protonation-State Changes

    Energy Technology Data Exchange (ETDEWEB)

    Cotlet, M.; Mudalige, K.; Habuchi, S.; Goodwin, P.M.; Pai, R.K.; De Schryver, F.

    2010-03-15

    HcRed is a dimeric intrinsically fluorescent protein with origins in the sea anemone Heteractis crispa. This protein exhibits deep red absorption and emission properties. Using a combination of ensemble and single molecule methods and by varying environmental parameters such as temperature and pH, we found spectroscopic evidence for the presence of two ground state conformers, trans and cis chromophores that are in thermal equilibrium and that follow different excited-state pathways upon exposure to light. The photocycle of HcRed appears to be a combination of both kindling proteins and bright emitting GFP/GFP-like proteins: the trans chromophore undergoes light driven isomerization followed by radiative relaxation with a fluorescence lifetime of 0.5 ns. The cis chromophore exhibits a photocycle similar to bright GFPs and GFP-like proteins such as enhanced GFP, enhanced YFP or DsRed, with radiative relaxation with a fluorescence lifetime of 1.5 ns, singlet-triplet deactivation on a microsecond time scale and solvent controlled protonation/deprotonation in tens of microseconds. Using single molecule spectroscopy, we identify trans and cis conformers at the level of individual moieties and show that it is possible that the two conformers can coexist in a single protein due to the dimeric nature of HcRed.

  7. Structure−Activity Analysis of Diffusible Lipid Electrophiles Associated with Phospholipid Peroxidation: 4-Hydroxynonenal and 4-Oxononenal Analogues

    OpenAIRE

    McGrath, Colleen E.; Tallman, Keri A.; Porter, Ned A.; Marnett, Lawrence J.

    2011-01-01

    Electrophile-mediated disruption of cell signal-ing is involved in the pathogenesis of several diseases including atherosclerosis and cancer. Diffusible and membrane bound lipid electrophiles are known to modify DNA and protein substrates and modulate cellular pathways including ER stress, antioxidant response, DNA damage, heat shock, and apoptosis. Herein we report on a structure−activity relationship for several electrophilic analogues of 4-hydroxynonenal (HNE) and 4-oxononenal (ONE) with r...

  8. Analogue to Digital and Digital to Analogue Converters (ADCs and DACs): A Review Update

    CERN Document Server

    Pickering, J

    2015-01-01

    This is a review paper updated from that presented for CAS 2004. Essentially, since then, commercial components have continued to extend their performance boundaries but the basic building blocks and the techniques for choosing the best device and implementing it in a design have not changed. Analogue to digital and digital to analogue converters are crucial components in the continued drive to replace analogue circuitry with more controllable and less costly digital processing. This paper discusses the technologies available to perform in the likely measurement and control applications that arise within accelerators. It covers much of the terminology and 'specmanship' together with an application-oriented analysis of the realisable performance of the various types. Finally, some hints and warnings on system integration problems are given.

  9. The Greenland analogue project. Yearly report 2010

    Energy Technology Data Exchange (ETDEWEB)

    Harper, J.; Brinkerhoff, D.; Johnson, J. [University of Montana, Missoula (United States); Ruskeeniemi, T.; Engstroem, J.; Kukkonen, I. [Geological Survey of Finland (Finland)] [and others

    2012-04-15

    A four-year field and modelling study of the Greenland ice sheet and subsurface conditions, Greenland Analogue Project (GAP), has been initiated collaboratively by SKB, Posiva and NWMO to advance the understanding of processes associated with glaciation and their impact on the long-term performance of a deep geological repository. The study site encompasses a land terminus portion of the Greenland ice sheet, east of Kangerlussuaq, and is in many ways considered to be an appropriate analogue of the conditions that are expected to prevail in much of Canada and Fennoscandia during future glacial cycles. The project begins in 2009 and is scheduled for completion in 2012. Our current understanding of the hydrological, hydrogeological and hydrogeochemical processes associated with cold climate conditions and glacial cycles, and their impact on the long-term performance of deep geological repositories for spent nuclear fuel, will be significantly improved by studying a modern analogue. The GAP will conduct the first in situ investigations of some of the parameters and processes needed to achieve a better understanding of how an ice sheet may impact a deep repository, and will provide measurements, observations and data that may significantly improve our safety assessments and risk analyses of glaciation scenarios. This report was produced by the GAP team members and presents an overview of the activities within the GAP during the interval January 1 to December 31, 2010, as well as research results obtained during this time frame. Research for the GAP is ongoing, and additional results related to the data presented here may become available in the future and will be presented in subsequent annual reports. (orig.)

  10. Technical Considerations in Magnetic Analogue Models

    CERN Document Server

    Adams, Patrick W M

    2016-01-01

    The analogy between vorticity and magnetic fields has been a subject of interest to researchers for a considerable period of time, mainly because of the structural similarities between the systems of equations that govern the evolution of the two fields. We recently presented the analysis of magnetic fields and hydrodynamics vorticity fields and argued for a formal theory of analogue magnetism. This article provides in depth technical details of the relevant considerations for the simulation procedures and extends the analyses to a range of fluids.

  11. Analogues of Euler and Poisson Summation Formulae

    Indian Academy of Sciences (India)

    Vivek V Rane

    2003-08-01

    Euler–Maclaurin and Poisson analogues of the summations $\\sum_{a < n ≤ b}(n)f(n), \\sum_{a < n ≤ b}d(n) f(n), \\sum_{a < n ≤ b}d(n)(n) f(n)$ have been obtained in a unified manner, where (()) is a periodic complex sequence; () is the divisor function and () is a sufficiently smooth function on [, ]. We also state a generalised Abel's summation formula, generalised Euler's summation formula and Euler's summation formula in several variables.

  12. Analogue cosmology in a hadronic fluid

    Directory of Open Access Journals (Sweden)

    Bilić Neven

    2014-01-01

    Full Text Available Analog gravity models of general relativity seem promising routes to providing laboratory tests of the foundation of quantum field theory in curved space-time. In contrast to general relativity, where geometry of a spacetime is determined by the Einstein equations, in analog models geometry and evolution of analog spacetime are determined by the equations of fluid mechanics. In this paper we study the analogue gravity model based on massless pions propagating in a expanding hadronic fluid. The analog expanding spacetime takes the form of an FRW universe, with the apparent and trapping horizons defined in the standard way.

  13. Satellite television analogue and digital reception techniques

    CERN Document Server

    Benoit, Herve

    1999-01-01

    Satellite television is part of the lives of millions of television viewers worldwide and its influence is set to increase significantly with the launch of digital satellite television services.This comprehensive reference book, written by the author of the highly successful 'Digital Television', provides a technical overview of both analogue and digital satellite TV. Written concisely and thoroughly, it covers all aspects of satellite TV necessary to understand its operation and installation. It also covers the evolution of satellite television, and contains a detailed glossary of tec

  14. U.S. Nuclear Regulatory Commission natural analogue research program

    Energy Technology Data Exchange (ETDEWEB)

    Kovach, L.A.; Ott, W.R. [Nuclear Regulatory Commission, Washington, DC (United States)

    1995-09-01

    This article describes the natural analogue research program of the U.S. Nuclear Regulatory Commission (US NRC). It contains information on the regulatory context and organizational structure of the high-level radioactive waste research program plan. It also includes information on the conditions and processes constraining selection of natural analogues, describes initiatives of the US NRC, and describes the role of analogues in the licensing process.

  15. Chromophoric Dissolved Organic Matter across a Marine Distributed Biological Observatory in the Pacific Arctic Region

    Science.gov (United States)

    Berman, S. L.; Frey, K. E.; Shake, K. L.; Cooper, L. W.; Grebmeier, J. M.

    2014-12-01

    Dissolved organic matter (DOM) plays an important role in marine ecosystems as both a carbon source for the microbial food web (and thus a source of CO2 to the atmosphere) and as a light inhibitor in marine environments. The presence of chromophoric dissolved organic matter (CDOM; the optically active portion of total DOM) can have significant controlling effects on transmittance of sunlight through the water column and therefore on primary production as well as the heat balance of the upper ocean. However, CDOM is also susceptible to photochemical degradation, which decreases the flux of solar radiation that is absorbed. Knowledge of the current spatial and temporal distribution of CDOM in marine environments is thus critical for understanding how ongoing and future changes in climate may impact these biological, biogeochemical, and physical processes. We describe the quantity and quality of CDOM along five key productive transects across a developing Distributed Biological Observatory (DBO) in the Pacific Arctic region. The samples were collected onboard the CCGS Sir Wilfred Laurier in July 2013 and 2014. Monitoring of the variability of CDOM along transects of high productivity can provide important insights into biological and biogeochemical cycling across the region. Our analyses include overall concentrations of CDOM, as well as proxy information such as molecular weight, lability, and source (i.e., autochthonous vs. allochthonous) of organic matter. We utilize these field observations to compare with satellite-derived CDOM concentrations determined from the Aqua MODIS satellite platform, which ultimately provides a spatially and temporally continuous synoptic view of CDOM concentrations throughout the region. Examining the current relationships among CDOM, sea ice variability, biological productivity, and biogeochemical cycling in the Pacific Arctic region will likely provide key insights for how ecosystems throughout the region will respond in future

  16. Flavylium chromophores as species markers for dragon's blood resins from Dracaena and Daemonorops trees.

    Science.gov (United States)

    Sousa, Micaela M; Melo, Maria J; Parola, A Jorge; Seixas de Melo, J Sérgio; Catarino, Fernando; Pina, Fernando; Cook, Frances E M; Simmonds, Monique S J; Lopes, João A

    2008-10-31

    A simple and rapid liquid chromatographic method with diode-array UV-vis spectrophotometric detection has been developed for the authentication of dragon's blood resins from Dracaena and Daemonorops trees. Using this method it was discovered that the flavylium chromophores, which contribute to the red colour of these resins, differ among the species and could be used as markers to differentiate among species. A study of parameters, such as time of extraction, proportion of MeOH and pH, was undertaken to optimise the extraction of the flavyliums. This method was then used to make extracts from samples of dragon's blood resin obtained from material of known provenance. From the samples analysed 7,6-dihydroxy-5-methoxyflavylium (dracorhodin), 7,4'-dihydroxy-5-methoxyflavylium (dracoflavylium) and 7,4'-dihydroxyflavylium were selected as species markers for Daemonorops spp., Dracaena draco and Dracaena cinnabari, respectively. The chromatograms from these samples were used to build an HPLC-DAD database. The ability to discriminate among species of dragon's blood using the single marker compounds was compared with a principal components analysis of the chromatograms in the HPLC-DAD database. The results from the HPLC-DAD method based on the presence of these flavylium markers was unequivocal. The HPLC-DAD method was subsequently applied to 37 samples of dragon blood resins from the historical samples in the Economic Botany Collection, Royal Botanic Gardens, Kew. The method identified anomalies in how samples in this collection had been labelled. It is clear that the method can be used to evaluate the provenance of samples used in different areas of cultural heritage. It also could be used to monitor the trade of endangered species of dragon's blood and the species being used in complex formulations of traditional Chinese medicine.

  17. Sources and transformations of dissolved lignin phenols and chromophoric dissolved organic matter in Otsuchi Bay, Japan

    Directory of Open Access Journals (Sweden)

    Chia-Jung eLu

    2016-06-01

    Full Text Available Dissolved lignin phenols and optical properties of dissolved organic matter (DOM were measured to investigate the sources and transformations of terrigenous DOM (tDOM in Otsuchi Bay, Japan. Three rivers discharge into the bay, and relatively high values of syringyl:vanillyl phenols (0.73 ± 0.07 and cinnamyl:vanillyl phenols (0.33 ± 0.10 indicated large contributions of non-woody angiosperm tissues to lignin and tDOM. The physical mixing of river and seawater played an important role in controlling the concentrations and distributions of lignin phenols and chromophoric DOM (CDOM optical properties in the bay. Lignin phenol concentrations and the CDOM absorption coefficient at 350 nm, a(350, were strongly correlated in river and bay waters. Measurements of lignin phenols and CDOM in bay waters indicated a variety of photochemical and biological transformations of tDOM, including oxidation reactions, photobleaching and a decrease in molecular weight. Photodegradation and biodegradation of lignin and CDOM were investigated in decomposition experiments with river water and native microbial assemblages exposed to natural sunlight or kept in the dark. There was a rapid and substantial removal of lignin phenols and CDOM during the first few days in the light treatment, indicating transformations of tDOM and CDOM can occur soon after discharge of buoyant river water into the bay. The removal of lignin phenols was slightly greater in the dark (34% than in the light (30% during the remaining 59 days of the incubation. Comparison of the light and dark treatments indicated biodegradation was responsible for 67% of total lignin phenol removal during the 62-day incubation exposed to natural sunlight, indicating biodegradation is a dominant removal process in Otsuchi Bay.

  18. Spin dynamics of photogenerated triradicals in fixed distance electron donor-chromophore-acceptor-TEMPO molecules.

    Science.gov (United States)

    Mi, Qixi; Chernick, Erin T; McCamant, David W; Weiss, Emily A; Ratner, Mark A; Wasielewski, Michael R

    2006-06-15

    The stable free radical 2,2,6,6-tetramethylpiperidinoxyl (TEMPO, T*) was covalently attached to the electron acceptor in a donor-chromophore-acceptor (D-C-A) system, MeOAn-6ANI-Phn-A-T*, having well-defined distances between each component, where MeOAn = p-methoxyaniline, 6ANI = 4-(N-piperidinyl)naphthalene-l,8-dicarboximide, Ph = 2,5-dimethylphenyl (n = 0,1), and A = naphthalene-1,8:4,5-bis(dicarboximide) (NI) or pyromellitimide (PI). Using both time-resolved optical and EPR spectroscopy, we show that T* influences the spin dynamics of the photogenerated triradical states 2,4(MeOAn+*-6ANI-Phn-A-*-T*), resulting in modulation of the charge recombination rate within the triradical compared with the corresponding biradical lacking T*. The observed spin-spin exchange interaction between the photogenerated radicals MeOAn+* and A-* is not altered by the presence of T*, which interacts most strongly with A-* and accelerates radical pair intersystem crossing. Charge recombination within the triradicals results in the formation of 2,4(MeOAn-6ANI-Phn-3*NI-T*) or 2,4(MeOAn-3*6ANI-Phn-PI-T*) in which T* is strongly spin polarized in emission. Normally, the spin dynamics of correlated radical pairs do not produce a net spin polarization; however, the rate at which the net spin polarization appears on T* closely follows the photogenerated radical ion pair decay rate. This effect is attributed to antiferromagnetic coupling between T* and the local triplet state 3NI, which is populated following charge recombination. These results are explained using a switch in the spin basis set between the triradical and the three-spin charge recombination product having both T* and 3*NI or 3*6ANI present.

  19. Looking at the Green Fluorescent Protein (GFP) chromophore from a different perspective: a computational insight.

    Science.gov (United States)

    Paul, Bijan Kumar; Guchhait, Nikhil

    2013-02-15

    In the present contribution Density Functional Theory (DFT) has been applied to explore molecular dipole moment, frontier molecular orbital (FMO) features, chemical hardness, and the molecular electrostatic potential surface (MEPS) characteristics for optimized molecular geometry of the Green Fluorescent Protein (GFP) chromophore p-hydroxybenzylideneimidazolinone (HBDI) both in its protonated (neutral) and deprotonated (anion) forms. The distribution of atomic charges over the entire molecular framework as obtained from Natural Bond Orbital (NBO) analysis is found to faithfully replicate the predictions from the MEP map in respect of reactivity map of HBDI (neutral and anion) and possible sites for hydrogen bonding interactions etc. The three dimensional MEP map encompassing the entire molecule yields a reliable reactivity map of HBDI molecule also displaying the most probable regions for non-covalent interactions. The differential distribution of the electrostatic potential over the neutral and anionic species of HBDI is authentically reflected on MEP map and NBO charge distribution analysis. Thermodynamic properties such as heat capacity, thermal energy, enthalpy, entropy have been calculated and the correlation of the various thermodynamic functions with temperature has been established for neutral molecule. More importantly, however, the computational approach has been employed to unveil the nonlinear optical (NLO) properties of protonated (neutral) and deprotonated (anion) HBDI. Also in an endeavor to achieve a fuller understanding on this aspect the effect of basis set on the NLO properties of the title molecule has been investigated. Our computations delineate the discernible differences in NLO properties between the neutral and anionic species of HBDI whereby indicating the possibility of development of photoswitchable NLO device.

  20. Characterization and spacial distribution variability of chromophoric dissolved organic matter (CDOM) in the Yangtze Estuary.

    Science.gov (United States)

    Wang, Ying; Zhang, Di; Shen, Zhenyao; Chen, Jing; Feng, Chenghong

    2014-01-01

    The spatial characteristics and the quantity and quality of the chromophoric dissolved organic matter (CDOM) in the Yangtze Estuary, based on the abundance, degree of humification and sources, were studied using 3D fluorescence excitation emission matrix spectra (F-EEMs) with parallel factor and principal component analysis (PARAFAC-PCA). The results indicated that the CDOM abundance decreased and the aromaticity increased from the upstream to the downstream areas of the estuary. Higher CDOM abundance and degrees of humification were observed in the pore water than that in the surface and bottom waters. Two humic-like components (C1 and C3) and one tryptophan-like component (C2) were identified using the PARAFAC model. The separation of the samples by PCA highlighted the differences in the DOM properties. Components C1 and C3 concurrently displayed positive factor 1 loadings with nearly zero factor 2 loadings, while C2 showed highly positive factor 2 loadings. The C1 and C3 were very similar and exhibited a direct relationship with A355 and DOC. The CDOM in the pore water increased along the river to the coastal area, which was mainly influenced by C1 and C3 and was significantly derived from sediment remineralization and deposition from the inflow of the Yangtze River. The CDOM in the surface and bottom waters was dominated by C2, especially in the inflows of multiple tributaries that were affected by intensive anthropogenic activities. The microbial degradation of exogenous wastes from the tributary inputs and shoreside discharges were dominant sources of the CDOM in the surface and bottom waters.

  1. Conformational heterogeneity of the Pfr chromophore in plant and cyanobacterial phytochromes.

    Science.gov (United States)

    Velazquez Escobar, Francisco; von Stetten, David; Günther-Lütkens, Mina; Keidel, Anke; Michael, Norbert; Lamparter, Tilman; Essen, Lars-Oliver; Hughes, Jon; Gärtner, Wolfgang; Yang, Yang; Heyne, Karsten; Mroginski, Maria A; Hildebrandt, Peter

    2015-01-01

    Phytochromes are biological photoreceptors that can be reversibly photoconverted between a dark and photoactivated state. The underlying reaction sequences are initiated by the photoisomerization of the tetrapyrrole cofactor, which in plant and cyanobacterial phytochromes are a phytochromobilin (PΦB) and a phycocyanobilin (PCB), respectively. The transition between the two states represents an on/off-switch of the output module activating or deactivating downstream physiological processes. In addition, the photoactivated state, i.e., Pfr in canonical phytochromes, can be thermally reverted to the dark state (Pr). The present study aimed to improve our understanding of the specific reactivity of various PΦB- and PCB-binding phytochromes in the Pfr state by analysing the cofactor structure by vibrational spectroscopic techniques. Resonance Raman (RR) spectroscopy revealed two Pfr conformers (Pfr-I and Pfr-II) forming a temperature-dependent conformational equilibrium. The two sub-states-found in all phytochromes studied, albeit with different relative contributions-differ in structural details of the C-D and A-B methine bridges. In the Pfr-I sub-state the torsion between the rings C and D is larger by ca. 10° compared to Pfr-II. This structural difference is presumably related to different hydrogen bonding interactions of ring D as revealed by time-resolved IR spectroscopic studies of the cyanobacterial phytochrome Cph1. The transitions between the two sub-states are evidently too fast (i.e., nanosecond time scale) to be resolved by NMR spectroscopy which could not detect a structural heterogeneity of the chromophore in Pfr. The implications of the present findings for the dark reversion of the Pfr state are discussed.

  2. Conformational heterogeneity of the Pfr chromophore in plant and cyanobacterial phytochromes

    Directory of Open Access Journals (Sweden)

    Francisco eVelazquez Escobar

    2015-07-01

    Full Text Available Phytochromes are biological photoreceptors that can be reversibly photoconverted between a dark and photoactivated state. The underlying reaction sequences are initiated by the photoisomerisation of the tetrapyrrole cofactor, which in plant and cyanobacterial phytochromes are a phytochromobilin (PB and a phycocyanobilin (PCB, respectively. The transition between the two states represents an on/off-switch of the output module activating or deactivating downstream physiological processes. In addition, the photoactivated state, i.e. Pfr in canonical phytochromes, can be thermally reverted to the dark state (Pr. The present study aimed to improve our understanding of the specific reactivity of various PB- and PCB-binding phytochromes in the Pfr state by analyzing the cofactor structure by vibrational spectroscopic techniques. Resonance Raman (RR spectroscopy revealed two Pfr conformers (Pfr-I and Pfr-II forming a temperature-dependent conformational equilibrium. The two sub-states - found in all phytochromes studied, albeit with different relative contributions - differ in structural details of the C-D and A-B methine bridges. In the Pfr-I sub-state the torsion between the rings C and D is larger by ca. 10o compared to Pfr-II. This structural difference is presumably related to different hydrogen bonding interactions of ring D as revealed by time-resolved IR spectroscopic studies of the cyanobacterial phytochrome Cph1. The transitions between the two sub-states are evidently too fast (i.e., nanosecond time scale to be resolved by NMR spectroscopy which could not detect a structural heterogeneity of the chromophore in Pfr. The implications of the present findings for the dark reversion of the Pfr state are discussed.

  3. Highly expressed N1-acetylpolyamine oxidase detoxifies polyamine analogue N1-cyclopropylmethyl-N11-ethylnorspermine in human lung cancer cell line A549

    Institute of Scientific and Technical Information of China (English)

    HAN Yu; REN Yu-san; CAO Chun-yu; REN Dong-ming; ZHOU Yong-qin; WANG Yan-lin

    2009-01-01

    Background The critical roles of polyamines in cell growth and differentiation have made polyamine metabolic pathway a promising target for antitumor therapy. Recent studies have demonstrated in vitro that some antitumor polyamine analogues could be used as substrates and oxidized by purified recombinant human N1-acetylpolyamine oxidase (APAO, an enzyme that catabolizes natural polyamines), indicating a potential role of APAO in determining the sensitivity of cancer cells to specific antitumor analogues. This study evaluated, in vivo, the effect of APAO on cytotoxicity of antitumor polyamine analogue, N1-cyclopropylmethyI-N11-ethylnorspermine (CPENS) and its mechanism when highly expressed in human lung cancer line A549.Methods A clone with high expression of APAO was obtained by transfecting A549 lung cancer cell line with pcDNA3.1/APAO plasmid and selecting with quantitative realtime PCR and APAO activity assay. Cell proliferation was determined by MTT method and apoptosis related events were evaluated by DNA fragmentation, sub-G1/flow cytometric assay, western blotting (for cytochrome C and Bax) and colorimetric assay (for casapse-3 activity). Results A clone highly expressing APAO was obtained. High expression of APAO in A549 cells inhibited accumulation of CPENS, decreased their sensitivity to the toxicity of CPENS and prevented CPENS induced apoptosis. Conclusion These results indicate a new drug resisting, mechanism in the tumor cells. High expression of APAO can greatly decrease the sensitivity of tumor cells to the specific polyamine analogues by detoxitying those analogues and prevent analogue induced apoptosis.

  4. Self-Powered Analogue Smart Skin.

    Science.gov (United States)

    Shi, Mayue; Zhang, Jinxin; Chen, Haotian; Han, Mengdi; Shankaregowda, Smitha A; Su, Zongming; Meng, Bo; Cheng, Xiaoliang; Zhang, Haixia

    2016-04-26

    The progress of smart skin technology presents unprecedented opportunities for artificial intelligence. Resolution enhancement and energy conservation are critical to improve the perception and standby time of robots. Here, we present a self-powered analogue smart skin for detecting contact location and velocity of the object, based on a single-electrode contact electrification effect and planar electrostatic induction. Using an analogue localizing method, the resolution of this two-dimensional smart skin can be achieved at 1.9 mm with only four terminals, which notably decreases the terminal number of smart skins. The sensitivity of this smart skin is remarkable, which can even perceive the perturbation of a honey bee. Meanwhile, benefiting from the triboelectric mechanism, extra power supply is unnecessary for this smart skin. Therefore, it solves the problems of batteries and connecting wires for smart skins. With microstructured poly(dimethylsiloxane) films and silver nanowire electrodes, it can be covered on the skin with transparency, flexibility, and high sensitivity.

  5. Dynamic Analogue Initialization for Ensemble Forecasting

    Institute of Scientific and Technical Information of China (English)

    LI Shan; RONG Xingyao; LIU Yun; LIU Zhengyu; Klaus FRAEDRICH

    2013-01-01

    This paper introduces a new approach for the initialization of ensemble numerical forecasting:Dynamic Analogue Initialization (DAI).DAI assumes that the best model state trajectories for the past provide the initial conditions for the best forecasts in the future.As such,DAI performs the ensemble forecast using the best analogues from a full size ensemble.As a pilot study,the Lorenz63 and Lorenz96 models were used to test DAI's effectiveness independently.Results showed that DAI can improve the forecast significantly.Especially in lower-dimensional systems,DAI can reduce the forecast RMSE by ~50% compared to the Monte Carlo forecast (MC).This improvement is because DAI is able to recognize the direction of the analysis error through the embedding process and therefore selects those good trajectories with reduced initial error.Meanwhile,a potential improvement of DAI is also proposed,and that is to find the optimal range of embedding time based on the error's growing speed.

  6. Long-term predictions using natural analogues

    Energy Technology Data Exchange (ETDEWEB)

    Ewing, R.C. [Univ. of New Mexico, Albuquerque, NM (United States)

    1995-09-01

    One of the unique and scientifically most challenging aspects of nuclear waste isolation is the extrapolation of short-term laboratory data (hours to years) to the long time periods (10{sup 3}-10{sup 5} years) required by regulatory agencies for performance assessment. The direct validation of these extrapolations is not possible, but methods must be developed to demonstrate compliance with government regulations and to satisfy the lay public that there is a demonstrable and reasonable basis for accepting the long-term extrapolations. Natural systems (e.g., {open_quotes}natural analogues{close_quotes}) provide perhaps the only means of partial {open_quotes}validation,{close_quotes} as well as data that may be used directly in the models that are used in the extrapolation. Natural systems provide data on very large spatial (nm to km) and temporal (10{sup 3}-10{sup 8} years) scales and in highly complex terranes in which unknown synergisms may affect radionuclide migration. This paper reviews the application (and most importantly, the limitations) of data from natural analogue systems to the {open_quotes}validation{close_quotes} of performance assessments.

  7. Dynamic fluorescence spectroscopy on single tryptophan mutants of EIImtl in detergent micelles : Effects of substrate binding and phosphorylation on the fluorescence and anisotropy decay

    NARCIS (Netherlands)

    Swaving Dijkstra, Dolf; Broos, J.; Visser, Antonie J.W.G.; van Hoek, A.; Robillard, George

    1997-01-01

    The effects of substrate and substrate analogue binding and phosphorylation on the conformational dynamics of the mannitol permease of Escherichia coli were investigated, using time-resolved fluorescence spectroscopy on mutants containing five single tryptophans situated in the membrane-embedded C d

  8. Studies on phospholipase a and its zymogen from porcine pancreas IV. The influence of chemical modification of the lecithin structure on substrate properties

    NARCIS (Netherlands)

    Bonsen, P.P.M.; Haas, Gerard H. de; Pieterson, W.A.; Deenen, L.L.M. van

    1972-01-01

    1. 1. A series of chemically modified lecithins were used to investigate by kinetic analyses their substrate c.q. inhibitor properties for porcine pancreatic phospholipase A. The substrate analogues used were systematically modified in: the stereochemical configuration, the susceptible ester bond, t

  9. Synthesis, Properties and Applications of Diazotrifluropropanoyl-Containing Photoactive Analogues of Farnesyl Diphosphate Containing Modified Linkages for Enhanced Stability

    Science.gov (United States)

    Hovlid, Marisa L.; Edelstein, Rebecca L.; Henry, Olivier; Ochocki, Joshua; DeGraw, Amanda; Lenevich, Stepan; Talbot, Trista; Young, Victor G.; Hruza, Alan W.; Lopez-Gallego, Fernando; Labello, Nicholas P.; Strickland, Corey L.; Schmidt-Dannert, Claudia; Distefano, Mark D.

    2009-01-01

    Photoactive analogues of farnesyl diphosphate (FPP) are useful probes in studies of enzymes that employ this molecule as a substrate. Here, we describe the preparation and properties of two new FPP analogues that contain diazotrifluoropropionyl photophores linked to geranyl diphosphate via amide or ester linkages. The amide-linked analogue (3) was synthesized in 32P-labeled form from geraniol in 7 steps. Experiments with Saccharomyces cerevisiae protein farnesyltransferase (ScPFTase) showed that 3 is an alternative substrate for the enzyme. Photolysis experiments with [32P]3 demonstrate that this compound labels the β-subunits of both farnesyl- and geranylgeranyltransferase (types 1 and 2). However, the amide-linked probe 3 undergoes a rearrangement to a photochemically unreactive isomeric triazolone upon long term storage making it inconvenient to use. To address this stability issue, the ester-linked analogue 4 was prepared in 6 steps from geraniol. Computational analysis and X-ray crystallographic studies suggest that 4 binds to PFTase in a similar fashion as FPP. Compound 4 is also an alternative substrate for PFTase and a 32P-labeled form selectively photocrosslinks the β-subunit of ScPFTase as well as E. coli farnesyldiphosphate synthase and a germacrene-producing sesquiterpene synthase from Nostoc sp. strain PCC7120 (a cyanobacterial source). Finally, nearly exclusive labeling of ScPFTase in crude E. coli extract was observed, suggesting that [32P]4 manifests significant selectivity and should hence be useful for identifying novel FPP utilizing enzymes in crude protein preparations. PMID:19954434

  10. Low-temperature spectra of the analogues of 10-hydroxybenzo[h]quinoline as an indication of barrierless ESIPT.

    Science.gov (United States)

    Deperasińska, Irena; Gryko, Daniel T; Karpiuk, Elena; Kozankiewicz, Bolesław; Makarewicz, Artur; Piechowska, Joanna

    2012-12-13

    The absorption and fluorescence spectra of two analogues of 10-hydroxybenzo[h]quinoline (10-HBQ), namely, 1-hydroxy-7-methylbenzo[c]acridine (HMBA) and 4-hydroxybenzo[c]phenanthridine (HBPA), were studied in n-alkane matrices at 5 K. Considerable energy separation between the onsets of the spectra and broadening of the bands was an indication that intramolecular proton transfer (ESIPT) takes place at such a low temperature. DFT and ab initio methods were used to calculate the electronic transition energies and oscillator strengths and the vibronic structure of the electronic spectra. Shortcomings in our knowledge of the shape of the potential energy surface for ESIPT systems are highlighted in the context of the discussion of the shape of the electronic spectra. The π-expansion of the 10-HBQ chromophore achieved by adding a benzene moiety at various positions adjacent to the pyridine ring led to compounds possessing diverse photophysical properties, ranging from the non-ESIPT strongly fluorescent molecule of 10-hydroxy-1-azaperylene to weakly emitting (or nonemitting) molecules, where ESIPT occurs very efficiently.

