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Sample records for cation condensed dna

  1. Condensation of nonstochiometric DNA/polycation complexes by divalent cations.

    Science.gov (United States)

    Budker, Vladimir; Trubetskoy, Vladimir; Wolff, Jon A

    2006-12-15

    This study found that divalent cations induced the further condensation of partially condensed DNA within nonstochiometric polycation complexes. The addition of a few mmol of a divalent cation such as calcium reduced by half the inflection point at which DNA became fully condensed by poly-L-lysine (PLL) and a variety of other polycations. The effect on DNA condensation was initially observed using a new method, which is based on the concentration-dependent self-quenching of fluorescent moieties (e.g., rhodamine) covalently linked to the DNA backbone at relatively high densities. Additional analyses, which employed ultracentrifugation, dynamic light scattering, agarose gel electrophoresis, and atomic force microscopy, confirmed the effect of divalent cations. These results provide an additional accounting of the process by which divalent cations induce greater chromatin compaction that is based on the representation of chromatin fibers as a nonstoichiometric polyelectrolyte complex. They also offer a new approach to assemble nonviral vectors for gene therapy.

  2. Intermolecular forces between low generation PAMAM dendrimer condensed DNA helices: role of cation architecture.

    Science.gov (United States)

    An, Min; Parkin, Sean R; DeRouchey, Jason E

    2014-01-28

    In recent years, dendriplexes, complexes of cationic dendrimers with DNA, have become attractive DNA delivery vehicles due to their well-defined chemistries. To better understand the nature of the forces condensing dendriplexes, we studied low generation poly(amidoamine) (PAMAM) dendrimer-DNA complexes and compared them to comparably charged linear arginine peptides. Using osmotic stress coupled with X-ray scattering, we have investigated the effect of molecular chain architecture on DNA-DNA intermolecular forces that determine the net attraction and equilibrium interhelical distance within these polycation condensed DNA arrays. In order to compact DNA, linear cations are believed to bind in DNA grooves and to interact with the phosphate backbone of apposing helices. We have previously shown a length dependent attraction resulting in higher packaging densities with increasing charge for linear cations. Hyperbranched polycations, such as polycationic dendrimers, presumably would not be able to bind to DNA and correlate their charges in the same manner as linear cations. We show that attractive and repulsive force amplitudes in PAMAM-DNA assemblies display significantly different trends than comparably charged linear arginines resulting in lower DNA packaging densities with increasing PAMAM generation. The salt and pH dependencies of packaging in PAMAM dendrimer-DNA and linear arginine-DNA complexes were also investigated. Significant differences in the force curve behaviour and salt and pH sensitivities suggest that different binding modes may be present in DNA condensed by dendrimers when compared to linear polycations.

  3. Thermodynamics of cationic lipid binding to DNA and DNA condensation: roles of electrostatics and hydrophobicity.

    Science.gov (United States)

    Matulis, Daumantas; Rouzina, Ioulia; Bloomfield, Victor A

    2002-06-26

    Alkylammonium binding to DNA was studied by isothermal titration calorimetry. Experimental data, obtained as functions of alkyl chain length, salt concentration, DNA concentration, and temperature, provided a detailed thermodynamic description of lipid-DNA binding reactions leading to DNA condensation. Lipid binding, counterion displacement, and DNA condensation were highly cooperative processes, driven by a large increase in entropy and opposed by a relatively small endothermic enthalpy at room temperature. Large negative heat capacity change indicated a contribution from hydrophobic interactions between aliphatic tails. An approximation of lipid-DNA binding as dominated by two factors-ionic and hydrophobic interactions-yielded a model that was consistent with experimental data. Chemical group contributions to the energetics of binding were determined and could be used to predict energetics of other lipid binding to DNA. Electrostatic and hydrophobic contributions to Gibbs free energy, enthalpy, entropy, and heat capacity could be distinguished by applying additivity principles. Binding of lipids with two, three, and four aliphatic tails was investigated and compared to single-tailed lipid binding. Structurally, the model suggests that lipid cationic headgroups and aliphatic tails distribute evenly and lay down on DNA surface without the formation of micelles.

  4. Investigation of DNA condensing properties of amphiphilic triblock cationic polymers by atomic force microscopy.

    Science.gov (United States)

    Lidgi-Guigui, Nathalie; Guis, Christine; Brissault, Blandine; Kichler, Antoine; Leborgne, Christian; Scherman, Daniel; Labdi, Sid; Curmi, Patrick A

    2010-11-16

    Introduction of nucleic acids into cells is an important biotechnology research field which also holds great promise for therapeutic applications. One of the key steps in the gene delivery process is compaction of DNA into nanometric particles. The study of DNA condensing properties of three linear cationic triblock copolymers poly(ethylenimine-b-propylene glycol-b-ethylenimine), namely, LPEI(50)-PPG(36)-LPEI(50), LPEI(19)-PPG(36)-LPEI(19), and LPEI(14)-PPG(68)-LPEI(14), indicates that proper DNA condensation is driven by both the charge and the size of the respective cationic hydrophilic linear polyethylenimine (LPEI) and neutral hydrophobic poly(propylene glycol) (PPG) parts. Atomic force microscopy was used to investigate the interactions of the triblock copolymers with plasmid DNA at the single molecule level and to enlighten the mechanism involved in DNA condensation.

  5. Investigations on the liquid crystalline phases of cation-induced condensed DNA

    Indian Academy of Sciences (India)

    C K S Pillai; Neethu Sundaresan; M Radhakrishnan Pillai; T Thomas; T J Thomas

    2005-10-01

    Viral and nonviral condensing agents are used in gene therapy to compact oligonucleotides and plasmid DNA into nanostructures for their efficient transport through the cell membranes. Whereas viral vectors are best by the toxic effects on the immune system, most of the nonviral delivery vehicles are not effective for use in clinical system. Recent investigations indicate that the supramolecular organization of DNA in the condensed state is liquid crystalline. The present level of understanding of the liquid crystalline phase of DNA is inadequate and a thorough investigation is required to understand the nature, stability, texture and the influence of various environmental conditions on the structure of the phase. The present study is mainly concerned with the physicochemical investigations on the liquid crystalline transitions during compaction of DNA by cationic species such as polyamines and metallic cations. As a preliminary to the above investigation, studies were conducted on the evolution of mesophase transitions of DNA with various cationic counterion species using polarized light microscopy. These studies indicated significant variations in the phase behaviour of DNA in the presence of Li and other ions. Apart from the neutralization of the charges on the DNA molecule, these ions are found to influence selectively the hydration sphere of DNA that in turn influences the induction and stabilization of the LC phases. The higher stability observed with the liquid crystalline phases of Li-DNA system could be useful in the production of nanostructured DNA. In the case of the polyamine, a structural specificity effect depending on the nature, charge and structure of the polyamine used has been found to be favoured in the crystallization of DNA.

  6. Investigations on the liquid crystalline phases of cation-induced condensed DNA

    Science.gov (United States)

    Pillai, C. K. S.; Sundaresan, Neethu; Radhakrishnan Pillai, M.; Thomas, T.; Thomas, T. J.

    2005-10-01

    Viral and nonviral condensing agents are used in gene therapy to compact oligonucleotides and plasmid DNA into nanostructures for their efficient transport through the cell membranes. Whereas viral vectors are best by the toxic effects on the immune system, most of the nonviral delivery vehicles are not effective for use in clinical system. Recent investigations indicate that the supramolecular organization of DNA in the condensed state is liquid crystalline. The present level of understanding of the liquid crystalline phase of DNA is inadequate and a thorough investigation is required to understand the nature, stability, texture and the influence of various environmental conditions on the structure of the phase. The present study is mainly concerned with the physico-chemical investigations on the liquid crystalline transitions during compaction of DNA by cationic species such as polyamines and metallic cations. As a preliminary to the above investigation, studies were conducted on the evolution of mesophase transitions of DNA with various cationic counterion species using polarized light microscopy. These studies indicated significant variations in the phase behaviour of DNA in the presence of Li and other ions. Apart from the neutralization of the charges on the DNA molecule, these ions are found to influence selectively the hydration sphere of DNA that in turn influences the induction and stabilization of the LC phases. The higher stability observed with the liquid crystalline phases of Li--DNA system could be useful in the production of nanostructured DNA. In the case of the polyamine, a structural specificity effect depending on the nature, charge and structure of the polyamine used has been found to be favoured in the crystallization of DNA.

  7. Divalent counterion-induced condensation of triple-strand DNA.

    Science.gov (United States)

    Qiu, Xiangyun; Parsegian, V Adrian; Rau, Donald C

    2010-12-14

    Understanding and manipulation of the forces assembling DNA/RNA helices have broad implications for biology, medicine, and physics. One subject of significance is the attractive force between dsDNA mediated by polycations of valence ≥ 3. Despite extensive studies, the physical origin of the "like-charge attraction" remains unsettled among competing theories. Here we show that triple-strand DNA (tsDNA), a more highly charged helix than dsDNA, is precipitated by alkaline-earth divalent cations that are unable to condense dsDNA. We further show that our observation is general by examining several cations (Mg(2+), Ba(2+), and Ca(2+)) and two distinct tsDNA constructs. Cation-condensed tsDNA forms ordered hexagonal arrays that redissolve upon adding monovalent salts. Forces between tsDNA helices, measured by osmotic stress, follow the form of hydration forces observed with condensed dsDNA. Probing a well-defined system of point-like cations and tsDNAs with more evenly spaced helical charges, the counterintuitive observation that the more highly charged tsDNA (vs. dsDNA) is condensed by cations of lower valence provides new insights into theories of polyelectrolytes and the biological and pathological roles of tsDNA. Cations and tsDNAs also hold promise as a model system for future studies of DNA-DNA interactions and electrostatic interactions in general.

  8. Quantitative assessment of DNA condensation.

    Science.gov (United States)

    Trubetskoy, V S; Slattum, P M; Hagstrom, J E; Wolff, J A; Budker, V G

    1999-02-15

    A fluorescent method is proposed for assessing DNA condensation in aqueous solutions with variety of condensing agents. The technique is based on the effect of concentration-dependent self-quenching of covalently bound fluorophores upon DNA collapse. The method allows a more precise determination of charge equivalency in titration experiments with various polycations. The technique's ability to determine the number of DNA molecules that are condensed together in close proximity is under further investigation.

  9. Simple Simulations of DNA Condensation

    Energy Technology Data Exchange (ETDEWEB)

    STEVENS,MARK J.

    2000-07-12

    Molecular dynamics simulations of a simple, bead-spring model of semiflexible polyelectrolytes such as DNA are performed. All charges are explicitly treated. Starting from extended, noncondensed conformations, condensed structures form in the simulations with tetravalent or trivalent counterions. No condensates form or are stable for divalent counterions. The mechanism by which condensates form is described. Briefly, condensation occurs because electrostatic interactions dominate entropy, and the favored Coulombic structure is a charge ordered state. Condensation is a generic phenomena and occurs for a variety of polyelectrolyte parameters. Toroids and rods are the condensate structures. Toroids form preferentially when the molecular stiffness is sufficiently strong.

  10. The structure and intermolecular forces of DNA condensates.

    Science.gov (United States)

    Yoo, Jejoong; Aksimentiev, Aleksei

    2016-03-18

    Spontaneous assembly of DNA molecules into compact structures is ubiquitous in biological systems. Experiment has shown that polycations can turn electrostatic self-repulsion of DNA into attraction, yet the physical mechanism of DNA condensation has remained elusive. Here, we report the results of atomistic molecular dynamics simulations that elucidated the microscopic structure of dense DNA assemblies and the physics of interactions that makes such assemblies possible. Reproducing the setup of the DNA condensation experiments, we measured the internal pressure of DNA arrays as a function of the DNA-DNA distance, showing a quantitative agreement between the results of our simulations and the experimental data. Analysis of the MD trajectories determined the DNA-DNA force in a DNA condensate to be pairwise, the DNA condensation to be driven by electrostatics of polycations and not hydration, and the concentration of bridging cations, not adsorbed cations, to determine the magnitude and the sign of the DNA-DNA force. Finally, our simulations quantitatively characterized the orientational correlations of DNA in DNA arrays as well as diffusive motion of DNA and cations.

  11. Polymer induced condensation of dna supercoils

    NARCIS (Netherlands)

    Bessa Ramos Jr., J.E.; Ruggiero Neto, J.; Vries, de R.J.

    2008-01-01

    Macromolecular crowding is thought to be a significant factor driving DNA condensation in prokaryotic cells. Whereas DNA in prokaryotes is supercoiled, studies on crowding-induced DNA condensation have so far focused on linear DNA. Here we compare DNA condensation by poly(ethylene oxide) for superco

  12. Chiral DNA packaging in DNA-cationic liposome assemblies.

    Science.gov (United States)

    Zuidam, N J; Barenholz, Y; Minsky, A

    1999-09-03

    Recent studies have indicated that the structural features of DNA-lipid assemblies, dictated by the lipid composition and cationic lipid-to-DNA ratio, critically affect the efficiency of these complexes in acting as vehicles for cellular delivery of genetic material. Using circular dichroism we find that upon binding DNA, positively-charged liposomes induce a secondary conformational transition of the DNA molecules from the native B form to the C motif. Liposomes composed of positively-charged and neutral 'helper' lipids, found to be particularly effective as transfecting agents, induce - in addition to secondary conformational changes - DNA condensation into a left-handed cholesteric-like phase. A structural model is presented according to which two distinct, yet inter-related modes of DNA packaging coexist within such assemblies. The results underline the notion that subtle changes in the components of a supramolecular assembly may substantially modulate the interplay of interactions which dictate its structure and functional properties.

  13. Divalent cation shrinks DNA but inhibits its compaction with trivalent cation

    Science.gov (United States)

    Tongu, Chika; Kenmotsu, Takahiro; Yoshikawa, Yuko; Zinchenko, Anatoly; Chen, Ning; Yoshikawa, Kenichi

    2016-05-01

    Our observation reveals the effects of divalent and trivalent cations on the higher-order structure of giant DNA (T4 DNA 166 kbp) by fluorescence microscopy. It was found that divalent cations, Mg(2+) and Ca(2+), inhibit DNA compaction induced by a trivalent cation, spermidine (SPD(3+)). On the other hand, in the absence of SPD(3+), divalent cations cause the shrinkage of DNA. As the control experiment, we have confirmed the minimum effect of monovalent cation, Na(+) on the DNA higher-order structure. We interpret the competition between 2+ and 3+ cations in terms of the change in the translational entropy of the counterions. For the compaction with SPD(3+), we consider the increase in translational entropy due to the ion-exchange of the intrinsic monovalent cations condensing on a highly charged polyelectrolyte, double-stranded DNA, by the 3+ cations. In contrast, the presence of 2+ cation decreases the gain of entropy contribution by the ion-exchange between monovalent and 3+ ions.

  14. Spermidine-induced two-dimensional DNA condensations on mica surfaces: A different pathway from condensations in solution

    Institute of Scientific and Technical Information of China (English)

    ZHANG XingHua; HOU XiMiao; JI Chao; LI Ming; DOU ShuoXing; WANG PengYe

    2009-01-01

    With atomic force microscopy (AFM) we systematically studied the DNA condensations on mica surfaces induced by multivalent cation spermidine. The pattern of the DNA condensates is a flat single layer, with a core in the centre and DNA wrapping around it at high density. We assume this to be a two-dimensional condensation of free coiled DNA onto negatively charged mica surfaces by the multivalent cation. The DNA molecules condense on mica surfaces via a pathway different from the formation of toroids, rods or globules in bulk solutions. We give an explanation to why toroid structures are difficult to be observed by AFM, and further discuss the relationship between DNA condensations in solutions and on mica surfaces. The present work will be helpful for understanding the behaviors of DNA on charged surfaces, which might be significantly different from that in solutions.

  15. DNA condensation in one dimension

    Science.gov (United States)

    Pardatscher, Günther; Bracha, Dan; Daube, Shirley S.; Vonshak, Ohad; Simmel, Friedrich C.; Bar-Ziv, Roy H.

    2016-12-01

    DNA can be programmed to assemble into a variety of shapes and patterns on the nanoscale and can act as a template for hybrid nanostructures such as conducting wires, protein arrays and field-effect transistors. Current DNA nanostructures are typically in the sub-micrometre range, limited by the sequence space and length of the assembled strands. Here we show that on a patterned biochip, DNA chains collapse into one-dimensional (1D) fibres that are 20 nm wide and around 70 µm long, each comprising approximately 35 co-aligned chains at its cross-section. Electron beam writing on a photocleavable monolayer was used to immobilize and pattern the DNA molecules, which condense into 1D bundles in the presence of spermidine. DNA condensation can propagate and split at junctions, cross gaps and create domain walls between counterpropagating fronts. This system is inherently adept at solving probabilistic problems and was used to find the possible paths through a maze and to evaluate stochastic switching circuits. This technique could be used to propagate biological or ionic signals in combination with sequence-specific DNA nanotechnology or for gene expression in cell-free DNA compartments.

  16. Temperature dependence of DNA condensation at high ionic concentration

    Science.gov (United States)

    Mao, Wei; Gao, Qingqing; Liu, Yanhui; Fan, Yangtao; Hu, Lin; Xu, Houqiang

    2016-08-01

    A series of experiments pointed out that compact states of DNA condensed by multivalent cation prefer higher temperature. The condensed DNA takes elongated coil or compact globule states and the population of the compact globule states increases with an increase in temperature. At the same time, a recent experimental work carried out in buffer solution without multivalent cation points out that DNA persistence length strongly depends on the temperature. DNA persistence length is a key parameter for quantitative interpretation of the conformational properties of DNA and related to the bending rigidity of DNA. It is necessary to revolve the effects of temperature dependence of persistence length on DNA condensation, and a model including the temperature dependence of persistence length and strong correlation of multivalent cation on DNA is provided. The autocorrelation function of the tangent vectors is found as an effective way to detect the temperature dependence of toroid conformations. With an increase in temperature, the first periodic oscillation in the autocorrelation function shifts left and the number of segments containing the first periodic oscillation decreases gradually. According to the experiments mentioned above, the long-axis length is defined to estimate the temperature dependence of condensation process further. At the temperatures defined in experiments mentioned above, the relation between long-axis length and temperature matches the experimental results.

  17. Competitive Effects of 2+ and 3+ Cations on DNA Compaction

    CERN Document Server

    Tongu, C; Yoshikawa, Y; Zinchenko, A A; Chen, N; Yoshikawa, K

    2016-01-01

    By using single-DNA observation with fluorescence microscopy, we observed the effects of divalent and trivalent cations on the higher-order structure of giant DNA (T4 DNA with 166 kbp). It was found that divalent cations, such as Mg(2+) and Ca(2+), inhibit DNA compaction induced by a trivalent cation, spermidine (SPD(3+)). On the other hand, in the absence of SPD(3+), divalent cations cause the shrinkage of DNA. These experimental observations are inconsistent with the well-established Debye-Huckel scheme regarding the shielding effect of counter ions, which is given as the additivity of contributions of cations with different valences. We interpreted the competition between 2+ and 3+ cations in terms of the change in the translational entropy of the counter ions before and after the folding transition of DNA. For the compaction with SPD(3+), we considered the increase in translational entropy due to the ion-exchange of the intrinsic monovalent cations condensing on a highly-charged polyelectrolyte, double-st...

  18. Effects of oxaliplatin on DNA condensation

    Institute of Scientific and Technical Information of China (English)

    JU HaiPeng; ZHANG HongYan; LI Wei; WANG PengYe

    2014-01-01

    In this paper the interactions between DNA and anti-cancer drug oxaliplatin were investigated by using magnetic tweezers.The dynamics of DNA condensation due to oxaliplatin was traced under various forces.It is found that torsion constraint in DNA enhances the ability of oxaliplatin for shortening DNA.The transplatin helps oxaliplatin combine to DNA and increase the rate of DNA condensation.All these results are consistent to the previously proposed model and are helpful for further investigation of interaction between DNA and oxaliplatin.

  19. Cation charge dependence of the forces driving DNA assembly.

    Science.gov (United States)

    DeRouchey, Jason; Parsegian, V Adrian; Rau, Donald C

    2010-10-20

    Understanding the strength and specificity of interactions among biologically important macromolecules that control cellular functions requires quantitative knowledge of intermolecular forces. Controlled DNA condensation and assembly are particularly critical for biology, with separate repulsive and attractive intermolecular forces determining the extent of DNA compaction. How these forces depend on the charge of the condensing ion has not been determined, but such knowledge is fundamental for understanding the basis of DNA-DNA interactions. Here, we measure DNA force-distance curves for a homologous set of arginine peptides. All forces are well fit as the sum of two exponentials with 2.4- and 4.8-Å decay lengths. The shorter-decay-length force is always repulsive, with an amplitude that varies slightly with length or charge. The longer-decay-length force varies strongly with cation charge, changing from repulsion with Arg¹ to attraction with Arg². Force curves for a series of homologous polyamines and the heterogeneous protein protamine are quite similar, demonstrating the universality of these forces for DNA assembly. Repulsive amplitudes of the shorter-decay-length force are species-dependent but nearly independent of charge within each species. A striking observation was that the attractive force amplitudes for all samples collapse to a single curve, varying linearly with the inverse of the cation charge.

  20. Effects of Ionic Dependence of DNA Persistence Length on the DNA Condensation at Room Temperature

    Science.gov (United States)

    Mao, Wei; Liu, Yan-Hui; Hu, Lin; Xu, Hou-Qiang

    2016-05-01

    DNA persistence length is a key parameter for quantitative interpretation of the conformational properties of DNA and related to the bending rigidity of DNA. A series of experiments pointed out that, in the DNA condensation process by multivalent cations, the condensed DNA takes elongated coil or compact globule states and the population of the compact globule states increases with an increase in ionic concentration. At the same time, single molecule experiments carried out in solution with multivalent cations (such as spermidine, spermine) indicated that DNA persistence length strongly depends on the ionic concentration. In order to revolve the effects of ionic concentration dependence of persistence length on DNA condensation, a model including the ionic concentration dependence of persistence length and strong correlation of multivalent cation on DNA is provided. The autocorrelation function of the tangent vectors is found as an effective way to detect the ionic concentration dependence of toroidal conformations. With an increase in ion concentration, the first periodic oscillation contained in the autocorrelation function shifts, the number of segment contained in the first periodic oscillation decreases gradually. According to the experiments, the average long-axis length is defined to estimate the ionic concentration dependence of condensation process further. The relation between long-axis length and ionic concentration matches the experimental results qualitatively. Supported by National Natural Science Foundation of China under Grant Nos. 11047022, 11204045, 11464004 and 31360215; The Research Foundation from Ministry of Education of China (212152), Guizhou Provincial Tracking Key Program of Social Development (SY20123089, SZ20113069); The General Financial Grant from the China Postdoctoral Science Foundation (2014M562341); The Research Foundation for Young University Teachers from Guizhou University (201311); The West Light Foundation (2015) and College

  1. High DNA-Binding Affinity and Gene-Transfection Efficacy of Bioreducible Cationic Nanomicelles with a Fluorinated Core.

    Science.gov (United States)

    Wang, Long-Hai; Wu, De-Cheng; Xu, Hang-Xun; You, Ye-Zi

    2016-01-11

    During the last two decades, cationic polymers have become one of the most promising synthetic vectors for gene transfection. However, the weak interactions formed between DNA and cationic polymers result in low transfection efficacy. Furthermore, the polyplexes formed between cationic polymers and DNA generally exhibit poor stability and toxicity because of the large excess of cationic polymer typically required for complete DNA condensation. Herein, we report the preparation of a novel class of bioreducible cationic nanomicelles by the use of disulfide bonds to connect the cationic shell to the fluorocarbon core. These bioreducible nanomicelles form strong interactions with DNA and completely condense DNA at an N/P ratio of 1. The resulting nanomicelle/DNA polyplexes exhibited high biocompatibility and performed very effectively as a gene-delivery system.

  2. Single DNA Condensation Induced by Hexammine Cobalt with Molecular Combing

    Institute of Scientific and Technical Information of China (English)

    Gao-ming Hu; Yu Lin; Shi-yong Ran; Yan-wei Wang; Guang-can Yang

    2012-01-01

    We investigated the interaction between DNA and hexammine cobalt Ⅲ [Co(NH3)6]3+ by a simple molecular combing method and dynamic light scattering.The average extension of λ-DNA-YOYO-1 complex is found to be 20.9 μm,about 30% longer than the contour length of the DNA in TE buffer (10 mmol/L Tris,1 mmol/L EDTA,pH=8.0),due to bis-intercalation of YOYO-1.A multivalent cation,hexammine cobalt,is used for DNA condensation.We find that the length of DNA-[Co(NH3)6]3+ complexes decrease from 20.9 μm to 5.9 μm as the concentration of the [Co(NH3)6]3+ vary from 0 to 3 μmol/L.This observation provides a direct visualization of single DNA condensation induced by hexammine cobalt.The results from the molecular combing studies are supported by dynamic light scattering investigation,where the average hydrodynamic radius of the DNA complex decreases from 203.8 nm to 39.26 nm under the same conditions.It shows that the molecular combing method is feasible for quantitative conformation characterization of single bio-macromolecules.

  3. Spermine Condenses DNA, but Not RNA Duplexes

    Energy Technology Data Exchange (ETDEWEB)

    Katz, Andrea M.; Tolokh, Igor S.; Pabit, Suzette A.; Baker, Nathan; Onufriev, Alexey V.; Pollack, Lois

    2017-01-01

    Interactions between the polyamine spermine and nucleic acids drive important cellular processes. Spermine condenses DNA, and some RNAs such as poly(rA):poly(rU). A large fraction of the spermine present in cells is bound to RNA, but apparently does not condense it. Here, we study the effect of spermine binding to short duplex RNA and DNA and compare our findings with predictions of molecular dynamics simulations. When small numbers of spermine are introduced, RNA with a designed sequence, containing a mixture of 14 GC pairs and 11 AU pairs, resists condensation relative to DNA of an equivalent sequence or to 25 base pair poly(rA):poly(rU) RNA. Comparison of wide-angle x-ray scattering profiles with simulation suggests that spermine is sequestered deep within the major groove of mixed sequence RNA, preventing condensation by limiting opportunities to bridge to other molecules as well as stabilizing the RNA by locking it into a particular conformation. In contrast, for DNA, simulations suggest that spermine binds external to the duplex, offering opportunities for intermolecular interaction. The goal of this study is to explain how RNA can remain soluble, and available for interaction with other molecules in the cell, despite the presence of spermine at concentrations high enough to precipitate DNA.

  4. DNA condensation by high-affinity interaction with avidin.

    Science.gov (United States)

    Morpurgo, Margherita; Radu, Aurelian; Bayer, Edward A; Wilchek, Meir

    2004-01-01

    Avidin, the basic biotin-binding glycoprotein from chicken egg white, is known to interact with DNA, whereas streptavidin, its neutral non-glycosylated bacterial analog, does not. In the present study we investigated the DNA-binding properties of avidin. Its affinity for DNA in the presence and absence of biotin was compared with that of other positively charged molecules, namely the protein lysozyme, the cationic polymers polylysine and polyarginine and an avidin derivative with higher isoelectric point (pI approximately 11) in which most of the lysine residues were converted to homoarginines. Gel-shift assays, transmission electron microscopy and dynamic light scattering experiments demonstrated an unexpectedly strong interaction between avidin and DNA. The most pronounced gel-shift retardation occurred with the avidin-biotin complex, followed by avidin alone and then guanidylated avidin. Furthermore, ultrastructural and light-scattering studies showed that avidin assembles on the DNA molecule in an organized manner. The assembly leads to the formation of nanoparticles that are about 50-100 nm in size (DNA approximately 5 kb) and have a rod-like or toroidal shape. In these particles the DNA is highly condensed and one avidin is bound to each 18 +/- 4 DNA base pairs. The complexes are very stable even at high dilution ([DNA] =10 pM) and are not disrupted in the presence of buffers or salt (up to 200 mM NaCl). The other positively charged molecules also condense DNA and form particles with a globular shape. However, in this case, these particles disassemble by dilution or in the presence of low salt concentration. The results indicate that the interaction of avidin with DNA may also occur under physiological conditions, further enhanced by the presence of biotin. This DNA-binding property of avidin may thus shed light on a potentially new physiological role for the protein in its natural environment.

  5. Mode of formation and structural features of DNA-cationic liposome complexes used for transfection.

    Science.gov (United States)

    Gershon, H; Ghirlando, R; Guttman, S B; Minsky, A

    1993-07-20

    Complexes formed between cationic liposomes and nucleic acids represent a highly efficient vehicle for delivery of DNA and RNA molecules into a large variety of eukaryotic cells. By using fluorescence, gel electrophoresis, and metal-shadowing electron microscopy techniques, the factors that affect the, yet unclear, interactions between DNA and cationic liposomes as well as the structural features of the resulting complexes have been elucidated. A model is suggested according to which cationic liposomes bind initially to DNA molecules to form clusters of aggregated vesicles along the nucleic acids. At a critical liposome density, two processes occur, namely, DNA-induced membrane fusion, indicated by lipid mixing studies, and liposome-induced DNA collapse, pointed out by the marked cooperativity of the encapsulation processes, by their modulations by DNA-condensing agents, and also by their conspicuous independence upon DNA length. The DNA collapse leads to the formation of condensed structures which can be completely encapsulated within the fused lipid bilayers in a fast, highly cooperative process since their exposed surface is substantially smaller than that of extended DNA molecules. The formation of the transfecting DNA-liposome complexes in which the nucleic acids are fully encapsulated within a positively-charged lipid bilayer is proposed, consequently, to be dominated by mutual effects exerted by the DNA and the cationic liposomes, leading to interrelated lipid fusion and DNA collapse.

  6. Atomic Force Microscopy of spermidine-induced DNA condensates on silicon surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Carrasco, I.S.S.; Bastos, F.M.; Munford, M.L.; Ramos, E.B.; Rocha, M.S., E-mail: marcios.rocha@ufv.br

    2012-01-01

    In the present work, we show that oxidized silicon may be successfully used to image multivalent cation-induced DNA condensates under the Atomic Force Microscope (AFM). The images thus obtained are good enough, allowing us to distinguish between different condensate forms and to perform nanometer-sized measurements. Qualitative results previously obtained using mica as a substrate are recovered here. We additionally show that the interactions between the cation spermidine (the condensing agent) and the DNA molecules are not significantly disturbed by the silicon surface, since the phase behavior of an ensemble of DNA molecules deposited on the silicon substrate as a function of the cation concentration is very similar to that found in solution. - Highlights: Black-Right-Pointing-Pointer We developed a protocol do deposit condensed DNA on oxidized silicon substrates. Black-Right-Pointing-Pointer We measured the sizes of the spermidine-induced DNA condensates under the AFM. Black-Right-Pointing-Pointer We sketch the phase diagram of an ensemble of DNA molecules in a spermidine solution.

  7. Theory and simulations of toroidal and rod-like structures in single-molecule DNA condensation.

    Science.gov (United States)

    Cortini, Ruggero; Caré, Bertrand R; Victor, Jean-Marc; Barbi, Maria

    2015-03-14

    DNA condensation by multivalent cations plays a crucial role in genome packaging in viruses and sperm heads, and has been extensively studied using single-molecule experimental methods. In those experiments, the values of the critical condensation forces have been used to estimate the amplitude of the attractive DNA-DNA interactions. Here, to describe these experiments, we developed an analytical model and a rigid body Langevin dynamics assay to investigate the behavior of a polymer with self-interactions, in the presence of a traction force applied at its extremities. We model self-interactions using a pairwise attractive potential, thereby treating the counterions implicitly. The analytical model allows to accurately predict the equilibrium structures of toroidal and rod-like condensed structures, and the dependence of the critical condensation force on the DNA length. We find that the critical condensation force depends strongly on the length of the DNA, and finite-size effects are important for molecules of length up to 10(5)μm. Our Langevin dynamics simulations show that the force-extension behavior of the rod-like structures is very different from the toroidal ones, so that their presence in experiments should be easily detectable. In double-stranded DNA condensation experiments, the signature of the presence of rod-like structures was not unambiguously detected, suggesting that the polyamines used to condense DNA may protect it from bending sharply as needed in the rod-like structures.

  8. Layer-by-layer deposition of oppositely charged polyelectrolytes on the surface of condensed DNA particles.

    Science.gov (United States)

    Trubetskoy, V S; Loomis, A; Hagstrom, J E; Budker, V G; Wolff, J A

    1999-08-01

    DNA can be condensed with an excess of poly-cations in aqueous solutions forming stable particles of submicron size with positive surface charge. This charge surplus can be used to deposit alternating layers of polyanions and polycations on the surface surrounding the core of condensed DNA. Using poly-L-lysine (PLL) and succinylated PLL (SPLL) as polycation and polyanion, respectively, we demonstrated layer-by-layer architecture of the particles. Polyanions with a shorter carboxyl/backbone distance tend to disassemble binary DNA/PLL complexes by displacing DNA while polyanions with a longer carboxyl/backbone distance effectively formed a tertiary complex. The zeta potential of such complexes became negative, indicating effective surface recharging. The charge stoichiometry of the DNA/PLL/SPLL complex was found to be close to 1:1:1, resembling poly-electrolyte complexes layered on macrosurfaces. Recharged particles containing condensed plasmid DNA may find applications as non-viral gene delivery vectors.

  9. Decondensation behavior of DNA chains induced by multivalent cations at high salt concentrations:Molecular dynamics simulations and experiments

    Institute of Scientific and Technical Information of China (English)

    蒋杨伟; 冉诗勇; 何林李; 王向红; 章林溪

    2015-01-01

    Using molecular dynamics simulations and atomic force microscopy (AFM), we study the decondensation process of DNA chains induced by multivalent cations at high salt concentrations in the presence of short cationic chains in solutions. The typical simulation conformations of DNA chains with varying salt concentrations for multivalent cations imply that the concentration of salt cations and the valence of multivalent cations have a strong influence on the process of DNA decondensation. The DNA chains are condensed in the absence of salt or at low salt concentrations, and the compacted conformations of DNA chains become loose when a number of cations and anions are added into the solution. It is explicitly demonstrated that cations can overcompensate the bare charge of the DNA chains and weaken the attraction interactions between the DNA chains and short cationic chains at high salt concentrations. The condensation-decondensation transi-tions of DNA are also experimentally observed in mixing spermidine withλ-phage DNA at different concentrations of NaCl/MgCl2 solutions.

  10. Time study of DNA condensate morphology: implications regarding the nucleation, growth, and equilibrium populations of toroids and rods.

    Science.gov (United States)

    Vilfan, Igor D; Conwell, Christine C; Sarkar, Tumpa; Hud, Nicholas V

    2006-07-04

    It is well known that multivalent cations cause free DNA in solution to condense into nanometer-scale particles with toroidal and rod-like morphologies. However, it has not been shown to what degree kinetic factors (e.g., condensate nucleation) versus thermodynamic factors (e.g., DNA bending energy) determine experimentally observed relative populations of toroids and rods. It is also not clear how multimolecular DNA toroids and rods interconvert in solution. We have conducted a series of condensation studies in which DNA condensate morphology statistics were measured as a function of time and DNA structure. Here, we show that in a typical in vitro DNA condensation reaction, the relative rod population 2 min after the initiation of condensation is substantially greater than that measured after morphological equilibrium is reached (ca. 20 min). This higher population of rods at earlier time points is consistent with theoretical studies that have suggested a favorable kinetic pathway for rod nucleation. By using static DNA loops to alter the kinetics and thermodynamics of condensation, we further demonstrate that reported increases in rod populations associated with decreasing DNA length are primarily due to a change in the thermodynamics of DNA condensation, rather than a change in the kinetics of condensate nucleation or growth. The results presented also reveal that the redistribution of DNA from rods to toroids is mediated through the exchange of DNA strands with solution.

  11. From cation to oxide: hydroxylation and condensation of aqueous complexes; Du cation a l'oxyde: hydroxylation et condensation en solution

    Energy Technology Data Exchange (ETDEWEB)

    Jolivet, J.P. [Universite Pierre et Marie Curie, Chimie de la Matiere Condensee, URA CNRS 1466, 75 - Paris (France)

    1997-07-01

    Hydroxylation, condensation and precipitation of metal cations in aqueous solution are briefly reviewed. Hydroxylation of aqueous complexes essentially depends on the format charge (oxidation state), the size and the pH of the medium. It is the step allowing the condensation reaction. Depending on the nature of complexes (aqua-hydroxo, oxo-hydroxo), the. mechanism of condensation is different, olation or ox-olation respectively. The first one leads to poly-cations or hydroxides more or less stable against dehydration. The second one leads to poly-anions or oxides. Oligomeric species (poly-cations, poly-anions) are form from charged monomer complexes while the formation of solid phases requires non-charged precursors. Because of their high lability, charged oligomers are never the precursors of solids phases. The main routes for the formation of solid phases from solution are studied with two important and representative elements, Al and Si. For Al{sup 3+} ions, different methods (base addition in solution, thermo-hydrolysis, hydrothermal synthesis) are discussed in relation to the crystal structure of the solid phase obtained. For silicic species condensing by ox-olation, the role of acid or base catalysis on the morphology of gels is studied. The influence of complexing ligands on the processes and on the characteristics of solids (morphology of particles, basic salts and polymetallic oxides formation) is studied. (author)

  12. Cationic lipids and cationic ligands induce DNA helix denaturation: detection of single stranded regions by KMnO4 probing.

    Science.gov (United States)

    Prasad, T K; Gopal, Vijaya; Rao, N Madhusudhana

    2003-09-25

    Cationic lipids and cationic polymers are widely used in gene delivery. Using 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) as a cationic lipid, we have investigated the stability of the DNA in DOTAP:DNA complexes by probing with potassium permanganate (KMnO4). Interestingly, thymidines followed by a purine showed higher susceptibility to cationic ligand-mediated melting. Similar studies performed with other water-soluble cationic ligands such as polylysine, protamine sulfate and polyethyleneimine also demonstrated melting of the DNA but with variations. Small cations such as spermine and spermidine and a cationic detergent, cetyl trimethylammonium bromide, also rendered the DNA susceptible to modification by KMnO4. The data presented here provide direct proof for melting of DNA upon interaction with cationic lipids. Structural changes subsequent to binding of cationic lipids/ligands to DNA may lead to instability and formation of DNA bubbles in double-stranded DNA.

  13. Complexation Between Cationic Diblock Copolymers and Plasmid DNA

    Science.gov (United States)

    Jung, Seyoung; Reineke, Theresa; Lodge, Timothy

    Deoxyribonucleic acids (DNA), as polyanions, can spontaneously bind with polycations to form polyelectrolyte complexes. When the polycation is a diblock copolymer with one cationic block and one uncharged hydrophilic block, the polyelectrolyte complexes formed with plasmid DNA (pDNA) are often colloidally stable, and show great promise in the field of polymeric gene therapy. While the resulting properties (size, stability, and toxicity to biological systems) of the complexes have been studied for numerous cationic diblocks, the fundamentals of the pDNA-diblock binding process have not been extensively investigated. Herein, we report how the cationic block content of a diblock influences the pDNA-diblock interactions. pDNA with 7164 base pairs and poly(2-deoxy-2-methacrylamido glucopyranose)-block-poly(N-(2-aminoethyl) methacrylamide) (PMAG-b-PAEMA) are used as the model pDNA and cationic diblock, respectively. To vary the cationic block content, two PMAG-b-PAEMA copolymers with similar PMAG block lengths but distinct PAEMA block lengths and a PAEMA homopolymer are utilized. We show that the enthalpy change from pDNA-diblock interactions is dependent on the cationic diblock composition, and is closely associated with both the binding strength and the pDNA tertiary structure.

  14. Cationic lipids delay the transfer of plasmid DNA to lysosomes.

    Science.gov (United States)

    Wattiaux, R; Jadot, M; Laurent, N; Dubois, F; Wattiaux-De Coninck, S

    1996-10-14

    Plasmid 35S DNA, naked or associated with different cationic lipid preparations was injected to rats. Subcellular distribution of radioactivity in the liver one hour after injection, was established by centrifugation methods. Results show that at that time, 35S DNA has reached lysosomes. On the contrary, when 35S DNA was complexed with lipids, radioactivity remains located in organelles whose distribution after differential and isopycnic centrifugation, is clearly distinct from that of arylsulfatase, lysosome marker enzyme. Injection of Triton WR 1339, a specific density perturbant of lysosomes, four days before 35S DNA injection causes a density decrease of radioactivity bearing structures, apparent one hour after naked 35S DNA injection but visible only after more than five hours, when 35S DNA associated with a cationic lipid is injected. These observations show that cationic lipids delay the transfer to lysosomes, of plasmid DNA taken up by the liver.

  15. Molecular recognition of genomic DNA in a condensate with a model surfactant for potential gene-delivery applications.

    Science.gov (United States)

    Singh, Priya; Choudhury, Susobhan; Chandra, Goutam Kumar; Lemmens, Peter; Pal, Samir Kumar

    2016-04-01

    The functionality of a gene carrying nucleic acid in an artificial gene-delivery system is important for the overall efficiency of the vehicle in vivo. Here, we have studied a well-known artificial gene-delivery system, which is a condensate of calf thymus DNA (CT-DNA) with a model cationic surfactant cetyltrimethylammonium bromide (CTAB) to investigate the molecular recognition of the genomic DNA in the condensate. While dynamic light scattering (DLS) and circular dichroism (CD) reveal structural aspects of the condensate and the constituting DNA respectively, picosecond resolved polarization gated spectroscopy and Förster resonance energy transfer (FRET) reveal molecular recognition of the genomic DNA in the condensate. We have considered ethidium bromide (EB) and crystal violet (CV), which are well known DNA-binding agents through intercalative (specific) and electrostatic (non-specific) interactions, respectively, as model ligands for the molecular recognition studies. A fluorescent cationic surfactant, Nonyl Acridine Orange (NAO) is considered to be a mimic of CTAB in the condensate. The polarization gated fluorescence of NAO at various temperatures has been used to investigate the local microviscosity of the condensate. The excellent spectral overlap of NAO emission and the absorption spectra of both EB and CV allow us to investigate FRET-distances of the ligands with respect to NAO in the condensate at various temperatures and thermal stability of ligand-binding of the genomic DNA. The thermodynamic properties of the molecular recognition have also been explored using Van't Hoff equation. We have also extended our studies to molecular recognition of the genomic DNA in the condensate as dried thin films. This has important implications for its application in bioelectronics.

  16. Synergy of DNA-bending nucleoid proteins and macromolecular crowd-condensing DNA

    NARCIS (Netherlands)

    Bessa Ramos, E.; Wintraecken, C.H.J.M.; Geerling, A.C.M.; Vries, de R.J.

    2007-01-01

    Many prokaryotic nucleoid proteins bend DNA and form extended helical protein-DNA fibers rather than condensed structures. On the other hand, it is known that such proteins (such as bacterial HU) strongly promote DNA condensation by macromolecular crowding. Using theoretical arguments, we show that

  17. Activation of DNA damage response signaling by condensed chromatin.

    Science.gov (United States)

    Burgess, Rebecca C; Burman, Bharat; Kruhlak, Michael J; Misteli, Tom

    2014-12-11

    The DNA damage response (DDR) occurs in the context of chromatin, and architectural features of chromatin have been implicated in DNA damage signaling and repair. Whereas a role of chromatin decondensation in the DDR is well established, we show here that chromatin condensation is integral to DDR signaling. We find that, in response to DNA damage chromatin regions transiently expand before undergoing extensive compaction. Using a protein-chromatin-tethering system to create defined chromatin domains, we show that interference with chromatin condensation results in failure to fully activate DDR. Conversely, forced induction of local chromatin condensation promotes ataxia telangiectasia mutated (ATM)- and ATR-dependent activation of upstream DDR signaling in a break-independent manner. Whereas persistent chromatin compaction enhanced upstream DDR signaling from irradiation-induced breaks, it reduced recovery and survival after damage. Our results demonstrate that chromatin condensation is sufficient for activation of DDR signaling and is an integral part of physiological DDR signaling.

  18. Investigation of various structures of DNA molecules (Ⅲ)——Coil-globe transition of λ-DNA induced by cationic surfactant

    Institute of Scientific and Technical Information of China (English)

    冯喜增; 林璋; 王琛; 白春礼

    1999-01-01

    The structure transition of λ-DNA induced by cationic surfactant cellar media was investigated by using CD, SEM and AFM. The experimental data of CD revealed that λ-DNA can be induced from B-form to a collapsed structure with the addition of the cationic surfactant CTAB to the system. The condensed process of λ-DNA from coil state to small globular state (diameter about 1.25 μm) and finally big globular state (diameter about 5.4 μm) was observed by using SEM and AFM.

  19. Photoluminescence quenching of [Ru(bpy)2(atatp)](2+) bound to a condensed DNA matrix.

    Science.gov (United States)

    Chen, Linlin; Chao, Hui; Zhao, Qianwen; Zheng, Xuling; Li, Hong

    2016-01-01

    A novel [Ru(bpy)2(atatp)](2+) (bpy=2,2'-bipyridine and atatp=acenaphtheno[1,2-b]-1,4,8,9-tetraazatriphenylene) can induce the condensation of herring sperm DNA to form an orange-red cast film via intercalation and electrostatic attraction. The thus-prepared cast film shows microsecond emission lifetimes and reversible luminescence tuning characteristics by oxygen and nitrogen with an on-off emission intensity ratio of 4.3. The photoluminescence of [Ru(bpy)2(atatp)](2+) bound to a DNA condensed matrix can be quenched by water, dissolved oxygen, copper(II) and ferrocyanide ions. The DNA binding is found to hardly alter the dynamic quenching of [Ru(bpy)2(atatp)](2+) by oxygen at a low DNA-to-Ru(II) molar ratio (r=0.83), allowing [Ru(bpy)2(atatp)](2+) to keep a basically unchanged oxygen quenching constant, as well as endow the photo-induced electron transfer between [Ru(bpy)2(atatp)](2+) and copper(II) cations, and weaken the electrostatic attraction of [Ru(bpy)2(atatp)](2+) with ferrocyanide anions. In addition, the DNA condensation induced by [Ru(bpy)2(atatp)](2+) can protect the DNA oxidative damage against superoxide anion and hydroxyl radical toxicity. The present results could provide a versatile platform for better fabrication of optoelectronic devices.

  20. Effect of clustered peptide binding on DNA condensation.

    Science.gov (United States)

    Haley, Jennifer; Kabiru, Paul; Geng, Yan

    2010-01-01

    DNA condensation in-vitro has been studied as a model system to reveal common principles underlying gene packaging in biology, and as the critical first step towards the development of non-viral gene delivery vectors. In this study, we use a bio-inspired approach, where small DNA-binding peptides are controllably clustered by an amphiphilic block copolymer scaffold, to reveal the effect of clustered peptide binding on the energetics, size, shape and physical properties of DNA condensation in-vitro. This provides insights into the general architectural effect of gene-binding proteins on DNA condensation process. Moreover, the versatility afforded by regulating the clustering density and composition of peptides may provide a novel design platform for gene delivery applications in the future.

  1. Microscopic insight into the DNA condensation process of a zwitterion-functionalized polycation.

    Science.gov (United States)

    Sun, Hui; Zhou, Li; Chen, Xiaolu; Han, Xia; Wang, Rui; Liu, Honglai

    2016-11-01

    Zwitterion-functionalized polycations are ideal gene carriers with long circulation, high cellular uptaking and low cell viability. However, the trade-off between the DNA condensation efficiency and the cell viability must be addressed. The purpose of this study is to provide a microscopic insight into the DNA condensation process and to explore the effect of a zwitterionic block of zwitterion-functionalized polycation, which is of great significance in designing novel gene delivery systems. Poly[2-(dimethylamino)ethyl methacrylate-b-(sulfobetaine methacrylate)] (PDMAEMA-b-PSBMA) copolymers were synthesized and used as the model systems. Different from the conventional concept that the PSBMA zwitterionic block act only as the "stealthy" groups, the subtle differences in physical and colloidal characteristics between the polycation/DNA polyplexes show that the PSBMA segment is capable of wrapping DNA attributed to the quaternary ammonium cations, without compromising the DNA condensation capability. On the other hand, the incorporation of PSBMA block reduces the surface charge of the polyplexes, which substantially result in the inefficient transfection and the reduced cytotoxicity.

  2. Benzo[f]azino[2,1-a]phthalazinium cations: novel DNA intercalating chromophores with antiproliferative activity.

    Science.gov (United States)

    Martínez, Valentín; Burgos, Carolina; Alvarez-Builla, Julio; Fernández, Gerónimo; Domingo, Alberto; García-Nieto, Raquel; Gago, Federico; Manzanares, Ignacio; Cuevas, Carmen; Vaquero, Juan J

    2004-02-26

    New azaquinolizinium-type cations have been obtained from isochromane. The synthesis was completed over seven steps and included as the key feature an intramolecular Westphal condensation. This first example of the intramolecular process allowed the preparation of benzo[f]pyrido[2,1-a]phthalazinium and benzo[f]quino[2,1-a]phthalazinium salts, which were evaluated as DNA intercalators, DNA topoisomerase I inhibitors, and antiproliferative compounds. Both cationic systems behave as DNA intercalators and exhibit antiproliferative activity. The pentacyclic benzo[f]quino[2,1-a]phthalazinium cations also have an inhibitory effect on the catalytic activity of DNA topoisomerase I, without trapping of cleavage complexes. Structural characterization using density functional theory indicates that the fused ring systems are slightly nonplanar, and additional molecular modeling studies suggest a preferred orientation for the intercalating chromophores within a typical CpG or TpG intercalation site.

  3. Unfolding DNA condensates produced by DNA-like charged depletants: A force spectroscopy study

    Science.gov (United States)

    Lima, C. H. M.; Rocha, M. S.; Ramos, E. B.

    2017-02-01

    In this work, we have measured, by means of optical tweezers, forces acting on depletion-induced DNA condensates due to the presence of the DNA-like charged protein bovine serum albumin (BSA). The stretching and unfolding measurements performed on the semi-flexible DNA chain reveal (1) the softening of the uncondensed DNA contour length and (2) a mechanical behavior strikingly different from those previously observed: the force-extension curves of BSA-induced DNA condensates lack the "saw-tooth" pattern and applied external forces as high as ≈80 pN are unable to fully unfold the condensed DNA contour length. This last mechanical experimental finding is in agreement with force-induced "unpacking" detailed Langevin dynamics simulations recently performed by Cortini et al. on model rod-like shaped condensates. Furthermore, a simple thermodynamics analysis of the unfolding process has enabled us to estimate the free energy involved in the DNA condensation: the estimated depletion-induced interactions vary linearly with both the condensed DNA contour length and the BSA concentration, in agreement with the analytical and numerical analysis performed on model DNA condensates. We hope that future additional experiments can decide whether the rod-like morphology is the actual one we are dealing with (e.g. pulling experiments coupled with super-resolution fluorescence microscopy).

  4. Cationic Polybutyl Cyanoacrylate Nanoparticles for DNA Delivery

    Directory of Open Access Journals (Sweden)

    Jinghua Duan

    2009-01-01

    Full Text Available To enhance the intracellular delivery potential of plasmid DNA using nonviral vectors, we used polybutyl cyanoacrylate (PBCA and chitosan to prepare PBCA nanoparticles (NPs by emulsion polymerization and prepared NP/DNA complexes through the complex coacervation of nanoparticles with the DNA. The object of our work is to evaluate the characterization and transfection efficiency of PBCA-NPs. The NPs have a zeta potential of 25.53 mV at pH 7.4 and size about 200 nm. Electrophoretic analysis suggested that the NPs with positive charges could protect the DNA from nuclease degradation and cell viability assay showed that the NPs exhibit a low cytotoxicity to human hepatocellular carcinoma (HepG2 cells. Qualitative and quantitative analysis of transfection in HepG2 cells by the nanoparticles carrying plasmid DNA encoding for enhanced green fluorescent protein (EGFP-N1 was done by digital fluorescence imaging microscopy system and fluorescence-activated cell sorting (FACS. Qualitative results showed highly efficient expression of GFP that remained stable for up to 96 hours. Quantitative results from FACS showed that PBCA-NPs were significantly more effective in transfecting HepG2 cells after 72 hours postincubation. The results of this study suggested that PBCA-NPs have favorable properties for nonviral delivery.

  5. Measuring cation dependent DNA polymerase fidelity landscapes by deep sequencing.

    Directory of Open Access Journals (Sweden)

    Bradley Michael Zamft

    Full Text Available High-throughput recording of signals embedded within inaccessible micro-environments is a technological challenge. The ideal recording device would be a nanoscale machine capable of quantitatively transducing a wide range of variables into a molecular recording medium suitable for long-term storage and facile readout in the form of digital data. We have recently proposed such a device, in which cation concentrations modulate the misincorporation rate of a DNA polymerase (DNAP on a known template, allowing DNA sequences to encode information about the local cation concentration. In this work we quantify the cation sensitivity of DNAP misincorporation rates, making possible the indirect readout of cation concentration by DNA sequencing. Using multiplexed deep sequencing, we quantify the misincorporation properties of two DNA polymerases--Dpo4 and Klenow exo(---obtaining the probability and base selectivity of misincorporation at all positions within the template. We find that Dpo4 acts as a DNA recording device for Mn(2+ with a misincorporation rate gain of ∼2%/mM. This modulation of misincorporation rate is selective to the template base: the probability of misincorporation on template T by Dpo4 increases >50-fold over the range tested, while the other template bases are affected less strongly. Furthermore, cation concentrations act as scaling factors for misincorporation: on a given template base, Mn(2+ and Mg(2+ change the overall misincorporation rate but do not alter the relative frequencies of incoming misincorporated nucleotides. Characterization of the ion dependence of DNAP misincorporation serves as the first step towards repurposing it as a molecular recording device.

  6. Computational and analytical modeling of cationic lipid-DNA complexes.

    Science.gov (United States)

    Farago, Oded; Grønbech-Jensen, Niels

    2007-05-01

    We present a theoretical study of the physical properties of cationic lipid-DNA (CL-DNA) complexes--a promising synthetically based nonviral carrier of DNA for gene therapy. The study is based on a coarse-grained molecular model, which is used in Monte Carlo simulations of mesoscopically large systems over timescales long enough to address experimental reality. In the present work, we focus on the statistical-mechanical behavior of lamellar complexes, which in Monte Carlo simulations self-assemble spontaneously from a disordered random initial state. We measure the DNA-interaxial spacing, d(DNA), and the local cationic area charge density, sigma(M), for a wide range of values of the parameter (c) representing the fraction of cationic lipids. For weakly charged complexes (low values of (c)), we find that d(DNA) has a linear dependence on (c)(-1), which is in excellent agreement with x-ray diffraction experimental data. We also observe, in qualitative agreement with previous Poisson-Boltzmann calculations of the system, large fluctuations in the local area charge density with a pronounced minimum of sigma(M) halfway between adjacent DNA molecules. For highly-charged complexes (large (c)), we find moderate charge density fluctuations and observe deviations from linear dependence of d(DNA) on (c)(-1). This last result, together with other findings such as the decrease in the effective stretching modulus of the complex and the increased rate at which pores are formed in the complex membranes, are indicative of the gradual loss of mechanical stability of the complex, which occurs when (c) becomes large. We suggest that this may be the origin of the recently observed enhanced transfection efficiency of lamellar CL-DNA complexes at high charge densities, because the completion of the transfection process requires the disassembly of the complex and the release of the DNA into the cytoplasm. Some of the structural properties of the system are also predicted by a continuum

  7. Cation binding to 15-TBA quadruplex DNA is a multiple-pathway cation-dependent process.

    Science.gov (United States)

    Reshetnikov, Roman V; Sponer, Jiri; Rassokhina, Olga I; Kopylov, Alexei M; Tsvetkov, Philipp O; Makarov, Alexander A; Golovin, Andrey V

    2011-12-01

    A combination of explicit solvent molecular dynamics simulation (30 simulations reaching 4 µs in total), hybrid quantum mechanics/molecular mechanics approach and isothermal titration calorimetry was used to investigate the atomistic picture of ion binding to 15-mer thrombin-binding quadruplex DNA (G-DNA) aptamer. Binding of ions to G-DNA is complex multiple pathway process, which is strongly affected by the type of the cation. The individual ion-binding events are substantially modulated by the connecting loops of the aptamer, which play several roles. They stabilize the molecule during time periods when the bound ions are not present, they modulate the route of the ion into the stem and they also stabilize the internal ions by closing the gates through which the ions enter the quadruplex. Using our extensive simulations, we for the first time observed full spontaneous exchange of internal cation between quadruplex molecule and bulk solvent at atomistic resolution. The simulation suggests that expulsion of the internally bound ion is correlated with initial binding of the incoming ion. The incoming ion then readily replaces the bound ion while minimizing any destabilization of the solute molecule during the exchange.

  8. Cationic Polyene Phospholipids as DNA Carriers for Ocular Gene Therapy

    Directory of Open Access Journals (Sweden)

    Susana Machado

    2014-01-01

    Full Text Available Recent success in the treatment of congenital blindness demonstrates the potential of ocular gene therapy as a therapeutic approach. The eye is a good target due to its small size, minimal diffusion of therapeutic agent to the systemic circulation, and low immune and inflammatory responses. Currently, most approaches are based on viral vectors, but efforts continue towards the synthesis and evaluation of new nonviral carriers to improve nucleic acid delivery. Our objective is to evaluate the efficiency of novel cationic retinoic and carotenoic glycol phospholipids, designated C20-18, C20-20, and C30-20, to deliver DNA to human retinal pigmented epithelium (RPE cells. Liposomes were produced by solvent evaporation of ethanolic mixtures of the polyene compounds and coformulated with 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE or cholesterol (Chol. Addition of DNA to the liposomes formed lipoplexes, which were characterized for binding, size, biocompatibility, and transgene efficiency. Lipoplex formulations of suitable size and biocompatibility were assayed for DNA delivery, both qualitatively and quantitatively, using RPE cells and a GFP-encoding plasmid. The retinoic lipoplex formulation with DOPE revealed a transfection efficiency comparable to the known lipid references 3β-[N-(N′,N′-dimethylaminoethane-carbamoyl]-cholesterol (DC-Chol and 1,2-dioleoyl-sn-glycero-3-ethylphosphocholine (EPC and GeneJuice. The results demonstrate that cationic polyene phospholipids have potential as DNA carriers for ocular gene therapy.

  9. Optical tweezers reveal a dynamic mechanical response of cationic peptide-DNA complexes

    Science.gov (United States)

    Lee, Amy; Zheng, Tai; Sucayan, Sarah; Chou, Szu-Ting; Tricoli, Lucas; Hustedt, Jason; Kahn, Jason; Mixson, A. James; Seog, Joonil

    2013-03-01

    Nonviral carriers have been developed to deliver nucleic acids by forming nanoscale complexes; however, there has been limited success in achieving high transfection efficiency. Our hypothesis is that a factor affecting gene delivery efficiency is the mechanical response of the condensed complex. To begin to test this hypothesis, we directly measured the mechanical properties of DNA-carrier complexes using optical tweezers. Histidine-lysine (HK) polymer, Asparagine-lysine (NK) polymer and poly-L-lysine were used to form complexes with a single DNA molecule. As carriers were introduced, a sudden decrease in DNA extension occurrs at a force level which is defined as critical force (Fc). Fc is carrier and concentration dependent. Pulling revealed reduction in DNA extension length for HK-DNA complexes. The characteristics of force profiles vary by agent and can be dynamically manipulated by changes in environmental conditions such as ionic strength of the buffer as well as pH. Heparin can remove cationic reagents which are otherwise irreversibly bound to DNA. The implications for optimizing molecular interactions to enhance transfection efficiency will be discussed.

  10. Electrochemical uranyl cation biosensor with DNA oligonucleotides as receptor layer.

    Science.gov (United States)

    Jarczewska, Marta; Ziółkowski, Robert; Górski, Łukasz; Malinowska, Elżbieta

    2014-04-01

    The present study aims at the further development of the uranyl oligonucleotide-based voltammetric biosensor, which takes advantage of strong interaction between UO2(2+) and phosphate DNA backbone. Herein we report the optimization of working parameters of previously elaborated electrochemical DNA biosensor. It is shown that the sensor sensitivity is highly dependent on the oligonucleotide probe length and the incubation time of sensor in a sample solution. Consequently, the highest sensitivity was obtained for 10-nucleotide sequence and 60 min incubation time. The lower detection limit towards uranyl cation for developed biosensor was 30 nM. The influence of mixed monolayers and the possibility of developing a non-calibration device were also investigated. The selectivity of the proposed biosensor was significantly improved via elimination of adenine nucleobases from the DNA probe. Moreover, the regeneration procedure was elaborated and tested to prolong the use of the same biosensor for 4 subsequent determinations of UO2(2+).