  11. Robust plasmonic substrates

    DEFF Research Database (Denmark)

    Kostiučenko, Oksana; Fiutowski, Jacek; Tamulevicius, Tomas

    2014-01-01

    substrates is presented, which relies on the coverage of gold nanostructures with diamond-like carbon (DLC) thin films of thicknesses 25, 55 and 105 nm. DLC thin films were grown by direct hydrocarbon ion beam deposition. In order to find the optimum balance between optical and mechanical properties...... and breaking. DLC coating with thicknesses between 25 and 105 nm is found to considerably increase the mechanical strength of the substrates while at the same time ensuring conservation of sufficient field enhancements of the gold plasmonic substrates....

  12. Unusual Spectral Properties of Bacteriophytochrome Agp2 Result from a Deprotonation of the Chromophore in the Red-absorbing Form Pr*

    Science.gov (United States)

    Zienicke, Benjamin; Molina, Isabel; Glenz, René; Singer, Patrick; Ehmer, Dorothee; Escobar, Francisco Velazquez; Hildebrandt, Peter; Diller, Rolf; Lamparter, Tilman

    2013-01-01

    Phytochromes are widely distributed photoreceptors with a bilin chromophore that undergo a typical reversible photoconversion between the two spectrally different forms, Pr and Pfr. The phytochrome Agp2 from Agrobacterium tumefaciens belongs to the group of bathy phytochromes that have a Pfr ground state as a result of the Pr to Pfr dark conversion. Agp2 has untypical spectral properties in the Pr form reminiscent of a deprotonated chromophore as confirmed by resonance Raman spectroscopy. UV/visible absorption spectroscopy showed that the pKa is >11 in the Pfr form and ∼7.6 in the Pr form. Unlike other phytochromes, photoconversion thus results in a pKa shift of more than 3 units. The Pr/Pfr ratio after saturating irradiation with monochromatic light is strongly pH-dependent. This is partially due to a back-reaction of the deprotonated Pr chromophore at pH 9 after photoexcitation as found by flash photolysis. The chromophore protonation and dark conversion were affected by domain swapping and site-directed mutagenesis. A replacement of the PAS or GAF domain by the respective domain of the prototypical phytochrome Agp1 resulted in a protonated Pr chromophore; the GAF domain replacement afforded an inversion of the dark conversion. A reversion was also obtained with the triple mutant N12S/Q190L/H248Q, whereas each single point mutant is characterized by decelerated Pr to Pfr dark conversion. PMID:24036118

  13. Unusual spectral properties of bacteriophytochrome Agp2 result from a deprotonation of the chromophore in the red-absorbing form Pr.

    Science.gov (United States)

    Zienicke, Benjamin; Molina, Isabel; Glenz, René; Singer, Patrick; Ehmer, Dorothee; Escobar, Francisco Velazquez; Hildebrandt, Peter; Diller, Rolf; Lamparter, Tilman

    2013-11-01

    Phytochromes are widely distributed photoreceptors with a bilin chromophore that undergo a typical reversible photoconversion between the two spectrally different forms, Pr and Pfr. The phytochrome Agp2 from Agrobacterium tumefaciens belongs to the group of bathy phytochromes that have a Pfr ground state as a result of the Pr to Pfr dark conversion. Agp2 has untypical spectral properties in the Pr form reminiscent of a deprotonated chromophore as confirmed by resonance Raman spectroscopy. UV/visible absorption spectroscopy showed that the pKa is >11 in the Pfr form and ∼7.6 in the Pr form. Unlike other phytochromes, photoconversion thus results in a pKa shift of more than 3 units. The Pr/Pfr ratio after saturating irradiation with monochromatic light is strongly pH-dependent. This is partially due to a back-reaction of the deprotonated Pr chromophore at pH 9 after photoexcitation as found by flash photolysis. The chromophore protonation and dark conversion were affected by domain swapping and site-directed mutagenesis. A replacement of the PAS or GAF domain by the respective domain of the prototypical phytochrome Agp1 resulted in a protonated Pr chromophore; the GAF domain replacement afforded an inversion of the dark conversion. A reversion was also obtained with the triple mutant N12S/Q190L/H248Q, whereas each single point mutant is characterized by decelerated Pr to Pfr dark conversion.

  14. ZINDO-SOS Studies on Second-order Nonlinear Optical Properties of Thiophene S,S-Dioxide Chromophores

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The second-order nonlinear optical properties of thiophene S,S-dioxides derivatives were studied by using the ZINDO-SOS method. The computed results show that the thiophene S,S-dioxide derivatives exhibit larger second-order polarizabilities than their thiophene precursors. In order to clarify the origin of the different NLO responses among these chromophores, their electron properties and frontier orbital properties were investigated as well. These thiophene S,S-dioxides derivatives are good candidates for their application in electro-optical device due to their high nonlinearities, good thermal and photo stabilities.

  15. Linear and third-order nonlinear optical properties for the heptamethine cyanine chromophore H-aggregates thin film

    Institute of Scientific and Technical Information of China (English)

    YUAN YiZhong; KANG HaiFeng; SUN ZhenRong; WANG ZuGeng

    2007-01-01

    The thin film of a heptamethine cyanine chromophore HC was prepared by spin-coating technique. Its surface morphology and linear optical property were characterized by atomic force microscopy (AFM) and UV-visible absorption spectroscopy. The results show that HC molecules are arranged in a well-ordered H-aggregate type. The third-order nonlinear optical properties of the spin-coating film were also measured by degenerate four-wave mixing (DFWM) measurement. Enhanced third-order nonlinear susceptibility can be attributed to molecular aggregation effects, and the corresponding mechanism was dealt with by collective electronic oscillator (CEO) approach.

  16. Synthesis of an Orthogonal Topological Analogue of Helicene

    DEFF Research Database (Denmark)

    Wixe, Torbjörn; Wallentin, Carl‐Johan; Johnson, Magnus T.

    2013-01-01

    The synthesis of an orthogonal topological pentamer analogue of helicene is presented. This analogue forms a tubular structure with its aromatic systems directed parallel to the axis of propagation, which creates a cavity with the potential to function as a host molecule. The synthetic strategy r...

  17. Functional Analysis: The Use of Analogues in Applied Settings.

    Science.gov (United States)

    Stichter, Janine Peck

    2001-01-01

    This article suggests possible applications of experimental analyses using analogues to empirically verify results of functional assessments in classrooms for students with autism and related disabilities. Analogue assessments involve creating conditions in which antecedents and consequences are held constant and specific variables suspected to…

  18. Black Hole Analogue in Bose–Einstein Condensation

    Indian Academy of Sciences (India)

    Tangmei He

    2014-09-01

    We have proposed a black hole analogue in a Bose–Einstein condensation. By introducing the Painlevé co-ordinates and using K–G equations, we have obtained the critical temperature of the black hole analogue in a Bose–Einstein condensation.

  19. Dipeptide analogues containing 4-ethoxy-3-pyrrolin-2-ones

    DEFF Research Database (Denmark)

    Hosseini, Masood; Kringelum, Henriette; Murray, A.;

    2006-01-01

    Pyrrolidine-2,4-diones (1) are naturally occurring analogues of amino acids. We herein present a facile synthesis of N-acylated, O-alkylated pyrrolin-2-ones (2) in high yield and excellent enantiopurity. Molecular mechanics calculations suggest that the resulting dipeptide analogues adopt a linea...

  20. Insulin analogues and severe hypoglycaemia in type 1 diabetes

    DEFF Research Database (Denmark)

    Kristensen, P L; Hansen, L S; Jespersen, M J

    2012-01-01

    The effect of insulin analogues on glycaemic control is well-documented, whereas the effect on avoidance of severe hypoglycaemia remains tentative. We studied the frequency of severe hypoglycaemia in unselected patients with type 1 diabetes treated with insulin analogues, human insulin, or mixed...

  1. Ultrafast excited state dynamics of Pt(II) chromophores bearing multiple infrared absorbers.

    Science.gov (United States)

    Glik, Elena A; Kinayyigit, Solen; Ronayne, Kate L; Towrie, Michael; Sazanovich, Igor V; Weinstein, Julia A; Castellano, Felix N

    2008-08-04

    The paper reports the synthesis, structural characterization, electrochemistry, ultrafast time-resolved infrared (TRIR) and transient absorption (TA) spectroscopy associated with two independent d (8) square planar Pt(II) diimine chromophores, Pt(dnpebpy)Cl 2 ( 1) and Pt(dnpebpy)(C[triple bond]Cnaph) 2 ( 2), where dnpebpy = 4,4'-(CO 2CH 2- (t) Bu) 2-2,2'-bipyridine and CCnaph = naphthylacetylide. The neopentyl ester substitutions provided markedly improved complex solubility relative to the corresponding ethyl ester which facilitates synthetic elaboration as well as spectroscopic investigations. Following 400 nm pulsed laser excitation in CH 2Cl 2, the 23 cm (-1) red shift in the nu C=O vibrations in 1 are representative of a complex displaying a lowest charge-transfer-to-diimine (CT) excited state. The decay kinetics in 1 are composed of two time constants assigned to vibrational cooling of the (3)CT excited-state concomitant with its decay to the ground state (tau = 2.2 +/- 0.4 ps), and to cooling of the formed vibrationally hot ground electronic state (tau = 15.5 +/- 4.0 ps); we note that an assignment of the latter to a ligand field state cannot be excluded. Ultrafast TA data quantitatively support these assignments yielding an excited-state lifetime of 2.7 +/- 0.4 ps for the (3)CT excited-state of 1 and could not detect any longer-lived species. The primary intention of this study was to develop a Pt (II) complex ( 2) bearing dual infrared spectroscopic tags (C[triple bond]C attached to the metal and CO (ester) attached to the diimine ligand) to independently track the movement of charge density in different segments of the molecule following pulsed light excitation. Femtosecond laser excitation of 2 in CH 2Cl 2 at 400 nm simultaneously induces a red-shift in both the nu C=O (-30 cm (-1)) and the nu C[triple bond]C (-61 cm (-1)) vibrations. The TRIR data in 2 are consistent with a charge transfer assignment, and the significant decrease of the energy of the nu

  2. The crystal structure of the Leishmania major deoxyuridine triphosphate nucleotidohydrolase in complex with nucleotide analogues, dUMP, and deoxyuridine.

    Science.gov (United States)

    Hemsworth, Glyn R; Moroz, Olga V; Fogg, Mark J; Scott, Benjamin; Bosch-Navarrete, Cristina; González-Pacanowska, Dolores; Wilson, Keith S

    2011-05-06

    Members of the Leishmania genus are the causative agents of the life-threatening disease leishmaniasis. New drugs are being sought due to increasing resistance and adverse side effects with current treatments. The knowledge that dUTPase is an essential enzyme and that the all α-helical dimeric kinetoplastid dUTPases have completely different structures compared with the trimeric β-sheet type dUTPase possessed by most organisms, including humans, make the dimeric enzymes attractive drug targets. Here, we present crystal structures of the Leishmania major dUTPase in complex with substrate analogues, the product dUMP and a substrate fragment, and of the homologous Campylobacter jejuni dUTPase in complex with a triphosphate substrate analogue. The metal-binding properties of both enzymes are shown to be dependent upon the ligand identity, a previously unseen characteristic of this family. Furthermore, structures of the Leishmania enzyme in the presence of dUMP and deoxyuridine coupled with tryptophan fluorescence quenching indicate that occupation of the phosphate binding region is essential for induction of the closed conformation and hence for substrate binding. These findings will aid in the development of dUTPase inhibitors as potential new lead anti-trypanosomal compounds.

  3. Oligosaccharide and Substrate Binding in the Starch Debranching Enzyme Barley Limit Dextrinase

    DEFF Research Database (Denmark)

    Møller, Marie Sofie; Windahl, Michael Skovbo; Sim, Lyann;

    2015-01-01

    Complete hydrolytic degradation of starch requires hydrolysis of both the α-1,4- and α-1,6-glucosidic bonds in amylopectin. Limit dextrinase (LD) is the only endogenous barley enzyme capable of hydrolyzing the α-1,6-glucosidic bond during seed germination, and impaired LD activity inevitably...... reduces the maltose and glucose yields from starch degradation. Crystal structures of barley LD and active-site mutants with natural substrates, products and substrate analogues were sought to better understand the facets of LD-substrate interactions that αconfine high activity of LD to branched...... starch synthesis....

  4. Tren-based analogues of bacillibactin: structure and stability.

    Science.gov (United States)

    Dertz, Emily A; Xu, Jide; Raymond, Kenneth N

    2006-07-10

    Synthetic analogues were designed to highlight the effect of the glycine moiety of bacillibactin on the overall stability of the ferric complex as compared to synthetic analogues of enterobactin. Insertion of a variety of amino acids to catecholamide analogues based on a Tren (tris(2-aminoethyl)amine) backbone increased the overall acidity of the ligands, causing an enhancement of the stability of the resulting ferric complex as compared to TRENCAM. Solution thermodynamic behavior of these siderophores and their synthetic analogues was investigated through potentiometric and spectrophotometric titrations. X-ray crystallography, circular dichroism, and molecular modeling were used to determine the chirality and geometry of the ferric complexes of bacillibactin and its analogues. In contrast to the Tren scaffold, addition of a glycine to the catechol chelating arms causes an inversion of the trilactone backbone, resulting in opposite chiralities of the two siderophores and a destabilization of the ferric complex of bacillibactin compared to ferric enterobactin.

  5. Gravitational analogue of the Witten effect

    Energy Technology Data Exchange (ETDEWEB)

    Foda, O. (International Centre for Theoretical Physics, Trieste (Italy))

    1985-07-22

    In the presence of massive fermions, and assuming a non-vanishing theta-parameter as the only source of CP violation, the Witten effect (a shift in the electric charge of a magnetic monopole due to CP non-conservation) is shown to follow from an anomalous chiral commutator. Next, given the gravitational contribution to the chiral anomaly, the corresponding anomalous commutator for Dirac fermion currents in a gravitational background is derived. From that, we infer the equivalence of a thetaR tildeR term in the lagrangian to a shift in the mass parameter of the NUT metric, in proportion to theta. This is interpreted as the gravitational analogue of the Witten effect. Its relevance to certain Kaluza-Klein monopoles is briefly discussed.

  6. Electromagnetic wave analogue of electronic diode

    CERN Document Server

    Shadrivov, Ilya V; Kivshar, Yuri S; Fedotov, Vassili A; Zheludev, Nikolay I

    2010-01-01

    An electronic diode is a nonlinear semiconductor circuit component that allows conduction of electrical current in one direction only. A component with similar functionality for electromagnetic waves, an electromagnetic isolator, is based on the Faraday effect of the polarization state rotation and is also a key component of optical and microwave systems. Here we demonstrate a chiral electromagnetic diode, which is a direct analogue of an electronic diode: its functionality is underpinned by an extraordinary strong nonlinear wave propagation effect in the same way as electronic diode function is provided by a nonlinear current characteristic of a semiconductor junction. The effect exploited in this new electromagnetic diode is an intensity-dependent polarization change in an artificial chiral metamolecule. This microwave effect exceeds a similar optical effect previously observed in natural crystals by more than 12 orders of magnitude and a direction-dependent transmission that differing by a factor of 65.

  7. New pentamidine analogues in medicinal chemistry.

    Science.gov (United States)

    Porcheddu, A; Giacomelli, G; De Luca, L

    2012-01-01

    Sixty years after its introduction, 1,5-bis(4-amidinophenoxy)pentane (Pentamidine) is still one of the most used drugs for the treatment of the first stage of Human African trypanosomiasis and other neglected diseases such as malaria and leishmaniasis. These protozoan infections are prevalent in the poorest world areas such as sub-saharian and developing countries, however the increasing immigration from these countries to the richest part of the world and the overlap of HIV with parasitic infections result in a growing number of cases in developed nations. A great effort has been made to develop new generations of diamidines for the treatment of these infections transmitted by insects. This review summarises the synthesis and evaluation of pentamidine analogues reported in the last years in the effort to find new drugs with better pharmaceutical activity, higher lipophilicity and lower citotoxycicty.

  8. Helical chirality induction of expanded porphyrin analogues

    Indian Academy of Sciences (India)

    Jun-Ichiro Setsune

    2012-11-01

    Expanded porphyrin analogues with unique figure-eight conformation were prepared by way of useful pyrrole intermediates such as bis(azafulvene)s and 2-borylpyrrole. Supramolecular chirogenesis of cyclooctapyrrole O1 with 32-cycloconjugation was successfully applied to determine absolute configuration of chiral carboxylic acids. Dinuclear CuII complex of cyclooctapyrrole O2 with interrupted -conjugation was resolved by HPLC into enantiomers and their helical handedness was determined by theoretical simulation of their CD spectral pattern. Enantioselective induction of helicity in the metal helicate formation in the presence of a chiral promoter was demonstrated by using ()-(+)-1-(1-phenyl)ethylamine that favoured , helicity. Dinuclear CoII complexes of cyclotetrapyrroletetrapyridine O3 were found to be substitution labile and pick up amino acid anions in water. Those amino acid complexes of O3Co2 were rendered to adopt a particular unidirectional helical conformation preferentially depending on the ligated amino acid anion.

  9. Terrestrial analogues for lunar impact melt flows

    Science.gov (United States)

    Neish, C. D.; Hamilton, C. W.; Hughes, S. S.; Nawotniak, S. Kobs; Garry, W. B.; Skok, J. R.; Elphic, R. C.; Schaefer, E.; Carter, L. M.; Bandfield, J. L.; Osinski, G. R.; Lim, D.; Heldmann, J. L.

    2017-01-01

    Lunar impact melt deposits have unique physical properties. They have among the highest observed radar returns at S-Band (12.6 cm wavelength), implying that they are rough at the decimeter scale. However, they are also observed in high-resolution optical imagery to be quite smooth at the meter scale. These characteristics distinguish them from well-studied terrestrial analogues, such as Hawaiian pāhoehoe and ´a´ā lava flows. The morphology of impact melt deposits can be related to their emplacement conditions, so understanding the origin of these unique surface properties will help to inform us as to the circumstances under which they were formed. In this work, we seek to find a terrestrial analogue for well-preserved lunar impact melt flows by examining fresh lava flows on Earth. We compare the radar return and high-resolution topographic variations of impact melt flows to terrestrial lava flows with a range of surface textures. The lava flows examined in this work range from smooth Hawaiian pāhoehoe to transitional basaltic flows at Craters of the Moon (COTM) National Monument and Preserve in Idaho to rubbly and spiny pāhoehoe-like flows at the recent eruption at Holuhraun in Iceland. The physical properties of lunar impact melt flows appear to differ from those of all the terrestrial lava flows studied in this work. This may be due to (a) differences in post-emplacement modification processes or (b) fundamental differences in the surface texture of the melt flows due to the melts' unique emplacement and/or cooling environment. Information about the surface properties of lunar impact melt deposits will be critical for future landed missions that wish to sample these materials.

  10. MAQARIN natural analogue study: phase III

    Energy Technology Data Exchange (ETDEWEB)

    Alexander, W.R.; Mazurek, M.; Waber, H.N. [Univ. of Berne (Switzerland). Institutes of Geology, Mineralogy and Petrology, Rock-Water Interaction Group (GGWW); Arlinger, J.; Erlandson, A.C.; Hallbeck, L.; Pedersen, K. [Goeteborg Univ. (Sweden). Dept. of General and Marine Microbiology; Boehlmann, W.; Fritz, P.; Geyer, S.; Geyer, W.; Hanschman, G.; Kopinke, F.D.; Poerschmann, J. [Umweltforschungszentrum Leipzig-Halle (Germany); Chambers, A.V.; Haworth, A.; Ilett, D.; Linklater, C.M.; Tweed, C.J. [AEA Technology plc, Harwell (United Kingdom); Chenery, S.R.N.; Kemp, S.J.; Milodowski, A.E.; Pearce, J.M.; Reeder, S.; Rochelle, C.A.; Smith, B.; Wetton, P.D.; Wragg, J. [British Geological Survey, Keyworth (United Kingdom); Clark, I.D. [Univ. of Ottawa (Canada). Dept. of Geology; Hodginson, E.; Hughes, C.R. [Univ. of Manchester (United Kingdom). Dept. of Earth Sciences; Hyslop, E.K. [British Geological Survey, Edinburgh (United Kingdom); Karlsson, F. [Swedish Nuclear Fuel and Waste Management Co., Stockholm (Sweden); Khoury, H.N.; Salameh, E. [Univ. of Jordan, Amman (Jordan); Lagerblad, B. [Cement Inst., Stockholm (Sweden); Longworth, G. [Univ. of Manchester (United Kingdom). Dept. of Geology; Pitty, A.F. [Private consultant, Norwich (United Kingdom); Savage, D. [QuantiSci Ltd, Melton Mowbray (United Kingdom); Smellie, J.A.T. [ed.] [Conterra AB, Uppsala (Sweden)

    1998-12-01

    This report represents the conclusion to Phase III of the Maqarin Natural Analogue Study. The main thrust was to establish the origin and chemistry of the Western Springs hyper alkaline groundwaters (Na/K enriched Ca(OH){sub 2} type) and to study their interaction with rocks of different compositions, as natural analogues to key processes that might occur at an early stage within the `alkali disturbed zone` of cementitious repositories in different host rocks. Whilst earlier studies at Maqarin were very much site-specific and process-oriented, Phase III provided a regional perspective to the geological evolution of the Maqarin region. This was made possible by greater field access which allowed a more systematic structural and geomorphological study of the area. This has resulted in a greater understanding of the age and spatial relationships concerning formation of the cement zones through spontaneous combustion of the Bituminous Marls, and the subsequent formation of high pH groundwaters at the Eastern and Western Springs locations. At the Western Springs locality, hydrochemical and hydrogeological evaluation of new and published data (plus access to unpublished data), together with detailed mineralogical and geochemical studies, helped to clarify the very earliest stage of cement leachate/host rock interaction. The data were used also to test coupled flow/transport codes developed to assess the long-term evolution of a cementitious repository. Additional objectives addressed include: a) rock matrix diffusion, b) the occurrence and chemical controls on zeolite composition, e) the occurrence and chemical controls on clay stability, and d) the role of microbes, organics and colloids in trace element transport. The Maqarin site now provides a consistent picture explaining the origin of the hyperalkaline groundwaters, and is therefore a unique location for the examination of the mechanisms and processes associated with cementitious repositories. Application of these

  11. Current european regulatory perspectives on insulin analogues

    Directory of Open Access Journals (Sweden)

    Enzmann Harald G

    2011-07-01

    Full Text Available Abstract Insulin analogues are increasingly considered as an alternative to human insulin in the therapy of diabetes mellitus. Insulin analogues (IAs are chemically different from human insulin and may have different pharmacokinetic or pharmacodynamic properties. The significance of the modifications of the insulin molecule for the safety profile of IAs must be considered. This review describes the regulatory procedure and the expectations for the scientific content of European marketing authorization applications for innovative IAs submitted to the European Medicines Agency. Particular consideration is given to a potential cancer hazard. Specific regulatory guidance on how to address a possible carcinogenic or tumor promoting effect of innovative IAs in non-clinical studies is available. After marketing authorization, the factual access of patients to the new product will be determined to great extent by health technology assessment bodies, reimbursement decisions and the price. Whereas the marketing authorization is a European decision, pricing and reimbursement are national or regional responsibilities. The assessment of benefit and risk by the European Medicines Agency is expected to influence future decisions on price and reimbursement on a national or regional level. Collaborations between regulatory agencies and health technology assessment bodies have been initiated on European and national level to facilitate the use of the European Medicines Agency's benefit risk assessment as basis on which to build the subsequent health technology assessment. The option for combined or joint scientific advice procedures with regulators and health technology assessment bodies on European level or on a national level in several European Member States may help applicants to optimize their development program and dossier preparation in regard of both European marketing authorization application and reimbursement decisions.

  12. MAQARIN natural analogue study: phase III

    Energy Technology Data Exchange (ETDEWEB)

    Alexander, W.R.; Mazurek, M.; Waber, H.N. [Univ. of Berne (Switzerland). Institutes of Geology, Mineralogy and Petrology, Rock-Water Interaction Group (GGWW); Arlinger, J.; Erlandson, A.C.; Hallbeck, L.; Pedersen, K. [Goeteborg University (Sweden). Dept. of General and Marine Microbiology; Boehlmann, W.; Fritz, P.; Geyer, S.; Geyer, W.; Hanschman, G.; Kopinke, F.D.; Poerschmann, J. [Umweltforschungszentrum Leipzig-Halle (Germany); Chambers, A.V.; Haworth, A.; Ilett, D.; Linklater, C.M.; Tweed, C.J. [AEA Technology plc, Harwell (United Kingdom); Chenery, S.R.N.; Kemp, S.J.; Milodowski, A.E.; Pearce, J.M.; Reeder, S.; Rochelle, C.A.; Smith, B.; Wetton, P.D.; Wragg, J. [British Geological Survey, Keyworth (United Kingdom); Clark, I.D. [Univ. of Ottawa (Canada). Dept. of Geology; Hodginson, E.; Hughes, C.R. [Univ. of Manchester (United Kingdom). Dept. of Earth Sciences; Hyslop, E.K. [British Geological Survey, Edinburgh (United Kingdom); Karlsson, F. [Swedish Nuclear Fuel and Waste Management Co., Stockholm (Sweden); Khoury, H.N.; Salameh, E. [Univ. of Jordan, Amman (Jordan); Lagerblad, B. [Cement Institute, Stockholm (Sweden); Longworth, G. [Univ. of Manchester (United Kingdom). Dept. of Geology; Pitty, A.F. [Private consultant, Norwich (United Kingdom); Savage, D. [QuantiSci Ltd, Melton Mowbray (United Kingdom); Smellie, J.A.T. [ed.] [Conterra AB, Uppsala (Sweden)

    1998-12-01

    This report represents the conclusion to Phase III of the Maqarin Natural Analogue Study. The main thrust was to establish the origin and chemistry of the Western Springs hyper alkaline groundwaters (Na/K enriched Ca(OH){sub 2} type) and to study their interaction with rocks of different compositions, as natural analogues to key processes that might occur at an early stage within the `alkali disturbed zone` of cementitious repositories in different host rocks. Whilst earlier studies at Maqarin were very much site-specific and process-oriented, Phase III provided a regional perspective to the geological evolution of the Maqarin region. This was made possible by greater field access which allowed a more systematic structural and geomorphological study of the area. This has resulted in a greater understanding of the age and spatial relationships concerning formation of the cement zones through spontaneous combustion of the Bituminous Marls, and the subsequent formation of high pH groundwaters at the Eastern and Western Springs locations. At the Western Springs locality, hydrochemical and hydrogeological evaluation of new and published data (plus access to unpublished data), together with detailed mineralogical and geochemical studies, helped to clarify the very earliest stage of cement leachate/host rock interaction. The data were used also to test coupled flow/transport codes developed to assess the long-term evolution of a cementitious repository. Additional objectives addressed include: a) rock matrix diffusion, b) the occurrence and chemical controls on zeolite composition, e) the occurrence and chemical controls on clay stability, and d) the role of microbes, organics and colloids in trace element transport. The Maqarin site now provides a consistent picture explaining the origin of the hyperalkaline groundwaters, and is therefore a unique location for the examination of the mechanisms and processes associated with cementitious repositories. Application of these

  13. Natural analogues of nuclear waste glass corrosion.

    Energy Technology Data Exchange (ETDEWEB)

    Abrajano, T.A. Jr.; Ebert, W.L.; Luo, J.S.

    1999-01-06

    This report reviews and summarizes studies performed to characterize the products and processes involved in the corrosion of natural glasses. Studies are also reviewed and evaluated on how well the corrosion of natural glasses in natural environments serves as an analogue for the corrosion of high-level radioactive waste glasses in an engineered geologic disposal system. A wide range of natural and experimental corrosion studies has been performed on three major groups of natural glasses: tektite, obsidian, and basalt. Studies of the corrosion of natural glass attempt to characterize both the nature of alteration products and the reaction kinetics. Information available on natural glass was then compared to corresponding information on the corrosion of nuclear waste glasses, specifically to resolve two key questions: (1) whether one or more natural glasses behave similarly to nuclear waste glasses in laboratory tests, and (2) how these similarities can be used to support projections of the long-term corrosion of nuclear waste glasses. The corrosion behavior of basaltic glasses was most similar to that of nuclear waste glasses, but the corrosion of tektite and obsidian glasses involves certain processes that also occur during the corrosion of nuclear waste glasses. The reactions and processes that control basalt glass dissolution are similar to those that are important in nuclear waste glass dissolution. The key reaction of the overall corrosion mechanism is network hydrolysis, which eventually breaks down the glass network structure that remains after the initial ion-exchange and diffusion processes. This review also highlights some unresolved issues related to the application of an analogue approach to predicting long-term behavior of nuclear waste glass corrosion, such as discrepancies between experimental and field-based estimates of kinetic parameters for basaltic glasses.

  14. Analogue to Digital and Digital to Analogue (AD/DA) Conversion Techniques: An Overview

    CERN Document Server

    CERN. Geneva

    2002-01-01

    The basic ideas behind modern Analogue to Digital and Digital to Analogue (AD/DA) conversion methods will be introduced: a general view of the importance of these devices will be given, along with the digital representation of time-varying, real-world analogue signals. Some CERN applications will be outlined. The variety of conversion methods, their limitations, error sources and measurement methods will form the major part of this presentation. A review of the technological progress in this field over the last 30 years will be presented, concluding with the present 'state of the art' and a quick look at what is just around the corner. This Technical Training Seminar is in the framework of the FEED-2002 Lecture Series, and it is a prerequisite to attending to any of the FEED-2002 Terms. FEED-2002 is a two-term course that will review the techniques dealing with closed loop systems, focussing on time-invariant linear systems. (free attendance, no registration required) More information on the FEED-2002 ...

  15. Synthesis and characterization of thermally stable second-order nonlinear optical side-chain polyimides containing thiazole and benzothiazole push-pull chromophores

    Science.gov (United States)

    Tambe, S. M.; Kittur, A. A.; Inamdar, S. R.; Mitchell, G. R.; Kariduraganavar, M. Y.