  11. DNA-poly(vinyl alcohol) gel matrices: release properties are strongly dependent on electrolytes and cationic surfactants.

    Science.gov (United States)

    Valente, Artur J M; Cruz, Sandra M A; Murtinho, Dina M B; Miguel, M Graça; Muniz, Edvani C

    2013-01-01

    The release of DNA from cryogel PVA-DNA gel matrices to different electrolyte aqueous solutions was investigated. The rate of release and the distribution coefficient of DNA have been quantified by using a first order kinetic law equation, developed in the frame of a partition-based model. The release of DNA from gels to 1:1 sodium and nitrate salts shows that the transport properties are dependent on the ability of anions/cations to solubilise the DNA in the aqueous phase which, with the exception of bromide, can be related to the Hofmeister series; in the presence of multivalent electrolytes, or increasing the ionic strength, the condensation of DNA inside the gel, followed by a phase separation as seen by scanning electron microscopy, induces the retention of DNA inside the polymer matrix. The DNA condensation and/or phase separation, which contribute to a decrease in the water volume fraction inside the gel, determined by swelling degree experiments, also lead to a decrease in the rate constant of DNA release; such decrease can be justified by the difficulty of the molecular aggregate to move through out the polymeric structure. The DNA release is also dependent on the pH of the bulk solution. The effect of uni- and di-valent cationic surfactants on the release properties of DNA was also evaluated. Our findings suggest that the kinetics of DNA release depends on a complex balance between different structural properties of the surfactants, namely charge, bulkiness of the headgroup and alkyl chain length.

  12. Structure-function investigations of DNA condensing agents with application to gene delivery

    Science.gov (United States)

    Evans, Heather Marie

    Lipid-based systems are notoriously poor for gene delivery, and their use has been primarily empirical. In order to improve these systems, it is imperative to obtain a greater understanding of molecular interactions between DNA and positively charged molecules. A variety of cationic molecules have been studied with DNA, in an attempt to correlate structural properties of these assemblies (using x-ray diffraction) with their efficiency as DNA carriers for gene delivery (using a luciferase assay). Several systems have been studied, some of which use the same charged amine moieties presented in three distinct morphologies: the multivalent salts spermine and spermidine, dendrimers, and dendrimeric lipids. The dendrimers somewhat approximate the properties of histories, cylindrical proteins that condense intracellular DNA. Structural studies of histone and DNA have also been conducted in order to better understand these interactions and their possible relevance to the gene delivery pathway. In addition, empirical evidence suggests that for successful in vivo gene delivery, cholesterol should be used as a helper lipid. The delivery efficiency and structural behavior of cholesterol and other sterol molecules have been studied in ternary lipid mixtures.

  13. DNA packaging induced by micellar aggregates: a novel in vitro DNA condensation system.

    Science.gov (United States)

    Ghirlando, R; Wachtel, E J; Arad, T; Minsky, A

    1992-08-11

    Evidence for a conceptually novel DNA packaging process is presented. X-ray scattering, electron microscopy, and circular dichroism measurements indicate that in the presence of positively charged micellar aggregates and flexible anionic polymers, such as negatively charged polypeptides or single-stranded RNA species, a complex is formed in which DNA molecules are partially embedded within a micellar scaffold and partially condensed into highly packed chiral structures. Based on studies of micelle-DNA and micelle-flexible anionic polymer systems, as well as on the known effects of a high charge density upon the micellar organization, a DNA packaging model is proposed. According to this model, the DNA induces the elongation of the micelles into rodlike aggregates, forming a closely packed matrix in which the DNA molecules are immobilized. In contrast, the flexible anionic polymers stabilize clusters of spherical micelles which are proposed to effect a capping of the rodlike micelles, thus arresting their elongation and creating surfactant-free segments of the DNA that are able to converge and collapse. Thus, unlike other in vitro DNA packaging systems, in which condensation follows encounters between charge-neutralized DNA molecules, a prepackaging phase where the DNA is immobilized within a matrix is proposed in this case. Cellular and nuclear membranes have been implicated in DNA packaging processes in vivo, and negatively charged polyelectrolytes were shown to be involved in the processes. These observations, combined with the basic tenets of the DNA condensation system described here, allow for the progression to the study of more elaborate model systems and thus might lead to insights into the nature and roles of the intricate in vivo DNA-membrane complexes.

  14. The role of a microscopic colloidally stabilized phase in solubilizing oligoamine-condensed DNA complexes.

    Science.gov (United States)

    Trubetskoy, Vladimir S; Wolff, Jon A; Budker, Vladimir G

    2003-02-01

    DNA complexes of spermine and spermidine become resolubilized at very high concentrations of the oligoamine. It has been postulated that high oligoamine concentrations shift the DNA from the globule back to the coil phase. The present study indicates that DNA resolubilization at high concentrations of spermine and spermidine is explained by formation of small particles of condensed DNA that cannot be precipitated by centrifugation. The fact that DNA stays condensed during resolubilization was confirmed using a relatively new condensation assay and three independent microscopic techniques. A considerable portion of DNA was found to be in particles with diameter <100 nm. Formation of such small particles is likely to be caused by colloidal forces. The ability to form small, condensed DNA particles in solutions that contain high concentrations of oligocation should aid in the design of synthetic DNA vectors for gene transfer and gene therapy and in the handling of DNA for diagnostic studies.

  15. DNA condensates organized by the capsid protein VP15 in White Spot Syndrome Virus.

    Science.gov (United States)

    Liu, Yingjie; Wu, Jinlu; Chen, Hu; Hew, Choy Leong; Yan, Jie

    2010-12-20

    The White Spot Syndrome Virus (WSSV) has a large circular double-stranded DNA genome of around 300kb and it replicates in the nucleus of the host cells. The machinery of how the viral DNA is packaged has been remained unclear. VP15, a highly basic protein, is one of the major capsid proteins found in the virus. Previously, it was shown to be a DNA binding protein and was hypothesized to participate in the viral DNA packaging process. Using Atomic Force Microscopy imaging, we show that the viral DNA is associated with a (or more) capsid proteins. The organized viral DNA qualitatively resembles the conformations of VP15 induced DNA condensates in vitro. Furthermore, single-DNA manipulation experiments revealed that VP15 is able to condense single DNA against forces of a few pico Newtons. Our results suggest that VP15 may aid in the viral DNA packaging process by directly condensing DNA.

  16. Extracellular DNA chelates cations and induces antibiotic resistance in Pseudomonas aeruginosa biofilms.

    Directory of Open Access Journals (Sweden)

    Heidi Mulcahy

    2008-11-01

    Full Text Available Biofilms are surface-adhered bacterial communities encased in an extracellular matrix composed of DNA, bacterial polysaccharides and proteins, which are up to 1000-fold more antibiotic resistant than planktonic cultures. To date, extracellular DNA has been shown to function as a structural support to maintain Pseudomonas aeruginosa biofilm architecture. Here we show that DNA is a multifaceted component of P. aeruginosa biofilms. At physiologically relevant concentrations, extracellular DNA has antimicrobial activity, causing cell lysis by chelating cations that stabilize lipopolysaccharide (LPS and the outer membrane (OM. DNA-mediated killing occurred within minutes, as a result of perturbation of both the outer and inner membrane (IM and the release of cytoplasmic contents, including genomic DNA. Sub-inhibitory concentrations of DNA created a cation-limited environment that resulted in induction of the PhoPQ- and PmrAB-regulated cationic antimicrobial peptide resistance operon PA3552-PA3559 in P. aeruginosa. Furthermore, DNA-induced expression of this operon resulted in up to 2560-fold increased resistance to cationic antimicrobial peptides and 640-fold increased resistance to aminoglycosides, but had no effect on beta-lactam and fluoroquinolone resistance. Thus, the presence of extracellular DNA in the biofilm matrix contributes to cation gradients, genomic DNA release and inducible antibiotic resistance. DNA-rich environments, including biofilms and other infection sites like the CF lung, are likely the in vivo environments where extracellular pathogens such as P. aeruginosa encounter cation limitation.

  17. Both Chromosome Decondensation and Condensation Are Dependent on DNA Replication in C. elegans Embryos.

    Science.gov (United States)

    Sonneville, Remi; Craig, Gillian; Labib, Karim; Gartner, Anton; Blow, J Julian

    2015-07-21

    During cell division, chromatin alternates between a condensed state to facilitate chromosome segregation and a decondensed form when DNA replicates. In most tissues, S phase and mitosis are separated by defined G1 and G2 gap phases, but early embryogenesis involves rapid oscillations between replication and mitosis. Using Caenorhabditis elegans embryos as a model system, we show that chromosome condensation and condensin II concentration on chromosomal axes require replicated DNA. In addition, we found that, during late telophase, replication initiates on condensed chromosomes and promotes the rapid decondensation of the chromatin. Upon replication initiation, the CDC-45-MCM-GINS (CMG) DNA helicase drives the release of condensin I complexes from chromatin and the activation or displacement of inactive MCM-2-7 complexes, which together with the nucleoporin MEL-28/ELYS tethers condensed chromatin to the nuclear envelope, thereby promoting chromatin decondensation. Our results show how, in an early embryo, the chromosome-condensation cycle is functionally linked with DNA replication.

  18. Lamellar cationic lipid-DNA complexes from lipids with a strong preference for planar geometry: A Minimal Electrostatic Model.

    Science.gov (United States)

    Perico, Angelo; Manning, Gerald S

    2014-11-01

    We formulate and analyze a minimal model, based on condensation theory, of the lamellar cationic lipid (CL)-DNA complex of alternately charged lipid bilayers and DNA monolayers in a salt solution. Each lipid bilayer, composed by a random mixture of cationic and neutral lipids, is assumed to be a rigid uniformly charged plane. Each DNA monolayer, located between two lipid bilayers, is formed by the same number of parallel DNAs with a uniform separation distance. For the electrostatic calculation, the model lipoplex is collapsed to a single plane with charge density equal to the net lipid and DNA charge. The free energy difference between the lamellar lipoplex and a reference state of the same number of free lipid bilayers and free DNAs, is calculated as a function of the fraction of CLs, of the ratio of the number of CL charges to the number of negative charges of the DNA phosphates, and of the total number of planes. At the isoelectric point the free energy difference is minimal. The complex formation, already favoured by the decrease of the electrostatic charging free energy, is driven further by the free energy gain due to the release of counterions from the DNAs and from the lipid bilayers, if strongly charged. This minimal model compares well with experiment for lipids having a strong preference for planar geometry and with major features of more detailed models of the lipoplex.

  19. DNA induced sequestration of a bioactive cationic fluorophore from the lipid environment: A spectroscopic investigation.

    Science.gov (United States)

    Ghosh, Saptarshi; Kundu, Pronab; Chattopadhyay, Nitin

    2016-01-01

    The effect of calf-thymus DNA (ctDNA) on the lipid bound probe, formed by the cationic phenazinium dye phenosafranin (PSF) and the anionic lipid dimyristoyl-L-α-phosphatidylglycerol (DMPG), has been unearthed exploiting various spectroscopic techniques. Steady state and time-resolved fluorometric studies and measurements of circular dichroism and DNA helix melting temperature reveal that in the presence of DNA the probe is dislodged from the lipid environment and gets intercalated within the DNA helix. The work qualitatively illustrates that the anionic lipid can be used as a potential nanocarrier for delivering the cationic drugs to the most relevant biomacromolecular target, DNA.

  20. Cationic comb-type copolymers for DNA analysis

    Science.gov (United States)

    Kim, Won Jong; Sato, Yuichi; Akaike, Toshihiro; Maruyama, Atsushi

    2003-12-01

    Genetic diagnoses, such as single nucleotide polymorphism (SNP) typing, allow elucidation of gene-based physiological differences, such as susceptibility to diseases and response to drugs, among individuals. Many detection technologies, including allele-specific hybridization, allele-specific primer extension and oligonucleotide ligation, are being used to discriminate SNP alleles. These methods still have many unsolved practical issues. In general they require adequate and specific hybridizations of primer or probe DNAs with target DNAs. This frequently needs optimization of the probe/primer structures and operating conditions. In nature, highly homology-sensitive hybridization is assisted by a nucleic acid chaperone that reduces the energy barrier associated with breakage and reassociation of nucleic base pairs. Here we report a simple, quick, precise but enzyme-free method for SNP analysis. The method uses cationic comb-type copolymers (CCCs) producing high nucleic acid chaperone activities. A single-base mismatch in 20-mer DNA can be detected within a few minutes at ambient temperatures (25-37 °C). Even without careful optimization processes, the method has the sensitivity to detect the mismatches causing subtle changes (ΔTm ~ 1 °C) in duplex thermal stability. CCCs may have various bioanalytical applications where precise hybridization of nucleic acids is needed.

  1. Binding of DNA by a dinitro-diester calix[4]arene: denaturation and condensation of DNA.

    Science.gov (United States)

    Ostos, F J; Lebron, J A; Moyá, M L; Deasy, M; López-Cornejo, P

    2015-03-01

    A study of a dinitro-diester calix[4]arene (5,17-(3-nitrobenzylideneamino)-11,23-di-tert-butyl-25,27-diethoxycarbonyl methyleneoxy-26,28-dihydroxycalix[4]arene) interaction with calf-thymus DNA was carried out using several techniques. The measurements were done at various molar ratios X=[calixarene]/[DNA]. Results show diverse changes in the DNA conformation depending on the X value. Thus, at low macrocycle concentrations, the calixarene binds to the polynucleotide. This interaction, mainly in groove mode, weakens the hydrogen bonds between base pairs of the helix inducing denaturation of the double strands, as well as condensation of the macromolecule, from an extended coil state to a globular state. An opposite effect is observed at X molar ratios higher than 0.07. The de-condensation of DNA happens, that is, the transition from a compact state to a more extended conformation, probably due to the stacking of calixarene molecules in the solution. Results also show the importance of making a proper choice of the system under consideration.

  2. Immobilization and condensation of DNA with 3-aminopropyltriethoxysilane studied by atomic force microscopy.

    Science.gov (United States)

    Liu, Z; Li, Z; Zhou, H; Wei, G; Song, Y; Wang, L

    2005-06-01

    We used different methods to modify a mica surface with 3-aminopropyltriethoxysilane (APTES), and then used it as substrate to immobilize DNA for atomic force microscopy (AFM) observation. The evaporation method and solution modifying method were investigated and evaluated. The solution modifying method was found to be relatively simple and effective. Using an APTES solution-modified mica surface, DNA immobilization appeared more reproducible and it could be imaged in liquid. The mixed solution of APTES and DNA was dropped directly onto the mica surface for AFM imaging. We found that DNA can condense in APTES water solutions. Toroids, rods and intermediate structures of condensation were captured by AFM.

  3. Condensation of Plasmid DNA Enhances Mitochondrial Association in Skeletal Muscle Following Hydrodynamic Limb Vein Injection

    Directory of Open Access Journals (Sweden)

    Yukari Yasuzaki

    2014-08-01

    Full Text Available Mitochondrial gene therapy and diagnosis have the potential to provide substantial medical benefits. However, the utility of this approach has not yet been realized because the technology available for mitochondrial gene delivery continues to be a bottleneck. We previously reported on mitochondrial gene delivery in skeletal muscle using hydrodynamic limb vein (HLV injection. HLV injection, a useful method for nuclear transgene expression, involves the rapid injection of a large volume of naked plasmid DNA (pDNA. Moreover, the use of a condensed form of pDNA enhances the nuclear transgene expression by the HLV injection. The purpose of this study was to compare naked pDNA and condensed pDNA for mitochondrial association in skeletal muscle, when used in conjunction with HLV injection. PCR analysis showed that the use of condensed pDNA rather than naked pDNA resulted in a more effective mitochondrial association with pDNA, suggesting that the physicochemical state of pDNA plays a key role. Moreover, no mitochondrial toxicities in skeletal muscle following the HLV injection of condensed pDNA were confirmed, as evidenced by cytochrome c oxidase activity and mitochondrial membrane potential. These findings have the potential to contribute to the development for in vivo mitochondrial gene delivery system.

  4. Sensing Conformational Changes in DNA upon Ligand Binding Using QCM-D. Polyamine Condensation and Rad51 Extension of DNA Layers

    KAUST Repository

    Sun, Lu

    2014-10-16

    © 2014 American Chemical Society. Biosensors, in which binding of ligands is detected through changes in the optical or electrochemical properties of a DNA layer confined to the sensor surface, are important tools for investigating DNA interactions. Here, we investigate if conformational changes induced in surface-attached DNA molecules upon ligand binding can be monitored by the quartz crystal microbalance with dissipation (QCM-D) technique. DNA duplexes containing 59-184 base pairs were formed on QCM-D crystals by stepwise assembly of synthetic oligonucleotides of designed base sequences. The DNA films were exposed to the cationic polyamines spermidine and spermine, known to condense DNA molecules in bulk experiments, or to the recombination protein Rad51, known to extend the DNA helix. The binding and dissociation of the ligands to the DNA films were monitored in real time by measurements of the shifts in resonance frequency (Δf) and in dissipation (ΔD). The QCM-D data were analyzed using a Voigt-based model for the viscoelastic properties of polymer films in order to evaluate how the ligands affect thickness and shear viscosity of the DNA layer. Binding of spermine shrinks all DNA layers and increases their viscosity in a reversible fashion, and so does spermidine, but to a smaller extent, in agreement with its lower positive charge. SPR was used to measure the amount of bound polyamines, and when combined with QCM-D, the data indicate that the layer condensation leads to a small release of water from the highly hydrated DNA films. The binding of Rad51 increases the effective layer thickness of a 59bp film, more than expected from the know 50% DNA helix extension. The combined results provide guidelines for a QCM-D biosensor based on ligand-induced structural changes in DNA films. The QCM-D approach provides high discrimination between ligands affecting the thickness and the structural properties of the DNA layer differently. The reversibility of the film

  5. Glom Is a Novel Mitochondrial DNA Packaging Protein in Physarum polycephalum and Causes Intense Chromatin Condensation without Suppressing DNA Functions

    Science.gov (United States)

    Sasaki, Narie; Kuroiwa, Haruko; Nishitani, Chikako; Takano, Hiroyoshi; Higashiyama, Tetsuya; Kobayashi, Tamaki; Shirai, Yuki; Sakai, Atsushi; Kawano, Shigeyuki; Murakami-Murofushi, Kimiko; Kuroiwa, Tsuneyoshi

    2003-01-01

    Mitochondrial DNA (mtDNA) is packed into highly organized structures called mitochondrial nucleoids (mt-nucleoids). To understand the organization of mtDNA and the overall regulation of its genetic activity within the mt-nucleoids, we identified and characterized a novel mtDNA packaging protein, termed Glom (a protein inducing agglomeration of mitochondrial chromosome), from highly condensed mt-nucleoids of the true slime mold, Physarum polycephalum. This protein could bind to the entire mtDNA and package mtDNA into a highly condensed state in vitro. Immunostaining analysis showed that Glom specifically localized throughout the mt-nucleoid. Deduced amino acid sequence revealed that Glom has a lysine-rich region with proline-rich domain in the N-terminal half and two HMG boxes in C-terminal half. Deletion analysis of Glom revealed that the lysine-rich region was sufficient for the intense mtDNA condensation in vitro. When the recombinant Glom proteins containing the lysine-rich region were expressed in Escherichia coli, the condensed nucleoid structures were observed in E. coli. Such in vivo condensation did not interfere with transcription or replication of E. coli chromosome and the proline-rich domain was essential to keep those genetic activities. The expression of Glom also complemented the E. coli mutant lacking the bacterial histone-like protein HU and the HMG-boxes region of Glom was important for the complementation. Our results suggest that Glom is a new mitochondrial histone-like protein having a property to cause intense DNA condensation without suppressing DNA functions. PMID:12960433

  6. DNA-Accelerated Catalysis of Carbene-Transfer Reactions by a DNA/Cationic Iron Porphyrin Hybrid

    NARCIS (Netherlands)

    Rioz-Martínez, Ana; Oelerich, Jens; Ségaud, Nathalie; Roelfes, Gerard

    2016-01-01

    A novel DNA-based hybrid catalyst comprised of salmon testes DNA and an iron(III) complex of a cationic meso-tetrakis(N-alkylpyridyl)porphyrin was developed. When the N-methyl substituents were placed at the ortho position with respect to the porphyrin ring, high reactivity in catalytic

  7. Evidence of interlipidic ion-pairing in anion-induced DNA release from cationic amphiphile-DNA complexes. Mechanistic implications in transfection.

    Science.gov (United States)

    Bhattacharya, S; Mandal, S S

    1998-05-26

    Complex formation of DNA with a number of cationic amphiphiles has been examined using fluorescence, gel electrophoresis, and chemical nuclease digestion. Here we have addressed the status of both DNA and lipid upon complexation with each other. DNA upon binding with cationic amphiphiles changes its structure in such a way that it loses the ability to intercalate and becomes resistant to nuclease digestion. Fluorescence anisotropy measurements due to 1, 6-diphenylhexatriene (DPH) doped in cationic liposomes demonstrated that upon complexation with DNA, the resulting complexes still retain lamellar organizations with modest enhancement in thermal stabilities. The lipid-DNA complexation is most effective only when the complexation was carried out at or around the phase transition temperatures of the cationic lipid employed in the complexation with DNA. The release of DNA from cationic lipid-DNA complexes could be induced by several anionic additives. Determination of fluorescence anisotropies (due to DPH) as a function of temperature clearly demonstrates that the addition of equivalent amounts of anionic amphiphile into cationic lipid-DNA complexes leads to the ion-pairing of the amphiphiles, the melting profiles of which are virtually the same as those obtained in the absence of DNA. In this process DNA gets released from its complexes with cationic lipids and regains its natural intercalation ability, movement, and staining ability on agarose gel and also the sensitivities toward nuclease digestion. This clearly suggests that combination of ion-pairing and hydrophobic interactions between cationic and anionic amphiphiles is stronger than the electrostatic forces involved in the cationic lipid-DNA complexation. It is further revealed that the DNA release by anions is most efficient from the cationic lipid-DNA complexes at or around the Tm of the cationic lipid used in DNA complexation. This explains why more effective DNA delivery is achieved with cationic lipids

  8. Characterisation of LMD virus-like nanoparticles self-assembled from cationic liposomes, adenovirus core peptide mu and plasmid DNA.

    Science.gov (United States)

    Tagawa, T; Manvell, M; Brown, N; Keller, M; Perouzel, E; Murray, K D; Harbottle, R P; Tecle, M; Booy, F; Brahimi-Horn, M C; Coutelle, C; Lemoine, N R; Alton, E W F W; Miller, A D

    2002-05-01

    Liposome:mu:DNA (LMD) is a ternary nucleic acid delivery system built around the mu peptide associated with the condensed core complex of the adenovirus. LMD is prepared by precondensing plasmid DNA (D) with mu peptide (M) in a 1:0.6 (w/w) ratio and then combining these mu:DNA (MD) complexes with extruded cationic liposomes (L) resulting in a final lipid:mu:DNA ratio of 12:0.6:1 (w/w/w). Correct buffer conditions, reagent concentrations and rates of mixing are all crucial to success. However, once optimal conditions are established, homogeneous LMD particles (120 +/- 30 nm) will result that each appear to comprise an MD particle encapsulated within a cationic bilammellar liposome. LMD particles can be formulated reproducibly, they are amenable to long-term storage (>1 month) at -80 degrees C and are stable to aggregation at a plasmid DNA concentration up to 5 mg/ml (15 mM nucleotide concentration). Furthermore, LMD transfections are significantly more time and dose efficient in vitro than cationic liposome-plasmid DNA (LD) transfections. Transfection times as short as 10 min and plasmid DNA doses as low as 0.001 microg/well result in significant gene expression. LMD transfections will also take place in the presence of biological fluids (eg up to 100% serum) giving 15-25% the level of gene expression observed in the absence of serum. Results from confocal microscopy experiments using fluorescent-labelled LMD particles suggest that endocytosis is not a significant barrier to LMD transfection, although the nuclear membrane still is. We also confirm that topical lung transfection in vivo by LMD is at least equal in absolute terms with transfection mediated by GL-67:DOPE:DMPE-PEG(5000) (1:2:0.05 m/m/m), an accepted 'gold-standard' non-viral vector system for topical lung transfection, and is in fact at least six-fold more dose efficient. All these features make LMD an important new non-viral vector platform system from which to derive tailor-made non-viral delivery

  9. Improved DNA condensation, stability, and transfection with alkyl sulfonyl-functionalized PAMAM G2

    Energy Technology Data Exchange (ETDEWEB)

    Rata-Aguilar, Azahara, E-mail: azahara@ugr.es; Maldonado-Valderrama, Julia; Jódar-Reyes, Ana Belén; Ortega-Vinuesa, Juan Luis [University of Granada, Biocolloid and Fluid Physics Group, Department of Applied Physics (Spain); Santoyo-Gonzalez, Francisco [University of Granada, Organic Chemistry Department, Institute of Biotechnology (Spain); Martín-Rodríguez, Antonio [University of Granada, Biocolloid and Fluid Physics Group, Department of Applied Physics (Spain)

    2015-04-15

    In this work, we have used a second-generation PAMAM grafted with octadecyl sulfonyl chains to condense plasmid DNA. The influence of this modification at different levels was investigated by comparison with original PAMAM G2. The condensation process and temporal stability of the complexes was studied with DLS, finding that the aliphatic chains influence DNA compaction via hydrophobic forces and markedly improve the formation and temporal stability of a single populated system with a hydrodynamic diameter below 100 nm. Interaction with a cell membrane model was also evaluated with a pendant drop tensiometer, resulting in further incorporation of the C18-PAMAM dendriplexes onto the interface. The improvement observed in transfection with our C18 grafted PAMAM is ascribed to the size, stability, and interfacial behavior of the complexes, which in turn are consequence of the DNA condensation process and the interactions involved.

  10. Both Chromosome Decondensation and Condensation Are Dependent on DNA Replication in C. elegans Embryos

    Directory of Open Access Journals (Sweden)

    Remi Sonneville

    2015-07-01

    Full Text Available During cell division, chromatin alternates between a condensed state to facilitate chromosome segregation and a decondensed form when DNA replicates. In most tissues, S phase and mitosis are separated by defined G1 and G2 gap phases, but early embryogenesis involves rapid oscillations between replication and mitosis. Using Caenorhabditis elegans embryos as a model system, we show that chromosome condensation and condensin II concentration on chromosomal axes require replicated DNA. In addition, we found that, during late telophase, replication initiates on condensed chromosomes and promotes the rapid decondensation of the chromatin. Upon replication initiation, the CDC-45-MCM-GINS (CMG DNA helicase drives the release of condensin I complexes from chromatin and the activation or displacement of inactive MCM-2–7 complexes, which together with the nucleoporin MEL-28/ELYS tethers condensed chromatin to the nuclear envelope, thereby promoting chromatin decondensation. Our results show how, in an early embryo, the chromosome-condensation cycle is functionally linked with DNA replication.

  11. Recharging cationic DNA complexes with highly charged polyanions for in vitro and in vivo gene delivery.

    Science.gov (United States)

    Trubetskoy, V S; Wong, S C; Subbotin, V; Budker, V G; Loomis, A; Hagstrom, J E; Wolff, J A

    2003-02-01

    The intravenous delivery of plasmid DNA complexed with either cationic lipids (CL) or polyethyleneimine (PEI) enables high levels of foreign gene expression in lung. However, these cationic DNA complexes cause substantial toxicity. The present study found that the inclusion of polyacrylic acid (pAA) with DNA/polycation and DNA/CL complexes prevented the serum inhibition of the transfection complexes in cultured cells. The mechanism mediating this increase seems to involve both particle size enlargement due to flocculation and electrostatic shielding from opsonizing serum proteins. The use of pAA also increased the levels of lung expression in mice in vivo substantially above the levels achieved with just binary complexes of DNA and linear PEI (lPEI) or CL and reduced their toxicity. Also, the use of a "chaser" injection of pAA 30 min after injection of the ternary DNA/lPEI/pAA complexes further aided this effort to reduce toxicity while not affecting foreign gene expression. By optimizing the amount of pAA, lPEI, and DNA within the ternary complexes and using the "chaser" injection, substantial levels of lung expression were obtained while avoiding adverse effects in lung or liver. These developments will aid the use of cationic DNA complexes in animals and for eventual human gene therapy.

  12. Synthesis and characterization of homopolymers bearing acid-cleavable cationic side-chains for pH-modulated release of DNA.

    Science.gov (United States)

    Xu, Zhangyan; Lai, Junping; Tang, Rupei; Ji, Weihang; Wang, Rui; Wang, Jun; Wang, Chun

    2014-07-01

    A new type of homopolymers, PMAOE, bearing acid-cleavable cationic side-chains is synthesized and characterized. PMAOE is obtained via free radical polymerization, and they could efficiently bind and condense plasmid DNA at neutral pH. The strength of DNA binding is dependent on the length of PMAOE chains. NMR analysis reveals that hydrolysis of the ortho ester group of PMAOE follows an exocyclic mechanism and the rate of hydrolysis is much accelerated at mildly acidic pH, leading to accelerated disruption of polyplexes and release of DNA in mildly acidic environment. PMAOE is not toxic to cultured NIH 3T3 and COS-7 cells measured by MTT. This study demonstrates a unique mechanism of achieving pH-modulated binding and release of DNA from polymers with potential applications for gene delivery.

  13. Arginine-based cationic liposomes for efficient in vitro plasmid DNA delivery with low cytotoxicity

    Directory of Open Access Journals (Sweden)

    Sarker SR

    2013-04-01

    Full Text Available Satya Ranjan Sarker, Yumiko Aoshima, Ryosuke Hokama, Takafumi Inoue, Keitaro Sou, Shinji Takeoka Department of Life Science and Medical Bioscience, Graduate School of Advanced Science and Engineering, Waseda University (TWIns, Tokyo, Japan Background: Currently available gene delivery vehicles have many limitations such as low gene delivery efficiency and high cytotoxicity. To overcome these drawbacks, we designed and synthesized two cationic lipids comprised of n-tetradecyl alcohol as the hydrophobic moiety, 3-hydrocarbon chain as the spacer, and different counterions (eg, hydrogen chloride [HCl] salt or trifluoroacetic acid [TFA] salt in the arginine head group. Methods: Cationic lipids were hydrated in 4-(2-hydroxyethyl-1-piperazineethanesulfonic acid (HEPES buffer to prepare cationic liposomes and characterized in terms of their size, zeta potential, phase transition temperature, and morphology. Lipoplexes were then prepared and characterized in terms of their size and zeta potential in the absence or presence of serum. The morphology of the lipoplexes was determined using transmission electron microscopy and atomic force microscopy. The gene delivery efficiency was evaluated in neuronal cells and HeLa cells and compared with that of lysine-based cationic assemblies and Lipofectamine™ 2000. The cytotoxicity level of the cationic lipids was investigated and compared with that of Lipofectamine™ 2000. Results: We synthesized arginine-based cationic lipids having different counterions (ie, HCl-salt or TFA-salt that formed cationic liposomes of around 100 nm in size. In the absence of serum, lipoplexes prepared from the arginine-based cationic liposomes and plasmid (p DNA formed large aggregates and attained a positive zeta potential. However, in the presence of serum, the lipoplexes were smaller in size and negative in zeta potential. The morphology of the lipoplexes was vesicular. Arginine-based cationic liposomes with HCl-salt showed the

  14. Mathematical relationships among DNA supercoiling, cation concentration, and temperature for prokaryotic transcription.

    Science.gov (United States)

    Wang, J Y

    1998-08-01

    DNA twist has been proposed to affect transcription from some promoters of Escherichia coli, but involvement of twist has been difficult to test because it cannot be measured in transcription reaction mixtures. However, changes in other factors affect both DNA twist and transcription. These parameters are expected to be related when maximum transcription initiation is considered. In the present work, mathematical relationships among supercoiling, cation concentration, and temperature are derived for prokaryotic transcription initiation. The relationships indicate that as DNA becomes more negatively supercoiled, maximal initiation occurs at a higher cation concentration and at a lower temperature. For example, when superhelical density becomes more negative by 0.0025, a 1.6-fold increase in potassium concentration is predicted to be required to maintain transcription initiation at its maximum rate. Experimental verification of the relationships should provide a useful test of the idea that transcription initiation is sensitive to DNA twist.

  15. Interaction between cationic agents and small interfering RNA and DNA molecules

    Science.gov (United States)

    Unksov, I. N.; Slita, A. V.; Petrova, A. V.; Pereviazko, I.; Bakulev, V. M.; Rolich, V. I.; Bondarenko, A. B.; Kasyanenko, N. A.

    2016-11-01

    Azobenzene containing surfactant AzoTAB was used for investigation of binding in cationic- agent + nucleic acid in NaCl salt aqueous solutions. Two nucleic acids, macromolecular DNA and small interfering RNA, were examined upon the interaction with the surfactant. For DNA the interaction was studied using spectral methods and the methods of viscometry and flow birefringence measurement. For siRNA the possibility of surfactant-based delivery was checked in vitro.

  16. PEGylation enhances tumor targeting of plasmid DNA by an artificial cationized protein with repeated RGD sequences, Pronectin.

    Science.gov (United States)

    Hosseinkhani, Hossein; Tabata, Yasuhiko

    2004-05-31

    The objective of this study is to investigate feasibility of a non-viral gene carrier with repeated RGD sequences (Pronectin F+) in tumor targeting for gene expression. The Pronectin F+ was cationized by introducing spermine (Sm) to the hydroxyl groups to allow to polyionically complex with plasmid DNA. The cationized Pronectin F+ prepared was additionally modified with poly(ethylene glycol) (PEG) molecules which have active ester and methoxy groups at the terminal, to form various PEG-introduced cationized Pronectin F+. The cationized Pronectin F+ with or without PEGylation at different extents was mixed with a plasmid DNA of LacZ to form respective cationized Pronectin F+-plasmid DNA complexes. The plasmid DNA was electrophoretically complexed with cationized Pronectin F+ and PEG-introduced cationized Pronectin F+, irrespective of the PEGylation extent, although the higher N/P ratio of complexes was needed for complexation with the latter Pronectin F+. The molecular size and zeta potential measurements revealed that the plasmid DNA was reduced in size to about 250 nm and the charge was changed to be positive by the complexation with cationized Pronectin F+. For the complexation with PEG-introduced cationized Pronectin F+, the charge of complex became neutral being almost 0 mV with the increasing PEGylation extents, while the molecular size was similar to that of cationized Pronectin F+. When cationized Pronectin F+-plasmid DNA complexes with or without PEGylation were intravenously injected to mice carrying a subcutaneous Meth-AR-1 fibrosarcoma mass, the PEG-introduced cationized Pronectin F+-plasmid DNA complex specifically enhanced the level of gene expression in the tumor, to a significantly high extent compared with the cationized Pronectin F+-plasmid DNA complexes and free plasmid DNA. The enhanced level of gene expression depended on the percentage of PEG introduced, the N/P ratio, and the plasmid DNA dose. A fluorescent microscopic study revealed that the

  17. Preparation and Characterization of Cationic PLA-PEG Nanoparticles for Delivery of Plasmid DNA

    Science.gov (United States)

    Zou, Weiwei; Liu, Chunxi; Chen, Zhijin; Zhang, Na

    2009-09-01

    The purpose of the present work was to formulate and evaluate cationic poly(lactic acid)-poly(ethylene glycol) (PLA-PEG) nanoparticles as novel non-viral gene delivery nano-device. Cationic PLA-PEG nanoparticles were prepared by nanoprecipitation method. The gene loaded nanoparticles were obtained by incubating the report gene pEGFP with cationic PLA-PEG nanoparticles. The physicochemical properties (e.g., morphology, particle size, surface charge, DNA binding efficiency) and biological properties (e.g., integrity of the released DNA, protection from nuclease degradation, plasma stability, in vitro cytotoxicity, and in vitro transfection ability in Hela cells) of the gene loaded PLA-PEG nanoparticles were evaluated, respectively. The obtained cationic PLA-PEG nanoparticles and gene loaded nanoparticles were both spherical in shape with average particle size of 89.7 and 128.9 nm, polydispersity index of 0.185 and 0.161, zeta potentials of +28.9 and +16.8 mV, respectively. The obtained cationic PLA-PEG nanoparticles with high binding efficiency (>95%) could protect the loaded DNA from the degradation by nuclease and plasma. The nanoparticles displayed sustained-release properties in vitro and the released DNA maintained its structural and functional integrity. It also showed lower cytotoxicity than Lipofectamine 2000 and could successfully transfect gene into Hela cells even in presence of serum. It could be concluded that the established gene loaded cationic PLA-PEG nanoparticles with excellent properties were promising non-viral nano-device, which had potential to make cancer gene therapy achievable.

  18. Preparation and Characterization of Cationic PLA-PEG Nanoparticles for Delivery of Plasmid DNA

    Directory of Open Access Journals (Sweden)

    Zou Weiwei

    2009-01-01

    Full Text Available Abstract The purpose of the present work was to formulate and evaluate cationic poly(lactic acid-poly(ethylene glycol (PLA-PEG nanoparticles as novel non-viral gene delivery nano-device. Cationic PLA-PEG nanoparticles were prepared by nanoprecipitation method. The gene loaded nanoparticles were obtained by incubating the report gene pEGFP with cationic PLA-PEG nanoparticles. The physicochemical properties (e.g., morphology, particle size, surface charge, DNA binding efficiency and biological properties (e.g., integrity of the released DNA, protection from nuclease degradation, plasma stability, in vitro cytotoxicity, and in vitro transfection ability in Hela cells of the gene loaded PLA-PEG nanoparticles were evaluated, respectively. The obtained cationic PLA-PEG nanoparticles and gene loaded nanoparticles were both spherical in shape with average particle size of 89.7 and 128.9 nm, polydispersity index of 0.185 and 0.161, zeta potentials of +28.9 and +16.8 mV, respectively. The obtained cationic PLA-PEG nanoparticles with high binding efficiency (>95% could protect the loaded DNA from the degradation by nuclease and plasma. The nanoparticles displayed sustained-release properties in vitro and the released DNA maintained its structural and functional integrity. It also showed lower cytotoxicity than Lipofectamine 2000 and could successfully transfect gene into Hela cells even in presence of serum. It could be concluded that the established gene loaded cationic PLA-PEG nanoparticles with excellent properties were promising non-viral nano-device, which had potential to make cancer gene therapy achievable.

  19. Binding interaction of cationic phenazinium dyes with calf thymus DNA: a comparative study.

    Science.gov (United States)

    Sarkar, Deboleena; Das, Paramita; Basak, Soumen; Chattopadhyay, Nitin

    2008-07-31

    Absorption, steady-state fluorescence, steady-state fluorescence anisotropy, and intrinsic and induced circular dichroism (CD) have been exploited to explore the binding of calf thymus DNA (ctDNA) with three cationic phenazinium dyes, viz., phenosafranin (PSF), safranin-T (ST), and safranin-O (SO). The absorption and fluorescence spectra of all the three dyes reflect significant modifications upon interaction with the DNA. A comparative study of the dyes with respect to modification of fluorescence and fluorescence anisotropy upon binding, effect of urea, iodide-induced fluorescence quenching, and CD measurements reveal that the dyes bind to the ctDNA principally in an intercalative fashion. The effect of ionic strength indicates that electrostatic attraction between the cationic dyes and ctDNA is also an important component of the dye-DNA interaction. Intrinsic and induced CD studies help to assess the structural effects of dyes binding to DNA and confirm the intercalative mode of binding as suggested by fluorescence and other studies. Finally it is proposed that dyes with bulkier substitutions are intercalated into the DNA to a lesser extent.

  20. Isothermal titration calorimetric analysis of the interaction between cationic lipids and plasmid DNA.

    Science.gov (United States)

    Lobo, B A; Davis, A; Koe, G; Smith, J G; Middaugh, C R

    2001-02-01

    The effects of buffer and ionic strength upon the enthalpy of binding between plasmid DNA and a variety of cationic lipids used to enhance cellular transfection were studied using isothermal titration calorimetry at 25.0 degrees C and pH 7.4. The cationic lipids DOTAP (1,2-dioleoyl-3-trimethyl ammonium propane), DDAB (dimethyl dioctadecyl ammonium bromide), DOTAP:cholesterol (1:1), and DDAB:cholesterol (1:1) bound endothermally to plasmid DNA with a negligible proton exchange with buffer. In contrast, DOTAP: DOPE (L-alpha-dioleoyl phosphatidyl ethanolamine) (1:1) and DDAB:DOPE (1:1) liposomes displayed a negative enthalpy and a significant uptake of protons upon binding to plasmid DNA at neutral pH. These findings are most easily explained by a change in the apparent pKa of the amino group of DOPE upon binding. Complexes formed by reverse addition methods (DNA into lipid) produced different thermograms, sizes, zeta potentials, and aggregation behavior, suggesting that structurally different complexes were formed in each titration direction. Titrations performed in both directions in the presence of increasing ionic strength revealed a progressive decrease in the heat of binding and an increase in the lipid to DNA charge ratio at which aggregation occurred. The unfavorable binding enthalpy for the cationic lipids alone and with cholesterol implies an entropy-driven interaction, while the negative enthalpies observed with DOPE-containing lipid mixtures suggest an additional contribution from changes in protonation of DOPE.

  1. Lipid Phases Eye View to Lipofection. Cationic Phosphatidylcholine Derivatives as Efficient DNA Carriers for Gene Delivery

    Directory of Open Access Journals (Sweden)

    Rumiana Koynova

    2008-01-01

    Full Text Available Efficient delivery of genetic material to cells is needed for tasks of utmost importance in laboratory and clinic, such as gene transfection and gene silencing. Synthetic cationic lipids can be used as delivery vehicles for nucleic acids and are now considered the most promising non-viral gene carriers. They form complexes (lipoplexes with the polyanionic nucleic acids. A critical obstacle for clinical application of the lipid-mediated DNA delivery (lipofection is its unsatisfactory efficiency for many cell types. Understanding the mechanism of lipid-mediated DNA delivery is essential for their successful application, as well as for rational design and synthesis of novel cationic lipoid compounds for enhanced gene delivery. According to the current understanding, the critical factor in lipid-mediated transfection is the structural evolution of lipoplexes within the cell, upon interacting and mixing with cellular lipids. In particular, recent studies with cationic phospha- tidylcholine derivatives showed that the phase evolution of lipoplex lipids upon interaction and mixing with membrane lipids appears to be decisive for transfection success: specifically, lamellar lipoplex formulations, which were readily susceptible to undergoing lamellar-nonlamellar (precisely lamellar-cubic phase transition upon mixing with cellular lipids, were found rather consistently associated with superior transfection potency, presumably as a result of facilitated DNA release subsequent to lipoplex fusion with the cellular membranes. Further, hydrophobic moiety of the cationic phospholipids was found able to strongly modulate liposomal gene delivery into primary human umbilical artery endothelial cells; superior activity was found for cationic phosphatidylcholine derivatives with two 14-carbon atom monounsaturated hydrocarbon chains, able to induce formation of cubic phase in membranes. Thus, understanding the lipoplex structure and the phase changes upon interacting

  2. Fingerprinting DNA oxidation processes: IR characterization of the 5-methyl-2'-deoxycytidine radical cation.

    Science.gov (United States)

    Bucher, Dominik B; Pilles, Bert M; Pfaffeneder, Toni; Carell, Thomas; Zinth, Wolfgang

    2014-02-24

    Methylated cytidine plays an important role as an epigenetic signal in gene regulation. Its oxidation products are assumed to be involved in active demethylation processes but also in damaging DNA. Here, we report the photochemical production of the 5-methyl-2'-deoxycytidine radical cation via a two-photon ionization process. The radical cation is detected by time-resolved IR spectroscopy and identified by band assignment using density functional theory calculations. Two final oxidation products are characterized with liquid chromatography coupled to mass spectrometry.

  3. Ternary nanoparticles composed of cationic solid lipid nanoparticles, protamine, and DNA for gene delivery

    Directory of Open Access Journals (Sweden)

    He SN

    2013-08-01

    Full Text Available Sai-Nan He,1 Yun-Long Li,1,2 Jing-Jing Yan,2 Wei Zhang,2 Yong-Zhong Du,2 He-Yong Yu,1 Fu-Qiang Hu,2 Hong Yuan21Women’s Hospital, 2College of Pharmaceutical Sciences, School of Medicine, Zhejiang University, Hangzhou, People’s Republic of ChinaBackground: The objective of this research was to design an effective gene delivery system composed of cationic solid lipid nanoparticles (SLNs, protamine, and Deoxyribonucleic acid DNA.Methods: Cationic SLNs were prepared using an aqueous solvent diffusion method with octadecylamine as the cationic lipid material. First, protamine was combined with DNA to form binary protamine/DNA nanoparticles, and the ternary nanoparticle gene delivery system was then obtained by combining binary protamine/DNA nanoparticles with cationic SLNs. The size, zeta potential, and ability of the binary and ternary nanoparticles to compact and protect DNA were characterized. The effect of octadecylamine content in SLNs and the SLNS/DNA ratios on transfection efficiency, cellular uptake and cytotoxicity of the ternary nanoparticles were also assessed using HEK293 cells.Results: When the weight ratio of protamine to DNA reached 1.5:1, the plasmid DNA could be effectively compacted and protected. The average hydrodynamic diameter of the ternary nanoparticles when combined with protamine increased from 188.50 ± 0.26 nm to 259.33 ± 3.44 nm, and the zeta potential increased from 25.50 ± 3.30 mV to 33.40 ± 2.80 mV when the weight ratio of SLNs to DNA increased from 16/3 to 80/3. The ternary nanoparticles showed high gene transfection efficiency compared with LipofectamineTM 2000/DNA nanoparticles. Several factors that might affect gene transfection efficiency, such as content and composition of SLNs, post-transfection time, and serum were examined. The ternary nanoparticles composed of SLNs with 15 wt% octadecylamine (50/3 weight ratio of SLNs to DNA showed the best transfection efficiency (26.13% ± 5.22% in the presence of

  4. Excessive Counterion Condensation on Immobilized ssDNA in Solutions of High Ionic Strength

    Science.gov (United States)

    Rant, Ulrich; Arinaga, Kenji; Fujiwara, Tsuyoshi; Fujita, Shozo; Tornow, Marc; Yokoyama, Naoki; Abstreiter, Gerhard

    2003-01-01

    We present experiments on the bias-induced release of immobilized, single-stranded (ss) 24-mer oligonucleotides from Au-surfaces into electrolyte solutions of varying ionic strength. Desorption is evidenced by fluorescence measurements of dye-labeled ssDNA. Electrostatic interactions between adsorbed ssDNA and the Au-surface are investigated with respect to 1), a variation of the bias potential applied to the Au-electrode; and 2), the screening effect of the electrolyte solution. For the latter, the concentration of monovalent salt in solution is varied from 3 to 1600 mM. We find that the strength of electric interaction is predominantly determined by the effective charge of the ssDNA itself and that the release of DNA mainly occurs before the electrochemical double layer has been established at the electrolyte/Au interface. In agreement with Manning's condensation theory, the measured desorption efficiency (ηrel) stays constant over a wide range of salt concentrations; however, as the Debye length is reduced below a value comparable to the axial charge spacing of the DNA, ηrel decreases substantially. We assign this effect to excessive counterion condensation on the DNA in solutions of high ionic strength. In addition, the relative translational diffusion coefficient of ssDNA in solution is evaluated for different salt concentrations. PMID:14645075

  5. Determination of the cationic amphiphilic drug-DNA binding mode and DNA-assisted fluorescence resonance energy transfer amplification.

    Science.gov (United States)

    Yaseen, Zahid; Banday, Abdul Rouf; Hussain, Mohammed Aamir; Tabish, Mohammad; Kabir-ud-Din

    2014-03-25

    Understanding the mechanism of drug-DNA binding is crucial for predicting the potential genotoxicity of drugs. Agarose gel electrophoresis, absorption, steady state fluorescence, and circular dichroism have been used in exploring the interaction of cationic amphiphilic drugs (CADs) such as amitriptyline hydrochloride (AMT), imipramine hydrochloride (IMP), and promethazine hydrochloride (PMT) with calf thymus or pUC19 DNA. Agarose gel electrophoresis assay, along with absorption and steady state fluorescence studies, reveal interaction between the CADs and DNA. A comparative study of the drugs with respect to the effect of urea, iodide induced quenching, and ethidium bromide (EB) exclusion assay reflects binding of CADs to the DNA primarily in an intercalative fashion. Circular dichroism data also support the intercalative mode of binding. Besides quenching, there is fluorescence exchange energy transfer (FRET) in between CADs and EB using DNA as a template.

  6. Novel cyclen-based linear polymer as a high-affinity binding material for DNA condensation

    Institute of Scientific and Technical Information of China (English)

    XIANG YongZhe; WANG Na; ZHANG Ji; LI Kun; ZHANG ZhongWei; LIN HongHui; YU XiaoQi

    2009-01-01

    A novel cyclen-based linear polyamine (POGEC) was designed and synthesized from the reaction be-tween 1,3-propanediol diglycidyl ether and 1,7-bis(diethoxyphosphory)-1,4,7,10-tetraazacyclod- odecane.High-affinity binding between POGEC and DNA was demonstrated by agarose gel electrophoresis and scanning electron microscopy (SEM). Moreover, the formed POGEC/DNA complex (termed polyplex) could be disassociated to release the free DNA through addition of the physiological concentration of NaCl solution. Fluorescence spectrum was used to measure the high-affinity binding and DNA con-densation capability of POGEC. Circular dichroism (CD) spectrum indicates that the DNA conformation did not change after binding to POEGC.

  7. Novel cyclen-based linear polymer as a high-affinity binding material for DNA condensation

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    A novel cyclen-based linear polyamine (POGEC) was designed and synthesized from the reaction between 1,3-propanediol diglycidyl ether and 1,7-bis(diethoxyphosphory)-1,4,7,10-tetraazacyclod-odecane. High-affinity binding between POGEC and DNA was demonstrated by agarose gel electrophoresis and scanning electron microscopy (SEM). Moreover,the formed POGEC/DNA complex (termed polyplex) could be disassociated to release the free DNA through addition of the physiological concentration of NaCl solution. Fluorescence spectrum was used to measure the high-affinity binding and DNA condensation capability of POGEC. Circular dichroism (CD) spectrum indicates that the DNA conformation did not change after binding to POEGC.

  8. Condensations of single DNA molecules induced by heptaplatin and its chiral isomer

    Science.gov (United States)

    Zhang, Hong-Yan; Liu, Yu-Ru; Li, Wei; Li, Hui; Dou, Shuo-Xing; Xie, Ping; Wang, Wei-Chi; Wang, Peng-Ye

    2014-08-01

    Heptaplatin is a third-generation platinum antitumor drug. It has a chiral isomer. We studied the interactions between the two isomers and DNA by using magnetic tweezers and atomic force microscopy (AFM) to investigate the effect of chiralities of the isomers on the interactions. We found that the extension curves and average condensation rates of DNA molecules incubated with heptaplatin were nearly the same as those incubated with its chiral isomer. In addition, the structures of DNA molecules incubated with heptaplatin were also similar to those incubated with its chiral isomer. These results indicate the difference in chirality of the two isomers does not induce different interactions of the isomers with DNA. Our study may facilitate the understanding of interactions of platinum complexes with DNA and the design of new antitumor platinum complexes.

  9. Microneedle-mediated transcutaneous immunization with plasmid DNA coated on cationic PLGA nanoparticles

    Science.gov (United States)

    Kumar, Amit; Wonganan, Piyanuch; Sandoval, Michael A.; Li, Xinran; Zhu, Saijie; Cui, Zhengrong

    2012-01-01

    Previously, it was shown that microneedle-mediated transcutaneous immunization with plasmid DNA can potentially induce a stronger immune response than intramuscular injection of the same plasmid DNA. In the present study, we showed that the immune responses induced by transcutaneous immunization by applying plasmid DNA onto a skin area pretreated with solid microneedles were significantly enhanced by coating the plasmid DNA on the surface of cationic nanoparticles. In addition, the net surface charge of the DNA-coated nanoparticles significantly affected their in vitro skin permeation and their ability to induce immune responses in vivo. Transcutaneous immunization with plasmid DNA-coated net positively charged anoparticles elicited a stronger immune response than with plasmid DNA-coated net negatively charged nanoparticles or by intramuscular immunization with plasmid DNA alone. Transcutaneous immunization with plasmid DNA-coated net positively charged nanoparticles induced comparable immune responses as intramuscular injection of them, but transcutaneous immunization was able to induce specific mucosal immunity and a more balanced T helper type 1 and type 2 response. The ability of the net positively charged DNA-coated nanoparticles to induce a strong immune response through microneedle-mediated transcutaneous immunization may be attributed to their ability to increase the expression of the antigen gene encoded by the plasmid and to more effectively stimulate the maturation of antigen-presenting cells. PMID:22921518

  10. Antibacterial effect of cationic porphyrazines and anionic phthalocyanine and their interaction with plasmid DNA

    Science.gov (United States)

    Hassani, Leila; Hakimian, Fatemeh; Safaei, Elham; Fazeli, Zahra

    2013-11-01

    Resistance to antibiotics is a public health issue and identification of new antibacterial agents is one of the most important goals of pharmacological research. Among the novel developed antibacterial agents, porphyrin complexes and their derivatives are ideal candidates for use in medical applications. Phthalocyanines differ from porphyrins by having nitrogen atoms link the individual pyrrol units. The aza analogues of the phthalocyanines (azaPcs) such as tetramethylmetalloporphyrazines are heterocyclic Pc analogues. In this investigation, interaction of an anionic phthalocyanine (Cu(PcTs)) and two cationic tetrapyridinoporphyrazines including [Cu(2,3-tmtppa)]4+ and [Cu(3,4-tmtppa)]4+ complexes with plasmid DNA was studied using spectroscopic and gel electrophoresis methods. In addition, antibacterial effect of the complexes against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria was investigated using dilution test method. The results indicated that both porphyrazines have significant antibacterial properties, but Cu(PcTs) has weak antibacterial effect. Compairing the binding of the phthalocyanine and the porphyrazines to DNA demonstrated that the interaction of cationic porphyrazines is stronger than the anionic phthalocyanine remarkably. The extent of hypochromicity and red shift of absorption spectra indicated preferential intercalation of the two porphyrazine into the base pairs of DNA helix. Gel electrophoresis result implied Cu(2,3-tmtppa) and Cu(3,4-tmtppa) are able to perform cleavage of the plasmid DNA. Consequently, DNA binding and cleavage might be one of the antibacterial mechanisms of the complexes.

  11. Cationic modified nucleic acids for use in DNA hairpins and parallel triplexes

    DEFF Research Database (Denmark)

    Bomholt, Niels; Filichev, Vyacheslav V; Pedersen, Erik Bjerregaard

    2011-01-01

    Non-nucleosidic DNA monomers comprising partially protonated amines at low pH have been designed and synthesized. The modifications were incorporated into DNA oligonucleotides via standard DNA phosphoramidite synthesis. The ability of cationic modifications to stabilize palindromic DNA hairpins...... and parallel triplexes were evaluated using gel electrophoresis, circular dichroism and thermal denaturation measurements. The non-nucleosidic modifications were found to increase the thermal stability of palindromic hairpins at pH 8.0 as compared with a nucleosidic tetraloop (TCTC). Incorporation...... of modifications at the 5'-end of a triplex forming oligonucleotide resulted in a significant increase in thermal stability at low pH when the modifications were placed as the 5'-dangling end....

  12. Cationic polymers for DNA origami coating - examining their binding efficiency and tuning the enzymatic reaction rates

    Science.gov (United States)

    Kiviaho, Jenny K.; Linko, Veikko; Ora, Ari; Tiainen, Tony; Järvihaavisto, Erika; Mikkilä, Joona; Tenhu, Heikki; Nonappa, Affc; Kostiainen, Mauri A.

    2016-06-01

    DNA origamis are fully tailored, programmable, biocompatible and readily functionalizable nanostructures that provide an excellent foundation for the development of sophisticated drug-delivery systems. However, the DNA origami objects suffer from certain drawbacks such as low cell-transfection rates and low stability. A great deal of studies on polymer-based transfection agents, mainly focusing on polyplex formation and toxicity, exists. In this study, the electrostatic binding between a brick-like DNA origami and cationic block-copolymers was explored. The effect of the polymer structure on the binding was investigated and the toxicity of the polymer-origami complexes evaluated. The study shows that all of the analyzed polymers had a suitable binding efficiency irrespective of the block structure. It was also observed that the toxicity of polymer-origami complexes was insignificant at the biologically relevant concentration levels. Besides brick-like DNA origamis, tubular origami carriers equipped with enzymes were also coated with the polymers. By adjusting the amount of cationic polymers that cover the DNA structures, we showed that it is possible to control the enzyme kinetics of the complexes. This work gives a starting point for further development of biocompatible and effective polycation-based block copolymers that can be used in coating different DNA origami nanostructures for various bioapplications.DNA origamis are fully tailored, programmable, biocompatible and readily functionalizable nanostructures that provide an excellent foundation for the development of sophisticated drug-delivery systems. However, the DNA origami objects suffer from certain drawbacks such as low cell-transfection rates and low stability. A great deal of studies on polymer-based transfection agents, mainly focusing on polyplex formation and toxicity, exists. In this study, the electrostatic binding between a brick-like DNA origami and cationic block-copolymers was explored. The

  13. Tuning backbones and side-chains of cationic conjugated polymers for optical signal amplification of fluorescent DNA detection.

    Science.gov (United States)

    Huang, Yan-Qin; Liu, Xing-Fen; Fan, Qu-Li; Wang, Lihua; Song, Shiping; Wang, Lian-Hui; Fan, Chunhai; Huang, Wei

    2009-06-15

    Three cationic conjugated polymers (CCPs) exhibiting different backbone geometries and charge densities were used to investigate how their conjugated backbone and side chain properties, together with the transitions of DNA amphiphilic properties, interplay in the CCP/DNA-C* (DNA-C*: fluorophore-labeled DNA) complexes to influence the optical signal amplification of fluorescent DNA detection based on Förster resonance energy transfer (FRET). By examining the FRET efficiencies to dsDNA-C* (dsDNA: double-stranded DNA) and ssDNA-C* (ssDNA: single-stranded DNA) for each CCP, twisted conjugated backbones and higher charge densities were proved to facilitate electrostatic attraction in CCP/dsDNA-C* complexes, and induced improved sensitivity to DNA hybridization. Especially, by using the CCP with twisted conjugated backbone and the highest charge density, a more than 7-fold higher efficiency of FRET to dsDNA-C* was found than to ssDNA-C*, indicating a high signal amplification for discriminating between dsDNA and ssDNA. By contrast, linear conjugated backbones and lower charge density were demonstrated to favor hydrophobic interactions in CCP/ssDNA-C* complexes. These findings provided guidelines for the design of novel sensitive CCP, which can be useful to recognize many other important DNA activities involving transitions of DNA amphiphilic properties like DNA hybridization, such as specific DNA binding with ions, some secondary or tertiary structural changes of DNA, and so forth.

  14. Development of a novel gene delivery scaffold utilizing colloidal gold-polyethylenimine conjugates for DNA condensation.

    Science.gov (United States)

    Ow Sullivan, M M; Green, J J; Przybycien, T M

    2003-10-01

    We have developed a novel gene delivery scaffold based on DNA plasmid condensation with colloidal gold/polyethylenimine conjugates. This scaffold system was designed to enable systematic study of the relationships between DNA complex physical properties and transfection efficiency. Using an enhanced green fluorescent protein-coding reporter plasmid and a Chinese hamster ovary cell line, we have measured the transfection efficiencies of our complexes using flow cytometry and their cytotoxicities using the trypan blue assay. We have also assayed complex particle morphologies using atomic force microscopy, photon correlation spectroscopy, and a novel plasmon absorbance peak position analysis. We achieved comparable rates of transfection relative to the commonly used polycationic condensation agents calcium phosphate and LipofectAMINE, with comparably low cytotoxicities. In addition, by manipulating colloidal gold concentration, we could partially decouple complex physical properties including charge ratio, size, DNA loading, and polyethylenimine concentration. Our morphological analyses showed that complexes with a diameter of a few hundred nanometers and a charge ratio of approximately 8 perform best in our transfection efficiency assays. The use of colloidal gold as a component in our delivery system provides a versatile system for manipulating complex properties and morphology as well as a convenient scaffold for planned ligand conjugation studies.