    2009-04-01

    Push-pull nonlinear optical (NLO) chromophores containing thiazole and benzothiazole acceptors were synthesized and characterized. Using these chromophores a series of second-order NLO polyimides were successfully prepared from 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), pyromellitic dianhydride (PMDA) and 3,3'4,4'-benzophenone tetracarboxylic dianhydride (BTDA) by a standard condensation polymerization technique. These polyimides exhibit high glass transition temperatures ranging from 160 to 188 °C. UV-vis spectrum of polyimide exhibited a slight blue shift and decreases in absorption due to birefringence. From the order parameters, it was found that chromophores were aligned effectively. Using in situ poling and temperature ramping technique, the optical temperatures for corona poling were obtained. It was found that the optimal temperatures of polyimides approach their glass transition temperatures. These polyimides demonstrate relatively large d33 values range between 35.15 and 45.20 pm/V at 532 nm.

  16. Experimental evidence for secondary protein-chromophore interactions at the Schiff base linkage in bacteriorhodopsin: molecular mechanism for proton pumping

    Energy Technology Data Exchange (ETDEWEB)

    Lewis, A.; Marcus, M.A.; Ehrenberg, B.; Crespi, H.

    1978-10-01

    Resonance Raman spectroscopy of the retinylidene chromophore in various isotopically labeled membrane environments together with spectra of isotopically labeled model compounds demonstrates that a secondary protein interaction is present at the protonated Schiff base linkage in bacteriorhodopsin. The data indicate that although the interaction is present in all protonated bacteriorhodopsin species it is absent in unprotonated intermediates. Furthermore, kinetic resonance Raman spectroscopy has been used to monitor the dynamics of Schiff base deprotonation as a function of pH. All results are consistent with lysine as the interacting group. A structure for the interaction is proposed in which the interacting protein group in an unprotonated configuration is complexed through the Schiff base proton to the Schiff base nitrogen. These data suggest a molecular mechanism for proton pumping and ion gate molecular regulation. In this mechanism, light causes electron redistribution in the retinylidene chromophore, which results in the deprotonation of an amino acid side chain with pK > 10.2 +- 0.3 (e.g., arginine). This induces subsequent retinal and protein conformational transitions which eventually lower the pK of the Schiff base complex from > 12 before light absorption to 10.2 +- 0.3 in microseconds after photon absorption. Finally, in this low pK state the complex can reprotonate the proton-deficient high pK group generated by light, and the complex is then reprotonated from the opposite side of the membrane.

  17. Preparation and third-order nonlinear optical property of poly(urethane-imide containing dispersed red chromophore

    Directory of Open Access Journals (Sweden)

    2008-11-01

    Full Text Available A novel poly(urethane-imide (PUI containing dispersed red chromophore was synthesized. The PUI was characterized by FT-IR, UV-Vis, DSC and TGA. The results of DSC and TGA indicated that the PUI exhibited high thermal stability up to its glass-transition temperature (Tg of 196°C and 5% heat weight loss temperature of 229°C. According to UV-Vis spectrum and working curve, the maximum molar absorption coefficient and absorption wavelength were measured. They were used to calculate the third-order nonlinear optical coefficient χ(3. At the same time, the chromophore density of PUI, nonlinear refractive index coefficient and molecular hyperpolarizability of PUI were obtained. The fluorescence spectra of PUI and model compound DR-19 were determined at excitation wavelength 300 nm. The electron donor and acceptor in polymer formed the exciplex through the transfer of the electric charges. The results show that the poly(urethane-imide is a promising candidate for application in optical devices.

  18. Predicting dissolved lignin phenol concentrations in the coastal ocean from chromophoric dissolved organic matter (CDOM absorption coefficients

    Directory of Open Access Journals (Sweden)

    Cédric G. Fichot

    2016-02-01

    Full Text Available Dissolved lignin is a well-established biomarker of terrigenous dissolved organic matter (DOM in the ocean, and a chromophoric component of DOM. Although evidence suggests there is a strong linkage between lignin concentrations and chromophoric DOM (CDOM absorption coefficients in coastal waters, the characteristics of this linkage and the existence of a relationship that is applicable across coastal oceans remain unclear. Here, 421 paired measurements of dissolved lignin concentrations (sum of 9 lignin phenols and CDOM absorption coefficients (ag(λ were used to examine their relationship along the river-ocean continuum (0-37 salinity and across contrasting coastal oceans (sub-tropical, temperate, high-latitude. Overall, lignin concentrations spanned four orders of magnitude and revealed a strong, non-linear relationship with ag(λ. The characteristics of the relationship (shape, wavelength dependency, lignin-composition dependency and evidence from degradation indicators were all consistent with lignin being an important driver of CDOM variability in coastal oceans, and suggested physical mixing and long-term photodegradation were important in shaping the relationship. These observations were used to develop two simple empirical models for estimating lignin concentrations from ag(λ with a +/- 20% error relative to measured values. The models are expected to be applicable in most coastal oceans influenced by terrigenous inputs.

  19. Novel hybrid organic-inorganic sol-gel materials based on highly efficient heterocyclic push-pull chromophores

    Science.gov (United States)

    Abbotto, Alessandro; Bozio, Renato; Brusatin, Giovanna; Facchetti, Antonio; Guglielmi, Massimo; Innocenzi, Plinio; Meneghetti, Moreno; Pagani, Giorgio A.; Signorini, Raffaella

    1999-10-01

    We report the synthesis of sol-gel materials based on highly efficient heterocycle-based push-pull chromophores showing second- and third-order nonlinear optical activity. We show the proper functionalization of the best performing chromophores and their incorporation into a hybrid organic- inorganic sol-gel matrix. Different types of functionalization of the active molecule have been considered, including hydroxyl and alkoxysilyl end-groups. The functionalization strategy responded to different criteria such as stability and synthetic availability of the final molecular precursors, their solubility, and the used synthetic approach to the sol-gel material. The synthesis of the sol-gel materials has been tuned in order to preserve molecular properties and control important factors such as final concentration of the active dye in the matrix. Both acid- and base-catalyzed sol-gel synthesis has been taken into account. 3-Glycidoxypropyltrimethoxysilane and 3- aminopropyltriethoxysilane have been used as the organically modified alkoxides to prepare the hybrid organic-inorganic matrix. Characterization of the spectroscopic properties of the sol-gel materials is presented.

  20. Versatile design of biohybrid light-harvesting architectures to tune location, density, and spectral coverage of attached synthetic chromophores for enhanced energy capture.

    Science.gov (United States)

    Harris, Michelle A; Jiang, Jianbing; Niedzwiedzki, Dariusz M; Jiao, Jieying; Taniguchi, Masahiko; Kirmaier, Christine; Loach, Paul A; Bocian, David F; Lindsey, Jonathan S; Holten, Dewey; Parkes-Loach, Pamela S

    2014-07-01

    Biohybrid antennas built upon chromophore-polypeptide conjugates show promise for the design of efficient light-capturing modules for specific purposes. Three new designs, each of which employs analogs of the β-polypeptide from Rhodobacter sphaeroides, have been investigated. In the first design, amino acids at seven different positions on the polypeptide were individually substituted with cysteine, to which a synthetic chromophore (bacteriochlorin or Oregon Green) was covalently attached. The polypeptide positions are at -2, -6, -10, -14, -17, -21, and -34 relative to the 0-position of the histidine that coordinates bacteriochlorophyll a (BChl a). All chromophore-polypeptides readily formed LH1-type complexes upon combination with the α-polypeptide and BChl a. Efficient energy transfer occurs from the attached chromophore to the circular array of 875 nm absorbing BChl a molecules (denoted B875). In the second design, use of two attachment sites (positions -10 and -21) on the polypeptide affords (1) double the density of chromophores per polypeptide and (2) a highly efficient energy-transfer relay from the chromophore at -21 to that at -10 and on to B875. In the third design, three spectrally distinct bacteriochlorin-polypeptides were prepared (each attached to cysteine at the -14 position) and combined in an ~1:1:1 mixture to form a heterogeneous mixture of LH1-type complexes with increased solar coverage and nearly quantitative energy transfer from each bacteriochlorin to B875. Collectively, the results illustrate the great latitude of the biohybrid approach for the design of diverse light-harvesting systems.

  1. Lake and sea populations of Mysis relicta (Crustacea, Mysida with different visual-pigment absorbance spectra use the same A1 chromophore.

    Directory of Open Access Journals (Sweden)

    Nikolai Belikov

    Full Text Available Glacial-relict species of the genus Mysis (opossum shrimps inhabiting both fresh-water lakes and brackish sea waters in northern Europe show a consistent lake/sea dichotomy in eye spectral sensitivity. The absorbance peak (λmax recorded by microspectrophotometry in isolated rhabdoms is invariably 20-30 nm red-shifted in "lake" compared with "sea" populations. The dichotomy holds across species, major opsin lineages and light environments. Chromophore exchange from A1 to A2 (retinal → 3,4-didehydroretinal is a well-known mechanism for red-shifting visual pigments depending on environmental conditions or stages of life history, present not only in fishes and amphibians, but in some crustaceans as well. We tested the hypothesis that the lake/sea dichotomy in Mysis is due to the use of different chromophores, focussing on two populations of M. relicta from, respectively, a Finnish lake and the Baltic Sea. They are genetically very similar, having been separated for less than 10 kyr, and their rhabdoms show a typical lake/sea difference in λmax (554 nm vs. 529 nm. Gene sequencing has revealed no differences translating into amino acid substitutions in the transmembrane parts of their opsins. We determined the chromophore identity (A1 or A2 in the eyes of these two populations by HPLC, using as standards pure chromophores A1 and A2 as well as extracts from bovine (A1 and goldfish (A2 retinas. We found that the visual-pigment chromophore in both populations is A1 exclusively. Thus the spectral difference between these two populations of M. relicta is not due to the use of different chromophores. We argue that this conclusion is likely to hold for all populations of M. relicta as well as its European sibling species.

  2. Oligosaccharide and substrate binding in the starch debranching enzyme barley limit dextrinase.

    Science.gov (United States)

    Møller, Marie S; Windahl, Michael S; Sim, Lyann; Bøjstrup, Marie; Abou Hachem, Maher; Hindsgaul, Ole; Palcic, Monica; Svensson, Birte; Henriksen, Anette

    2015-03-27

    Complete hydrolytic degradation of starch requires hydrolysis of both the α-1,4- and α-1,6-glucosidic bonds in amylopectin. Limit dextrinase (LD) is the only endogenous barley enzyme capable of hydrolyzing the α-1,6-glucosidic bond during seed germination, and impaired LD activity inevitably reduces the maltose and glucose yields from starch degradation. Crystal structures of barley LD and active-site mutants with natural substrates, products and substrate analogues were sought to better understand the facets of LD-substrate interactions that confine high activity of LD to branched maltooligosaccharides. For the first time, an intact α-1,6-glucosidically linked substrate spanning the active site of a LD or pullulanase has been trapped and characterized by crystallography. The crystal structure reveals both the branch and main-chain binding sites and is used to suggest a mechanism for nucleophilicity enhancement in the active site. The substrate, product and analogue complexes were further used to outline substrate binding subsites and substrate binding restraints and to suggest a mechanism for avoidance of dual α-1,6- and α-1,4-hydrolytic activity likely to be a biological necessity during starch synthesis.

  3. Substrate Recognition and Catalysis by the Cofactor-Independent Dioxygenase DpgC+

    Energy Technology Data Exchange (ETDEWEB)

    Fielding,E.; Widboom, P.; Bruner, S.

    2007-01-01

    The enzyme DpgC belongs to a small class of oxygenases not dependent on accessory cofactors for activity. DpgC is in the biosynthetic pathway for the nonproteinogenic amino acid 3, 5-dihydroxyphenylglycine in actinomycetes bacteria responsible for the production of the vancomycin/teicoplanin family of antibiotic natural products. The X-ray structure of DpgC confirmed the absence of cofactors and defined a novel hydrophobic dioxygen binding pocket adjacent to a bound substrate analogue. In this paper, the role specific amino acids play in substrate recognition and catalysis is examined through biochemical and structural characterization of site-specific enzyme mutations and alternate substrates. The results establish the importance of three amino acids, Arg254, Glu299, and Glu189, in the chemistry of DpgC. Arg254 and Glu189 join to form a specific contact with one of the phenolic hydroxyls of the substrate, and this interaction plays a key role in both substrate recognition and catalysis. The X-ray crystal structure of Arg254Lys was determined to address the role this residue plays in the chemistry. In addition, characterization of alternate substrate analogues demonstrates the presence and position of phenol groups are necessary for both enzyme recognition and downstream oxidation chemistry. Overall, this work defines the mechanism of substrate recognition and specificity by the cofactor-independent dioxygenase DpgC.

  4. Structure of the red fluorescent protein from a lancelet (Branchiostoma lanceolatum): a novel GYG chromophore covalently bound to a nearby tyrosine

    Energy Technology Data Exchange (ETDEWEB)

    Pletnev, Vladimir Z., E-mail: vzpletnev@gmail.com; Pletneva, Nadya V.; Lukyanov, Konstantin A.; Souslova, Ekaterina A.; Fradkov, Arkady F.; Chudakov, Dmitry M.; Chepurnykh, Tatyana; Yampolsky, Ilia V. [Russian Academy of Sciences, Moscow (Russian Federation); Wlodawer, Alexander [National Cancer Institute, Frederick, MD 21702 (United States); Dauter, Zbigniew [National Cancer Institute, Argonne, IL 60439 (United States); Pletnev, Sergei, E-mail: vzpletnev@gmail.com [National Cancer Institute, Argonne, IL 60439 (United States); SAIC-Frederick, Argonne, IL 60439 (United States); Russian Academy of Sciences, Moscow (Russian Federation)

    2013-09-01

    The crystal structure of the novel red emitting fluorescent protein from lancelet Branchiostoma lanceolatum (Chordata) revealed an unusual five residues cyclic unit comprising Gly58-Tyr59-Gly60 chromophore, the following Phe61 and Tyr62 covalently bound to chromophore Tyr59. A key property of proteins of the green fluorescent protein (GFP) family is their ability to form a chromophore group by post-translational modifications of internal amino acids, e.g. Ser65-Tyr66-Gly67 in GFP from the jellyfish Aequorea victoria (Cnidaria). Numerous structural studies have demonstrated that the green GFP-like chromophore represents the ‘core’ structure, which can be extended in red-shifted proteins owing to modifications of the protein backbone at the first chromophore-forming position. Here, the three-dimensional structures of green laGFP (λ{sub ex}/λ{sub em} = 502/511 nm) and red laRFP (λ{sub ex}/λ{sub em} ≃ 521/592 nm), which are fluorescent proteins (FPs) from the lancelet Branchiostoma lanceolatum (Chordata), were determined together with the structure of a red variant laRFP-ΔS83 (deletion of Ser83) with improved folding. Lancelet FPs are evolutionarily distant and share only ∼20% sequence identity with cnidarian FPs, which have been extensively characterized and widely used as genetically encoded probes. The structure of red-emitting laRFP revealed three exceptional features that have not been observed in wild-type fluorescent proteins from Cnidaria reported to date: (i) an unusual chromophore-forming sequence Gly58-Tyr59-Gly60, (ii) the presence of Gln211 at the position of the conserved catalytic Glu (Glu222 in Aequorea GFP), which proved to be crucial for chromophore formation, and (iii) the absence of modifications typical of known red chromophores and the presence of an extremely unusual covalent bond between the Tyr59 C{sup β} atom and the hydroxyl of the proximal Tyr62. The impact of this covalent bond on the red emission and the large Stokes shift (

  5. Accurate Spectral Fits of Jupiter's Great Red Spot: VIMS Visual Spectra Modelled with Chromophores Created by Photolyzed Ammonia Reacting with Acetyleneχ±

    Science.gov (United States)

    Baines, Kevin; Sromovsky, Lawrence A.; Fry, Patrick M.; Carlson, Robert W.; Momary, Thomas W.

    2016-10-01

    We report results incorporating the red-tinted photochemically-generated aerosols of Carlson et al (2016, Icarus 274, 106-115) in spectral models of Jupiter's Great Red Spot (GRS). Spectral models of the 0.35-1.0-micron spectrum show good agreement with Cassini/VIMS near-center-meridian and near-limb GRS spectra for model morphologies incorporating an optically-thin layer of Carlson (2016) aerosols at high altitudes, either at the top of the tropospheric GRS cloud, or in a distinct stratospheric haze layer. Specifically, a two-layer "crème brûlée" structure of the Mie-scattering Carlson et al (2016) chromophore attached to the top of a conservatively scattering (hereafter, "white") optically-thick cloud fits the spectra well. Currently, best agreement (reduced χ2 of 0.89 for the central-meridian spectrum) is found for a 0.195-0.217-bar, 0.19 ± 0.02 opacity layer of chromophores with mean particle radius of 0.14 ± 0.01 micron. As well, a structure with a detached stratospheric chromophore layer ~0.25 bar above a white tropospheric GRS cloud provides a good spectral match (reduced χ2 of 1.16). Alternatively, a cloud morphology with the chromophore coating white particles in a single optically- and physically-thick cloud (the "coated-shell model", initially explored by Carlson et al 2016) was found to give significantly inferior fits (best reduced χ2 of 2.9). Overall, we find that models accurately fit the GRS spectrum if (1) most of the optical depth of the chromophore is in a layer near the top of the main cloud or in a distinct separated layer above it, but is not uniformly distributed within the main cloud, (2) the chromophore consists of relatively small, 0.1-0.2-micron-radius particles, and (3) the chromophore layer optical depth is small, ~ 0.1-0.2. Thus, our analysis supports the exogenic origin of the red chromophore consistent with the Carlson et al (2016) photolytic production mechanism rather than an endogenic origin, such as upwelling of material

  6. A mutasynthesis approach with a Penicillium chrysogenum ΔroqA strain yields new roquefortine D analogues.

    Science.gov (United States)

    Ouchaou, Kahina; Maire, Florian; Salo, Oleksandr; Ali, Hazrat; Hankemeier, Thomas; van der Marel, Gijsbert A; Filippov, Dmitri V; Bovenberg, Roel A L; Vreeken, Rob J; Driessen, Arnold J M; Overkleeft, Herman S

    2015-04-13

    Penicillium chrysogenum, which lacks the roqA gene, processes synthetic, exogenously added histidyltryptophanyldiketopiperazine (HTD) to yield a set of roquefortine-based secondary metabolites also produced by the wild-type strain. Feeding a number of synthetic HTD analogues to the ΔroqA strain gives rise to the biosynthesis of a number of new roquefortine D derivatives, depending on the nature of the synthetic HTD added. Besides delivering semisynthetic roquefortine analogues, the mutasynthesis studies presented here also shed light on the substrate preferences and molecular mechanisms employed by the roquefortine C/D biosynthesis gene cluster, knowledge that may be tapped for the future development of more complex semisynthetic roquefortine-based secondary metabolites.

  7. The Greenland Analogue Project. Yearly Report 2009

    Energy Technology Data Exchange (ETDEWEB)

    2010-12-15

    A deep geological repository for spent nuclear fuel needs to be designed to keep used nuclear fuel isolated from mankind and the environment for a million years. Within this time frame glacial conditions are expected in regions that have been glaciated in the past two to ten million years. Climate induced changes such as the growth of ice sheets and permafrost will influence and alter the ground surface and subsurface environment, including its hydrology, which may impact repository safety. Glaciation impact assessments have to-date used over-simplified models and conservative assumptions, for example in the representation of ice sheet hydrology, that do not reflect the complexity of natural systems and processes. This is largely due to lack of direct observations of such processes from existing ice sheets, which if more readily available could help reduce uncertainties and provide a strong scientific basis for the treatment of glacial impacts in safety assessments. Our current understanding of the hydrological, hydrogeological and hydrogeochemical processes associated with glacial cycles and their impact on the long-term performance of deep geological repositories for spent nuclear fuel will be significantly improved by studying a modern analogue. To advance the understanding of processes associated with glaciation and their impact on the long-term performance of a deep geological repository, the Greenland Analogue Project (GAP), a four-year field and modelling study of the Greenland ice sheet and sub-surface conditions, has been initiated collaboratively by SKB, Posiva and NWMO. The study site encompasses a land terminus portion of the Greenland ice sheet east of Kangerlussuaq and is in many ways considered to be an appropriate analogue of the conditions that are expected to prevail in much of Canada and Fennoscandia during future glacial cycles. The project is planned to run from 2009 until 2012. The GAP will conduct the first in situ investigations of some of

  8. A Low-cost Multi-channel Analogue Signal Generator

    CERN Document Server

    Müller, F; The ATLAS collaboration; Shen, W; Stamen, R

    2009-01-01

    A scalable multi-channel analogue signal generator is presented. It uses a commercial low-cost graphics card with multiple outputs in a standard PC as signal source. Each color signal serves as independent channel to generate an analogue signal. A custom-built external PCB was developed to adjust the graphics card output voltage levels for a specific task, which needed differential signals. The system furthermore comprises a software package to program the signal shape. The signal generator was successfully used as independent test bed for the ATLAS Level-1 Trigger Pre-Processor, providing up to 16 analogue signals.

  9. Geometries and Vertical Excitation Energies in Retinal Analogues Resolved at the CASPT2 Level of Theory: Critical Assessment of the Performance of CASSCF, CC2, and DFT Methods.

    Science.gov (United States)

    Walczak, Elżbieta; Szefczyk, Borys; Andruniów, Tadeusz

    2013-11-12

    A systematic investigation of structural properties and vertical excitation energies of a series of structurally modified 11-cis-retinal chromophores in vacuo was performed by means of multiconfigurational second-order perturbation theory (CASPT2). CASPT2-based geometries agree reasonably well with Møller-Plesset second-order perturbation theory (MP2), local second-order approximate coupled cluster singles and doubles (LCC2), and density functional theory (DFT) geometries, while the complete active space self-consistent field (CASSCF) method exaggerates dramatically the bond length pattern in the polyene chain. The quality of the resulting vertical excitation energies obtained by employing CASSCF, second-order approximate coupled cluster singles and doubles (CC2), LCC2, and time-dependent density functional theory (TD-DFT) approaches is assessed with respect to the CASPT2 data. We show that the commonly used CASSCF/CASPT2 approach works reasonably well in the case of vertical excitation energies of planar structures, but lack of dynamic correlation leads to large errors in energetics for strongly strained structures. For example, the highly twisted conformers of 9,10-dimethyl and 9,10,13-trimethyl species are found as global minima at the CASSCF level, whereas they turn almost planar at the CASPT2, MP2, LCC2, and DFT levels of theory. The CC2 method has shown a remarkable performance, manifested by a maximum deviation of 0.05 eV from the reference CASPT2 results, whereas the local version of CC2 seems to fail to describe the charge-transfer character of the S0 → S1 transitions correctly. We believe that our CASPT2 benchmark set will provide a reference that can be utilized for validation and development studies on 11-cis-retinal protonated Schiff base chromophore analogues.

  10. A positive Grassmannian analogue of the permutohedron

    CERN Document Server

    Williams, Lauren K

    2015-01-01

    The classical permutohedron Perm is the convex hull of the points (w(1),...,w(n)) in R^n where w ranges over all permutations in the symmetric group. This polytope has many beautiful properties -- for example it provides a way to visualize the weak Bruhat order: if we orient the permutohedron so that the longest permutation w_0 is at the "top" and the identity e is at the "bottom," then the one-skeleton of Perm is the Hasse diagram of the weak Bruhat order. Equivalently, the paths from e to w_0 along the edges of Perm are in bijection with the reduced decompositions of w_0. Moreover, the two-dimensional faces of the permutohedron correspond to braid and commuting moves, which by the Tits Lemma, connect any two reduced expressions of w_0. In this note we introduce some polytopes Br(k,n) (which we call bridge polytopes) which provide a positive Grassmannian analogue of the permutohedron. In this setting, BCFW bridge decompositions of reduced plabic graphs play the role of reduced decompositions. We define Br(k,...

  11. Insulin, insulin analogues and diabetic retinopathy.

    Science.gov (United States)

    Chantelau, Ernst; Kimmerle, Renate; Meyer-Schwickerath, Rolf

    2008-02-01

    Insulin is absolutely vital for living beings. It is not only involved in metabolism, but also in the regulation of growth factors, e.g. IGF-1. In this review we address the role insulin has in the natural evolution of diabetic retinopathy. On the one hand, chronic deficiency of insulin and IGF-1 at the retina is thought to cause capillary degeneration, with subsequent ischaemia. On the other hand, acute abundance of (exogenously administered) insulin and IGF-1 enhances ischaemia-induced VEGF expression. A critical ratio of tissue VEGF-susceptibility: VEGF-availability triggers vascular proliferation (i.e. of micro-aneurysms and/or abnormal vessels). The patent-protected insulin analogues Lispro, Glulisine, Aspart, Glargine and Detemir are artificial insulin derivatives with altered biological responses compared to natural insulin (e.g. divergent insulin and /or IGF-1 receptor-binding characteristics, signalling patterns, and mitogenicity). Their safety profiles concerning diabetic retinopathy remain to be established by randomised controlled trials. Anecdotal reports and circumstantial evidence suggest that Lispro and Glargine might worsen diabetic retinopathy.

  12. Developing Skin Analogues for a Robotic Octopus

    Institute of Scientific and Technical Information of China (English)

    Jinping Hou; Richard H.C.Bonser; George Jeronimidis

    2012-01-01

    In order to fabricate a biomimetic skin for an octopus inspired robot,a new process was developed based on mechanical properties measured from real octopus skin.Various knitted nylon textiles were tested and the one of 10-denier nylon was chosen as reinforcement.A combination of Ecoflex 0030 and 0010 silicone rubbers was used as matrix of the composite to obtain the right stiffness for the skin-analogue system.The open mould fabrication process developed allows air bubble to escape easily and the artificial skin produced was thin and waterproof.Material properties of the biomimetic skin were characterised using static tensile and instrumented scissors cutting tests.The Young's moduli of the artificial skin are 0.08 MPa and 0.13 MPa in the longitudinal and transverse directions,which are much lower than those of the octopus skin.The strength and fracture toughness of the artificial skin,on the other hand are higher than those of real octopus skins.Conically-shaped skin prototypes to be used to cover the robotic arm unit were manufactured and tested.The biomimetic skin prototype was stiff enough to maintain it conical shape when filled with water.The driving force for elongation was reduced significantly compared with previous prototypes.

  13. Multiple alternative substrate kinetics.

    Science.gov (United States)

    Anderson, Vernon E

    2015-11-01

    The specificity of enzymes for their respective substrates has been a focal point of enzyme kinetics since the initial characterization of metabolic chemistry. Various processes to quantify an enzyme's specificity using kinetics have been utilized over the decades. Fersht's definition of the ratio kcat/Km for two different substrates as the "specificity constant" (ref [7]), based on the premise that the important specificity existed when the substrates were competing in the same reaction, has become a consensus standard for enzymes obeying Michaelis-Menten kinetics. The expansion of the theory for the determination of the relative specificity constants for a very large number of competing substrates, e.g. those present in a combinatorial library, in a single reaction mixture has been developed in this contribution. The ratio of kcat/Km for isotopologs has also become a standard in mechanistic enzymology where kinetic isotope effects have been measured by the development of internal competition experiments with extreme precision. This contribution extends the theory of kinetic isotope effects to internal competition between three isotopologs present at non-tracer concentrations in the same reaction mix. This article is part of a special issue titled: Enzyme Transition States from Theory and Experiment.

  14. A q-Analogue of the Dirichlet L-Function

    Institute of Scientific and Technical Information of China (English)

    Min-Soo Kim; Jin-Woo Son

    2002-01-01

    In this paper, we will treat some interesting formulae which are slightly different from Kim's results by more or less the same method in [4-9]. At first, we consider a new definition of a q-analogue of Bernoulli numbers and polynomials.We construct a q-analogue of the Riemann ζ-function, Hurwitz ζ-function, and Dirichlet L-series. Also, we investigate the relation between the q-analogue of generalized Bernoulli numbers and the generalized Euler numbers. As an application, we prove that the q-analogue of Bernoulli numbers occurs in the coefficients of some Stirling type series for the p-adic analytic q-log-gamma function.

  15. Current prodrug strategies for improving oral absorption of nucleoside analogues

    Directory of Open Access Journals (Sweden)

    Youxi Zhang

    2014-04-01

    Full Text Available Nucleoside analogues are first line chemotherapy in various severe diseases: AIDS (acquired immunodeficiency disease syndrome, cytomegalovirus infections, cancer, etc. However, many nucleoside analogues exhibit poor oral bioavailability because of their high polarity and low intestinal permeability. In order to get around this drawback, prodrugs have been utilized to improve lipophilicity by chemical modification of the parent drug. Alternatively, prodrugs targeting transporters present in the intestine have been applied to promote the transport of the nucleoside analogues. Valacyclovir and valganciclovir are two classic valine ester prodrugs transported by oligopeptide transporter 1. The ideal prodrug achieves delivery of a parent drug by attaching a non-toxic moiety that is stable during transport, but is readily degraded to the parent drug once at the target. This article presents advances of prodrug approaches for enhancing oral absorption of nucleoside analogues.

  16. Insulin analogues in pregnancy and specific congenital anomalies

    DEFF Research Database (Denmark)

    de Jong, Josta; Garne, Ester; Wender-Ozegowska, Ewa

    2016-01-01

    in the congenital anomaly rate among foetuses exposed to insulin analogues (lispro, aspart, glargine or detemir) compared with those exposed to human insulin or Neutral Protamine Hagedorn insulin. The total prevalence of congenital anomalies was not increased for foetuses exposed to insulin analogues. The small...... included 1286 foetuses of mothers using short-acting insulin analogues with 1089 references of mothers using human insulin and 768 foetuses of mothers using long-acting insulin analogues with 685 references of mothers using long-acting human insulin (Neutral Protamine Hagedorn). The congenital anomaly rate...... samples in the included studies provided insufficient statistical power to identify a moderate increased risk of specific congenital anomalies. Copyright © 2015 John Wiley & Sons, Ltd....

  17. Synthesis of Novel Isoxazole-contained Analogues of Losartan

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A series of novel isoxazole-contained analogues of Losartan were designed and synthesized with 1,3-DC reaction. The regioselectivity of the reaction was discussed and the compounds are potential antihypertensive.

  18. Solistatinol, a novel phenolic compactin analogue from Penicillium solitum

    DEFF Research Database (Denmark)

    Larsen, Thomas Ostenfeld; Lange, Lene; Schnorr, Kirk

    2007-01-01

    Solistatinol, a novel phenolic compactin analogue, has been isolated from Penicillium solitum using a UV-guided strategy. The structure and relative stereochemistry were determined by NMR spectroscopy and mass spectrometry. The absolute stereochemistry was determined by chemical degradation...

  19. Sulphur Spring: Busy Intersection and Possible Martian Analogue

    Science.gov (United States)

    Nankivell, A.; Andre, N.; Thomas-Keprta, K.; Allen, C.; McKay, D.