  15. Investigation of DNA-cationic bolaform surfactants interaction with different spacer length.

    Science.gov (United States)

    Sohrabi, Beheshteh; Khani, Vahid; Moosavi-Movahedi, Ali Akbar; Moradi, Parviz

    2013-10-01

    In this paper interaction of DNA with cationic bolaform surfactants is investigated. The structural formula for synthesized bolaforms is as follows: bolaform B1 with structural formula Br(-)(CH3)3N(+)(CH2)3N(+)(CH3)Br(-) and bolaform B2 with structural formula of Br(-)(CH3)3N(+)(CH2)12N(+)(CH3)Br(-). There are stronger electrostatic interactions in bolaform B1 due to shorter spacer length, while there are stronger hydrophobic interactions in bolaform B2 compared to bolaform B1 due to existence of 12 carbons in hydrocarbonic chain. The structure of bolaforms consists of two polar head groups which play important role in DNA compaction. Surface tension change in aqueous solution of bolaform surfactants is measured using tensiometer. Electrical conductivity of surfactants aqueous solution is examined with and without DNA. DNA compaction is tracked in the presence of bolaforms by dynamic light scattering (DLS) technique. Results of DLS indicate bolaforms with shorter spacer length (dominant electrostatic interactions) are more influential in compressing DNA compared to bolaforms with longer spacer length (stronger hydrophobic interactions). UV-vis and fluorescence spectroscopies specify the binding mechanism of bolaform surfactants to DNA.

  16. DNA Condensation by Partially Acetylated Poly(amido amine Dendrimers: Effects of Dendrimer Charge Density on Complex Formation

    Directory of Open Access Journals (Sweden)

    Ronald G. Larson

    2013-09-01

    Full Text Available The ability of poly(amido amine (or PAMAM dendrimers to condense semiflexible dsDNA and penetrate cell membranes gives them great potential in gene therapy and drug delivery but their high positive surface charge makes them cytotoxic. Here, we describe the effects of partial neutralization by acetylation on DNA condensation using light scattering, circular dichroism, and single molecule imaging of dendrimer-DNA complexes combed onto surfaces and tethered to those surfaces under flow. We find that DNA can be condensed by generation-five (G5 dendrimers even when the surface charges are more than 65% neutralized, but that such dendrimers bind negligibly when an end-tethered DNA is stretched in flow. We also find that when fully charged dendrimers are introduced by flow to end-tethered DNA, all DNA molecules become equally highly coated with dendrimers at a rate that becomes very fast at high dendrimer concentration, and that dendrimers remain bound during subsequent flow of dendrimer-free buffer. These results suggest that the presence of dendrimer-free DNA coexisting with dendrimer-bound DNA after bulk mixing of the two in solution may result from diffusion-limited irreversible dendrimer-DNA binding, rather than, or in addition to, the previously proposed cooperative binding mechanism of dendrimers to DNA.

  17. Investigation on interaction of DNA and several cationic surfactants with different head groups by spectroscopy, gel electrophoresis and viscosity technologies.

    Science.gov (United States)

    Guo, Qing; Zhang, Zhaohong; Song, Youtao; Liu, Shuo; Gao, Wei; Qiao, Heng; Guo, Lili; Wang, Jun

    2017-02-01

    In this study, the interaction between DNA and several cationic surfactants with different head groups such as ethyl hexadecyl dimethyl ammonium bromide (EHDAB), hexadecyl dimethyl benzyl ammonium chloride (HDBAC), and cetyl pyridinium bromide (CPB) were investigated by UV-vis absorption, fluorescence and circular dichroism (CD) spectroscopy, gel electrophoresis, and viscosity technologies. The results show that these cationic surfactants can interact with DNA and major binding modes are electrostatic and hydrophobic. Also, CPB and HDBAC molecules interact with DNA by partial intercalation, and CPB has slightly stronger intercalation than HDBAC, while EHDAB interacts with DNA by non-intercalation. The different head groups of the surfactant molecules can influence the interaction strength. CPB has the stronger interaction with DNA than the others. Moreover, surfactant concentration, the ratio of DNA and fluorescence probe, ionic strength can influence the interaction. The surfactants may interact with DNA by the competition reactions with BR for DNA-BR. The increase of ionic strength may favor the surface binding between DNA and surfactants to some extent. This work provides deep mechanistic insight on the toxicity of cationic surfactants with different head groups to DNA molecules.

  18. Cationic polymers for nuclaic acid delivery to tumors

    NARCIS (Netherlands)

    Wolf, H.K. de

    2007-01-01

    In the field of cancer gene therapy, the use of gene carrier systems is considered indispensable. Cationic polymers are able to effectively condense plasmid DNA to nano-sized particles, further referred to as polyplexes. Compared to free DNA, polyplexes have shown improved nuclease-resistance, a

  19. Interaction between a cationic bolaamphiphile and DNA: The route towards nanovectors for oligonucleotide antimicrobials.

    Science.gov (United States)

    Mamusa, Marianna; Resta, Claudio; Barbero, Francesco; Carta, Davide; Codoni, Doroty; Hatzixanthis, Kostas; McArthur, Michael; Berti, Debora

    2016-07-01

    Bacterial resistance to antimicrobials is a global threat that requires development of innovative therapeutics that circumvent its onset. The use of Transcription Factor Decoys (TFDs), DNA fragments that act by blocking essential transcription factors in microbes, represents a very promising approach. TFDs require appropriate carriers to protect them from degradation in biological fluids and transfect them through the bacterial cell wall into the cytoplasm, their site of action. Here we report on a bolaform cationic surfactant, [12-bis-THA]Cl2, with proven transfection activity in vivo. By studying the physical-chemical properties of its aqueous solutions with light scattering, cryo-TEM, ζ-potential, absorption and fluorescence spectroscopies, we prove that the bolaamphiphiles associate into transient vesicles which convert into one-dimensional elongated structures over time. These surfactant assemblies complex TFDs with extremely high efficiency, if compared to common cationic amphiphiles. At Z+/-=11, the nanoplexes are stable and have a size of 120nm, and they form independently of the original morphology of the [12-bis-THA]Cl2 aggregate. DNA is compacted in the nanoplexes, as shown through CD spectroscopy and fluorescence, but is readily released in its native form if sodium taurocholate is added.

  20. Thermal treatment effects imposed on solid DNA cationic lipid complex with hexadecyltrimethylammonium chloride, observed by variable angle spectroscopic ellipsometry

    Energy Technology Data Exchange (ETDEWEB)

    Nizioł, Jacek, E-mail: niziol@agh.edu.pl [Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Kraków (Poland)

    2014-12-21

    DNA cationic lipid complexes are materials of properties required for applications in organic electronics and optoelectronics. Often, their thermal stability demonstrated by thermogravimetry is cited in the literature as important issue. However, little is known about processes occurring in heated solid DNA cationic lipid complexes. In frame of this work, thin films of Deoxyribonucleic acid-hexadecyltrimethylammonium chloride (DNA-CTMA) were deposited on silicon wafers. Samples were thermally annealed, and simultaneously, their optical functions were measured by spectroscopic ellipsometry. At lower temperatures, thermal expansion coefficient of solid DNA-CTMA was negative, but at higher temperatures positive. Thermally induced modification of absorption spectrum in UV-vis was observed. It occurred at a range of temperatures higher than this of DNA denaturation in solution. The observed phenomenon was irreversible, at least in time scale of the experiment (one day)

  1. The electrokinetic characterization of gold nanoparticles, functionalized with cationic functional groups, and its' interaction with DNA.

    Science.gov (United States)

    Lazarus, Geraldine Genevive; Revaprasadu, Neerish; López-Viota, Julián; Singh, Moganavelli

    2014-09-01

    Gold nanoparticles have attracted strong biomedical interest for drug delivery due to their low toxic nature, surface plasmon resonance and capability of increasing the stability of the payload. However, gene transfection represents another important biological application. Considering that cellular barriers keep enclosed their secret to deliver genes using nanoparticles, an important step can be achieved by studying the functionalization of nanoparticles with DNA. In the present contribution the synthesis of nanoparticles consisting of a gold core coated with one or more layers of amino acid (l-lysine), and cationic polyelectrolytes (poly-ethyleneimine and poly-l-lysine) is reported. All nanoparticles were subjected to dynamic light scattering, electrophoretic mobility measurements, UV-vis optical spectrophotometry analysis and transmission electron microscopy imaging. In addition, the adsorption of DNA plasmid (pSGS) with linear and supercoiled configurations was studied for those gold nanoparticles under the most suitable surface modifications. Preliminary results showed that the gold nanoparticles functionalized with poly-ethyleneimine and poly-l-lysine, respectively, and bound to linear DNA configurations, present in absolute value a higher electrophoretic mobility irrespective of the pH of the media, compared to the supercoiled and nicked configuration. The findings from this study suggest that poly-ethyleneimine and poly-l-lysine functionalized gold nanoparticles are biocompatible and may be promising in the chemical design and future optimization of nanostructures for biomedical applications such as gene and drug delivery.

  2. Theoretical study of ionic liquids based on the cholinium cation. Ab initio simulations of their condensed phases

    Science.gov (United States)

    Campetella, Marco; Bodo, Enrico; Montagna, Maria; De Santis, Serena; Gontrani, Lorenzo

    2016-03-01

    We have explored by means of ab initio molecular dynamics the homologue series of 11 different ionic liquids based on the combination of the cholinium cation with deprotonated amino acid anions. We present a structural analysis of the liquid states of these compounds as revealed by accurate ab initio computations of the forces. We highlight the persistent structural motifs that see the ionic couple as the basic building block of the liquid whereby a strong hydrogen bonding network substantially determines the short range structural behavior of the bulk state. Other minor docking features of the interaction network are also discovered and described. Special cases along the series such as Cysteine and Phenylalanine are discussed in the view of their peculiar properties due to zwitterion formation and additional long-range structural organization.

  3. Multi-colored fibers by self-assembly of DNA, histone proteins, and cationic conjugated polymers.

    Science.gov (United States)

    Wang, Fengyan; Liu, Zhang; Wang, Bing; Feng, Liheng; Liu, Libing; Lv, Fengting; Wang, Yilin; Wang, Shu

    2014-01-01

    The development of biomolecular fiber materials with imaging ability has become more and more useful for biological applications. In this work, cationic conjugated polymers (CCPs) were used to construct inherent fluorescent microfibers with natural biological macromolecules (DNA and histone proteins) through the interfacial polyelectrolyte complexation (IPC) procedure. Isothermal titration microcalorimetry results show that the driving forces for fiber formation are electrostatic and hydrophobic interactions, as well as the release of counterions and bound water molecules. Color-encoded IPC fibers were also obtained based on the co-assembly of DNA, histone proteins, and blue-, green-, or red- (RGB-) emissive CCPs by tuning the fluorescence resonance energy-transfer among the CCPs at a single excitation wavelength. The fibers could encapsulate GFP-coded Escherichia coli BL21, and the expression of GFP proteins was successfully regulated by the external environment of the fibers. These multi-colored fibers show a great potential in biomedical applications, such as biosensor, delivery, and release of biological molecules and tissue engineering.

  4. Synthesis and studies of polypeptide materials: Self-assembled block copolypeptide amphiphiles, DNA-condensing block copolypeptides and membrane-interactive random copolypeptides

    Science.gov (United States)

    Wyrsta, Michael Dmytro

    A new class of transition metal initiators for the controlled polymerization of alpha-aminoacid-N-carboxyanhydrides (alpha-NCAs), has been developed by Deming et al. This discovery has allowed for the synthesis of well-defined "protein-like" polymers. Using this chemistry we have made distinct block/random copolypeptides for biomedical applications. Drug delivery, gene delivery, and antimicrobial polymers were the focus of our research efforts. The motivation for the synthesis and study of synthetic polypeptide based materials comes from proteins. Natural proteins are able to adopt a staggeringly large amount of uniquely well-defined folded structures. These structures account for the diversity in properties of proteins. As catalysts (enzymes) natural proteins perform some of the most difficult chemistry with ease and precision at ambient pressures and temperatures. They also exhibit incredible structural properties that directly result from formation of complex hierarchical assemblies. Self-assembling block copolymers were synthesized with various compositions and architectures. In general, di- and tri-block amphiphiles were studied for their self-assembling properties. Both spherical and tubular vesicles were found to assemble from di- and tri-block amphiphiles, respectively. In addition to self-assembly, pH responsiveness was engineered into these amphiphiles by the incorporation of basic residues (lysine) into the hydrophobic block. Another form of self-assembly studied was the condensation of DNA using cationic block copolymers. It was found that cationic block copolymers could condense DNA into compact, ordered, water-soluble aggregates on the nanoscale. These aggregates sufficiently protected DNA from nucleases and yet were susceptible to proteases. These studies form the basis of a gene delivery platform. The ease with which NCAs are polymerized renders them completely amenable to parallel synthetic methods. We have employed this technique to discover new

  5. Structure of DNA-Cationic Surfactant Complexes at Hydrophobically Modified and Hydrophilic Silica Surfaces as Revealed by Neutron Reflectometry

    DEFF Research Database (Denmark)

    Cardenas Gomez, Marite; Wacklin, Hanna; Campbell, Richard A.

    2011-01-01

    In this article, we discuss the structure and composition of mixed DNA-cationic surfactant adsorption layers on both hydrophobic and hydrophilic solid surfaces. We have focused on the effects of the bulk concentrations, the surfactant chain length, and the type solid surface on the interfacial...... layer structure (the location, coverage, and conformation the e DNA and surfactant molecules). Neutron reflectometry is the technique of choice for revealing the surface layer structure by means of selective deuteration. We start by studying the interfacial complexation of DNA...... with dodecyltrimethylammonium bromide (DTAB) and hexadecyltrimethylammonium bromide (CTAB) on hydrophobic surfaces, where we show that DNA molecules are located on top of a self-assembled surfactant monolayer, with the thickness of the DNA layer and the surfactant DNA ratio determined by the surface coverage of the underlying...

  6. Effect of the head-group geometry of amino acid-based cationic surfactants on interaction with plasmid DNA.

    Science.gov (United States)

    Jadhav, Vaibhav; Maiti, Souvik; Dasgupta, Antara; Das, Prasanta Kumar; Dias, Rita S; Miguel, Maria G; Lindman, Björn

    2008-07-01

    The interaction between DNA and different types of amino acid-based cationic surfactants was investigated. Particular attention was directed to determine the extent of influence of surfactant head-group geometry toward tuning the interaction behavior of these surfactants with DNA. An overview is obtained by gel retardation assay, isothermal titration calorimetry, fluorescence spectroscopy, and circular dichroism at different mole ratios of surfactant/DNA; also, cell viability was assessed. The studies show that the surfactants with more complex/bulkier hydrophobic head group interact more strongly with DNA but exclude ethidium bromide less efficiently; thus, the accessibility of DNA to small molecules is preserved to a certain extent. The presence of more hydrophobic groups surrounding the positive amino charge also gave rise to a significantly lower cytotoxicity. The surfactant self-assembly pattern is quite different without and with DNA, illustrating the roles of electrostatic and steric effects in determining the effective shape of a surfactant molecule.

  7. The intracellular delivery of plasmid DNA using cationic reducible carbon nanotube - Disulfide conjugates of polyethylenimine.

    Science.gov (United States)

    Nia, Azadeh Hashem; Eshghi, Hossein; Abnous, Kalil; Ramezani, Mohammad

    2017-03-30

    A series of polyethylenimine conjugates of single-walled carbon nanotube (PEI-SWNT) containing bioreducible disulfide bonds was synthesized and evaluated for their transfection efficiency. Different molecular weights of polyethylenimine (PEI) were thiolated with different mole ratio of 2-iminothiolane (2-IT). Single-walled carbon nanotube (SWNT) was first carboxylated and then three different cysteine-functionalized SWNT formulations were synthesized via introduced linkers: a) carbonyl group b) spermidine c) 1,8-diamino 3,6-dioxo octane. The final nanocarriers were fabricated upon conjugation of thiolated PEIs and thiolated SWNT via oxidative disulfide bond formation. All PEI-disulfide-SWNT conjugates were capable of DNA condensation and showed improved viability and transfection efficiency compared to PEI itself. Transfection efficiencies were up to 1500 times greater than PEI 25kDa (C/P=0.8). The results of this study suggest that the synthesized formulations based on SWNT-CO-Cysteine and PEI 1.8kDa were the most efficient carriers. Considering the decreased cytotoxicity and higher transfection levels, the conjugates bear the potential for effective delivery of genetic materials. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Evaluation of Maltose-Based Cationic Liposomes with Different Hydrophobic Tails for Plasmid DNA Delivery

    Directory of Open Access Journals (Sweden)

    Bo Li

    2017-03-01

    Full Text Available In this paper, three cationic glycolipids with different hydrophobic chains Malt-DiC12MA (IX a, Malt-DiC14MA (IX b and Malt-DiC16MA (IX c were constructed by using maltose as starting material via peracetylation, selective 1-O-deacetylation, trichloroacetimidation, glycosylation, azidation, deacetylation, Staudinger reaction, tertiary amination and quaternization. Target compounds and some intermediates were characterized by 1H-NMR, 13C-NMR, 1H-1H COSY and 1H-13C HSQC. The results of gel electrophoresis assay, atomic force microscopy images (AFM and dynamic light scattering (DLS demonstrate that all the liposomes could efficiently bind and compact DNA (N/P ratio less than 2 into nanoparticles with proper size (88 nm–146 nm, PDI < 0.4 and zeta potential (+15 mV–+26 mV. The transfection efficiency and cellular uptake of glycolipids in HEK293 cell were evaluated through the enhanced green fluorescent protein (EGFP expression and Cy3-labeled pEGFP-C1 (Enhanced Green Fluorescent Protein plasmid images, respectively. Importantly, it indicated that Malt-DiC14MA exhibited high gene transfer efficiency and better uptake capability at N/P ratios of 8:1. Additionally, the result of cell viability showed glycolipids exhibited low biotoxicity and good biocompatibility by thiazolyl blue tetrazolium bromide (MTT assay.

  9. Influence of phospholipid composition on cationic emulsions/DNA complexes: physicochemical properties, cytotoxicity, and transfection on Hep G2 cells

    Directory of Open Access Journals (Sweden)

    Fraga M

    2011-10-01

    Full Text Available Michelle Fraga1,2, Fernanda Bruxel1, Valeska Lizzi Lagranha2,3, Helder Ferreira Teixeira1, Ursula Matte2,31Post Graduation Program in Pharmaceutical Sciences, Universidade Federal do Rio Grande do Sul, 2Gene Therapy Center, Experimental Research Center, Hospital de Clínicas de Porto Alegre, 3Post Graduation Program in Genetics and Molecular Biology, Universidade Federal do Rio Grande do Sul, Porto Alegre, BrazilBackground: Cationic nanoemulsions have been recently considered as potential delivery systems for nucleic acids. This study reports the influence of phospholipids on the properties of cationic nanoemulsions/DNA plasmid complexes.Methods: Nanoemulsions composed of medium-chain triglycerides, stearylamine, egg lecithin or isolated phospholipids, ie, DSPC, DOPC, DSPE, or DOPE, glycerol, and water were prepared by spontaneous emulsification. Gene transfer to Hep G2 cells was analyzed using real-time polymerase chain reaction.Results: The procedure resulted in monodispersed nanoemulsions with a droplet size and zeta potential of approximately 250 nm and +50 mV, respectively. The complexation of cationic nanoemulsions with DNA plasmid, analyzed by agarose gel retardation assay, was complete when the complex was obtained at a charge ratio of ≥1.0. In these conditions, the complexes were protected from enzymatic degradation by DNase I. The cytotoxicity of the complexes in Hep G2 cells, evaluated by MTT assay, showed that an increasing number of complexes led to progressive toxicity. Higher amounts of reporter DNA were detected for the formulation obtained with the DSPC phospholipid. Complexes containing DSPC and DSPE phospholipids, which have high phase transition temperatures, were less toxic in comparison with the formulations obtained with lecithin, DOPC, and DOPE.Conclusion: The results show the effect of the DNA/nanoemulsion complexes composition on the toxicity and transfection results.Keywords: plasmids, cationic nanoemulsions

  10. Capture of a Transition State Using Molecular Dynamics: Creation of an Intercalation Site in dsDNA with Ethidium Cation

    Directory of Open Access Journals (Sweden)

    Regina R. Monaco

    2010-01-01

    Full Text Available The mechanism of intercalation and the ability of double stranded DNA (dsDNA to accommodate a variety of ligands in this manner has been well studied. Proposed mechanistic steps along this pathway for the classical intercalator ethidium have been discussed in the literature. Some previous studies indicate that the creation of an intercalation site may occur spontaneously, with the energy for this interaction arising either from solvent collisions or soliton propagation along the helical axis. A subsequent 1D diffusional search by the ligand along the helical axis of the DNA will allow the ligand entry to this intercalation site from its external, electrostatically stabilized position. Other mechanistic studies show that ethidium cation participates in the creation of the site, as a ligand interacting closely with the external surface of the DNA can cause unfavorable steric interactions depending on the ligands' orientation, which are relaxed during the creation of an intercalation site. Briefly, such a site is created by the lengthening of the DNA molecule via bond rotation between the sugars and phosphates along the DNA backbone, causing an unwinding of the dsDNA itself and separation between the adjacent base pairs local to the position of the ligand, which becomes the intercalation site. Previous experimental measurements of this interaction measure the enthalpic cost of this part of the mechanism to be about −8 kcal/mol. This paper reports the observation, during a computational study, of the spontaneous opening of an intercalation site in response to the presence of a single ethidium cation molecule in an externally bound configuration. The concerted motions between this ligand and the host, a dsDNA decamer, are clear. The dsDNA decamer AGGATGCCTG was studied; the central …GATG… site was the intercalation site.

  11. DNA association-enhanced physical stability of catanionic vesicles composed of ion pair amphiphile with double-chain cationic surfactant.

    Science.gov (United States)

    Lee, Jung; Chang, Chien-Hsiang

    2014-09-01

    Physical stability control of vesicle/DNA complexes is a key issue for the development of catanionic vesicles composed of ion pair amphiphile (IPA) as DNA carriers. In this work, physical stability characteristics of the complexes of DNA with positively charged catanionic vesicles composed of an IPA and a double-chain cationic surfactant, dihexadecyldimethylammonium bromide (DHDAB), were explored. It was found that in water, the mixed IPA/DHDAB catanionic vesicles became stable when the mole fraction of DHDAB (xDHDAB) was increased up to 0.5. The improved physical stability of the vesicles with a high xDHDAB could be related to the enhanced electrostatic interaction between the vesicles. When the catanionic vesicles interacted with DNA, excellent physical stability was detected for the vesicle/DNA complexes especially with a high xDHDAB. However, this could not be fully explained by the electrostatic interaction effect, and the role of molecular packing within the vesicular bilayers was apparently important. The corresponding Langmuir monolayer study demonstrated that the molecular packing of mixed IPA/DHDAB layers became ordered with DNA association due to inhibited desorption of the positively charged moiety of the IPA. Moreover, the DNA association-induced improvement in the molecular packing of the mixed IPA/DHDAB layers became pronounced with increased xDHDAB. The results imply that one can fabricate catanionic vesicle/DNA complexes with excellent physical stability through the improved molecular packing in the IPA vesicular bilayers with DHDAB addition and DNA association.

  12. Ultrasound-Mediated Gene Delivery with Cationic Versus Neutral Microbubbles: Effect of DNA and Microbubble Dose on In Vivo Transfection Efficiency

    Science.gov (United States)

    Panje, Cedric M.; Wang, David S.; Pysz, Marybeth A.; Paulmurugan, Ramasamy; Ren, Ying; Tranquart, Francois; Tian, Lu; Willmann, Jürgen K.

    2012-01-01

    Objective: To assess the effect of varying microbubble (MB) and DNA doses on the overall and comparative efficiencies of ultrasound (US)-mediated gene delivery (UMGD) to murine hindlimb skeletal muscle using cationic versus neutral MBs. Materials and Methods: Cationic and control neutral MBs were characterized for size, charge, plasmid DNA binding, and ability to protect DNA against endonuclease degradation. UMGD of a codon optimized firefly luciferase (Fluc) reporter plasmid to endothelial cells (1 MHz, 1 W/cm², 20% duty cycle, 1 min) was performed in cell culture using cationic, neutral, or no MBs. In vivo UMGD to mouse hindlimb muscle was performed by insonation (1 MHz, 2 W/cm², 50% duty cycle, 5 min) after intravenous administration of Fluc combined with cationic, neutral, or no MBs. Gene delivery efficiency was assessed by serial in vivo bioluminescence imaging. Efficiency of in vivo UMGD with cationic versus neutral MBs was systematically evaluated by varying plasmid DNA dose (10, 17.5, 25, 37.5, and 50 µg) while maintaining a constant MB dose of 1x108 MBs and by changing MB dose (1x107, 5x107, 1x108, or 5x108 MBs) while keeping a constant DNA dose of 50 µg. Results: Cationic and size-matched control neutral MBs differed significantly in zeta potential with cationic MBs being able to bind plasmid DNA (binding capacity of 0.03 pg/MB) and partially protect DNA from nuclease degradation while neutral MBs could not. Cationic MBs enhanced UMGD compared to neutral MBs as well as no MB and no US controls both in cell culture (P < 0.001) and in vivo (P < 0.05). Regardless of MB type, in vivo UMGD efficiency increased dose-dependently with DNA dose and showed overall maximum transfection with 50 µg DNA. However, there was an inverse correlation (ρ = -0.90; P = 0.02) between DNA dose and the degree of enhanced UMGD efficiency observed with using cationic MBs instead of neutral MBs. The delivery efficiency advantage associated with cationic MBs was most prominent

  13. Ultrasound-Mediated Gene Delivery with Cationic Versus Neutral Microbubbles: Effect of DNA and Microbubble Dose on In Vivo Transfection Efficiency

    Directory of Open Access Journals (Sweden)

    Cedric M. Panje, David S. Wang, Marybeth A. Pysz, Ramasamy Paulmurugan, Ying Ren, Francois Tranquart, Lu Tian, Jürgen K. Willmann

    2012-01-01

    Full Text Available Objective: To assess the effect of varying microbubble (MB and DNA doses on the overall and comparative efficiencies of ultrasound (US-mediated gene delivery (UMGD to murine hindlimb skeletal muscle using cationic versus neutral MBs.Materials and Methods: Cationic and control neutral MBs were characterized for size, charge, plasmid DNA binding, and ability to protect DNA against endonuclease degradation. UMGD of a codon optimized firefly luciferase (Fluc reporter plasmid to endothelial cells (1 MHz, 1 W/cm², 20% duty cycle, 1 min was performed in cell culture using cationic, neutral, or no MBs. In vivo UMGD to mouse hindlimb muscle was performed by insonation (1 MHz, 2 W/cm², 50% duty cycle, 5 min after intravenous administration of Fluc combined with cationic, neutral, or no MBs. Gene delivery efficiency was assessed by serial in vivo bioluminescence imaging. Efficiency of in vivo UMGD with cationic versus neutral MBs was systematically evaluated by varying plasmid DNA dose (10, 17.5, 25, 37.5, and 50 µg while maintaining a constant MB dose of 1x108 MBs and by changing MB dose (1x107, 5x107, 1x108, or 5x108 MBs while keeping a constant DNA dose of 50 µg.Results: Cationic and size-matched control neutral MBs differed significantly in zeta potential with cationic MBs being able to bind plasmid DNA (binding capacity of 0.03 pg/MB and partially protect DNA from nuclease degradation while neutral MBs could not. Cationic MBs enhanced UMGD compared to neutral MBs as well as no MB and no US controls both in cell culture (P < 0.001 and in vivo (P < 0.05. Regardless of MB type, in vivo UMGD efficiency increased dose-dependently with DNA dose and showed overall maximum transfection with 50 µg DNA. However, there was an inverse correlation (ρ = -0.90; P = 0.02 between DNA dose and the degree of enhanced UMGD efficiency observed with using cationic MBs instead of neutral MBs. The delivery efficiency advantage associated with cationic MBs was most

  14. Chelation of Membrane-Bound Cations by Extracellular DNA Activates the Type VI Secretion System in Pseudomonas aeruginosa.

    Science.gov (United States)

    Wilton, Mike; Wong, Megan J Q; Tang, Le; Liang, Xiaoye; Moore, Richard; Parkins, Michael D; Lewenza, Shawn; Dong, Tao G

    2016-08-01

    Pseudomonas aeruginosa employs its type VI secretion system (T6SS) as a highly effective and tightly regulated weapon to deliver toxic molecules to target cells. T6SS-secreted proteins of P. aeruginosa can be detected in the sputum of cystic fibrosis (CF) patients, who typically present a chronic and polymicrobial lung infection. However, the mechanism of T6SS activation in the CF lung is not fully understood. Here we demonstrate that extracellular DNA (eDNA), abundant within the CF airways, stimulates the dynamics of the H1-T6SS cluster apparatus in Pseudomonas aeruginosa PAO1. Addition of Mg(2+) or DNase with eDNA abolished such activation, while treatment with EDTA mimicked the eDNA effect, suggesting that the eDNA-mediated effect is due to chelation of outer membrane-bound cations. DNA-activated H1-T6SS enables P. aeruginosa to nonselectively attack neighboring species regardless of whether or not it was provoked. Because of the importance of the T6SS in interspecies interactions and the prevalence of eDNA in the environments that P. aeruginosa inhabits, our report reveals an important adaptation strategy that likely contributes to the competitive fitness of P. aeruginosa in polymicrobial communities.

  15. Polycations XX: New Monodentate Cationic Ligands and Their Coordination with Ruthenium for the Construction of Complexes Expressing Enhanced Interaction with DNA

    Directory of Open Access Journals (Sweden)

    Leslie Babukutty

    2012-01-01

    Full Text Available Prior investigations from this laboratory concerned with the preparation of new types of organic cations for a variety of biological and nonbiological applications have been extended to the preparation of cation-bearing ligands with nitrogen coordinating sites for use in complexation reactions with ruthenium cores. The syntheses of new cationic ligands as well as ruthenium complexes bearing them are reported here. The introduction of these new types of ligands is intended to provide to the complexes an enhanced ability to interact with DNA, and thereby to have the potential to be enhanced antitumor agents. Preliminary observations of their interactions with DNA are presented.

  16. Role of amino acid insertions on intermolecular forces between arginine peptide condensed DNA helices: implications for protamine-DNA packaging in sperm.

    Science.gov (United States)

    DeRouchey, Jason E; Rau, Donald C

    2011-12-09

    In spermatogenesis, chromatin histones are replaced by arginine-rich protamines to densely compact DNA in sperm heads. Tight packaging is considered necessary to protect the DNA from damage. To better understand the nature of the forces condensing protamine-DNA assemblies and their dependence on amino acid content, the effect of neutral and negatively charged amino acids on DNA-DNA intermolecular forces was studied using model peptides containing six arginines. We have previously observed that the neutral amino acids in salmon protamine decrease the net attraction between protamine-DNA helices compared with the equivalent homo-arginine peptide. Using osmotic stress coupled with x-ray scattering, we have investigated the component attractive and repulsive forces that determine the net attraction and equilibrium interhelical distance as a function of the chemistry, position, and number of the amino acid inserted. Neutral amino acids inserted into hexa-arginine increase the short range repulsion while only slightly affecting longer range attraction. The amino acid content alone of salmon protamine is enough to rationalize the forces that package DNA in sperm heads. Inserting a negatively charged amino acid into hexa-arginine dramatically weakens the net attraction. Both of these observations have biological implications for protamine-DNA packaging in sperm heads.

  17. Changes in the infrared microspectroscopic characteristics of DNA caused by cationic elements, different base richness and single-stranded form.

    Directory of Open Access Journals (Sweden)

    Maria Luiza S Mello

    Full Text Available BACKGROUND: The infrared (IR analysis of dried samples of DNA and DNA-polypeptide complexes is still scarce. Here we have studied the FT-IR profiles of these components to further the understanding of the FT-IR signatures of chromatin and cell nuclei. METHODOLOGY/PRINCIPAL FINDINGS: Calf thymus and salmon testis DNA, and complexes of histone H1, protamine, poly-L-lysine and poly-L-arginine (histone-mimic macromolecules with DNA were analyzed in an IR microspectroscope equipped with an attenuated total reflection diamond objective and Grams software. Conditions including polypeptides bound to the DNA, DNA base composition, and single-stranded form were found to differently affect the vibrational characteristics of the chemical groups (especially, PO(2(- in the nucleic acid. The antisymmetric stretching (ν(as of the DNA PO(2(- was greater than the symmetric stretching (ν(s of these groups and increased in the polypeptide-DNA complexes. A shift of the ν(as of the DNA PO(2(- to a lower frequency and an increased intensity of this vibration were induced especially by lysine-rich histones. Lysine richness additionally contributed to an increase in the vibrational stretching of the amide I group. Even in simple molecules such as inorganic phosphates, the vibrational characteristics of the phosphate anions were differently affected by different cations. As a result of the optimization of the DNA conformation by binding to arginine-rich polypeptides, enhancements of the vibrational characteristics in the FT-IR fingerprint could be detected. Although different profiles were obtained for the DNA with different base compositions, this situation was no longer verified in the polypeptide-DNA complexes and most likely in isolated chromatin or cell nuclei. However, the ν(as PO(2(-/ν(s PO(2(- ratio could discriminate DNA with different base compositions and DNA in a single-stranded form. CONCLUSIONS/SIGNIFICANCE: FT-IR spectral profiles are a valuable tool

  18. Cationic influenza virosomes as an adjuvanted delivery system for CTL induction by DNA vaccination

    NARCIS (Netherlands)

    Jamali, Abbas; Holtrop, Marijke; de Haan, Aalzen; Hashemi, Hamidreza; Shenagari, Mohammad; Memarnejadian, Arash; Roohvand, Farzin; Sabahi, Farzaneh; Kheiri, Masumeh Tavassoti; Huckriede, Anke

    2012-01-01

    DNA vaccines have emerged as an attractive approach to induce CTL responses against cancer and infectious agents in recent years. Although CTL induction by DNA vaccination would be a valuable strategy for controlling viral infections, increasing the potency of DNA vaccines is mandatory before DNA

  19. Compositional tuning of epoxide-polyetheramine "click" reaction toward cytocompatible, cationic hydrogel particles with antimicrobial and DNA binding activities.

    Science.gov (United States)

    Tang, Shuangcheng; Huang, Lu; Daniels-Mulholland, Robert J; Dlugosz, Elizabeth; Morin, Emily A; Lenaghan, Scott; He, Wei

    2016-10-01

    The "click" characteristics of nucleophilic opening of epoxide have recently been exploited for the development of a functional hydrogel particle system based on commercially available bisepoxide and triamine polyetheramine monomers. Key features of these particles include high cationic charges and responsiveness to temperature, pH, and oxidation. Despite these advantages, the cytocompatibility of these particles must be considered prior to use in biomedical applications. Here we demonstrate that, by introducing a diamine polyetheramine as a comonomer in the "click" reaction, and tuning its molar ratio with the triamine monomer, cationic nanoparticles with improved cytocompatibility can be prepared. The reduced cytotoxicity is primarily due to the hydrophilic backbone of the diamine comonomer, which has polyethylene glycol as a primary component. The resulting nanoparticles formed from the diamine comonomer exhibited a lower surface charge, while maintaining a comparable size. In addition, the responsiveness of the nanoparticles to temperature, pH, and oxidation was conserved, while achieving greater colloidal stability at basic pH. Results from this study further demonstrated that the nanoparticles were able to encapsulate Nile red, a model for hydrophobic drug molecules, were effective against the bacteria Staphylococcus aureus, and were capable of binding DNA through ionic complexation. Based on the results from this work, the use of diamine comonomers significantly reduces the cytotoxicity of similarly developed hydrogel nanoparticles, allowing for numerous biomedical applications, including nanocarriers for therapeutic agents with poor water solubility, treatment of bacterial infection, and non-viral vectors for gene therapy. In recent years significant attention has been placed on the development of nanocarriers for numerous biomedical applications. Of particular interest are cationic polymers, which contain high positive surface charges that allow binding of

  20. Biophysical characterization of complexes of DNA with mixtures of the neutral lipids 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-hexanoylamine or 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-dodecanoylamine and 1,2-dioleoyl-sn-glycero-3-phosphocholine in the presence of bivalent metal cations for DNA transfection.

    Science.gov (United States)

    Pisani, Michela; Mobbili, Giovanna; Placentino, Immacolata F; Smorlesi, Arianna; Bruni, Paolo

    2011-09-01

    Neutral lipids have received up to now a little attention as genetic material carriers, despite some valuable features, such as the absence of toxicity and the high stability in serum of their complexes with DNA. We have prepared two quaternary complexes of DNA and mixtures of 1, 2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-hexanoylamine (6PE) or 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-dodecanoylamine (12PE) with DOPC in aqueous dispersions of bivalent metal cations (PE/DOPC-DNA-M(2+)). The aim was to evaluate the effect of the amide moiety on the transfection efficiency. These complexes form in a self-assembled manner, the DNA condensation being promoted by the metal cations. Synchrotron X-ray diffraction analysis was used to determine the structure of the complexes, which exhibit the lamellar symmetry of the L(α)(c) phase. The size and surface charge of the complexes have also been measured, and promising results of DNA transfections in vitro have been reported. © 2011 American Chemical Society

  1. Early and late effects of Ibuprofen on mouse sperm parameters, chromatin condensation, and DNA integrity in mice

    Directory of Open Access Journals (Sweden)

    Fatemeh Roodbari

    2015-11-01

    Full Text Available Background: There are few studies indicating the detrimental effects of ibuprofen on sperm fertility potential and DNA integrity. Objective: To determine the effects of Ibuprofen on sperm parameters, chromatin condensation and DNA integrity of mice. Materials and Methods: In this experimental study, 36 adult male mice with average weight 37 gr were divided into three groups, including control (group I, n=12, normal dosage of ibuprofen (group II, n=12 and high dosage (group III, n=12. Ibuprofen with different doses was dissolved in daily water of animals. After 35, 70 and 105 days, the cauda epididymis of mice were cut and incubated in Ham’s F10 media. Sperm samples were analyzed for parameters (motility, morphology and count, DNA integrity (SCD test and chromatin condensation (chromomycin A3 and Aniline blue staining. Results: After 35 days, in addition to above mentioned sperm parameters, all of the treated mice showed statistically significant increase in spermatozoa with immature chromatin (P<0.05. However, after 70 days, the rate of sperm DNA fragmentation assessed by SCD was increased in group II (66.5±0.7 and the percentage of immature spermatozoa (AB+ and CMA3+ was higher in group III (77.5±0.7 and 49.5±6.3 respectively than other groups. After 105 days, the AB+ spermatozoa were increased in both normal dose and high dose groups. Conclusion: Ibuprofen may cause a significant reduction in sperm parameters and sperm chromatin/DNA integrity in mice. It should be noted that these deleterious effects are dose-dependent and can be seen in early and late stage of drug treatments.

  2. Description of the binding of chitosan to DNA at different ionic strengths in terms of the theories of ion condensation and adsorption

    NARCIS (Netherlands)

    Vorob'ev, E. A.; Nechipurenko, Yu. D.; Salyanov, V. I.; Evdokimov, Yu. M.

    2007-01-01

    The binding of chitosan molecules to DNA in solutions of different ionic strength has been studied. The data were analyzed in terms of the model of ion condensation and the thermodynamic theory of the binding of protracted ligands to DNA. Combining these approaches made it possible to estimate the s

  3. Elucidating the interplay between DNA-condensing and free polycations in gene transfection through a mechanistic study of linear and branched PEI

    DEFF Research Database (Denmark)

    Dai, Zhuojun; Gjetting, Torben; Mattebjerg, Maria Ahlm;

    2011-01-01

    In the present study we compare LPEI and BPEI characteristics related to DNA condensation and their role as free polycation chains in gene transfection. Using radioactive 32P labeled DNA, we investigated the effect of free PEI chains on the cellular uptake of polyplexes. Our investigations show d...

  4. Cationic solid-lipid nanoparticles can efficiently bind and transfect plasmid DNA

    NARCIS (Netherlands)

    Olbrich, C; Bakowsky, U; Muller, RH; Kneuer, C

    2001-01-01

    The suitability of cationically modified solid-lipid nanoparticles (SLN) as a novel transfection agent was investigated. SLN were produced by hot homogenisation using either Compritol ATO 888 or paraffin as matrix lipid, a mixture of Tween 80 and Span 85 as tenside and either EQ1 (NN-di-(beta-steaor

  5. The neutrophil-activating Dps protein of Helicobacter pylori, HP-NAP, adopts a mechanism different from Escherichia coli Dps to bind and condense DNA.

    Science.gov (United States)

    Ceci, Pierpaolo; Mangiarotti, Laura; Rivetti, Claudio; Chiancone, Emilia

    2007-01-01

    The Helicobacter pylori neutrophil-activating protein (HP-NAP), a member of the Dps family, is a fundamental virulence factor involved in H.pylori-associated disease. Dps proteins protect bacterial DNA from oxidizing radicals generated by the Fenton reaction and also from various other damaging agents. DNA protection has a chemical component based on the highly conserved ferroxidase activity of Dps proteins, and a physical one based on the capacity of those Dps proteins that contain a positively charged N-terminus to bind and condense DNA. HP-NAP does not possess a positively charged N-terminus but, unlike the other members of the family, is characterized by a positively charged protein surface. To establish whether this distinctive property could be exploited to bind DNA, gel shift, fluorescence quenching and atomic force microscopy (AFM) experiments were performed over the pH range 6.5-8.5. HP-NAP does not self-aggregate in contrast to Escherichia coli Dps, but is able to bind and even condense DNA at slightly acid pH values. The DNA condensation capacity acts in concert with the ferritin-like activity and could be used to advantage by H.pylori to survive during host-infection and other stress challenges. A model for DNA binding/condensation is proposed that accounts for all the experimental observations.

  6. Synthesis of linear and cyclic peptide-PEG-lipids for stabilization and targeting of cationic liposome-DNA complexes.

    Science.gov (United States)

    Ewert, Kai K; Kotamraju, Venkata Ramana; Majzoub, Ramsey N; Steffes, Victoria M; Wonder, Emily A; Teesalu, Tambet; Ruoslahti, Erkki; Safinya, Cyrus R

    2016-03-15

    Because nucleic acids (NAs) have immense potential value as therapeutics, the development of safe and effective synthetic NA vectors continues to attract much attention. In vivo applications of NA vectors require stabilized, nanometer-scale particles, but the commonly used approaches of steric stabilization with a polymer coat (e.g., PEGylation; PEG=poly(ethylene glycol)) interfere with attachment to cells, uptake, and endosomal escape. Conjugation of peptides to PEG-lipids can improve cell attachment and uptake for cationic liposome-DNA (CL-DNA) complexes. We present several synthetic approaches to peptide-PEG-lipids and discuss their merits and drawbacks. A lipid-PEG-amine building block served as the common key intermediate in all synthetic routes. Assembling the entire peptide-PEG-lipid by manual solid phase peptide synthesis (employing a lipid-PEG-carboxylic acid) allowed gram-scale synthesis but is mostly applicable to linear peptides connected via their N-terminus. Conjugation via thiol-maleimide or strain-promoted (copper-free) azide-alkyne cycloaddition chemistry is highly amenable to on-demand preparation of peptide-PEG-lipids, and the appropriate PEG-lipid precursors are available in a single chemical step from the lipid-PEG-amine building block. Azide-alkyne cycloaddition is especially suitable for disulfide-bridged peptides such as iRGD (cyclic CRGDKGPDC). Added at 10 mol% of a cationic/neutral lipid mixture, the peptide-PEG-lipids stabilize the size of CL-DNA complexes. They also affect cell attachment and uptake of nanoparticles in a peptide-dependent manner, thereby providing a platform for preparing stabilized, affinity-targeted CL-DNA nanoparticles.

  7. Shock waves and DNA-cationic lipid assemblies: a synergistic approach to express exogenous genes in human cells.

    Science.gov (United States)

    Millán-Chiu, Blanca; Camacho, Giselle; Varela-Echavarría, Alfredo; Tamariz, Elisa; Fernández, Francisco; López-Marín, Luz M; Loske, Achim M

    2014-07-01

    Cationic lipid/DNA complexes (lipoplexes) represent a powerful tool for cell transfection; however, their use is still limited by important concerns, including toxicity and poor internalization into deep tissues. In this work, we investigated the use of shock wave-induced acoustic cavitation in vitro for the transfection of lipoplexes in human embryo kidney 293 cells. We selected shock waves with the ability to internalize 10-kDa fluorescein isothiocyanate-dextran into cells while maintaining survival rates above 50%. Cell transfection was tested using the green fluorescent protein-encoding plasmid pCX::GFPGPI2. Confocal microscopy and fluorescence-assisted cell sorting analyses revealed successful transfection after treatments ranging from 1 to 3 min using 60 to 180 shock waves at peak amplitudes of 12.3 ± 1.5 MPa. Interestingly, the combination of shock waves and lipoplexes induced a 3.1- and 3.8-fold increase in the expression of the reporter gene compared with the use of lipoplexes or shock waves alone, respectively. These results indicate that cationic DNA assembly and shock waves act in a synergistic manner to promote transfection of human cells, revealing a potential approach for non-invasive site-specific gene therapy. Copyright © 2014 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  8. Quantitative analysis of EDC-condensed DNA on vertically aligned carbon nanofiber gene delivery arrays

    Energy Technology Data Exchange (ETDEWEB)

    Mann, David G. J. [Univ. of Tennessee, Knoxville, TN (United States). Center for Environmental Biotechnology; McKnight, Timothy E. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Engineering Science and Technology Division; Melechko, Anatoli V. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Science (CNMS); Simpson, Michael L. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Science (CNMS); Sayler, Gary S. [Univ. of Tennessee, Knoxville, TN (United States). Center for Environmental Biotechnology

    2006-12-08

    Vertically aligned carbon nanofibers (VACNFs) with immobilized DNA have been developed as a novel tool for direct physical introduction and expression of exogenous genes in mammalian cells. Immobilization of DNA base amines to the carboxylic acids on nanofibers can influence the accessibility and transcriptional activity of the DNA template, making it necessary to determine the number of accessible gene copies on nanofiber arrays. We used polymerase chain reaction (PCR) and in vitro transcription (IVT) to investigate the transcriptional accessibility of DNA tethered to VACNFs by correlating the yields of both IVT and PCR to that of non-tethered, free DNA. Yields of the promoter region and promoter/gene region of bound DNA plasmid were high. Amplification using primers designed to cover 80% of the plasmid failed to yield any product. These results are consistent with tethered, longer DNA sequences having a higher probability of interfering with the activity of DNA and RNA polymerases. Quantitative PCR (qPCR) was used to quantify the number of accessible gene copies tethered to nanofiber arrays. Copy numbers of promoters and reporter genes were quantified and compared to non-tethered DNA controls. In subsequent reactions of the same nanofiber arrays, DNA yields decreased dramatically in the non-tethered control, while the majority of tethered DNA was retained on the arrays. This decrease could be explained by the presence of DNA which is non-tethered to all samples and released during the assay. In conclusion,this investigation shows the applicability of these methods for monitoring DNA immobilization techniques.

  9. Competitive interaction of monovalent cations with DNA from 3D-RISM

    OpenAIRE

    Giambaşu, George M.; Gebala, Magdalena K.; Panteva, Maria T.; Luchko, Tyler; Case, David A.; York, Darrin M.

    2015-01-01

    The composition of the ion atmosphere surrounding nucleic acids affects their folding, condensation and binding to other molecules. It is thus of fundamental importance to gain predictive insight into the formation of the ion atmosphere and thermodynamic consequences when varying ionic conditions. An early step toward this goal is to benchmark computational models against quantitative experimental measurements. Herein, we test the ability of the three dimensional reference interaction site mo...

  10. Why double-stranded RNA resists condensation

    Energy Technology Data Exchange (ETDEWEB)

    Tolokh, Igor S.; Pabit, Suzette; Katz, Andrea M.; Chen, Yujie; Drozdetski, Aleksander; Baker, Nathan A.; Pollack, Lois; Onufriev, Alexey

    2014-09-15

    The addition of small amounts of multivalent cations to solutions containing double-stranded DNA leads to attraction between the negatively charged helices and eventually to condensation. Surprisingly, this effect is suppressed in double-stranded RNA, which carries the same charge as the DNA, but assumes a different double helical form. However, additional characterization of short (25 base-pairs) nucleic acid (NA) duplex structures by circular dichroism shows that measured differences in condensation are not solely determined by duplex helical geometry. Here we combine experiment, theory, and atomistic simulations to propose a mechanism that connects the observed variations in condensation of short NA duplexes with the spatial variation of cobalt hexammine (CoHex) binding at the NA duplex surface. The atomistic picture that emerged showed that CoHex distributions around the NA reveals two major NA-CoHex binding modes -- internal and external -- distinguished by the proximity of bound CoHex to the helical axis. Decreasing trends in experimentally observed condensation propensity of the four studied NA duplexes (from B-like form of homopolymeric DNA, to mixed sequence DNA, to DNA:RNA hybrid, to A-like RNA) are explained by the progressive decrease of a single quantity: the fraction of CoHex ions in the external binding mode. Thus, while NA condensation depends on a complex interplay between various structural and sequence features, our coupled experimental and theoretical results suggest a new model in which a single parameter connects the NA condensation propensity with geometry and sequence dependence of CoHex binding.

  11. Cationic Polymer Intercalation into the Lipid Membrane Enables Intact Polyplex DNA Escape from Endosomes for Gene Delivery.

    Science.gov (United States)

    Vaidyanathan, Sriram; Chen, Junjie; Orr, Bradford G; Banaszak Holl, Mark M

    2016-06-06

    Developing improved cationic polymer-DNA polyplexes for gene delivery requires improved understanding of DNA transport from endosomes into the nucleus. Using a FRET-capable oligonucleotide molecular beacon (OMB), we monitored the transport of intact DNA to cell organelles. We observed that for effective (jetPEI) and ineffective (G5 PAMAM) vectors, the fraction of cells displaying intact OMB in the cytosol (jetPEI ≫ G5 PAMAM) quantitatively predicted the fraction expressing transgene (jetPEI ≫ G5 PAMAM). Intact OMB delivered with PAMAM and confined to endosomes could be released to the cytosol by the subsequent addition of L-PEI, with a corresponding 10-fold increase in transgene expression. These results suggest that future vector development should optimize vectors for intercalation into, and destabilization of, the endosomal membrane. Finally, the study highlights a two-step strategy in which the pDNA is loaded in cells using one vector and endosomal release is mediated by a second agent.

  12. Effect of ionic strength and cationic DNA affinity binders on the DNA sequence selective alkylation of guanine N7-positions by nitrogen mustards

    Energy Technology Data Exchange (ETDEWEB)

    Hartley, J.A.; Forrow, S.M.; Souhami, R.L. (Univ. College and Middlesex School of Medicine, London (England))

    1990-03-27

    Large variations in alkylation intensities exist among guanines in a DNA sequence following treatment with chemotherapeutic alkylating agents such as nitrogen mustards, and the substituent attached to the reactive group can impose a distinct sequence preference for reaction. In order to understand further the structural and electrostatic factors which determine the sequence selectivity of alkylation reactions, the effect of increase ionic strength, the intercalator ethidium bromide, AT-specific minor groove binders distamycin A and netropsin, and the polyamine spermine on guanine N7-alkylation by L-phenylalanine mustard (L-Pam), uracil mustard (UM), and quinacrine mustard (QM) was investigated with a modification of the guanine-specific chemical cleavage technique for DNA sequencing. The result differed with both the nitrogen mustard and the cationic agent used. The effect, which resulted in both enhancement and suppression of alkylation sites, was most striking in the case of netropsin and distamycin A, which differed from each other. DNA footprinting indicated that selective binding to AT sequences in the minor groove of DNA can have long-range effects on the alkylation pattern of DNA in the major groove.

  13. Chiroptical properties of anionic and cationic porphyrins and metalloporphyrins in complex with left-handed Z-DNA and right-handed B-DNA.

    Science.gov (United States)

    Choi, Jung Kyu; D'Urso, Alessandro; Balaz, Milan

    2013-10-01

    We report the chiroptical signature and binding interactions of cationic (meso-tetrakis(4-N-methylptridyl)porphyrin, 2HT4) and anionic (meso-tetrakis(4-sulfonatophenyl)porphyrin, 2HTPPS) porphyrins and their zinc(II) and nickel(II) derivatives (ZnT4, ZnTPPS, NiT4, and NiTPPS) with right-handed B-form and two forms of left-handed Z-form of alternating guanine-cytosine polydeoxynucleotide poly(dG-dC)2. NiTPPS is able to spectroscopically discriminate between spermine-induced Z-DNA and Co(III)-induced Z-DNA via new induced circular dichroism signal in the visible region of the electromagnetic spectrum.

  14. Ultratrace DNA Detection Based on the Condensing-Enrichment Effect of Superwettable Microchips.

    Science.gov (United States)

    Xu, Li-Ping; Chen, Yanxia; Yang, Gao; Shi, Wanxin; Dai, Bing; Li, Guannan; Cao, Yanhua; Wen, Yongqiang; Zhang, Xueji; Wang, Shutao

    2015-11-18

    A sensitive nucleic acid detection platform based on superhydrophilic microwells spotted on a superhydrophobic substrate is fabricated. Due to the wettability differences, ultratrace DNA molecules are enriched and the fluorescent signals are amplified to allow more sensitive detection. The biosensing interface based on superwettable materials provides a simple and cost-effective way for ultratrace DNA sensing.

  15. Detection of target DNA using fluorescent cationic polymer and peptide nucleic acid probes on solid support

    Directory of Open Access Journals (Sweden)

    Leclerc Mario

    2005-04-01

    Full Text Available Abstract Background Nucleic acids detection using microarrays requires labelling of target nucleic acids with fluorophores or other reporter molecules prior to hybridization. Results Using surface-bound peptide nucleic acids (PNA probes and soluble fluorescent cationic polythiophenes, we show a simple and sensitive electrostatic approach to detect and identify unlabelled target nucleic acid on microarray. Conclusion This simple methodology opens exciting possibilities for applied genetic analysis for the diagnosis of infections, identification of genetic mutations, and forensic inquiries. This electrostatic strategy could also be used with other nucleic acid detection methods such as electrochemistry, silver staining, metallization, quantum dots, or electrochemical dyes.

  16. Cationic liposomes enhance targeted delivery and expression of exogenous DNA mediated by N-terminal modified poly(L-lysine)-antibody conjugate in mouse lung endothelial cells.

    Science.gov (United States)

    Trubetskoy, V S; Torchilin, V P; Kennel, S; Huang, L

    1992-07-15

    A new and improved system for targeted gene delivery and expression is described. Transfection efficiency of N-terminal modified poly(L-lysine) (NPLL) conjugated with anti-thrombomodulin antibody 34A can be improved by adding to the system a lipophilic component, cationic liposomes. DNA, antibody conjugate and cationic liposomes form a ternary electrostatic complex which preserves the ability to bind specifically to the target cells. At the same time the addition of liposomes enhance the specific transfection efficiency of antibody-polylysine/DNA binary complex by 10 to 20-fold in mouse lung endothelial cells in culture.

  17. Influence of biological media on the structure and behavior of ferrocene-containing cationic lipid/DNA complexes used for DNA delivery.

    Science.gov (United States)

    Golan, Sharon; Aytar, Burcu S; Muller, John P E; Kondo, Yukishige; Lynn, David M; Abbott, Nicholas L; Talmon, Yeshayahu

    2011-06-07

    Biological media affect the physicochemical properties of cationic lipid-DNA complexes (lipoplexes) and can influence their ability to transfect cells. To develop new lipids for efficient DNA delivery, the influence of serum-containing media on the structures and properties of the resulting lipoplexes must be understood. To date, however, a clear and general picture of how serum-containing media influences the structures of lipoplexes has not been established. Some studies suggest that serum can disintegrate lipoplexes formed using certain types of cationic lipids, resulting in the inhibition of transfection. Other studies have demonstrated that lipoplexes formulated from other lipids are stable in the presence of serum and are able to transfect cells efficiently. In this article, we describe the influence of serum-containing media on lipoplexes formed using the redox-active cationic lipid bis(n-ferrocenylundecyl)dimethylammonium bromide (BFDMA). This lipoplex system promotes markedly decreased levels of transgene expression in COS-7 cells as serum concentrations are increased from 0 to 2, 5, 10, and 50% (v/v). To understand the cause of this decrease in transfection efficiency, we used cryogenic transmission electron microscopy (cryo-TEM) and measurements of zeta potential to characterize lipoplexes in cell culture media supplemented with 0, 2, 5, 10, and 50% serum. Cryo-TEM revealed that in serum-free media BFDMA lipoplexes form onionlike, multilamellar nanostructures. However, the presence of serum in the media caused disassociation of the intact multilamellar lipoplexes. At low serum concentrations (2 and 5%), DNA threads appeared to separate from the complex, leaving the nanostructure of the lipoplexes disrupted. At higher serum concentration (10%), disassociation increased and bundles of multilamellae were discharged from the main multilamellar complex. In contrast, lipoplexes characterized in serum-free aqueous salt (Li(2)SO(4)) medium and in OptiMEM cell

  18. Cationic Lipid-Nucleic Acid Complexes for Gene Delivery And Silencing: Pathways And Mechanisms for Plasmid Dna And Sirna

    Energy Technology Data Exchange (ETDEWEB)

    Ewert, K.K.; Zidovska, A.; Ahmad, A.; Bouxsein, N.F.; Evans, H.M.; McAllister, C.S.; Samuel, C.E.; Safinya, C.R.; /SLAC

    2012-07-17

    Motivated by the promises of gene therapy, there is great interest in developing non-viral lipid-based vectors for therapeutic applications due to their low immunogenicity, low toxicity, ease of production, and the potential of transferring large pieces of DNA into cells. In fact, cationic liposome (CL) based vectors are among the prevalent synthetic carriers of nucleic acids (NAs) currently used in gene therapy clinical trials worldwide. These vectors are studied both for gene delivery with CL-DNA complexes and gene silencing with CL-siRNA (short interfering RNA) complexes. However, their transfection efficiencies and silencing efficiencies remain low compared to those of engineered viral vectors. This reflects the currently poor understanding of transfection-related mechanisms at the molecular and self-assembled levels, including a lack of knowledge about interactions between membranes and double stranded NAs and between CL-NA complexes and cellular components. In this review we describe our recent efforts to improve the mechanistic understanding of transfection by CL-NA complexes, which will help to design optimal lipid-based carriers of DNA and siRNA for therapeutic gene delivery and gene silencing.

  19. Interaction between a cationic porphyrin and ctDNA investigated by SPR, CV and UV-vis spectroscopy.

    Science.gov (United States)

    Xu, Zi-Qiang; Zhou, Bo; Jiang, Feng-Lei; Dai, Jie; Liu, Yi

    2013-10-01

    The interaction between ctDNA and a cationic porphyrin was studied in this work. The binding process was monitored by surface plasmon resonance (SPR) spectroscopy in detail. The association, dissociation rate constants and the binding constants calculated by global analysis were 2.4×10(2)±26.4M(-1)s(-1), 0.011±0.0000056s(-1) and 2.18×10(4)M(-1), respectively. And the results were confirmed by cyclic voltammetry and UV-vis absorption spectroscopy. The binding constants obtained from cyclic voltammetry and UV-vis absorption spectroscopy were 8.28×10(4)M(-1) and 6.73×10(4)M(-1) at 298K, respectively. The covalent immobilization methodology of ctDNA onto gold surface modified with three different compounds was also investigated by SPR. These compounds all contain sulfydryl but with different terminated functional groups. The results indicated that the 11-MUA (HS(CH2)10COOH)-modified gold film is more suitable for studying the DNA-drug interaction.

  20. Assessment of SYBR green I dye-based fluorescence assay for screening antimalarial activity of cationic peptides and DNA intercalating agents.

    Science.gov (United States)

    Bhatia, Rakesh; Gautam, Ankur; Gautam, Shailendra K; Mehta, Divya; Kumar, Vinod; Raghava, Gajendra P S; Varshney, Grish C

    2015-05-01

    The SYBR green I (SG) dye-based fluorescence assay for screening antimalarial compounds is based on direct quantitation of parasite DNA. We show that DNA-interacting cationic cell-penetrating peptides (CPPs) and intercalating agents compete with SG dye to bind to DNA. Therefore, readouts of this assay, unlike those of the [(3)H]hypoxanthine incorporation assay, for the antimalarial activity of the above DNA binding agents may be erroneous. In the case of CPPs, false readouts can be improved by the removal of excess peptides. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

  1. Direct measurement of the intermolecular forces between counterion-condensed DNA double helices. Evidence for long range attractive hydration forces.

    Science.gov (United States)

    Rau, D C; Parsegian, V A

    1992-01-01

    Rather than acting by modifying van der Waals or electrostatic double layer interactions or by directly bridging neighboring molecules, polyvalent ligands bound to DNA double helices appear to act by reconfiguring the water between macromolecular surfaces to create attractive long range hydration forces. We have reached this conclusion by directly measuring the repulsive forces between parallel B-form DNA double helices pushed together from the separations at which they have self organized into hexagonal arrays of parallel rods. For all of the wide variety of "condensing agents" from divalent Mn to polymeric protamines, the resulting intermolecular force varies exponentially with a decay rate of 1.4-1.5 A, exactly one-half that seen previously for hydration repulsion. Such behavior qualitatively contradicts the predictions of all electrostatic double layer and van der Waals force potentials previously suggested. It fits remarkably well with the idea, developed and tested here, that multivalent counterion adsorption reorganizes the water at discrete sites complementary to unadsorbed sites on the apposing surface. The measured strength and range of these attractive forces together with their apparent specificity suggest the presence of a previously unexpected force in molecular organization.

  2. Cationic solid-lipid nanoparticles are as efficient as electroporation in DNA vaccination against visceral leishmaniasis in mice.

    Science.gov (United States)

    Saljoughian, N; Zahedifard, F; Doroud, D; Doustdari, F; Vasei, M; Papadopoulou, B; Rafati, S

    2013-12-01

    The use of an appropriate delivery system has recently emerged as a promising approach for the development of effective vaccination against visceral leishmaniasis (VL). Here, we compare two vaccine delivery systems, namely electroporation and cationic solid-lipid nanoparticle (cSLN) formulation, to administer a DNA vaccine harbouring the L. donovani A2 antigen along with L. infantum cysteine proteinases [CPA and CPB without its unusual C-terminal extension (CPB(-CTE) )] and evaluate their potential against L. infantum challenge. Prime-boost administration of the pcDNA-A2-CPA-CPB(-CTE) delivered by either electroporation or cSLN formulation protects BALB/c mice against L. infantum challenge and that protective immunity is associated with high levels of IFN-γ and lower levels of IL-10 production, leading to a strong Th1 immune response. At all time points, the ratio of IFN-γ: IL-10 induced upon restimulation with rA2-rCPA-rCPB and F/T antigens was significantly higher in vaccinated animals. Moreover, Th2-efficient protection was elicited through a high humoral immune response. Nitric oxide production, parasite burden and histopathological analysis were also in concordance with other findings. Overall, these data indicate that similar to the electroporation delivery system, cSLNs as a nanoscale vehicle of Leishmania antigens could improve immune response, hence indicating the promise of these strategies against visceral leishmaniasis.

  3. Conformational conversion of DNA G-quadruplex induced by a cationic porphyrin.

    Science.gov (United States)

    Zhang, Huijuan; Xiao, Xiao; Wang, Peng; Pang, Siping; Qu, Feng; Ai, Xicheng; Zhang, Jianping

    2009-09-15

    The interactions between cationic meso-tetrakis(4-(N-methylpyridiumyl))porphyrin (TMPyP4) and the G-quadruplex (G4) of human telomeric single-strand oligonucleotide d(TTAGGG)(2) (S12) have been investigated by means of circular dichroism (CD), UV-visible absorption and fluorescence spectroscopies. It is found that TMPyP4 can preferentially induce the conformational conversion of the G4 structure from the parallel type to the parallel/antiparallel mixture in the presence of K(+), and that it can directly induce the formation of antiparallel G4 structure from the single-strand oligonucleotide S12 in the absence of K(+). Furthermore, the comparable experiments of TMPyP4 with two single-strand oligonucleotides S6 d(TTAGGG) and S24 d(TAGGG(TTAGGG)(3)T) in the absence of K(+) show that TMPyP4 can also induce the formation of antiparallel G4 from S24 but not from S6, indicating that the end-loops of the G4 structure are the key factors for the formation of G4 induced by TMPyP4.

  4. CL22 - a novel cationic peptide for efficient transfection of mammalian cells.

    Science.gov (United States)

    Haines, A M; Irvine, A S; Mountain, A; Charlesworth, J; Farrow, N A; Husain, R D; Hyde, H; Ketteringham, H; McDermott, R H; Mulcahy, A F; Mustoe, T L; Reid, S C; Rouquette, M; Shaw, J C; Thatcher, D R; Welsh, J H; Williams, D E; Zauner, W; Phillips, R O

    2001-01-01

    Condensing peptide-DNA complexes have great potential as nonviral agents for gene delivery. To date, however, such complexes have given transfection activities greatly inferior to adenovirus and somewhat inferior to cationic lipid-DNA complexes, even for cell lines and primary cells in vitro. We report here the identification of a novel condensing peptide, CL22, which forms DNA complexes that efficiently transfect many cell lines, as well as primary dendritic and endothelial cells. We report studies with sequence and structure variants that define some properties of the peptide that contribute to efficient transfection. We demonstrate that the superior transfection activity of CL22 compared with other DNA condensing peptides is conferred at a step after uptake of the complexes into cells. We show that CL22-DNA complexes have transfection activity that is at least equivalent to the best available nonviral agents.

  5. Nucleic acid binding properties of a helix stabilising nucleoid protein from the thermoacidophilic archaeon Sulfolobus acidocaldarius that condenses DNA into compact structures.

    Science.gov (United States)

    Celestina, F; Suryanarayana, T

    1995-12-01

    Helix stabilising nucleoid protein (HSNP-C') from an acidothermophilic archaeon Sulfolobus acidocaldarius has been characterised with respect to interaction with nucleic acids by gel retardation assay, binding to nucleic acid columns, fluorescence titrations and electron microscopy. The protein exists in solution as very large multimeric aggregates as indicated by cross-linking studies. The protein binds strongly and co-operatively to double stranded DNA. Electron microscopy of the complexes of the protein with DNA shows compact structures suggesting that the protein condenses DNA.

  6. Cell interactions in concanavalin A activated cation flux and DNA synthesis of mouse lymphocytes

    DEFF Research Database (Denmark)

    Owens, T; Kaplan, J G

    1980-01-01

    Co-culture at constant cell density of nude mouse spleen cells (by themselves unresponsive to the T-cell mitogen concanavalin A (Con A)), with congenic T-enriched lymphocyte suspensions and Con A caused anomalously high activation of K+ transport (measured by 86Rb uptake) and of incorporation...... of thymidine into DNA; the expected dilution of these two responses by nude spleen cells did not occur. However, if the nude splenocytes were added immediately prior to assay to the enriched T cells that had been precultured in presence of Con A, the expected dilution of the activated T-cell responses occurred......; both 86Rb uptake and thymidine incorporation were reduced proportionally to the degree of dilution of the T cells by the nonresponding cells. These data indicate that during co-culture in presence of Con A there is interaction between the T cells, capable of responding to mitogens, and the nude spleen...

  7. 32P-postlabelling analysis of DNA adducts in the skin of mice treated with petrol and diesel engine lubricating oils and exhaust condensates.

    Science.gov (United States)

    Schoket, B; Hewer, A; Grover, P L; Phillips, D H

    1989-08-01

    Samples of unused or used petrol and diesel engine lubricating oils were applied to the shaved dorsal skin of 4- to 6-week-old male Parkes mice, either as a single treatment (50 microliters/mouse) or as four consecutive daily treatments (50 microliters/application). DNA isolated from the skin 24 h after the final treatment was digested to 3'-mononucleotides and analysed by 32P-postlabelling for the presence of aromatic adducts. Enhancement of sensitivity using butanol extraction or nuclease P1 digestion of the DNA hydrolysates led to the detection of up to eight adduct spots on polyethyleneimine-cellulose thin-layer chromatograms with samples of DNA from skin treated with used engine oils, at levels of 40-150 amol total adducts/micrograms DNA. Multiple treatments with the used oils gave rise to similar patterns of adducts in lung DNA. A single treatment of mouse skin with petrol engine exhaust condensate (50 microliters), or diesel engine exhaust condensate (50 microliters), containing 20 and 46 micrograms benzo[a]pyrene (BaP)/g respectively, gave rise to approximately 75 amol total adducts/micrograms DNA in skin. A significant proportion, 31 and 48% respectively, of the adducts formed by the petrol and diesel engine exhaust condensates co-chromatographed with the major BaP-DNA adduct, but with the used engine oils, only petrol engine oil, and not diesel engine oil, produced significant amounts of an adduct (22% of total) that corresponded to the BaP-DNA adduct.

  8. DNA-based vaccination against hepatitis B virus using dissolving microneedle arrays adjuvanted by cationic liposomes and CpG ODN.

    Science.gov (United States)

    Qiu, Yuqin; Guo, Lei; Zhang, Suohui; Xu, Bai; Gao, Yunhua; Hu, Yan; Hou, Jun; Bai, Bingke; Shen, Honghui; Mao, Panyong

    2016-09-01

    DNA vaccines are simple to produce and can generate strong cellular and humoral immune response, making them attractive vaccine candidates. However, a major shortcoming of DNA vaccines is their poor immunogenicity when administered intramuscularly. Transcutaneous immunization (TCI) via microneedles is a promising alternative delivery route to enhance the vaccination efficacy. A novel dissolving microneedle array (DMA)-based TCI system loaded with cationic liposomes encapsulated with hepatitis B DNA vaccine and adjuvant CpG ODN was developed and characterized. The pGFP expression in mouse skin using DMA was imaged over time. In vivo immunity tests in mice were performed to observe the capability of DMA to induce immune response after delivery of DNA. The results showed that pGFP could be delivered into skin by DMA and expressed in skin. Further, the amount of expressed GFP was likely to peak at day 4. The immunity tests showed that the DMA-based DNA vaccination could induce effective immune response. CpG ODN significantly improved the immune response and achieved the shift of immune type from predominate Th2 type to a balance Th1/Th2 type. The cationic liposomes could further improve the immunogenicity of DNA vaccine. In conclusion, the novel DMA-based TCI system can effectively deliver hepatitis B DNA vaccine into skin, inducing effective immune response and change the immune type by adjuvant CpG ODN.

  9. Stress induced by premature chromatin condensation triggers chromosome shattering and chromothripsis at DNA sites still replicating in micronuclei or multinucleate cells when primary nuclei enter mitosis.

    Science.gov (United States)

    Terzoudi, Georgia I; Karakosta, Maria; Pantelias, Antonio; Hatzi, Vasiliki I; Karachristou, Ioanna; Pantelias, Gabriel

    2015-11-01

    Combination of next-generation DNA sequencing, single nucleotide polymorphism array analyses and bioinformatics has revealed the striking phenomenon of chromothripsis, described as complex genomic rearrangements acquired in a single catastrophic event affecting one or a few chromosomes. Via an unproven mechanism, it is postulated that mechanical stress causes chromosome shattering into small lengths of DNA, which are then randomly reassembled by DNA repair machinery. Chromothripsis is currently examined as an alternative mechanism of oncogenesis, in contrast to the present paradigm that considers a stepwise development of cancer. While evidence for the mechanism(s) underlying chromosome shattering during cancer development remains elusive, a number of hypotheses have been proposed to explain chromothripsis, including ionizing radiation, DNA replication stress, breakage-fusion-bridge cycles, micronuclei formation and premature chromosome compaction. In the present work, we provide experimental evidence on the mechanistic basis of chromothripsis and on how chromosomes can get locally shattered in a single catastrophic event. Considering the dynamic nature of chromatin nucleoprotein complex, capable of rapid unfolding, disassembling, assembling and refolding, we first show that chromatin condensation at repairing or replicating DNA sites induces the mechanical stress needed for chromosome shattering to ensue. Premature chromosome condensation is then used to visualize the dynamic nature of interphase chromatin and demonstrate that such mechanical stress and chromosome shattering can also occur in chromosomes within micronuclei or asynchronous multinucleate cells when primary nuclei enter mitosis. Following an aberrant mitosis, chromosomes could find themselves in the wrong place at the wrong time so that they may undergo massive DNA breakage and rearrangement in a single catastrophic event. Specifically, our results support the hypothesis that premature chromosome

  10. Condensation patterns of prophase/prometaphase chromosome are correlated with H4K5 histone acetylation and genomic DNA contents in plants.

    Science.gov (United States)

    Feitoza, Lidiane; Costa, Lucas; Guerra, Marcelo

    2017-01-01

    Mitotic prophase chromosome condensation plays an essential role in nuclear division being therefore regulated by highly conserved mechanisms. However, degrees of chromatin condensation in prophase-prometaphase cells may vary along the chromosomes resulting in specific condensation patterns. We examined different condensation patterns (CPs) of prophase and prometaphase chromosomes and investigated their relationship with genome size and distribution of histone H4 acetylated at lysine 5 (H4K5ac) in 17 plant species. Our results showed that most species with small genomes (2C < 5 pg) (Arachis pusilla, Bixa orellana, Costus spiralis, Eleutherine bulbosa, Indigofera campestris, Phaseolus lunatus, P. vulgaris, Poncirus trifoliata, and Solanum lycopersicum) displayed prophase chromosomes with late condensing terminal regions that were highly enriched in H4K5ac, and early condensing regions with apparently non-acetylated proximal chromatin. The species with large genomes (Allium cepa, Callisia repens, Araucaria angustifolia and Nothoscordum pulchellum) displayed uniformly condensed and acetylated prophase/prometaphase chromosomes. Three species with small genomes (Eleocharis geniculata, Rhynchospora pubera, and R. tenuis) displayed CP and H4K5ac labeling patterns similar to species with large genomes, whereas a forth species (Emilia sonchifolia) exhibited a gradual chromosome labeling, being more acetylated in the terminal regions and less acetylated in the proximal ones. The nucleolus organizer chromatin was the only chromosomal region that in prometaphase or metaphase could be hyperacetylated, hypoacetylated or non-acetylated, depending on the species. Our data indicate that the CP of a plant chromosome complement is influenced but not exclusively determined by nuclear and chromosomal DNA contents, whereas the CP of individual chromosomes is clearly correlated with H4K5ac distribution.

  11. Anchoring of self-assembled plasmid DNA/ anti-DNA antibody/cationic lipid micelles on bisphosphonate-modified stent for cardiovascular gene delivery

    Directory of Open Access Journals (Sweden)

    Ma G

    2013-03-01

    Full Text Available Guilei Ma,1,# Yong Wang,1,# Ilia Fishbein,2 Mei Yu,1 Linhua Zhang,1 Ivan S Alferiev,2 Jing Yang,1 Cunxian Song,1 Robert J Levy2 1Institute of Biomedical Engineering, Chinese Academy of Medical Sciences and Peking Union Medical College, Tianjin, People's Republic of China; 2Children's Hospital of Philadelphia, Abramson Research Building, Philadelphia, PA, USA #These authors contributed equally to this work Purpose: To investigate the anchoring of plasmid DNA/anti-DNA antibody/cationic lipid tri-complex (DAC micelles onto bisphosphonate-modified 316 L coronary stents for cardiovascular site-specific gene delivery. Methods: Stents were first modified with polyallylamine bisphosphonate (PAA-BP, thereby enabling the retention of a PAA-BP molecular monolayer that permits the anchoring (via vector-binding molecules of DAC micelles. DAC micelles were then chemically linked onto the PAA-BP-modified stents by using N-succinimidyl-3-(2-pyridyldithiol-propionate (SPDP as a crosslinker. Rhodamine-labeled DNA was used to assess the anchoring of DAC micelles, and radioactive-labeled antibody was used to evaluate binding capacity and stability. DAC micelles (encoding green fluorescent protein were tethered onto the PAA-BP-modified stents, which were assessed in cell culture. The presence of a PAA-BP molecular monolayer on the steel surface was confirmed by X-ray photoelectron spectroscopy and atomic force microscope analysis. Results: The anchoring of DAC micelles was generally uniform and devoid of large-scale patches of defects. Isotopic quantification confirmed that the amount of antibody chemically linked on the stents was 17-fold higher than that of the physical adsorbed control stents and its retention time was also significantly longer. In cell culture, numerous green fluorescent protein-positive cells were found on the PAA-BP modified stents, which demonstrated high localization and efficiency of gene delivery. Conclusion: The DAC micelle

  12. Cationic Liposomes Modified with Polyallylamine as a Gene Carrier: Preparation, Characterization and Transfection Efficiency Evaluation

    Directory of Open Access Journals (Sweden)

    Reza Kazemi Oskuee

    2016-12-01

    Full Text Available Purpose: Cationic polymers and cationic liposomes have shown to be effective non-viral gene delivery vectors. In this study, we tried to improve the transfection efficiency by employing the advantages of both. Methods: For this purpose, modified polyallylamines (PAAs were synthesized. These modifications were done through the reaction of PAA (15 KDa with acrylate and 6-bromoalkanoic acid derivatives. Liposomes comprising of these cationic polymers and cationic lipid were prepared and extruded through polycarbonate filters to obtain desired size. Liposome-DNA nanocomplexes were prepared in three carrier to plasmid (C/P ratios. Size, zeta potential and DNA condensation ability of each complex were characterized separately and finally transfection efficiency and cytotoxicity of prepared vectors were evaluated in Neuro2A cell line. Results: The results showed that mean particle size of all these nanocomplexes was lower than 266 nm with surface charge of 22.0 to 33.9 mV. Almost the same condensation pattern was observed in all vectors and complete condensation was occurred at C/P ratio of 1.5. The lipoplexes containing modified PAA 15 kDa with 10% hexyl acrylate showed the highest transfection efficacy and lowest cytotoxicity in C/P ratio of 0.5. Conclusion: In some cases nanocomplexes consisting of cationic liposome and modified PAA showed better transfection activity and lower cytotoxicity compared to PAA.

  13. Study the effects of metallic ions on the combination of DNA and histones with molecular combing technique

    Institute of Scientific and Technical Information of China (English)

    LIU Yuying; WANG Pengye; DOU Shuoxing; XIE Ping; WANG Weichi; YIN Huawei

    2005-01-01

    The effects of monovalent (Na+, K+) and divalent (Mg2+, Ca2+, Mn2+) ions on the interaction between DNA and histone are studied using the molecular combing technique. λ-DNA molecules and DNA-histone complexes incubated with metal cations (Na+, K+, Mg2+, Ca2+, Mn2+) are stretched on hydrophobic surfaces, and directly observed by fluorescence microscopy. The results indicate that when these cations are added into the DNA solution, the fluorescence intensities of the stained DNA are reduced differently. The monovalent cations (Na+, K+) inhibit binding of histone to DNA. The divalent cations (Mg2+, Ca2+, Mn2+) enhance significantly the binding of histone to DNA and the binding of the DNA-histone complex to the hydrophobic surface. Mn2+ also induces condensation and aggregation of the DNA- histone complex.

  14. A comparison of the effectiveness of cationic polymers poly-L-lysine (PLL) and polyethylenimine (PEI) for non-viral delivery of plasmid DNA to bone marrow stromal cells (BMSC).

    Science.gov (United States)

    Farrell, Laura-Lee; Pepin, Joel; Kucharski, Cezary; Lin, Xiaoyue; Xu, Zhenghe; Uludag, Hasan

    2007-03-01

    Bone marrow stromal cells (BMSC) represent an important cell phenotype for pursuit of successful gene therapy. Non-viral methods to enable expression of exogenous genes in BMSC will accelerate clinical application of gene therapy, without the concerns associated with the viral means of gene transfer. Towards this end, this study investigated the potential of cationic polymers poly-L-lysine (PLL) and branched polyethylenimine (PEI) as gene carriers for modification of BMSC. Both polymers rapidly (approximately 30 min) condensed a 4.2 kb Enhanced Green Fluorescent Protein (pEGFP-N2) plasmid into 100-200 nm particles. PLL and PEI were both readily internalized with BMSC with >80% of BMSC exhibiting polymer uptake by flow cytometric analysis. The relative uptake of PEI, however, was significantly higher as compared to the PLL. The majority of the BMSC (>60%) exhibited nuclear presence of the polymers as analyzed by fluorescent microscopy. Although both polymers were able to deliver the pEGFP-N2 into the cells under microscopic evaluation, only a small fraction of the cells (PLL and PEI readily displayed cellular uptake, but PEI was more effective in delivering plasmid DNA intracellularly, which was likely the underlying basis for a more sustained gene expression.

  15. Effects of inhibitors of DNA, RNA, and protein synthesis on frequencies and types of premature chromosome condensation from x-ray induced micronuclei. [Cytosine arabinoside, azathioprine, thymidine, trenimon

    Energy Technology Data Exchange (ETDEWEB)

    Madle, S.; Nowak, J.; Obe, G.

    1976-10-28

    Cells containing x-ray induced micronuclei were treated for a few hours before fixation with inhibitors of DNA synthesis (cytosine arabinoside; azathioprine; thymidine; trenimon), of RNA synthesis (actinomycin D; ethidium bromide), and of protein synthesis (puromycin). Only the inhibitors of DNA synthesis lead to a significant suppression of the frequencies of mitoses with micronucleus derived premature chromosome condensation (PCC). We tend to interpret the result as follows: Micronuclei that are in the G1 phase of their cell cycles are accumulated at the G1/S border or in the early S phase of their cell cycles under the influence of the inhibitors of the DNA synthesis. Micronuclei blocked in this way cannot be induced to undergo PCC and seem to disappear from the cells.

  16. Nuclear DNA methylation and chromatin condensation phenotypes are distinct between normally proliferating/aging, rapidly growing/immortal, and senescent cells.

    Science.gov (United States)

    Oh, Jin Ho; Gertych, Arkadiusz; Tajbakhsh, Jian

    2013-03-01

    This study reports on probing the utility of in situ chromatin texture features such as nuclear DNA methylation and chromatin condensation patterns - visualized by fluorescent staining and evaluated by dedicated three-dimensional (3D) quantitative and high-throughput cell-by-cell image analysis - in assessing the proliferative capacity, i.e. growth behavior of cells: to provide a more dynamic picture of a cell population with potential implications in basic science, cancer diagnostics/prognostics and therapeutic drug development. Two types of primary cells and four different cancer cell lines were propagated and subjected to cell-counting, flow cytometry, confocal imaging, and 3D image analysis at various points in culture. Additionally a subset of primary and cancer cells was accelerated into senescence by oxidative stress. DNA methylation and chromatin condensation levels decreased with declining doubling times when primary cells aged in culture with the lowest levels reached at the stage of proliferative senescence. In comparison, immortal cancer cells with constant but higher doubling times mostly displayed lower and constant levels of the two in situ-derived features. However, stress-induced senescent primary and cancer cells showed similar levels of these features compared with primary cells that had reached natural growth arrest. With regards to global DNA methylation and chromatin condensation levels, aggressively growing cancer cells seem to take an intermediate level between normally proliferating and senescent cells. Thus, normal cells apparently reach cancer-cell equivalent stages of the two parameters at some point in aging, which might challenge phenotypic distinction between these two types of cells. Companion high-resolution molecular profiling could provide information on possible underlying differences that would explain benign versus malign cell growth behaviors.

  17. Cation Coordination Alters the Conformation of a Thrombin-Binding G-Quadruplex DNA Aptamer That Affects Inhibition of Thrombin.

    Science.gov (United States)

    Zavyalova, Elena; Tagiltsev, Grigory; Reshetnikov, Roman; Arutyunyan, Alexander; Kopylov, Alexey

    2016-10-01

    Thrombin-binding aptamers are promising anticoagulants. HD1 is a monomolecular antiparallel G-quadruplex with two G-quartets linked by three loops. Aptamer-thrombin interactions are mediated with two TT-loops that bind thrombin exosite I. Several cations were shown to be coordinated inside the G-quadruplex, including K(+), Na(+), NH4(+), Ba(2+), and Sr(2+); on the contrary, Mn(2+) was coordinated in the grooves, outside the G-quadruplex. K(+) or Na(+) coordination provides aptamer functional activity. The effect of other cations on aptamer functional activity has not yet been described, because of a lack of relevant tests. Interactions between aptamer HD1 and a series of cations were studied. A previously developed enzymatic method was applied to evaluate aptamer inhibitory activity. The structure-function correlation was studied using the characterization of G-quadruplex conformation by circular dichroism spectroscopy. K(+) coordination provided the well-known high inhibitory activity of the aptamer, whereas Na(+) coordination supported low activity. Although NH4(+) coordination yielded a typical antiparallel G-quadruplex, no inhibitory activity was shown; a similar effect was observed for Ba(2+) and Sr(2+) coordination. Mn(2+) coordination destabilized the G-quadruplex that drastically diminished aptamer inhibitory activity. Therefore, G-quadruplex existence per se is insufficient for aptamer inhibitory activity. To elicit the nature of these effects, we thoroughly analyzed nuclear magnetic resonance (NMR) and X-ray data on the structure of the HD1 G-quadruplex with various cations. The most reasonable explanation is that cation coordination changes the conformation of TT-loops, affecting thrombin binding and inhibition. HD1 counterparts, aptamers 31-TBA and NU172, behaved similarly with some distinctions. In 31-TBA, an additional duplex module stabilized antiparallel G-quadruplex conformation at high concentrations of divalent cations; whereas in NU172, a

  18. Evaluation of effects of bivalent cations on the formation of purine-rich triple-helix DNA by ESI-FT-MS.

    Science.gov (United States)

    Wan, Cuihong; Cui, Meng; Song, Fengrui; Liu, Zhiqiang; Liu, Shuying

    2009-07-01

    The GGA triplet repeats are widely dispersed throughout eukaryotic genomes. (GGA)n or (GGT)n oligonucleotides can interact with double-stranded DNA containing (GGA:CCT)n to form triple-stranded DNA. The effects of 8 divalent metal ions (3 alkaline-earth metals and 5 transition metals) on formation of these purine-rich triple-helix DNA were investigated by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FT-MS). In the absence of metal ions, no triplex but single-strand, duplex, and purine homodimer ions were observed in mass spectra. The triple-helix DNA complexes were observed only in the presence of certain divalent ions. The effects of different divalent cations on the formation of purine-rich triplexes were compared. Transition-metal ions, especially Co(2+) and Ni(2+), significantly boost the formation of triple-helix DNA, whereas alkaline-earth metal ions have no positive effects on triplex formation. In addition, Ba(2+) is notably beneficial to the formation of homodimer instead of triplex.

  19. Binding of Cationic Bis-porphyrins Linked with p- or m-Xylylenediamine and Their Zinc(II Complexes to Duplex DNA

    Directory of Open Access Journals (Sweden)

    Tadayuki Uno

    2008-12-01

    Full Text Available Spectroscopic, viscometric, and molecular docking analysis of binding of cationic bis-porphyrins linked with p- or m-xylylenediamine (H2pXy and H2mXy and their zinc(II complexes (ZnpXy and ZnmXy to duplex DNA are described. H2pXy and H2mXy bound to calf thymus DNA (CTDNA stronger than unichromophoric H2TMPyP, and showed exciton-type induced circular dichroism spectra of their Soret bands. The H2TMPyP-like units of the metal-free bis-porphyrins did not intercalate into CTDNA, and thus the binding mode is outside binding with intramolecular stacking. ZnpXy showed favorable binding to A·T over G·C region, and should lie in the major groove of A·T region.

  20. Internal charge transfer based ratiometric interaction of anionic surfactant with calf thymus DNA bound cationic surfactant: Study I

    Science.gov (United States)

    Mukherjee, Abhijit; Chaudhuri, Tandrima; Moulik, Satya Priya; Banerjee, Manas

    2016-01-01

    Cetyl trimethyl ammonium bromide (CTAB) binds calf thymus (ct-) DNA like anionic biopolymers electrostatically and established equilibrium both in the ground as well as in excited state in aqueous medium at pH 7. Anionic sodium dodecyl sulfate (SDS) does not show even hydrophobic interaction with ct-DNA at low concentration. On contrary, SDS can establish well defined equilibrium with DNA bound CTAB in ground state where the same CTAB-DNA isosbestic point reappears. First report of internal charge transfer (ICT) based binding of CTAB with ct-DNA as well as ICT based interaction of anionic SDS with DNA bound CTAB that shows dynamic quenching contribution also. The reappearance of anodic peak and slight increase in cathodic peak current with increasing concentration (at lower range) of anionic SDS, possibly reflect the release of CTAB from DNA bound CTAB by SDS.

  1. Internal charge transfer based ratiometric interaction of anionic surfactant with calf thymus DNA bound cationic surfactant: Study I.

    Science.gov (United States)

    Mukherjee, Abhijit; Chaudhuri, Tandrima; Moulik, Satya Priya; Banerjee, Manas

    2016-01-01

    Cetyl trimethyl ammonium bromide (CTAB) binds calf thymus (ct-) DNA like anionic biopolymers electrostatically and established equilibrium both in the ground as well as in excited state in aqueous medium at pH 7. Anionic sodium dodecyl sulfate (SDS) does not show even hydrophobic interaction with ct-DNA at low concentration. On contrary, SDS can establish well defined equilibrium with DNA bound CTAB in ground state where the same CTAB-DNA isosbestic point reappears. First report of internal charge transfer (ICT) based binding of CTAB with ct-DNA as well as ICT based interaction of anionic SDS with DNA bound CTAB that shows dynamic quenching contribution also. The reappearance of anodic peak and slight increase in cathodic peak current with increasing concentration (at lower range) of anionic SDS, possibly reflect the release of CTAB from DNA bound CTAB by SDS.

  2. Actinide cation-cation complexes

    Energy Technology Data Exchange (ETDEWEB)

    Stoyer, Nancy Jane [Univ. of California, Berkeley, CA (United States)

    1994-12-01

    The +5 oxidation state of U, Np, Pu, and Am is a linear dioxo cation (AnO2+) with a formal charge of +1. These cations form complexes with a variety of other cations, including actinide cations. Other oxidation states of actinides do not form these cation-cation complexes with any cation other than AnO2+; therefore, cation-cation complexes indicate something unique about AnO2+ cations compared to actinide cations in general. The first cation-cation complex, NpO2+•UO22+, was reported by Sullivan, Hindman, and Zielen in 1961. Of the four actinides that form AnO2+ species, the cation-cation complexes of NpO2+ have been studied most extensively while the other actinides have not. The only PuO2+ cation-cation complexes that have been studied are with Fe3+ and Cr3+ and neither one has had its equilibrium constant measured. Actinides have small molar absorptivities and cation-cation complexes have small equilibrium constants; therefore, to overcome these obstacles a sensitive technique is required. Spectroscopic techniques are used most often to study cation-cation complexes. Laser-Induced Photacoustic Spectroscopy equilibrium constants for the complexes NpO2+•UO22+, NpO2+•Th4+, PuO2+•UO22+, and PuO2+•Th4+ at an ionic strength of 6 M using LIPAS are 2.4 ± 0.2, 1.8 ± 0.9, 2.2 ± 1.5, and ~0.8 M-1.

  3. Effects of pulling forces, osmotic pressure, condensing agents and viscosity on the thermodynamics and kinetics of DNA ejection from bacteriophages to bacterial cells: a computational study

    Science.gov (United States)

    Petrov, Anton S.; Douglas, Scott S.; Harvey, Stephen C.

    2013-03-01

    In this work, we report on simulations of double-stranded DNA (dsDNA) ejection from bacteriophage ϕ29 into a bacterial cell. The ejection was studied with a coarse-grained model, in which viral dsDNA was represented by beads on a torsion-less string. The bacteriophage’s capsid and the bacterial cell were defined by sets of spherical constraints. To account for the effects of the viscous medium inside the bacterial cell, the simulations were carried out using a Langevin dynamics protocol. Our simplest simulations (involving constant viscosity and no external biasing forces) produced results compatible with the push-pull model of DNA ejection, with an ejection rate significantly higher in the first part of ejection than in the latter parts. Additionally, we performed more complicated simulations, in which we included additional factors such as external forces, osmotic pressure, condensing agents and ejection-dependent viscosity. The effects of these factors (independently and in combination) on the thermodynamics and kinetics of DNA ejection were studied. We found that, in general, the dependence of ejection forces and ejection rates on the amount of DNA ejected becomes more complex if the ejection is modeled with a broader, more realistic set of parameters and influences (such as variation in the solvent’s viscosity and the application of an external force). However, certain combinations of factors and numerical parameters led to the opposition of some ejection-driving and ejection-inhibiting influences, ultimately causing an apparent simplification of the ejection profiles.

  4. Development of polymeric-cationic peptide composite nanoparticles, a nanoparticle-in-nanoparticle system for controlled gene delivery.

    Science.gov (United States)

    Jain, Arvind K; Massey, Ashley; Yusuf, Helmy; McDonald, Denise M; McCarthy, Helen O; Kett, Vicky L

    2015-01-01

    We report the formulation of novel composite nanoparticles that combine the high transfection efficiency of cationic peptide-DNA nanoparticles with the biocompatibility and prolonged delivery of polylactic acid-polyethylene glycol (PLA-PEG). The cationic cell-penetrating peptide RALA was used to condense DNA into nanoparticles that were encapsulated within a range of PLA-PEG copolymers. The composite nanoparticles produced exhibited excellent physicochemical properties including size 80%. Images of the composite nanoparticles obtained with a new transmission electron microscopy staining method revealed the peptide-DNA nanoparticles within the PLA-PEG matrix. Varying the copolymers modulated the DNA release rate >6 weeks in vitro. The best formulation was selected and was able to transfect cells while maintaining viability. The effect of transferrin-appended composite nanoparticles was also studied. Thus, we have demonstrated the manufacture of composite nanoparticles for the controlled delivery of DNA.

  5. Water Condensation

    DEFF Research Database (Denmark)

    Jensen, Kasper Risgaard; Fojan, Peter; Jensen, Rasmus Lund

    2014-01-01

    The condensation of water is a phenomenon occurring in multiple situations in everyday life, e.g., when fog is formed or when dew forms on the grass or on windows. This means that this phenomenon plays an important role within the different fields of science including meteorology, building physics......, and chemistry. In this review we address condensation models and simulations with the main focus on heterogeneous condensation of water. The condensation process is, at first, described from a thermodynamic viewpoint where the nucleation step is described by the classical nucleation theory. Further, we address...

  6. Gastrointestinal Bacterial and Methanogenic Archaea Diversity Dynamics Associated with Condensed Tannin-Containing Pine Bark Diet in Goats Using 16S rDNA Amplicon Pyrosequencing

    Directory of Open Access Journals (Sweden)

    Byeng R. Min

    2014-01-01

    Full Text Available Eighteen Kiko-cross meat goats (n=6 were used to collect gastrointestinal (GI bacteria and methanogenic archaea for diversity measures when fed condensed tannin-containing pine bark (PB. Three dietary treatments were tested: control diet (0% PB and 30% wheat straw (WS; 0.17% condensed tannins (CT dry matter (DM; 15% PB and 15% WS (1.6% CT DM, and 30% PB and 0% WS (3.2% CT DM. A 16S rDNA bacterial tag-encoded FLX amplicon pyrosequencing technique was used to characterize and elucidate changes in GI bacteria and methanogenic archaea diversity among the diets. Proteobacteria was the most dominant phylum in goats with mean relative abundance values ranging from 39.7 (30% PB to 46.5% (control and 47.1% (15% PB. Other phyla individually accounted for fewer than 25% of the relative abundance observed. Predominant methanogens were Methanobrevibacter (75, 72, and 49%, Methanosphaera (3.3, 2.3, and 3.4%, and Methanobacteriaceae (1.2, 0.6, and 0.7% population in control, 15, and 30% PB, respectively. Among methanogens, Methanobrevibacter was linearly decreased (P=0.05 with increasing PB supplementation. These results indicate that feeding PB selectively altered bacteria and methanogenic archaeal populations in the GI tract of goats.

  7. Gastrointestinal Bacterial and Methanogenic Archaea Diversity Dynamics Associated with Condensed Tannin-Containing Pine Bark Diet in Goats Using 16S rDNA Amplicon Pyrosequencing.

    Science.gov (United States)

    Min, Byeng R; Solaiman, Sandra; Shange, Raymon; Eun, Jong-Su

    2014-01-01

    Eighteen Kiko-cross meat goats (n = 6) were used to collect gastrointestinal (GI) bacteria and methanogenic archaea for diversity measures when fed condensed tannin-containing pine bark (PB). Three dietary treatments were tested: control diet (0% PB and 30% wheat straw (WS); 0.17% condensed tannins (CT) dry matter (DM)); 15% PB and 15% WS (1.6% CT DM), and 30% PB and 0% WS (3.2% CT DM). A 16S rDNA bacterial tag-encoded FLX amplicon pyrosequencing technique was used to characterize and elucidate changes in GI bacteria and methanogenic archaea diversity among the diets. Proteobacteria was the most dominant phylum in goats with mean relative abundance values ranging from 39.7 (30% PB) to 46.5% (control) and 47.1% (15% PB). Other phyla individually accounted for fewer than 25% of the relative abundance observed. Predominant methanogens were Methanobrevibacter (75, 72, and 49%), Methanosphaera (3.3, 2.3, and 3.4%), and Methanobacteriaceae (1.2, 0.6, and 0.7%) population in control, 15, and 30% PB, respectively. Among methanogens, Methanobrevibacter was linearly decreased (P = 0.05) with increasing PB supplementation. These results indicate that feeding PB selectively altered bacteria and methanogenic archaeal populations in the GI tract of goats.

  8. How does the spacer length of cationic gemini lipids influence the lipoplex formation with plasmid DNA? Physicochemical and biochemical characterizations and their relevance in gene therapy.

    Science.gov (United States)

    Muñoz-Úbeda, Mónica; Misra, Santosh K; Barrán-Berdón, Ana L; Datta, Sougata; Aicart-Ramos, Clara; Castro-Hartmann, Pablo; Kondaiah, Paturu; Junquera, Elena; Bhattacharya, Santanu; Aicart, Emilio

    2012-12-10

    Lipoplexes formed by the pEGFP-C3 plasmid DNA (pDNA) and lipid mixtures containing cationic gemini surfactant of the 1,2-bis(hexadecyl dimethyl ammonium) alkanes family referred to as C16CnC16, where n=2, 3, 5, or 12, and the zwitterionic helper lipid, 1,2-dioleoyl-sn-glycero-3-phosphatidylethanolamine (DOPE) have been studied from a wide variety of physical, chemical, and biological standpoints. The study has been carried out using several experimental methods, such as zeta potential, gel electrophoresis, small-angle X-ray scattering (SAXS), cryo-TEM, gene transfection, cell viability/cytotoxicity, and confocal fluorescence microscopy. As reported recently in a communication (J. Am. Chem. Soc. 2011, 133, 18014), the detailed physicochemical and biological studies confirm that, in the presence of the studied series lipid mixtures, plasmid DNA is compacted with a large number of its associated Na+ counterions. This in turn yields a much lower effective negative charge, qpDNA−, a value that has been experimentally obtained for each mixed lipid mixture. Consequently, the cationic lipid (CL) complexes prepared with pDNA and CL/DOPE mixtures to be used in gene transfection require significantly less amount of CL than the one estimated assuming a value of qDNA−=−2. This drives to a considerably lower cytotoxicity of the gene vector. Depending on the CL molar composition, α, of the lipid mixture, and the effective charge ratio of the lipoplex, ρeff, the reported SAXS data indicate the presence of two or three structures in the same lipoplex, one in the DOPE-rich region, other in the CL-rich region, and another one present at any CL composition. Cryo-TEMand SAXS studies with C16CnC16/DOPE-pDNA lipoplexes indicate that pDNA is localized between the mixed lipid bilayers of lamellar structures within a monolayer of ∼2 nm. This is consistent with a highly compacted supercoiled pDNA conformation compared with that of linear DNA. Transfection studies were carried out

  9. Non-enolisable Knoevenagel condensate appended Schiff bases-metal (II) complexes: Spectral characteristics, DNA-binding and nuclease activities

    Science.gov (United States)

    Gubendran, Ammavasi; Kesavan, Mookkandi Palsamy; Ayyanaar, Srinivasan; Mitu, Liviu; Athappan, Periyakaruppan; Rajesh, Jegathalaprathaban

    2017-06-01

    New Schiff base complexes [Cu(L1)Cl] (1), [Ni(L1)Cl] (2), [Zn(L1)Cl] (3), and [Fe(L2)H2OCl] (4) {L1 = (4E)-3-(2-hydroxybenzylidene)-4-(2-hydroxyphenylimino)pentan-2-one, L2 = 2,2‧-(1E,1‧E)-(3-(2-hydroxybenzylidene)-pentane-2,4-diylidene)bis(azan-1-yl-1 idene)diphenol} have been synthesized and characterized by elemental analysis, UV-Vis, IR, FAB-mass, EPR, spectral studies and electrochemical studies, the ligands L1 &L2 were characterized by 1H and 13C NMR spectra. Complex 1 show a visible spectral d-d band near 600 nm and display cyclic voltammetric quasireversible response for the Cu(II)/Cu(I) couple vs Ag/AgCl in DMSO. The EPR spectrum of 1 show g‖ > g⊥ suggesting a square planar geometry around copper with dx2 - y2 as the ground state. The mass spectral results have confirmed the proposed structure for complexes 1-4. DNA binding properties of these complexes 1-4 have been investigated by absorption titrations, cyclic voltammetric studies and circular dichroism studies. On titration with DNA, the complexes 1-4 show hypochromism at the MLCT band (13-31%) with a red shift of 1-8 nm in the electronic spectrum and positive shift of voltammetric E1/2 in the CV studies are in favour of intercalative binding. CD spectra of 1 showed an increase in molar ellipticity (θ278) of the positive band with a minor red shift indicating the transition of B-form of DNA to A like form. DNA cleavage studies of complexes 1 and 4 with pUC18 DNA were studied by gel electrophoresis and complex 4 cleaves supercoiled pUC18 DNA in an oxidative manner in the presence of H2O2 and on photo irradiation at 312 nm.

  10. Electrostatic contribution to DNA condensation - application of 'energy minimization' in a simple model in strong Coulomb coupling regime

    CERN Document Server

    Mukherjee, Arup K

    2011-01-01

    Bending of DNA from a straight rod to a circular form in presence of any of the mono-, di-, tri- or tetravalent counterions has been simulated in strong Coulomb coupling environment employing a previously developed energy minimization simulation technique. The inherent characteristics of the simulation technique allow monitoring the required electrostatic contribution to the bending. The curvature of the bending has been found to play crucial roles in facilitating electrostatic attractive potential energy. The total electrostatic potential energy has been found to decrease with bending which indicates that bending a straight DNA to a circular form or to a toroidal form in presence of neutralizing counterions is energetically favorable and practically is a spontaneous phenomenon.

  11. TACN-based cationic lipids with amino acid backbone and double tails: materials for non-viral gene delivery.

    Science.gov (United States)

    Wang, Bing; Yi, Wen-Jing; Zhang, Ji; Zhang, Qin-Fang; Xun, Miao-Miao; Yu, Xiao-Qi

    2014-04-01

    Cationic lipids have become an efficient type of non-viral vectors for gene delivery. In this Letter, four cationic lipids containing 1,4,7-triazacyclononane (TACN) headgroup, glutamic/aspartic acid backbone and dioleyl tails were designed and synthesized. The TACN headgroup gives these lipids excellent pH buffering capacities, which were higher than branched 25 kDa PEI. Cationic liposomes prepared from these lipids and DOPE showed good DNA affinity, and full DNA condensation was found at N/P ratio of 3 via agarose gel electrophoresis. The lipoplexes were characterized by dynamic light scattering (DLS) assay, which gave proper particle sizes and zeta-potentials for transfection. In vitro gene transfection results in two cell lines reveal that TAN (with aspartic acid and amide bond in the structure) shows the best transfection efficiency, which is close to commercially available transfection agent Lipofectamine 2000.

  12. DNA conformational behavior and compaction in biomimetic systems: Toward better understanding of DNA packaging in cell.

    Science.gov (United States)

    Zinchenko, Anatoly

    2016-06-01

    In a living cell, long genomic DNA is strongly compacted and exists in the environment characterized by a dense macromolecular crowding, high concentrations of mono- and divalent cations, and confinement of ca. 10μm size surrounded by a phospholipid membrane. Experimental modelling of such complex biological system is challenging but important to understand spatiotemporal dynamics and functions of the DNA in cell. The accumulated knowledge about DNA condensation/compaction in conditions resembling those in the real cell can be eventually used to design and construct partly functional "artificial cells" having potential applications in drug delivery systems, gene therapy, and production of synthetic cells. In this review, I would like to overview the past progress in our understanding of the DNA conformational behavior and, in particular, DNA condensation/compaction phenomenon and its relation to the DNA biological activity. This understanding was gained by designing relevant experimental models mimicking DNA behavior in the environment of living cell. Starting with a brief summary of classic experimental systems to study DNA condensation/compaction, in later parts, I highlight recent experimental methodologies to address the effects of macromolecular crowding and nanoscale and microscale confinements on DNA conformation dynamics. All the studies are discussed in the light of their relevance to DNA behavior in living cells, and future prospects of the field are outlined.

  13. The Free Tricoordinated Silyl Cation Problem

    Directory of Open Access Journals (Sweden)

    Čičak, H.

    2010-03-01

    Full Text Available As the importance and abundance of silicon in our environment is large, it has been thought that silicon might take the place of carbon in forming a host of similar compounds and silicon-based life. However, until today there is no experimental evidence for such a hypothesis and carbon is still unique among the elements in the vast number and variety of compounds it can form. Also, the corresponding derivatives of the two elements show considerable differences in their chemical properties.The essential debate concerning organosilicon chemistry relates to the existence of the free planar tricoordinated silyl cations in condensed phase (R3Si+, in analogy to carbocations (R3C+ which have been known and characterized as free species. Although silyl cations are thermodynamically more stable than their carbon analogs, they are very reactive due to their high inherent electrophilicity and the ability of hypervalent coordination. On the other hand, stabilization by inductive and hyperconjugative effects and larger steric effects of carbocations make them less sensitive to solvation or other environmental effects than silyl cations. Hence, observation of free silyl cations in the condensed phase proved extremely difficult and the actual problem is the question of the degree of the (remaining silyl cation character.The first free silyl cation, trimesitylsilyl cation, and in analogy with it tridurylsilyl cation, were synthesized by Lambert et al. Free silyl cations based on analogy to aromatic ions (homocyclopropenylium and tropylium have also been prepared. However, in these silyl cations the cationic character is reduced by internal π -conjugation. Čičak et al. prepared some silyl-cationic intermediates (Me3Si--CH≡CR+in solid state. With the help of quantum-mechanical calculations it was concluded that these adducts have much more silyl cation than carbocation character.

  14. Cationic lipid/DNA complexes (JVRS-100) combined with influenza vaccine (Fluzone) increases antibody response, cellular immunity, and antigenically drifted protection.

    Science.gov (United States)

    Lay, Marla; Callejo, Bernadette; Chang, Stella; Hong, David K; Lewis, David B; Carroll, Timothy D; Matzinger, Shannon; Fritts, Linda; Miller, Christopher J; Warner, John F; Liang, Lily; Fairman, Jeffery

    2009-06-12

    Safe and effective adjuvants for influenza vaccines that could increase both the levels of neutralizing antibody, including against drifted viral subtypes, and T-cell immunity would be a major advance in vaccine design. The JVRS-100 adjuvant, consisting of DOTIM/cholesterol cationic liposome-DNA complexes, is particularly promising for vaccines that require induction of high levels of antibody and T-cell immunity, including CD8(+) cytotoxic T lymphocytes (CTL). Inclusion of protein antigens with JVRS-100 results in the induction of enhanced humoral and cell-mediated (i.e., CD4(+) and CD8(+) T cells) immune responses. The JVRS-100 adjuvant combined with a split trivalent influenza vaccine (Fluzone-sanofi pasteur) elicited increased antibody and T-cell responses in mice and non-human primates compared to vaccination with Fluzone alone. Mice vaccinated with JVRS-100-Fluzone and challenged with antigenically drifted strains of H1N1 (PR/8/34) and influenza B (B/Lee/40) viruses had higher grade protection, as measured by attenuation of weight loss and increased survival, compared to recipients of unadjuvanted vaccine. The results indicate that the JVRS-100 adjuvant substantially increases immunogenicity and protection from drifted-strain challenge using an existing influenza vaccine.

  15. Electrostatic theory of the assembly of PAMAM dendrimers and DNA.

    Science.gov (United States)

    Perico, Angelo

    2016-05-01

    The electrostatic interactions mediated by counterions between a cationic PAMAM dendrimer, modelized as a sphere of radius and cationic surface charge highly increasing with generation, and a DNA, modelized as an anionic elastic line, are analytically calculated in the framework of condensation theory. Under these interactions the DNA is wrapped around the sphere. For excess phosphates relative to dendrimer primary amines, the free energy of the DNA-dendrimer complex displays an absolute minimum when the complex is weakly negatively overcharged. This overcharging opposes gene delivery. For a highly positive dendrimer and a DNA fixed by experimental conditions to a number of phosphates less than the number of dendrimer primary amines, excess amine charges, the dendrimer may at the same time bind stably DNA and interact with negative cell membranes to activate cell transfection in fair agreement with molecular simulations and experiments.

  16. Stabilization flyuorytopodibnoyi structure in oxide vacuum condensate

    Directory of Open Access Journals (Sweden)

    О.М. Заславський

    2006-01-01

    Full Text Available  The influence of the oxide-stabilizer content, M'-cation radius and film deposition temperature on the stabilization of the fluorite-like solid solutions in the zirconium and hafnium oxides-based vacuum condensates, obtained by Laser-evaporating method, was investigated. The optimum parameters of the coatication of the isotropic thermostable coverings was determined. This results were explained by using of the high-speed condensation in vacuum theory.

  17. Condensation Polymerization

    Indian Academy of Sciences (India)

    S Ramakrishnan

    2017-04-01

    The very idea that large polymer molecules can indeed existwas hotly debated during the early part of the 20th century.As highlighted by Sivaram in his articles on Carothersand Flory, Staudinger’s macromolecular hypothesis was finallyaccepted, and the study of polymers gained momentumbecause of the remarkable efforts of the these two individualswho laid down the foundations concerning the processes thatled to the formation of large polymer molecules, and to thosethat led to an understanding of many of their extraordinaryphysical properties. Condensation polymerizations, as thename suggests, utilizes bond-forming reactions that generatea small molecule condensate, which often needs to be continuouslyremoved to facilitate the formation of the polymer. Inthis article, I shall describe some of the essential principles ofcondensation polymerizations or more appropriately calledstep-growth polymerizations; and I will also describe someinteresting extensions that lead to the formation of polymernetworks and highly branched polymers.

  18. MD and NMR analyses of choline and TMA binding to duplex DNA: on the origins of aberrant sequence-dependent stability by alkyl cations in aqueous and water-free solvents.

    Science.gov (United States)

    Portella, Guillem; Germann, Markus W; Hud, Nicholas V; Orozco, Modesto

    2014-02-26

    It has been known for decades that alkylammonium ions, such as tetramethyl ammonium (TMA), alter the usual correlation between DNA GC-content and duplex stability. In some cases it is even possible for an AT-rich duplex to be more stable than a GC-rich duplex of the same length. There has been much speculation regarding the origin of this aberration in sequence-dependent DNA duplex stability, but no clear resolution. Using a combination of molecular dynamics simulations and NMR spectroscopy we demonstrate that choline (2-hydroxy-N,N,N-trimethylethanaminium) and TMA are preferentially localized in the minor groove of DNA duplexes at A·T base pairs and these same ions show less pronounced localization in the major groove compared to what has been demonstrated for alkali and alkali earth metal ions. Furthermore, free energy calculations show that single-stranded GC-rich sequences exhibit more favorable solvation by choline than single-stranded AT-rich sequences. The sequence-specific nature of choline and TMA binding provides a rationale for the enhanced stability of AT-rich sequences when alkyl-ammonium ions are used as the counterions of DNA. Our combined theoretical and experimental study provides one of the most detailed pictures to date of cations localized along DNA in the solution state, and provides insights that go beyond understanding alkyl-ammonium ion binding to DNA. In particular, because choline and TMA bind to DNA in a manner that is found to be distinct from that previously reported for Na(+), K(+), Mg(2+), and Ca(2+), our results reveal the important but underappreciated role that most other cations play in sequence-specific duplex stability.

  19. In vitro studies of the genotoxic effects of bitumen and coal-tar fume condensates: comparison of data obtained by mutagenicity testing and DNA adduct analysis by 32P-postlabelling.

    Science.gov (United States)

    De Méo, M; Genevois, C; Brandt, H; Laget, M; Bartsch, H; Castegnaro, M

    1996-08-14

    Bitumens contain traces of polycyclic aromatic compounds (PACs), a part of which will end up in the fumes emitted during hot handling of bitumen-containing products, e.g. during roadpaving. Although exposure of workers to these fumes is low, it might lead to health problems. Studies on bitumen fume condensates (BFCs) showed weak to moderate mutagenic activities, but studies on DNA adduct formation have not been reported. Therefore, a study was initiated in which fumes were generated from two road grade bitumens, in such a way that they were representative of the fumes produced in the field. The combined vapour/particulates were tested in vitro for their ability to produce DNA adducts and in modified Ames mutation assays, using a number of different strains. An attempt was made to relate the results to chemical data, such as the content of a number of individual polycyclic aromatic hydrocarbons (PAHs) and with a measure for the total PAC content. As a reference material fume condensate from coal-tar (coal-tar pitch volatiles; CTPV) were subjected to the same tests. All fume condensates tested were mutagenic to all strains and induced the formation of DNA adducts. The patterns of DNA adducts, obtained by 32P-postlabelling, arising from the BFCs were qualitatively different from the patterns of adducts obtained from the CTPVs, implying qualitative differences in the nature of the compounds responsible for the formation of these adducts. This is corroborated by the observation that for BFCs quantitative adduct levels are higher than would be expected based on the PAH content. These data thus indicate that the PAHs analysed are not the sole components responsible for adduct formation from BFCs, but that an important contribution comes from other (hetero- and/or substituted-) PACs.

  20. Does Cation Size Affect Occupancy and Electrostatic Screening of the Nucleic Acid Ion Atmosphere?

    Science.gov (United States)

    Gebala, Magdalena; Bonilla, Steve; Bisaria, Namita; Herschlag, Daniel

    2016-08-31

    Electrostatics are central to all aspects of nucleic acid behavior, including their folding, condensation, and binding to other molecules, and the energetics of these processes are profoundly influenced by the ion atmosphere that surrounds nucleic acids. Given the highly complex and dynamic nature of the ion atmosphere, understanding its properties and effects will require synergy between computational modeling and experiment. Prior computational models and experiments suggest that cation occupancy in the ion atmosphere depends on the size of the cation. However, the computational models have not been independently tested, and the experimentally observed effects were small. Here, we evaluate a computational model of ion size effects by experimentally testing a blind prediction made from that model, and we present additional experimental results that extend our understanding of the ion atmosphere. Giambasu et al. developed and implemented a three-dimensional reference interaction site (3D-RISM) model for monovalent cations surrounding DNA and RNA helices, and this model predicts that Na(+) would outcompete Cs(+) by 1.8-2.1-fold; i.e., with Cs(+) in 2-fold excess of Na(+) the ion atmosphere would contain an equal number of each cation (Nucleic Acids Res. 2015, 43, 8405). However, our ion counting experiments indicate that there is no significant preference for Na(+) over Cs(+). There is an ∼25% preferential occupancy of Li(+) over larger cations in the ion atmosphere but, counter to general expectations from existing models, no size dependence for the other alkali metal ions. Further, we followed the folding of the P4-P6 RNA and showed that differences in folding with different alkali metal ions observed at high concentration arise from cation-anion interactions and not cation size effects. Overall, our results provide a critical test of a computational prediction, fundamental information about ion atmosphere properties, and parameters that will aid in the

  1. Condensation heat transfer

    Science.gov (United States)

    Rose, J. W.

    The paper gives a brief description of some of the better understood aspects of condensation heat transfer and includes discussion of the liquid-vapour interface, natural and forced convection laminar film condensation and dropwise condensation.

  2. Resin regeneration device for condensate desalter

    Energy Technology Data Exchange (ETDEWEB)

    Segawa, Yoshihiro [Toshiba Engineering Co. Ltd., Kawasaki, Kanagawa (Japan); Hirose, Yuki

    1998-07-28

    The present invention provides a resin regeneration device for a condensate desalter of a nuclear power plant. Namely, both anionic and cationic exchange resins are supplied in a mixed state from a forwarding water desalting tower to an anionic resin regeneration tower. In the anionic resin generation tower, the resin is once separated to an anionic exchange region layer, a mixed resin layer and an cationic exchange resin layer in this order from the upper portion by water injected from a stirring water injection tube disposed at the bottom. Then, water is injected from a developing water injection tube disposed at the lower portion of the mixed resin layer to develop the cationic exchange resin layer and the mixed resin layer to the upper portion of the cationic resin regeneration tower. Subsequently, the amount of the injection of the developing water is reduced to such a flow rate that only the anionic exchange resin is precipitated. Then, a cationic exchange resin layer is formed at the upper portion and an anion exchange resin layer is formed at the lower portion of the developing water injection tube of the cationic resin regeneration tower. The anionic exchange resin is transferred to the anionic exchange resin regeneration tower in this state. According to the present invention, the mixed resin layer can be separated to anionic and cationic exchange resins easily and reliably. (I.S.)

  3. Nature as a source of inspiration for cationic lipid synthesis.

    Science.gov (United States)

    Labas, Romain; Beilvert, Fanny; Barteau, Benoit; David, Stéphanie; Chèvre, Raphaël; Pitard, Bruno

    2010-02-01

    Synthetic gene delivery systems represent an attractive alternative to viral vectors for DNA transfection. Cationic lipids are one of the most widely used non-viral vectors for the delivery of DNA into cultured cells and are easily synthesized, leading to a large variety of well-characterized molecules. This review discusses strategies for the design of efficient cationic lipids that overcome the critical barriers of in vitro transfection. A particular focus is placed on natural hydrophilic headgroups and lipophilic tails that have been used to synthesize biocompatible and non-toxic cationic lipids. We also present chemical features that have been investigated to enhance the transfection efficiency of cationic lipids by promoting the escape of lipoplexes from the endosomal compartment and DNA release from DNA-liposome complexes. Transfection efficiency studies using these strategies are likely to improve the understanding of the mechanism of cationic lipid-mediated gene delivery and to help the rational design of novel cationic lipids.

  4. Effect of lipid composition on the structure and theoretical phase diagrams of DC-Chol/DOPE-DNA lipoplexes.

    Science.gov (United States)

    Muñoz-Ubeda, Mónica; Rodríguez-Pulido, Alberto; Nogales, Aurora; Martín-Molina, Alberto; Aicart, Emilio; Junquera, Elena

    2010-12-13

    Lipoplexes constituted by calf-thymus DNA (CT-DNA) and mixed cationic liposomes consisting of varying proportions of the cationic lipid 3β-[N-(N',N'-dimethylaminoethane)-carbamoyl]cholesterol hydrochloride (DC-Chol) and the zwitterionic lipid, 1,2-dioleoyl-sn-glycero-3-phosphoetanolamine (DOPE) have been analyzed by means of electrophoretic mobility, SAXS, and fluorescence anisotropy experiments, as well as by theoretically calculated phase diagrams. Both experimental and theoretical studies have been run at several liposome and lipoplex compositions, defined in terms of cationic lipid molar fraction, α, and either the mass or charge ratios of the lipoplex, respectively. The experimental electrochemical results indicate that DC-Chol/DOPE liposomes, with a mean hydrodynamic diameter of around (120 ± 10) nm, compact and condense DNA fragments at their cationic surfaces by means of a strong entropically driven electrostatic interaction. Furthermore, the positive charges of cationic liposomes are compensated by the negative charges of DNA phosphate groups at the isoneutrality L/D ratio, (L/D)(ϕ), which decreases with the cationic lipid content of the mixed liposome, for a given DNA concentration. This inversion of sign process has been also studied by means of the phase diagrams calculated with the theoretical model, which confirms all the experimental results. SAXS diffractograms, run at several lipoplex compositions, reveal that, irrespectively of the lipoplex charge ratio, DC-Chol/DOPE-DNA lipoplexes show a lamellar structure, L(α), when the cationic lipid content on the mixed liposomes α ≥ 0.4, while for a lower content (α = 0.2) the lipoplexes show an inverted hexagonal structure, H(II), usually related with improved cell transfection efficiency. A similar conclusion is reached from fluorescence anisotropy results, which indicate that the fluidity on liposome and lipoplexes membrane, also related with better transfection results, increases as long as the

  5. Polyamine-DNA interactions and development of gene delivery vehicles.

    Science.gov (United States)

    Thomas, T J; Tajmir-Riahi, H A; Thomas, Thresia

    2016-10-01

    Polyamines are positively charged organic cations under physiologic ionic and pH conditions and hence they interact with negatively charged macromolecules such as DNA and RNA. Although electrostatic interaction is the predominant mode of polyamine-nucleic acid interactions, site- and structure-specific binding has also been recognized. A major consequence of polyamine-DNA interaction is the collapse of DNA to nanoparticles of approximately 100 nm diameter. Electron and atomic force microscopic studies have shown that these nanoparticles are spheroids, toroids and rods. DNA transport to cells for gene therapy applications requires the condensation of DNA to nanoparticles and hence the study of polyamines and related compounds with nucleic acids has received technological importance. In addition to natural and synthetic polyamines, several amine-terminated or polyamine-substituted agents are under intense investigation for non-viral gene delivery vehicles.