    2000-01-01

    Life in extreme environments exhibiting conditions similar to early Earth and Mars, such as Sulphur Spring, may harbor microbiota serving as both relics from the past as well as present day Martian analogues.

  20. Automated Layout Generation of Analogue and Mixed-Signal ASIC's

    DEFF Research Database (Denmark)

    Bloch, Rene

    The research and development carried out in this Ph.D. study focusses on two key areas of the design flow for analogue and mixed-signal integrated circuit design, the mixed-signal floorplanning and the analogue layout generation.A novel approach to floorplanning is presented which provides true...... flow.A new design flow for automated layout generation of general analogue integrated circuits is presented. The design flow provides an automated design path from a sized circuit schematic to the final layout containing the placed, but unrouted, devices of the circuit. The analogue circuit layout...... interactive floorplanning capabilities due to a new implementation variant of a Genetic Algorithm. True interactive floorplanning allows the designer to communicate with existing floorplans during optimization. By entering the "ideas" and expertise of the designer into the optimization algorithm the automated...

  1. Analogue and Mixed-Signal Integrated Circuits for Space Applications

    CERN Document Server

    2014-01-01

    The purpose of AMICSA 2014 (organised in collaboration of ESA and CERN) is to provide an international forum for the presentation and discussion of recent advances in analogue and mixed-signal VLSI design techniques and technologies for space applications.

  2. Analogue gravitational phenomena in Bose-Einstein condensates

    CERN Document Server

    Finazzi, Stefano

    2012-01-01

    Analogue gravity is based on the simple observation that perturbations propagating in several physical systems can be described by a quantum field theory in a curved spacetime. While phenomena like Hawking radiation are hardly detectable in astrophysical black holes, these effects may be experimentally tested in analogue systems. In this Thesis, focusing on Bose-Einstein condensates, we present our recent results about analogue models of gravity from three main perspectives: as laboratory tests of quantum field theory in curved spacetime, for the techniques that they provide to address various issues in general relativity, and as toy models of quantum gravity. The robustness of Hawking-like particle creation is investigated in flows with a single black hole horizon. Furthermore, we find that condensates with two (white and black) horizons develop a dynamical instability known in general relativity as black hole laser effect. Using techniques borrowed from analogue gravity, we also show that warp drives, which...

  3. Doing it with Mirrors Classical analogues for Black Hole radiation

    CERN Document Server

    Srinivasan, K

    1998-01-01

    We construct analogues for the quantum phenomena of black hole radiation in the context of {\\it classical field theory}. Hawking radiation from a (radially) collapsing star is mathematically equivalent to radiation from a mirror moving along a specific trajectory in Minkowski spacetime. We construct a classical analogue for this quantum phenomenon and use it to construct a classical analogue for black hole radiation. The radiation spectrum in quantum field theory has the power spectrum as its classical analogue. Monochromatic light is continually reflected off a moving mirror or the silvered surface of a collapsing star.The reflected light is fourier analysed by the observer and the power spectrum is constructed. For a mirror moving along the standard black hole trajectory,it is seen that the power spectrum has a ``thermal'' nature. Mirror-observer configurations like an inertial mirror observed in an accelerated observer's frame and an accelerated mirror observed in a Rindler frame are investigated and condi...

  4. From BPA to its analogues: Is it a safe journey?

    Science.gov (United States)

    Usman, Afia; Ahmad, Masood

    2016-09-01

    Bisphenol-A (BPA) is one of the most abundant synthetic chemicals in the world due to its uses in plastics. Its widespread exposure vis-a-vis low dose effects led to a reduction in its safety dose and imposition of ban on its use in infant feeding bottles. This restriction paved the way for the gradual market entry of its analogues. However, their structural similarity to BPA has put them under surveillance for endocrine disrupting potential. The application of these analogues is increasing and so are the studies reporting their toxicity. This review highlights the reasons which led to the ban of BPA and also reports the exposure and toxicological data available on its analogues. Hence, this compilation is expected to answer in a better way whether the replacement of BPA by these analogues is safer or more harmful?

  5. Cell-cycle analyses using thymidine analogues in fission yeast.

    Directory of Open Access Journals (Sweden)

    Silje Anda

    Full Text Available Thymidine analogues are powerful tools when studying DNA synthesis including DNA replication, repair and recombination. However, these analogues have been reported to have severe effects on cell-cycle progression and growth, the very processes being investigated in most of these studies. Here, we have analyzed the effects of 5-ethynyl-2'-deoxyuridine (EdU and 5-Chloro-2'-deoxyuridine (CldU using fission yeast cells and optimized the labelling procedure. We find that both analogues affect the cell cycle, but that the effects can be mitigated by using the appropriate analogue, short pulses of labelling and low concentrations. In addition, we report sequential labelling of two consecutive S phases using EdU and 5-bromo-2'-deoxyuridine (BrdU. Furthermore, we show that detection of replicative DNA synthesis is much more sensitive than DNA-measurements by flow cytometry.

  6. Cell-cycle analyses using thymidine analogues in fission yeast.

    Science.gov (United States)

    Anda, Silje; Boye, Erik; Grallert, Beata

    2014-01-01

    Thymidine analogues are powerful tools when studying DNA synthesis including DNA replication, repair and recombination. However, these analogues have been reported to have severe effects on cell-cycle progression and growth, the very processes being investigated in most of these studies. Here, we have analyzed the effects of 5-ethynyl-2'-deoxyuridine (EdU) and 5-Chloro-2'-deoxyuridine (CldU) using fission yeast cells and optimized the labelling procedure. We find that both analogues affect the cell cycle, but that the effects can be mitigated by using the appropriate analogue, short pulses of labelling and low concentrations. In addition, we report sequential labelling of two consecutive S phases using EdU and 5-bromo-2'-deoxyuridine (BrdU). Furthermore, we show that detection of replicative DNA synthesis is much more sensitive than DNA-measurements by flow cytometry.

  7. Review of the recent progress in photoresponsive molecularly imprinted polymers containing azobenzene chromophores.

    Science.gov (United States)

    Wei, Yu-bo; Tang, Qian; Gong, Cheng-bin; Lam, Michael Hon-Wah

    2015-11-05

    Photoresponsive molecularly imprinted polymers (PMIPs) containing azobenzene have received wide research attention in recent years and made notable achievements. This article reviews the recent developments on PMIPs containing azobenzene. Topics include the following: (i) brief introduction of azobenzene, molecularly imprinted polymers, and PMIPs containing azobenzene; (ii) progress in functional monomers, cross-linkers, and polymerization conditions; (iii) preparation methods, properties, applications, as well as advantages and disadvantages of conventional PMIPs; (iv) substrate, preparation method, and applications of photoresponsive surface molecularly imprinted polymers; and (v) some perspectives for further development of PMIPs containing azobenzene.

  8. A new antiproliferative noscapine analogue: chemical synthesis and biological evaluation

    OpenAIRE

    Ghaly, Peter E.; Abou El-Magd, Rabab M.; Churchill, Cassandra D. M.; Tuszynski, Jack A.; West, F. G.

    2016-01-01

    Noscapine, a naturally occurring opium alkaloid, is a widely used antitussive medication. Noscapine has low toxicity and recently it was also found to possess cytotoxic activity which led to the development of many noscapine analogues. In this paper we report on the synthesis and testing of a novel noscapine analogue. Cytotoxicity was assessed by MTT colorimetric assay using SKBR-3 and paclitaxel-resistant SKBR-3 breast cancer cell lines using different concentrations for both noscapine and t...

  9. Analogue and digital linear modulation techniques for mobile satellite

    Science.gov (United States)

    Whitmarsh, W. J.; Bateman, A.; Mcgeehan, J. P.

    1990-01-01

    The choice of modulation format for a mobile satellite service is complex. The subjective performance is summarized of candidate schemes and voice coder technologies. It is shown that good performance can be achieved with both analogue and digital voice systems, although the analogue system gives superior performance in fading. The results highlight the need for flexibility in the choice of signaling format. Linear transceiver technology capable of using many forms of narrowband modulation is described.

  10. An azumamide C analogue without the zinc-binding functionality

    DEFF Research Database (Denmark)

    Villadsen, Jesper; Kitir, Betül; Wich, Kathrine;

    2014-01-01

    + - coordinating moiety. Herein, we describe the synthesis of an azumamide analogue lacking its native Zn 2+ -binding group and evaluation of its inhibitory activity against recombinant human HDAC1 – 11. Furthermore, kinetic investigation of the inhibitory mechanism of both parent natural product and synthetic...... analogue against HDAC3-NCoR2 is reported as well as their activity against Burkitt's lymphoma cell proliferation....

  11. Adjuvant properties of a simplified C32 monomycolyl glycerol analogue.

    Science.gov (United States)

    Bhowruth, Veemal; Minnikin, David E; Agger, Else Marie; Andersen, Peter; Bramwell, Vincent W; Perrie, Yvonne; Besra, Gurdyal S

    2009-04-01

    A simplified C(32) monomycolyl glycerol (MMG) analogue demonstrated enhanced immunostimulatory activity in a dioctadecyl ammonium bromide (DDA)/Ag85B-ESAT-6 formulation. Elevated levels of IFN-gamma and IL-6 were produced in spleen cells from mice immunised with a C(32) MMG analogue comparable activity to the potent Th1 adjuvant, trehalose 6,6'-di-behenate (TDB).

  12. Analogue Signal Processing: Collected Papers 1994-95

    DEFF Research Database (Denmark)

    1996-01-01

    This document is a collection of the papers presented at international conferences and in international journals by the analogue signal processing group of Electronics Institute, Technical University of Denmark, in 1994 and 1995.......This document is a collection of the papers presented at international conferences and in international journals by the analogue signal processing group of Electronics Institute, Technical University of Denmark, in 1994 and 1995....

  13. Analogue Signal Processing: Collected Papers 1996-97

    DEFF Research Database (Denmark)

    1997-01-01

    This document is a collection of the papers presented at international conferences and in international journals by the analogue signal processing group of the Department of Information Technology, Technical University of Denmark, in 1996 and 1997.......This document is a collection of the papers presented at international conferences and in international journals by the analogue signal processing group of the Department of Information Technology, Technical University of Denmark, in 1996 and 1997....

  14. Semisynthesis of salviandulin E analogues and their antitrypanosomal activity.

    Science.gov (United States)

    Aoyagi, Yutaka; Fujiwara, Koji; Yamazaki, Akira; Sugawara, Naoko; Yano, Reiko; Fukaya, Haruhiko; Hitotsuyanagi, Yukio; Takeya, Koichi; Ishiyama, Aki; Iwatsuki, Masato; Otoguro, Kazuhiko; Yamada, Haruki; Ōmura, Satoshi

    2014-01-15

    A series of analogues of salviandulin E, a rearranged neoclerodane diterpene originally isolated from Salvia leucantha (Lamiaceae), were prepared and their in vitro activity against Trypanosoma brucei brucei was evaluated with currently used therapeutic drugs as positive controls. One of the 19 compounds prepared and assayed in the present study, butanoyl 3,4-dihydrosalviandulin E analogue was found to be a possible candidate for an antitrypanosomal drug with fairly strong antitrypanosomal activity and lower cytotoxicity.

  15. Phosphorescence parameters for platinum (II) organometallic chromophores: A study at the non-collinear four-component Kohn–Sham level of theory

    DEFF Research Database (Denmark)

    Norman, Patrick; Jensen, Hans Jørgen Aagaard

    2012-01-01

    A theoretical characterization of the phosphorescence decay traces of a prototypical platinum (II) organic chromophore has been conducted. The phosphorescence wavelength and radiative lifetime are predicted to equal 544 nm and 160 μs, respectively. The third triplet state is assigned as participa...

  16. Ferrocene-quinoxaline Y-shaped chromophores as fascinating second-order NLO building blocks for long lasting highly active SHG polymeric films.

    Science.gov (United States)

    Senthilkumar, Kabali; Thirumoorthy, Krishnan; Dragonetti, Claudia; Marinotto, Daniele; Righetto, Stefania; Colombo, Alessia; Haukka, Matti; Palanisami, Nallasamy

    2016-07-26

    The first example of a Y-shaped ferrocene quinoxaline derivative with a surprisingly high and stable second harmonic generation (SHG) response in composite polymeric films is reported. The interesting quadratic hyperpolarizability values of different substituted Y-shaped chromophores are also investigated in solution by the EFISH technique.

  17. New sugar-based gelators bearing a p-nitrophenyl chromophore: remarkably large influence of a sugar structure on the gelation ability

    NARCIS (Netherlands)

    Amanokura, Natsuki; Yoza, Kenji; Shinmori, Hideyuki; Shinkai, Seiji; Reinhoudt, David N.

    1998-01-01

    Three sugar-integrated gelators bearing a p-nitrophenyl group as a chromophore were synthesised. D-Mannose-based compound 3 was too soluble in most organic solvents to act as a gelator whereas D-galactose-based compound 2 was sparingly soluble in most organic solvents. D-Glucose-based compound 1 was

  18. Theoretical Studies on the First Hyperpolarizabilities of One-dimensional Donor-bridge-acceptor Chromophores and New Applications of BLA in Determining Molecular First Hyperpolarizabilities

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    We present a quantum-chemical analysis of the relationship between the bond length alteration (BLA) and the static first hyperpolarizability of a series of one-dimensional (ID)chromophores with donor-bridge-acceptor (D-B-A) structures.The calculated results show that the parameter BLA can be considered as an indicator to evaluate the molecular first hyper-polarizability.Along the direction of molecular ground-state dipole moments, the evolutions of BLA can be classified into three categories: the first is a non-monotonic line, which represents most chromophores; the second is monotonic increasing; and the third, contrarily, is monotonic decreasing.On the whole, the first hyperpolarizabilities of these studied chromophores are the mortotonic functions of BLA along the direction of dipole moments.Therefore, the first hyper-polarizability of these 1D chromophores can be preliminarily evaluated in terms of the deve-lopment of BLA without a rigorous computation.In other words, one can roughly estimate the relative magnitude of the first hyperpolarizability according to the optimized geometry.

  19. Extension of Light-Harvesting Ability of Photosynthetic Light-Harvesting Complex 2 (LH2) through Ultrafast Energy Transfer from Covalently Attached Artificial Chromophores.

    Science.gov (United States)

    Yoneda, Yusuke; Noji, Tomoyasu; Katayama, Tetsuro; Mizutani, Naoto; Komori, Daisuke; Nango, Mamoru; Miyasaka, Hiroshi; Itoh, Shigeru; Nagasawa, Yutaka; Dewa, Takehisa

    2015-10-14

    Introducing appropriate artificial components into natural biological systems could enrich the original functionality. To expand the available wavelength range of photosynthetic bacterial light-harvesting complex 2 (LH2 from Rhodopseudomonas acidophila 10050), artificial fluorescent dye (Alexa Fluor 647: A647) was covalently attached to N- and C-terminal Lys residues in LH2 α-polypeptides with a molar ratio of A647/LH2 ≃ 9/1. Fluorescence and transient absorption spectroscopies revealed that intracomplex energy transfer from A647 to intrinsic chromophores of LH2 (B850) occurs in a multiexponential manner, with time constants varying from 440 fs to 23 ps through direct and B800-mediated indirect pathways. Kinetic analyses suggested that B800 chromophores mediate faster energy transfer, and the mechanism was interpretable in terms of Förster theory. This study demonstrates that a simple attachment of external chromophores with a flexible linkage can enhance the light harvesting activity of LH2 without affecting inherent functions of energy transfer, and can achieve energy transfer in the subpicosecond range. Addition of external chromophores, thus, represents a useful methodology for construction of advanced hybrid light-harvesting systems that afford solar energy in the broad spectrum.

  20. UV-Vis spectroscopy of tyrosine side-groups in studies of protein structure. Part 1: basic principles and properties of tyrosine chromophore.

    Science.gov (United States)

    Antosiewicz, Jan M; Shugar, David

    Spectroscopic properties of tyrosine residues may be employed in structural studies of proteins. Here we discuss several different types of UV-Vis spectroscopy, like normal, difference and second-derivative UV absorption spectroscopy, fluorescence spectroscopy, linear and circular dichroism spectroscopy, and Raman spectroscopy, and corresponding optical properties of the tyrosine chromophore, phenol, which are used to study protein structure.

  1. The relevance of analogue studies for understanding obsessions and compulsions.

    Science.gov (United States)

    Abramowitz, Jonathan S; Fabricant, Laura E; Taylor, Steven; Deacon, Brett J; McKay, Dean; Storch, Eric A

    2014-04-01

    Analogue samples are often used to study obsessive-compulsive (OC) symptoms and related phenomena. This approach is based on the hypothesis that results derived from such samples are relevant to understanding OC symptoms in individuals with a diagnosis of obsessive-compulsive disorder (OCD). Two decades ago, Gibbs (1996) reviewed the available literature and found initial support for this hypothesis. Since then there have been many important advances addressing this issue. The purpose of the present review was to synthesize various lines of research examining the assumptions of using analogue samples to draw inferences about people with OCD. We reviewed research on the prevalence of OC symptoms in non-clinical populations, the dimensional (vs. categorical) nature of these symptoms, phenomenology, etiology, and studies on developmental and maintenance factors in clinical and analogue samples. We also considered the relevance of analogue samples in OCD treatment research. The available evidence suggests research with analogue samples is highly relevant for understanding OC symptoms. Guidelines for the appropriate use of analogue designs and samples are suggested.

  2. Cladribine Analogues via O6-(Benzotriazolyl Derivatives of Guanine Nucleosides

    Directory of Open Access Journals (Sweden)

    Sakilam Satishkumar

    2015-10-01

    Full Text Available Cladribine, 2-chloro-2′-deoxyadenosine, is a highly efficacious, clinically used nucleoside for the treatment of hairy cell leukemia. It is also being evaluated against other lymphoid malignancies and has been a molecule of interest for well over half a century. In continuation of our interest in the amide bond-activation in purine nucleosides via the use of (benzotriazol-1yl-oxytris(dimethylaminophosphonium hexafluorophosphate, we have evaluated the use of O6-(benzotriazol-1-yl-2′-deoxyguanosine as a potential precursor to cladribine and its analogues. These compounds, after appropriate deprotection, were assessed for their biological activities, and the data are presented herein. Against hairy cell leukemia (HCL, T-cell lymphoma (TCL and chronic lymphocytic leukemia (CLL, cladribine was the most active against all. The bromo analogue of cladribine showed comparable activity to the ribose analogue of cladribine against HCL, but was more active against TCL and CLL. The bromo ribose analogue of cladribine showed activity, but was the least active among the C6-NH2-containing compounds. Substitution with alkyl groups at the exocyclic amino group appears detrimental to activity, and only the C6 piperidinyl cladribine analogue demonstrated any activity. Against adenocarcinoma MDA-MB-231 cells, cladribine and its ribose analogue were most active.

  3. A New Class of Organic Luminophores With a stilbene Chromophore: 3-Phenylmethylene-1(3-H) Isobenzofuranones

    Science.gov (United States)

    Nikolov, Peter; Fratev, Filip; Minchev, Stoyan

    1983-02-01

    A new class of luminophores with a stilbene chromophore, 3-phenylmethylene-1(3H)-iso-benzofuranones (BPH's), has been investigated. The fluorescence occurs in the region 26000-16000 cm-1, the maximal quantum yield being about 0.6. As a result of substitution or higher polarity of the solvent the ππ* state of the BPH's separates from the fluorescently inactive nπ* state. The S0-S2 absorption transition of the BPH's results from an excitation which is practically localized in the stilbene fragment. The good linear correlation of the fluorescence and absorption maxima and O-O transitions in ethanol with the σp-Hammett constants has been used for an interpretation of the changes in the potential hyperfaces of S0 and S1 states.

  4. Experimental tests of the correlated chromophore domain model of self-healing in a dye-doped polymer

    CERN Document Server

    Ramini, Shiva K; Kuzyk, Mark G

    2013-01-01

    Temperature dependent photodegradation and recovery studies of Dipserse Orange 11 (DO11) dye dissolved in poly(methyl methacrylate) and polystyrene polymer hosts are used as a test of the recently proposed correlated chromophore domain model.[1] This model posits that dye molecules form domains or aggregates. The nature of aggregation or how it mediates self healing is not yet well understood. In this paper we present qualitative evidence that supports the hypothesis that the dye molecules undergo a change to a tautomer state with higher dipole moment and hydrogen bond with the amines and keto oxygens of the polymer. Groupings of such molecules in a polymer chain form what we call a domain, and interactions between molecules in a domain make them more robust to photodegradation and mediate self healing.

  5. Theoretical Investigation on the Electron and Energy Transfer between Peripheral Carrier Transport Groups and Central Chromophores in Electroluminescent Materials

    Institute of Scientific and Technical Information of China (English)

    潘玉钰; 刘丹丹; 许海; 刘晓冬; 孙冠楠; 杨兵; 马於光

    2012-01-01

    The molecular materials with structures of luminescent core and peripheral carrier groups (e.g. carbazoles), have exhibited high-performance in organic light-emitting diodes (OLEDs). Present work is to understand the basic process of electronic and energy exchange between the peripheral functional groups and the central core through quantum chemical analysis. As an example, 4,7-bis(9,9-bis(6-(9H-carbazol-9-yl)hexyl)-9H-fluoren-2-yl)benzo[c]- [1,2,5]thiadiazole (TCBzC) is investigated in regards to optoelectronic properties using density functional theory (DFT). The results suggest that the forbidden transition from peripheral carbazole to the central chromophore core makes for separated electrical and optical properties, and high performance electroluminescence (EL) is mainly at- tributed to the energy-transfer from carbazoles to the fluorene derivative core.

  6. Recent Advances in Stimuli-Responsive Photofunctional Materials Based on Accommodation of Chromophore into Layered Double Hydroxide Nanogallery

    Directory of Open Access Journals (Sweden)

    Wu Li

    2013-01-01

    Full Text Available The assembly of photofunctional molecules into host matrices has become an important strategy to achieve tunable fluorescence and to develop intelligent materials. The stimuli-responsive photofunctional materials based on chromophores-assembled layered double hydroxides (LDHs have received much attention from both academic and industry fields as a result of their advantages, such as high photo/thermal stability, easy processing, and well reversibility, which can construct new types of smart luminescent nanomaterials (e.g., ultrathin film and nanocomposite for sensor and switch applications. In this paper, external environmental stimuli have mainly involved physical (such as temperature, pressure, light, and electricity and chemical factors (such as pH and metal ion; recent progress on the LDH-based organic-inorganic stimuli-responsive materials has been summarized. Moreover, perspectives on further development of these materials are also discussed.

  7. LanFP10-A, first functional fluorescent protein whose chromophore contains the elusive mutation G67A.

    Science.gov (United States)

    Roldán-Salgado, Abigail; Sánchez-Barreto, Celidee; Gaytán, Paul

    2016-11-01

    Since Green Fluorescent Protein (GFP) was first successfully expressed in heterologous systems in 1994, many genes encoding other natural autofluorescent proteins (AFPs) have been cloned and subsequently modified by protein engineering to improve their physicochemical properties. Throughout this twenty-two-year period, glycine 67 (Gly67) has been regarded as the only amino acid in the entire protein family that is essential for the formation of the different reported chromophores. In this work, we demonstrate that a synthetic gene encoding LanFP10-A, a natural protein encoded in the genome of the lancelet Branchiostoma floridae containing the G67A mutation, produces a heterologous, functional yellow fluorescent protein when expressed in E. coli. In contrast to LanFP10-A, LanFP6-A, a second GFP-like protein found in the lancelet genome that also contains the natural G67A mutation, was non-fluorescent.

  8. Ultrafast dual photoresponse of isolated biological chromophores: link to the photoinduced mode-specific non-adiabatic dynamics in proteins

    DEFF Research Database (Denmark)

    Bochenkova, Anastasia; Andersen, Lars Henrik

    2013-01-01

    channels. Deactivation includes vibrational resonant photodetachment and internal conversion. Here, we provide a detailed insight in the efficiency of different vibrational modes in promoting a selective photoresponse in the bare GFP chromophore anion. We introduce a general theoretical model...... that is capable to account for the alternative non-equivalent pathways in internal conversion, and we outline the factors, by which the photo-initiated response may be altered in this channel. The topography around the planar minimum in S1 and the two distinct types of the S1/S0 conical intersections obtained...... the ultrafast non-statistical electron emission coupled with vibrational (de)coherence, whereas a vibrational pre-excitation in the ground state may lead to the ultrafast non-statistical internal conversion through a conical intersection. We also discuss the implication of our results to the photo-initiated non...

  9. Synthesis of Bidimensional Prussian Blue Analogue Using an Inverted Langmuir-Schaefer Method.

    Science.gov (United States)

    Rossos, Andreas K; Gengler, Régis Y N; Badali, Daniel S; Miller, R J Dwayne

    2016-09-27

    One of the aspects of modern materials science that has been captivating scientific interest for the past decade is low-dimensional systems. This stems from the fact that the physical, chemical, and biological properties of such systems are often vastly different from their bulk counterparts. Additionally, low-dimensionality structures frequently serve as a convenient platform for device applications. However, such materials are typically constructed from building blocks that are inherently three-dimensional, and so, from a morphological point of view, these can still be categorized as bulk powders or crystals. To push the boundaries of reduced dimensionality, we synthesized truly two-dimensional films of Prussian blue analogues (mixed valence tetracyanides) by combining an air-water interface reaction and a novel inverted Langmuir-Schaefer technique. The methodology introduced in this study offers control and tailoring over the Prussian blue analogues' film characteristics, which is an important step toward their incorporation into tangible applications. Standard isotherms were collected as a function of the initial reactant volume, and a number of characterization techniques such as X-ray photoelectron spectroscopy (XPS), UV-visible spectroscopy (UV-vis), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and atomic force microscopy (AFM) were performed on films transferred on various substrates. The results indicated a collection of single-crystalline and polycrystalline flakes possessing different thicknesses and having a structural coherence length of 11 ± 3 nm.

  10. In vitro and in vivo biocompatibility studies of a recombinant analogue of spidroin 1 scaffolds.

    Science.gov (United States)

    Moisenovich, M M; Pustovalova, O L; Arhipova, A Yu; Vasiljeva, T V; Sokolova, O S; Bogush, V G; Debabov, V G; Sevastianov, V I; Kirpichnikov, M P; Agapov, I I

    2011-01-01

    The goal of this study was to generate porous scaffolds from the genetically engineered protein, an analogue of Nephila clavipes spidroin 1 (rS1/9) and to assess the properties of new rS1/9 scaffolds essential for bioengineering. The salt leaching technique was used to make the rS1/9 scaffolds of interconnected macroporous structure with spontaneously formed micropores. The tensile strength of scaffolds was 18 ± 5 N/cm(2). Scaffolds were relatively stable in a phosphate buffer but degraded in oxidizing environment after 11 weeks of incubation. Applicability of the recombinant spidroin 1 as a substrate for cell culture was demonstrated by successful 3T3 cells growth on the surface of rS1/9 films (270 ± 20 cells/mm(2) vs. 97 ± 8 cells/mm(2) on the glass surface, p 0.05), whereas the initial distribution was 58% ± 7% and 11% ± 8%, respectively; p < 0.05). The rS1/9 scaffolds implanted subcutaneously into Balb/c mice were well tolerated. Over a 2-month period, the scaffolds promoted an ingrowth of de novo formed vascularized connective tissue elements and nerve fibers. Thus, scaffolds made of the novel recombinant spidroin 1 analogue are potentially applicable in tissue engineering.

  11. Novel purine nucleoside analogues for hematological malignancies.

    Science.gov (United States)

    Korycka, Anna; Lech-Marańda, Ewa; Robak, Tadeusz

    2008-06-01

    Recently, the search for more effective and safer antineoplastic agents has led to synthesis and introduction into preclinical and clinical studies of a few new purine nucleoside analogues (PNA). Three of them: clofarabine (CAFdA), nelarabine, and forodesine (immucillin H, BCX-1777), despite belonging to the same group of drugs such as PNA, have shown some differences concerning their active forms, metabolic properties and mechanism of action. However, all these drugs have demonstrated promising activity in patients with relapsed and refractory acute lymphoblastic leukemia (ALL). CAFdA was approved for the therapy of relapsed or refractory ALL in the third line of treatment. It has proved promising in pediatric patients as well as in some patients who are able to proceed to allogenic hematopietic stem cell transplantation (HSCT). Moreover, the drug exhibits an efficacy in acute myeloid leukemia (AML), blast crisis of chronic myelogenous leukemia (CML-BP) and myelodysplastic syndrome (MDS). Nelarabine is recommended for T-ALL and T-cell lymphoblastic lymphoma (T-LBL) with the overall response rates ranging from 11 to 60%. However, the use of the drug is limited by potentially severe neurotoxicity. Forodesine is a purine nucleoside phosphorylase (PNP) inhibitor and it has shown activity in relapsed and refractory T- and B-cells leukemias as well as in cutaneous T-cell lymphoma (CTCL). Recently patented, a few of inventions in the field of pharmaceutical preparation of new PNA have also been published. Great hopes are currently set on the use of these drugs in the treatment of lymphoid and myeloid malignancies in adult and in pediatric patients, however ongoing studies will help to define their role in the standard therapy.

  12. Habitability & Astrobiology Research in Mars Terrestrial Analogues

    Science.gov (United States)

    Foing, Bernard

    2014-05-01

    We performed a series of field research campaigns (ILEWG EuroMoonMars) in the extreme Utah desert relevant to Mars environments, and in order to help in the interpretation of Mars missions measurements from orbit (MEX, MRO) or from the surface (MER, MSL), or Moon geochemistry (SMART-1, LRO). We shall give an update on the sample analysis in the context of habitability and astrobiology. Methods & Results: In the frame of ILEWG EuroMoonMars campaigns (2009 to 2013) we deployed at Mars Desert Research station, near Hanksville Utah, a suite of instruments and techniques [A, 1, 2, 9-11] including sample collection, context imaging from remote to local and microscale, drilling, spectrometers and life sensors. We analyzed how geological and geochemical evolution affected local parameters (mineralogy, organics content, environment variations) and the habitability and signature of organics and biota. Among the important findings are the diversity in the composition of soil samples even when collected in close proximity, the low abundances of detectable PAHs and amino acids and the presence of biota of all three domains of life with significant heterogeneity. An extraordinary variety of putative extremophiles was observed [3,4,9]. A dominant factor seems to be soil porosity and lower clay-sized particle content [6-8]. A protocol was developed for sterile sampling, contamination issues, and the diagnostics of biodiversity via PCR and DGGE analysis in soils and rocks samples [10, 11]. We compare the 2009 campaign results [1-9] to new measurements from 2010-2013 campaigns [10-12] relevant to: comparison between remote sensing and in-situ measurements; the study of minerals; the detection of organics and signs of life. Keywords: field analogue research, astrobiology, habitability, life detection, Earth-Moon-Mars, organics References [A] Foing, Stoker & Ehrenfreund (Editors, 2011) "Astrobiology field Research in Moon/Mars Analogue Environments", Special Issue of International

  13. Protonation state and structural changes of the tetrapyrrole chromophore during the Pr --> Pfr phototransformation of phytochrome: a resonance Raman spectroscopic study.