  6. pH and reduction dual-responsive dipeptide cationic lipids with α-tocopherol hydrophobic tail for efficient gene delivery.

    Science.gov (United States)

    Liu, Qiang; Su, Rong-Chuan; Yi, Wen-Jing; Zheng, Li-Ting; Lu, Shan-Shan; Zhao, Zhi-Gang

    2017-03-31

    A series of tocopherol-based cationic lipid 3a-3f bearing a pH-sensitive imidazole moiety in the dipeptide headgroup and a reduction-responsive disulfide linkage were designed and synthesized. Acid-base titration of these lipids showed good buffering capacities. The liposomes formed from 3 and co-lipid 1, 2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) could efficiently bind and condense DNA into nanoparticles. Gel binding and HPLC assays confirmed the encapsulated DNA could release from lipoplexes 3 upon addition of 10 mM glutathione (GSH). MTT assays in HEK 293 cells demonstrated that lipoplexes 3 had low cytotoxicity. The in vitro gene transfection studies showed cationic dipeptide headgroups clearly affected the transfection efficiency (TE), and arginine-histidine based dipeptide lipid 3f give the best TE, which was 30.4 times higher than Lipofectamine 3000 in the presence of 10% serum. Cell-uptake assays indicated that basic amino acid containing dipeptide cationic lipids exhibited more efficient cell uptake than serine and aromatic amino acids based dipeptide lipids. Confocal laser scanning microscopy (CLSM) studies corroborated that 3 could efficiently deliver and release DNA into the nuclei of HeLa cells. These results suggest that tocopherol-based dipeptide cationic lipids with pH and reduction dual-sensitive characteristics might be promising non-viral gene delivery vectors.

  7. Discovery of metabolically stabilized electronegative polyacridine-PEG peptide DNA open polyplexes.

    Science.gov (United States)

    Fernandez, Christian A; Baumhover, Nicholas J; Anderson, Kevin; Rice, Kevin G

    2010-04-21

    Cationic condensing peptides and polymers bind electrostatically to DNA to form cationic polyplexes. While many cationic polyplexes are able to achieve in vitro transfection mediated through electrostatic interactions, few have been able to mediate gene transfer in vivo. The present study describes the development and testing of polyacridine PEG-peptides that bind to plasmid DNA by intercalation resulting in electronegative open polyplex DNA. Polyacridine PEG-peptides were prepared by chemically conjugating 6-(9-acridinylamino) hexanoic acid onto side chains of Lys in PEG-Cys-Trp-(Lys)(3, 4, or 5). The resulting PEG-Cys-Trp-(Lys-(Acr))(3, 4, or 5) peptides bound tightly to DNA by polyintercalation, rather than electrostatic binding. Unlike polycationic polyplexes, polyacridine PEG-peptide polyplexes were anionic and open coiled, as revealed by zeta potential and atomic force microscopy. PEG-Cys-Trp-(Lys-(Acr))(5) showed the highest DNA binding affinity and the greatest ability to protect DNA from metabolism by DNase. Polyacridine PEG-peptide DNA open polyplexes were dosed intramuscularly and electroporated in mice to demonstrate their functional activity in gene transfer. These results establish polyacridine PEG-peptide DNA open polyplexes as a novel gene delivery method for in vivo use.

  8. Incorporation of an aggregation-induced-emissive tetraphenylethene derivative into cationic gene delivery vehicles manifested the nuclear translocation of uncomplexed DNA.

    Science.gov (United States)

    Han, Xiongqi; Chen, Qixian; Lu, Hongguang; Guo, Pan; Li, Wei; Wu, Guolin; Ma, Jianbiao; Gao, Hui

    2016-03-11

    A fluorophore displaying aggregation-induced emission was introduced at the terminus of branched polyethylenimine (PEI). The formulated polyplex not only demonstrated an improved safety profile and preserved transfection activity but also importantly indicated that the uncomplexed naked DNA rather than the polyplexes translocated into the nucleus.

  9. Condensation in insulated homes

    Energy Technology Data Exchange (ETDEWEB)

    Wiley, R A

    1978-05-28

    A research proposal on condensation in insulated homes is presented. Information is provided on: justification for condensation control; previous work and present outlook (good vapor barrier, condensation and retrofit insulation, vapor barrier decreases condensation, brick-veneer walls, condensation in stress-skin panels, air-conditioned buildings, retrofitting for conservation, study on mobile homes, high indoor relative humidity, report on various homes); and procedure (after funding has been secured). Measures are briefly described on opening walls, testing measures, and retrofitting procedures. An extensive bibliography and additional informative citations are included. (MCW)

  10. Interaction of DNA with Cationic Gemini Surfactant Trimethylene-1, 3-bis (dodecyldimethyl-ammonium bromide) and Anionic surfactant SDS mixed system%DNA与阳离子gemini表面活性剂和阴离子表面活性剂SDS混合系统的相互作用

    Institute of Scientific and Technical Information of China (English)

    赵小芳; 尚亚卓; 刘洪来; 胡英; 姜建文

    2008-01-01

    The interaction of DNA with cationic gemini surfactant trimethylene-1,3-bis (dodecyl dimethyl-ammonium bromide) (12-3-12) and anionic surfactant sodium dodecyl sulfate (SDS) mixed system has been investigated by measuring the fluorescence, zeta potential, UV-Vis spectrum, and circular dichroism. In the absence of SDS, owing to the electrostatic and hydrophobic interactions, 12-3-12 forms micelle-like structure on the DNA chain before the micellization in bulk phase. For the mixed system of 12-3-12 and SDS, the negative charges on SDS can compete against DNA to bind with cationic 12-3-12 because of the stronger interaction between oppositely charged surfactants, and thus, the catanionic mixed micelles are formed before the formation of DNA/12-3-12 complexes. Thereafter, the positive charges on the mixed micelles bind with DNA, and thus, the change of the zeta potential from negative to positive is distinctly different from the system without SDS. Meanwhile, the existence of SDS postpones the exclusion of ethidium bromide (EB) from DNA/EB complexes. The conformation of DNA undergoes a change from native B-form to chiral Ψ-phase as binding with 12-3-12 process. Upon adding SDS to the DNA/12-3-12 complex solution, however, DNA is released to the bulk and the Ψ-phase returns to B-form again.

  11. Electrostatic contribution to DNA condensation-application of 'energy minimization' in a simple model in the strong Coulomb coupling regime

    Energy Technology Data Exchange (ETDEWEB)

    Mukherjee, Arup K, E-mail: akmukherjee11@hotmail.com [Department of Physics, Chancellor College, University of Malawi, Box 280, Zomba (Malawi)

    2011-08-17

    The process of bending of straight DNA to a circular form in the presence of any of the mono-, di-, tri- or tetravalent counterions has been simulated in a strong Coulomb coupling environment, employing a previously developed energy minimization simulation technique. The inherent characteristics of the simulation technique allow the monitoring of the required electrostatic contribution to the bending. The curvature of the bending has been found to play a crucial role in facilitating the electrostatic attractive potential energy. The total electrostatic potential energy has been found to decrease with bending, which indicates that bending straight DNA to a circular form or to a toroidal form in the presence of neutralizing counterions is energetically favourable and is practically a spontaneous phenomenon.

  12. Cationic lipid-formulated DNA vaccine against hepatitis B virus: immunogenicity of MIDGE-Th1 vectors encoding small and large surface antigen in comparison to a licensed protein vaccine.

    Directory of Open Access Journals (Sweden)

    Anne Endmann

    Full Text Available Currently marketed vaccines against hepatitis B virus (HBV based on the small (S hepatitis B surface antigen (HBsAg fail to induce a protective immune response in about 10% of vaccinees. DNA vaccination and the inclusion of PreS1 and PreS2 domains of HBsAg have been reported to represent feasible strategies to improve the efficacy of HBV vaccines. Here, we evaluated the immunogenicity of SAINT-18-formulated MIDGE-Th1 vectors encoding the S or the large (L protein of HBsAg in mice and pigs. In both animal models, vectors encoding the secretion-competent S protein induced stronger humoral responses than vectors encoding the L protein, which was shown to be retained mainly intracellularly despite the presence of a heterologous secretion signal. In pigs, SAINT-18-formulated MIDGE-Th1 vectors encoding the S protein elicited an immune response of the same magnitude as the licensed protein vaccine Engerix-B, with S protein-specific antibody levels significantly higher than those considered protective in humans, and lasting for at least six months after the third immunization. Thus, our results provide not only the proof of concept for the SAINT-18-formulated MIDGE-Th1 vector approach but also confirm that with a cationic-lipid formulation, a DNA vaccine at a relatively low dose can elicit an immune response similar to a human dose of an aluminum hydroxide-adjuvanted protein vaccine in large animals.

  13. Rigid aromatic linking moiety in cationic lipids for enhanced gene transfection efficiency.

    Science.gov (United States)

    Wang, Bing; Zhao, Rui-Mo; Zhang, Ji; Liu, Yan-Hong; Huang, Zheng; Yu, Qing-Ying; Yu, Xiao-Qi

    2017-08-18

    Although numerous cationic lipids have been developed as non-viral gene vectors, the structure-activity relationship (SAR) of these materials remains unclear and needs further investigation. In this work, a series of lysine-derived cationic lipids containing linkages with different rigidity were designed and synthesized. SAR studies showed that lipids with rigid aromatic linkage could promote the formation of tight liposomes and enhance DNA condensation, which is essential for the gene delivery process. These lipids could give much higher transfection efficiency than those containing more flexible aliphatic linkage in various cell lines. Moreover, the rigid aromatic linkage also affords the material higher serum tolerance ability. Flow cytometry assay revealed that the target lipids have good cellular uptake, while confocal microscopy observation showed weaker endosome escape than Lipofectamine 2000. To solve such problem and further increase the transfection efficiency, some lysosomotropic reagents were used to improve the endosome escape of lipoplex. As expected, higher transfection efficiency than Lipofectamine 2000 could be obtained via this strategy. Cytotoxicity assay showed that these lipids have lower toxicity in various cell lines than Lipofectamine 2000, suggesting their potential for further application. This work demonstrates that a rigid aromatic linkage might distinctly improve the gene transfection abilities of cationic lipids and affords information to construct safe and efficient gene vector towards practical application. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  14. Density-fitted open-shell symmetry-adapted perturbation theory and application to π-stacking in benzene dimer cation and ionized DNA base pair steps

    Science.gov (United States)

    Gonthier, Jérôme F.; Sherrill, C. David

    2016-10-01

    Symmetry-Adapted Perturbation Theory (SAPT) is one of the most popular approaches to energy component analysis of non-covalent interactions between closed-shell systems, yielding both accurate interaction energies and meaningful interaction energy components. In recent years, the full open-shell equations for SAPT up to second-order in the intermolecular interaction and zeroth-order in the intramolecular correlation (SAPT0) were published [P. S. Zuchowski et al., J. Chem. Phys. 129, 084101 (2008); M. Hapka et al., ibid. 137, 164104 (2012)]. Here, we utilize density-fitted electron repulsion integrals to produce an efficient computational implementation. This approach is used to examine the effect of ionization on π-π interactions. For the benzene dimer radical cation, comparison against reference values indicates a good performance for open-shell SAPT0, except in cases with substantial charge transfer. For π stacking between hydrogen-bonded pairs of nucleobases, dispersion interactions still dominate binding, in spite of the creation of a positive charge.

  15. An efficient nonviral gene-delivery vector based on hyperbranched cationic glycogen derivatives

    Directory of Open Access Journals (Sweden)

    Liang X

    2014-01-01

    Full Text Available Xuan Liang,1,* Xianyue Ren,2,* Zhenzhen Liu,1 Yingliang Liu,1 Jue Wang,2 Jingnan Wang,2 Li-Ming Zhang,1 David YB Deng,2 Daping Quan,1 Liqun Yang1 1Institute of Polymer Science, School of Chemistry and Chemical Engineering, Key Laboratory of Designed Synthesis and Application of Polymer Material, Key Laboratory for Polymeric Composite and Functional Materials of Ministry of Education, Sun Yat-Sen University, Guangzhou, People's Republic of China; 2Research Center of Translational Medicine, The First Affiliated Hospital, Sun Yat-Sen University, Guangzhou, People's Republic of China *Both these authors contributed equally to this work Background: The purpose of this study was to synthesize and evaluate hyperbranched cationic glycogen derivatives as an efficient nonviral gene-delivery vector. Methods: A series of hyperbranched cationic glycogen derivatives conjugated with 3-(dimethylamino-1-propylamine (DMAPA-Glyp and 1-(2-aminoethyl piperazine (AEPZ-Glyp residues were synthesized and characterized by Fourier-transform infrared and hydrogen-1 nuclear magnetic resonance spectroscopy. Their buffer capacity was assessed by acid–base titration in aqueous NaCl solution. Plasmid deoxyribonucleic acid (pDNA condensation ability and protection against DNase I degradation of the glycogen derivatives were assessed using agarose gel electrophoresis. The zeta potentials and particle sizes of the glycogen derivative/pDNA complexes were measured, and the images of the complexes were observed using atomic force microscopy. Blood compatibility and cytotoxicity were evaluated by hemolysis assay and MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assay, respectively. pDNA transfection efficiency mediated by the cationic glycogen derivatives was evaluated by flow cytometry and fluorescence microscopy in the 293T (human embryonic kidney and the CNE2 (human nasopharyngeal carcinoma cell lines. In vivo delivery of pDNA in model animals (Sprague Dawley

  16. Cationic niosomes an effective gene carrier composed of novel spermine-derivative cationic lipids: effect of central core structures.

    Science.gov (United States)

    Opanasopit, Praneet; Leksantikul, Lalita; Niyomtham, Nattisa; Rojanarata, Theerasak; Ngawhirunpat, Tanasait; Yingyongnarongkul, Boon-Ek

    2017-05-01

    Cationic niosomes formulated from Span 20, cholesterol (Chol) and novel spermine-based cationic lipids of multiple central core structures (di(oxyethyl)amino, di(oxyethyl)amino carboxy, 3-amino-1,2-dioxypropyl and 2-amino-1,3-dioxypropyl) were successfully prepared for improving transfection efficiency in vitro. The niosomes composed of spermine cationic lipid with central core structure of di(oxyethyl)amino revealed the highest gene transfection efficiency. To investigate the factors affecting gene transfection and cell viability including differences in the central core structures of cationic lipids, the composition of vesicles, molar ratio of cationic lipids in formulations and the weight ratio of niosomes to DNA. Cationic niosomes composed of nonionic surfactants (Span20), cholesterol and spermine-based cationic lipids of multiple central core structures were formulated. Gene transfection and cell viability were evaluated on a human cervical carcinoma cell line (HeLa cells) using pDNA encoding green fluorescent protein (pEGFP-C2). The morphology, size and charge were also characterized. High transfection efficiency was obtained from cationic niosomes composed of Span20:Chol:cationic lipid at the molar ratio of 2.5:2.5:0.5 mM. Cationic lipids with di(oxyethyl)amino as a central core structure exhibited highest transfection efficiency. In addition, there was also no serum effect on transfection efficiency. These novel cationic niosomes may constitute a good alternative carrier for gene transfection.

  17. Paramagnetic decoration of DNA origami nanostructures by Eu³⁺ coordination.

    Science.gov (United States)

    Opherden, Lars; Oertel, Jana; Barkleit, Astrid; Fahmy, Karim; Keller, Adrian

    2014-07-15

    The folding of DNA into arbitrary two- and three-dimensional shapes, called DNA origami, represents a powerful tool for the synthesis of functional nanostructures. Here, we present the first approach toward the paramagnetic functionalization of DNA origami nanostructures by utilizing postassembly coordination with Eu(3+) ions. In contrast to the usual formation of toroidal dsDNA condensates in the presence of trivalent cations, planar as well as rod-like DNA origami maintain their shape and monomeric state even under high loading with the trivalent lanthanide. Europium coordination was demonstrated by the change in Eu(3+) luminescence upon binding to the two DNA origami. Their natural circular dichroism in the Mg(2+)- and Eu(3+)-bound state was found to be very similar to that of genomic DNA, evidencing little influence of the DNA origami superstructure on the local chirality of the stacked base pairs. In contrast, the magnetic circular dichroism of the Mg(2+)-bound DNA origami deviates from that of genomic DNA. Furthermore, the lanthanide affects the magnetic properties of DNA in a superstructure-dependent fashion, indicative of the existence of superstructure-specific geometry of Eu(3+) binding sites in the DNA origami that are not formed in genomic DNA. This simple approach lays the foundation for the generation of magneto-responsive DNA origami nanostructures. Such systems do not require covalent modifications and can be used for the magnetic manipulation of DNA nanostructures or for the paramagnetic alignment of molecules in NMR spectroscopy.

  18. Exploring the strength, mode, dynamics, and kinetics of binding interaction of a cationic biological photosensitizer with DNA: implication on dissociation of the drug-DNA complex via detergent sequestration.

    Science.gov (United States)

    Paul, Bijan Kumar; Guchhait, Nikhil

    2011-10-20

    The present study aims at exploring a detailed characterization of the binding interaction of a promising cancer cell photosensitizer, harmane (HM), with DNA extracted from herring sperm. The polarity-sensitive prototropic transformation of HM, a naturally occurring, fluorescent, drug-binding alkaloid, β-carboline, is remarkably modified upon interaction with DNA and is manifested through significant modulations on the absorption and emission profiles of HM. From the series of studies undertaken in the present program, for example, absorption; steady-state emission; the effect of chaotrope (urea); iodide ion-induced steady-state fluorescence quenching; circular dichroism (CD); and helix melting from absorption spectroscopy; the mode of binding of HM into the DNA helix has been substantiated to be principally intercalative. Concomitantly, a discernible dependence of the photophysics of the DNA-bound drug on the medium ionic strength indicates that electrostatic attraction should not be ignored in the interaction. Efforts have also been delivered to delineate the dynamical aspects of the interaction, such as modulation in time-resolved fluorescence decay and rotational relaxation dynamics of the drug within the DNA environment. In view of the prospective biological applications of HM, the issue of facile dissociation of intercalated HM from the DNA helix also comprises a crucial prerequisite for the functioning as an effective therapeutic agent. In this context, our results imply that the concept of detergent-sequestered dissociation of the drug from the drug-DNA complex can be a prospective strategy through an appropriate choice of the detergent molecule. The utility of the present work resides in exploring the potential applicability of the fluorescence property of HM for studying its interactions with a relevant biological target, for example, DNA. In addition, the methods and techniques used in the present work can also be exploited to study the interaction of

  19. Condensation Energy of a Spacetime Condensate

    CERN Document Server

    de Matos, Clovis Jacinto

    2010-01-01

    Starting from an analogy between the Planck-Einstein scale and the dual length scales in Ginzburg-Landau theory of superconductivity, and assuming that space-time is a condensate of neutral fermionic particles with Planck mass, we derive the baryonic mass of the universe. In that theoretical framework baryonic matter appears to be associated with the condensation energy gained by spacetime in the transition from its normal (symetric) to its (less symetric) superconducting-like phase. It is shown however that the critical transition temperature cannot be the Planck temperature. Thus leaving open the enigma of the microscopic description of spacetime at quantum level.

  20. Systematic text condensation

    DEFF Research Database (Denmark)

    Malterud, Kirsti

    2012-01-01

    To present background, principles, and procedures for a strategy for qualitative analysis called systematic text condensation and discuss this approach compared with related strategies.......To present background, principles, and procedures for a strategy for qualitative analysis called systematic text condensation and discuss this approach compared with related strategies....

  1. Measure Guideline: Evaporative Condensers

    Energy Technology Data Exchange (ETDEWEB)

    German, A [Alliance for Residential Building Innovation (ARBI), Davis, CA (United States); Dakin, B. [Alliance for Residential Building Innovation (ARBI), Davis, CA (United States); Hoeschele, M. [Alliance for Residential Building Innovation (ARBI), Davis, CA (United States)

    2012-03-01

    This measure guideline on evaporative condensers provides information on properly designing, installing, and maintaining evaporative condenser systems as well as understanding the benefits, costs, and tradeoffs. This is a prescriptive approach that outlines selection criteria, design and installation procedures, and operation and maintenance best practices.

  2. Parametrization of direct and soft steric-undulatory forces between DNA double helical polyelectrolytes in solutions of several different anions and cations.

    Science.gov (United States)

    Podgornik, R; Rau, D C; Parsegian, V A

    1994-04-01

    Directly measured forces between DNA helices in ordered arrays have been reduced to simple force coefficients and mathematical expressions for the interactions between pairs of molecules. The tabulated force parameters and mathematical expressions can be applied to parallel molecules or, by transformation, to skewed molecules of variable separation and mutual angle. This "toolbox" of intermolecular forces is intended for use in modelling molecular interactions, assembly, and conformation. The coefficients characterizing both the exponential hydration and the electrostatic interactions depend strongly on the univalent counterion species in solution, but are only weakly sensitive to anion type and temperature (from 5 to 50 degrees C). Interaction coefficients for the exponentially varying hydration force seen at spacings less than 10 to 15 A between surfaces are extracted directly from pressure versus interaxial distance curves. Electrostatic interactions are only observed at larger spacings and are always coupled with configurational fluctuation forces that result in observed exponential decay lengths that are twice the expected Debye-Huckel length. The extraction of electrostatic force parameters relies on a theoretical expression describing steric forces of molecules "colliding" through soft exponentially varying direct interactions.

  3. DNA

    Science.gov (United States)

    Stent, Gunther S.

    1970-01-01

    This history for molecular genetics and its explanation of DNA begins with an analysis of the Golden Jubilee essay papers, 1955. The paper ends stating that the higher nervous system is the one major frontier of biological inquiry which still offers some romance of research. (Author/VW)

  4. Supramolecular 1-D polymerization of DNA origami through a dynamic process at the 2-dimensionally confined air-water interface.

    Science.gov (United States)

    Yonamine, Yusuke; Cervantes-Salguero, Keitel; Minami, Kosuke; Kawamata, Ibuki; Nakanishi, Waka; Hill, Jonathan P; Murata, Satoshi; Ariga, Katsuhiko

    2016-05-14

    In this study, a Langmuir-Blodgett (LB) system has been utilized for the regulation of polymerization of a DNA origami structure at the air-water interface as a two-dimensionally confined medium, which enables dynamic condensation of DNA origami units through variation of the film area at the macroscopic level (ca. 10-100 cm(2)). DNA origami sheets were conjugated with a cationic lipid (dioctadecyldimethylammonium bromide, 2C18N(+)) by electrostatic interaction and the corresponding LB-film was prepared. By applying dynamic pressure variation through compression-expansion processes, the lipid-modified DNA origami sheets underwent anisotropic polymerization forming a one-dimensionally assembled belt-shaped structure of a high aspect ratio although the thickness of the polymerized DNA origami was maintained at the unimolecular level. This approach opens up a new field of mechanical induction of the self-assembly of DNA origami structures.

  5. Sedimentary condensation and authigenesis

    Science.gov (United States)

    Föllmi, Karl

    2016-04-01

    Most marine authigenic minerals form in sediments, which are subjected to condensation. Condensation processes lead to the formation of well individualized, extremely thin ( 100ky), and which experienced authigenesis and the precipitation of glaucony, verdine, phosphate, iron and manganese oxyhydroxides, iron sulfide, carbonate and/or silica. They usually show complex internal stratigraphies, which result from an interplay of sediment accumulation, halts in sedimentation, sediment winnowing, erosion, reworking and bypass. They may include amalgamated faunas of different origin and age. Hardgrounds may be part of condensed beds and may embody strongly condensed beds by themselves. Sedimentary condensation is the result of a hydrodynamically active depositional regime, in which sediment accumulation, winnowing, erosion, reworking and bypass are processes, which alternate as a function of changes in the location and intensity of currents, and/or as the result of episodic high-energy events engendered by storms and gravity flow. Sedimentary condensation has been and still is a widespread phenomenon in past and present-day oceans. The present-day distribution of glaucony and verdine-rich sediments on shelves and upper slopes, phosphate-rich sediments and phosphorite on outer shelves and upper slopes, ferromanganese crusts on slopes, seamounts and submarine plateaus, and ferromanganese nodules on abyssal seafloors is a good indication of the importance of condensation processes today. In the past, we may add the occurrence of oolitic ironstone, carbonate hardgrounds, and eventually also silica layers in banded iron formations as indicators of the importance of condensation processes. Besides their economic value, condensed sediments are useful both as a carrier of geochemical proxies of paleoceanographic and paleoenvironmental change, as well as the product of episodes of paleoceanographic and paleoenvironmental change themselves.

  6. Physics of condensed matter

    CERN Document Server

    Misra, Prasanta K

    2012-01-01

    Physics of Condensed Matter is designed for a two-semester graduate course on condensed matter physics for students in physics and materials science. While the book offers fundamental ideas and topic areas of condensed matter physics, it also includes many recent topics of interest on which graduate students may choose to do further research. The text can also be used as a one-semester course for advanced undergraduate majors in physics, materials science, solid state chemistry, and electrical engineering, because it offers a breadth of topics applicable to these majors. The book be

  7. Infrared spectrum of the chloromethylene hydroperoxide cation in solid argon

    Science.gov (United States)

    Chen, Mohua; Zhou, Mingfei

    2013-07-01

    Infrared spectrum of the chloromethylene hydroperoxide cation, HC(Cl)OOH+ in solid argon is reported. The cation is produced by co-condensation of dichloromethane and dioxygen mixtures with high-frequency discharged argon at 4 K followed by visible light excitation. On the basis of isotopic substitutions as well as quantum chemical frequency calculations, absorptions at 3452.7, 3052.0, 1499.6, 976.9, 855.4 and 956.1 cm-1 are assigned to the O-H, C-H, Cdbnd O, C-Cl and O-O stretching and out-of-plane CH wagging vibrations of the chloromethylene hydroperoxy cation. The cation was predicted to have a singlet ground state with planar Cs symmetry.

  8. Cationic dialkylarylphosphates: a new family of bio-inspired cationic lipids for gene delivery.

    Science.gov (United States)

    Le Corre, Stéphanie S; Belmadi, Nawal; Berchel, Mathieu; Le Gall, Tony; Haelters, Jean-Pierre; Lehn, Pierre; Montier, Tristan; Jaffrès, Paul-Alain

    2015-01-28

    In this work that aims to synthesize and evaluate new cationic lipids as vectors for gene delivery, we report the synthesis of a series of cationic lipids in which a phosphate functional group acts as a linker to assemble on a molecular scale, two lipid chains and one cationic polar head. The mono or dicationic moiety is connected to the phosphate group by an aryl spacer. In this work, two synthesis strategies were evaluated. The first used the Atherton-Todd coupling reaction to introduce a phenolic derivative to dioleylphosphite. The second strategy used a sequential addition of lipid alcohol and a phenolic derivative on POCl3. The two methods are efficient, but the latter allows larger yields. Different polar head groups were introduced, thus producing amphiphilic compounds possessing either one permanent (N-methyl-imidazolium, pyridinium, trimethylammonium) or two permanent cationic charges. All these cationic lipids were formulated as liposomal solutions and characterized (size and zeta potential). They formed stable liposomal solutions both in water (at pH 7.0) and in a weakly acidic medium (at pH 5.5). Finally, this new generation of cationic lipids was used to deliver DNA into various human-derived epithelial cells cultured in vitro. Compared with Lipofectamine used as a reference commercial lipofection reagent, some cationic dialkylarylphosphates were able to demonstrate potent gene transfer abilities, and noteworthily, monocationic derivatives were much more efficient than dicationic analogues.

  9. Measure Guideline: Evaporative Condensers

    Energy Technology Data Exchange (ETDEWEB)

    German, A.; Dakin, B.; Hoeschele, M.

    2012-03-01

    The purpose of this measure guideline on evaporative condensers is to provide information on a cost-effective solution for energy and demand savings in homes with cooling loads. This is a prescriptive approach that outlines selection criteria, design and installation procedures, and operation and maintenance best practices. This document has been prepared to provide a process for properly designing, installing, and maintaining evaporative condenser systems as well as understanding the benefits, costs, and tradeoffs.

  10. Efficient cell migration requires global chromatin condensation.

    Science.gov (United States)

    Gerlitz, Gabi; Bustin, Michael

    2010-07-01

    Cell migration is a fundamental process that is necessary for the development and survival of multicellular organisms. Here, we show that cell migration is contingent on global condensation of the chromatin fiber. Induction of directed cell migration by the scratch-wound assay leads to decreased DNaseI sensitivity, alterations in the chromatin binding of architectural proteins and elevated levels of H4K20me1, H3K27me3 and methylated DNA. All these global changes are indicative of increased chromatin condensation in response to induction of directed cell migration. Conversely, chromatin decondensation inhibited the rate of cell migration, in a transcription-independent manner. We suggest that global chromatin condensation facilitates nuclear movement and reshaping, which are important for cell migration. Our results support a role for the chromatin fiber that is distinct from its known functions in genetic processes.

  11. Cation-cation interaction in neptunyl(V) compounds

    Energy Technology Data Exchange (ETDEWEB)

    Krot, N.N. [Russian Academy of Sciences, Institute of Physical Chemistry (Russian Federation); Saeki, Masakatsu [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    2003-03-01

    The original manuscript was prepared by Professor N.N. Krot of Institute of Physical Chemistry, Russian Academy of Sciences, in 1997. Saeki tried to translate that into Japanese and to add some new data since 1997. The contents include the whole picture of cation-cation interactions mainly in 5-valence neptunium compounds. Firstly, characteristic structures of neptunium are summarized of the cation-cation bonding in compounds. Secondly, it is mentioned how the cation-cation bonding affects physical and chemical properties of the compounds. Then, characterization-methods for the cation-cation bonding in the compounds are discussed. Finally, the cation-cation interactions in compounds of other actinide-ions are shortly reviewed. (author)

  12. Sulfo cation-exchange resins as heterogeneous catalysts for the reaction of styrene with formaldehyde

    Energy Technology Data Exchange (ETDEWEB)

    Kasymova, K.A.; Sharf, V.Z.; Litvin, E.F.; Grigor' eva, E.N.

    1987-07-20

    Macroporous and gel sulfo cation-exchange resins are active catalysts for the condensation of styrene with formaldehyde. The product, 4-phenyl-1,3-dioxane was obtained in up to 97% yield. The activity of macroporous sulfo cation-exchange resins increases with decreasing particle diameter but in the case of the gel samples, granule size has only a slight effect on the reaction rate. The enhanced activity of sulfo cation-exchange resins is presumably a result of the high value of the acidity function H/sub 0/ of the sulfonic acid groups of the cation-exchange resin.

  13. Muonic Chemistry in Condensed Matter

    CERN Multimedia

    2002-01-01

    When polarized muons (@m|+) stop in condensed matter, muonic atoms are formed in the final part of their range, and direct measurements of the @m|+-spin polarization are possible via the asymmetric decay into positrons. The hyperfine interaction determines the characteristic precession frequencies of the @m|+ spin in muonium, @w(Mu). Such frequencies can be altered by the interactions of the muonium's electron spin with the surrounding medium. The measurement of @w(Mu) in a condensed system is known often to provide unique information regarding the system. \\\\ \\\\ In particular, the use of muonium atoms as a light isotope of the simple reactive radical H|0 allows the investigation of fast reactions of radicals over a typical time scale 10|-|9~@$<$~t~@$<$~10|-|5~sec, which is determined by the instrumental resolution at one end and by the @m|+ lifetime at the other. \\\\ \\\\ In biological macromolecules transient radicals, such as the constituents of DNA itself, exist on a time scale of sub-microseconds, acco...

  14. Synthesis of water-based cationic polyurethane for antibacterial and gene delivery applications.

    Science.gov (United States)

    Wu, Geng-Hsi; Hsu, Shan-Hui

    2016-10-01

    Cationic polymers are often used as antimicrobial materials and transfection reagents. Water-based process could reduce environmental pollution and prevent the risk of solvent residue in the final product. In this study, waterborne biodegradable cationic polyurethane (WCPU) was synthesized by reacting polycaprolactone (PCL diol), isophorone diisocyanate (IPDI), and N-methyldiethanolamine (N-MDEA) under 75°C. An aqueous dispersion of WCPU nanoparticles (NPs) could be acquired by vigorous stirring under acidic condition. The particles in the dispersion had an average size of ∼80nm and a zeta potential of ∼60mV. When cast into films, the contact angle of the film was ∼67° and the zeta potential was ∼16mV. WCPU NPs demonstrated excellent antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) (100% inhibition with a contact time of 3h). Meanwhile, the antibacterial ratio of WCPU films to E. coli and S. aureus reached 100% after 24h of contact. Moreover, WCPU NPs could be used as a transfection reagent without significant toxicity for concentrations less than 1000μg/mL and showed the ability to condensate plasmid DNA. The transfection efficiency for HEK293T cells and hBMSCs was ∼60% and ∼30% at 48h, respectively, after the transfection. Therefore, the WCPU synthesized in this study has potential antibacterial and gene delivery applications.

  15. Cationic amphiphiles as delivery system for genes into eukaryotic cells

    NARCIS (Netherlands)

    Oberle, Volker; Zuhorn, Inge S.; Audouy, Sandrine; Bakowsky, Udo; Smisterová, Jarmila; Engberts, Jan B.F.N.; Hoekstra, Dick; Gregoriadis, G; McCormack, B

    2000-01-01

    Cationic liposomes, consisting of synthetic amphiphiles and a so-called helper lipid, rapidly form complexes with DNA, known as lipoplexes. When incubated with cells in culture, the DNA can be delivered into the cell and becomes expressed. Because of these properties, lipoplexes are considered a use

  16. CONDENSATION OF WATER VAPOR IN A VERTICAL TUBE CONDENSER

    Directory of Open Access Journals (Sweden)

    Jan Havlík

    2015-10-01

    Full Text Available This paper presents an analysis of heat transfer in the process of condensation of water vapor in a vertical shell-and-tube condenser. We analyze the use of the Nusselt model for calculating the condensation heat transfer coefficient (HTC inside a vertical tube and the Kern, Bell-Delaware and Stream-flow analysis methods for calculating the shell-side HTC from tubes to cooling water. These methods are experimentally verified for a specific condenser of waste process vapor containing air. The operating conditions of the condenser may be different from the assumptions adopted in the basic Nusselt theory. Modifications to the Nusselt condensation model are theoretically analyzed.

  17. Regeneration method for condensate desalting device

    Energy Technology Data Exchange (ETDEWEB)

    Tsurumi, Takeshi; Kashimura, Makoto

    1998-09-02

    Regeneration of a condensate desalting device in a PWR type power plant is conducted by separating a mixed bed into an anion exchange resin layer and a cation exchange resin layer by back washing after stoppage of passage of water. Regeneration of an anion exchange resin layer is conducted by injecting alkali (hydrogen) carbonate such as sodium carbonate and potassium hydrogen carbonate, and extruding them with purified water and then injecting alkali hydroxide, extruding and further washing with purified water. Regeneration of a cation exchange resin layer is conducted by injecting acids such as hydrochloric acid and sulfuric acid followed by extrusion and washing. It is preferable that a liquid formed by mixing the regenerated liquid wastes of the anion exchange resin containing alkali (hydro) carbonate and regenerated liquid wastes of the cationic exchange resin containing acids and allowing generated carbon dioxide to be absorbed to alkali hydroxide is used as alkali (hydrogen) carbonate for the next regeneration. With such procedures, anion exchange resin which adsorbs decomposed products of amines can be regenerated efficiently. (I.N.)

  18. Condensed matter physics

    CERN Document Server

    Isihara, A

    2007-01-01

    More than a graduate text and advanced research guide on condensed matter physics, this volume is useful to plasma physicists and polymer chemists, and their students. It emphasizes applications of statistical mechanics to a variety of systems in condensed matter physics rather than theoretical derivations of the principles of statistical mechanics and techniques. Isihara addresses a dozen different subjects in separate chapters, each designed to be directly accessible and used independently of previous chapters. Topics include simple liquids, electron systems and correlations, two-dimensional

  19. Modulation of Higher Order Chromatin Conformation in Mammalian Cell Nuclei Can Be Mediated by Polyamines and Divalent Cations.

    Directory of Open Access Journals (Sweden)

    Ashwat Visvanathan

    Full Text Available The organisation of the large volume of mammalian genomic DNA within cell nuclei requires mechanisms to regulate chromatin compaction involving the reversible formation of higher order structures. The compaction state of chromatin varies between interphase and mitosis and is also subject to rapid and reversible change upon ATP depletion/repletion. In this study we have investigated mechanisms that may be involved in promoting the hyper-condensation of chromatin when ATP levels are depleted by treating cells with sodium azide and 2-deoxyglucose. Chromatin conformation was analysed in both live and permeabilised HeLa cells using FLIM-FRET, high resolution fluorescence microscopy and by electron spectroscopic imaging microscopy. We show that chromatin compaction following ATP depletion is not caused by loss of transcription activity and that it can occur at a similar level in both interphase and mitotic cells. Analysis of both live and permeabilised HeLa cells shows that chromatin conformation within nuclei is strongly influenced by the levels of divalent cations, including calcium and magnesium. While ATP depletion results in an increase in the level of unbound calcium, chromatin condensation still occurs even in the presence of a calcium chelator. Chromatin compaction is shown to be strongly affected by small changes in the levels of polyamines, including spermine and spermidine. The data are consistent with a model in which the increased intracellular pool of polyamines and divalent cations, resulting from depletion of ATP, bind to DNA and contribute to the large scale hyper-compaction of chromatin by a charge neutralisation mechanism.

  20. Preventing freezing of condensate inside tubes of air cooled condenser

    Energy Technology Data Exchange (ETDEWEB)

    Joo, Jeong A; Hwang, In Hwan; Lee, Dong Hwan [Chonbuk Nat' l Univ., Jeonju (Korea, Republic of); Cho, Young Il [Drexel Univ., Philadelphia (United States)

    2012-08-15

    An air cooled condenser is a device that is used for converting steam into condensate by using ambient air. The air cooled condenser is prone to suffer from a serious explosion when the condensate inside the tubes of a heat exchanger is frozen; in particular, tubes can break during winter. This is primarily due to the structural problem of the tube outlet of an existing conventional air cooled condenser system, which causes the backflow of residual steam and noncondensable gases. To solve the backflow problem in such condensers, such a system was simulated and a new system was designed and evaluated in this study. The experimental results using the simulated condenser showed the occurrence of freezing because of the backflow inside the tube. On the other hand, no backflow and freezing occurred in the advanced new condenser, and efficient heat exchange occurred.

  1. Condensed Matter Physics

    Science.gov (United States)

    Marder, Michael P.

    2000-01-01

    A modern, unified treatment of condensed matter physics This new work presents for the first time in decades a sweeping review of the whole field of condensed matter physics. It consolidates new and classic topics from disparate sources, teaching "not only about the effective masses of electrons in semiconductor crystals and band theory, but also about quasicrystals, dynamics of phase separation, why rubber is more floppy than steel, electron interference in nanometer-sized channels, and the quantum Hall effect." Six major areas are covered---atomic structure, electronic structure, mechanical properties, electron transport, optical properties, and magnetism. But rather than defining the field in terms of particular materials, the author focuses on the way condensed matter physicists approach physical problems, combining phenomenology and microscopic arguments with information from experiments. For graduate students and professionals, researchers and engineers, applied mathematicians and materials scientists, Condensed Matter Physics provides: * An exciting collection of new topics from the past two decades. * A thorough treatment of classic topics, including band theory, transport theory, and semiconductor physics. * Over 300 figures, incorporating many images from experiments. * Frequent comparison of theory and experiment, both when they agree and when problems are still unsolved. * More than 50 tables of data and a detailed index. * Ample end-of-chapter problems, including computational exercises. * Over 1000 references, both recent and historically significant.

  2. Soft condensed matter

    NARCIS (Netherlands)

    Frenkel, D.

    2002-01-01

    These lectures illustrate some of the concepts of soft-condensed matter physics, taking examples from colloid physics. Many of the theoretical concepts will be illustrated with the results of computer simulations. After a brief introduction describing interactions between colloids, the paper focuses

  3. Condensed landscape experience

    DEFF Research Database (Denmark)

    Earon, Ofri

    2011-01-01

    . This paper addresses the question of whether the sensation of landscape can be condensed in function or to the size of an urban building. It also discusses the benefits and potentials of the amalgamate, by underlining the unique qualities of such a hybrid. In an attempt to define the experience of landscape...

  4. Interactions between cationic liposomes and drugs or biomolecules

    Directory of Open Access Journals (Sweden)

    ANA MARIA CARMONA-RIBEIRO

    2000-03-01

    Full Text Available Multiple uses for synthetic cationic liposomes composed of dioctadecyldimethylammonium bromide (DODAB bilayer vesicles are presented. Drugs or biomolecules can be solubilized or incorporated in the cationic bilayers. The cationic liposomes themselves can act as antimicrobial agents causing death of bacteria and fungi at concentrations that barely affect mammalian cells in culture. Silica particles or polystyrene microspheres can be functionalized by coverage with DODAB bilayers or phospholipid monolayers. Negatively charged antigenic proteins can be carried by the cationic liposomes which generate a remarkable immunoadjuvant action. Nucleotides or DNA can be physically adsorbed to the cationic liposomes to be transferred to mammalian cells for gene therapy. An overview of the interactions between DODAB vesicles and some biomolecules or drugs clearly points out their versatility for useful applications in a near future.

  5. Interactions between cationic liposomes and drugs or biomolecules.

    Science.gov (United States)

    Carmona-Ribeiro, A M

    2000-01-01

    Multiple uses for synthetic cationic liposomes composed of dioctadecyldimethylammonium bromide (DODAB) bilayer vesicles are presented. Drugs or biomolecules can be solubilized or incorporated in the cationic bilayers. The cationic liposomes themselves can act as antimicrobial agents causing death of bacteria and fungi at concentrations that barely affect mammalian cells in culture. Silica particles or polystyrene microspheres can be functionalized by coverage with DODAB bilayers or phospholipid monolayers. Negatively charged antigenic proteins can be carried by the cationic liposomes which generate a remarkable immunoadjuvant action. Nucleotides or DNA can be physically adsorbed to the cationic liposomes to be transferred to mammalian cells for gene therapy. An overview of the interactions between DODAB vesicles and some biomolecules or drugs clearly points out their versatility for useful applications in a near future.

  6. Domains of Disoriented Chiral Condensate

    CERN Document Server

    Amado, R D; Lu, Yang

    1996-01-01

    The probability distribution of neutral pion fraction from independent domains of disoriented chiral condensate is characterized. The signal for the condensate is clear for a small number of domains but is greatly reduced for more than three.

  7. DNA quantification based on FRET realized by combination with surfactant CPB.

    Science.gov (United States)

    Liu, Chunxia; Wang, Lei; Jiang, Wei

    2010-04-15

    In this work, we developed a novel DNA quantitative analysis based on fluorescence resonance energy transfer (FRET) realized by combination with a surfactant CPB. The approach was capable of detecting long-stranded DNA in a separation-free format. A sandwich-type FAM-c-DNA-t-DNA-r-DNA-TAMRA conjugate was first formed by the capture probe tagged with FAM, the reporter probe tagged with TAMRA and the target DNA through hybridization. The donor (FAM) and the acceptor (TAMRA) were bridged to afford a FRET system. Subsequently, an addition of the cationic surfactant CPB to the system resulted in a substantial change of the microenvironment and an effective condensation of DNA strands. Consequently, without altering the component of the double strands, an enhanced acceptor fluorescence signal from FRET was achieved and a quantification of the target DNA containing 30 bases was enabled. Under the optimal experimental conditions, an excellent linear relationship between the increase of acceptor fluorescent peak area and the target DNA concentration was obtained over the range from 1.0 x 10(-7) to 3.0 x 10(-9) mol L(-1). The proposed approach offered adequate sensitivity for the detection of the target DNA at 1.0 x 10(-9) mol L(-1).

  8. Statistical physics and condensed matter

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2003-07-01

    This document is divided into 4 sections: 1) General aspects of statistical physics. The themes include: possible geometrical structures of thermodynamics, the thermodynamical foundation of quantum measurement, transport phenomena (kinetic theory, hydrodynamics and turbulence) and out of equilibrium systems (stochastic dynamics and turbulence). The techniques involved here are typical of applied analysis: stability criteria, mode decomposition, shocks and stochastic equations. 2) Disordered, glassy and granular systems: statics and dynamics. The complexity of the systems can be studied through the structure of their phase space. The geometry of this phase space is studied in several works: the overlap distribution can now be computed with a very high precision; the boundary energy between low lying states does not behave like in ordinary systems; and the Edward's hypothesis of equi-probability of low lying metastable states is invalidated. The phenomenon of aging, characteristic of glassy dynamics, is studied in several models. Dynamics of biological systems or of fracture is shown to bear some resemblance with that of disordered systems. 3) Quantum systems. The themes include: mesoscopic superconductors, supersymmetric approach to strongly correlated electrons, quantum criticality and heavy fermion compounds, optical sum rule violation in the cuprates, heat capacity of lattice spin models from high-temperature series expansion, Lieb-Schultz-Mattis theorem in dimension larger than one, quantum Hall effect, Bose-Einstein condensation and multiple-spin exchange model on the triangular lattice. 4) Soft condensed matter and biological systems. Path integral representations are invaluable to describe polymers, proteins and self-avoiding membranes. Using these methods, problems as diverse as the titration of a weak poly-acid by a strong base, the denaturation transition of DNA or bridge-hopping in conducting polymers have been addressed. The problems of RNA folding

  9. Photon condensation: A new paradigm for Bose-Einstein condensation

    Science.gov (United States)

    Rajan, Renju; Ramesh Babu, P.; Senthilnathan, K.

    2016-10-01

    Bose-Einstein condensation is a state of matter known to be responsible for peculiar properties exhibited by superfluid Helium-4 and superconductors. Bose-Einstein condensate (BEC) in its pure form is realizable with alkali atoms under ultra-cold temperatures. In this paper, we review the experimental scheme that demonstrates the atomic Bose-Einstein condensate. We also elaborate on the theoretical framework for atomic Bose-Einstein condensation, which includes statistical mechanics and the Gross-Pitaevskii equation. As an extension, we discuss Bose-Einstein condensation of photons realized in a fluorescent dye filled optical microcavity. We analyze this phenomenon based on the generalized Planck's law in statistical mechanics. Further, a comparison is made between photon condensate and laser. We describe how photon condensate may be a possible alternative for lasers since it does not require an energy consuming population inversion process.

  10. Efficient gene transfection using novel cationic polymers poly(hydroxyalkylene imines).

    Science.gov (United States)

    Zaliauskiene, Lolita; Bernadisiute, Ula; Vareikis, Ausvydas; Makuska, Ricardas; Volungeviciene, Ieva; Petuskaite, Agne; Riauba, Laurynas; Lagunavicius, Arunas; Zigmantas, Sarunas

    2010-09-15

    A series of novel cationic polymers poly(hydroxyalkylene imines) were synthesized and tested for their ability to transfect cells in vitro and in vivo. Poly(hydroxyalkylene imines), in particular, poly(2-hydroxypropylene imine) (pHP), poly(2-hydroxypropylene imine ethylene imine) (pHPE), and poly(hydroxypropylene imine propylene imine) (pHPP) were synthesized by polycondensation reaction from 1,3-diamino-2-propanol and the appropriate dibromide. Electron microscopic examination demonstrated that the resulting polymers condensed DNA into toroid shape complexes of 100-150 nm in size. Transfection studies showed that all three polymers were able to deliver genetic material into the cell, with pHP being superior to pHPP and pHPE. pHP acted as an efficient gene delivery agent in a variety of different cell lines and outcompeted most of the widely used polymer or lipid based transfection reagents. Intravenous administration of pHP-DNA polyplexes in mice followed by the reporter gene analysis showed that the reagent was suitable for in vivo applications. In summary, the results indicate that pHP is a new efficient reagent for gene delivery in vitro and in vivo.

  11. Condensed matter physics

    CERN Document Server

    Marder, Michael P

    2010-01-01

    This Second Edition presents an updated review of the whole field of condensed matter physics. It consolidates new and classic topics from disparate sources, teaching not only about the effective masses of electrons in semiconductor crystals and band theory, but also about quasicrystals, dynamics of phase separation, why rubber is more floppy than steel, granular materials, quantum dots, Berry phases, the quantum Hall effect, and Luttinger liquids.

  12. Chaos of chiral condensate

    CERN Document Server

    Hashimoto, Koji; Yoshida, Kentaroh

    2016-01-01

    Assigning a chaos index for vacua of generic quantum field theories is a challenging problem. We find chaotic behavior of chiral condensates of a quantum gauge theory at strong coupling limit, by using the AdS/CFT correspondence. We evaluate the time evolution of homogeneous quark condensates and in an N=2 supersymmetric QCD with the SU(N_c) gauge group at large N_c and at large 't Hooft coupling lambda. At an equivalent classical gravity picture, a Lyapunov exponent is readily defined. We show that the condensates exhibit chaotic behavior for energy density E > (6x10^2) (N_c/lambda^2) (m_q)^4 where m_q is the quark mass. The energy region of the chaotic vacua of the N=2 supersymmetric QCD increases for smaller N_c or larger lambda. The Lyapunov exponent is calculated as a function of the theory (N_c,lambda,E), showing that the N=2 supersymmetric QCD is more chaotic for smaller N_c.

  13. Asymmetric condensed dark matter

    CERN Document Server

    Aguirre, Anthony

    2015-01-01

    We explore the viability of a boson dark matter candidate with an asymmetry between the number densities of particles and antiparticles. A simple thermal field theory analysis confirms that, under certain general conditions, this component would develop a Bose-Einstein condensate in the early universe that, for appropriate model parameters, could survive the ensuing cosmological evolution until now. The condensation of a dark matter component in equilibrium with the thermal plasma is a relativistic process, hence the amount of matter dictated by the charge asymmetry is complemented by a hot relic density frozen out at the time of decoupling. Contrary to the case of ordinary WIMPs, dark matter particles in a condensate can be very light, $10^{-22}\\,{\\rm eV} \\lesssim m \\lesssim 10^2\\,{\\rm eV}$; the lower limit arises from constraints on small-scale structure formation, while the upper bound ensures that the density from thermal relics is not too large. Big-Bang nucleosynthesis constrains the temperature of deco...

  14. Asymmetric condensed dark matter

    Science.gov (United States)

    Aguirre, Anthony; Diez-Tejedor, Alberto

    2016-04-01

    We explore the viability of a boson dark matter candidate with an asymmetry between the number densities of particles and antiparticles. A simple thermal field theory analysis confirms that, under certain general conditions, this component would develop a Bose-Einstein condensate in the early universe that, for appropriate model parameters, could survive the ensuing cosmological evolution until now. The condensation of a dark matter component in equilibrium with the thermal plasma is a relativistic process, hence the amount of matter dictated by the charge asymmetry is complemented by a hot relic density frozen out at the time of decoupling. Contrary to the case of ordinary WIMPs, dark matter particles in a condensate must be lighter than a few tens of eV so that the density from thermal relics is not too large. Big-Bang nucleosynthesis constrains the temperature of decoupling to the scale of the QCD phase transition or above. This requires large dark matter-to-photon ratios and very weak interactions with standard model particles.

  15. Novel cationic SLN containing a synthesized single-tailed lipid as a modifier for gene delivery

    Energy Technology Data Exchange (ETDEWEB)

    Yu Wangyang; Liu Chunxi; Ye Jiesheng; Zou Weiwei; Zhang Na; Xu Wenfang [School of Pharmaceutical Sciences, Shandong University, 44 Wenhua Xi Road, Ji' nan (China)], E-mail: zhangnancy9@sdu.edu.cn

    2009-05-27

    Cationic solid lipid nanoparticles (SLN) can bind DNA directly via ionic interaction and mediate in vitro gene transfection. However, toxicity is still an obstacle, which is strongly dependent on the cationic lipid used. In the present study, a novel single-tailed cationic lipid, 6-lauroxyhexyl lysinate (LHLN), was synthesized and used as a modifier to prepare stable SLN-DNA complexes by a nanoprecipitation method. The commonly used cationic lipid cetyltrimethylammonium bromide (CTAB) modified SLN-DNA formulation served as a contrast. These two formulations were characterized and compared in terms of morphology, particle size, surface charge, DNA binding capacity, release profile, cytotoxicity, and transfection efficiency. The LHLN SLN-DNA complexes had a similar spherical morphology, a relatively narrow particle size distribution and a more remarkable DNA loading capability compared to the CTAB ones. Most importantly, LHLN modified SLN had a higher gene transfection efficiency than the naked DNA and CTAB ones, which was approximately equal to that of Lipofectamine-DNA complexes, and a lower cytotoxicity compared with CTAB-SLN and Lipofectamine 2000. Thus, the novel cationic SLN can achieve efficient transfection of plasmid DNA, and to some extent reduce the cytotoxicity, which might overcome some drawbacks of the conventional cationic nanocarriers in vivo and may become a promising non-viral gene therapy vector.

  16. Novel cationic SLN containing a synthesized single-tailed lipid as a modifier for gene delivery

    Science.gov (United States)

    Yu, Wangyang; Liu, Chunxi; Ye, Jiesheng; Zou, Weiwei; Zhang, Na; Xu, Wenfang

    2009-05-01

    Cationic solid lipid nanoparticles (SLN) can bind DNA directly via ionic interaction and mediate in vitro gene transfection. However, toxicity is still an obstacle, which is strongly dependent on the cationic lipid used. In the present study, a novel single-tailed cationic lipid, 6-lauroxyhexyl lysinate (LHLN), was synthesized and used as a modifier to prepare stable SLN-DNA complexes by a nanoprecipitation method. The commonly used cationic lipid cetyltrimethylammonium bromide (CTAB) modified SLN-DNA formulation served as a contrast. These two formulations were characterized and compared in terms of morphology, particle size, surface charge, DNA binding capacity, release profile, cytotoxicity, and transfection efficiency. The LHLN SLN-DNA complexes had a similar spherical morphology, a relatively narrow particle size distribution and a more remarkable DNA loading capability compared to the CTAB ones. Most importantly, LHLN modified SLN had a higher gene transfection efficiency than the naked DNA and CTAB ones, which was approximately equal to that of Lipofectamine-DNA complexes, and a lower cytotoxicity compared with CTAB-SLN and Lipofectamine 2000. Thus, the novel cationic SLN can achieve efficient transfection of plasmid DNA, and to some extent reduce the cytotoxicity, which might overcome some drawbacks of the conventional cationic nanocarriers in vivo and may become a promising non-viral gene therapy vector.

  17. Is countercurrent regeneration an option for condensate polishing? Yes, it is.

    Energy Technology Data Exchange (ETDEWEB)

    Daucik, K. [DONG Energy Generation A/S, Fredericia (Denmark)

    2008-03-15

    This paper presents a brief report on operation experience with a three-train separate bed condensate polisher in countercurrent operation/regeneration mode installed at a 400 MW ultra supercritical unit. Operation data show that the quality of the polished condensate is superior to that of the previously used standard (cation-mixed bed) condensate polisher, and it has been possible to almost completely eliminate sodium sulfate-related deposition problems in the plant cycle experienced when operating with that standard design unit. (orig.)

  18. Niosomes based on synthetic cationic lipids for gene delivery: the influence of polar head-groups on the transfection efficiency in HEK-293, ARPE-19 and MSC-D1 cells.

    Science.gov (United States)

    Ojeda, E; Puras, G; Agirre, M; Zárate, J; Grijalvo, S; Pons, R; Eritja, R; Martinez-Navarrete, G; Soto-Sanchez, C; Fernández, E; Pedraz, J L

    2015-01-28

    We designed niosomes based on three lipids that differed only in the polar-head group to analyze their influence on the transfection efficiency. These lipids were characterized by small-angle X-ray scattering before being incorporated into the niosomes which were characterized in terms of pKa, size, zeta potential, morphology and physical stability. Nioplexes were obtained upon the addition of a plasmid. Different ratios (w/w) were selected to analyze the influence of this parameter on size, charge and the ability to condense, release and protect the DNA. In vitro transfection experiments were performed in HEK-293, ARPE-19 and MSC-D1 cells. Our results show that the chemical composition of the cationic head-group clearly affects the physicochemical parameters of the niosomes and especially the transfection efficiency. Only niosomes based on cationic lipids with a dimethyl amino head group (lipid 3) showed a transfection capacity when compared with their counterparts amino (lipid 1) and tripeptide head-groups (lipid 2). Regarding cell viability, we clearly observed that nioplexes based on the cationic lipid 3 had a more deleterious effect than their counterparts, especially in ARPE-19 cells at 20/1 and 30/1 ratios. Similar studies could be extended to other series of cationic lipids in order to progress in the research on safe and efficient non-viral vectors for gene delivery purposes.

  19. Condensed Matter Nuclear Science

    Science.gov (United States)

    Biberian, Jean-Paul

    2006-02-01

    1. General. A tribute to gene Mallove - the "Genie" reactor / K. Wallace and R. Stringham. An update of LENR for ICCF-11 (short course, 10/31/04) / E. Storms. New physical effects in metal deuterides / P. L. Hagelstein ... [et al.]. Reproducibility, controllability, and optimization of LENR experiments / D. J. Nagel -- 2. Experiments. Electrochemistry. Evidence of electromagnetic radiation from Ni-H systems / S. Focardi ... [et al.]. Superwave reality / I. Dardik. Excess heat in electrolysis experiments at energetics technologies / I. Dardik ... [et al.]. "Excess heat" during electrolysis in platinum/K[symbol]CO[symbol]/nickel light water system / J. Tian ... [et al.]. Innovative procedure for the, in situ, measurement of the resistive thermal coefficient of H(D)/Pd during electrolysis; cross-comparison of new elements detected in the Th-Hg-Pd-D(H) electrolytic cells / F. Celani ... [et al.]. Emergence of a high-temperature superconductivity in hydrogen cycled Pd compounds as an evidence for superstoihiometric H/D sites / A. Lipson ... [et al.]. Plasma electrolysis. Calorimetry of energy-efficient glow discharge - apparatus design and calibration / T. B. Benson and T. O. Passell. Generation of heat and products during plasma electrolysis / T. Mizuno ... [et al.]. Glow discharge. Excess heat production in Pd/D during periodic pulse discharge current in various conditions / A. B. Karabut. Beam experiments. Accelerator experiments and theoretical models for the electron screening effect in metallic environments / A. Huke, K. Czerski, and P. Heide. Evidence for a target-material dependence of the neutron-proton branching ratio in d+d reactions for deuteron energies below 20keV / A. Huke ... [et al.]. Experiments on condensed matter nuclear events in Kobe University / T. Minari ... [et al.]. Electron screening constraints for the cold fusion / K. Czerski, P. Heide, and A. Huke. Cavitation. Low mass 1.6 MHz sonofusion reactor / R. Stringham. Particle detection. Research

  20. Convective condensation heat transfer in a horizontal condenser tube

    Energy Technology Data Exchange (ETDEWEB)

    Sarma, P.K. [College of Engineering, GITAM, Visakhapatnam (India); Sastry, C.V.N.; Rao, V.D. [Andhra Univ., College of Engineering, Visakhapatnam (India); Kakac, S.; Liu, H. [Miami Univ., College of Engineering, FL (United States)

    2002-03-01

    The purpose of this article is to solve analytically the problem of convective condensation of vapors inside a horizontal condenser tube. Homogeneous model approach is employed in the estimation of shear velocity, which is subsequently, made use of in predicting local convective condensation heat transfer coefficients. The resulting analysis of the present study is compared with some of the available equations in the literature. It is observed that the agreement is reasonably satisfactory validating the assumptions and the theory presented. (authors)

  1. Superfluidity in polariton condensates

    Energy Technology Data Exchange (ETDEWEB)

    Amo, A; Lefrere, J; Adrados, C; Giacobino, E; Bramati, A [Laboratoire Kastler Brossel, UPMC, ENS and CNRS, 75005 Paris (France); Sanvitto, D; Laussy, F P; Ballarini, D; Valle, E del; MartIn, M D; Tejedor, C; Vina, L [SEMICUAM, Universidad Autonoma de Madrid, 28049 Madrid (Spain); Pigeon, S; Ciuti, C [Laboratoire Materiaux et Phenomenes Quantiques, UMR 7162, Universite Paris Diderot-Paris 7 and CNRS, 75013 Paris (France); Carusotto, I [BEC-CNR-INFM and Dip. di Fisica, Universita di Trento, I-38050 Povo (Italy); Houdre, R [Institut de Photonique et d' Electronique Quantique, Ecole Polytechnique Federale de Lausanne, Station 3, CH-1015 Lausanne (Switzerland); LemaItre, A; Bloch, J [Laboratoire de Photonique et de Nanostructures, CNRS, Route de Nozay, 91460 Marcoussis (France); Krizhanovskii, D N; Skolnick, M S, E-mail: alberto.amo@spectro.jussieu.f [Department of Physics and Astronomy, University of Sheffield, S3 7RH, Sheffield (United Kingdom)

    2010-02-01

    Exciton-polaritons, two-dimensional composite bosons arising from the quantum mixture of excitons and photons, can manifest many-body quantum effects at liquid He temperatures (4 K). Interestingly, polaritons are predicted to behave as particular quantum fluids due to their out of equilibrium character, arising from their reduced lifetime (shorter than their thermalization time). Here we report the observation of superfluid motion of polaritons in semiconductor microcavities both under cw and pulsed excitation. Among other signatures, superfluidity is manifested via the absence of scattering of the polariton condensates when encountering a localized defect in their flow path.