    Science.gov (United States)

    Kneip, C; Hildebrandt, P; Schlamann, W; Braslavsky, S E; Mark, F; Schaffner, K

    1999-11-16

    The photoconversion of phytochrome (phytochrome A from Avena satina) from the inactive (Pr) to the physiologically active form (Pfr) was studied by near-infrared Fourier transform resonance Raman spectroscopy at cryogenic temperatures, which allow us to trap the intermediate states. Nondeuterated and deuterated buffer solutions were used to determine the effect of H/D exchange on the resonance Raman spectra. For the first time, reliable spectra of the "bleached" intermediates meta-R(A) and meta-R(C) were obtained. The vibrational bands in the region 1300-1700 cm(-)(1), which is particularly indicative of structural changes in tetrapyrroles, were assigned on the basis of recent calculations of the Raman spectra of the chromophore in C-phycocyanin and model compounds [Kneip, C., Hildebrandt, P., Németh, K., Mark, F., Schaffner, K. (1999) Chem. Phys. Lett. 311, 479-485]. The experimental resonance Raman spectra Pr are compatible with the Raman spectra calculated for the protonated ZZZasa configuration, which hence is suggested to be the chromophore structure in this parent state of phytochrome. Furthermore, marker bands could be identified that are of high diagnostic value for monitoring structural changes in individual parts of the chromophore. Specifically, it could be shown that not only in the parent states Pr and Pfr but also in all intermediates the chromophore is protonated at the pyrroleninic nitrogen. The spectral changes observed for lumi-R confirm the view that the photoreaction of Pr is a Z --> E isomerization of the CD methine bridge. The subsequent thermal decay reaction to meta-R(A) includes relaxations of the CD methine bridge double bond, whereas the formation of meta-R(C) is accompanied by structural adaptations of the pyrrole rings B and C in the protein pocket. The far-reaching similarities between the chromophores of meta-R(A) and Pfr suggest that in the step meta-R(A) --> Pfr the ultimate structural changes of the protein matrix occur.

  14. Highly conserved residues Asp-197 and His-250 in Agp1 phytochrome control the proton affinity of the chromophore and Pfr formation.

    Science.gov (United States)

    von Stetten, David; Seibeck, Sven; Michael, Norbert; Scheerer, Patrick; Mroginski, Maria Andrea; Murgida, Daniel H; Krauss, Norbert; Heyn, Maarten P; Hildebrandt, Peter; Borucki, Berthold; Lamparter, Tilman

    2007-01-19

    The mutants H250A and D197A of Agp1 phytochrome from Agrobacterium tumefaciens were prepared and investigated by different spectroscopic and biochemical methods. Asp-197 and His-250 are highly conserved amino acids and are part of the hydrogen-bonding network that involves the chromophore. Both substitutions cause a destabilization of the protonated chromophore in the Pr state as revealed by resonance Raman and UV-visible absorption spectroscopy. Titration experiments demonstrate a lowering of the pK(a) from 11.1 (wild type) to 8.8 in H250A and 7.2 in D197A. Photoconversion of the mutants does not lead to the Pfr state. H250A is arrested in a meta-Rc-like state in which the chromophore is deprotonated. For H250A and the wild-type protein, deprotonation of the chromophore in meta-Rc is coupled to the release of a proton to the external medium, whereas the subsequent proton re-uptake, linked to the formation of the Pfr state in the wild-type protein, is not observed for H250A. No transient proton exchange with the external medium occurs in D197A, suggesting that Asp-197 may be the proton release group. Both mutants do not undergo the photo-induced protein structural changes that in the wild-type protein are detectable by size exclusion chromatography. These conformational changes are, therefore, attributed to the meta-Rc --> Pfr transition and most likely coupled to the transient proton re-uptake. The present results demonstrate that Asp-197 and His-250 are essential for stabilizing the protonated chromophore structure in the parent Pr state, which is required for the primary photochemical process, and for the complete photo-induced conversion to the Pfr state.

  15. Incorporation of tryptophan analogues into the lantibiotic nisin.

    Science.gov (United States)

    Zhou, Liang; Shao, Jinfeng; Li, Qian; van Heel, Auke J; de Vries, Marcel P; Broos, Jaap; Kuipers, Oscar P

    2016-05-01

    Lantibiotics are posttranslationally modified peptides with efficient inhibitory activity against various Gram-positive bacteria. In addition to the original modifications, incorporation of non-canonical amino acids can render new properties and functions to lantibiotics. Nisin is the most studied lantibiotic and contains no tryptophan residues. In this study, a system was constructed to incorporate tryptophan analogues into nisin, which included the modification machinery (NisBTC) and the overexpression of tryptophanyl-tRNA synthetase (TrpRS). Tryptophan and three different tryptophan analogues (5-fluoroTrp (5FW), 5-hydroxyTrp (5HW) and 5-methylTrp (5MeW)) were successfully incorporated at four different positions of nisin (I1W, I4W, M17W and V32W). The incorporation efficiency of tryptophan analogues into mutants I1W, M17W and V32W was over 97 %, while the mutant I4W showed relatively low incorporation efficiency (69-93 %). The variants with 5FW showed relatively higher production yield, while 5MeW-containing variants showed the lowest yield. The dehydration efficiency of serines or threonines was affected by the tryptophan mutants of I4W and V32W. The affinity of the peptides for the cation-ion exchange and reverse phase chromatography columns was significantly reduced when 5HW was incorporated. The antimicrobial activity of IIW and its 5FW analogue both decreased two times compared to that of nisin, while that of its 5HW analogue decreased four times. The 5FW analogue of I4W also showed two times decreased activity than nisin. However, the mutant M17W and its 5HW analogue both showed 32 times reduced activity relative to that of nisin.

  16. Insulin analogues and cancer: a note of caution

    Directory of Open Access Journals (Sweden)

    Joseph A.M.J.L. eJanssen

    2014-05-01

    Full Text Available Abstract In view of the lifelong exposure and large patient populations involved, insulin analogues with an increased mitogenic effect in comparison to human insulin may potentially constitute a major health problem, since these analogues may possibly induce the growth of pre-existing neoplasms. At present, the available data suggest that insulin analogues are safe. In line with these findings, we observed that serum of diabetic patients treated with insulin analogues, compared to that of diabetic patients treated with human insulin, did not induce an increased phosphorylation of tyrosine residues of the insulin-like growth factor-I receptor (IGF-IR. However, the classical model of the IGF-IR signaling may be insufficient to explain (all mitogenic effects of insulin analogues since also non-canonical signaling pathways of the IGF-IR may play a major role in this respect. Although phosphorylation of tyrosine residues of the IGF-IR is generally considered to be the initial activation step within the intracellular IGF-IR signaling pathway, it has been found that cells undergo a signaling switch under hyperglycemic conditions. After this switch, a completely different mechanism is utilized to activate the mitogenic (mitogen-activated protein kinase (MAPK pathways of the IGF-IR that is independent from tyrosine phosphorylation of the IGF-IR. At present it is unknown whether activation of this alternative intracellular pathway of the IGF-IR occurs during hyperglycemia in vivo and whether it is stronger in patients treated with (some insulin analogues than in patients treated with human insulin. In addition, it is unknown whether the insulin receptors (IRs also undergo a signaling switch during hyperglycemia. This should be investigated in future studies. Finally, relative overexpression of IR isoform A (IR-A in (pre cancer tissues may play a key role in the development and progression of human cancers during treatment with insulin (analogues. Further

  17. Dihydrobenzofuran analogues of hallucinogens. 4. Mescaline derivatives.

    Science.gov (United States)

    Monte, A P; Waldman, S R; Marona-Lewicka, D; Wainscott, D B; Nelson, D L; Sanders-Bush, E; Nichols, D E

    1997-09-12

    hallucinogens, that such compounds must be full agonists at the 5-HT2A receptor subtype. In contrast to the 2,5-dimethoxy-substituted phenethylamines, where rigidification of the methoxy groups had no deleterious effect on activity, the loss of activity in the 3,4,5-trioxygenated mescaline analogues may suggest that the 3 and 5 methoxy groups must remain conformationally mobile to enable receptor activation.

  18. Iron isotopes in an Archean ocean analogue

    Science.gov (United States)

    Busigny, Vincent; Planavsky, Noah J.; Jézéquel, Didier; Crowe, Sean; Louvat, Pascale; Moureau, Julien; Viollier, Eric; Lyons, Timothy W.

    2014-05-01

    Iron isotopes have been extensively used to trace the history of microbial metabolisms and the redox evolution of the oceans. Archean sedimentary rocks display greater variability in iron isotope ratios and more markedly negative values than those deposited in the Proterozoic and Phanerozoic. This increased variability has been linked to changes in either water column iron cycling or the extent of benthic microbial iron reduction through time. We tested these contrasting scenarios through a detailed study of anoxic and ferruginous Lac Pavin (France), which can serve as a modern analogue of the Archean ocean. A depth-profile in the water column of Lac Pavin shows a remarkable increase in dissolved Fe concentration (0.1-1200 μM) and δ56Fe values (-2.14‰ to +0.31‰) across the oxic-anoxic boundary to the lake bottom. The largest Fe isotope variability is found at the redox boundary and is related to partial oxidation of dissolved ferrous iron, leaving the residual Fe enriched in light isotopes. The analysis of four sediment cores collected along a lateral profile (one in the oxic layer, one at the redox boundary, one in the anoxic zone, and one at the bottom of the lake) indicates that bulk sediments, porewaters, and reactive Fe mostly have δ56Fe values near 0.0 ± 0.2‰, similar to detrital iron. In contrast, pyrite δ56Fe values in sub-chemocline cores (60, 65, and 92 m) are highly variable and show significant deviations from the detrital iron isotope composition (δ56Fepyrite between -1.51‰ and +0.09‰; average -0.93‰). Importantly, the pyrite δ56Fe values mirror the δ56Fe of dissolved iron at the redox boundary—where near quantitative sulfate and sulfide drawdown occurs—suggesting limited iron isotope fractionation during iron sulfide formation. This finding has important implications for the Archean environment. Specifically, this work suggests that in a ferruginous system, most of the Fe isotope variability observed in sedimentary pyrites can

  19. Molecular Determinants of Substrate Specificity in Plant 5-Methylthioadenosine Nucleosidases

    Energy Technology Data Exchange (ETDEWEB)

    Siu,K.; Lee, J.; Sufrin, J.; Moffatt, B.; McMillan, M.; Cornell, K.; Isom, C.; Howell, L.

    2008-01-01

    5?-Methylthioadenosine (MTA)/S-adenosylhomocysteine (SAH) nucleosidase (MTAN) is essential for cellular metabolism and development in many bacterial species. While the enzyme is found in plants, plant MTANs appear to select for MTA preferentially, with little or no affinity for SAH. To understand what determines substrate specificity in this enzyme, MTAN homologues from Arabidopsis thaliana (AtMTAN1 and AtMTAN2, which are referred to as AtMTN1 and AtMTN2 in the plant literature) have been characterized kinetically. While both homologues hydrolyze MTA with comparable kinetic parameters, only AtMTAN2 shows activity towards SAH. AtMTAN2 also has higher catalytic activity towards other substrate analogues with longer 5?-substituents. The structures of apo AtMTAN1 and its complexes with the substrate- and transition-state-analogues, 5?-methylthiotubercidin and formycin A, respectively, have been determined at 2.0-1.8 Angstroms resolution. A homology model of AtMTAN2 was generated using the AtMTAN1 structures. Comparison of the AtMTAN1 and AtMTAN2 structures reveals that only three residues in the active site differ between the two enzymes. Our analysis suggests that two of these residues, Leu181/Met168 and Phe148/Leu135 in AtMTAN1/AtMTAN2, likely account for the divergence in specificity of the enzymes. Comparison of the AtMTAN1 and available Escherichia coli MTAN (EcMTAN) structures suggests that a combination of differences in the 5?-alkylthio binding region and reduced conformational flexibility in the AtMTAN1 active site likely contribute to its reduced efficiency in binding substrate analogues with longer 5?-substituents. In addition, in contrast to EcMTAN, the active site of AtMTAN1 remains solvated in its ligand-bound forms. As the apparent pKa of an amino acid depends on its local environment, the putative catalytic acid Asp225 in AtMTAN1 may not be protonated at physiological pH and this suggests the transition state of AtMTAN1, like human MTA phosphorylase and

  20. Substrate specificity and molecular modelling of the feline herpesvirus-1 thymidine kinase.

    Science.gov (United States)

    Hussein, Islam T M; Miguel, Ricardo Núñez; Tiley, Laurence S; Field, Hugh J

    2008-01-01

    Feline herpesvirus-1 (FHV-1) causes a severe upper respiratory and ocular disease in cats. An effective antiviral compound is required for treating FHV-1 infections. The virus-encoded thymidine kinase (TK) is the molecular basis for selective activation of commonly used antiviral nucleoside analogue drugs, e.g. acyclovir (ACV), penciclovir (PCV) and ganciclovir (GCV). The substrate specificity of a recombinant FHV-1 TK, expressed in Escherichia coli, was studied. FHV-1 TK efficiently phosphorylated its natural substrate deoxythymidine. However, it exhibited relatively lower affinity for the guanosine analogue substrates. PCV was most efficiently phosphorylated, followed by GCV, with approximately twofold reduction in the phosphorylation rate. The lowest phosphorylation rate was recorded for ACV. To correlate these biochemical data with structural features of the FHV-1 TK, a three-dimensional (3D) model of this enzyme was constructed based on sequence homology with two other herpesviral TKs, encoded by equine herpesvirus-4 (EHV-4) and herpes simplex-1 (HSV-1). Mutational analysis of the amino acids forming the FHV-1 TK active site identified two residues (Y29 and F144) as being critical for the differential ability of this enzyme to phosphorylate nucleoside analogues. A double substitution of Y29H/F144Y resulted in a threefold increase in the ACV phosphorylation rate.

  1. MARKOV GRAPHS OF ONE–DIMENSIONAL DYNAMICAL SYSTEMS AND THEIR DISCRETE ANALOGUES AND THEIR DISCRETE ANALOGUES

    Directory of Open Access Journals (Sweden)

    SERGIY KOZERENKO

    2016-04-01

    Full Text Available One feature of the famous Sharkovsky’s theorem is that it can be proved using digraphs of a special type (the so–called Markov graphs. The most general definition assigns a Markov graph to every continuous map from the topological graph to itself. We show that this definition is too broad, i.e. every finite digraph can be viewed as a Markov graph of some one–dimensional dynamical system on a tree. We therefore consider discrete analogues of Markov graphs for vertex maps on combinatorial trees and characterize all maps on trees whose discrete Markov graphs are of the following types: complete, complete bipartite, the disjoint union of cycles, with every arc being a loop.

  2. Preparation and phytotoxicity of sorgoleone analogues

    Directory of Open Access Journals (Sweden)

    Luiz Cláudio de Almeida Barbosa

    2001-12-01

    Full Text Available 3,5-Dimethoxybenzylic alcohol was converted into the 2-acetoxy-5-methoxy-3-(pent-1-yl-1,4-benzoquinone (12, in seven steps, with an overall yield of 14.6%. The natural quinone sorgoleone (1 was isolated from Sorghum bicolor and converted into the corresponding quinone (13 having a saturated side chain. The selective effects of these compounds (1, 12 and 13, at the dose of 5.6 mug of a.i./ g of substrate, on the growth of Cucumis sativus, Lactuca sativa, Desmodium tortuosum, Hyptis suaveolens and Euphorbia heterophylla were evaluated. All three compounds caused some inhibition on the root growth of the test plants (0.0-69.19% with the aerial parts less affected. The results showed that the triene unit of the sorgoleone side chain is not essential for the phytotoxicity and also the synthetic quinone was as active as the natural product.

  3. Engineering of insulin receptor isoform-selective insulin analogues.

    Directory of Open Access Journals (Sweden)

    Tine Glendorf

    Full Text Available BACKGROUND: The insulin receptor (IR exists in two isoforms, A and B, and the isoform expression pattern is tissue-specific. The C-terminus of the insulin B chain is important for receptor binding and has been shown to contact the IR just adjacent to the region where the A and B isoforms differ. The aim of this study was to investigate the importance of the C-terminus of the B chain in IR isoform binding in order to explore the possibility of engineering tissue-specific/liver-specific insulin analogues. METHODOLOGY/PRINCIPAL FINDINGS: Insulin analogue libraries were constructed by total amino acid scanning mutagenesis. The relative binding affinities for the A and B isoform of the IR were determined by competition assays using scintillation proximity assay technology. Structural information was obtained by X-ray crystallography. Introduction of B25A or B25N mutations resulted in analogues with a 2-fold preference for the B compared to the A isoform, whereas the opposite was observed with a B25Y substitution. An acidic amino acid residue at position B27 caused an additional 2-fold selective increase in affinity for the receptor B isoform for analogues bearing a B25N mutation. Furthermore, the combination of B25H with either B27D or B27E also resulted in B isoform-preferential analogues (2-fold preference even though the corresponding single mutation analogues displayed no differences in relative isoform binding affinity. CONCLUSIONS/SIGNIFICANCE: We have discovered a new class of IR isoform-selective insulin analogues with 2-4-fold differences in relative binding affinities for either the A or the B isoform of the IR compared to human insulin. Our results demonstrate that a mutation at position B25 alone or in combination with a mutation at position B27 in the insulin molecule confers IR isoform selectivity. Isoform-preferential analogues may provide new opportunities for developing insulin analogues with improved clinical benefits.

  4. Central effects of angiotensin II, its fragment and analogues.

    Science.gov (United States)

    Georgiev, V P; Klousha, V E; Petkov, V D; Markovska, V L; Svirskis, S V; Mountsinietse, R K; Anouans, Z E

    1984-01-01

    The effects of the octapeptide angiotensin II (AT II), its fragment Ile8 AT3-8 and the analogues Sar1 Ala8 AT II, Ala8 AT II and Ile8 AT II were studied with respect to: the level of biogenic amines (DA, 5-HT and their metabolites HVA and 5-HIAA) in the forebrain; the behaviour of the animals--haloperidol catalepsy, apomorphine stereotypy, unconditioned jumping reaction (UJR), convulsive threshold. Good correlation was found between the biochemical and behavioural effects. The fragment of AT II where phenylalanine is substituted at the C-terminal by Ile reduces the haloperidol-increased content of HVA, potentiates apomorphine stereotypy and reduces catalepsy, whereas the AT II analogues (where the C-terminal phenylalanine is substituted by Ala, and the N-terminal--by Sar) potentiate the effect of haloperidol increasing the HVA content, reduce apomorphine stereotypy and potentiate catalepsy; saralasine independently applied induces brief catalepsy; AT II, its fragment and analogues inhibit UJR, in combination with amphetamine and PTZ this effect becomes deeper; the duration of hexobarbital sleep is increased. The peptides investigated increase the convulsive threshold. The results show that the hexapeptide fragment has preserved the effects of AT II, whereas in the analogues (with changed C- and N-terminals) they are changed. The results obtained may be explained with the modulating influence of AT II-receptors on the DA-ergic receptors in the brain structures with which AT II and its fragment and analogues enter in contact.

  5. Molecular mechanism of allosteric substrate activation in a thiamine diphosphate-dependent decarboxylase.

    Science.gov (United States)

    Versées, Wim; Spaepen, Stijn; Wood, Martin D H; Leeper, Finian J; Vanderleyden, Jos; Steyaert, Jan

    2007-11-30

    Thiamine diphosphate-dependent enzymes are involved in a wide variety of metabolic pathways. The molecular mechanism behind active site communication and substrate activation, observed in some of these enzymes, has since long been an area of debate. Here, we report the crystal structures of a phenylpyruvate decarboxylase in complex with its substrates and a covalent reaction intermediate analogue. These structures reveal the regulatory site and unveil the mechanism of allosteric substrate activation. This signal transduction relies on quaternary structure reorganizations, domain rotations, and a pathway of local conformational changes that are relayed from the regulatory site to the active site. The current findings thus uncover the molecular mechanism by which the binding of a substrate in the regulatory site is linked to the mounting of the catalytic machinery in the active site in this thiamine diphosphate-dependent enzyme.

  6. Dewetting on microstructured substrates

    Science.gov (United States)

    Kim, Taehong; Kim, Wonjung

    2016-11-01

    A thin liquid film has an equilibrium thickness in such a way as to minimize the free energy. When a liquid film thickness is out of its equilibrium, the film seeks its equilibrium state, resulting in dynamics of liquid film, which are referred to as wetting and dewetting, depending on the flow direction. We here present a combined experimental and theoretical investigation of dewetting on a substrate with parallel microstructures. Our experiments show that residue may remain on the substrate after dewetting, and residue morphologies can be classified into three modes. Based on our experimental observations, we elucidate how the modes depend on the pattern morphology and contact angle, and develop a model for the contact line motion. Our results provide a basis for controlling the thickness film, which is important for many practical applications such as oil recovery, detergency, lithography, and cleaning. This work was supported by the National Research Foundation of Korea (NRF) Grant funded by the Korea government (MSIP) (No.2015R1A2A2A04006181).

  7. The Immucillins: Design, Synthesis and Application of Transition- State Analogues.

    Science.gov (United States)

    Evans, Gary B; Schramm, Vern L; Tyler, Peter C

    2015-01-01

    Transition-state analysis based on kinetic isotope effects and computational chemistry provides electrostatic potential maps to serve as blueprints for the design and chemical synthesis of transition-state analogues. The utility of these molecules is exemplified by potential clinical applications toward leukemia, autoimmune disorders, gout, solid tumors, bacterial quorum sensing and bacterial antibiotics. In some cases, transition-state analogues have chemical features that have allowed them to be repurposed for new indications, including potential antiviral use. Three compounds from this family have entered clinical trials. The transition-state analogues bind to their target proteins with high affinity and specificity. The physical and structural properties of binding teach valuable and often surprising lessons about the nature of tight-binding inhibitors.

  8. Gold Nanoparticles Decorated with Mannose-6-phosphate Analogues

    Directory of Open Access Journals (Sweden)

    Stéphanie Combemale

    2014-01-01

    Full Text Available Herein, the preparation of neoglycoconjugates bearing mannose-6-phosphate analogues is described by: (a synthesis of a cyclic sulfate precursor to access the carbohydrate head-group by nucleophilic displacement with an appropriate nucleophile; (b introduction of spacers on the mannose-6-phosphate analogues via Huisgen’s cycloaddition, the Julia reaction, or the thiol-ene reaction under ultrasound activation. With the resulting compounds in hand, gold nanoparticles could be functionalized with various carbohydrate derivatives (glycoconjugates and then tested for angiogenic activity. It was observed that the length and flexibility of the spacer separating the sugar analogue from the nanoparticle have little influence on the biological response. One particular nanoparticle system substantially inhibits blood vessel growth in contrast to activation by the corresponding monomeric glycoconjugate, thereby demonstrating the importance of multivalency in angiogenic activity.

  9. Analogue peptides for the immunotherapy of human acute myeloid leukemia.

    Science.gov (United States)

    Hofmann, Susanne; Mead, Andrew; Malinovskis, Aleksandrs; Hardwick, Nicola R; Guinn, Barbara-Ann

    2015-11-01

    The use of peptide vaccines, enhanced by adjuvants, has shown some efficacy in clinical trials. However, responses are often short-lived and rarely induce notable memory responses. The reason is that self-antigens have already been presented to the immune system as the tumor develops, leading to tolerance or some degree of host tumor cell destruction. To try to break tolerance against self-antigens, one of the methods employed has been to modify peptides at the anchor residues to enhance their ability to bind major histocompatibility complex molecules, extending their exposure to the T-cell receptor. These modified or analogue peptides have been investigated as stimulators of the immune system in patients with different cancers with variable but sometimes notable success. In this review we describe the background and recent developments in the use of analogue peptides for the immunotherapy of acute myeloid leukemia describing knowledge useful for the application of analogue peptide treatments for other malignancies.

  10. Synthesis and cytotoxic activities of semisynthetic zearalenone analogues.

    Science.gov (United States)

    Tadpetch, Kwanruthai; Kaewmee, Benyapa; Chantakaew, Kittisak; Kantee, Kawalee; Rukachaisirikul, Vatcharin; Phongpaichit, Souwalak

    2016-08-01

    Zearalenone is a β-resorcylic acid macrolide with various biological activities. Herein we report the synthesis and cytotoxic activities of 34 zearalenone analogues against human oral epidermoid carcinoma (KB) and human breast adenocarcinoma (MCF-7) cells as well as noncancerous Vero cells. Some zearalenone analogues showed moderately enhanced cytotoxic activities against the two cancer cell lines. We have discovered the potential lead compounds with diminished or no cytotoxicity to Vero cells. Preliminary structure-activity relationship studies revealed that the double bond at the 1' and 2' positions of zearalenone core was crucial for cytotoxic activities on both cell lines. In addition, for zearalenol analogues, the unprotected hydroxyl group at C-2 and an alkoxy substituent at C-4 played key roles on cytotoxic effects of both cell lines.

  11. Conception, synthesis, and biological evaluation of original discodermolide analogues.

    Science.gov (United States)

    de Lemos, Elsa; Agouridas, Evangelos; Sorin, Geoffroy; Guerreiro, Antonio; Commerçon, Alain; Pancrazi, Ange; Betzer, Jean-François; Lannou, Marie-Isabelle; Ardisson, Janick

    2011-08-29

    Due to its intriguing biological activity profile and potential chemotherapeutic application discodermolide (DDM) proved to be an attractive target. Therefore, notable efforts have been carried out directed toward its total synthesis and toward the production and evaluation of synthetic analogues. Recently, we achieved the total synthesis of DDM. At the present, guided by the knowledge gained during our DDM total synthesis and by the requirement of keeping the bioactive "U" shape conformation, we report the convergent preparation of five original analogues. Three types of changes were realized through modification of the terminal (Z)-diene moiety, of the methyl group at the C14-position, and the lactone region. All analogues were active in the nanomolar range and two of them turned out to be equipotent to DDM.

  12. Ensemble meteorological reconstruction using circulation analogues of 1781–1785

    Directory of Open Access Journals (Sweden)

    P. Yiou

    2013-09-01

    Full Text Available This paper uses a method of atmospheric flow analogues to reconstruct an ensemble of atmospheric variables (namely sea-level pressure, surface temperature and wind speed between 1781 and 1785. The properties of this ensemble are investigated and tested against observations of temperature. The goal of the paper is to assess whether the atmospheric circulation during the Laki volcanic eruption (in 1783 and the subsequent winter were similar to the conditions that prevailed in the winter 2009/2010 and during spring 2010. We find that the three months following the Laki eruption in June 1783 barely have analogues in 2010. The cold winter of 1783/1784 yields circulation analogues in 2009/2010. Our analysis suggests that it is unlikely that the Laki eruption was responsible for the cold winter of 1783/1784, of the relatively short memory of the atmospheric circulation.

  13. Synthesis and cytotoxic activity of novel curcumin analogues

    Institute of Scientific and Technical Information of China (English)

    Qin Zhang; Yao Fu; Hao Wei Wang; Tao Gong; Yong Qin; Zhi Rong Zhang

    2008-01-01

    Five novel curcumin analogues bearing different substituents at 4-position of phenyl group were synthesized. Their structures were confirmed by NMR and HRMS spectrum. Their cytotoxic activities against six tumor cell lines were tested by the standard MTT assay in vitro. The results indicated that four analogues (1A-1C, 1E) with solubilizing moieties showed selective potent cytotoxicity against HepG2, HeLa and CT26 cell lines, and analogue 1A and 1C exhibited more potent cytotoxicity than curcumin against CT26 cell line. It was suggested that introduction of appropriate substituents to 4-position of phenyl group might be a potential option for structural modification of curcumin.

  14. Synthesis and Biological Evaluation of New (-)-Englerin Analogues.

    Science.gov (United States)

    López-Suárez, Laura; Riesgo, Lorena; Bravo, Fernando; Ransom, Tanya T; Beutler, John A; Echavarren, Antonio M

    2016-05-01

    We report the synthesis and biological evaluation of a series of (-)-englerin A analogues obtained along our previously reported synthetic route based on a stereoselective gold(I) cycloaddition process. This synthetic route is a convenient platform to access analogues with broad structural diversity and has led us to the discovery of unprecedented and easier-to-synthesize derivatives with an unsaturation in the cyclopentyl ring between C4 and C5. We also introduce novel analogues in which the original isopropyl motif has been substituted with cyclohexyl, phenyl, and cyclopropyl moieties. The high selectivity and growth-inhibitory activity shown by these new derivatives in renal cancer cell lines opens new ways toward the final goal of finding effective drugs for the treatment of renal cell carcinoma (RCC).

  15. Controlled analogue experiments on propagation of seismic electromagnetic signals

    Institute of Scientific and Technical Information of China (English)

    HUANG Qinghua

    2005-01-01

    This study presented a method of laboratory analogue experiments based on a geographical scaling model and a waveguide model to investigate the characteristics of the propagation of seismic electromagnetic signals in the crust and the atmosphere. Some controlled experiments were done to evaluate the possible influence on the experimental results from the background electromagnetic field, geographical conditions, boundary effects, the source of electromagnetic signals (position, magnitude, and frequency), and media conductivity. The reliability and the extensibility of the above analogue experimental method were also investigated. This study indicated that such kind of analogue experimental method provided an intuitionistic way of studying the propagation of seismic electromagnetic signals, which is one of the most difficult research topics in seismo-electro- magnetism.

  16. Largazole Analogues Embodying Radical Changes in the Depsipeptide Ring: Development of a More Selective and Highly Potent Analogue.

    Science.gov (United States)

    Almaliti, Jehad; Al-Hamashi, Ayad A; Negmeldin, Ahmed T; Hanigan, Christin L; Perera, Lalith; Pflum, Mary Kay H; Casero, Robert A; Tillekeratne, L M Viranga

    2016-12-08

    A number of analogues of the marine-derived histone deacetylase inhibitor largazole incorporating major structural changes in the depsipeptide ring were synthesized. Replacing the thiazole-thiazoline fragment of largazole with a bipyridine group gave analogue 7 with potent cell growth inhibitory activity and an activity profile similar to that of largazole, suggesting that conformational change accompanying switching hybridization from sp(3) to sp(2) at C-7 is well tolerated. Analogue 7 was more class I selective compared to largazole, with at least 464-fold selectivity for class I HDAC proteins over class II HDAC6 compared to a 22-fold selectivity observed with largazole. To our knowledge 7 represents the first example of a potent and highly cytotoxic largazole analogue not containing a thiazoline ring. The elimination of a chiral center derived from the unnatural amino acid R-α-methylcysteine makes the molecule more amenable to chemical synthesis, and coupled with its increased class I selectivity, 7 could serve as a new lead compound for developing selective largazole analogues.