  2. Nanocarbon condensation in detonation

    Science.gov (United States)

    Bastea, Sorin

    2017-01-01

    We analyze the definition of the Gibbs free energy of a nanoparticle in a reactive fluid environment, and propose an approach for predicting the size of carbon nanoparticles produced by the detonation of carbon-rich explosives that regards their condensation as a nucleation process and takes into account absolute entropy effects of the cluster population. The results are consistent with experimental observations and indicate that such entropy considerations are important for determining chemical equilibrium states in energetic materials that contain an excess of carbon. The analysis may be useful for other applications that deal with the nucleation of nanoparticles under reactive conditions. PMID:28176827

  3. Galaxies as condensates

    CERN Document Server

    Bugg, D V

    2012-01-01

    A novel interpretation of MOND is presented. For galactic data, in addition to Newtonian acceleration, there is an attractive acceleration peaking at Milgrom's parameter a_0. The peak lies within experimental error where a_0 = cH_0/2\\pi and H_0 is the present-time value of the Hubble constant. This peaking may be understood in terms of quantum mechanical mixing between Newtonian gravitation and the Hubble mechanism. There are five pointers towards galaxies being Fermi-Dirac condensates.

  4. Confinement Contains Condensates

    Energy Technology Data Exchange (ETDEWEB)

    Brodsky, Stanley J.; Roberts, Craig D.; Shrock, Robert; Tandy, Peter C.

    2012-03-12

    Dynamical chiral symmetry breaking and its connection to the generation of hadron masses has historically been viewed as a vacuum phenomenon. We argue that confinement makes such a position untenable. If quark-hadron duality is a reality in QCD, then condensates, those quantities that have commonly been viewed as constant empirical mass-scales that fill all spacetime, are instead wholly contained within hadrons; i.e., they are a property of hadrons themselves and expressed, e.g., in their Bethe-Salpeter or light-front wave functions. We explain that this paradigm is consistent with empirical evidence, and incidentally expose misconceptions in a recent Comment.

  5. Topology and Fermionic Condensate

    Science.gov (United States)

    Kulikov, I.; Pronin, P.

    The purpose of this paper is to investigate an influence of a space-time topology on the formation of fermionic condensate in the model with four-fermion interaction ()2. The value for the space-time with topology of R1 × R1 × S1 is found. Moreover a relation of the value of fermionic condensate to a periodic length is studied. In this connection the possibility of a relation of the topologic deposits to structure of hadrons is discussed.Translated AbstractTopologie und FermikondensatEs wird der Einfluß einer Raum-Zeittopologie auf die Bildung des Fermikondensats in einem Modell mit Vierfermionenwechselwirkung ()2 untersucht. Für eine Raum-Zeit mit der Topologie R1 × R2 × S1 werden die Parameter gegeben. Weiterhin wird die Relation der Größe des Fermikondensats zu einer periodischen Länge untersucht. In diesem Zusammenhang wird die Verbindung des topologischen Depots zur Struktur der Hadronen diskutiert.

  6. Polariton condensates put in motion

    Energy Technology Data Exchange (ETDEWEB)

    Sanvitto, D; Amo, A; Vina, L [Departamento de Fisica de Materiales, Universidad Autonoma de Madrid, E-28049, Madrid (Spain); Laussy, F P; Tejedor, C [Departamento de Fisica Teorica de la Materia Condensada, Universidad Autonoma de Madrid, E-28049, Madrid (Spain); LemaItre, A; Bloch, J, E-mail: daniele.sanvitto@uam.es [LPN/CNRS, Route de Nozay, F-91460, Marcoussis (France)

    2010-04-02

    We present several examples of the interesting phenomenology shown by a moving polariton condensate in semiconductor microcavities. The superfluid behavior is probed by colliding the polariton condensate against physical obstacles in the form of natural defects of the sample, demonstrating a clear suppression of scattering when the speed of the flow lies below the critical velocity. At higher velocities Cerenkov-like shock waves around the defect and disruption of the condensate are also observed.

  7. Dynamic constitutional frameworks for DNA biomimetic recognition.

    Science.gov (United States)

    Catana, Romina; Barboiu, Mihail; Moleavin, Ioana; Clima, Lilia; Rotaru, Alexandru; Ursu, Elena-Laura; Pinteala, Mariana

    2015-02-07

    Linear and cross-linked dynamic constitutional frameworks generated from reversibly interacting linear PEG/core constituents and cationic sites shed light on the dominant coiling versus linear DNA binding behaviours, closer to the histone DNA binding wrapping mechanism.

  8. Nonequilibrium Weak Processes in Kaon Condensation; 2, Kinetics of condensation

    CERN Document Server

    Muto, T; Iwamoto, N; Muto, Takumi; Tatsumi, Toshitaka; Iwamoto, Naoki

    2000-01-01

    The kinetics of negatively charged kaon condensation in the early stages of a newly born neutron star is considered. The thermal kaon process, in which kaons are thermally produced by nucleon-nucleon collisions, is found to be dominant throughout the equilibration process. Temporal changes of the order parameter of the condensate and the number densities of the chemical species are obtained from the rate equations, which include the thermal kaon reactions as well as the kaon-induced Urca and the modified Urca reactions. It is shown that the dynamical evolution of the condensate is characterized by three stages: the first, prior to establishment of a condensate, the second, during the growth and subsequent saturation of the condensate, and the third, near chemical equilibrium. The connection between the existence of a soft kaon mode and the instability of the noncondensed state is discussed. Implications of the nonequilibrium process on the possible delayed collapse of a protoneutron star are also mentioned.

  9. Condensation Processes in Geothermal Systems

    Science.gov (United States)

    Norman, D. I.; Moore, J. N.

    2005-12-01

    We model condensation processes in geothermal systems to understand how this process changes fluid chemistry. We assume two processes operate in geothermal systems: 1) condensation of a vapor phase derived by boiling an aqueous geothermal fluid into a cool near surface water and 2) condensation of a magmatic vapor by a deep circulating meteoric thermal fluid. It is assumed that the condensation process has two stages. Initially the condensing fluid is under saturated in gaseous species. Condensation of the vapor phase continues until the pressure on the fluid equals the sum of the partial pressures of water and the dissolved gaseous species. At that time bubbles flux through the condensing fluid. In time the fluid and fluxing gas phase come to equilibrium. Calculation shows that during the second stage of the condensation process the liquid phase becomes enriched in more soluble gaseous species like CO2 and H2S, and depleted in less soluble species like CH4 and N2. Stage 2 condensation processes can therefore be monitored by ratios of more and less condensable species like CO2/N2. Condensation of vapor released by boiling geothermal fluids results in liquids with high concentrations of H2S and CO2 like is seen in geothermal system steam-heated waters. Condensation of a magmatic vapor into circulating meteoric water has been proposed, but not well demonstrated. We compare to our models the Cerro Prieto, Mexico gas analysis data set collected over twelve years time by USGS personnel. It was assumed for modeling that the Cerro Prieto geothermal fluids are circulating meteoritic fluids with N2/Ar ratios about 40 to which is added a magmatic vapor with N2/Ar ratio = 400. The Cerro Prieto analyses show a strong correlation between N2/Ar and CO2/N2 as predicted by calculation. Two dimensional image plots of well N2/Ar + CO2/N2 show a bull's-eye pattern on the geothermal field. Image plots of analyses collected over a year or less time show N2/Ar and CO2/N2 hot spots

  10. Microgravity condensing heat exchanger

    Science.gov (United States)

    Thomas, Christopher M. (Inventor); Ma, Yonghui (Inventor); North, Andrew (Inventor); Weislogel, Mark M. (Inventor)

    2011-01-01

    A heat exchanger having a plurality of heat exchanging aluminum fins with hydrophilic condensing surfaces which are stacked and clamped between two cold plates. The cold plates are aligned radially along a plane extending through the axis of a cylindrical duct and hold the stacked and clamped portions of the heat exchanging fins along the axis of the cylindrical duct. The fins extend outwardly from the clamped portions along approximately radial planes. The spacing between fins is symmetric about the cold plates, and are somewhat more closely spaced as the angle they make with the cold plates approaches 90.degree.. Passageways extend through the fins between vertex spaces which provide capillary storage and communicate with passageways formed in the stacked and clamped portions of the fins, which communicate with water drains connected to a pump externally to the duct. Water with no entrained air is drawn from the capillary spaces.

  11. PPOOLEX experiments on wall condensation

    Energy Technology Data Exchange (ETDEWEB)

    Laine, J.; Puustinen, M. (Lappeenranta Univ. of Technology, Nuclear Safety Research Unit (Finland))

    2009-08-15

    This report summarizes the results of the wall condensation experiments carried out in December 2008 and January 2009 with the scaled down PPOOLEX test facility designed and constructed at Lappeenranta University of Technology. Steam was blown into the dry well compartment and from there through a DN200 blowdown pipe to the condensation pool. Altogether five experiments, each consisting of several blows, were carried out. The main purpose of the experiment series was to study wall condensation phenomenon inside the dry well compartment while steam is discharged through it into the condensation pool and to produce comparison data for CFD calculations at VTT. The PPOOLEX test facility is a closed stainless steel vessel divided into two compartments, dry well and wet well. For the wall condensation experiments the test facility was equipped with a system for collecting and measuring the amount of condensate from four different wall segments of the dry well compartment. A thermo graphic camera was used in a couple of experiments for filming the outside surface of the dry well wall. The effect of the initial temperature level of the dry well structures and of the steam flow rate for the accumulation of condensate was studied. The initial temperature level of the dry well structures varied from 23 to 99 deg. C. The steam flow rate varied from 90 to 690 g/s and the temperature of incoming steam from 115 to 160 deg. C. During the initial phase of steam discharge the accumulation of condensate was strongly controlled by the temperature level of the dry well structures; the lower the initial temperature level was the more condensate was accumulated. As the dry well structural temperatures increased the condensation process slowed down. Most of the condensate usually accumulated during the first 200 seconds of the discharge. However, the condensation process never completely stopped because a small temperature difference remained between the dry well atmosphere and inner wall

  12. Multivalent co-ions reduce DNA$-$DNA like-charge attraction and enhance DNA overcharging by mutivalent counterions

    CERN Document Server

    Duc, Nguyen Viet; Duc, Nguyen Huu

    2016-01-01

    Strongly correlated electrostatics of DNA systems has drawn the interest of many groups, especially the condensation and overcharging of DNA by multivalent counterions. By adding counterions of different valencies and shapes, one can enhance or reduce DNA overcharging. In this letter, we focus on the effect of multivalent co-ions, specifically divalent coion such as SO$_4^{2-}$, on the strongly correlated electrostatics of DNA condensation problem. A computational experiment of DNA condensation using Monte$-$Carlo simulation in grand canonical ensemble is carried out where DNA system is in equilibirium with a bulk solution containing a mixture of salt of different valency of co-ions. Compared to system with purely monovalent co-ions, the influence of divalent co-ions shows up in multiple aspects. Divalent co-ions lead to an increase of monovalent salt in the DNA condensate. Because monovalent salts mostly participate in linear screening of electrostatic interactions in the system, more monovalent salt molecul...

  13. Decay of Ultralight Axion Condensates

    Energy Technology Data Exchange (ETDEWEB)

    Eby, Joshua; Ma, Michael; Suranyi, Peter; Wijewardhana, L. C.R.

    2017-05-15

    Axion particles can form macroscopic condensates, whose size can be galactic in scale for models with very small axion masses $m\\sim10^{-22}$ eV, and which are sometimes referred to under the name of Fuzzy Dark Matter. Many analyses of these condensates are done in the non-interacting limit, due to the weakness of the self-interaction coupling of axions. We investigate here how certain results change upon inclusion of these interactions, finding a decreased maximum mass and a modified mass-radius relationship. Further, these condensates are, in general, unstable to decay through number-changing interactions. We analyze the stability of galaxy-sized condensates of axion-like particles, and sketch the parameter space of stable configurations as a function of a binding energy parameter. We find a strong lower bound on the size of Fuzzy Dark Matter condensates which are stable to decay, with lifetimes longer than the age of the universe.

  14. APPARATUS FOR CONDENSATION AND SUBLIMATION

    Science.gov (United States)

    Schmidt, R.J.; Fuis, F. Jr.

    1958-10-01

    An apparatus is presented for the sublimation and condensation of uranium compounds in order to obtain an improved crystalline structure of this material. The apparatus comprises a vaporizing chamber and condensing structure connected thereto. There condenser is fitted with a removable liner having a demountable baffle attached to the liner by means of brackets and a removable pin. The baffle is of spiral cross-section and is provided with cooling coils disposed between the surfaces of the baffle for circulation of a temperature controlling liquid within the baffle. The cooling coll provides for controlllng the temperature of the baffle to insure formatlon of a satisfactory condensate, and the removable liner facilitates the removal of condensate formed during tbe sublimation process.

  15. Left-handed DNA crossovers. Implications for DNA-DNA recognition and structural alterations.

    Science.gov (United States)

    Timsit, Y; Shatzky-Schwartz, M; Shakked, Z

    1999-02-01

    The close approach of DNA segments participates in many biological functions including DNA condensation and DNA processing. Previous crystallographic studies have shown that B-DNA self-fitting by mutual groove-backbone interaction produces right-handed DNA crossovers. These structures have opened new perspectives on the role of close DNA-DNA interactions in the architecture and activity the DNA molecule. In the present study, the analysis of the crystal packing of two B-DNA decamer duplexes d(CCIIICCCGG) and d(CCGCCGGCGG) reveals the existence of new modes of DNA crossing. Symmetric left-handed crossovers are produced by mutual fitting of DNA grooves at the crossing point. New sequence patterns contribute to stabilize longitudinal fitting of the sugar-phosphate backbone into the major groove. In addition, the close approach of DNA segments greatly influences the DNA conformation in a sequence dependent manner. This study provides new insights into the role of DNA sequence and structure in DNA-DNA recognition. In providing detailed molecular views of DNA crossovers of opposite chirality, this study can also help to elucidate the role of symmetry and chirality in the recognition of complex DNA structures by protein dimers or tetramers, such as topoisomerase II and recombinase enzymes. These results are discussed in the context of the possible relationships between DNA condensation and DNA processing.

  16. The superstructure of chromatin and its condensation mechanism. VI. Electric dichroism and model calculations.

    Science.gov (United States)

    Koch, M H; Sayers, Z; Michon, A M; Sicre, P; Marquet, R; Houssier, C

    1989-01-01

    Electric dichroism and X-ray scattering measurements on solutions of uncondensed and condensed chicken erythrocyte chromatin were interpreted on the basis of model calculations. Information about the state of uncondensed fibers in the conditions of electric dichroism measurements was obtained from scattering patterns recorded as a function of pH, in the presence of spermine and at very low monovalent cation concentrations. Electric dichroism measurements on a complex of uncondensed chromatin with methylene blue were made to determine the contribution of the linker and of the nucleosomes to the total dichroism. A new approach to calculate the dichroism from realistic structural models, which also yields other structural parameters (radius of gyration, radius of gyration of the cross-section, mass per unit length) was used. Only a restricted range of structures is simultaneously compatible with all experimental results. Further, it is shown that previous interpretations of dichroism measurements on chromatin were in contradiction with X-ray scattering data and failed to take into account the distribution of orientation of the nucleosomes in the fibers. When this is done, it is found that the linker DNA in chicken erythrocyte and sea urchin chromatin must run nearly perpendicularly to the fibre axis. Taken together with the dependence of the fibre diameter on the linker length, these results provide the strongest evidence hitherto available for a model in which the linker crosses the central part of the fibre.

  17. Independent Generation and Reactivity of Thymidine Radical Cations.

    Science.gov (United States)

    Sun, Huabing; Taverna Porro, Marisa L; Greenberg, Marc M

    2017-10-10

    Thymidine radical cation (1) is produced by ionizing radiation and has been invoked as an intermediate in electron transfer in DNA. Previous studies on its structure and reactivity have utilized thymidine as a precursor, which limits quantitative product analysis because thymidine is readily reformed from 1. In this investigation, radical cation 1 is independently generated via β-heterolysis of a pyrimidine radical generated photochemically from an aryl sulfide. Thymidine is the major product (33%) from 1 at pH 7.2. Diastereomeric mixtures of thymidine glycol and the corresponding 5-hydroxperoxides resulting from water trapping of 1 are formed. Significantly lower yields of products such as 5-formyl-2'-deoxyuridine that are ascribable to deprotonation from the C5-methyl group of 1 are observed. Independent generation of the N3-methyl analogue of 1 (NMe-1) produces considerably higher yields of products derived from water trapping, and these products are formed in much higher yields than those attributable to the C5-methyl group deprotonation in NMe-1. N3-Methyl-thymidine is, however, the major product and is produced in as high as 70% yield when the radical cation is produced in the presence of excess thiol. The effects of exogenous reagents on product distributions are consistent with the formation of diffusively free radical cations (1, NMe-1). This method should be compatible with producing radical cations at defined positions within DNA.

  18. Mitotic chromosome condensation in vertebrates

    Energy Technology Data Exchange (ETDEWEB)

    Vagnarelli, Paola, E-mail: P.Vagnarelli@ed.ac.uk

    2012-07-15

    Work from several laboratories over the past 10-15 years has revealed that, within the interphase nucleus, chromosomes are organized into spatially distinct territories [T. Cremer, C. Cremer, Chromosome territories, nuclear architecture and gene regulation in mammalian cells, Nat. Rev. Genet. 2 (2001) 292-301 and T. Cremer, M. Cremer, S. Dietzel, S. Muller, I. Solovei, S. Fakan, Chromosome territories-a functional nuclear landscape, Curr. Opin. Cell Biol. 18 (2006) 307-316]. The overall compaction level and intranuclear location varies as a function of gene density for both entire chromosomes [J.A. Croft, J.M. Bridger, S. Boyle, P. Perry, P. Teague,W.A. Bickmore, Differences in the localization and morphology of chromosomes in the human nucleus, J. Cell Biol. 145 (1999) 1119-1131] and specific chromosomal regions [N.L. Mahy, P.E. Perry, S. Gilchrist, R.A. Baldock, W.A. Bickmore, Spatial organization of active and inactive genes and noncoding DNA within chromosome territories, J. Cell Biol. 157 (2002) 579-589] (Fig. 1A, A'). In prophase, when cyclin B activity reaches a high threshold, chromosome condensation occurs followed by Nuclear Envelope Breakdown (NEB) [1]. At this point vertebrate chromosomes appear as compact structures harboring an attachment point for the spindle microtubules physically recognizable as a primary constriction where the two sister chromatids are held together. The transition from an unshaped interphase chromosome to the highly structured mitotic chromosome (compare Figs. 1A and B) has fascinated researchers for several decades now; however a definite picture of how this process is achieved and regulated is not yet in our hands and it will require more investigation to comprehend the complete process. From a biochemical point of view a vertebrate mitotic chromosomes is composed of DNA, histone proteins (60%) and non-histone proteins (40%) [6]. I will discuss below what is known to date on the contribution of these two different classes

  19. Condensation of tetragonal zirconia polycrystals by reactive sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Chen, I-M. [Institute of Materials Science and Engineering, National Sun Yat-sen University, Kaohsiung, Taiwan (China); Yeh, S.-W. [Institute of Materials Science and Engineering, National Sun Yat-sen University, Kaohsiung, Taiwan (China); Chiou, S.-Y. [Department of Mold and Die Engineering, National Kaohsiung University of Applied Science, Kaohsiung, Taiwan (China); Gan Dershin [Institute of Materials Science and Engineering, National Sun Yat-sen University, Kaohsiung, Taiwan (China)]. E-mail: dgan@mail.nsysu.edu.tw; Shen Pouyan [Institute of Materials Science and Engineering, National Sun Yat-sen University, Kaohsiung, Taiwan (China)

    2005-11-22

    Reactive sputtering on metallic Zr target under various oxygen flow rates was employed to produce nanocrystalline zirconia condensates, which were collected on a carbon-coated collodion film for analytical electron microscopic observations. With an Ar flow rate of 28 sccm, the collected condensates are cubic and tetragonal (t-) zirconia less than 10 nm in size under 0-2 sccm oxygen flow rate and increased to 10-20 nm in size with partial t- to monoclinic (m-) zirconia transformation at 3 sccm. Between 4 and 4.5 sccm, t-zirconia polycrystals (TZP) about 20 nm in grain size were formed by coalescence of the t-zirconia condensates. Above 6 sccm, the (111) and {l_brace}100{r_brace} specific coalescence as well as random attachment prevailed to form larger (> 30 nm) individual condensates of m-zirconia as the critical size of martensitic t-m transformation is exceeded. The TZP formation can be accounted for by the small grain size, the presence of low-valence Zr cation and the lateral constraint of neighboring grains.

  20. Advanced ion exchange resins for PWR condensate polishing

    Energy Technology Data Exchange (ETDEWEB)

    Hoffman, B. [Rohm and Haas Co. (United States); Tsuzuki, S. [Rohm and Haas Co. (Japan)

    2002-07-01

    The severe chemical and mechanical requirements of a pressurized water reactor (PWR) condensate polishing plant (CPP) present a major challenge to the design of ion exchange resins. This paper describes the development and initial operating experience of improved cation and anion exchange resins that were specifically designed to meet PWR CPP needs. Although this paper focuses specifically on the ion exchange resins and their role in plant performance, it is also recognized and acknowledged that excellent mechanical design and operation of the CPP system are equally essential to obtaining good results. (authors)

  1. Pds5 regulators segregate cohesion and condensation pathways in Saccharomyces cerevisiae.

    Science.gov (United States)

    Tong, Kevin; Skibbens, Robert V

    2015-06-02

    Cohesins are required both for the tethering together of sister chromatids (termed cohesion) and subsequent condensation into discrete structures-processes fundamental for faithful chromosome segregation into daughter cells. Differentiating between cohesin roles in cohesion and condensation would provide an important advance in studying chromatin metabolism. Pds5 is a cohesin-associated factor that is essential for both cohesion maintenance and condensation. Recent studies revealed that ELG1 deletion suppresses the temperature sensitivity of pds5 mutant cells. However, the mechanisms through which Elg1 may regulate cohesion and condensation remain unknown. Here, we report that ELG1 deletion from pds5-1 mutant cells results in a significant rescue of cohesion, but not condensation, defects. Based on evidence that Elg1 unloads the DNA replication clamp PCNA from DNA, we tested whether PCNA overexpression would similarly rescue pds5-1 mutant cell cohesion defects. The results indeed reveal that elevated levels of PCNA rescue pds5-1 temperature sensitivity and cohesion defects, but do not rescue pds5-1 mutant cell condensation defects. In contrast, RAD61 deletion rescues the condensation defect, but importantly, neither the temperature sensitivity nor cohesion defects exhibited by pds5-1 mutant cells. In combination, these findings reveal that cohesion and condensation are separable pathways and regulated in nonredundant mechanisms. These results are discussed in terms of a new model through which cohesion and condensation are spatially regulated.

  2. Synthesis, Characterization, and Flocculation Properties of Branched Cationic Polyacrylamide

    Directory of Open Access Journals (Sweden)

    Weimin Sun

    2013-01-01

    Full Text Available A water soluble branched cationic polyacrylamide (BCPAM was synthesized using solution polymerization. The polymerization was initiated using potassium diperiodatocuprate, K5[Cu(HIO62](Cu(III, initiating the self-condensing vinyl copolymerization of acrylamide and acryloxyethyltrimethyl ammonium chloride (DAC monomer. The resulting copolymer was characterized by the use of Fourier-transform infrared (FTIR spectroscopy and nuclear magnetic resonance (NMR spectroscopy. Its flocculation properties were evaluated with standard jar tests of sewage. The effects of initiator concentration, monomer concentration, reaction temperature, and the mass ratio of monomers on intrinsic viscosity and flocculation properties of the product were determined using single-factor experiments and orthogonal experiment.

  3. Antikaon condensation in neutron stars

    CERN Document Server

    Pal, S; Greiner, W

    2000-01-01

    We investigate the condensation of charged K sup - meson and neutral anti-K sup 0 meson in dense neutron star matter. Calculations are performed in relativistic mean field models in which both the baryon-baryon and (anti)kaon-baryon interactions are mediated by meson exchange. It is found that anti-K sup 0 condensation is quite sensitive to the antikaon optical potential and depends more strongly on the nucleonic equation of state. For moderate values of antikaon potential and a rather stiff equation of state, a significant region of maximum mass star will contain anti-K sup 0 meson. The critical density of anti-K sup 0 condensation is always higher than that of K sup - condensation. With the appearance of K sup - and anti-K sup 0 condensates, pairs of p-K sup - and n-Kbar sup 0 are produced with equal proportion leading to a perfectly symmetric matter of nucleons and antikaons in neutron stars. Along with K sup - condensate, anti-K sup 0 condensate makes the equation of state much softer resulting in smaller...

  4. Gas-phase energies of actinide oxides -- an assessment of neutral and cationic monoxides and dioxides from thorium to curium

    Energy Technology Data Exchange (ETDEWEB)

    Marcalo, Joaquim; Gibson, John K.

    2009-08-10

    An assessment of the gas-phase energetics of neutral and singly and doubly charged cationic actinide monoxides and dioxides of thorium, protactinium, uranium, neptunium, plutonium, americium, and curium is presented. A consistent set of metal-oxygen bond dissociation enthalpies, ionization energies, and enthalpies of formation, including new or revised values, is proposed, mainly based on recent experimental data and on correlations with the electronic energetics of the atoms or cations and with condensed-phase thermochemistry.

  5. A simple approach for producing highly efficient DNA carriers with reduced toxicity based on modified polyallylamine

    Energy Technology Data Exchange (ETDEWEB)

    Oskuee, Reza Kazemi [Neurogenic Inflammation Research Center, Mashhad University of Medical Sciences, Mashhad (Iran, Islamic Republic of); Department of Medical Biotechnology, School of Medicine, Mashhad University of Medical Sciences, Mashhad (Iran, Islamic Republic of); Dosti, Fatemeh [School of Pharmacy, Mashhad University of Medical Sciences, Mashhad (Iran, Islamic Republic of); Gholami, Leila [Targeted Drug Delivery Research Center, School of Medicine, Mashhad University of Medical Sciences, Mashhad (Iran, Islamic Republic of); Malaekeh-Nikouei, Bizhan, E-mail: malaekehb@mums.ac.ir [Nanotechnology Research Center, School of Pharmacy, Mashhad University of Medical Sciences, Mashhad (Iran, Islamic Republic of)

    2015-04-01

    Nowadays gene delivery is a topic in many research studies. Non-viral vectors have many advantages over viral vectors in terms of safety, immunogenicity and gene carrying capacity but they suffer from low transfection efficiency and high toxicity. In this study, polyallylamine (PAA), the cationic polymer, has been modified with hydrophobic branches to increase the transfection efficiency of the polymer. Polyallylamine with molecular weights of 15 and 65 kDa was selected and grafted with butyl, hexyl and decyl acrylate at percentages of 10, 30 and 50. The ability of the modified polymer to condense DNA was examined by ethidium bromide test. The complex of modified polymer and DNA (polyplex) was characterized for size, zeta potential, transfection efficiency and cytotoxicity in Neuro2A cell lines. The results of ethidium bromide test showed that grafting of PAA decreased its ability for DNA condensation but vectors could still condense DNA at moderate and high carrier to DNA ratios. Most of polyplexes had particle size between 150 and 250 nm. The prepared vectors mainly showed positive zeta potential but carriers composed of PAA with high percentage of grafting had negative zeta potential. The best transfection activity was observed in vectors with hexyl acrylate chain. Grafting of polymer reduced its cytotoxicity especially at percentages of 30 and 50. The vectors based of PAA 15 kDa had better transfection efficiency than the vectors made of PAA 65 kDa. In conclusion, results of the present study indicated that grafting PAA 15 kDa with high percentages of hexyl acrylate can help to prepare vectors with better transfection efficiency and less cytotoxicity. - Highlights: • The modified polyallylamine was synthesized as a gene carrier. • Modification of polyallylamine (15 kDa) with high percentages of hexyl acrylate improved transfection activity remarkably. • Grafting of polymer with acrylate derivatives reduced polymer cytotoxicity especially at percentages of

  6. Design of amphiphilic oligopeptides as models for fine tuning peptide assembly with plasmid DNA.

    Science.gov (United States)

    Goparaju, Geetha N; Gupta, Pardeep K

    2014-08-01

    We discuss the design of novel amphiphilic oligopeptides with hydrophobic and cationic amino acids to serve as models to understand peptide-DNA assembly. Biophysical and thermodynamic characterization of interaction of these amphiphilic peptides with plasmid DNA is presented. Peptides with at least +4 charges favor stable complex formation. Surface potential is dependent on the type of hydrophobic amino acid for a certain charge. Thermodynamically it is a spontaneous interaction between most of the peptides and plasmid DNA. Lys(7) and Tyr peptides with +4/+5 charges indicate cooperative binding with pDNA without saturation of interaction while Val(2)-Gly-Lys(4), Val-Gly-Lys(5), and Phe-Gly-Lys(5) lead to saturation of interaction indicating condensed pDNA within the range of N/Ps studied. We show that the biophysical properties of DNA-peptide complexes could be modulated by design and the peptides presented here could be used as building blocks for creating DNA-peptide complexes for various biomedical applications, mainly nucleic acid delivery.

  7. Efficient, Long-Life Biocidal Condenser Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Environmental control systems for manned lunar and planetary bases will require condensing heat exchangers to control humidity. Condensing surfaces must be...

  8. Efficient, Long-Life Biocidal Condenser Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Environmental control systems for manned lunar and planetary bases will require condensing heat exchangers to control humidity in manned modules. Condensing surfaces...

  9. Bose condensation in (random traps

    Directory of Open Access Journals (Sweden)

    V.A. Zagrebnov

    2009-01-01

    Full Text Available We study a non-interacting (perfect Bose-gas in random external potentials (traps. It is shown that a generalized Bose-Einstein condensation in the random eigenstates manifests if and only if the same occurs in the one-particle kinetic-energy eigenstates, which corresponds to the generalized condensation of the free Bose-gas. Moreover, we prove that the amounts of both condensate densities are equal. This statement is relevant for justification of the Bogoliubov approximation} in the theory of disordered boson systems.

  10. Cationic polymers and porous materials

    KAUST Repository

    Han, Yu

    2017-04-27

    According to one or more embodiments, cationic polymers may be produced which include one or more monomers containing cations. Such cationic polymers may be utilized as structure directing agents to form mesoporous zeolites. The mesoporous zeolites may include micropores as well as mesopores, and may have a surface area of greater than 350 m2/g and a pore volume of greater than 0.3 cm3/g. Also described are core/shell zeolites, where at least the shell portion includes a mesoporous zeolite material.

  11. Synthetic cation-selective nanotube: Permeant cations chaperoned by anions

    Science.gov (United States)

    Hilder, Tamsyn A.; Gordon, Dan; Chung, Shin-Ho

    2011-01-01

    The ability to design ion-selective, synthetic nanotubes which mimic biological ion channels may have significant implications for the future treatment of bacteria, diseases, and as ultrasensitive biosensors. We present the design of a synthetic nanotube made from carbon atoms that selectively allows monovalent cations to move across and rejects all anions. The cation-selective nanotube mimics some of the salient properties of biological ion channels. Before practical nanodevices are successfully fabricated it is vital that proof-of-concept computational studies are performed. With this in mind we use molecular and stochastic dynamics simulations to characterize the dynamics of ion permeation across a single-walled (10, 10), 36 Å long, carbon nanotube terminated with carboxylic acid with an effective radius of 5.08 Å. Although cations encounter a high energy barrier of 7 kT, its height is drastically reduced by a chloride ion in the nanotube. The presence of a chloride ion near the pore entrance thus enables a cation to enter the pore and, once in the pore, it is chaperoned by the resident counterion across the narrow pore. The moment the chaperoned cation transits the pore, the counterion moves back to the entrance to ferry another ion. The synthetic nanotube has a high sodium conductance of 124 pS and shows linear current-voltage and current-concentration profiles. The cation-anion selectivity ratio ranges from 8 to 25, depending on the ionic concentrations in the reservoirs.

  12. DNA Bar-Coding for Phytoplasma Identification

    DEFF Research Database (Denmark)

    Makarova, Olga; Contaldo, Nicoletta; Paltrinieri, Samanta

    2013-01-01

    Phytoplasma identi fi cation has proved dif fi cult due to their inability to be maintained in vitro. DNA barcoding is an identi fi cation method based on comparison of a short DNA sequence with known sequences from a database. A DNA barcoding tool has been developed for phytoplasma identi fi...... cation. While other sequencebased methods may be well adapted to identification of particular strains of phytoplasmas, often they cannot be used for the simultaneous identification of phytoplasmas from different groups. The phytoplasma DNA barcoding protocol in this chapter, based on the tuf and 16Sr...

  13. Flexible polyelectrolyte conformation in the presence of cationic and anionic surfactants

    Science.gov (United States)

    Passos, C. B.; Kuhn, P. S.; Diehl, A.

    2015-11-01

    In this work we have studied the conformation of flexible polyelectrolyte chains in the presence of cationic and anionic surfactant molecules. We developed a simple theoretical model for the formation of the polyelectrolyte-cationic surfactant complexes and mixed micelles formed by cationic and anionic surfactant molecules, in the framework of the Debye-Hückel-Bjerrum-Manning and Flory theories, with the hydrophobic interaction included explicitly as an effective short-ranged attraction between the surfactant hydrocarbon tails. This simple model allows us to calculate the extension of the polyelectrolyte-cationic surfactant complexes as a function of the anionic surfactant concentration, for different types of cationic and anionic surfactant molecules. A discrete conformational transition from a collapsed state to an elongated coil was found, for all surfactant chain lengths we have considered, in agreement with the experimental observations for the unfolding of ​DNA-cationic surfactant complexes.

  14. Nonequilibrium Thermodynamics of Wealth Condensation

    CERN Document Server

    Braun, D

    2006-01-01

    We analyze wealth condensation for a wide class of stochastic economy models on the basis of the economic analog of thermodynamic potentials, termed transfer potentials. The economy model is based on three common transfers modes of wealth: random transfer, profit proportional to wealth and motivation of poor agents to work harder. The economies never reach steady state. Wealth condensation is the result of stochastic tunneling through a metastable transfer potential. In accordance with reality, both wealth and income distribution transiently show Pareto tails for high income subjects. For metastable transfer potentials, exponential wealth condensation is a robust feature. For example with 10 % annual profit 1% of the population owns 50 % of the wealth after 50 years. The time to reach such a strong wealth condensation is a hyperbolic function of the annual profit rate.

  15. Solar engineering - a condensed course

    Energy Technology Data Exchange (ETDEWEB)

    Broman, Lars

    2011-11-15

    The document represents the material covered in a condensed two-week course focusing on the most important thermal and PV solar energy engineering topics, while also providing some theoretical background.

  16. Nuclear fusion inside condense matters

    Institute of Scientific and Technical Information of China (English)

    HE Jing-tang

    2007-01-01

    This article describes in detail the nuclear fusion inside condense matters--the Fleischmann-Pons effect, the reproducibility of cold fusions, self-consistentcy of cold fusions and the possible applications.

  17. Cationic Nitrogen Doped Helical Nanographenes.

    Science.gov (United States)

    Xu, Kun; Feng, Xinliang; Berger, Reinhard; Popov, Alexey A; Weigand, Jan J; Vincon, Ilka; Machata, Peter; Hennersdorf, Felix; Zhou, Youjia; Fu, Yubin

    2017-09-13

    Herein, we report on the synthesis of a series of novel cationic nitrogen doped nanographenes (CNDN) by rhodium catalyzed annulation reactions. This powerful method allows for the synthesis of cationic nanographenes with non-planar, axial chiral geometries. Single-crystal X-ray analysis reveals helical and cove-edged structures. Compared to their all-carbon analogues, the CNDN exhibit energetically lower lying frontier orbitals with a reduced optical energy gap and an electron accepting behavior. All derivatives show quasi reversible reductions in cyclic voltammetry. Depending on the number of nitrogen dopant, in situ spectroelectrochemistry proves the formation of neutral radicals (one nitrogen dopant) or radical cations (two nitrogen dopants) upon reduction. The developed synthetic protocol paves the way for the design and synthesis of expanded nanographenes or even graphene nanoribbons containing cationic nitrogen doping. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Cationic Lipid-Formulated DNA Vaccine against Hepatitis B Virus : Immunogenicity of MIDGE-Th1 Vectors Encoding Small and Large Surface Antigen in Comparison to a Licensed Protein Vaccine

    NARCIS (Netherlands)

    Endmann, Anne; Klunder, Katharina; Kapp, Kerstin; Riede, Oliver; Oswald, Detlef; Talman, Eduard G.; Schroff, Matthias; Kleuss, Christiane; Ruiters, Marcel H. J.; Juhls, Christiane

    2014-01-01

    Currently marketed vaccines against hepatitis B virus (HBV) based on the small (S) hepatitis B surface antigen (HBsAg) fail to induce a protective immune response in about 10% of vaccinees. DNA vaccination and the inclusion of PreS1 and PreS2 domains of HBsAg have been reported to represent feasible

  19. Asymmetric cation-binding catalysis

    DEFF Research Database (Denmark)

    Oliveira, Maria Teresa; Lee, Jiwoong

    2017-01-01

    and KCN, are selectively bound to the catalyst, providing exceptionally high enantioselectivities for kinetic resolutions, elimination reactions (fluoride base), and Strecker synthesis (cyanide nucleophile). Asymmetric cation-binding catalysis was recently expanded to silicon-based reagents, enabling...... solvents, thus increasing their applicability in synthesis. The expansion of this concept to chiral polyethers led to the emergence of asymmetric cation-binding catalysis, where chiral counter anions are generated from metal salts, particularly using BINOL-based polyethers. Alkali metal salts, namely KF...

  20. Condenser Optimization in Steam Power Plant

    Institute of Scientific and Technical Information of China (English)

    Sukru Bekdemir; Recep Ozturk; Zehra Yumurtac

    2003-01-01

    In this paper the effects of the condenser design parameters (such as turbine inlet condition, turbine power and condenser pressure) on heat transfer area, cooling water flow-rate, condenser cost and specific energy generation cost are studied for surface type condenser.The results are given in the text and also shown as diagrams.

  1. Rapid Drop Dynamics During Superhydrophobic Condensation

    Science.gov (United States)

    Zhang, Xiaodong; Boreyko, Jonathan; Chen, Chuan-Hua

    2008-11-01

    Rapid drop motion is observed on superhydrophobic surfaces during condensation; condensate drops with diameter of order 10 μm can move at above 100G and 0.1 m/s. When water vapor condenses on a horizontal superhydrophobic surface, condensate drops move in a seemingly random direction. The observed motion is attributed to the energy released through coalescence of neighboring condensate drops. A scaling analysis captured the initial acceleration and terminal velocity. Our work is a step forward in understanding the dynamics of superhydrophobic condensation occurring in both natural water-repellant plants and engineered dropwise condensers.

  2. Research progress of control of condensate depression for condenser

    Science.gov (United States)

    Liu, Ying; Liang, Run; Li, Fengyu

    2017-08-01

    It is introduced that significance and structure of the condensate depression control system. In accordance with controller devised procedure, we analyze and elaborate how to construct the lumped parameter and dynamic mathematical model which possesses distinct physics significance. Neural network model being called black-box model is also introduced. We analyze and contrast the control technique of condensate depression as conventional PI control, fuzzy PI control and fuzzy control. It is indicated that if the controller of condensate depression were devised inappropriate, while the steam discharged of turbine varying by a large margin, would result in the rotation rate of cooling water circulating pump accelerating at a great lick even to trigger the galloping danger which is less impressive for the units operating safely.

  3. Scrutinizing the pion condensed phase

    CERN Document Server

    Carignano, Stefano; Mammarella, Andrea; Mannarelli, Massimo; Pagliaroli, Giulia

    2016-01-01

    When the isospin chemical potential exceeds the pion mass, charged pions condense in the zero-momentum state forming a superfluid. Chiral perturbation theory provides a very powerful tool for studying this phase. However, the formalism that is usually employed in this context does not clarify various aspects of the condensation mechanism and makes the identification of the soft modes problematic. We re-examine the pion condensed phase using different approaches within the chiral perturbation theory framework. As a first step, we perform a low-density expansion of the chiral Lagrangian valid in the normal phase and close to the onset of the Bose-Einstein condensation. We obtain an effective theory that can be mapped to a Gross-Pitaevskii Lagrangian in which, remarkably, all the coefficients depend on the isospin chemical potential. The low-density expansion becomes unreliable deep in the pion condensed phase. For this reason, we develop an alternative field expansion deriving a low-energy Lagrangian analog to ...

  4. Polariton condensates at room temperature

    Science.gov (United States)

    Guillet, Thierry; Brimont, Christelle

    2016-10-01

    We review the recent developments of the polariton physics in microcavities featuring the exciton-photon strong coupling at room temperature, and leading to the achievement of room-temperature polariton condensates. Such cavities embed active layers with robust excitons that present a large binding energy and a large oscillator strength, i.e. wide bandgap inorganic or organic semiconductors, or organic molecules. These various systems are compared, in terms of figures of merit and of common features related to their strong oscillator strength. The various demonstrations of polariton laser are compared, as well as their condensation phase diagrams. The room-temperature operation indeed allows a detailed investigation of the thermodynamic and out-of-equilibrium regimes of the condensation process. The crucial role of the spatial dynamics of the condensate formation is discussed, as well as the debated issue of the mechanism of stimulated relaxation from the reservoir to the condensate under non-resonant excitation. Finally the prospects of polariton devices are presented.

  5. Persistent currents in ferromagnetic condensates

    Science.gov (United States)

    Lamacraft, Austen

    2017-06-01

    Persistent currents in Bose condensates with a scalar order parameter are stabilized by the topology of the order parameter manifold. In condensates with multicomponent order parameters it is topologically possible for supercurrents to "unwind" without leaving the manifold. We study the energetics of this process in the case of ferromagnetic condensates using a long wavelength energy functional that includes both the superfluid and spin stiffnesses. Exploiting analogies to an elastic rod and rigid body motion, we show that the current carrying state in a 1D ring geometry transitions between a spin helix in the energy minima and a solitonlike configuration at the maxima. The relevance to recent experiments in ultracold atoms is briefly discussed.

  6. Scrutinizing the pion condensed phase

    Energy Technology Data Exchange (ETDEWEB)

    Carignano, Stefano; Mammarella, Andrea; Mannarelli, Massimo [INFN, Laboratori Nazionali del Gran Sasso, Assergi (Italy); Lepori, Luca [Universita di Padova, Dipartimento di Fisica e Astronomia, Padova (Italy); Universita dell' Aquila, Dipartimento di Scienze Fisiche e Chimiche, Coppito-L' Aquila (Italy); Pagliaroli, Giulia [INFN, Laboratori Nazionali del Gran Sasso, Assergi (Italy); Gran Sasso Science Institute, L' Aquila (Italy)

    2017-02-15

    When the isospin chemical potential exceeds the pion mass, charged pions condense in the zero-momentum state forming a superfluid. Chiral perturbation theory provides a very powerful tool for studying this phase. However, the formalism that is usually employed in this context does not clarify various aspects of the condensation mechanism and makes the identification of the soft modes problematic. We re-examine the pion condensed phase using different approaches within the chiral perturbation theory framework. As a first step, we perform a low-density expansion of the chiral Lagrangian valid close to the onset of the Bose-Einstein condensation. We obtain an effective theory that can be mapped to a Gross-Pitaevskii Lagrangian in which, remarkably, all the coefficients depend on the isospin chemical potential. The low-density expansion becomes unreliable deep in the pion condensed phase. For this reason, we develop an alternative field expansion deriving a low-energy Lagrangian analog to that of quantum magnets. By integrating out the ''radial'' fluctuations we obtain a soft Lagrangian in terms of the Nambu-Goldstone bosons arising from the breaking of the pion number symmetry. Finally, we test the robustness of the second-order transition between the normal and the pion condensed phase when next-to-leading-order chiral corrections are included. We determine the range of parameters for turning the second-order phase transition into a first-order one, finding that the currently accepted values of these corrections are unlikely to change the order of the phase transition. (orig.)

  7. On the onset of surface condensation: formation and transition mechanisms of condensation mode

    Science.gov (United States)

    Sheng, Qiang; Sun, Jie; Wang, Qian; Wang, Wen; Wang, Hua Sheng

    2016-08-01

    Molecular dynamics simulations have been carried out to investigate the onset of surface condensation. On surfaces with different wettability, we snapshot different condensation modes (no-condensation, dropwise condensation and filmwise condensation) and quantitatively analyze their characteristics by temporal profiles of surface clusters. Two different types of formation of nanoscale droplets are identified, i.e. the formations with and without film-like condensate. We exhibit the effect of surface tensions on the formations of nanoscale droplets and film. We reveal the formation mechanisms of different condensation modes at nanoscale based on our simulation results and classical nucleation theory, which supplements the ‘classical hypotheses’ of the onset of dropwise condensation. We also reveal the transition mechanism between different condensation modes based on the competition between surface tensions and reveal that dropwise condensation represents the transition states from no-condensation to filmwise condensation.

  8. Turbulent mixing condensation nucleus counter

    Science.gov (United States)

    Mavliev, Rashid

    The construction and operating principles of the Turbulent Mixing Condensation Nucleus Counter (TM CNC) are described. Estimations based on the semiempirical theory of turbulent jets and the classical theory of nucleation and growth show the possibility of detecting particles as small as 2.5 nm without the interference of homogeneous nucleation. This conclusion was confirmed experimentally during the International Workshop on Intercomparison of Condensation Nuclei and Aerosol Particle Counters (Vienna, Austria). Number concentration, measured by the Turbulent Mixing CNC and other participating instruments, is found to be essentially equal.

  9. Condensed Matter Physics - Biology Resonance

    Science.gov (United States)

    Baskaran, G.

    The field of condensed matter physics had its genesis this century and it has had a remarkable evolution. A closer look at its growth reveals a hidden aim in the collective consciousness of the field - a part of the development this century is a kind of warm up exercise to understand the nature of living condensed matter, namely the field of biology, by a growing new breed of scientists in the coming century. Through some examples the vitality of this interaction will be pointed out.

  10. Evaporative Condensers in Comfortable Air Conditioning System

    Institute of Scientific and Technical Information of China (English)

    YIN Ying-de; ZHU Dong-sheng; DU Gui-mei; LI Yuan-xi; SUN He-jing; LIU Qing-ming

    2009-01-01

    The operating theory of an evaporative condenser was expatiated.The difference between an e-vaporative condensing refrigeration system and a general refrigeration system was analyzed.Compared with the air-cooled and the water-cooled,the virtues of energy-conservation and water-conservation of evaporative con-densers were analyzed.Some questions existing in the application of evaporative condensers were pointed out,the corresponding solving methods were analyzed accordingly,and the development trend of evaporative con-densing technique in mechanical refrigeration system field and the applied foreground of evaporative condensers in comfortable air conditioning were prospected.

  11. Condensational theory of stationary tornadoes

    CERN Document Server

    Makarieva, Anastassia M; Nefiodov, Andrei V; 10.1016/j.physleta.2011.04.023

    2012-01-01

    Using the Bernoulli integral for air streamline with condensing water vapor a stationary axisymmetric tornado circulation is described. The obtained profiles of vertical, radial and tangential velocities are in agreement with observations for the Mulhall tornado, world's largest on record and longest-lived among the three tornadoes for which 3D velocity data are available. Maximum possible vortex velocities are estimated.

  12. Approaching Bose-Einstein Condensation

    Science.gov (United States)

    Ferrari, Loris

    2011-01-01

    Bose-Einstein condensation (BEC) is discussed at the level of an advanced course of statistical thermodynamics, clarifying some formal and physical aspects that are usually not covered by the standard pedagogical literature. The non-conventional approach adopted starts by showing that the continuum limit, in certain cases, cancels out the crucial…

  13. Magnetofermionic condensate in two dimensions

    Science.gov (United States)

    Kulik, L. V.; Zhuravlev, A. S.; Dickmann, S.; Gorbunov, A. V.; Timofeev, V. B.; Kukushkin, I. V.; Schmult, S.

    2016-11-01

    Coherent condensate states of particles obeying either Bose or Fermi statistics are in the focus of interest in modern physics. Here we report on condensation of collective excitations with Bose statistics, cyclotron magnetoexcitons, in a high-mobility two-dimensional electron system in a magnetic field. At low temperatures, the dense non-equilibrium ensemble of long-lived triplet magnetoexcitons exhibits both a drastic reduction in the viscosity and a steep enhancement in the response to the external electromagnetic field. The observed effects are related to formation of a super-absorbing state interacting coherently with the electromagnetic field. Simultaneously, the electrons below the Fermi level form a super-emitting state. The effects are explicable from the viewpoint of a coherent condensate phase in a non-equilibrium system of two-dimensional fermions with a fully quantized energy spectrum. The condensation occurs in the space of vectors of magnetic translations, a property providing a completely new landscape for future physical investigations.

  14. Rotary condenser for SC2

    CERN Multimedia

    1975-01-01

    During 1975 the SC2 performance was improved among other things by redesigning some of the elements of the ROTCO (Annual Report 1975, p. 55). The photo shows an interior wiew of the housing of the rotary condenser and of the sixteen sets of shaped stator blades.

  15. Research progress in cation-π interactions

    Institute of Scientific and Technical Information of China (English)

    CHENG JiaGao; LUO XiaoMin; YAN XiuHua; LI Zhong; TANG Yun; JIANG HuaLiang; ZHU WeiLiang

    2008-01-01

    Cation-π interaction is a potent intermolecular interaction between a cation and an aromatic system, which has been viewed as a new kind of binding force, as being compared with the classical interac-tions (e.g. hydrogen bonding, electrostatic and hydrophobic interactions). Cation-π interactions have been observed in a wide range of biological contexts. In this paper, we present an overview of the typi-cal cation-π interactions in biological systems, the experimental and theoretical investigations on cation-π interactions, as well as the research results on cation-π interactions in our group.

  16. Research progress in cation-π interactions

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Cation-π interaction is a potent intermolecular interaction between a cation and an aromatic system,which has been viewed as a new kind of binding force,as being compared with the classical interactions(e.g. hydrogen bonding,electrostatic and hydrophobic interactions). Cation-π interactions have been observed in a wide range of biological contexts. In this paper,we present an overview of the typical cation-π interactions in biological systems,the experimental and theoretical investigations on cation-π interactions,as well as the research results on cation-π interactions in our group.

  17. 涂覆承载质粒DNA水凝胶的覆膜血管内支架置入主动脉局部基因转染的实验研究%Gene delivery of plasmid DNA to rabbit aorta by genetic engineering of cationized gelatin hydrogel coated partially covered endovascular stent graft

    Institute of Scientific and Technical Information of China (English)

    钟红珊; 徐克; 刘屹; 松井 修

    2008-01-01

    Objective To genetically engineer endovascular stent grafts that facilitate plasmid DNA delivery and offer the promise ofcular delivery system of therapeutic materials. Methods Partially covered polyester stent-grafts coated with cationized gelatin hydrogels (CGH) containing pCAGGS-LacZ or pEGFP were implanted in the descending aorta of 8 rabbits, which had neointima due to balloon injury four weeks ago. The aorta with stent-graft containing pCAGGS-LacZ and the one containing pEGFP was taken as negative control for each other. Expression of the plasmid-encoded marker genes, (3-galactosidase and enhanced green fluorescence protein (EGFP) were evaluated at 3 days after implantations by X-Gal staining and RT-PCR or fluorescence microscopy. Results Local plasmid DNA transfer was confined to the vessel wall at the site of stent-graft implantation, especially where the graft was compressed firmly to the vessel by metal struts. Plasmid DNA was not detected in vessel segments immediately proximal or distal to the stent graft and dissemination of plasmid DNA to brain, heart, lung, liver or kidney was not observed. The (3-galactosidase-expressed cells were identified as endothelial cells, and smooth muscle cells by pathological analysis. Fluorescence microscopy identified the EGFP expression which demonstrated the transgene delivery of plasmid DNA and it was not related to the plasmid-encoded marker genes. No signal was detected in the aorta of the rabbits that received cationized gelatin hydrogels coated stent-grafts without plasmid DNA. Conclusions Cationized gelatin hydrogels coated partially covered stent grafts provide a new access for transgene delivery to the cells of aortic wall.%目的 用部分覆膜血管内支架涂覆阳离子胶原水凝胶(CGH)承载质粒DNA实现主动脉局部的基因转染,为核酸等大分子治疗物质经血管导入提供理论依据.方法 将CGH涂覆于部分覆膜血管内支架的覆膜织物上,以CGH涂层分别承载2种质

  18. Contribution of hydrophobic/hydrophilic modification on cationic chains of poly(ε-caprolactone)-graft-poly(dimethylamino ethylmethacrylate) amphiphilic co-polymer in gene delivery.

    Science.gov (United States)

    Han, Shangcong; Wan, Haiying; Lin, Daoshu; Guo, Shutao; Dong, Hongxu; Zhang, Jianhua; Deng, Liandong; Liu, Ruming; Tang, Hua; Dong, Anjie

    2014-02-01

    Nanoparticles (NPs) assembled from amphiphilic polycations have been certified as potential carriers for gene delivery. Structural modification of polycation moieties may be an efficient route to further enhance gene delivery efficiency. In this study two electroneutral monomers with different hydrophobicities, 2-hydroxyethyl methacrylate (HEMA) and 2-hydroxyethyl acrylate (HEA), were incorporated into the cationic poly(dimethylamino ethyl methacrylate) (PDMAEMA) side-chains of amphiphilic poly(ε-caprolactone)-graft-poly(dimethylamino ethylmethacrylate) (PCD) by random co-polymerization, to obtain poly(ε-caprolactone)-graft-poly(dimethylamino ethyl methacrylate-co-2-hydroxyethyl methacrylate) (PCD-HEMA) and poly(ε-caprolactone)-graft-poly(dimethylamino ethyl methacrylate-co-2-hydroxyethyl acrylate) (PCD-HEA). Minimal HEA or HEMA moieties in PDMAEMA do not lead to statistically significant changes in particle size, zeta potential, DNA condensation properties and buffering capacity of the naked NPs. However, the incorporation of HEMA and HEA lead to reductions and increases, respectively, in the surface hydrophilicity of the naked NPs and NPs/DNA complexes, which was confirmed by water contact angle assay. These simple modifications of PDMAEMA with HEA and HEMA moieties significantly affect the gene transfection efficiency on HeLa cells in vitro: PCD-HEMA NP/DNA complexes show a much higher transfection efficiency than PCD NPs/DNA complexes, while PCD-HEA NPs/DNA complexes show a lower transfection efficiency than PCD NP/DNA complexes. Fluorescence activated cell sorter and confocal laser scanning microscope results indicate that the incorporation of hydrophobic HEMA moieties facilitates an enhancement in both cellular uptake and endosomal/lysosomal escape, leading to a higher transfection efficiency. Moreover, the process of endosomal/lysosomal escape confirmed in our research that PCD and its derivatives do not just rely on the proton sponge mechanism, but also

  19. Molecular Effects on Evaporation and Condensation

    OpenAIRE

    Meland, Roar

    2002-01-01

    In this thesis the evaporation from and condensation on a plane liquid surface have been studied by analysis and molecular dynamics simulations. The effect of the condensation coefficient on the inverted temperature gradient for a two-surface evaporation-condensation geometry is investigated by the moment method. The influence of the molecular exchange phenomenon on the gas-kinetic treatment of evaporation and condensation is shown to be neglible under certain assumptions. Methods to simulate...

  20. The antimicrobial polymer PHMB enters cells and selectively condenses bacterial chromosomes

    DEFF Research Database (Denmark)

    Chindera, Kantaraja; Mahato, Manohar; Sharma, Ashwani Kumar

    2016-01-01

    To combat infection and antimicrobial resistance, it is helpful to elucidate drug mechanism(s) of action. Here we examined how the widely used antimicrobial polyhexamethylene biguanide (PHMB) kills bacteria selectively over host cells. Contrary to the accepted model of microbial membrane disruption...... by PHMB, we observed cell entry into a range of bacterial species, and treated bacteria displayed cell division arrest and chromosome condensation, suggesting DNA binding as an alternative antimicrobial mechanism. A DNA-level mechanism was confirmed by observations that PHMB formed nanoparticles when...... to bacterial and mammalian cellular DNA and selectively binds and condenses bacterial chromosomes. Because acquired resistance to PHMB has not been reported, selective chromosome condensation provides an unanticipated paradigm for antimicrobial action that may not succumb to resistance....

  1. Tripodal Receptors for Cation and Anion Sensors

    NARCIS (Netherlands)

    Kuswandi, Bambang; Nuriman,; Verboom, Willem; Reinhoudt, David N.

    2006-01-01

    This review discusses different types of artificial tripodal receptors for the selectiverecognition and sensing of cations and anions. Examples on the relationship between structure andselectivity towards cations and anions are described. Furthermore, their applications as potentiometricion sensing

  2. Structural Isomerization of the Gas Phase 2-NORBORNYL Cation Revealed with Infrared Spectroscopy and Computational Chemistry

    Science.gov (United States)

    Mauney, Daniel; Mosley, Jonathan; Duncan, Michael A.

    2014-06-01

    The non-classical structure of the 2-norborny cation (C_7H11+) which was at the center of "the most heated chemical controversy of our time" has been observed in the condensed phase and recently using X-ray crystallography. However, no gas phase vibrational spectrum has been collected. The C_7H11+ cation is produced via H_3+ protonation of norbornene by pulsed discharge in a supersonic expansion of H_2/Ar. Ions are mass-selected and probed using infrared photodissociation spectroscopy. Due to high exothermicity, protonation via H_3+ leads to a structural isomerization to the global minimum structure 1,3-dimethylcyclopentenyl (DMCP+). Experiments are currently being conducted to find softer protonation techniques that could lead to the authentic 2-norbornyl cation. Schleyer,P.v.R. et. al.; Stable Carbocation Chemistry, John Wiley & Sons,Inc.; New York, 1997, Chapter 2

  3. Heavy metal cations permeate the TRPV6 epithelial cation channel.

    Science.gov (United States)

    Kovacs, Gergely; Danko, Tamas; Bergeron, Marc J; Balazs, Bernadett; Suzuki, Yoshiro; Zsembery, Akos; Hediger, Matthias A

    2011-01-01

    TRPV6 belongs to the vanilloid family of the transient receptor potential channel (TRP) superfamily. This calcium-selective channel is highly expressed in the duodenum and the placenta, being responsible for calcium absorption in the body and fetus. Previous observations have suggested that TRPV6 is not only permeable to calcium but also to other divalent cations in epithelial tissues. In this study, we tested whether TRPV6 is indeed also permeable to cations such as zinc and cadmium. We found that the basal intracellular calcium concentration was higher in HEK293 cells transfected with hTRPV6 than in non-transfected cells, and that this difference almost disappeared in nominally calcium-free solution. Live cell imaging experiments with Fura-2 and NewPort Green DCF showed that overexpression of human TRPV6 increased the permeability for Ca(2+), Ba(2+), Sr(2+), Mn(2+), Zn(2+), Cd(2+), and interestingly also for La(3+) and Gd(3+). These results were confirmed using the patch clamp technique. (45)Ca uptake experiments showed that cadmium, lanthanum and gadolinium were also highly efficient inhibitors of TRPV6-mediated calcium influx at higher micromolar concentrations. Our results suggest that TRPV6 is not only involved in calcium transport but also in the transport of other divalent cations, including heavy metal ions, which may have toxicological implications.

  4. 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

  5. Antiviral effect of cationic compounds on bacteriophages

    Directory of Open Access Journals (Sweden)

    Mai Huong eChatain-Ly

    2013-03-01

    Full Text Available The antiviral activity of several cationic compounds - cetytrimethylammonium (CTAB, chitosan, nisin and lysozyme - was investigated on the bacteriophage c2 (DNA head and non-contractile tail infecting Lactococcus strains and the bacteriophage MS2 (F-specific RNA infecting E.coli. Firstly, these activities were evaluated in a phosphate buffer pH 7- 10 mM. The CTAB had a virucidal effect on the Lactococcus bacteriophages, but not on the MS2. After 1 min of contact with 0.125 mM CTAB, the c2 population was reduced from 6 log(pfu/mL to 1,5 log(pfu/mL and completely deactivated at 1 mM. On the contrary, chitosan inhibited the MS2 more than it did the bacteriophages c2. No antiviral effect was observed for the nisin or the lysozyme on bacteriophages after 1 min of treatment. A 1 and 2.5 log reduction was respectively observed for nisin and lysozyme when the treatment time increased (5 or 10 min. These results showed that the antiviral effect depended both on the virus and structure of the antimicrobial compounds. The antiviral activity of these compounds was also evaluated in different physico-chemical conditions and in complex matrices. The antiviral activity of CTAB was impaired in acid pH and with an increase of the ionic strength. These results might be explained by the electrostatic interactions between cationic compounds and negatively charged particles such as bacteriophages or other compounds in a matrix. Milk proved to be protective suggesting the components of food could interfere with antimicrobial compounds.

  6. Metal Cations in G-Quadruplex Folding and Stability

    Science.gov (United States)

    Bhattacharyya, Debmalya; Mirihana Arachchilage, Gayan; Basu, Soumitra

    2016-01-01

    This review is focused on the structural and physicochemical aspects of metal cation coordination to G-Quadruplexes (GQ) and their effects on GQ stability and conformation. G-quadruplex structures are non-canonical secondary structures formed by both DNA and RNA. G-quadruplexes regulate a wide range of important biochemical processes. Besides the sequence requirements, the coordination of monovalent cations in the GQ is essential for its formation and determines the stability and polymorphism of GQ structures. The nature, location, and dynamics of the cation coordination and their impact on the overall GQ stability are dependent on several factors such as the ionic radii, hydration energy, and the bonding strength to the O6 of guanines. The intracellular monovalent cation concentration and the localized ion concentrations determine the formation of GQs and can potentially dictate their regulatory roles. A wide range of biochemical and biophysical studies on an array of GQ enabling sequences have generated at a minimum the knowledge base that allows us to often predict the stability of GQs in the presence of the physiologically relevant metal ions, however, prediction of conformation of such GQs is still out of the realm. PMID:27668212

  7. Cation ordering and superstructures in natural layered double hydroxides.

    Science.gov (United States)

    Krivovichev, Sergey V; Yakovenchuk, Victor N; Zolotarev, Andrey A; Ivanyuk, Gregory N; Pakhomovsky, Yakov A

    2010-01-01

    Layered double hydroxides (LDHs) constitute an important group of materials with many applications ranging from catalysis and absorption to carriers for drug delivery, DNA intercalation and carbon dioxide sequestration. The structures of LDHs are based upon double brucite-like hydroxide layers [M(2+)(n)M(3+)(m)(OH)(2(m+n)](m+), where M(2+) = Mg(2+), Fe(2+), Mn(2+), Zn(2+), etc.; M(3+) = Al(3+), Fe(3+), Cr(3+), Mn(3+), etc. Structural features of LDHs such as cation ordering, charge distribution and polytypism have an immediate influence upon their properties. However, all the structural studies on synthetic LDHs deal with powder samples that prevent elucidation of such fine details of structure architecture as formation of superstructures due to cation ordering. In contrast to synthetic materials, natural LDHs are known to form single crystals accessible to single-crystal X-ray diffraction analysis, which provides a unique possibility to investigate 3D cation ordering in LDHs that results in formation of complex superstructures, where 2D cation order is combined with a specific order of layer stacking (polytypism). Therefore LDH minerals provide an indispensable source of structural information for modeling of structures and processes happening in LDHs at the molecular and nanoscale levels.

  8. Metal Cations in G-Quadruplex Folding and Stability

    Science.gov (United States)

    Bhattacharyya, Debmalya; Mirihana Arachchilage, Gayan; Basu, Soumitra

    2016-09-01

    This review is focused on the structural and physico-chemical aspects of metal cation coordination to G-Quadruplexes (GQ) and their effects on GQ stability and conformation. G-Quadruplex structures are non-canonical secondary structures formed by both DNA and RNA. G-quadruplexes regulate a wide range of important biochemical processes. Besides the sequence requirements, the coordination of monovalent cations in the GQ is essential for its formation and determines the stability and polymorphism of GQ structures. The nature, location and dynamics of the cation coordination and their impact on the overall GQ stability are dependent on several factors such as the ionic radii, hydration energy and the bonding strength to the O6 of guanines. The intracellular monovalent cation concentration and the localized ion concentrations determine the formation of GQs and can potentially dictate their regulatory roles. A wide range of biochemical and biophysical studies on an array of GQ enabling sequences have generated at a minimum the knowledge base that allows us to often predict the stability of GQs in presence of the physiologically relevant metal ions, however, prediction of conformation of such GQs is still out of the realm.

  9. Metal Cations in G-Quadruplex Folding and Stability

    Directory of Open Access Journals (Sweden)

    Debmalya Bhattacharyya

    2016-09-01

    Full Text Available This review is focused on the structural and physico-chemical aspects of metal cation coordination to G-Quadruplexes (GQ and their effects on GQ stability and conformation. G-Quadruplex structures are non-canonical secondary structures formed by both DNA and RNA. G-quadruplexes regulate a wide range of important biochemical processes. Besides the sequence requirements, the coordination of monovalent cations in the GQ is essential for its formation and determines the stability and polymorphism of GQ structures. The nature, location and dynamics of the cation coordination and their impact on the overall GQ stability are dependent on several factors such as the ionic radii, hydration energy and the bonding strength to the O6 of guanines. The intracellular monovalent cation concentration and the localized ion concentrations determine the formation of GQs and can potentially dictate their regulatory roles. A wide range of biochemical and biophysical studies on an array of GQ enabling sequences have generated at a minimum the knowledge base that allows us to often predict the stability of GQs in presence of the physiologically relevant metal ions, however, prediction of conformation of such GQs is still out of the realm.

  10. Fundamentals of condensed matter physics

    CERN Document Server

    Cohen, Marvin L

    2016-01-01

    Based on an established course and covering the fundamentals, central areas, and contemporary topics of this diverse field, Fundamentals of Condensed Matter Physics is a much-needed textbook for graduate students. The book begins with an introduction to the modern conceptual models of a solid from the points of view of interacting atoms and elementary excitations. It then provides students with a thorough grounding in electronic structure as a starting point to understand many properties of condensed matter systems - electronic, structural, vibrational, thermal, optical, transport, magnetic and superconductivity - and methods to calculate them. Taking readers through the concepts and techniques, the text gives both theoretically and experimentally inclined students the knowledge needed for research and teaching careers in this field. It features 200 illustrations, 40 worked examples and 150 homework problems for students to test their understanding. Solutions to the problems for instructors are available at w...

  11. Polymer Bose–Einstein condensates

    Energy Technology Data Exchange (ETDEWEB)

    Castellanos, E., E-mail: ecastellanos@fis.cinvestav.mx [Departamento de Física, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, A.P. 14-740, México D.F. 07000 (Mexico); Chacón-Acosta, G., E-mail: gchacon@correo.cua.uam.mx [Departamento de Matemáticas Aplicadas y Sistemas, Universidad Autónoma Metropolitana-Cuajimalpa, Artificios 40, México D.F. 01120 (Mexico)

    2013-05-13

    In this work we analyze a non-interacting one-dimensional polymer Bose–Einstein condensate in a harmonic trap within the semiclassical approximation. We use an effective Hamiltonian coming from the polymer quantization that arises in loop quantum gravity. We calculate the number of particles in order to obtain the critical temperature. The Bose–Einstein functions are replaced by series, whose high order terms are related to powers of the polymer length. It is shown that the condensation temperature presents a shift respect to the standard case, for small values of the polymer scale. In typical experimental conditions, it is possible to establish a bound for λ{sup 2} up to ≲10{sup −16} m{sup 2}. To improve this bound we should decrease the frequency of the trap and also decrease the number of particles.

  12. Atomistic modeling of dropwise condensation

    Science.gov (United States)

    Sikarwar, B. S.; Singh, P. L.; Muralidhar, K.; Khandekar, S.

    2016-05-01

    The basic aim of the atomistic modeling of condensation of water is to determine the size of the stable cluster and connect phenomena occurring at atomic scale to the macroscale. In this paper, a population balance model is described in terms of the rate equations to obtain the number density distribution of the resulting clusters. The residence time is taken to be large enough so that sufficient time is available for all the adatoms existing in vapor-phase to loose their latent heat and get condensed. The simulation assumes clusters of a given size to be formed from clusters of smaller sizes, but not by the disintegration of the larger clusters. The largest stable cluster size in the number density distribution is taken to be representative of the minimum drop radius formed in a dropwise condensation process. A numerical confirmation of this result against predictions based on a thermodynamic model has been obtained. Results show that the number density distribution is sensitive to the surface diffusion coefficient and the rate of vapor flux impinging on the substrate. The minimum drop radius increases with the diffusion coefficient and the impinging vapor flux; however, the dependence is weak. The minimum drop radius predicted from thermodynamic considerations matches the prediction of the cluster model, though the former does not take into account the effect of the surface properties on the nucleation phenomena. For a chemically passive surface, the diffusion coefficient and the residence time are dependent on the surface texture via the coefficient of friction. Thus, physical texturing provides a means of changing, within limits, the minimum drop radius. The study reveals that surface texturing at the scale of the minimum drop radius does not provide controllability of the macro-scale dropwise condensation at large timescales when a dynamic steady-state is reached.

  13. Advances in condensed matter optics

    CERN Document Server

    Chen, Liangyao; Jiang, Xunya; Jin, Kuijuan; Liu, Hui; Zhao, Haibin

    2015-01-01

    This book describes some of the more recent progresses and developmentsin the study of condensed matter optics in both theoretic and experimental fields.It will help readers, especially graduate students and scientists who are studying and working in the nano-photonic field, to understand more deeply the characteristics of light waves propagated in nano-structure-based materials with potential applications in the future.

  14. Radiative corrections to Bose condensation

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, A. (Academia de Ciencias de Cuba, La Habana. Inst. de Matematica, Cibernetica y Computacion)

    1985-04-01

    The Bose condensation of the scalar field in a theory behaving in the Coleman-Weinberg mode is considered. The effective potential of the model is computed within the semiclassical approximation in a dimensional regularization scheme. Radiative corrections are shown to introduce certain ..mu..-dependent ultraviolet divergences in the effective potential coming from the Many-Particle theory. The weight of radiative corrections in the dynamics of the system is strongly modified by the charge density.

  15. Theory of laminar film condensation

    CERN Document Server

    Fujii, Tetsu

    1991-01-01

    Since the petroleum crisis in the 1970s, a lot of effort to save energy was made in industry, and remarkable achievements have been made. In the research and development concerning thermal energy, however, it was clar­ ified that one of the most important problems was manufacturing con­ densing systems with smaller size and higher performance. To solve this problem we need a method which synthesizes selections_ of the type of con­ denser, cooling tube and its arrangement, assessment of fouling on the cooling surfaces, consideration of transient characteristics of a condenser, etc. The majority of effort, however, has been to devise a surface element which enhances the heat transfer coefficient in condensation of a single or multicomponent vapor. Condensation phenomena are complexly affected by a lot of physical property values, and accordingly the results of theo­ retical research are expressed with several dimensionless parameters. On the other hand, the experimental research is limited to those with som...

  16. Condensation on Slippery Asymmetric Bumps

    Science.gov (United States)

    Park, Kyoo-Chul; Kim, Philseok; Aizenberg, Joanna

    2016-11-01

    Controlling dropwise condensation by designing surfaces that enable droplets to grow rapidly and be shed as quickly as possible is fundamental to water harvesting systems, thermal power generation, distillation towers, etc. However, cutting-edge approaches based on micro/nanoscale textures suffer from intrinsic trade-offs that make it difficult to optimize both growth and transport at once. Here we present a conceptually different design approach based on principles derived from Namib desert beetles, cacti, and pitcher plants that synergistically couples both aspects of condensation and outperforms other synthetic surfaces. Inspired by an unconventional interpretation of the role of the beetle's bump geometry in promoting condensation, we show how to maximize vapor diffusion flux at the apex of convex millimetric bumps by optimizing curvature and shape. Integrating this apex geometry with a widening slope analogous to cactus spines couples rapid drop growth with fast directional transport, by creating a free energy profile that drives the drop down the slope. This coupling is further enhanced by a slippery, pitcher plant-inspired coating that facilitates feedback between coalescence-driven growth and capillary-driven motion. We further observe an unprecedented six-fold higher exponent in growth rate and much faster shedding time compared to other surfaces. We envision that our fundamental understanding and rational design strategy can be applied to a wide range of phase change applications.

  17. Condensate from a two-stage gasifier

    DEFF Research Database (Denmark)

    Bentzen, Jens Dall; Henriksen, Ulrik Birk; Hindsgaul, Claus

    2000-01-01

    that the organic compounds and the inhibition effect are very low even before treatment with activated carbon. The moderate inhibition effect relates to a high content of ammonia in the condensate. The nitrifiers become tolerant to the condensate after a few weeks of exposure. The level of organic compounds......Condensate, produced when gas from downdraft biomass gasifier is cooled, contains organic compounds that inhibit nitrifiers. Treatment with activated carbon removes most of the organics and makes the condensate far less inhibitory. The condensate from an optimised two-stage gasifier is so clean...

  18. Quality factors to consider in condensate selection

    Energy Technology Data Exchange (ETDEWEB)

    Lywood, B. [Crude Quality Inc., Edmonton, AB (Canada)

    2009-07-01

    Many factors must be considered when assessing the feasibility of using condensates as a diluent for bitumen or heavy crude production blending. In addition to commercial issues, the effect of condensate quality is a key consideration. In general, condensate quality refers to density and viscosity. However, valuation decisions could be enhanced through the expansion of quality definitions and understanding. This presentation focused on the parameters that are important in choosing a diluent grade product. It also reviewed pipeline and industry specifications and provided additional information regarding general properties for bitumen and condensate compatibility; sampling and quality testing needs; and existing sources of information regarding condensate quality. tabs., figs.

  19. Semiflexible biopolymers: Microrheology and single filament condensation

    Science.gov (United States)

    Schnurr, Bernhard

    Polymers and their elementary subunits, called monomers, come in an immense variety of structures and sizes, and are of great importance for their material properties as well as a multitude of biological functions. The emphasis here is on semiflexible polymers, which are identified by their intermediate degree of stiffness. Their individual as well as their collective properties when assembled into entangled networks is a topic of great interest to polymer physics, materials science, and biology. Some of the most important semiflexible polymers are biopolymers, with such prominent examples as DNA, F-actin, and microtubules. Their functions range from their use as structural elements in the cytoskeleton of most plant and animal cells, to their role as transport tracks for molecular motors, and the storage of genetic information in their linear sequence. The two parts of this experimental and theoretical thesis address single filament aspects as well as network properties of solutions of semiflexible polymers. In the first part, we describe an optical technique for measuring the bulk properties of soft materials at the local scale. We apply it to a solution of entangled, filamentous actin, a particularly difficult material to characterize with conventional techniques. Beyond a description of measurements and apparatus, we also discuss, from a theoretical point of view, the interpretation and fundamental limitations of this and other microrheological techniques. In the second part, we describe the condensation dynamics of a single, semiflexible filament, induced by changing solvent conditions. A biologically important example of this phenomenon is the condensation of DNA into toroidal structures, which occurs, for instance, in viral capsids. Our observations of a molecular simulation motivate an unexpected pathway of collapse via a series of metastable intermediates we call ``racquet'' states. The analysis of the conformational energies of these structures in the

  20. DNA Nanocarriers for Systemic Administration: Characterization and In Vivo Bioimaging in Healthy Mice

    OpenAIRE

    David, Stéphanie; Passirani,Catherine; Carmoy, Nathalie; Morille, Marie; Mevel, Mathieu; Chatin, Benoit; Benoit, Jean-Pierre; Montier, Tristan; Pitard, Bruno

    2013-01-01

    International audience; We hereby present different DNA nanocarriers consisting of new multimodular systems (MMS), containing the cationic lipid dioleylaminesuccinylparomomycin (DNA MMS DOSP), or bis (guanidinium)-tren-cholesterol (DNA MMS BGTC), and DNA lipid nanocapsules (DNA LNCs). Active targeting of the asialoglycoprotein receptor (ASGP-R) using galactose as a ligand for DNA MMS (GAL DNA MMS) and passive targeting using a polyethylene glycol coating for DNA LNCs (PEG DNA LNCs) should imp...

  1. Condensation on slippery asymmetric bumps

    Science.gov (United States)

    Park, Kyoo-Chul; Kim, Philseok; Grinthal, Alison; He, Neil; Fox, David; Weaver, James C.; Aizenberg, Joanna

    2016-03-01

    Controlling dropwise condensation is fundamental to water-harvesting systems, desalination, thermal power generation, air conditioning, distillation towers, and numerous other applications. For any of these, it is essential to design surfaces that enable droplets to grow rapidly and to be shed as quickly as possible. However, approaches based on microscale, nanoscale or molecular-scale textures suffer from intrinsic trade-offs that make it difficult to optimize both growth and transport at once. Here we present a conceptually different design approach—based on principles derived from Namib desert beetles, cacti, and pitcher plants—that synergistically combines these aspects of condensation and substantially outperforms other synthetic surfaces. Inspired by an unconventional interpretation of the role of the beetle’s bumpy surface geometry in promoting condensation, and using theoretical modelling, we show how to maximize vapour diffusion fluxat the apex of convex millimetric bumps by optimizing the radius of curvature and cross-sectional shape. Integrating this apex geometry with a widening slope, analogous to cactus spines, directly couples facilitated droplet growth with fast directional transport, by creating a free-energy profile that drives the droplet down the slope before its growth rate can decrease. This coupling is further enhanced by a slippery, pitcher-plant-inspired nanocoating that facilitates feedback between coalescence-driven growth and capillary-driven motion on the way down. Bumps that are rationally designed to integrate these mechanisms are able to grow and transport large droplets even against gravity and overcome the effect of an unfavourable temperature gradient. We further observe an unprecedented sixfold-higher exponent of growth rate, faster onset, higher steady-state turnover rate, and a greater volume of water collected compared to other surfaces. We envision that this fundamental understanding and rational design strategy can be

  2. Telomere Chromatin Condensation Assay (TCCA): a novel approach to study structural telomere integrity.

    Science.gov (United States)

    Gonzalez-Vasconcellos, Iria; Alonso-Rodríguez, Silvia; López-Baltar, Isidoro; Fernández, José Luis

    2015-01-01

    Telomeres, the DNA-protein complexes located at the end of linear eukaryotic chromosomes are essential for genome stability. Improper higher-order chromatin organization at the chromosome ends can give rise to telomeric recombination and genomic instability. We report the development of an assay to quantify differences in the condensation of telomeric chromatin, thereby offering new opportunities to study telomere biology and stability. We have combined a DNA nuclease digestion with a quantitative PCR (qPCR) assay of telomeric DNA, which we term the Telomere Chromatin Condensation Assay (TCCA). By quantifying the relative quantities of telomeric DNA that are progressively digested with the exonuclease Bal 31 the method can discriminate between different levels of telomeric chromatin condensation. The structural chromatin packaging at telomeres shielded against exonuclease digestion delivered an estimate, which we term Chromatin Protection Factor (CPF) that ranged from 1.7 to 2.3 fold greater than that present in unpacked DNA. The CPF was significantly decreased when cell cultures were incubated with the DNA hypomethylating agent 5-azacytidine, demonstrating the ability of the TCCA assay to discriminate between packaging levels of telomeric DNA.

  3. Quantum tunnelling in condensed media

    CERN Document Server

    Kagan, Yu

    1992-01-01

    The essays in this book deal with of the problem of quantum tunnelling and related behavior of a microscopic or macroscopic system, which interacts strongly with an ""environment"" - this being some form of condensed matter. The ""system"" in question need not be physically distinct from its environment, but could, for example, be one particular degree of freedom on which attention is focussed, as in the case of the Josephson junction studied in several of the papers. This general problem has been studied in many hundreds, if not thousands, of articles in the literature, in contexts as diverse

  4. Velocity condensation for magnetotactic bacteria

    CERN Document Server

    Rupprecht, Jean-Francois; Bocquet, Lydéric

    2015-01-01

    Magnetotactic swimmers tend to align along magnetic field lines against stochastic reorientations. We show that the swimming strategy, e.g. active Brownian motion versus run-and-tumble dynamics, strongly affects the orientation statistics. The latter can exhibit a velocity condensation whereby the alignment probability density diverges. As a consequence, we find that the swimming strategy affects the nature of the phase transition to collective motion, indicating that L\\'evy run-and-tumble walks can outperform active Brownian processes as strategies to trigger collective behavior.

  5. Dropwise Condensation on Hydrophobic Cylinders

    CERN Document Server

    Park, Kyoo-Chul; Hoang, Michelle; McManus, Brendan; Aizenberg, Joanna

    2016-01-01

    In this work, we studied the effect of the diameter of horizontal hydrophobic cylinders on droplet growth. We postulate that the concentration gradient created by natural convection around a horizontal circular cylinder is related to the droplet growth on the cylinder by condensation. We derive a simple scaling law of droplet growth and compare it with experimental results. The predicted negative exponent of drop diameter (d) as a function of cylinder diameter (D) at different time points is similar to the general trend of experimental data. Further, this effect of cylinder diameter on droplet growth is observed to be stronger than the supersaturation conditions created by different surface temperatures.

  6. Cationic Amphiphiles Increase Activity of Aminoglycoside Antibiotic Tobramycin in the Presence of Airway Polyelectrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Purdy Drew, Kirstin R.; Sanders, Lori K.; Culumber, Zachary W.; Zribi, Olena; Wong, Gerard C.L.; (UIUC)

    2009-06-17

    It is empirically known that anionic polyelectrolytes present in cystic fibrosis (CF) airways due to bacterial infection significantly decrease the activity of cationic antimicrobials via electrostatic binding. In this work, we use synchrotron small-angle X-ray scattering to investigate the interaction between tobramycin, an aminoglycoside antibiotic commonly administered to CF patients via inhalation, with DNA, which is found in high concentrations in the CF airway. We find that interactions between DNA and tobramycin are significantly modified by the presence of mixtures of amphiphilic molecules. We measure a hierarchy of self-assembled structures formed between tobramycin, DNA, and the amphiphile mixtures and show how interactions between these components can be controlled. Results indicate that mixtures of cationic and negative curvature amphiphiles optimized for DNA binding via charge matching and curvature matching can competitively displace bound tobramycin from DNA and thereby drastically suppress tobramycin-DNA binding and resultant antimicrobial inactivation. Growth inhibition assays confirm the increased activity of tobramycin in the presence of DNA with the addition of the amphiphiles. These results suggest that optimized cationic amphiphile solutions have the potential to enhance antimicrobial function in highly infected environments that contain increased concentrations of anionic inflammatory polymers.

  7. Cationic Amphiphiles Increase Activity of Aminoglycoside Antibiotic Tobramycin in the Presence of Airway Polyelectrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Drew, K.R.Purdy; Sanders, L.K.; Culumber, Z.W.; Zribi, O.; Wong, G.C.L.

    2009-05-21

    It is empirically known that anionic polyelectrolytes present in cystic fibrosis (CF) airways due to bacterial infection significantly decrease the activity of cationic antimicrobials via electrostatic binding. In this work, we use synchrotron small-angle X-ray scattering to investigate the interaction between tobramycin, an aminoglycoside antibiotic commonly administered to CF patients via inhalation, with DNA, which is found in high concentrations in the CF airway. We find that interactions between DNA and tobramycin are significantly modified by the presence of mixtures of amphiphilic molecules. We measure a hierarchy of self-assembled structures formed between tobramycin, DNA, and the amphiphile mixtures and show how interactions between these components can be controlled. Results indicate that mixtures of cationic and negative curvature amphiphiles optimized for DNA binding via charge matching and curvature matching can competitively displace bound tobramycin from DNA and thereby drastically suppress tobramycin-DNA binding and resultant antimicrobial inactivation. Growth inhibition assays confirm the increased activity of tobramycin in the presence of DNA with the addition of the amphiphiles. These results suggest that optimized cationic amphiphile solutions have the potential to enhance antimicrobial function in highly infected environments that contain increased concentrations of anionic inflammatory polymers.

  8. Hydrogen bonding versus hyperconjugation in condensed-phase carbocations.

    Science.gov (United States)

    Reed, Christopher A; Stoyanov, Evgenii S; Tham, Fook S

    2013-06-21

    Hyperconjugative stabilization of positive charge in tertiary carbocations is the textbook explanation for their stability and low frequency νCH bands in their IR spectra have long been taken as confirming evidence. While this is substantiated in the gas phase by the very close match of the IR spectrum of argon-tagged t-butyl cation with that calculated under C(s) symmetry, the situation in condensed phases is much less clear. The congruence of νCH(max) of t-Bu(+) in superacid media (2830 cm(-1)) with that in the gas phase (2834 cm(-1)) has recently been shown to be accidental. Rather, νCH(max) varies considerably as a function of counterion in a manner that reveals the presence of significant C-H···anion hydrogen bonding. This paper addresses the question of the relative importance of hyperconjugation versus H-bonding. We show by assigning IR spectra in the νCH region to specific C-H bonds in t-butyl cation that the low frequency νCH(max) band in the IR spectrum of t-butyl cation, long taken as direct evidence for hyperconjugation, appears to be due mostly to H-bonding. The appearance of similar low frequency νCH bands in the IR spectra of secondary alkyl carboranes such as i-Pr(CHB11Cl11), which have predominant sp(3) centres rather than sp(2) centres (and are therefore less supportive of hyperconjugation), also suggests the dominance of H-bonding over hyperconjugation.

  9. Bio-oil fractionation and condensation

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Robert C.; Jones, Samuel T.; Pollard, Anthony

    2017-04-04

    The present invention relates to a method of fractionating bio-oil vapors which involves providing bio-oil vapors comprising bio-oil constituents. The bio-oil vapors are cooled in a first stage which comprises a condenser having passages for the bio-oil separated by a heat conducting wall from passages for a coolant. The coolant in the condenser of the first stage is maintained at a substantially constant temperature, set at a temperature in the range of 75 to 100.degree. C., to condense a first liquid fraction of liquefied bio-oil constituents in the condenser of the first stage. The first liquid fraction of liquified bio-oil constituents from the condenser in the first stage is collected. Also disclosed are steps for subsequently recovering further liquid fractions of liquefied bio-oil constituents. Particular compositions of bio-oil condensation products are also described.

  10. The physics of exciton-polariton condensates

    CERN Document Server

    Lagoudakis, Konstantinos

    2013-01-01

    In 2006 researchers created the first polariton Bose-Einstein condensate at 19K in the solid state. Being inherently open quantum systems, polariton condensates open a window into the unpredictable world of physics beyond the “fifth state of matter”: the limited lifetime of polaritons renders polariton condensates out-of-equilibrium and provides a fertile test-bed for non-equilibrium physics. This book presents an experimental investigation into exciting features arising from this non-equilibrium behavior. Through careful experimentation, the author demonstrates the ability of polaritons to synchronize and create a single energy delocalized condensate. Under certain disorder and excitation conditions the complete opposite case of coexisting spatially overlapping condensates may be observed. The author provides the first demonstration of quantized vortices in polariton condensates and the first observation of fractional vortices with full phase and amplitude characterization. Finally, this book investigate...

  11. Bio-oil fractionation and condensation

    Science.gov (United States)

    Brown, Robert C; Jones, Samuel T; Pollard, Anthony

    2013-07-02

    A method of fractionating bio-oil vapors which involves providing bio-oil vapors comprising bio-oil constituents is described. The bio-oil vapors are cooled in a first stage which comprises a condenser having passages for the bio-oil separated by a heat conducting wall from passages for a coolant. The coolant in the condenser of the first stage is maintained at a substantially constant temperature, set at a temperature in the range of 75 to 100.degree. C., to condense a first liquid fraction of liquefied bio-oil constituents in the condenser of the first stage. The first liquid fraction of liquified bio-oil constituents from the condenser in the first stage is collected. Also described are steps for subsequently recovering further liquid fractions of liquefied bio-oil constituents. Particular compositions of bio-oil condensation products are also described.

  12. Condensation induced water hammer safety

    Energy Technology Data Exchange (ETDEWEB)

    Gintner, M.A.

    1997-03-10

    Condensation induced water hammer events in piping systems can cause catastrophic steam system failures which can result in equipment damage, personal injury, and even death. As an industry, we have learned to become accustomed to the ''banging'' that we often hear in our steam piping systems, and complacent in our actions to prevent it. It is unfortunate that lives are lost needlessly, as this type of water hammer event is preventable if one only applies some basic principles when operating and maintaining their steam systems. At the U. S. Department of Energy's Hanford Site where I work, there was one such accident that occurred in 1993 which took the life of a former co-worker and friend of mine. Hanford was established as part of the Manhattan Project during World War II. it is a 560 square mile complex located along the banks of the Columbia River in Southeastern Washington State. For almost 45 years, hanford's mission was to produce weapons grade plutonium for our nations defense programs. Today, Hanford no longer produces plutonium, but is focused on site clean-up and economic diversification. Hanford still uses steam for heating and processing activities, utilizing over 20 miles of piping distribution systems similar to those found in industry. Although these aging systems are still sound, they cannot stand up to the extreme pressure pulses developed by a condensation induced water hammer.

  13. Multi-shell model of ion-induced nucleic acid condensation

    Science.gov (United States)

    Tolokh, Igor S.; Drozdetski, Aleksander V.; Pollack, Lois; Baker, Nathan A.; Onufriev, Alexey V.

    2016-04-01

    We present a semi-quantitative model of condensation of short nucleic acid (NA) duplexes induced by trivalent cobalt(iii) hexammine (CoHex) ions. The model is based on partitioning of bound counterion distribution around single NA duplex into "external" and "internal" ion binding shells distinguished by the proximity to duplex helical axis. In the aggregated phase the shells overlap, which leads to significantly increased attraction of CoHex ions in these overlaps with the neighboring duplexes. The duplex aggregation free energy is decomposed into attractive and repulsive components in such a way that they can be represented by simple analytical expressions with parameters derived from molecular dynamic simulations and numerical solutions of Poisson equation. The attractive term depends on the fractions of bound ions in the overlapping shells and affinity of CoHex to the "external" shell of nearly neutralized duplex. The repulsive components of the free energy are duplex configurational entropy loss upon the aggregation and the electrostatic repulsion of the duplexes that remains after neutralization by bound CoHex ions. The estimates of the aggregation free energy are consistent with the experimental range of NA duplex condensation propensities, including the unusually poor condensation of RNA structures and subtle sequence effects upon DNA condensation. The model predicts that, in contrast to DNA, RNA duplexes may condense into tighter packed aggregates with a higher degree of duplex neutralization. An appreciable CoHex mediated RNA-RNA attraction requires closer inter-duplex separation to engage CoHex ions (bound mostly in the "internal" shell of RNA) into short-range attractive interactions. The model also predicts that longer NA fragments will condense more readily than shorter ones. The ability of this model to explain experimentally observed trends in NA condensation lends support to proposed NA condensation picture based on the multivalent "ion binding

  14. Structure of Nonlocal Vacuum Condensate of Quarks

    Institute of Scientific and Technical Information of China (English)

    周丽娟; 马维兴

    2003-01-01

    The Dyson-Schwinger formalism is used to derive a fully dressed quark propagator. By use of the derived form of the quark propagator, the structure of non-local quark vacuum condensate is studied, and the values of local quark vacuum condensate as well as quark gluon mixed condensate are calculated. The theoretical predictions are in good agreement with the empirical one used commonly in the literature.

  15. Ultra-low threshold polariton condensation

    CERN Document Server

    Steger, Mark; Alberi, Kirstin; Mascarenhas, Angelo; Snoke, David W; Pfeiffer, Loren N; West, Ken

    2016-01-01

    We demonstrate condensation of microcavity polaritons with a very sharp threshold occuring at two orders of magnitude lower pump intensity than previous demonstrations of condensation. The long cavity-lifetime and trapping and pumping geometries are crucial to the realization of this low threshold. Polariton condensation, or "polariton lasing" has long been proposed as a promising source of coherent light at lower threshold than traditional lasing, and these results suggest methods to bring this threshold even lower.

  16. Van der Waals Interactions and Exciton Condensation

    Science.gov (United States)

    Handel, P. H.; Kittel, C.

    1971-01-01

    It is shown that the van der Waals interaction can lead at low temperatures to a condensed state of excitons with properties in qualitative agreement with the observations of exciton droplets. Our calculation gives a binding energy of the correct sign and magnitude for the exciton condensate. In a diclectric medium, the strong enhancement of the exciton polarizability leads to a giant van der Waals interaction, and this interaction appears to make possible a condensed exciton phase. PMID:16591958

  17. Lorentz violation and Condensed Matter Physics

    CERN Document Server

    Ajaib, Muhammad Adeel

    2014-01-01

    We present heuristic arguments that hint to a possible connection of Lorentz violation with observed phenomenon in condensed matter physics. Various references from condensed matter literature are cited where operators in the Standard Model Extension (SME) appear to be enhanced. Based on this we propose that, in the non-relativistic limit, Lorentz violation in the context of the SME exhibits itself in various condensed matter systems.

  18. Studies of base pair sequence effects on DNA solvation based on all-atom molecular dynamics simulations

    Indian Academy of Sciences (India)

    Surjit B Dixit; Mihaly Mezei; David L Beveridge

    2012-07-01

    Detailed analyses of the sequence-dependent solvation and ion atmosphere of DNA are presented based on molecular dynamics (MD) simulations on all the 136 unique tetranucleotide steps obtained by the ABC consortium using the AMBER suite of programs. Significant sequence effects on solvation and ion localization were observed in these simulations. The results were compared to essentially all known experimental data on the subject. Proximity analysis was employed to highlight the sequence dependent differences in solvation and ion localization properties in the grooves of DNA. Comparison of the MD-calculated DNA structure with canonical A- and B-forms supports the idea that the G/C-rich sequences are closer to canonical A- than B-form structures, while the reverse is true for the poly A sequences, with the exception of the alternating ATAT sequence. Analysis of hydration density maps reveals that the flexibility of solute molecule has a significant effect on the nature of observed hydration. Energetic analysis of solute–solvent interactions based on proximity analysis of solvent reveals that the GC or CG base pairs interactmore strongly with watermolecules in the minor groove of DNA that the AT or TA base pairs, while the interactions of the AT or TA pairs in the major groove are stronger than those of the GC or CG pairs. Computation of solvent-accessible surface area of the nucleotide units in the simulated trajectories reveals that the similarity with results derived from analysis of a database of crystallographic structures is excellent. The MD trajectories tend to follow Manning’s counterion condensation theory, presenting a region of condensed counterions within a radius of about 17 Å from the DNA surface independent of sequence. The GC and CG pairs tend to associate with cations in the major groove of the DNA structure to a greater extent than the AT and TA pairs. Cation association is more frequent in the minor groove of AT than the GC pairs. In general

  19. Mild access to planar-chiral ortho-condensed aromatic ferrocenes via gold(i)-catalyzed cycloisomerization of ortho-alkynylaryl ferrocenes.

    Science.gov (United States)

    Urbano, Antonio; Hernández-Torres, Gloria; Del Hoyo, Ana M; Martínez-Carrión, Alicia; Carmen Carreño, M

    2016-05-11

    An efficient approach to (Rp) planar-chiral tri- and tetracyclic ortho-condensed aromatic ferrocenes was developed through the enantioselective cationic Au(i)-catalyzed cycloisomerization, in the presence of bidentate phosphine ligand (R)-DTBM-Segphos, from readily available ortho-alkynylaryl ferrocenes under very mild conditions (11 examples, up to 92% yield and 93% ee).

  20. Enhanced condensation heat transfer with wettability patterning

    Science.gov (United States)

    Sinha Mahapatra, Pallab; Ghosh, Aritra; Ganguly, Ranjan; Megaridis, Constantine

    2015-11-01

    Condensation of water vapor on metal surfaces is useful for many engineering applications. A facile and scalable method is proposed for removing condensate from a vertical plate during dropwise condensation (DWC) in the presence of non-condensable gases (NCG). We use wettability-patterned superhydrophilic tracks (filmwise condensing domains) on a mirror-finish (hydrophilic) aluminum surface that promotes DWC. Tapered, horizontal ``collection'' tracks are laid to create a Laplace pressure driven flow, which collects condensate from the mirror-finish domains and sends it to vertical ``drainage tracks'' for gravity-induced shedding. An optimal design is achieved by changing the fractional area of superhydrophilic tracks with respect to the overall plate surface, and augmenting capillary-driven condensate-drainage by adjusting the track spatial layout. The design facilitates pump-less condensate drainage and enhances DWC heat transfer on the mirror-finish regions. The study highlights the relative influences of the promoting and retarding effects of dropwise and filmwise condensation zones on the overall heat transfer improvement on the substrate. The study demonstrated ~ 34% heat transfer improvement on Aluminum surface for the optimized design.

  1. Advances in modelling of condensation phenomena

    Energy Technology Data Exchange (ETDEWEB)

    Liu, W.S.; Zaltsgendler, E. [Ontario Hydro Nuclear, Toronto (Canada); Hanna, B. [Atomic Energy of Canada Limited, Pinawa, Manitoba (Canada)

    1997-07-01

    The physical parameters in the modelling of condensation phenomena in the CANDU reactor system codes are discussed. The experimental programs used for thermal-hydraulic code validation in the Canadian nuclear industry are briefly described. The modelling of vapour generation and in particular condensation plays a key role in modelling of postulated reactor transients. The condensation models adopted in the current state-of-the-art two-fluid CANDU reactor thermal-hydraulic system codes (CATHENA and TUF) are described. As examples of the modelling challenges faced, the simulation of a cold water injection experiment by CATHENA and the simulation of a condensation induced water hammer experiment by TUF are described.

  2. Optimizing Cationic and Neutral Lipids for Efficient Gene Delivery at High Serum Content

    Science.gov (United States)

    Majzoub, Ramsey N.; Hwu, Yeu-kuang; Liang, Keng S.; Leal, Cecília; Safinya, Cyrus R.

    2014-01-01

    Background Cationic liposome (CL)-DNA complexes are promising gene delivery vectors with potential applications in gene therapy. A key challenge in creating CL-DNA complexes for applications is that their transfection efficiency (TE) is adversely affected by serum. In particular, little is known about the effects of high serum contents on TE even though this may provide design guidelines for applications in vivo. Methods We prepared CL-DNA complexes in which we varied the neutral lipid (DOPC, glycerol-monooleate (GMO), cholesterol), the headgroup charge and chemical structure of the cationic lipid, and the ratio of neutral to cationic lipid; we then measured the TE of these complexes as a function of serum content and assessed their cytotoxicity. We tested selected formulations in two human cancer cell lines (M21/melanoma and PC-3/prostate cancer). Results In the absence of serum, all CL-DNA complexes of custom-synthesized multivalent lipids show high TE. Certain combinations of multivalent lipids and neutral lipids, such as MVL5(5+)/GMO-DNA complexes or complexes based on the dendritic-headgroup lipid TMVLG3(8+) exhibited high TE both in the absence and presence of serum. Although their TE still dropped to a small extent in the presence of serum, it reached or surpassed that of benchmark commercial transfection reagents, in particular at high serum content. Conclusions Two-component vectors (one multivalent cationic lipid and one neutral lipid) can rival or surpass benchmark reagents at low and high serum contents (up to 50%, v/v). We suggest guidelines for optimizing the serum resistance of CL-DNA complexes based on a given cationic lipid. PMID:24753287

  3. Condensing the information in DNA with double-headed nucleotides

    DEFF Research Database (Denmark)

    Hornum, Mick; Sharma, Pawan K; Reslow-Jacobsen, Charlotte

    2017-01-01

    A normal duplex holds as many Watson-Crick base pairs as the number of nucleotides in its constituent strands. Here we establish that single nucleotides can be designed to functionally imitate dinucleotides without compromising binding affinity. This effectively allows sequence information to be ...

  4. Involvement of organic cation transporter 1 in hepatic and intestinal distribution of metformin

    NARCIS (Netherlands)

    Wang, DS; Jonker, JW; Kato, Y; Kusuhara, H; Schinkel, AH; Sugiyama, Y

    2002-01-01

    Metformin, a biguanide, is widely used as an oral hypoglycemic agent for the treatment of type 2 diabetes mellitus. The purpose of the present study was to investigate the role of organic cation transporter 1 (Oct1) in the disposition of metformin. Transfection of rat Oct1 cDNA results in the time-d

  5. The mean condensate heat resistance of dropwise condensation with flowing inert gases

    NARCIS (Netherlands)

    van der Geld, C.W.M.; Brouwers, Jos

    1995-01-01

    The quantification of the condensate heat resistance is studied for dropwise condensation from flowing air-steam mixtures. Flows are essentially laminar and stable with gas Reynolds numbers around 900 and 2000. The condensate shaping up as hemispheres on a plastic plane wall and the presence of iner

  6. The mean condensate heat resistance of dropwise condensation with flowing inert gases

    NARCIS (Netherlands)

    Geld, van der C.W.M.; Brouwers, H.J.H.

    1995-01-01

    The quantification of the condensate heat resistance is studied for dropwise condensation from flowing air-steam mixtures. Flows are essentially laminar and stable with gas Reynolds numbers around 900 and 2000. The condensate shaping up as hemispheres on a plastic plane wall and the presence of iner

  7. The mean condensate heat resistance of dropwise condensation with flowing inert gases

    NARCIS (Netherlands)

    van der Geld, C.W.M.; Brouwers, Jos

    1995-01-01

    The quantification of the condensate heat resistance is studied for dropwise condensation from flowing air-steam mixtures. Flows are essentially laminar and stable with gas Reynolds numbers around 900 and 2000. The condensate shaping up as hemispheres on a plastic plane wall and the presence of

  8. Space, Time, and Tachyon Condensation

    CERN Document Server

    McInnes, B

    2006-01-01

    It has often been suggested that strings propagating on spatial sections with one or more dimensions compactified to a circle might help to resolve the initial singularity in cosmology. Assuming that Inflation occurred, it can however be shown, under extremely mild assumptions, that spatial sections having first homology groups which contain an element of infinite order actually \\emph{worsen} the singularity problem. We illustrate the force of this observation by explaining its consequences for recent ideas about winding strings and tachyon condensation as resolutions of the initial singularity. We argue that, in order to understand the initial singularity, one has to understand why the versions of de Sitter spacetime with compact flat spatial sections are themselves geodesically incomplete. To this end, we study the problem of the "twins" in these spacetimes. This study suggests that the singularity is not "resolved" but is instead made physically inaccessible.

  9. Condensation on Slippery Asymmetric Bumps

    CERN Document Server

    Park, Kyoo-Chul; He, Neil; Aizenberg, Joanna

    2015-01-01

    Bumps are omnipresent from human skin to the geological structures on planets, which offer distinct advantages in numerous phenomena including structural color, drag reduction, and extreme wettability. Although the topographical parameters of bumps such as radius of curvature of convex regions significantly influence various phenomena including anti-reflective structures and contact time of impacting droplets, the effect of the detailed bump topography on growth and transport of condensates have not been clearly understood. Inspired by the millimetric bumps of the Namib Desert beetle, here we report the identified role of radius of curvature and width of bumps with homogeneous surface wettability in growth rate, coalescence and transport of water droplets. Further rational design of asymmetric convex topography and synergetic combination with slippery coating simultaneously enable self-transport, leading to unseen five-fold higher growth rate and an order of magnitude faster shedding time of droplets compared...

  10. Exploring Multiscale Materials From Water, DNA to Bacteria

    DEFF Research Database (Denmark)

    Song, Jie

    2014-01-01

    multifunctional biomaterials at nanoscale on water, DNA, and bacteria. With this scale-up outline, the condensation of water atmospheric water, the self-assembly of DNA and the electron transfer of filamentous bacteria are discussed in the each chapter, along with the advanced function of AFM and TEM engaging....... In the water condensation project, the condensation of water vapor was investigated by in situ thermally controlled atomic force microscopy. Comparison with molecular dynamics simulation reveals that the Stranski-Krastanov growth model is more reasonable to describe the whole water condensation process...... and kinetics of the DNA nanotechnology from 2D to 3D DNA origami and tiles. After that, inspiration from the thermodynamic information gives us a possibility to explore the method for self-assembly DNA nanostructures at room temperature. And for the filamentous bacteria project, we report the finding of long...

  11. Afrikaans Syllabification Patterns

    Directory of Open Access Journals (Sweden)

    Tilla Fick

    2010-01-01

    Full Text Available In contrast to English, automatic hyphenation by computer of Afrikaans words is a problem that still needs to be addressed, since errors are still often encountered in printed text. An initial step in this task is the ability to automatically syllabify words. Since new words are created continuously by joining words, it is necessary to develop an “intelligent” technique for syllabification. As a first phase of the research, we consider only the orthographic information of words, and disregard both syntactic and morphological information. This approach allows us to use machine-learning techniques such as artificial neural networks and decision trees that are known for their pattern recognition abilities. Both these techniques are trained with isolated patterns consisting of input patterns and corresponding outputs (or targets that indicate whether the input pattern should be split at a certain position, or not. In the process of compiling a list of syllabified words from which to generate training data for the  syllabification problem, irregular patterns were identified. The same letter patterns are split differently in different words and complete words that are spelled identically are split differently due to meaning. We also identified irregularities in and between  the different dictionaries that we used. We examined the influence range of letters that are involved in irregularities. For example, for their in agter-ente and vaste-rente we have to consider three letters to the left of r to be certain where the hyphen should be inserted. The influence range of the k in verstek-waarde and kleinste-kwadrate is four to the left and three to the right. In an analysis of letter patterns in Afrikaans words we found that the letter e has the highest frequency overall (16,2% of all letters in the word list. The frequency of words starting with s is the highest, while the frequency of words ending with e is the highest. It is important to

  12. Condensed Matter Theories - Volume 22

    Science.gov (United States)

    Reinholz, Heidi; Röpke, Gerd; de Llano, Manuel

    2007-09-01

    pt. A. Fermi liquids. Pressure comparison between the spherical cellular model and the Thomas-Fermi model / G.A. Baker, Jr. Pair excitations and vertex corrections in Fermi fluids and the dynamic structure function of two-dimension 3He / H.M. Böhm, H. Godfrin, E. Krotscheck, H.J. Lauter, M. Meschke and M. Panholzer. Condensation of helium in wedges / E.S. Hernádez ... [et al.]. Non-Fermi liquid behavior from the Fermi-liquid approach / V.A. Khodel ... [et al.]. Theory of third sound and stability of thin 3He-4He superfluid films / E. Krotscheck and M.D. Miller. Pairing in asymmetrical Fermi systems / K.F. Quader and R. Liao. Ground-state properties of small 3He drops from quantum Monte Carlo simulations / E. Sola, J. Casulleras and J. Boronat. Ground-state energy and compressibility of a disordered two-dimensional electron gas / Tanatar ... [et al.]. Quasiexcitons in photoluminescence of incompressible quantum liquids / A. Wójs, A.G ladysiewicz and J.J. Quinn -- pt. B. Bose liquids. Quantum Boltzmann liquids / K.A. Gernoth, M L. Ristig and T. Lindenau. Condensate fraction in the dynamic structure function of Bose fluids / M. Saarela, F. Mazzanti and V. Apaja -- pt. C. Strongly-correlated electronic systems. Electron gas in high-field nanoscopic transport: metallic carbon nanotubes / F. Green and D. Neilson. Evolution and destruction of the Kondo effect in a capacitively coupled double dot system / D.E. Logan and M.R. Galpin. The method of increments-a wavefunction-based Ab-Initio correlation method for solids / B. Paulus. Fractionally charged excitations on frustrated lattices / E. Runge, F. Pollmann and P. Fulde. 5f Electrons in actinides: dual nature and photoemission spectra / G. Zwicknagl -- pt. D. Magnetism. Magnetism in disordered two-dimensional Kondo-Necklace / W. Brenig. On the de Haas-can Alphen oscillation in 2D / S. Fujita and D.L. Morabito. Dynamics in one-dimensional spin systems-density matrix reformalization group study / S. Nishimoto and M

  13. Assessment of the controllability of condensible emissions. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Shareef, G.S.; Waddell, J.T.

    1990-10-01

    The report gives results of a study to gain insights into the condensible emissions area from an air toxics perspective, with emphasis on controllability and chemical composition of these emissions. The study: compiled existing data on condensible emissions; determined the chemical composition of condensible emissions, where possible; identified source categories that are major emitters of condensibles; evaluated the effectiveness of various control devices in reducing condensible emissions; and evaluated how the performance of currently available control technologies can be improved to better control condensible emissions. Two data bases were developed: the Condensibles Data Base contains 43 emission source categories; the Specialized Condensibles Data Base focuses on the chemical composition of condensible emissions.

  14. Soliton resonance in bose-einstein condensate

    Science.gov (United States)

    Zak, Michail; Kulikov, I.

    2002-01-01

    A new phenomenon in nonlinear dispersive systems, including a Bose-Einstein Condensate (BEC), has been described. It is based upon a resonance between an externally induced soliton and 'eigen-solitons' of the homogeneous cubic Schrodinger equation. There have been shown that a moving source of positive /negative potential induces bright /dark solitons in an attractive / repulsive Bose condensate.

  15. ASSESSMENT OF THE CONTROLLABILITY OF CONDENSIBLE EMISSIONS

    Science.gov (United States)

    The report gives results of a study to gain insights into the condensible emissions area from an air toxics perspective, with emphasis on controllability and chemical composition of these emissions. he study compiled existing data on condensible emissions; determined the chemical...

  16. Phase contrast imaging of Bose condensed clouds

    NARCIS (Netherlands)

    Meppelink, R; Rozendaal, R.A.; Koller, S.B.; Vogels, J.M.; van der Straten, P.

    2010-01-01

    Phase contrast imaging is used to observe Bose-Einstein condensates (BECs) at finite temperature in situ. The imaging technique is used to accurately derive the absolute phase shift of a probe laser beam due to both the condensate and the thermal cloud. The accuracy of the method is enhanced by usin

  17. Bose-Einstein condensation of atomic hydrogen

    NARCIS (Netherlands)

    Willmann, L

    1999-01-01

    The recent creation of a Bose-Einstein condensate of atomic hydrogen has added a new system to this exciting field, The differences between hydrogen and the alkali metal atoms require other techniques for the initial trapping and cooling of the atoms and the subsequent detection of the condensate. T

  18. Hydrophilic structures for condensation management in appliances

    Science.gov (United States)

    Kuehl, Steven John; Vonderhaar, John J.; Wu, Guolian; Wu, Mianxue

    2016-02-02

    An appliance that includes a cabinet having an exterior surface; a refrigeration compartment located within the cabinet; and a hydrophilic structure disposed on the exterior surface. The hydrophilic structure is configured to spread condensation. The appliance further includes a wicking structure located in proximity to the hydrophilic structure, and the wicking structure is configured to receive the condensation.

  19. Gravitino condensation, supersymmetry breaking and inflation

    CERN Document Server

    Houston, N

    2015-01-01

    Motivated by dualistic considerations of the reality of quark condensation in quantum chromodynamics, and the connections of supergravity to the exotic physics of string and M-theory, in this thesis we investigate the dynamical breaking of local supersymmetry via gravitino condensation. We firstly demonstrate non-perturbative gravitino mass generation via this mechanism in flat spacetime, and from this derive the condensate mode wavefunction renormalisation. By then calculating the full canonically normalised one-loop effective potential for the condensate mode about a de Sitter background, we demonstrate that, contrary to claims in the literature, this process may both occur and function in a phenomenologically viable manner. In particular, we find that outside of certain unfortunate gauge choices, the stability of the condensate is intimately tied via gravitational degrees of freedom to the sign of the tree-level cosmological constant. Furthermore, we find that the energy density liberated may provide the n...

  20. When does lasing become a condensation phenomenon?

    CERN Document Server

    Fischer, Baruch

    2012-01-01

    We present a generic classical light condensation (LC) phenomenon in linear photonic mode systems, such as cw laser cavities, in a noisy environment (spontaneous emission, etc.), based on weighting the modes in a loss-gain scale rather than in photon energy. It is characterized by a sharp transition from multi- to single-mode oscillation. The study uses a linear multivariate Langevin formulation which gives a mode occupation hierarchy that functions like Bose-Einstein statistics. We find that condensation occurs when the spectral filtering has near the lowest loss mode a power law dependence with exponent smaller than 1. We then discuss how and when condensation occurs in photon systems, how it relates to lasing, and the difficulties to observe regular photon Bose-Einstein condensation (BEC) in laser cavities. We raise the possibility that recent experiments on photon condensation in optical cavities fall in a classical LC or lasing category rather than being a thermal-quantum BEC phenomenon.

  1. Advancements in Anion Exchange Membrane Cations

    Energy Technology Data Exchange (ETDEWEB)

    Sturgeon, Matthew R. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Long, Hai [National Renewable Energy Lab. (NREL), Golden, CO (United States); Park, Andrew M. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Pivovar, Bryan S. [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2015-10-15

    Anion-exchange membrane fuel cells (AME-FCs) are of increasingly popular interest as they enable the use of non-Pt fuel cell catalysts, the primary cost limitation of proton exchange membrane fuel cells. Benzyltrimethyl ammonium (BTMA) is the standard cation that has historically been utilized as the hydroxide conductor in AEMs. Herein we approach AEMs from two directions. First and foremost we study the stability of several different cations in a hydroxide solution at elevated temperatures. We specifically targeted BTMA and methoxy and nitro substituted BTMA. We've also studied the effects of adding an akyl spacer units between the ammonium cation and the phenyl group. In the second approach we use computational studies to predict stable ammonium cations, which are then synthesized and tested for stability. Our unique method to study cation stability in caustic conditions at elevated temperatures utilizes Teflon Parr reactors suitable for use under various temperatures and cation concentrations. NMR analysis was used to determine remaining cation concentrations at specific time points with GCMS analysis verifying product distribution. We then compare the experimental results with calculated modeling stabilities. Our studies show that the electron donating methoxy groups slightly increase stability (compared to that of BTMA), while the electron withdrawing nitro groups greatly decrease stability in base. These results give insight into possible linking strategies to be employed when tethering a BTMA like ammonium cation to a polymeric backbone; thus synthesizing an anion exchange membrane.

  2. Cation diffusion in the natural zeolite clinoptilolite

    Energy Technology Data Exchange (ETDEWEB)

    Dyer, A.; White, K.J. [Science Research Institute, Chemistry Division, Cockcroft Building, University of Salford, Salford (United Kingdom)

    1999-12-14

    The natural zeolite clinoptilolite is mined commercially in many parts of the world. It is a selective exchanger for the ammonium cation and this has prompted its use in waste water treatment, swimming pools and in fish farming. It is also used to scavenge radioisotopes in nuclear waste clean-up. Further potential uses for clinoptilolite are in soil amendment and remediation. The work described herein provides thermodynamic data on cation exchange processes in clinoptilolite involving the NH{sub 4}, Na, K, Ca, and Mg cations. The data includes estimates of interdiffusion coefficients together with free energies, entropies and energies of activation for the cation exchanges studied. Suggestions are made as to the mechanisms of cation-exchanges involved.

  3. Multi-shell model of ion-induced nucleic acid condensation

    Energy Technology Data Exchange (ETDEWEB)

    Tolokh, Igor S. [Department of Computer Science, Virginia Tech, Blacksburg, Virginia 24061, USA; Drozdetski, Aleksander V. [Department of Physics, Virginia Tech, Blacksburg, Virginia 24061, USA; Pollack, Lois [School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853-3501, USA; Baker, Nathan A. [Advanced Computing, Mathematics, and Data Division, Pacific Northwest National Laboratory, Richland, Washington 99352, USA; Division of Applied Mathematics, Brown University, Providence, Rhode Island 02912, USA; Onufriev, Alexey V. [Department of Computer Science, Virginia Tech, Blacksburg, Virginia 24061, USA; Department of Physics, Virginia Tech, Blacksburg, Virginia 24061, USA

    2016-04-21

    We present a semi-quantitative model of condensation of short nucleic acid (NA) duplexes in- duced by tri-valent cobalt hexammine (CoHex) ions. The model is based on partitioning of bound counterion distribution around single NA duplex into “external” and “internal” ion binding shells distinguished by the proximity to duplex helical axis. The duplex aggregation free energy is de- composed into attraction and repulsion components represented by simple analytic expressions. The source of the short-range attraction between NA duplexes in the aggregated phase is the in- teraction of CoHex ions in the overlapping regions of the “external” shells with the oppositely charged duplexes. The attraction depends on CoHex binding affinity to the “external” shell of nearly neutralized duplex and the number of ions in the shell overlapping volume. For a given NA duplex sequence and structure, these parameters are estimated from molecular dynamics simula- tion. The attraction is opposed by the residual repulsion of nearly neutralized duplexes as well as duplex configurational entropy loss upon aggregation. The estimates of the aggregation free energy are consistent with the experimental range of NA duplex condensation propensities, including the unusually poor condensation of RNA structures and subtle sequence effects upon DNA conden- sation. The model predicts that, in contrast to DNA, RNA duplexes may condense into tighter packed aggregates with a higher degree of duplex neutralization. The model also predicts that longer NA fragments will condense easier than shorter ones. The ability of this model to explain experimentally observed trends in NA condensation, lends support to proposed NA condensation picture based on the multivalent “ion binding shells”.

  4. Ancient DNA

    DEFF Research Database (Denmark)

    Willerslev, Eske; Cooper, Alan

    2004-01-01

    ancient DNA, palaeontology, palaeoecology, archaeology, population genetics, DNA damage and repair......ancient DNA, palaeontology, palaeoecology, archaeology, population genetics, DNA damage and repair...

  5. Mono-cationic detergents play a critical role in the development of liposome-based gene vector via controlling its lamellarity

    Science.gov (United States)

    Suzuki, Ryosuke; Yamada, Yuma; Kawamura, Eriko; Harashima, Hideyoshi

    2014-08-01

    Controlling the number of lipid bilayers, the lamellarity, in a liposome is a major factor in the in vivo/in vitro pharmacokinetics of drug delivery using liposome-based nanocarriers. Findings reported in a previous study indicated that a mono-cationic detergent (MCD) could be useful in controlling liposomal size via interaction with the lipid envelope. Here, we investigated controlling the lamellarity of the liposomal gene vector by MCD, using a multifunctional envelope-type nano device (MEND). The MEND consisted of a condensed plasmid DNA core and lipid envelopes. The size of the MCD-contained MEND (MCD-MEND) decreased as a function of the amount of MCD, indicating that MCD can be used to control the number of the lipid bilayers. We also developed a triple-layered MEND (TL-MEND) by packaging a di-lamellar MEND into an MCD-containing lipid bilayer. We hypothesized that the TL-MEND would efficiently deliver a gene to the nucleus, when the outer single bilayer fused with the plasma membrane and the inner double membranes then fused with the nuclear double membranes. Transfection assays showed that the TL-MEND had a high transfection activity in JAWS II cells, non-dividing cells. These results indicate that MCD has the potential for enhancing the gene delivery by controlling liposomal lamellarity.