  17. Maintainable substrate carrier for electroplating

    Science.gov (United States)

    Chen, Chen-An [Milpitas, CA; Abas, Emmanuel Chua [Laguna, PH; Divino, Edmundo Anida [Cavite, PH; Ermita, Jake Randal G [Laguna, PH; Capulong, Jose Francisco S [Laguna, PH; Castillo, Arnold Villamor [Batangas, PH; Ma,; Xiaobing, Diana [Saratoga, CA

    2012-07-17

    One embodiment relates to a substrate carrier for use in electroplating a plurality of substrates. The carrier includes a non-conductive carrier body on which the substrates are placed and conductive lines embedded within the carrier body. A plurality of conductive clip attachment parts are attached in a permanent manner to the conductive lines embedded within the carrier body. A plurality of contact clips are attached in a removable manner to the clip attachment parts. The contact clips hold the substrates in place and conductively connecting the substrates with the conductive lines. Other embodiments, aspects and features are also disclosed.

  18. Maintainable substrate carrier for electroplating

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Chen-An; Abas, Emmanuel Chua; Divino, Edmundo Anida; Ermita, Jake Randal G.; Capulong, Jose Francisco S.; Castillo, Arnold Villamor; Ma, Diana Xiaobing

    2016-08-02

    One embodiment relates to a substrate carrier for use in electroplating a plurality of substrates. The carrier includes a non-conductive carrier body on which the substrates are placed and conductive lines embedded within the carrier body. A plurality of conductive clip attachment parts are attached in a permanent manner to the conductive lines embedded within the carrier body. A plurality of contact clips are attached in a removable manner to the clip attachment parts. The contact clips hold the substrates in place and conductively connecting the substrates with the conductive lines. Other embodiments, aspects and features are also disclosed.

  19. Synthesis of daidzin analogues as potential agents for alcohol abuse.

    Science.gov (United States)

    Gao, Guang-Yao; Li, Dian-Jun; Keung, Wing Ming

    2003-09-01

    Daidzin, the active principle of an herbal remedy for 'alcohol addiction', has been shown to reduce alcohol consumption in all laboratory animals tested to date. Correlation studies using structural analogues of daidzin suggests that it acts by raising the monoamine oxidase (MAO)/mitochondrial aldehyde dehydrogenase (ALDH-2) activity ratio (J. Med. Chem. 2000, 43, 4169). Structure-activity relationship (SAR) studies on the 7-O-substituted analogues of daidzin have revealed structural features important for ALDH-2 and MAO inhibition (J. Med. Chem. 2001, 44, 3320). We here evaluated effects of substitutions at 2, 5, 6, 8, 3' and 4' positions of daidzin on its potencies for ALDH-2 and MAO inhibition. Results show that analogues with 4'-substituents that are small, polar and with hydrogen bonding capacities are most potent ALDH-2 inhibitors, whereas those that are non-polar and with electron withdrawing capacities are potent MAO inhibitors. Analogues with a 5-OH group are less potent ALDH-2 inhibitors but are more potent MAO inhibitors. All the 2-, 6-, 8- and 3'-substituted analogues tested so far do not inhibit ALDH-2 and/or have decreased potencies for MAO inhibition. This, together with the results obtained from previous studies, suggests that a potent antidipsotropic analogue would be a 4',7-disubstituted isoflavone. The 4'-substituent should be small, polar, and with hydrogen bonding capacities such as, -OH and -NH(2); whereas the 7-substituent should be a straight-chain alkyl with a terminal polar function such as -(CH(2))(n)-OH with 2 or =4.

  20. Rhenium complexes of chromophore-appended dipicolylamine ligands: syntheses, spectroscopic properties, DNA binding and X-ray crystal structure

    Energy Technology Data Exchange (ETDEWEB)

    Mullice, L.A.; Buurma, N.J.; Pope, S.J.A. [Cardiff Univ., School of Chemistry (United Kingdom); Laye, R.H. [Sheffield Univ., Dept. of Chemistry (United Kingdom); Harding, L.P. [Huddersfield Univ., School of Biological and Chemical Sciences (United Kingdom)

    2008-12-15

    The syntheses of two chromophore-appended dipicolylamine-derived ligands and their reactivity with penta-carbonyl-chloro-rhenium have been studied. The resultant complexes each possess the fac-Re(CO){sub 3} core. The ligands L{sup 1} 1-[bis(pyridine-2-yl-methyl)amino]methyl-pyrene and L{sup 2} 2-[bis(pyridine-2-yl-methyl)amino]methyl-quinoxaline were isolated via a one-pot reductive amination in moderate yield. The corresponding rhenium complexes were isolated in good yields and characterised by {sup 1}H NMR, MS, IR and UV-Vis studies. X-Ray crystallographic data were obtained for fac-{l_brace}Re(CO){sub 3}(L{sup 1}){r_brace}(BF{sub 4}), C{sub 34}H{sub 26}BF{sub 4}N{sub 4}O{sub 3}Re: monoclinic, P2(1)/c, a 18.327(2) Angstroms, {alpha} = 90.00 degrees, b 14.1537(14) Angstroms, {beta}96.263(6) degrees, c = 23.511(3) Angstroms, {gamma} 90.00 Angstroms, 6062.4(11) (Angstroms){sup 3}, Z=8. The luminescence properties of the ligands and complexes were also investigated, with the emission attributed to the appended chromophore in each case. Isothermal titration calorimetry suggests that fac-{l_brace}Re(CO){sub 3}(L{sup 1}){r_brace}(BF{sub 4}) self-aggregates cooperatively in aqueous solution, probably forming micelle-like aggregates with a cmc of 0.18 mM. Investigations into the DNA-binding properties of fac-{l_brace}Re(CO){sub 3}(L{sup 1}){r_brace}(BF{sub 4}) were undertaken and revealed that fac-{l_brace}Re(CO){sub 3}(L{sup 1}){r_brace}(BF{sub 4}) binding to fish sperm DNA (binding constant 1.5 {+-} 0.2 * 10{sup 5} M{sup -1}, binding site size 3.2 {+-} 0.3 base pairs) is accompanied by changes in the UV-Vis spectrum as typically observed for pyrene-based intercalators while the calorimetrically determined binding enthalpy (-14 {+-} 2 kcal mol{sup -1}) also agrees favourably with values as typically found for intercalators. (authors)

  1. Parameterization of the light absorption properties of chromophoric dissolved organic matter in the Baltic Sea and Pomeranian lakes

    Science.gov (United States)

    Meler, Justyna; Kowalczuk, Piotr; Ostrowska, Mirosława; Ficek, Dariusz; Zabłocka, Monika; Zdun, Agnieszka

    2016-08-01

    This study presents three alternative models for estimating the absorption properties of chromophoric dissolved organic matter aCDOM(λ). For this analysis we used a database containing 556 absorption spectra measured in 2006-2009 in different regions of the Baltic Sea (open and coastal waters, the Gulf of Gdańsk and the Pomeranian Bay), at river mouths, in the Szczecin Lagoon and also in three lakes in Pomerania (Poland) - Obłęskie, Łebsko and Chotkowskie. The variability range of the chromophoric dissolved organic matter (CDOM) absorption coefficient at 400 nm, aCDOM(400), lay within 0.15-8.85 m-1. The variability in aCDOM(λ) was parameterized with respect to the variability over 3 orders of magnitude in the chlorophyll a concentration Chl a (0.7-119 mg m-3). The chlorophyll a concentration and aCDOM(400) were correlated, and a statistically significant, nonlinear empirical relationship between these parameters was derived (R2 = 0.83). On the basis of the covariance between these parameters, we derived two empirical mathematical models that enabled us to design the CDOM absorption coefficient dynamics in natural waters and reconstruct the complete CDOM absorption spectrum in the UV and visible spectral domains. The input variable in the first model was the chlorophyll a concentration, and in the second one it was aCDOM(400). Both models were fitted to a power function, and a second-order polynomial function was used as the exponent. Regression coefficients for these formulas were determined for wavelengths from 240 to 700 nm at 5 nm intervals. Both approximations reflected the real shape of the absorption spectra with a low level of uncertainty. Comparison of these approximations with other models of light absorption by CDOM demonstrated that our parameterizations were superior (bias from -1.45 to 62 %, RSME from 22 to 220 %) for estimating CDOM absorption in the optically complex waters of the Baltic Sea and Pomeranian lakes.

  2. Synthesis of Novel 1,3-Dioxolane Nucleoside Analogues

    Institute of Scientific and Technical Information of China (English)

    蔡冬梅; 林昆华; 李明宗; 温集武; 李鸿艳; 尤田耙

    2004-01-01

    Novel 1,3-dioxolane C-nucleoside analogues of tiazofurin 2-(2-hydroxymethyl-1,3-dioxolan-4-yl)-1,3-thiazole-4-carboxamide as well as N-nucleoside analogues of substituted imidazoles 1-(2-hydroxymethyl-1,3-dioxolan-4-yl)-4-nitroimidazole and 1-(2-hydroxymethyl-1,3-dioxolan-4-yl)-4,5-dicyanoimidazole were synthesized frommethyl acrylate through a multistep procedure. Their structures were confirmed by IR, 1H NMR, 13C NMR spectra and elemental analysis.

  3. Analogue Building Blocks Based on Digital CMOS Gates

    DEFF Research Database (Denmark)

    Mucha, Igor

    1996-01-01

    Low-performance analogue circuits built of digital MOS gates are presented. Depending on the threshold voltages of the technology used the final circuits can be operated using low supply voltages. The main advantage using the proposed circuits is the simplicity and ultimate compatibility with the......Low-performance analogue circuits built of digital MOS gates are presented. Depending on the threshold voltages of the technology used the final circuits can be operated using low supply voltages. The main advantage using the proposed circuits is the simplicity and ultimate compatibility...

  4. Five new discodermolide analogues from the marine sponge Discodermia species.

    Science.gov (United States)

    Gunasekera, Sarath P; Paul, Gopal K; Longley, Ross E; Isbrucker, Richard A; Pomponi, Shirley A

    2002-11-01

    Discodermolide (1) and five new discodermolide analogues trivially named 2-epi-discodermolide (2), 2-des-methyldiscodermolide (3), 5-hydroxymethyldiscodermolate (4), 19-des-aminocarbonyldiscodermolide (5), and 9(13)-cyclodiscodermolide (6) have been isolated from marine sponges belonging to the genus Discodermia collected from the Caribbean Sea. The isolation, structure elucidation, and biological activities of 2-6 are described. The natural analogues, which were isolated in trace amounts, exhibited significant variation of cytotoxicity against the cultured murine P-388 leukemia and A-549 human adenocarcinoma cells and suggested the importance of the C(7) through C(17) moiety for potency against cultured tumor cell lines.

  5. Synthesis and evaluation of heterocyclic analogues of bromoxynil.

    Science.gov (United States)

    Cutulle, Matthew A; Armel, Gregory R; Brosnan, James T; Best, Michael D; Kopsell, Dean A; Bruce, Barry D; Bostic, Heidi E; Layton, Donovan S

    2014-01-15

    One attractive strategy to discover more active and/or crop-selective herbicides is to make structural changes to currently registered compounds. This strategy is especially appealing for those compounds with limited herbicide resistance and whose chemistry is accompanied with transgenic tools to enable herbicide tolerance in crop plants. Bromoxynil is a photosystem II (PSII) inhibitor registered for control of broadleaf weeds in several agronomic and specialty crops. Recently at the University of Tennessee-Knoxville several analogues of bromoxynil were synthesized including a previously synthesized pyridine (2,6-dibromo-5-hydroxypyridine-2-carbonitrile sodium salt), a novel pyrimidine (4,6-dibromo-5-hydroxypyrimidine-2-carbonitrile sodium salt), and a novel pyridine N-oxide (2,6-dibromo-1-oxidopyridin-1-ium-4-carbonitrile). These new analogues of bromoxynil were also evaluated for their herbicidal activity on soybean (Glycine max), cotton (Gossypium hirsutum), redroot pigweed (Amaranthus retroflexus), velvetleaf (Abutilon theophrasti), large crabgrass (Digitaria sanguinalis), and pitted morningglory ( Ipomoea lacunose ) when applied at 0.28 kg ha(-1). A second study was conducted on a glyphosate-resistant weed (Amaranthus palmeri) with the compounds being applied at 0.56 kg ha(-1). Although all compounds were believed to inhibit PSII by binding in the quinone binding pocket of D1, the pyridine and pyridine-N-oxide analogues were clearly more potent than bromoxynil on Amaranthus retroflexus. However, application of the pyrimidine herbicide resulted in the least injury to all species tested. These variations in efficacy were investigated using molecular docking simulations, which indicate that the pyridine analogue may form a stronger hydrogen bond in the pocket of the D1 protein than the original bromoxynil. A pyridine analogue was able to control the glyphosate-resistant Amaranthus palmeri with >80% efficacy. The pyridine analogues of bromoxynil showed potential

  6. Naturally occurring crystalline phases: analogues for radioactive waste forms

    Energy Technology Data Exchange (ETDEWEB)

    Haaker, R.F.; Ewing, R.C.

    1981-01-01

    Naturally occurring mineral analogues to crystalline phases that are constituents of crystalline radioactive waste forms provide a basis for comparison by which the long-term stability of these phases may be estimated. The crystal structures and the crystal chemistry of the following natural analogues are presented: baddeleyite, hematite, nepheline; pollucite, scheelite;sodalite, spinel, apatite, monazite, uraninite, hollandite-priderite, perovskite, and zirconolite. For each phase in geochemistry, occurrence, alteration and radiation effects are described. A selected bibliography for each phase is included.

  7. Analogue Kerr-like geometries in a MHD inflow

    CERN Document Server

    Noda, Sousuke; Takahashi, Masaaki

    2016-01-01

    We present a model of the analogue black hole in magnetohydrodynamic (MHD) flow. For a two dimensional axisymmetric stationary trans-magnetosonic inflow with a sink, using the dispersion relation of the MHD waves, we introduce the effective geometries for magnetoacoustic waves propagating in the MHD flow. Investigating the properties of the effective potentials for magnetoacoustic rays, we find that the effective geometries can be classified into five types which include analogue spacetimes of the Kerr black hole, ultra spinning stars with ergoregions and spinning stars without ergoregions. We address the effects of the magnetic pressure and the magnetic tension on each magnetoacoustic geometries.

  8. An investigation of electronic structure and properties of new chromophore: 3,3'-bithiazolo[3,4-a]pyridinium perchlorate

    Energy Technology Data Exchange (ETDEWEB)

    Liu Shixia [Departement fuer Chemie und Biochemie, Universitaet Bern, Freiestrasse 3, CH-3012 Bern (Switzerland)]. E-mail: liu@iac.unibe.ch; Tanner, Christian [Departement fuer Chemie und Biochemie, Universitaet Bern, Freiestrasse 3, CH-3012 Bern (Switzerland); Leutwyler, Samuel [Departement fuer Chemie und Biochemie, Universitaet Bern, Freiestrasse 3, CH-3012 Bern (Switzerland); Bigler, Peter [Departement fuer Chemie und Biochemie, Universitaet Bern, Freiestrasse 3, CH-3012 Bern (Switzerland); Decurtins, Silvio [Departement fuer Chemie und Biochemie, Universitaet Bern, Freiestrasse 3, CH-3012 Bern (Switzerland)

    2007-01-15

    The chromophore 3,3'-bithiazolo[3,4-a]pyridinium 1, obtained by oxidative cyclization reactions using a tetrathiafulvalene as a leaving group, strongly absorbs at the violet end of the visible region as evidenced by its yellow color. The solution (MeCN) spectrum displays an intensive, broad absorption band around 377 nm with a {epsilon} value of 8x10{sup 3} l mol{sup -1} cm{sup -1}. The chromophore also shows a strongly Stokes-shifted fluorescence emission with a lifetime {tau} of 2.8{+-}0.1 ns in acetonitrile solution. Herein, we describe the photophysical properties and a theoretical investigation of the electronic structure of the chiral dicationic, bis(bicyclic) ring assembly 1.

  9. Effect of lamellar nanostructures on the second harmonic generation of polymethylmethacrylate films doped with 4-(4-nitrophenylazo)aniline chromophores

    CERN Document Server

    Franco, Alfredo; Valverde-Aguilar, Guadalupe; García-Macedo, Jorge; Brusatin, Giovanna; Guglielmi, Massimo

    2011-01-01

    The kinetics of the orientation of Disperse Orange 3 molecules embedded in amorphous and nanostructured Polymethylmethacrylate films was studied under the effect of an intense electrostatic poling field. Non-centrosymmetric chromophore distributions were obtained in Polymethylmethacrylate films by Corona poling technique. These distributions depends on the Corona poling time. The changes in the orientation of the Disperse Orange 3 molecules were followed by in-situ transmitted Second Harmonic Generation measurements. The Second Harmonic Generation signal was recorded as function of time at several temperatures; it was fitted as function of the Corona poling time, considering matrix-chromophore interactions. The Polymethylmethacrylate films were nanostructured by the incorporation of an anionic surfactant, the Sodium Dodecyl Sulfate. The lamellar nanostructures in the films were identified by X-ray diffraction measurements.

  10. Nature of the lowest electron transitions in styryl bases benzothiazole derivatives and analogues bearing para-methoxy and -trifluoromethyl substituents in phenylyne moiety

    Science.gov (United States)

    Navozenko, O. M.; Naumenko, A. P.; Yashchuk, V. M.; Bricks, J. L.; Slominskii, Yu. L.; Ryabitskii, A. B.; Kachkovsky, O. D.

    2016-06-01

    Combined quantum-chemical and spectral investigation of cyanine bases derivatives of thiastyryls as well as their analogues with dimethylamino, metoxy and trifluorine-methyl substituents has been fulfilled. The calculations have shown that going from cationic styryl/metoxystyryl to the corresponding neutral bases is accompanied by substantial change of the equilibrium molecular geometry and charge distribution at atoms, while the experimental absorption band undergoes the essential hypsochromic shift. It is established that introducing on the donor groups in the bases causes negligible change of the carbon-carbon bond and atomic charges in the main chromophore, in contrast to the substantial changes of the magnitude and direction state dipole moments in both ground and excited states. It is found that the bases with the donor groups in benzthiazole moiety and with acceptor CF3 substituent demonstrate the inversion of the direction of the dipole moment. Based on the spectral and quantum-chemical study, one has proposed that some widening of the spectral bands is connected with the vibronic interaction, not with the second electron transition.

  11. Regiospecific attack of nitrogen and sulfur nucleophiles on quinones derived from poison oak/ivy catechols (urushiols) and analogues as models for urushiol-protein conjugate formation.

    Science.gov (United States)

    Liberato, D J; Byers, V S; Dennick, R G; Castagnoli, N

    1981-01-01

    Attempts to characterize potential biologically important covalent interactions between electrophilic quinones derived from catechols present in poison oak/ivy (urushiol) and biomacromolecules have led to the analysis of model reactions involving sulfur and amino nucleophiles with 3-heptadecylbenzoquinone. Characterization of the reaction products indicates that this quinone undergoes regiospecific attack by (S)-N-acetylcysteine at C-6 and by 1-aminopentane at C-5. The red solid obtained with 1-aminopentane proved to be 3-heptadecyl-5-(pentylamino)-1,2-benzoquinone. Analogous aminobenzoquinones were obtained with the quinones derived from the 4- and 6-methyl analogues of 3-pentadecylcatechol. All three adducts absorbed visible light at different wavelengths. When the starting catechols were incubated with human serum albumin almost identical chromophores were formed. These results establish that cathechols responsible for the production of the poison oak/ivy contact dermatitis in humans undergo a sequence of reactions in the presence of human serum albumin that lead to covalent attachment of the catechols to the protein via carbon-nitrogen bonds. Estimations of the extent of this binding indicate that, at least with human serum albumin, the reaction is quantitative.

  12. A practical synthesis of (+)-discodermolide and analogues: fragment union by complex aldol reactions.

    Science.gov (United States)

    Paterson, I; Florence, G J; Gerlach, K; Scott, J P; Sereinig, N

    2001-10-01

    A practical stereocontrolled synthesis of (+)-discodermolide (1) has been completed in 10.3% overall yield (23 steps longest linear sequence). The absolute stereochemistry of the C(1)-C(6) (7), C(9)-C(16) (8), and C(17)-C(24) (9) subunits was established via substrate-controlled, boron-mediated, aldol reactions of the chiral ethyl ketones 10, 11, and 12. Key fragment coupling reactions were a lithium-mediated, anti-selective, aldol reaction of aryl ester 8 (under Felkin-Anh induction from the aldehyde component 9), followed by in situ reduction to produce the 1,3-diol 40, and a (+)-diisopinocampheylboron chloride-mediated aldol reaction of methyl ketone 7 (overturning the inherent substrate induction from the aldehyde component 52) to give the (7S)-adduct 58. The flexibility of our overall strategy is illustrated by the synthesis of a number of diastereomers and structural analogues of discodermolide, which should serve as valuable probes for structure-activity studies.

  13. Inhibition of phosphatidylinositol-specific phospholipase C: studies on synthetic substrates, inhibitors and a synthetic enzyme.

    Science.gov (United States)

    Vizitiu, D; Kriste, A G; Campbell, A S; Thatcher, G R

    1996-01-01

    Enzyme inhibition studies on phosphatidylinositol-specific phospholipase C (PI-PLC) from B. Cereus were performed in order to gain an understanding of the mechanism of the PI-PLC family of enzymes and to aid inhibitor design. Inhibition studies on two synthetic cyclic phosphonate analogues (1,2) of inositol cyclic-1:2-monophosphate (cIP), glycerol-2-phosphate and vanadate were performed using natural phosphatidylinositol (PI) substrate in Triton X100 co-micelles and an NMR assay. Further inhibition studies on PI-PLC from B. Cereus were performed using a chromogenic, synthetic PI analogue (DPG-PI), an HPLC assay and Aerosol-OT (AOT), phytic acid and vanadate as inhibitors. For purposes of comparison, a model PI-PLC enzyme system was developed employing a synthetic Cu(II)-metallomicelle and a further synthetic PI analogue (IPP-PI). The studies employing natural PI substrate in Triton X100 co-micelles and synthetic DPG-PI in the absence of surfactant indicate three classes of PI-PLC inhibitors: (1) active-site directed inhibitors (e.g. 1,2); (2) water-soluble polyanions (e.g. tetravanadate, phytic acid); (3) surfactant anions (e.g. AOT). Three modes of molecular recognition are indicated to be important: (1) active site molecular recognition; (2) recognition at an anion-recognition site which may be the active site, and; (3) interfacial (or hydrophobic) recognition which may be exploited to increase affinity for the anion-recognition site in anionic surfactants such as AOT. The most potent inhibition of PI-PLC was observed by tetravanadate and AOT. The metallomicelle model system was observed to mimic PI-PLC in reproducing transesterification of the PI analogue substrate to yield cIP as product and in showing inhibition by phytic acid and AOT.

  14. Influence of environmental factors on spectral characteristics of chromophoric dissolved organic matter (CDOM) in Inner Mongolia Plateau, China

    Science.gov (United States)

    Wen, Z. D.; Song, K. S.; Zhao, Y.; Du, J.; Ma, J. H.

    2016-02-01

    Spectral characteristics of chromophoric dissolved organic matter (CDOM) were examined in conjunction with environmental factors in the waters of rivers and terminal lakes within the Hulun Buir plateau, northeast China. Dissolved organic carbon (DOC), total nitrogen (TN), and total phosphorous (TP) were significantly higher in terminal lakes than rivers waters (p RDA) indicated that the environmental variables total suspended matter (TSM), TN, and electrical conductivity (EC) had a strong correlation with light absorption characteristics, followed by total dissolved solid (TDS) and chlorophyll a. In most sampling locations, CDOM was the dominant non-water light-absorbing substance. Light absorption by non-algal particles often exceeded that by phytoplankton in the plateau waters. Study of these optical-physicochemical correlations is helpful in the evaluation of the potential influence of water quality factors on non-water light absorption in cold plateau water environments. The construction of a correlation between DOC concentration and water quality factors may help contribute to regional estimates of carbon sources and fate for catchment carbon budget assessments.

  15. Generalizing the correlated chromophore domain model of reversible photodegradation to include the effects of an applied electric field

    CERN Document Server

    Anderson, Benjamin

    2013-01-01

    All observations of photodegradation and self healing follow the predictions of the correlated chromophore domain model. [Ramini et.al. Polym. Chem., 2013, 4, 4948.] In the present work, we generalize the domain model to describe the effects of an electric field by including induced dipole interactions between molecules in a domain by means of a self-consistent field approach. This electric field correction is added to the statistical mechanical model to calculate the distribution of domains that are central to healing. Also included in the model are the dynamics due to the formation of an irreversibly damaged species. As in previous studies, the model with a one-dimensional domain best explains all experimental data of the population as a function of time, temperature, intensity, concentration, and now applied electric field. Though the nature of a domain is yet to be determined, the fact that only one-dimensional domain models are consistent with observations suggests that they might be made of correlated d...

  16. Temporal switching of homo-FRET pathways in single-chromophore dimer models of π-conjugated polymers.

    Science.gov (United States)

    Stangl, Thomas; Bange, Sebastian; Schmitz, Daniela; Würsch, Dominik; Höger, Sigurd; Vogelsang, Jan; Lupton, John M

    2013-01-01

    A set of π-conjugated oligomer dimers templated in molecular scaffolds is presented as a model system for studying the interactions between chromophores in conjugated polymers (CPs). Single-molecule spectroscopy was used to reveal energy transfer dynamics between two oligomers in either a parallel or oblique-angle geometry. In particular, the conformation of single molecules embedded in a host matrix was investigated via polarized excitation and emission fluorescence microscopy in combination with fluorescence correlation spectroscopy. While the intramolecular interchromophore conformation was found to have no impact on the fluorescence quantum yield, lifetime, or photon statistics (antibunching), the long-term nonequilibrium dynamics of energy transfer within these bichromophoric systems was accessible by studying the linear dichroism in emission at the single-molecule level, which revealed reversible switching of the emission between the two oligomers. In bulk polymer films, interchromophore coupling promotes the migration of excitation energy to quenching sites. Realizing the presence and dynamics of such interactions is crucial for understanding limitations on the quantum efficiency of larger CP materials.

  17. Primary structural response in tryptophan residues of Anabaena sensory rhodopsin to photochromic reactions of the retinal chromophore

    Science.gov (United States)

    Inada, Seisuke; Mizuno, Misao; Kato, Yoshitaka; Kawanabe, Akira; Kandori, Hideki; Wei, Zhengrong; Takeuchi, Satoshi; Tahara, Tahei; Mizutani, Yasuhisa

    2013-06-01

    Anabaena sensory rhodopsin (ASR) is a microbial rhodopsin found in eubacteria and functions as a photosensor. The photoreaction of ASR is photochromic between all-trans, 15-anti (ASRAT), and 13-cis, 15-syn (ASR13C) isomers. To understand primary protein dynamics in the photoreaction starting in ASRAT and ASR13C, picosecond time-resolved ultraviolet resonance Raman spectra were obtained. In the intermediate state appearing in the picosecond temporal region, spectral changes of Trp bands were observed. For both ASRAT and ASR13C, the intensities of the Trp bands were bleached within the instrumental response time and recovered with a time constant of 30 ps. This suggests that the rates of structural changes in the Trp residue in the vicinity of the chromophore do not depend on the direction of the isomerization of retinal. A comparison between spectra of the wild-type and Trp mutants indicates that the structures of Trp76 and Trp46 change upon the primary photoreaction of retinal.

  18. Synthesis, z-scan and degenerate four wave mixing characterization of certain functionalized photosensitive polyesters containing ortho-hydroxyazo chromophores

    Science.gov (United States)

    Jayakrishnan, K.; Siji Narendran, N. K.; Sreejith, P.; Joseph, Antony; Chandrasekharan, K.; Purushothaman, E.

    2015-07-01

    The preparation and NLO characterization of photosensitive polyesters containing azoaromatic residues in the molecular backbone, functionalized with orthohydroxy chromophores is presented. Samples were studied for its UV-vis absorption, FT-IR and intensity dependent nonlinear absorption properties. Nonlinear characterization was carried out with z-scan using frequency doubled, Q-switched Nd:YAG laser operating at 532 nm. The closed aperture z-scan spectra reveal the self defocusing effects of the samples with negative nonlinearity coefficient (n2) showing values as high as -1.28 × 10-10 (esu) for certain samples and the corresponding third order susceptibility coefficient of the order of 29.9 × 10-12 (esu). Degenerate four wave mixing technique was employed to substantiate the findings. The numerical fits show that the molecules exhibit reverse saturable absorption. A study of beam fluence dependence of nonlinear absorption coefficient (βeff) has been presented. All phenomena indicate that molecules are reverse saturable absorbers whose optical limiting property gets enhanced with increasing conjugation length.

  19. Phytochrome as molecular machine: revealing chromophore action during the Pfr --> Pr photoconversion by magic-angle spinning NMR spectroscopy.

    Science.gov (United States)

    Rohmer, Thierry; Lang, Christina; Bongards, Christian; Gupta, Karthick Babu Sai Sankar; Neugebauer, Johannes; Hughes, Jon; Gärtner, Wolfgang; Matysik, Jörg

    2010-03-31

    The cyanobacterial phytochrome Cph1 can be photoconverted between two thermally stable states, Pr and Pfr. The photochemically induced Pfr --> Pr back-reaction has been followed at low temperature by magic-angle spinning (MAS) NMR spectroscopy, allowing two intermediates, Lumi-F and Meta-F, to be trapped. Employing uniformly (13)C- and (15)N-labeled open-chain tetrapyrrole chromophores, all four states-Pfr, Lumi-F, Meta-F, and Pr-have been structurally characterized. In the first step, the double bond photoisomerization forming Lumi-F occurs. The second step, the transformation to Meta-F, is driven by the release of the mechanical tension. This process leads to the break of the hydrogen bond of the ring D nitrogen to Asp-207 and triggers signaling. The third step is protonically driven allowing the hydrogen-bonding interaction of the ring D nitrogen to be restored. Compared to the forward reaction, the order of events is changed, probably caused by the different properties of the hydrogen bonding partners of N24, leading to the directionality of the photocycle.

  20. Absorption features of chromophoric dissolved organic matter (CDOM and tracing implication for dissolved organic carbon (DOC in Changjiang Estuary, China

    Directory of Open Access Journals (Sweden)

    X. Y. Zhang

    2013-07-01

    Full Text Available Chromophoric dissolved organic matter (CDOM represents the light absorbing fraction of dissolved organic carbon (DOC. Studies have shown that the optical properties of CDOM can be used to infer the distribution and diffusion characteristics of DOC in the estuary and coastal zone. The inversion of DOC concentrations from remote sensing has been implemented in certain regions. In this study we investigate the potential of tracing DOC from CDOM by the measurement of DOC, absorption spectrum of CDOM, Chla concentration, suspended sediment (SS, and salinity from cruises in different seasons around the Changjiang estuary. Our results show that around the Changjiang estuary the absorption coefficients of CDOM in general have the similar spatial and temporal characteristics as that of DOC, but the strength of the correlation between CDOM and DOC varies locally and seasonally. The input of pollutants from outside the estuary, the bloom of phytoplankton in spring, re-suspension of deposited sediment, and light bleaching all contribute to the local and seasonal variation of the correlation between DOC and CDOM. An inversion model for the determination of DOC from CDOM is established, but the stability of model parameters and its application in different environments need further study. We find that relative to the absorption coefficient of CDOM, the fitted parameters of the absorption spectrum of DOM are better indictors for the composition of DOC. In addition, it is found that the terrestrial input of DOC to Changjiang estuary is a typical two-stage dilution process instead of a linear diffusion process.

  1. Novel D-π-A-π-D type organic chromophores for second harmonic generation and multi-photon absorption applications

    Science.gov (United States)

    Aditya, Pusala; Kumar, Hari; Kumar, Sunil; Rajashekar, Muralikrishna, M.; Muthukumar, V. Sai; Kumar, B. Siva; Sai, S. Siva Sankara; Rao, G. Nageshwar

    2013-06-01

    We report here the optical and non-linear optical properties of six different novel bis-chalcones of D-π-A-π-D derivatives of diarylideneacetone (DBA). These derivatives have been synthesized by Claisen-Schmidt condensation reaction and were well characterized by using FTIR, 1HNMR, 13CNMR, UV-Visible absorption and mass spectroscopic techniques. The optical bandgap for each of the DBA derivatives were determined both experimentally (UV-Visible spectra & Tauc Plot) and theoretically by ab intio DFT calculations using SIESTA software package. They were found to be in close agreement with each other. The Second Harmonic Generation from these organic chromophores were studied by standard Kurtz and Perry Powder SHG method at 1064 nm. They were found to have superior SHG conversion efficiency when compared to urea (standard sample). Further, we investigated the Multi-Photon absorption properties were using conventional open aperture z-scan technique. These DBA derivatives exhibited strong two photon absorption in the order of 1e-11m/W. Hence, these are potential candidate for various photonic applications like optical power limiting, photonic switching and frequency conversion.

  2. 5,6-Dihydroxyindole oxidation in phosphate buffer/polyvinyl alcohol: a new model system for studies of visible chromophore development in synthetic eumelanin polymers.

    Science.gov (United States)

    Pezzella, Alessandro; Ambrogi, Veronica; Arzillo, Marianna; Napolitano, Alessandra; Carfagna, Cosimo; d'Ischia, Marco

    2010-01-01

    The determinants of the broadband absorption spectrum of eumelanins are still largely unknown. Herein we report a novel approach to investigate eumelanin chromophore which is based on the biomimetic oxidation of the key monomer precursor, 5,6-dihydroxyindole (DHI, 1), with peroxidase/hydrogen peroxide in phosphate buffer, pH 7, containing 1-5% polyvinylalcohol (PVA, 27 000 Da). This approach relies on the discovery that as low as 1% PVA can prevent precipitation of the growing melanin polymer thus allowing investigation of the chromophoric phases accompanying oxidation of DHI without confounding scattering effects. Spectrophotometric monitoring showed the initial development of a band around 530 nm persisting for about 1 h before gradually changing into the typical broadband spectrum of eumelanin. Reductive treatment caused a significant absorbance decrease in the visible region without affecting an absorption band around 320 nm. Initial product analysis indicated an altered formation ratio of 2,4'-biindolyl (2) and 2,7'-biindolyl (3) relative to control experiments. Overall, these results demonstrate for the first time that the development in solution of visible chromophores since the early oligomer stages is independent of strong aggregation/precipitation phenomena.

  3. A highly efficient synthesis of itraconazole intermediates and their analogues

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, Chong Il; Myoung, Young Chan; Choi, Ha Young; Kim, Seung Jin [Agency for Technology and Standards, Gwacheon (Korea, Republic of)

    1999-12-01

    Itraconazole is an important drug for oral treatment of histoplasmosis and blastomycosis. Itraconazole has been the targets of many synthetic efforts due to their diverse antifungal activities. In this study, an efficient synthetic route for Itraconazole intermediates has been developed using new procedures. Also, Itraconazole analogues introducing 2- and 3-methoxy group instead of Itraconazole intermediates with 4-methoxy group were synthesized.

  4. Vitamin D analogues: Potential use in cancer treatment.

    Science.gov (United States)

    Duffy, Michael J; Murray, Alyson; Synnott, Naoise C; O'Donovan, Norma; Crown, John

    2017-04-01

    The vitamin D receptor (VDR) is a member of the thyroid-steroid family of nuclear transcription factors. Following binding of the active form of vitamin D, i.e., 1,25(OH)2D3 (also known as calcitriol) and interaction with co-activators and co-repressors, VDR regulates the expression of several different genes. Although relatively little work has been carried out on VDR in human cancers, several epidemiological studies suggest that low circulating levels of vitamin D are associated with both an increased risk of developing specific cancer types and poor outcome in patients with specific diagnosed cancers. These associations apply especially in colorectal and breast cancer. Consistent with these findings, calcitriol as well as several of its synthetic analogues have been shown to inhibit tumor cell growth in vitro and in diverse animal model systems. Indeed, some of these vitamin D analogues with low calcemic inducing activity (e.g., EB1089, inecalcitol, paricalcitol) have progressed to clinical trials in patients with cancer. Preliminary results from these trials suggest that these vitamin D analogues have minimal toxicity, but clear evidence of efficacy remains to be shown. Although evidence of efficacy for mono-treatment with vitamin D analogues is currently lacking, several studies have reported that supplementation with calcitriol or the presence of high endogenous circulating levels of vitamin D enhances response to standard therapies.

  5. Block-level Bayesian diagnosis of analogue electronic circuits

    NARCIS (Netherlands)

    Krishnan, S.; Doornbos, K.D.; Brand, R.; Kerkhoff, H.G.

    2010-01-01

    Daily experience with product designers, test and diagnosis engineers it is realized that the depth of interaction among them, ought be high for sucessfull diagnosis of analogue circuits. With this knowledge in mind, a responsibility was undertaken to choose a popular diagnostic method and define a

  6. Synthesis of pyrophosphonic acid analogues of farnesyl pyrophosphate

    NARCIS (Netherlands)

    Valentijn, A.R.P.M.; Berg, O. van den; Marel, G.A. van der; Cohen, L.H.; Boom, J.H. van

    1995-01-01

    The synthesis of four new analogues (i.e. 3-6) of farnesyl pyrophosphate (FPP), which may function as inhibitor of squalene synthase, is described. Compounds 3 and 4 were readily accessible by reaction of farnesal with diethyl phosphite or dimethyl lithiomethylphosphonate, respectively, followed by

  7. Design and Synthesis of Muramyl Dipeptide Cyclic Analogue

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A new conformationally restricted cyclic analogue of muramyl dipeptide was designed and manually synthesized by our "Meshed-Bag Gathered-Bunch" method with a combination of Fmoc, allyl and N-1-(4,4-dimethyl-2,6-dioxocyclo-hexylidene)ethyl chemical protection strategy.

  8. Reproducibility along a 10 cm vertical visual analogue scale.

    OpenAIRE

    Dixon, J. S.; Bird, H A

    1981-01-01

    Reproducibility along a vertical 10 cm visual analogue scale (VAS) was investigated. Eight normal volunteers attempted to duplicate a set of marked VAS. There was a tendency to estimate too high on the scale, and reproducibility was found to be variable along its length. This indicates that the error involved in the use of VASs is even more complex than previously thought.

  9. Click-based synthesis and proteomic profiling of lipstatin analogues

    OpenAIRE

    Ngai, Mun H.; Yang, Peng-Yu; Liu, Kai; Shen, Yuan; Wenk, Markus R; Yao, Shao Q.; Lear, Martin J.

    2010-01-01

    Using click chemistry to enable both structural diversity and proteome profiling within a natural product derived library, two out of nineteen lipstatin analogues showed similar activity to Orlistat against fatty acid synthase (FAS), but with an improved ability to induce tumour cell death.

  10. Solution-phase synthesis of a muramyl dipeptide analogue MDA

    Institute of Scientific and Technical Information of China (English)

    Nan Zhao; Yao Ma; Gang Liu

    2011-01-01

    The solution-phase synthesis of a muramyl dipeptide (MDP) analogue of Nα- [4-chlorocinnamoyl-L-alanyl-D-isoglutaminyl]-L-lysine (MDA, 2) is reported that possesses the features of easy feasibility, safety and low cost in large scale of synthesis.

  11. Direct neutron decay of analogue resonances in 105Rh

    Institute of Scientific and Technical Information of China (English)

    Hu Bi-Tao; P.P.Zarubin; U.U.Juravlev

    2006-01-01

    A new method, while takes into account the contribution of direct neutron decay of analogue resonances to the isomeric ratio resulting from (p,n) reaction, is used to analyse the published experimental data for the reaction 104Ru(p,n)104Rh and also estimate a minimum probability of direct decay.

  12. A Macroscopic Analogue of the Nuclear Pairing Potential

    Science.gov (United States)

    Dunlap, Richard A.

    2013-01-01

    A macroscopic system involving permanent magnets is used as an analogue to nucleons in a nucleus to illustrate the significance of the pairing interaction. This illustrates that the view of the total nuclear energy based only on the nucleon occupancy of the energy levels can yield erroneous results and it is only when the pairing interaction is…

  13. Nucleic Acid Analogue Induced Transcription of Double Stranded DNA

    DEFF Research Database (Denmark)

    1998-01-01

    RNA is transcribed from a double stranded DNA template by forming a complex by hybridizing to the template at a desired transcription initiation site one or more oligonucleic acid analogues of the PNA type capable of forming a transcription initiation site with the DNA and exposing the complex...

  14. An Analysis of an Autoclitic Analogue in Pigeons

    Science.gov (United States)

    Kuroda, Toshikazu; Lattal, Kennon A.; García-Penagos, Andrés

    2014-01-01

    Using a conditional discrimination procedure, pigeons were exposed to a nonverbal analogue of qualifying autoclitics such as "definitely" and "maybe." It has been suggested that these autoclitics are similar to tacts except that they are under the control of private discriminative stimuli. Instead of the conventional assumption…

  15. Are Structural Analogues to Bisphenol A Safe Alternatives?

    DEFF Research Database (Denmark)

    Rosenmai, Anna Kjerstine; Dybdahl, Marianne; Pedersen, Mikael;

    2014-01-01

    Background: Bisphenol A (BPA) is a chemical with widespread human exposure suspected of causing low-dose effects. Thus, a need for developing alternatives to BPA exists. Structural analogues of BPA have already been detected in foods and humans. Due to the structural analogy of the alternatives...

  16. Treatment with insulin (analogues) and breast cancer risk in diabetics

    DEFF Research Database (Denmark)

    Bronsveld, Heleen K; Ter Braak, Bas; Karlstad, Øystein

    2015-01-01

    : A systematic literature search was performed on breast cell-line, animal and human studies using the key words 'insulin analogue' and 'breast neoplasia' in MEDLINE at PubMed, EMBASE, and ISI Web of Science databases. A quantitative and qualitative review was performed on the epidemiological data; due...

  17. Synthesis and Antioxidant Properties of Novel Silybin Analogues

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Eight novel silybin analogues (7a-h) were synthesized and their antioxidant properties including the capability of scavenging superoxide anion free radicals and the inhibitory effect on DPPH free radicals were determined. Several synthetic compounds showed comparable antioxidative effect to that of quercetin.

  18. The influence of no fault found in analogue CMOS circuits

    NARCIS (Netherlands)

    Wan, Jinbo; Kerkhoff, Hans G.

    2014-01-01

    The most difficult fault category in electronic systems is the “No Fault Found” (NFF). It is considered to be the most costly fault category in, for instance, avionics. The relatively few papers in this area rarely deal with analogue integrated systems. In this paper a simple simulation model has be

  19. Aromaticity in Polyacene Analogues of Inorganic Ring Compounds

    CERN Document Server

    Chattaraj, P K; Chattaraj, Pratim Kumar; Roy, Debesh Ranjan

    2006-01-01

    The aromaticity in the polyacene analogues of several inorganic ring compounds (BN-acenes, CN-acenes, BO-acenes and Na6-acenes) is reported here for the first time. Conceptual density functional theory based reactivity descriptors and the nucleus independent chemical shift (NICS) values are used in this analysis.

  20. Rubrene analogues with the aggregation-induced emission enhancement behaviour

    DEFF Research Database (Denmark)

    Zhang, Xiaoxu; Sørensen, Jakob Kryger; Fu, Xiaowei;

    2014-01-01

    In the light of the principle of aggregation-induced emission enhancement (AIEE), the rubrene analogue with orange light-emitting properties is designed and synthesized by substituting the phenyl side groups of rubrene with thienyl groups. To the best of our knowledge, this is the first report...

  1. Design and Synthesis of Muramyl Dipeptide Cyclic Analogue

    Institute of Scientific and Technical Information of China (English)

    SuoDeZHANG; GangLIU; 等

    2002-01-01

    A new conformationalloy restricted cyclic analogue of muramyl dipeptide was designed and manually synthesized by our “Meshed-Bag Gathered-Bunch” method with a combination of Fmoc,ally and N-1-(4,4-dimethyl-2,6-dioxocyclo-hexylidene) ethyl chemical protection strategy.

  2. Synthesis, DNA interaction and antimicrobial activities of three rimantadine analogues

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Bing-Mi; Zhang, Jun [Department of Pharmacy, Liaoning University, Shenyang 110036 (China); Wang, Xin, E-mail: wangxinlnu@163.com [Department of Pharmacy, Liaoning University, Shenyang 110036 (China); Zhang, Li-Ping; Liu, Yang [Department of Pharmacy, Liaoning University, Shenyang 110036 (China); Niu, Hua-Ying [Jinan Dachpharm Development Co., Ltd., Jinan 250100 (China); Liu, Bin, E-mail: liubinzehao@163.com [Department of Pharmacy, Liaoning University, Shenyang 110036 (China)

    2015-03-15

    The interactions of three rimantadine analogues (RAs) with calf thymus deoxyribonucleic acid (ct-DNA) in buffer solution (pH 7.4) were investigated using berberine (BR) as a probe by various methods. Fluorescence studies revealed that the RAs interacted with DNA in vitro and the quenchings were all static. Furthermore, the binding modes of these compounds to DNA were disclosed as groove binding supported by absorption spectroscopy, viscosity measurement and denatured DNA experiment. The antimicrobial activities of the RAs were also evaluated in Staphylococcus aureus and Escherichia coli, and they all exhibited good bacteriostasic effects. The results might provide an important reference for investigation of the molecular mechanism associated with the DNA binding of the RAs. - Highlights: • Three rimantadine analogues were synthesized. • The RAs effectively quenched the intrinsic fluorescence of DNA via a static combination. • These analogues can bind to DNA via groove binding mode. • The antimicrobial activities of three analogues were also evaluated by the disk diffusion method.

  3. Combined treatment of somatostatin analogues with pegvisomant in acromegaly

    NARCIS (Netherlands)

    S.E. Franck; A. Muhammad; A-J. van der Lely (Aart-Jan); S.J.C.M.M. Neggers (Bas)

    2016-01-01

    textabstractTreatment of acromegaly with monotherapy long-acting somatostatin analogues (LA-SSA) as primary treatment or after neurosurgery can only achieve complete normalization of insulin-like growth factor I (IGF-I) in roughly 40 % of patients. Recently, one of the acromegaly consensus groups ha

  4. Concise synthesis of new bridged-nicotine analogues

    DEFF Research Database (Denmark)

    Crestey, François; Hooyberghs, Geert; Kristensen, Jesper Langgaard

    2012-01-01

    This study describes a very efficient strategy for the synthesis of two new bridged-nicotine analogues. Starting from either 4- or 3-chloropyridine the desired tricyclic ring systems are accessed in just three steps in 23% and 40% overall yield, respectively....

  5. Cytotoxicity of natural ginseng glycosides and semisynthetic analogues

    NARCIS (Netherlands)

    Atopkina, LN; Malinovskaya, GV; Elyakov, GB; Uvarova, NI; Woerdenbag, HJ; Koulman, A; Potier, P

    1999-01-01

    The cytotoxicity of natural glycosides from Ginseng, semisynthetic analogues and related triterpenes of the dammarane series, isolated from the leaves of the Far-East species of the genus Betula was studied in order to elucidate structure-activity relationships. Some of the compounds studied were ac

  6. Analogue Electrical Circuit for Simulation of the Duffing-Holmes Equation

    DEFF Research Database (Denmark)

    Tamaseviciute, E.; Tamasevicius, A.; Mykolaitis, G.;

    2008-01-01

    An extremely simple second order analogue electrical circuit for simulating the two-well Duffing-Holmes mathematical oscillator is described. Numerical results and analogue electrical simulations are illustrated with the snapshots of chaotic waveforms, phase portraits (Lissajous figures...

  7. Synthesis and Characterization of the Tetrazole Analogues of α-Amino Acids

    Institute of Scientific and Technical Information of China (English)

    Yan Min HUO; Gen Hu LEI; Yin Mao WEI; Xiao Hui ZHENG

    2006-01-01

    The tetrazole analogues have been synthesized from fluorenylmethoxycarbonyl (Fmoc)protected amino acids by three steps. The structures of the analogues were characterized by HPLC-MS, 1H NMR and 13C NMR.

  8. Non-robust numerical simulations of analogue extension experiments

    Science.gov (United States)

    Naliboff, John; Buiter, Susanne

    2016-04-01

    Numerical and analogue models of lithospheric deformation provide significant insight into the tectonic processes that lead to specific structural and geophysical observations. As these two types of models contain distinct assumptions and tradeoffs, investigations drawing conclusions from both can reveal robust links between first-order processes and observations. Recent studies have focused on detailed comparisons between numerical and analogue experiments in both compressional and extensional tectonics, sometimes involving multiple lithospheric deformation codes and analogue setups. While such comparisons often show good agreement on first-order deformation styles, results frequently diverge on second-order structures, such as shear zone dip angles or spacing, and in certain cases even on first-order structures. Here, we present finite-element experiments that are designed to directly reproduce analogue "sandbox" extension experiments at the cm-scale. We use material properties and boundary conditions that are directly taken from analogue experiments and use a Drucker-Prager failure model to simulate shear zone formation in sand. We find that our numerical experiments are highly sensitive to numerous numerical parameters. For example, changes to the numerical resolution, velocity convergence parameters and elemental viscosity averaging commonly produce significant changes in first- and second-order structures accommodating deformation. The sensitivity of the numerical simulations to small parameter changes likely reflects a number of factors, including, but not limited to, high angles of internal friction assigned to sand, complex, unknown interactions between the brittle sand (used as an upper crust equivalent) and viscous silicone (lower crust), highly non-linear strain weakening processes and poor constraints on the cohesion of sand. Our numerical-analogue comparison is hampered by (a) an incomplete knowledge of the fine details of sand failure and sand

  9. Directed evolution of the substrate specificity of biotin ligase.

    Science.gov (United States)

    Lu, Wei-Cheng; Levy, Matthew; Kincaid, Rodney; Ellington, Andrew D

    2014-06-01

    We have developed selection scheme for directing the evolution of Escherichia coli biotin protein ligase (BPL) via in vitro compartmentalization, and have used this scheme to alter the substrate specificity of the ligase towards the utilization of the biotin analogue desthiobiotin. In this scheme, a peptide substrate (BAP) was conjugated to a DNA library encoding BirA, emulsified such that there was a single template per compartment, and protein variants were transcribed and translated in vitro. Those variants that could efficiently desthiobiotinylate their corresponding peptide:DNA conjugate were subsequently captured and amplified. Following just six rounds of selection and amplification several variants that demonstrated higher activity with desthiobiotin were identified. The best variants from Round 6, BirA6-40 and BirA6-47 , showed 17-fold and 10-fold higher activity, respectively, their abilities to use desthiobiotin as a substrate. While selected enzymes contained a number of substitutions, a single mutation, M157T, proved sufficient to provide much greater activity with desthiobiotin. Further characterization of BirA6-40 and the single substitution variant BirAM157T revealed that they had twoto threefold higher kcat values for desthiobiotin. These variants had also lost much of their ability to utilize biotin, resulting in orthogonal enzymes that in conjunction with streptavidin variants that can utilize desthiobiotin may prove to be of great use in developing additional, robust conjugation handles for a variety of biological and biotechnological applications.

  10. Immobilization of Lipid Substrates: Application on Phospholipase A2 Determination.

    Science.gov (United States)

    Karkabounas, Athanassios; Georgiadou, Dimitra G; Argitis, Panagiotis; Psycharis, Vassilios; Nakos, George; Kosmas, Agni M; Lekka, Marilena E

    2015-12-01

    The purpose of the study was to assess a fluorimetric assay for the determination of total phospholipase A(2) (PLA(2)) activity in biological samples introducing the innovation of immobilized substrates on crosslinked polymeric membranes. The immobilized C(12)-NBD-PtdCho, a fluorescent analogue of phosphatidylcholine, exhibited excellent stability for 3 months at 4 °C and was not desorbed in the aqueous reaction mixture during analysis. The limit of detection was 0.5 pmol FA (0.2 pg) and the linear part of the response curve extended from 1 up to 190 nmol FA/h/mL sample. The intra- and inter-day relative standard deviations (%RSD), were ≤6 and ≤9 %, respectively. Statistical comparison with other fluorescent methods showed excellent correlation and agreement. Semiempirical calculations showed a fair amount of electrostatic interaction between the NBD-labeled substrate and the crosslinked polyvinyl alcohol with the styryl pyridinium residues (PVA-SbQ) material, from the plane of which, the sn-2 acyl chain of the phospholipid stands out and is accessible by PLA(2). Atomic Force Microscopy revealed morphological alterations of the immobilized substrate after the reaction with PLA(2). Mass spectrometry showed that only C(12)-NBD-FA, the PLA(2 )hydrolysis product, was detected in the reaction mixture, indicating that PLA(2) recognizes PVA-SbQ/C(12)-NBD-PtdCho as a surface to perform catalysis.

  11. Bicyclic proline analogues as organocatalysts for stereoselective aldol reactions: an in silico DFT study.

    Science.gov (United States)

    Shinisha, C B; Sunoj, Raghavan B

    2007-04-21

    Density functional theory has been employed in investigating the efficiency of a series of bicyclic analogues of proline as stereoselective organocatalysts for the aldol reaction. Three classes of conformationally restricted proline analogues, as part of either a [2.2.1] or [2.1.1] bicyclic framework, have been studied. Transition states for the stereoselective C-C bond formation between enamines derived from [2.2.1] and [2.1.1] bicyclic amino acids and p-nitrobenzaldehyde, leading to enantiomeric products, have been identified. Analysis of the transition state geometries revealed that the structural rigidity of catalysts, improved transition state organization as well as other weak interactions influence the relative stabilities of diastereomeric transition states and help contribute to the overall stereoselectivity in the aldol reaction. These bicyclic catalysts are predicted to be substantially more effective in improving the enantiomeric excess than the widely used organocatalyst proline. Enantiomeric excesses in the range 82-95% are predicted for these bicyclic catalysts when a sterically unbiased substrate such as p-nitrobenzaldehyde is employed for the asymmetric aldol reaction. More interestingly, introduction of substituents, as simple as a methyl group, at the ortho position of the aryl aldehyde bring about an increase in the enantiomeric excess to values greater than 98%. The reasons behind the vital energy separation between diastereomeric transition states has been rationalized with the help of a number of weak interactions such as intramolecular hydrogen bonding and Coulombic interactions operating on the transition states. These predictions could have wider implications for the rational design of improved organocatalysts for stereoselective carbon-carbon bond-forming reactions.

  12. Teratogenic potency of valproate analogues evaluated by quantitative estimation of cellular morphology in vitro.

    Science.gov (United States)

    Berezin, V; Kawa, A; Bojic, U; Foley, A; Nau, H; Regan, C; Edvardsen, K; Bock, E

    1996-10-01

    To develop a simple prescreening system for teratogenicity testing, a novel in vitro assay was established using computer assisted microscopy allowing automatic delineation of contours of stained cells and thereby quantitative determination of cellular morphology. The effects of valproic acid (VPA) and analogues with high as well as low teratogenic activities-(as previously determined in vivo)-were used as probes for study of the discrimination power of the in vitro model. VPA, a teratogenic analogue (+/-)-4-en-VPA, and a non-teratogenic analogue (E)-2-en-VPA, as well as the purified (S)- and (R)-enantiomers of 4-yn-VPA (teratogenic and non-teratogenic, respectively), were tested for their effects on cellular morphology of cloned mouse fibroblastoid L-cell lines, neuroblastoma N2a cells, and rat glioma BT4Cn cells, and were found to induce varying increases in cellular area: Furthermore, it was demonstrated that under the chosen conditions the increase in area correlated statistically significantly with the teratogenic potency of the employed compounds. Setting the cellular area of mouse L-cells to 100% under control conditions, the most pronounced effect was observed for (S)-4-yn-VPA (211%, P = < 0.001) followed by VPA (186%, P < 0.001), 4-en-VPA (169%, P < 0.001) and non-teratogenic 2-en-VPA (137%, P < 0.005) and (R)-4-yn-VPA (105%). This effect was independent of the choice of substrata, since it was observed on L-cells grown on plastic, fibronectin, laminin and Matrigel. However, when VPA-treated cells were exposed to an arginyl-glycyl-aspartate (RGD)-containing peptide to test whether VPA treatment was able to modulate RGD-dependent integrin interactions with components of the extracellular matrix, hardly any effect could be observed, whereas control cells readily detached from the substratum, indicating a changed substrate adhesion of the VPA-treated cells. The data thus indicate that measurement of cellular area may serve as a simple in vitro test in the

  13. Substrate Oxidation by Indoleamine 2,3-Dioxygenase: EVIDENCE FOR A COMMON REACTION MECHANISM.

    Science.gov (United States)

    Booth, Elizabeth S; Basran, Jaswir; Lee, Michael; Handa, Sandeep; Raven, Emma L

    2015-12-25

    The kynurenine pathway is the major route of L-tryptophan (L-Trp) catabolism in biology, leading ultimately to the formation of NAD(+). The initial and rate-limiting step of the kynurenine pathway involves oxidation of L-Trp to N-formylkynurenine. This is an O2-dependent process and catalyzed by indoleamine 2,3-dioxygenase and tryptophan 2,3-dioxygenase. More than 60 years after these dioxygenase enzymes were first isolated (Kotake, Y., and Masayama, I. (1936) Z. Physiol. Chem. 243, 237-244), the mechanism of the reaction is not established. We examined the mechanism of substrate oxidation for a series of substituted tryptophan analogues by indoleamine 2,3-dioxygenase. We observed formation of a transient intermediate, assigned as a Compound II (ferryl) species, during oxidation of L-Trp, 1-methyl-L-Trp, and a number of other substrate analogues. The data are consistent with a common reaction mechanism for indoleamine 2,3-dioxygenase-catalyzed oxidation of tryptophan and other tryptophan analogues.

  14. Rapid and direct spectrophotometric method for kinetics studies and routine assay of peroxidase based on aniline diazo substrates.

    Science.gov (United States)

    Mirazizi, Fatemeh; Bahrami, Azita; Haghbeen, Kamahldin; Shahbani Zahiri, Hossein; Bakavoli, Mehdi; Legge, Raymond L

    2016-12-01

    Peroxidases are ubiquitous enzymes that play an important role in living organisms. Current spectrophotometrically based peroxidase assay methods are based on the production of chromophoric substances at the end of the enzymatic reaction. The ambiguity regarding the formation and identity of the final chromophoric product and its possible reactions with other molecules have raised concerns about the accuracy of these methods. This can be of serious concern in inhibition studies. A novel spectrophotometric assay for peroxidase, based on direct measurement of a soluble aniline diazo substrate, is introduced. In addition to the routine assays, this method can be used in comprehensive kinetics studies. 4-[(4-Sulfophenyl)azo]aniline (λmax = 390 nm, ɛ = 32 880 M(-1) cm(-1) at pH 4.5 to 9) was introduced for routine assay of peroxidase. This compound is commercially available and is indexed as a food dye. Using this method, a detection limit of 0.05 nmol mL(-1) was achieved for peroxidase.

  15. Alligator Rivers Analogue project. Application of scenario development method in evaluation of the Koongarra Analogue. Final Report - Volume 16

    Energy Technology Data Exchange (ETDEWEB)

    Skagius, K. [Kemakta Consultants co., Stockholm (Sweden); Wingefors, S. [Swedish Nuclear Power Inspectorate, Stockholm (Sweden)

    1992-12-31

    The study of natural analogues has been established as one of the most important methods for validation of concepts and models applied for the assessment of long-term performance of repositories for nuclear waste. The objectives of such studies range from detailed investigations of processes and features on a small scale to attempts of explaining the evolution of whole sites. For studies of specific processes it may well be as important to consider the larger scale settings as boundary conditions. This appreciation of context and an integrated view may be as important for evaluation of most natural analogues as for performance assessments. This is more evident the more the evaluation depends on a knowledge about the evolution of the natural analogue. The attempted formulation of scenarios of the Koongarra Analogue has been based on the external conditions and external features. A rapid weathering of the host rock, i.e. the chlorite schist, is assumed to have started around the onset of the Pleistocene Ice Age (ca 1.6 Ma BP). The eventual oxidation and mobilization of the uranium ore could then have occurred under unsaturated or saturated conditions. This leads to the following major scenarios: (1) Uranyl Phosphates formed under unsaturated conditions, with a periodical evolution of the dispersion fan in conjunction with alternating dry (glacial) and wet (interglacial) periods during the Pleistocene Ice Age; (2) Uranyl Phosphates formed under unsaturated conditions as a single event, taking place either early or late during the Pleistocene Ice Age; (3)Uranyl Phosphates formed under saturated conditions, in conjunction with periods of higher and lower flow due to the climatic cycling. Although the original objectives may not have been fully achieved, this work is believed to contribute to a better understanding of the Koongarra Analogue as well as to give a basis for further scenario work

  16. Design, synthesis, and biological evaluation of substrate-competitive inhibitors of C-terminal Binding Protein (CtBP).

    Science.gov (United States)

    Korwar, Sudha; Morris, Benjamin L; Parikh, Hardik I; Coover, Robert A; Doughty, Tyler W; Love, Ian M; Hilbert, Brendan J; Royer, William E; Kellogg, Glen E; Grossman, Steven R; Ellis, Keith C

    2016-06-15

    C-terminal Binding Protein (CtBP) is a transcriptional co-regulator that downregulates the expression of many tumor-suppressor genes. Utilizing a crystal structure of CtBP with its substrate 4-methylthio-2-oxobutyric acid (MTOB) and NAD(+) as a guide, we have designed, synthesized, and tested a series of small molecule inhibitors of CtBP. From our first round of compounds, we identified 2-(hydroxyimino)-3-phenylpropanoic acid as a potent CtBP inhibitor (IC50=0.24μM). A structure-activity relationship study of this compound further identified the 4-chloro- (IC50=0.18μM) and 3-chloro- (IC50=0.17μM) analogues as additional potent CtBP inhibitors. Evaluation of the hydroxyimine analogues in a short-term cell growth/viability assay showed that the 4-chloro- and 3-chloro-analogues are 2-fold and 4-fold more potent, respectively, than the MTOB control. A functional cellular assay using a CtBP-specific transcriptional readout revealed that the 4-chloro- and 3-chloro-hydroxyimine analogues were able to block CtBP transcriptional repression activity. This data suggests that substrate-competitive inhibition of CtBP dehydrogenase activity is a potential mechanism to reactivate tumor-suppressor gene expression as a therapeutic strategy for cancer.

  17. Synthesis and Properties of Novel Organic Nonlinear Optical Chromophores Containing Furan Conjugating Bridges%含呋喃共轭桥有机非线性光学生色团的合成及性能研究

    Institute of Scientific and Technical Information of China (English)

    唐翔; 唐先忠; 游英才; 任立轲; 王洋; 严立京

    2012-01-01

    the non-furyl corresponding structure DCDHF-2-V. Density functional theory (DFT) B3LYP/6-31G method was used to optimize the structures and calculate the static hyperpolarizability (β0). The β0 value of EFFC was calculated as large as 6.5 × 10-28 esu. It was larger than the corresponding chromophores with dimethylamine donors. The chromophore was mixed into polysulfone (PSU) with the weight ratio of 18%. The mixture was dissolved in cyclohexanone and the films were spun onto ITO/glass substrates. The chromophores in the polymer matrix were aligned into a noncentrosymmetrical orientation by corona poling technique. The poling was performed in a wire-to-plane geometry under in-situ conditions. The discharging wire to plane distance was 1 cm. 12 kV of corona voltage was applied and kept for 15 min at 100 ℃. The film was cooled down to the room temperature at applied electric field maintaining a constant current. The second-order nonlinear coefficient r33 value reached to 80 pm/V at 1064 nm was measured by second harmonic generation method.

  18. Deposition of latex colloids at rough mineral surfaces: an analogue study using nanopatterned surfaces.

    Science.gov (United States)

    Krishna Darbha, Gopala; Fischer, Cornelius; Michler, Alex; Luetzenkirchen, Johannes; Schäfer, Thorsten; Heberling, Frank; Schild, Dieter

    2012-04-24

    Deposition of latex colloids on a structured silicon surface was investigated. The surface with well-defined roughness and topography pattern served as an analogue for rough mineral surfaces with half-pores in the submicrometer size. The silicon topography consists of a regular pit pattern (pit diameter = 400 nm, pit spacing = 400 nm, pit depth = 100 nm). Effects of hydrodynamics and colloidal interactions in transport and deposition dynamics of a colloidal suspension were investigated in a parallel plate flow chamber. The experiments were conducted at pH ∼ 5.5 under both favorable and unfavorable adsorption conditions using carboxylate functionalized colloids to study the impact of surface topography on particle retention. Vertical scanning interferometry (VSI) was applied for both surface topography characterization and the quantification of colloidal retention over large fields of view. The influence of particle diameter variation (d = 0.3-2 μm) on retention of monodisperse as well as polydisperse suspensions was studied as a function of flow velocity. Despite electrostatically unfavorable conditions, at all flow velocities, an increased retention of colloids was observed at the rough surface compared to a smooth surface without surface pattern. The impact of surface roughness on retention was found to be more significant for smaller colloids (d = 0.3, 0.43 vs. 1, 2 μm). From smooth to rough surfaces, the deposition rate of 0.3 and 0.43 μm colloids increased by a factor of ∼2.7 compared to a factor of 1.2 or 1.8 for 1 and 2 μm colloids, respectively. For a substrate herein, with constant surface topography, the ratio between substrate roughness and radius of colloid, Rq/rc, determined the deposition efficiency. As Rq/rc increased, particle-substrate overall DLVO interaction energy decreased. Larger colloids (1 and 2 μm) beyond a critical velocity (7 × 10(-5) and 3 × 10(-6) m/s) (when drag force exceeds adhesion force) tend to detach from the surface

  19. Studies on singlet oxygen formation and UVA light-mediated photobleaching of the yellow chromophores in human lenses.

    Science.gov (United States)

    Ortwerth, Beryl J; Chemoganskiy, Vitaliy; Olesen, P R

    2002-02-01

    The protein-bound chromophores, which increase with aging in the human lens, act as UVA sensitizers, producing almost exclusively singlet oxygen in vitro. Direct irradiation of whole, aged human lenses with high intensity UVA light (200 mW cm(-2) for 24 hr), however, failed to produce singlet oxygen damage, as evidenced by the lack of either His or Trp photodestruction. Total homogenates of human lenses prepared in a cuvette under air did show destruction of His and Trp residues by UVA light, but no destruction was seen when equivalent homogenates were prepared under argon. These data are consistent with the idea that the low oxygen levels in the lens prevent singlet oxygen damage in vivo.UVA irradiation of aged human lenses in culture caused an extensive photobleaching of the yellow chromophores. A time course indicated that the photobleaching increased with time, with significant color loss apparent after 6 hr. Homogenization of the irradiated and dark control lenses in 6 M guanidine-HCl, followed by determination of the difference spectrum, showed approximately 50% bleaching of compounds with a lambda(max) at 355 nm. Similarly, fluorophores with a lambda(max) for excitation of 355 nm and for emission of 420 nm were 50% destroyed by the UVA light. Similar results were obtained in vitro by the anaerobic irradiation of a sonication-solubilized WI fraction from type II brunescent cataracts and from aged human lenses. In this system, there was an initial bleaching of 15% after 30 min of irradiation, followed by a slow increase over the next 6 hr to a final bleaching of 30%. The addition of 1.0 m M ascorbic acid, but not 1.0 m M glutathione (GSH), increased the photobleaching to 60% under argon, and the loss of ascorbate could be detected under these anaerobic conditions. In the presence of air, UVA light produced no photobleaching, but rather caused a three-fold increase in absorbance at 345 nm, which was prevented by the inclusion of 1.0 m M ascorbic acid and almost

  20. Study of influencing factors to chromophoric dissolved organic matter absorption properties from fluorescence features in Taihu lake in autumn

    Directory of Open Access Journals (Sweden)

    Chuang-Chun Huang

    2013-04-01

    Full Text Available In order to identify the components of chromophoric dissolved organic matter (CDOM, confirm the influence of components to the absorption coefficient of CDOM (aCDOM, and estimate aCDOM from fluorescence spectra, fluorescence and optical measurements of CDOM were carried out in November 2008. The results indicate that, the primary component of CDOM is humic-like. The secondary component is tryptophan-like, which is the product of phytoplankton and aquatic debris rather than the wastewater treatment drainaged from city. In this study, six fluorophores with multiple excitation-emission matrices (EEMs peaks (A, B, C, N, M, T were identified according to the parallel factor analysis (PARAFAC. The average contribution of each component to the CDOM is 19.93, 18.82, 16.88, 16.39, 12.26, and 15.72%, respectively. Red Shifted phenomenon will happen with the increase of fluorescence intensity for ultraviolet and terrestrially humic-like. Conversely, marine humic-like will appear Reverse Red Shifted with the increase of fluorescence intensity. The primary contributor to the shoulder value of CDOM’s absorption coefficient at 275 nm is phytoplankton productivity, followed by marine humic-like. The main contributors to the shoulder shape are UV humic-like and phytoplankton productivity, followed by marine humic-like and tryptophan-like. A strong correlation between CDOM absorption and fluorescence intensity at emission wavelength of 424 nm and excitation wavelength ranging from 280 to 360 nm was found. The absorption coefficient can be retrieved successfully from the same excitation wavelength’s fluorescence intensity by an exponential model.

  1. Synthesis and properties of poly(1-phenyl-1-octyne)s containing stereogenic and chromophoric pendant groups

    Institute of Scientific and Technical Information of China (English)

    LAM; Jacky; W.Y.; JIM; Cathy; K.W.; KWOK; Hoi; Sing

    2009-01-01

    Poly(1-phenyl-1-octyne)s containing different stereogenic and chromophoric pendants {-[(C6H13)C=C(C6H4-p-CO2-R)]n-R=[(1S)-endo]-(-)-borneyl (P3), (1R,2S,5R)-(-)-menthyl (P4),―C6H4-p-(1R,2S,5R)-(-)-menthyl (P5), 2-napthyl (P6), 4-biphenylyl (P7)} have been designed and synthesized. The polymers are prepared in moderate yields by WCl6-Ph4Sn and possess high molecular weights (Mw up to 64000). The structures and properties of the polymers are characterized and evaluated by NMR, TGA, UV, CD, PL, and EL analyses. All the polymers are thermally stable and their temperatures for 5% weight loss locate in the range of 300 to 416℃ under nitrogen. The energy band gaps of all the polymers are ~3.0 eV. Polymers P4 and P5 show CD absorptions associated with the helicity of the polymer segments. Excitation of the THF solutions of P3―P7 by UV irradiation gives strong blue lights of ~485 nm with quantum yields higher than 20%. The thin films of the polymers also emit in the same spectral region, indicative of little aggregation-caused quenching of light emission. Multilayer EL devices with a configuration of ITO/Polymer:PVK/BCP/Alq3/LiF/Al are constructed, which emit blue lights of ~487 nm. The maximum luminance and external quantum efficiency vary with the pendant groups, with P6 exhibiting the highest external quantum efficiency of 0.16%. The spectra stability of the EL devices is outstanding and the EL peak maximum experiences little change with the applied voltage.

  2. Quantum Monte Carlo Treatment of the Charge Transfer and Diradical Electronic Character in a Retinal Chromophore Minimal Model.

    Science.gov (United States)

    Zen, Andrea; Coccia, Emanuele; Gozem, Samer; Olivucci, Massimo; Guidoni, Leonardo

    2015-03-10

    The penta-2,4-dieniminium cation (PSB3) displays similar ground state and first excited state potential energy features as those of the retinal protonated Schiff base (RPSB) chromophore in rhodopsin. Recently, PSB3 has been used to benchmark several electronic structure methods, including highly correlated multireference wave function approaches, highlighting the necessity to accurately describe the electronic correlation in order to obtain reliable properties even along the ground state (thermal) isomerization paths. In this work, we apply two quantum Monte Carlo approaches, the variational Monte Carlo and the lattice regularized diffusion Monte Carlo, to study the energetics and electronic properties of PSB3 along representative minimum energy paths and scans related to its thermal cis–trans isomerization. Quantum Monte Carlo is used in combination with the Jastrow antisymmetrized geminal power ansatz, which guarantees an accurate and balanced description of the static electronic correlation thanks to the multiconfigurational nature of the antisymmetrized geminal power term, and of the dynamical correlation, due to the presence of the Jastrow factor explicitly depending on electron–electron distances. Along the two ground state isomerization minimum energy paths of PSB3, CASSCF calculations yield wave functions having either charge transfer or diradical character in proximity of the two transition state configurations. Here, we observe that at the quantum Monte Carlo level of theory, only the transition state with charge transfer character can be located. The conical intersection, which becomes highly sloped, is observed only if the path connecting the two original CASSCF transition states is extended beyond the diradical one, namely by increasing the bond-length-alternation (BLA). These findings are in good agreement with the results obtained by MRCISD+Q calculations, and they demonstrate the importance of having an accurate description of the static and

  3. Constructing polyatomic potential energy surfaces by interpolating diabatic Hamiltonian matrices with demonstration on green fluorescent protein chromophore.

    Science.gov (United States)

    Park, Jae Woo; Rhee, Young Min

    2014-04-28

    Simulating molecular dynamics directly on quantum chemically obtained potential energy surfaces is generally time consuming. The cost becomes overwhelming especially when excited state dynamics is aimed with multiple electronic states. The interpolated potential has been suggested as a remedy for the cost issue in various simulation settings ranging from fast gas phase reactions of small molecules to relatively slow condensed phase dynamics with complex surrounding. Here, we present a scheme for interpolating multiple electronic surfaces of a relatively large molecule, with an intention of applying it to studying nonadiabatic behaviors. The scheme starts with adiabatic potential information and its diabatic transformation, both of which can be readily obtained, in principle, with quantum chemical calculations. The adiabatic energies and their derivatives on each interpolation center are combined with the derivative coupling vectors to generate the corresponding diabatic Hamiltonian and its derivatives, and they are subsequently adopted in producing a globally defined diabatic Hamiltonian function. As a demonstration, we employ the scheme to build an interpolated Hamiltonian of a relatively large chromophore, para-hydroxybenzylidene imidazolinone, in reference to its all-atom analytical surface model. We show that the interpolation is indeed reliable enough to reproduce important features of the reference surface model, such as its adiabatic energies and derivative couplings. In addition, nonadiabatic surface hopping simulations with interpolation yield population transfer dynamics that is well in accord with the result generated with the reference analytic surface. With these, we conclude by suggesting that the interpolation of diabatic Hamiltonians will be applicable for studying nonadiabatic behaviors of sizeable molecules.

  4. Difluorenyl carbo-Benzenes: Synthesis, Electronic Structure, and Two-Photon Absorption Properties of Hydrocarbon Quadrupolar Chromophores.

    Science.gov (United States)

    Baglai, Iaroslav; de Anda-Villa, Manuel; Barba-Barba, Rodrigo M; Poidevin, Corentin; Ramos-Ortíz, Gabriel; Maraval, Valérie; Lepetit, Christine; Saffon-Merceron, Nathalie; Maldonado, José-Luis; Chauvin, Remi

    2015-09-28

    The synthesis, crystal and electronic structures, and one- and two-photon absorption properties of two quadrupolar fluorenyl-substituted tetraphenyl carbo-benzenes are described. These all-hydrocarbon chromophores, differing in the nature of the linkers between the fluorenyl substituents and the carbo-benzene core (C-C bonds for 3 a, C-C=C-C expanders for 3 b), exhibit quasi-superimposable one-photon absorption (1PA) spectra but different two-photon absorption (2PA) cross-sections σ2PA. Z-scan measurements (under NIR femtosecond excitation) indeed showed that the C≡C expansion results in an approximately twofold increase in the σ2PA value, from 336 to 656 GM (1 GM = 10(-50) cm(4) s molecule(-1) photon(-1)) at λ = 800 nm. The first excited states of Au and Ag symmetry accounting for 1PA and 2PA, respectively, were calculated at the TDDFT level of theory and used for sum-over-state estimations of σ2PA(λi), in which λi = 2 hc/Ei, h is Planck's constant, c is the speed of light, and Ei is the energy of the 2PA-allowed transition. The calculated σ2PA values of 227 GM at 687 nm for 3 a and 349 GM at 708 nm for 3 b are in agreement with the Z-scan results.

  5. A Novel Radiative Substrate Heater

    OpenAIRE

    CEYLAN, Abdullah; Kaynak, Erdal; ÖZCAN, Şadan; Firat, Tezer

    2004-01-01

    In this work, we have developed a new low cost radiative substrate heater for deposition of high-Tc superconducting thin films. It has all the features required for the preparation of high quality superconducting thin films. It is possible to reach ~ 800 °C substrate temperature with it by using only one 250 W halogen projector bulb.

  6. An analogue conceptual rainfall-runoff model for educational purposes

    Science.gov (United States)

    Herrnegger, Mathew; Riedl, Michael; Schulz, Karsten

    2016-04-01

    Conceptual rainfall-runoff models, in which runoff processes are modelled with a series of connected linear and non-linear reservoirs, remain widely applied tools in science and practice. Additionally, the concept is appreciated in teaching due to its somewhat simplicity in explaining and exploring hydrological processes of catchments. However, when a series of reservoirs are used, the model system becomes highly parametrized and complex and the traceability of the model results becomes more difficult to explain to an audience not accustomed to numerical modelling. Since normally the simulations are performed with a not visible digital code, the results are also not easily comprehensible. This contribution therefore presents a liquid analogue model, in which a conceptual rainfall-runoff model is reproduced by a physical model. This consists of different acrylic glass containers representing different storage components within a catchment, e.g. soil water or groundwater storage. The containers are equipped and connected with pipes, in which water movement represents different flow processes, e.g. surface runoff, percolation or base flow. Water from a storage container is pumped to the upper part of the model and represents effective rainfall input. The water then flows by gravity through the different pipes and storages. Valves are used for controlling the flows within the analogue model, comparable to the parameterization procedure in numerical models. Additionally, an inexpensive microcontroller-based board and sensors are used to measure storage water levels, with online visualization of the states as time series data, building a bridge between the analogue and digital world. The ability to physically witness the different flows and water levels in the storages makes the analogue model attractive to the audience. Hands-on experiments can be performed with students, in which different scenarios or catchment types can be simulated, not only with the analogue but

  7. Soft substrates suppress droplet splashing

    CERN Document Server

    Howland, Christopher J; Style, Robert W; Castrejón-Pita, A A

    2015-01-01

    Droplets splash when they impact dry, flat substrates above a critical velocity that depends on parameters such as droplet size, viscosity and air pressure. We show that substrate stiffness also impacts the splashing threshold by imaging ethanol drops impacting silicone gels of different stiffnesses. Splashing is significantly suppressed: droplets on the softest substrates need over 70% more kinetic energy to splash than they do on rigid substrates. We show that splash suppression is likely to be due to energy losses caused by deformations of soft substrates during the first few microseconds of impact. We find that solids with Youngs modulus $\\lesssim O(10^5)$Pa suppress splashing, in agreement with simple scaling arguments. Thus materials like soft gels and elastomers can be used as simple coatings for effective splash prevention.

  8. Analogue Wormholes and Black Hole LASER Effect in Hydrodynamics

    CERN Document Server

    Peloquin, Cédric; Philbin, Thomas; Rousseaux, Germain

    2015-01-01

    We numerically study water wave packets on a spatially varying counter-current in the presence of surface tension. Depending on the details of the velocity profile, we show that traversable and bi-directional analogue wormholes exist in fluid mechanics. The limitations on traversability of wormholes in general relativity are absent here because of the dispersion of water waves and the ability to form flow profiles that are not solutions of Einstein's equations. We observe that negative energy can be trapped between analogue horizons forming a LASER-like cavity. Six horizons are involved in the trapping cavity because of the existence of two dispersive scales, in contrast to previous treatments which considered two horizons and one dispersive scale.

  9. Matrices with restricted entries and q-analogues of permutations

    CERN Document Server

    Lewis, Joel Brewster; Morales, Alejandro H; Panova, Greta; Sam, Steven V; Zhang, Yan

    2010-01-01

    We study the functions that count matrices of given rank over a finite field with specified positions equal to zero. We show that these matrices are $q$-analogues of permutations with certain restricted values. We obtain a simple closed formula for the number of invertible matrices with zero diagonal, a $q$-analogue of derangements, and a curious relationship between invertible skew-symmetric matrices and invertible symmetric matrices with zero diagonal. In addition, we provide recursions to enumerate matrices and symmetric matrices with zero diagonal by rank, and we frame some of our results in the context of Lie theory. Finally, we provide a brief exposition of polynomiality results for enumeration questions related to those mentioned, and give several open questions.

  10. Stark absorption spectroscopy of peridinin and allene-modified analogues

    Energy Technology Data Exchange (ETDEWEB)

    Kusumoto, Toshiyuki; Horibe, Tomoko [Department of Physics and CREST-JST, Graduated School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585 (Japan); Kajikawa, Takayuki; Hasegawa, Shinji [Department of Chemistry, School of Science and Technology, Kwansei Gakuin University, Gakuen 2-1, Sanda, Hyogo 669-1337 (Japan); Iwashita, Takashi [Suntory Institute for Bioorganic Research, Wakayamadai 1-1-1, Shimamoto, Mishimagunn, Osaka 618-8503 (Japan); Cogdell, Richard J. [Glasgow Biomedical Research Centre, University of Glasgow, 120 University Place, Glasgow G12 8QQ, Scotland (United Kingdom); Birge, Robert R.; Frank, Harry A. [Department of Chemistry, University of Connecticut, 55 North Eagleville Road, Storrs, CT 06269-3060 (United States); Katsumura, Shigeo [Department of Chemistry, School of Science and Technology, Kwansei Gakuin University, Gakuen 2-1, Sanda, Hyogo 669-1337 (Japan); Hashimoto, Hideki, E-mail: hassy@sci.osaka-cu.ac.jp [Department of Physics and CREST-JST, Graduated School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585 (Japan)

    2010-07-19

    Stark absorption spectra of peridinin (Per) and five allene-modified analogues and their angular dependence as a function of an externally applied electric field were measured in methyl methacrylate polymer at 77 K. In all cases, the energetically lowest absorption band has a significant change of static dipole-moment upon photoexcitation ({Delta}{mu}). In particular, Per has the largest value of |{Delta}{mu}|. The angles between {Delta}{mu} and the transition dipole-moment of all the analogues were determined. It is suggested that the allene group in Per plays a key role as the electron donor in the charge transfer process following photoexcitation. The results of MNDO-PSDCI calculations support this idea.

  11. Neutral Diboron Analogues of Archetypal Aromatic Species by Spontaneous Cycloaddition.

    Science.gov (United States)

    Arrowsmith, Merle; Böhnke, Julian; Braunschweig, Holger; Celik, Mehmet Ali; Claes, Christina; Ewing, William C; Krummenacher, Ivo; Lubitz, Katharina; Schneider, Christoph

    2016-09-05

    Among the numerous routes organic chemists have developed to synthesize benzene derivatives and heteroaromatic compounds, transition-metal-catalyzed cycloaddition reactions are the most elegant. In contrast, cycloaddition reactions of heavier alkene and alkyne analogues, though limited in scope, proceed uncatalyzed. In this work we present the first spontaneous cycloaddition reactions of lighter alkene and alkyne analogues. Selective addition of unactivated alkynes to boron-boron multiple bonds under ambient conditions yielded diborocarbon equivalents of simple aromatic hydrocarbons, including the first neutral 6 π-aromatic diborabenzene compound, a 2 π-aromatic triplet biradical 1,3-diborete, and a phosphine-stabilized 2 π-homoaromatic 1,3-dihydro-1,3-diborete. DFT calculations suggest that all three compounds are aromatic and show frontier molecular orbitals matching those of the related aromatic hydrocarbons, C6 H6 and C4 H4 (2+) , and homoaromatic C4 H5 (+) .

  12. Anti-cancer activities of diospyrin, its derivatives and analogues

    KAUST Repository

    Sagar, Sunil

    2010-09-01

    Natural products have played a vital role in drug discovery and development process for cancer. Diospyrin, a plant based bisnaphthoquinonoid, has been used as a lead molecule in an effort to develop anti-cancer drugs. Several derivatives/analogues have been synthesized and screened for their pro-apoptotic/anti-cancer activities so far. Our review is focused on the pro-apoptotic/anti-cancer activities of diospyrin, its derivatives/analogues and the different mechanisms potentially involved in the bioactivity of these compounds. Particular focus has been placed on the different mechanisms (both chemical and molecular) thought to underlie the bioactivity of these compounds. A brief bioinformatics analysis at the end of the article provides novel insights into the new potential mechanisms and pathways by which these compounds might exert their effects and lead to a better realization of the full therapeutic potential of these compounds as anti-cancer drugs. © 2010 Elsevier Masson SAS. All rights reserved.

  13. Tunneling approach and thermality in dispersive models of analogue gravity

    CERN Document Server

    Belgiorno, F; Piazza, F Dalla

    2014-01-01

    We set up a tunneling approach to the analogue Hawking effect in the case of models of analogue gravity which are affected by dispersive effects. An effective Schroedinger-like equation for the basic scattering phenomenon IN->P+N*, where IN is the incident mode, P is the positive norm reflected mode, and N* is the negative norm one, signalling particle creation, is derived, aimed to an approximate description of the phenomenon. Horizons and barrier penetration play manifestly a key-role in giving rise to pair-creation. The non-dispersive limit is also correctly recovered. Drawbacks of the model are also pointed out and a possible solution ad hoc is suggested.

  14. Liquid Crystal Analogue of Abrikosov Vortex Flow in Superconductors

    CERN Document Server

    Tanaka, A; Hayakawa, R

    1996-01-01

    We extend the correspondence between the Renn-Lubensky Twist-Grain-Boundary-A phase in chiral liquid crystals and the Abrikosov mixed state in superconductors to dynamical aspects. We find that for a TGB sample with free boundaries, an external electric field applied along the helical axis induces a uniform translational motion of the grain boundary system - an analogue of the well-known mixed state flux flow. Likewise, an analogue of the mixed state Nernst effect is found. In much the same way in which the flux flow carries intercore electric fields generating Joule heat in an otherwise dissipation-free system, the grain boundary flow carries along polarized charges, resulting in a finite electric conductivity in a ferroelectric.

  15. Modelling a river catchment using an electrical circuit analogue

    Directory of Open Access Journals (Sweden)

    C. G. Collier

    1998-01-01

    Full Text Available An electrical circuit analogue of a river catchment is described from which is derived an hydrological model of river flow called the River Electrical Water Analogue Research and Development (REWARD model. The model is based upon an analytic solution to the equation governing the flow of electricity in an inductance-capacitance-resistance (LCR circuit. An interpretation of L, C and R in terms of catchment parameters and physical processes is proposed, and tested for the River Irwell catchment in northwest England. Hydrograph characteristics evaluated using the model are compared with observed hydrographs, confirming that the modelling approach does provide a reliable framework within which to investigate the impact of variations in model input data.

  16. The theory of Hawking radiation in laboratory analogues

    CERN Document Server

    Robertson, Scott

    2015-01-01

    Hawking radiation, despite being known to theoretical physics for nearly forty years, remains elusive and undetected. It also suffers, in its original context of gravitational black holes, from practical and conceptual difficulties. Of particular note is the trans-Planckian problem, which is concerned with the apparent origin of the radiation in absurdly high frequencies. In order to gain better theoretical understanding and, it is hoped, experimental verification of Hawking radiation, much study is being devoted to laboratory systems which use moving media to model the spacetime geometry of black holes, and which, by analogy, are also thought to emit Hawking radiation. These analogue systems typically exhibit dispersion, which regularizes the wave behaviour at the horizon at the cost of a more complicated theoretical framework. This tutorial serves as an introduction to Hawking radiation and its analogues, developing the moving medium analogy for black holes and demonstrating how dispersion can be incorporat...

  17. New Immunosuppressive Sphingoid Base and Ceramide Analogues in Wild Cordyceps.

    Science.gov (United States)

    Mi, Jia-Ning; Han, Yuwei; Xu, Yingqiong; Kou, Junping; Wang, Jing-Rong; Jiang, Zhi-Hong

    2016-12-14

    A comprehensive identification of sphingoid bases and ceramides in wild Cordyceps was performed by integrating a sequential chromatographic enrichment procedure and an UHPLC-ultrahigh definition-Q-TOF-MS based sphingolipidomic approach. A total of 43 sphingoid bases and 303 ceramides were identified from wild Cordyceps, including 12 new sphingoid base analogues and 159 new ceramide analogues based on high-resolution MS and MS/MS data, isotope distribution, matching with the comprehensive personal sphingolipid database, confirmation by sphingolipid standards and chromatographic retention time rule. The immunosuppressive bioassay results demonstrated that Cordyceps sphingoid base fraction exhibits more potent immunosuppressive activity than ceramide fraction, elucidating the immunosuppressive ingredients of wild Cordyceps. This study represented the most comprehensive identification of sphingoid bases and ceramides from a natural source. The findings of this study provided an insight into therapeutic application of wild Cordyceps.

  18. New selenium-75 labeled radiopharmaceuticals: selenonium analogues of dopamine

    Energy Technology Data Exchange (ETDEWEB)

    Sadek, S.A.; Basmadjian, G.P.; Hsu, P.M.; Rieger, J.A.

    1983-07-01

    Selenium-75 labeled selenonium analogues of dopamine, (2-(3,4-dimethoxyphenyl)ethyl)dimethylselenonium iodide and its dihydroxy analogue, were prepared by reducing (/sup 75/Se)selenious acid with sodium borohydride at pH 6.0 and reacting the NaSeH produced with 1-(3,4-dimethoxyphenyl)-2-(p-toluenesulfonyloxy)ethane. Tissue distribution studies in rats given the /sup 75/Se-labeled selenonium agents intravenously demonstrated high initial heart uptake. Prolonged adrenal retention and high adrenal to blood ratio of compound 4 were observed. The high uptake and adrenal to blood ratio suggest the potential use of compound 4 as a radiopharmaceutical for the adrenal gland.

  19. Basic entwinements: unassuming analogue inserts in basic digital modeling (courses)

    DEFF Research Database (Denmark)

    Wiesner, Thomas

    2012-01-01

    to diverse inter-active discussions and a more conscious re-plays of material transcending the dichotomies of digital/analogue. Keywords Simple didactics, analogue sketching, cognitive space awareness, digital modelling, bachelor first year, morphology of body and space, pataphysics...... between the various intentions and the student’s actual grasp of the many basic architectural element’s interplays of form and space can become apparent. To alleviate, calibrate and cognitively fine-tune the potential for more acute and lasting cognitive understandings of (scaled) body and space...... of options for speedily produced material for various attuned and conscious, supplementary oblique architectural assessments. The simple procedure(s) advance a certain amount of beneficial cognitive complementarities: Beneficial interplay-changes between right and left brain concentrations; Change...

  20. Noncommutative analogue Aharonov-Bohm effect and superresonance

    CERN Document Server

    Anacleto, M A; Passos, E

    2012-01-01

    We consider the idea of modeling a rotating acoustic black hole by an idealized draining bathtub vortex which is a planar circulating flow phenomenon with a sink at the origin. We find the acoustic metric for this phenomenon from a noncommutative Abelian Higgs model. As such the acoustic metric not only describes a rotating acoustic black hole but also inherits the noncommutative characteristic of the spacetime. We address the issues of superresonance and analogue Aharonov-Bohm (AB) effect in this background. We mainly show that the scattering of planar waves by a draining bathtub vortex leads to a modified AB effect and due to spacetime noncommutativity, the phase shift persists even in the limit where the parameters associated with the circulation and draining vanish. Finally, we also find that the analogue AB effect and superresonance are competing phenomena at a noncommutative spacetime.