  6. The antimicrobial polymer PHMB enters cells and selectively condenses bacterial chromosomes.

    Science.gov (United States)

    Chindera, Kantaraja; Mahato, Manohar; Sharma, Ashwani Kumar; Horsley, Harry; Kloc-Muniak, Klaudia; Kamaruzzaman, Nor Fadhilah; Kumar, Satish; McFarlane, Alexander; Stach, Jem; Bentin, Thomas; Good, Liam

    2016-03-21

    To combat infection and antimicrobial resistance, it is helpful to elucidate drug mechanism(s) of action. Here we examined how the widely used antimicrobial polyhexamethylene biguanide (PHMB) kills bacteria selectively over host cells. Contrary to the accepted model of microbial membrane disruption by PHMB, we observed cell entry into a range of bacterial species, and treated bacteria displayed cell division arrest and chromosome condensation, suggesting DNA binding as an alternative antimicrobial mechanism. A DNA-level mechanism was confirmed by observations that PHMB formed nanoparticles when mixed with isolated bacterial chromosomal DNA and its effects on growth were suppressed by pairwise combination with the DNA binding ligand Hoechst 33258. PHMB also entered mammalian cells, but was trapped within endosomes and excluded from nuclei. Therefore, PHMB displays differential access to bacterial and mammalian cellular DNA and selectively binds and condenses bacterial chromosomes. Because acquired resistance to PHMB has not been reported, selective chromosome condensation provides an unanticipated paradigm for antimicrobial action that may not succumb to resistance.

  7. Cationic schiff base amphiphiles and their metal complexes: Surface and biocidal activities against bacteria and fungi.

    Science.gov (United States)

    Negm, N A; Zaki, M F; Salem, M A I

    2010-05-01

    A series of cationic surfactants containing schiff base groups was synthesized by condensation of four fatty amines namely: dodecyl, tetradecyl, hexadecyl and octadecyl amine and 4-diethyl aminobenzaldehyde (1-4), as well as their metal complexes with divalent transition metal ions including Co, Cu and Mn (5-16). The surface activities of the synthesized surfactants were influenced by their chemical structures and the type of the transition metals. The biological activity measurements of the parent cationic schiff bases showed high efficacy against Gram positive and Gram negative bacterial strains and fungi. While on complexation, the biocidal activity was increased remarkably. The biocidal activity of the tested compounds against sulfur reducing bacteria showed promising results in the field of biocide applications.

  8. A link between chromatin condensation mechanisms and Huntington's disease: connecting the dots.

    Science.gov (United States)

    Lokhande, Sonali; Patra, Biranchi N; Ray, Animesh

    2016-11-15

    Huntington's disease is a rare neurodegenerative disorder whose complex pathophysiology exhibits system-wide changes in the body, with striking and debilitating clinical features targeting the central nervous system. Among the various molecular functions affected in this disease, mitochondrial dysfunction and transcriptional dysregulation are some of the most studied aspects of this disease. However, there is evidence of the involvement of a mutant Huntingtin protein in the processes of DNA damage, chromosome condensation and DNA repair. This review attempts to briefly recapitulate the clinical features, model systems used to study the disease, major molecular processes affected, and, more importantly, examines recent evidence for the involvement of the mutant Huntingtin protein in the processes regulating chromosome condensation, leading to DNA damage response and neuronal death.

  9. New ion exchange resin designs and regeneration procedures yield improved performance for various condensate polishing applications

    Energy Technology Data Exchange (ETDEWEB)

    Najmy, S.W. [Dow Chemical Co., Midland, MI (United States)

    2002-07-01

    Condensate polishing is an application with many different design and operational aspects. The past decade has brought new challenges for improved water quality with respect to both soluble and insoluble contaminants. Nonetheless, the endeavors to understand the compositional complexities of the ion exchange resin bead and the convoluted dynamics of ion exchange chemistry and chemical engineering mechanisms occurring within the mixed bed condensate polisher have brought new ideas and expectations for ion exchange resin in deep-bed condensate polishers than ever before. The new products and procedures presented here are a collaboration of a great deal of effort on the part of researchers, consultants, system engineers, station chemists, lab technicians and others. The studies discussed in this paper unequivocally demonstrate the merits of: 1. A specially designed cation resin to achieve greater than 95% insoluble iron removal efficiency, 2. A less-separable mixed resin for improved control of reactor water sulfate in BWR primary cycles, 3. Applying increased levels of regeneration chemicals and retrofitting the service vessels with re-mixing capability to improve the operation of deep-bed condensate polishers in PWR secondary cycles. (authors)

  10. Depletion-induced instability in protein-DNA mixtures: Influence of protein charge and size

    NARCIS (Netherlands)

    Vries, de R.J.

    2006-01-01

    While there is abundant experimental and theoretical work on polymer-induced DNA condensation, it is still unclear whether globular proteins can condense linear DNA or not. We develop a simple analytical approximation for the depletion attraction between rodlike segments of semiflexible

  11. Isolation of homoleptic platinum oxyanionic complexes with doubly protonated diazacrown cation

    Science.gov (United States)

    Vasilchenko, Danila; Tkachev, Sergey; Baidina, Iraida; Romanenko, Galina; Korenev, Sergey

    2017-02-01

    Doubly protonated diazacrown ether cation (1,4,10,13-tetraoxa-7,16-diazoniacyclooctadecane DCH22+) was used for the efficient isolation of the homoleptic platinum complexes [Pt(NO3)6]2- and [Pt(C2O4)2]2- to crystalline solid phases from solutions containing mixtures of related platinum complexes. DCH22+ molecules in nitric acid solution were shown to prevent the condensation of mononuclear [Pt(H2O)n(NO3)6-n]n-2 species.

  12. Influence of chromatin condensation on the number of direct DSB damages induced by ions studied using a Monte Carlo code.

    Science.gov (United States)

    Dos Santos, M; Clairand, I; Gruel, G; Barquinero, J F; Incerti, S; Villagrasa, C

    2014-10-01

    The purpose of this work is to evaluate the influence of the chromatin condensation on the number of direct double-strand break (DSB) damages induced by ions. Two geometries of chromosome territories containing either condensed or decondensed chromatin were implemented as biological targets in the Geant4 Monte Carlo simulation code and proton and alpha irradiation was simulated using the Geant4-DNA processes. A DBSCAN algorithm was used in order to detect energy deposition clusters that could give rise to single-strand breaks or DSBs on the DNA molecule. The results of this study show an increase in the number and complexity of DNA DSBs in condensed chromatin when compared with decondensed chromatin.

  13. Direct contact condensation in packed beds

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yi; Klausner, James F.; Mei, Renwei; Knight, Jessica [Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL 32611 (United States)

    2006-12-15

    A diffusion driven desalination process was recently described where a very effective direct contact condenser with a packed bed is used to condense water vapor out of an air/vapor mixture. A laboratory scale direct contact condenser has been fabricated as a twin tower structure with two stages, co-current and countercurrent. Experiments have been operated in each stage with respective saturated air inlet temperatures of 36, 40 and 43{sup o}C. The temperature and humidity data have been collected at the inlet and exit of the packed bed for different water to air mass flow ratios that vary between 0 and 2.5. A one-dimensional model based on conservation principles has been developed, which predicts the variation of temperature, humidity, and condensation rate through the condenser stages. Agreement between the model and experiments is very good. It is observed that the countercurrent flow stage condensation effectiveness is significantly higher than that for the co-current stage. The condensation heat and mass transfer rates were found to decrease when water blockages occur within the packed bed. Using high-speed digital cinematography, it was observed that this problem can occur at any operating condition, and is dependent on the packing surface wetting characteristics. This observation is used to explain the requirement for two different empirical constants, depending on packing diameter, suggested by Onda for the air side mass transfer coefficient correlation. (author)

  14. Dispensing fuel with aspiration of condensed vapors

    Energy Technology Data Exchange (ETDEWEB)

    Butkovich, M.S.; Strock, D.J.

    1993-08-10

    A vapor recovery process is described, comprising the steps of: fueling a motor vehicle with gasoline by discharging gasoline into a fill opening or filler pipe of a tank of said vehicle through a fuel outlet conduit of a nozzle; emitting gasoline vapors from said tank during said fueling; substantially collecting said vapors during said fueling with a vapor return conduit of said nozzle and passing said vapors through said vapor return conduit in counter current flow relationship to said discharging gasoline in said fuel conduit; conveying said vapors from said vapor return conduit to a vapor return hose; at least some of said vapors condensing to form condensate in said vapor return hose; substantially removing said condensate from said vapor return hose during said fueling with a condensate pickup tube from said nozzle by passing said condensate through said condensate pickup tube in counter current flow relationship to said conveying vapors in said vapor return hose; sensing the presence of gasoline with a liquid sensing tube in said vapor return conduit of said nozzle between inner and outer spouts of said nozzle to detect when said tank of said vehicle is filled with said fuel conduit being within the inner spout of said nozzle; and automatically shutting off said fueling and condensate removing when said liquid sensing tube detects when said tank of said vehicle is filled and fuel enters said vapor return conduit.

  15. Enhancing dropwise condensation through bioinspired wettability patterning.

    Science.gov (United States)

    Ghosh, Aritra; Beaini, Sara; Zhang, Bong June; Ganguly, Ranjan; Megaridis, Constantine M

    2014-11-01

    Dropwise condensation (DWC) heat transfer depends strongly on the maximum diameter (Dmax) of condensate droplets departing from the condenser surface. This study presents a facile technique implemented to gain control of Dmax in DWC within vapor/air atmospheres. We demonstrate how this approach can enhance the corresponding heat transfer rate by harnessing the capillary forces in the removal of the condensate from the surface. We examine various hydrophilic-superhydrophilic patterns, which, respectively, sustain and combine DWC and filmwise condensation on the substrate. The material system uses laser-patterned masking and chemical etching to achieve the desired wettability contrast and does not employ any hydrophobizing agent. By applying alternating straight parallel strips of hydrophilic (contact angle ∼78°) mirror-finish aluminum and superhydrophilic regions (etched aluminum) on the condensing surface, we show that the average maximum droplet size on the less-wettable domains is nearly 42% of the width of the corresponding strips. An overall improvement in the condensate collection rate, up to 19% (as compared to the control case of DWC on mirror-finish aluminum) was achieved by using an interdigitated superhydrophilic track pattern (on the mirror-finish hydrophilic surface) inspired by the vein network of plant leaves. The bioinspired interdigitated pattern is found to outperform the straight hydrophilic-superhydrophilic pattern design, particularly under higher humidity conditions in the presence of noncondensable gases (NCG), a condition that is more challenging for maintaining sustained DWC.

  16. Dynamics of condensation on lubricant impregnated surfaces

    Science.gov (United States)

    Anand, Sushant; Paxson, Adam; Rykaczewski, Konrad; Beysens, Daniel; Varanasi, Kripa

    2013-03-01

    Replacing the filmwise condensation mode with dropwise condensation promises large improvements in heat transfer that will lead to large cost savings in material, water consumption and decreased size of the systems. In this regards, use of superhydrophobic surfaces fabricated by texturing surfaces with nano/microstructures has been shown to lead decrease in contact line pinning of millimetric drops resulting in fast shedding. However, these useful properties are lost during condensation where droplets that nucleate within texture grow by virtue of condensation to large sized droplets while still adhering to the surface. Recently we have shown that liquid impregnated surfaces can overcome many limitations of conventional superhydrophobic surfaces during condensation. Here we discuss aspects related to condensation on lubricant surfaces, such as behavior of growing droplets. We compare the characteristics of droplets condensing on these surfaces with their behavior on conventional un-impregnated superhydrophobic surfaces and show how use of lubricant impregnated surfaces may lead to large enhancement in heat transfer and energy efficiencies.

  17. Fouling computations for optimized condenser cleaning

    Energy Technology Data Exchange (ETDEWEB)

    Wolff, P.J.; March, P.A. [Tennessee Valley Authority, Norris, TN (United States)

    1996-08-01

    Condenser tests are typically performed to evaluate water side fouling levels. Because the water side fouling level is independent of condenser operating conditions, fouling levels determined from a condenser test should also be independent of condenser operating conditions. This study investigates the effect of inlet cooling water temperature on fouling levels computed with an empirical relation presented in the Heat Exchange Institute (HEI) Standard and with the resistance-summation method. These two methods are compared with a simplified mathematical model of a condenser and with actual test data. The comparisons show that the fouling and fouling rate computed by the HEI method are significantly lower than the resistance-summation method for cold condenser circulating water inlet temperatures. The significance of the deviation in fouling rates is then evaluated within the context of an optimized condenser cleaning schedule to determine differences in cleaning schedules and the associated dollar costs of basing cleaning decisions on each of the two methods. 11 refs., 11 figs.

  18. Silicate condensation in Mira variables

    CERN Document Server

    Gail, Hans-Peter; Pucci, Annemarie

    2016-01-01

    We study whether the condensation of silicate dust in Mira envelopes could be caused by cluster formation by the abundant SiO molecules. For a simplified model of the pulsational motions of matter in the the outer layers of a Mira variable which is guided by a numerical model for Mira pulsations, the equations of dust nucleation and growth are solved in the co-moving frame of a fixed mass element. It is assumed that seed particles form by clustering of SiO molecules. The calculation of the nucleation rate is based on the experimental data of Nuth and Donn (1982). The quantity of dust formed is calculated by a moment method and the calculation of radiation pressure on the dusty gas is based on a dirty silicate model. Dust nucleation occurs in the model at the upper culmination of the trajectory of a gas parcel where it stays for a considerable time at low temperatures while subsequent dust growth occurs during the descending part of the motion and continues after the next shock reversed motion. It is found tha...

  19. Stellar matter with pseudoscalar condensates

    Energy Technology Data Exchange (ETDEWEB)

    Andrianov, A.A. [Saint-Petersburg State University, St. Petersburg (Russian Federation); Universitat de Barcelona, Departament d' Estructura i Constituents de la Materia and Institut de Ciencies del Cosmos (ICCUB), Barcelona, Catalonia (Spain); Andrianov, V.A.; Kolevatov, S.S. [Saint-Petersburg State University, St. Petersburg (Russian Federation); Espriu, D. [Universitat de Barcelona, Departament d' Estructura i Constituents de la Materia and Institut de Ciencies del Cosmos (ICCUB), Barcelona, Catalonia (Spain)

    2016-03-15

    In this work we consider how the appearance of gradients of pseudoscalar condensates in dense systems may possibly influence the transport properties of photons in such a medium as well as other thermodynamic characteristics. We adopt the hypothesis that in regions where the pseudoscalar density gradient is large the properties of photons and fermions are governed by the usual lagrangian extended with a Chern-Simons interaction for photons and a constant axial field for fermions. We find that these new pieces in the lagrangian produce non-trivial reflection coefficients both for photons and fermions when entering or leaving a region where the pseudoscalar has a non-zero gradient. A varying pseudoscalar density may also lead to instability of some fermion and boson modes and modify some properties of the Fermi sea. We speculate that some of these modifications could influence the cooling rate of stellar matter (for instance in compact stars) and have other observable consequences. While quantitative results may depend on the precise astrophysical details most of the consequences are quite universal and consideration should be given to this possibility. (orig.)

  20. Baryonic Condensates on the Conifold

    CERN Document Server

    Benna, M K; Klebanov, I R; Benna, Marcus K.; Dymarsky, Anatoly; Klebanov, Igor R.

    2007-01-01

    We provide new evidence for the gauge/string duality between the baryonic branch of the cascading SU(k(M+1)) \\times SU(kM) gauge theory and a family of type IIB flux backgrounds based on warped products of the deformed conifold and R^{3,1}. We show that a Euclidean D5-brane wrapping all six deformed conifold directions can be used to measure the baryon expectation values, and present arguments based on kappa-symmetry and the equations of motion that identify the gauge bundles required to ensure worldvolume supersymmetry of this object. Furthermore, we investigate its coupling to the pseudoscalar and scalar modes associated with the phase and magnitude, respectively, of the baryon expectation value. We find that these massless modes perturb the Dirac-Born-Infeld and Chern-Simons terms of the D5-brane action in a way consistent with our identification of the baryonic condensates. We match the scaling dimension of the baryon operators computed from the D5-brane action with that found in the cascading gauge theor...

  1. Cationic Bolaamphiphiles for Gene Delivery

    Science.gov (United States)

    Tan, Amelia Li Min; Lim, Alisa Xue Ling; Zhu, Yiting; Yang, Yi Yan; Khan, Majad

    2014-05-01

    Advances in medical research have shed light on the genetic cause of many human diseases. Gene therapy is a promising approach which can be used to deliver therapeutic genes to treat genetic diseases at its most fundamental level. In general, nonviral vectors are preferred due to reduced risk of immune response, but they are also commonly associated with low transfection efficiency and high cytotoxicity. In contrast to viral vectors, nonviral vectors do not have a natural mechanism to overcome extra- and intracellular barriers when delivering the therapeutic gene into cell. Hence, its design has been increasingly complex to meet challenges faced in targeting of, penetration of and expression in a specific host cell in achieving more satisfactory transfection efficiency. Flexibility in design of the vector is desirable, to enable a careful and controlled manipulation of its properties and functions. This can be met by the use of bolaamphiphile, a special class of lipid. Unlike conventional lipids, bolaamphiphiles can form asymmetric complexes with the therapeutic gene. The advantage of having an asymmetric complex lies in the different purposes served by the interior and exterior of the complex. More effective gene encapsulation within the interior of the complex can be achieved without triggering greater aggregation of serum proteins with the exterior, potentially overcoming one of the great hurdles faced by conventional single-head cationic lipids. In this review, we will look into the physiochemical considerations as well as the biological aspects of a bolaamphiphile-based gene delivery system.

  2. Dropwise condensation dynamics in humid air

    Science.gov (United States)

    Castillo Chacon, Julian Eduardo

    Dropwise condensation of atmospheric water vapor is important in multiple practical engineering applications. The roles of environmental factors and surface morphology/chemistry on the condensation dynamics need to be better understood to enable efficient water-harvesting, dehumidication, and other psychrometric processes. Systems and surfaces that promote faster condensation rates and self-shedding of condensate droplets could lead to improved mass transfer rates and higher water yields in harvesting applications. The thesis presents the design and construction of an experimental facility that allows visualization of the condensation process as a function of relative humidity. Dropwise condensation experiments are performed on a vertically oriented, hydrophobic surface at a controlled relative humidity and surface subcooling temperature. The distribution and growth of water droplets are monitored across the surface at different relative humidities (45%, 50%, 55%, and 70%) at a constant surface subcooling temperature of 15 °C below the ambient temperature. The droplet growth dynamics exhibits a strong dependency on relative humidity in the early stages during which there is a large population of small droplets on the surface and single droplet growth dominates over coalescence effects. At later stages, the dynamics of droplet growth is insensitive to relative humidity due to the dominance of coalescence effects. The overall volumetric rate of condensation on the surface is also assessed as a function of time and ambient relative humidity. Low relative humidity conditions not only slow the absolute rate of condensation, but also prolong an initial transient regime over which the condensation rate remains significantly below the steady-state value. The current state-of-the-art in dropwise condensation research indicates the need for systematic experimental investigations as a function of relative humidity. The improved understanding of the relative humidity

  3. Quark Virtuality and QCD Vacuum Condensates

    Institute of Scientific and Technical Information of China (English)

    ZHOU Li-Juan; MA Wei-Xing

    2004-01-01

    @@ Based on the Dyson-Schwinger equations (DSEs) in the ‘rainbow' approximation, we investigate the quark virtuality in the vacuum state and quantum-chromodynamics (QCD) vacuum condensates. In particular, we calculate the local quark vacuum condensate and quark-gluon mixed condensates, and then the virtuality of quark. The calculated quark virtualities are λ2u,d = 0.7 GeV2 for u, d quarks, and 2s 1.6 GeV2 for s quark.Our theoretical predictions are consistent with empirical values used in QCD sum rules, and also fit to lattice QCD predictions.

  4. Microscopic theory of equilibrium polariton condensates

    Science.gov (United States)

    Xue, Fei; Wu, Fengcheng; Xie, Ming; Su, Jung-Jung; MacDonald, A. H.

    2016-12-01

    We present a microscopic theory of the equilibrium polariton condensate state of a semiconductor quantum well in a planar optical cavity. The theory accounts for the adjustment of matter excitations to the presence of a coherent photon field, predicts effective polariton-polariton interaction strengths that are weaker and condensate exciton fractions that are smaller than in the commonly employed exciton-photon model, and yields effective Rabi coupling strengths that depend on the detuning of the cavity-photon energy relative to the bare exciton energy. The dressed quasiparticle bands that appear naturally in the theory provide a mechanism for electrical manipulation of polariton condensates.

  5. QCD condensates in ADS/QCD

    DEFF Research Database (Denmark)

    Bechi, Jacopo

    2009-01-01

    This paper focuses on some issues about condensates and renormalization in AdS/QCD models. In particular we consider the consistency of the AdS/QCD approach for scale dependent quantities as the chiral condensate questioned in some recent papers and the 4D meaning of the 5D cosmological constant...... in a model in which the QCD is dual to a 5D gravity theory. We will be able to give some arguments that the cosmological constant is related to the QCD gluon condensate....

  6. Active condensation of water by plants

    Directory of Open Access Journals (Sweden)

    Prokhorov Alexey Anatolievich

    2013-10-01

    Full Text Available This paper is devoted to some peculiarities of water condensation on the surface of plants . Arguments in support of the hypothesis that in decreasing temperature of leaves and shoots below the dew point, the plant can actively condense moisture from the air, increasing the duration of dewfall are presented. Evening dewfall on plant surfaces begins before starting the formation of fog. Morning condensation continues for some time after the air temperature exceeds the dew point . The phenomenon in question is found everywhere, but it is particularly important for plants in arid ecosystems.

  7. The Dynamics of Aerosols in Condensational Scrubbers

    DEFF Research Database (Denmark)

    Johannessen, Jens Tue; Christensen, Jan A.; Simonsen, Ole;

    1997-01-01

    A mathematical model for the simulation of the dynamics of aerosol change in condensational scrubbers and scrubbing condensers is proposed. The model is applicable for packed column gas/liquid contact when plug flow can be assumed. The model is compared with experimental data for particle removal...... in a pilot plant condensational scrubber. The model can satisfactorily predict particle growth and particle deposition by diffusional, convective and inertial mechanisms for a wide range of conditions. The parameters of principal importance for the model precision are identified and a procedure...

  8. Holographic Duality in Condensed Matter Physics

    Science.gov (United States)

    Zaanen, Jan; Liu, Yan; Sun, Ya-Wen; Schalm, Koenraad

    2015-11-01

    Preface; 1. Introduction; 2. Condensed matter: the charted territory; 3. Condensed matter: the challenges; 4. Large N field theories for holography and condensed matter; 5. The AdS/CFT correspondence as computational device: the dictionary; 6. Finite temperature magic: black holes and holographic thermodynamics; 7. Holographic hydrodynamics; 8. Finite density: the Reissner-Nordström black hole and strange metals; 9. Holographic photoemission and the RN metal: the fermions as probes; 10. Holographic superconductivity; 11. Holographic Fermi liquids; 12. Breaking translational invariance; 13. AdS/CMT from the top down; 14. Outlook: holography and quantum matter; References; Index.

  9. Thermally forced transitions of DNA-CTMA complex microstructure

    Science.gov (United States)

    Nizioł, Jacek; Ekiert, Robert; Śniechowski, Maciej; Słomiany, Magdalena; Marzec, Mateusz M.

    2016-06-01

    DNA complexed with amphiphilic cationic surfactants is a new class of optical material. In this work DNA and its complex with cetyltrimetyl ammonium chloride were thermally annealed. X-ray diffractometry revealed irreversible changes of DNA-CTMA microstructure. The new microstucture that appeared in result of the first heating course was stable, despite the further thermal annealing. Agarose gel electrophoresis indicated fundamental differences between thermally treated native DNA and DNA-CTMA complex.

  10. Pool boiling and condensation analysis for a vertical tube bundle condenser

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, W.; Wolf, B., E-mail: zhouw@purdue.edu [Purdue Univ., West Lafayette, Indiana (United States); Revankar, S.T., E-mail: shripad@ecn.purdue.edu [Purdue Univ., West Lafayette, Indiana (United States); POSTECH, Pohang (Korea, Republic of)

    2011-07-01

    An experimental and theoretical study is performed for the steam condensation in a vertical tube bundle passive condenser simulating PCCS condenser in the ESBWR. Four condenser tubes are submerged in a water pool where the heat from the condenser tube is removed through boiling heat transfer. Condenser tubes with a full length/diameter scale are used to obtain the condensation data with various process parameters. The comparison of tube bundle experimental data with the single tube data by both the experiments and models shows that the single tube secondary heat transfer coefficient (HTC) is between 25% - 35% less than what was recorded for the tube bundle, and the tube bundle condensation rates are slightly higher than the data from the single tube test sections due to turbulent mixing effect which increases the condensation heat removal. The turbulent mixing on the secondary side decreases the DT between pool water and condenser tube outer wall, causing an increase in secondary HTC. This increase in secondary HTC thus results in higher condensate mass flow rates. Tube bundle boundary layer model and heat and mass analogy model were then developed for the prediction of the filmwise steam condensation with noncondensable (NC) gas in a vertical tube bundle. The predictions from the models are compared with the experimental data for various complete condensation and through flow conditions and the agreement is satisfactory. The local parameters predicted by the boundary layer model and heat and mass analogy model with tube bundle pool boiling can also be predicted with the axial distance from entrance for different NC gas fractions and system pressures. (author)

  11. Cation distributions on rapidly solidified cobalt ferrite

    Science.gov (United States)

    De Guire, Mark R.; Kalonji, Gretchen; O'Handley, Robert C.

    1990-01-01

    The cation distributions in two rapidly solidified cobalt ferrites have been determined using Moessbauer spectroscopy at 4.2 K in an 8-T magnetic field. The samples were obtained by gas atomization of a Co0-Fe2O3-P2O5 melt. The degree of cation disorder in both cases was greater than is obtainable by cooling unmelted cobalt ferrite. The more rapidly cooled sample exhibited a smaller departure from the equilibrium cation distribution than did the more slowly cooled sample. This result is explained on the basis of two competing effects of rapid solidification: high cooling rate of the solid, and large undercooling.

  12. Cation distributions on rapidly solidified cobalt ferrite

    Science.gov (United States)

    De Guire, Mark R.; Kalonji, Gretchen; O'Handley, Robert C.

    1990-01-01

    The cation distributions in two rapidly solidified cobalt ferrites have been determined using Moessbauer spectroscopy at 4.2 K in an 8-T magnetic field. The samples were obtained by gas atomization of a Co0-Fe2O3-P2O5 melt. The degree of cation disorder in both cases was greater than is obtainable by cooling unmelted cobalt ferrite. The more rapidly cooled sample exhibited a smaller departure from the equilibrium cation distribution than did the more slowly cooled sample. This result is explained on the basis of two competing effects of rapid solidification: high cooling rate of the solid, and large undercooling.

  13. Condensation and localization of the partitioning protein ParB on the bacterial chromosome.

    Science.gov (United States)

    Broedersz, Chase P; Wang, Xindan; Meir, Yigal; Loparo, Joseph J; Rudner, David Z; Wingreen, Ned S

    2014-06-17

    The ParABS system mediates chromosome segregation and plasmid partitioning in many bacteria. As part of the partitioning mechanism, ParB proteins form a nucleoprotein complex at parS sites. The biophysical basis underlying ParB-DNA complex formation and localization remains elusive. Specifically, it is unclear whether ParB spreads in 1D along DNA or assembles into a 3D protein-DNA complex. We show that a combination of 1D spreading bonds and a single 3D bridging bond between ParB proteins constitutes a minimal model for a condensed ParB-DNA complex. This model implies a scaling behavior for ParB-mediated silencing of parS-flanking genes, which we confirm to be satisfied by experimental data from P1 plasmids. Furthermore, this model is consistent with experiments on the effects of DNA roadblocks on ParB localization. Finally, we show experimentally that a single parS site is necessary and sufficient for ParB-DNA complex formation in vivo. Together with our model, this suggests that ParB binding to parS triggers a conformational switch in ParB that overcomes a nucleation barrier. Conceptually, the combination of spreading and bridging bonds in our model provides a surface tension ensuring the condensation of the ParB-DNA complex, with analogies to liquid-like compartments such as nucleoli in eukaryotes.

  14. Recent developments in Bose-Einstein condensation

    Energy Technology Data Exchange (ETDEWEB)

    Kalman, G.

    1997-09-22

    This paper contains viewgraphs on developments on Bose-Einstein condensation. Some topics covered are: strongly coupled coulomb systems; standard response functions of the first and second kind; dynamical mean field theory; quasi localized charge approximation; and the main equations.

  15. Vacuum condensates and `ether-drift' experiments

    OpenAIRE

    Consoli, M.; Pagano, A.; Pappalardo, L.

    2003-01-01

    The idea of a `condensed' vacuum state is generally accepted in modern elementary particle physics. We argue that this should motivate a new generation of precise `ether-drift' experiments with present-day technology.

  16. Condensate of excitations in moving superfluids

    CERN Document Server

    Kolomeitsev, E E

    2016-01-01

    A possibility of the condensation of excitations with a non-zero momentum in rectilinearly moving and rotating superfluid bosonic and fermionic (with Cooper pairing) media is considered in terms of a phenomenological order-parameter functional at zero and non-zero temperature. The results might be applicable to the description of bosonic systems like superfluid $^4$He, ultracold atomic Bose gases, charged pion and kaon condensates in rotating neutron stars, and various superconducting fermionic systems with pairing, like proton and color-superconducting components in compact stars, metallic superconductors, and neutral fermionic systems with pairing, like the neutron component in compact stars and ultracold atomic Fermi gases. Order parameters of the "mother" condensate in the superfluid and the new condensate of excitations, corresponding energy gains, critical temperatures and critical velocities are found.

  17. Cold condensation of dust in the ISM

    CERN Document Server

    Rouillé, Gaël; Krasnokutski, Serge A; Krebsz, Melinda; Henning, Thomas

    2015-01-01

    The condensation of complex silicates with pyroxene and olivine composition at conditions prevailing in molecular clouds has been experimentally studied. For this purpose, molecular species comprising refractory elements were forced to accrete on cold substrates representing the cold surfaces of surviving dust grains in the interstellar medium. The efficient formation of amorphous and homogeneous magnesium iron silicates at temperatures of about 12 K has been monitored by IR spectroscopy. The gaseous precursors of such condensation processes in the interstellar medium are formed by erosion of dust grains in supernova shock waves. In the laboratory, we have evaporated glassy silicate dust analogs and embedded the released species in neon ice matrices that have been studied spectroscopically to identify the molecular precursors of the condensing solid silicates. A sound coincidence between the 10 micron band of the interstellar silicates and the 10 micron band of the low-temperature siliceous condensates can be...

  18. Bimodal condensation silicone elastomers as dielectric elastomers

    DEFF Research Database (Denmark)

    Yu, Liyun; Madsen, Frederikke Bahrt; Skov, Anne Ladegaard

    unimodal refers to that there is one polymer only in the system. As an alternative to unimodal networks there are the bimodal networks where two polymers with significantly different molecular weights are mixed with one crosslinker. [2]Silicone rubber can be divided into condensation type and addition type...... according to the curing reaction. The advantages of condensation silicones compared to addition are the relatively low cost, the curing rate largely being independent of temperature, the excellent adhesion, and the catalyst being nontoxic. [3]In this work, a series of bimodal condensation silicone......, the top and bottom surfaces of the elastomer (7:3) prepared at 23oC and 50% humidity were tested by water contact angle and optical microscope. The results show the bimodal condensation elastomer possesses structural heterogeneity, which may lead to favourable properties for DE applications....

  19. Convection in Condensible-rich Atmospheres

    CERN Document Server

    Ding, Feng

    2016-01-01

    Condensible substances are nearly ubiquitous in planetary atmospheres. For the most familiar case-water vapor in Earth's present climate-the condensible gas is dilute, in the sense that its concentration is everywhere small relative to the noncondensible background gases. A wide variety of important planetary climate problems involve nondilute condensible substances. These include planets near or undergoing a water vapor runaway and planets near the outer edge of the conventional habitable zone, for which CO2 is the condensible. Standard representations of convection in climate models rely on several approximations appropriate only to the dilute limit, while nondilute convection differs in fundamental ways from dilute convection. In this paper, a simple parameterization of convection valid in the nondilute as well as dilute limits is derived and used to discuss the basic character of nondilute convection. The energy conservation properties of the scheme are discussed in detail and are verified in radiative-co...

  20. Dual condensates at finite isospin chemical potential

    CERN Document Server

    Zhang, Zhao

    2015-01-01

    The dual observables as order parameters for center symmetry are tested at finite isospin chemical potential $\\mu_I$ in a Polyakov-loop enhanced chiral model of QCD with physical quark masses. As a counterpart of the dressed Polyakov-loop, the first Fourier moment of pion condensate is introduced for $\\mu_I>{m_\\pi}/{2}$ under the temporal twisted boundary conditions for quarks. We demonstrate that this dual condensate exhibits the similar temperature dependence as the conventional Polyakov-loop. We confirm that its rapid increase with $T$ is driven by the evaporating of pion condensation. On the other hand, the dressed Polyakov-loop shows abnormal thermal behavior, which even decreases with $T$ at low temperatures due to the influence of pion condensate. We thus argue that in QCD the critical temperature extracting from a dual observable may have nothing to do with the quark confinement-deconfinement transition if the quark mass is very small.

  1. Arnold Sommerfeld and Condensed Matter Physics

    Science.gov (United States)

    Joas, Christian; Eckert, Michael

    2017-03-01

    Arnold Sommerfeld (1868-1951), one of the founders of modern theoretical physics and a pioneer of quantum theory, was no condensed matter physicist. He nevertheless played a crucial role for the history of the field. Besides his important contributions to the study of condensed matter systems, among which his seminal electron gas theory of metallic conduction probably stands out, he influenced the field through his very approach to science, through his way of “doing” physics. Sommerfeld's specific style permeated not only his research but also his teaching and his promoting of physics. This has had a lasting influence on the practices of physicists to this day, and not only, but importantly, on those of condensed matter physicists. This article aims to provide a concise account of Sommerfeld's influence on the study of condensed matter systems, with regard to both his research and his practice.

  2. DNA denaturation in ionic solution

    Science.gov (United States)

    Maity, Arghya; Singh, Amar; Singh, Navin

    2016-05-01

    Salt or cations, present in solution play an important role in DNA denaturation and folding kinetics of DNA helix. In this work we study the thermal melting of double stranded DNA (dsDNA) molecule using Peyrard Bishop Dauxois (PBD) model. We modify the potential of H-bonding between the bases of the complimentary strands to introduce the salt and solvent effect. We choose different DNA sequences having different contents of GC pairs and calculate the melting temperatures. The melting temperature increases logarithmically with the salt concentration of the solution. The more GC base pairs in the chain enhance the stability of DNA chain at a fix salt concentration. The obtained results are in good accordance with experimental findings.

  3. Essay: fifty years of condensed matter physics.

    Science.gov (United States)

    Cohen, Marvin L

    2008-12-19

    Since the birth of Physical Review Letters fifty years ago, condensed matter physics has seen considerable growth, and both the journal and the field have flourished during this period. In this essay, I begin with some general comments about condensed matter physics and then give some personal views on the conceptual development of the field and list some highlights. The focus is mostly on theoretical developments.

  4. Gaugino condensation, duality and supersymmetry breaking

    CERN Document Server

    Quevedo, Fernando

    1995-01-01

    The status of gaugino condensation in low-energy string theory is reviewed. Emphasis is given to the determination of the efective action below condensation scale in terms of the 2PI and Wilson actions. We illustrate how the different perturbative duality symmetries survive this simple nonperturbative phenomenon, providing evidence for the believe that these are exact nonperturbative symmetries of string theory. Consistency with T duality lifts the moduli degeneracy. The B_{\\mu\

  5. Experimental simulation of the condensation and metamorphism of seasonal CO2 condensates under martian conditions.

    Science.gov (United States)

    Grisolle, F.; Schmitt, B.; Beck, P.; Philippe, S.; Brissaud, O.

    2014-04-01

    An experimental set-up, CARBON-IR, has been developed in order to perform the condensation and metamorphism of CO2 condensates in various controlled martian conditions at, or out of, equilibrium. The sample texture is monitored and near-infrared reflectance spectra are recorded. We present a first set of experiments aimed to simulate the formation of compact translucent slabs by condensation of CO2 gas, the metamorphism of CO2 snow, as well as their sublimation.

  6. Cationic ruthenium alkylidene catalysts bearing phosphine ligands.

    Science.gov (United States)

    Endo, Koji; Grubbs, Robert H

    2016-02-28

    The discovery of highly active catalysts and the success of ionic liquid immobilized systems have accelerated attention to a new class of cationic metathesis catalysts. We herein report the facile syntheses of cationic ruthenium catalysts bearing bulky phosphine ligands. Simple ligand exchange using silver(i) salts of non-coordinating or weakly coordinating anions provided either PPh3 or chelating Ph2P(CH2)nPPh2 (n = 2 or 3) ligated cationic catalysts. The structures of these newly reported catalysts feature unique geometries caused by ligation of the bulky phosphine ligands. Their activities and selectivities in standard metathesis reactions were also investigated. These cationic ruthenium alkylidene catalysts reported here showed moderate activity and very similar stereoselectivity when compared to the second generation ruthenium dichloride catalyst in ring-closing metathesis, cross metathesis, and ring-opening metathesis polymerization assays.

  7. Wettability Patterning for Enhanced Dropwise Condensation

    Science.gov (United States)

    Ghosh, Aritra; Ganguly, Ranjan; Megaridis, Constantine

    2014-11-01

    Dropwise condensation (DwC), in order to be sustainable, requires removal of the condensate droplets. This removal is frequently facilitated by gravity. The rate of DwC heat transfer depends strongly on the maximum departing droplet diameter. Based on wettability patterning, we present a facile technique designed to control the maximum droplet size in DwC within vapor/air atmospheres, and demonstrate how this approach can be used to enhance the corresponding heat transfer rate. We examine various hydrophilic-superhydrophilic patterns, which, respectively sustain DwC and filmwise (FwC) condensation on the substrate. The fabrication method does notemploy any hydrophobizing agent. By juxtaposing parallel lines of hydrophilic (CA ~ 78°) and superhydrophilic (CA ~ 0°) regions on the condensing surface, we create alternating domains of DwC and FwC. The average droplet size on the DwC domain is reduced by ~ 60% compared to the theoretical maximum, which corresponds to the line width. We compare heat transfer rate between unpatternend DwC surfaces and patterned DwC surfaces. Even after sacrificing 40% of condensing area, we achieve up to 20% improvement in condensate collection rate using an interdigitated superhydrophilic pattern, inspired by the vein network of plant leaves. The bioinspired interdigitated pattern is found to outperform the straight hydrophilic-superhydrophilic pattern, particularly under higher vapor loadings in an air/vapor ambient atmosphere. NSF STTR Grant 1331817 via NBD Nano.

  8. Numerical simulation of condensation on structured surfaces.

    Science.gov (United States)

    Fu, Xiaowu; Yao, Zhaohui; Hao, Pengfei

    2014-11-25

    Condensation of liquid droplets on solid surfaces happens widely in nature and industrial processes. This phase-change phenomenon has great effect on the performance of some microfluidic devices. On the basis of micro- and nanotechnology, superhydrophobic structured surfaces can be well-fabricated. In this work, the nucleating and growth of droplets on different structured surfaces are investigated numerically. The dynamic behavior of droplets during the condensation is simulated by the multiphase lattice Boltzmann method (LBM), which has the ability to incorporate the microscopic interactions, including fluid-fluid interaction and fluid-surface interaction. The results by the LBM show that, besides the chemical properties of surfaces, the topography of structures on solid surfaces influences the condensation process. For superhydrophobic surfaces, the spacing and height of microridges have significant influence on the nucleation sites. This mechanism provides an effective way for prevention of wetting on surfaces in engineering applications. Moreover, it suggests a way to prevent ice formation on surfaces caused by the condensation of subcooled water. For hydrophilic surfaces, however, microstructures may be submerged by the liquid films adhering to the surfaces. In this case, microstructures will fail to control the condensation process. Our research provides an optimized way for designing surfaces for condensation in engineering systems.

  9. Cation locations and dislocations in zeolites

    Science.gov (United States)

    Smith, Luis James

    The focus of this dissertation is the extra-framework cation sites in a particular structural family of zeolites, chabazite. Cation sites play a particularly important role in the application of these sieves for ion exchange, gas separation, catalysis, and, when the cation is a proton, acid catalysis. Structural characterization is commonly performed through the use of powder diffraction and Rietveld analysis of powder diffraction data. Use of high-resolution nuclear magnetic resonance, in the study of the local order of the various constituent nuclei of zeolites, complements well the long-range order information produced by diffraction. Recent developments in solid state NMR techniques allow for increased study of disorder in zeolites particularly when such phenomena test the detection limits of diffraction. These two powerful characterization techniques, powder diffraction and NMR, offer many insights into the complex interaction of cations with the zeolite framework. The acids site locations in SSZ-13, a high silica chabazite, and SAPO-34, a silicoaluminophosphate with the chabazite structure, were determined. The structure of SAPO-34 upon selective hydration was also determined. The insensitivity of X-rays to hydrogen was avoided through deuteration of the acid zeolites and neutron powder diffraction methods. Protons at inequivalent positions were found to have different acid strengths in both SSZ-13 and SAPO-34. Other light elements are incorporated into zeolites in the form of extra-framework cations, among these are lithium, sodium, and calcium. Not amenable by X-ray powder diffraction methods, the positions of such light cations in fully ion-exchanged versions of synthetic chabazite were determined through neutron powder diffraction methods. The study of more complex binary cation systems were conducted. Powder diffraction and solid state NMR methods (MAS, MQMAS) were used to examine cation site preferences and dislocations in these mixed-akali chabazites

  10. Condensation of the air-steam mixture in a vertical tube condenser

    Science.gov (United States)

    Havlík, Jan; Dlouhý, Tomáš

    2016-03-01

    This paper deals with the condensation of water vapour in the presence of non-condensable air. Experimental and theoretical solutions of this problem are presented here. A heat exchanger for the condensation of industrial waste steam containing infiltrated air was designed. The condenser consists of a bundle of vertical tubes in which the steam condenses as it flows downwards with cooling water flowing outside the tubes in the opposite direction. Experiments with pure steam and with mixtures of steam with added air were carried out to find the dependence of the condensation heat transfer coefficient (HTC) on the air concentration in the steam mixture. The experimental results were compared with the theoretical formulas describing the cases. The theoretical determination of the HTC is based on the Nusselt model of steam condensation on a vertical wall, where the analogy of heat and mass transfer is used to take into account the behaviour of air in a steam mixture during the condensation process. The resulting dependencies obtained from the experiments and obtained from the theoretical model have similar results. The significant decrease in the condensation HTC, which begins at very low air concentrations in a steam mixture, was confirmed.

  11. Condensation of the air-steam mixture in a vertical tube condenser

    Directory of Open Access Journals (Sweden)

    Havlík Jan

    2016-01-01

    Full Text Available This paper deals with the condensation of water vapour in the presence of non-condensable air. Experimental and theoretical solutions of this problem are presented here. A heat exchanger for the condensation of industrial waste steam containing infiltrated air was designed. The condenser consists of a bundle of vertical tubes in which the steam condenses as it flows downwards with cooling water flowing outside the tubes in the opposite direction. Experiments with pure steam and with mixtures of steam with added air were carried out to find the dependence of the condensation heat transfer coefficient (HTC on the air concentration in the steam mixture. The experimental results were compared with the theoretical formulas describing the cases. The theoretical determination of the HTC is based on the Nusselt model of steam condensation on a vertical wall, where the analogy of heat and mass transfer is used to take into account the behaviour of air in a steam mixture during the condensation process. The resulting dependencies obtained from the experiments and obtained from the theoretical model have similar results. The significant decrease in the condensation HTC, which begins at very low air concentrations in a steam mixture, was confirmed.

  12. Changes in DNA topology during spermatogenesis.

    Science.gov (United States)

    Risley, M S; Einheber, S; Bumcrot, D A

    1986-01-01

    DNA topology in histone- and protamine-depleted nuclei (nucleoids) from somatic cells, sperm, and spermatogenic cells was studied to determine if the superhelical configuration of DNA looped domains is altered during spermatogenesis. The expansion and contraction of nucleoid DNA was measured with a fluorescence microscope following exposure of nucleoids to different concentrations of ethidium bromide (EB). Nucleoids from Xenopus laevis erythrocytes, primary spermatocytes, and round spermatids, and from Rana catesbeiana sperm all exhibited a biphasic change (condensed-relaxed-condensed) in size as a function of exposure to increasing concentrations (0.5-100 micrograms/ml) of EB, indicating that they contain negatively supercoiled DNA. In contrast, DNA in sperm nucleoids from Xenopus laevis and Bufo fowleri was relaxed and expanded at low (0.5-6 micrograms/ml) EB concentrations, but became gradually condensed as the EB concentration was increased (6-100 micrograms/ml). Nucleoids prepared from all cell types retained the general shape of the nucleus regardless of the superhelical configuration of the nucleoid DNA. Sperm nucleoid DNA condensed by 100 micrograms/ml EB was relaxed by exposure to UV light, DNase I, proteinase K, or 4 M urea, but not by RNase A or 10 mM dithiothreitol. These results demonstrate that the DNA in sperm nucleoids is constrained in domains of supercoiling by nonbasic nuclear proteins. Negatively supercoiled DNA is present in nucleoids from cells with a full complement of histones, including Rana sperm, but not in nucleoids from Xenopus and Bufo sperm in which histones are replaced by "intermediate-type" protamines. Histone replacement in these species, therefore, is accompanied by unfolding of nucleosomal DNA and active removal of the negative supercoils. Results presented also suggest an important role for the nonbasic nuclear proteins of sperm in the morphogenesis of the nucleus and the arrangement of DNA.

  13. Cationized Carbohydrate Gas-Phase Fragmentation Chemistry

    Science.gov (United States)

    Bythell, Benjamin J.; Abutokaikah, Maha T.; Wagoner, Ashley R.; Guan, Shanshan; Rabus, Jordan M.

    2016-11-01

    We investigate the fragmentation chemistry of cationized carbohydrates using a combination of tandem mass spectrometry, regioselective labeling, and computational methods. Our model system is D-lactose. Barriers to the fundamental glyosidic bond cleavage reactions, neutral loss pathways, and structurally informative cross-ring cleavages are investigated. The most energetically favorable conformations of cationized D-lactose were found to be similar. In agreement with the literature, larger group I cations result in structures with increased cation coordination number which require greater collision energy to dissociate. In contrast with earlier proposals, the B n -Y m fragmentation pathways of both protonated and sodium-cationized analytes proceed via protonation of the glycosidic oxygen with concerted glycosidic bond cleavage. Additionally, for the sodiated congeners our calculations support sodiated 1,6-anhydrogalactose B n ion structures, unlike the preceding literature. This affects the subsequent propensity of formation and prediction of B n /Y m branching ratio. The nature of the anomeric center (α/β) affects the relative energies of these processes, but not the overall ranking. Low-energy cross-ring cleavages are observed for the metal-cationized analytes with a retro-aldol mechanism producing the 0,2 A 2 ion from the sodiated forms. Theory and experiment support the importance of consecutive fragmentation processes, particularly for the protonated congeners at higher collision energies.

  14. Cationized Carbohydrate Gas-Phase Fragmentation Chemistry

    Science.gov (United States)

    Bythell, Benjamin J.; Abutokaikah, Maha T.; Wagoner, Ashley R.; Guan, Shanshan; Rabus, Jordan M.

    2017-04-01

    We investigate the fragmentation chemistry of cationized carbohydrates using a combination of tandem mass spectrometry, regioselective labeling, and computational methods. Our model system is D-lactose. Barriers to the fundamental glyosidic bond cleavage reactions, neutral loss pathways, and structurally informative cross-ring cleavages are investigated. The most energetically favorable conformations of cationized D-lactose were found to be similar. In agreement with the literature, larger group I cations result in structures with increased cation coordination number which require greater collision energy to dissociate. In contrast with earlier proposals, the B n -Y m fragmentation pathways of both protonated and sodium-cationized analytes proceed via protonation of the glycosidic oxygen with concerted glycosidic bond cleavage. Additionally, for the sodiated congeners our calculations support sodiated 1,6-anhydrogalactose B n ion structures, unlike the preceding literature. This affects the subsequent propensity of formation and prediction of B n /Y m branching ratio. The nature of the anomeric center (α/β) affects the relative energies of these processes, but not the overall ranking. Low-energy cross-ring cleavages are observed for the metal-cationized analytes with a retro-aldol mechanism producing the 0,2 A 2 ion from the sodiated forms . Theory and experiment support the importance of consecutive fragmentation processes, particularly for the protonated congeners at higher collision energies.

  15. Primes, Geometry and Condensed Matter

    Directory of Open Access Journals (Sweden)

    Al Rabeh R. H.

    2009-07-01

    Full Text Available Fascination with primes dates back to the Greeks and before. Primes are named by some "the elementary particles of arithmetic" as every nonprime integer is made of a unique set of primes. In this article we point to new connections between primes, geometry and physics which show that primes could be called "the elementary particles of physics" too. This study considers the problem of closely packing similar circles/spheres in 2D/3D space. This is in effect a discretization process of space and the allowable number in a pack is found to lead to some unexpected cases of prime configurations which is independent of the size of the constituents. We next suggest that a non-prime can be considered geometrically as a symmetric collection that is separable (factorable into similar parts- six is two threes or three twos for example. A collection that has no such symmetry is a prime. As a result, a physical prime aggregate is more difficult to split symmetrically resulting in an inherent stability. This "number/physical" stability idea applies to bigger collections made from smaller (prime units leading to larger stable prime structures in a limitless scaling up process. The distribution of primes among numbers can be understood better using the packing ideas described here and we further suggest that differing numbers (and values of distinct prime factors making a nonprime collection is an important factor in determining the probability and method of possible and subsequent disintegration. Disintegration is bound by energy conservation and is closely related to symmetry by Noether theorems. Thinking of condensed matter as the packing of identical elements, we examine plots of the masses of chemical elements of the periodic table, and also those of the elementary particles of physics, and show that prime packing rules seem to play a role in the make up of matter. The plots show convincingly that the growth of prime numbers and that of the masses of

  16. Primes, Geometry and Condensed Matter

    Directory of Open Access Journals (Sweden)

    Al Rabeh R. H.

    2009-07-01

    Full Text Available Fascination with primes dates back to the Greeks and before. Primes are named by some “the elementary particles of arithmetic” as every nonprime integer is made of a unique set of primes. In this article we point to new connections between primes, geometry and physics which show that primes could be called “the elementary particles of physics” too. This study considers the problem of closely packing similar circles / spheres in 2D / 3D space. This is in effect a discretization process of space and the allowable num- ber in a pack is found to lead to some unexpected cases of prime configurations which is independent of the size of the constituents. We next suggest that a non-prime can be considered geometrically as a symmetric collection that is separable (factorable into similar parts- six is two threes or three twos for example. A collection that has no such symmetry is a prime. As a result, a physical prime aggregate is more difficult to split symmetrically resulting in an inherent stability. This “number / physical” stability idea applies to bigger collections made from smaller (prime units leading to larger sta- ble prime structures in a limitless scaling up process. The distribution of primes among numbers can be understood better using the packing ideas described here and we further suggest that differing numbers (and values of distinct prime factors making a nonprime collection is an important factor in determining the probability and method of possible and subsequent disintegration. Disintegration is bound by energy conservation and is closely related to symmetry by Noether theorems. Thinking of condensed matter as the packing of identical elements, we examine plots of the masses of chemical elements of the periodic table, and also those of the elementary particles of physics, and show that prime packing rules seem to play a role in the make up of matter. The plots show con- vincingly that the growth of prime numbers and that

  17. UV-Vis Action Spectroscopy Reveals a Conformational Collapse in Hydrogen-Rich Dinucleotide Cation Radicals.

    Science.gov (United States)

    Korn, Joseph A; Urban, Jan; Dang, Andy; Nguyen, Huong T H; Tureček, František

    2017-09-07

    We report the generation of deoxyriboadenosine dinucleotide cation radicals by gas-phase electron transfer to dinucleotide dications and their noncovalent complexes with crown ether ligands. Stable dinucleotide cation radicals of a novel hydrogen-rich type were generated and characterized by tandem mass spectrometry and UV-vis photodissociation (UVPD) action spectroscopy. Electron structure theory analysis indicated that upon electron attachment the dinucleotide dications underwent a conformational collapse followed by intramolecular proton migrations between the nucleobases to give species whose calculated UV-vis absorption spectra matched the UVPD action spectra. Hydrogen-rich cation radicals generated from chimeric riboadenosine 5'-diesters gave UVPD action spectra that pointed to novel zwitterionic structures consisting of aromatic π-electron anion radicals intercalated between stacked positively charged adenine rings. Analogies with DNA ionization are discussed.

  18. Preparação e propriedades de zeólitas faujasita contendo cátions amônio Preparation and properties of faujasite zeolites containing ammonium cations

    Directory of Open Access Journals (Sweden)

    Karina Arruda Almeida

    2010-01-01

    Full Text Available Sodium faujasite zeolites with Si/Al ratio of 1.4 and 2.5 were exchanged with methylammonium cations. The influence of framework aluminum and ion exchange degree in their basic properties were evaluated. These properties were assessed in the Knoevenagel catalytic condensation. The sodium ion exchange was restricted to the supercavity and the exchange degree depended on the cation volume and on the Si/Al ratio. The higher catalytic activity is achieved for the zeolite with the lower Si/Al ratio exchanged with the monomethylammonium cation. The best performance of this catalyst is attributed to the higher basicity in combination with elevated micropore volume.

  19. Cationic nanoparticles with quaternary ammonium-functionalized PLGA-PEG-based copolymers for potent gene transfection

    Science.gov (United States)

    Wang, Yan-Hsung; Fu, Yin-Chih; Chiu, Hui-Chi; Wang, Chau-Zen; Lo, Shao-Ping; Ho, Mei-Ling; Liu, Po-Len; Wang, Chih-Kuang

    2013-11-01

    The objective of the present work was to develop new cationic nanoparticles (cNPs) with amphiphilic cationic copolymers for the delivery of plasmid DNA (pDNA). Cationic copolymers were built on the synthesis of quaternary ammonium salt compounds from diethylenetriamine (DETA) to include the positively charged head group and amphiphilic multi-grafts. PLGA- phe-PEG- qDETA (PPD), phe-PEG- qDETA-PLGA (PDP), and PLGA- phe-PEG- qDETA-PLGA (PPDP) cationic copolymers were created by this moiety of DETA quaternary ammonium, heterobifunctional polyethylene glycol (COOH-PEG-NH2), phenylalanine ( phe), and poly(lactic- co-glycolic acid) (PLGA). These new cNPs were prepared by the water miscible solvent displacement method. They exhibit good pDNA binding ability, as shown in a retardation assay that occurred at a particle size of 217 nm. The zeta potential was approximately +21 mV when the cNP concentration was 25 mg/ml. The new cNPs also have a better buffering capacity than PLGA NPs. However, the pDNA binding ability was demonstrated starting at a weight ratio of approximately 6.25 cNPs/pDNA. Gene transfection results showed that these cNPs had transfection effects similar to those of Lipofectamine 2000 in 293T cells. Furthermore, cNPs can also transfect human adipose-derived stem cells. The results indicate that the newly developed cNP is a promising candidate for a novel gene delivery vehicle.

  20. Cationic nanoparticles with quaternary ammonium-functionalized PLGA–PEG-based copolymers for potent gene transfection

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yan-Hsung [Kaohsiung Medical University, School of Dentistry, College of Dental Medicine (China); Fu, Yin-Chih [Kaohsiung Medical University, Graduate Institute of Medicine, College of Medicine (China); Chiu, Hui-Chi [Kaohsiung Medical University, Department of Medicinal and Applied Chemistry, College of Life Science (China); Wang, Chau-Zen [Kaohsiung Medical University, Department of Physiology, College of Medicine (China); Lo, Shao-Ping [Kaohsiung Medical University, Department of Medicinal and Applied Chemistry, College of Life Science (China); Ho, Mei-Ling [Kaohsiung Medical University, Department of Physiology, College of Medicine (China); Liu, Po-Len [Kaohsiung Medical University, Department of Respiratory Therapy, College of Medicine (China); Wang, Chih-Kuang, E-mail: ckwang@kmu.edu.tw [Kaohsiung Medical University, Department of Medicinal and Applied Chemistry, College of Life Science (China)

    2013-11-15

    The objective of the present work was to develop new cationic nanoparticles (cNPs) with amphiphilic cationic copolymers for the delivery of plasmid DNA (pDNA). Cationic copolymers were built on the synthesis of quaternary ammonium salt compounds from diethylenetriamine (DETA) to include the positively charged head group and amphiphilic multi-grafts. PLGA-phe-PEG-qDETA (PPD), phe-PEG-qDETA-PLGA (PDP), and PLGA-phe-PEG-qDETA-PLGA (PPDP) cationic copolymers were created by this moiety of DETA quaternary ammonium, heterobifunctional polyethylene glycol (COOH-PEG-NH{sub 2}), phenylalanine (phe), and poly(lactic-co-glycolic acid) (PLGA). These new cNPs were prepared by the water miscible solvent displacement method. They exhibit good pDNA binding ability, as shown in a retardation assay that occurred at a particle size of ∼217 nm. The zeta potential was approximately +21 mV when the cNP concentration was 25 mg/ml. The new cNPs also have a better buffering capacity than PLGA NPs. However, the pDNA binding ability was demonstrated starting at a weight ratio of approximately 6.25 cNPs/pDNA. Gene transfection results showed that these cNPs had transfection effects similar to those of Lipofectamine 2000 in 293T cells. Furthermore, cNPs can also transfect human adipose-derived stem cells. The results indicate that the newly developed cNP is a promising candidate for a novel gene delivery vehicle.

  1. Enhanced tubes for steam condensers. Volume 1, Summary of condensation and fouling; Volume 2, Detailed study of steam condensation

    Energy Technology Data Exchange (ETDEWEB)

    Webb, R.L.; Chamra, L.; Jaber, H.

    1992-02-01

    Electric utility steam condensers typically use plain tubes made of titanium, stainless steel, or copper alloys. Approximately two-thirds of the total thermal resistance is on the water side of the plain tube. This program seeks to conceive and develop a tube geometry that has special enhancement geometries on the tube (water) side and the steam (shell) side. This ``enhanced`` tube geometry, will provide increased heat transfer coefficients. The enhanced tubes will allow the steam to condense at a lower temperature. The reduced condensing temperature will reduce the turbine heat rate, and increase the plant peak load capability. Water side fouling and fouling control is a very important consideration affecting the choice of the tube side enhancement. Hence, we have consciously considered fouling potential in our selection of the tube side surface geometry. Using appropriate correlations and theoretical models, we have designed condensation and water side surface geometries that will provide high performance and be cleanable using sponge ball cleaning. Commercial tube manufacturers have made the required tube geometries for test purposes. The heat transfer test program includes measurement of the condensation and water side heat transfer coefficients. Fouling tests are being run to measure the waterside fouling resistance, and to the test the ability of the sponge ball cleaning system to clean the tubes.

  2. Dropwise condensation on superhydrophobic surfaces with two-tier roughness

    Science.gov (United States)

    Chen, Chuan-Hua; Cai, Qingjun; Tsai, Chialun; Chen, Chung-Lung; Xiong, Guangyong; Yu, Ying; Ren, Zhifeng

    2007-04-01

    Dropwise condensation can enhance heat transfer by an order of magnitude compared to film condensation. Superhydrophobicity appears ideal to promote continued dropwise condensation which requires rapid removal of condensate drops; however, such promotion has not been reported on engineered surfaces. This letter reports continuous dropwise condensation on a superhydrophobic surface with short carbon nanotubes deposited on micromachined posts, a two-tier texture mimicking lotus leaves. On such micro-/nanostructured surfaces, the condensate drops prefer the Cassie state which is thermodynamically more stable than the Wenzel state. With a hexadecanethiol coating, superhydrophobicity is retained during and after condensation and rapid drop removal is enabled.

  3. Cell compatible arginine containing cationic polymer: one-pot synthesis and preliminary biological assessment.

    Science.gov (United States)

    Zavradashvili, Nino; Memanishvili, Tamar; Kupatadze, Nino; Baldi, Lucia; Shen, Xiao; Tugushi, David; Wandrey, Christine; Katsarava, Ramaz

    2014-01-01

    Synthetic cationic polymers are of interest as both nonviral vectors for intracellular gene delivery and antimicrobial agents. For both applications synthetic polymers containing guanidine groups are of special interest since such kind of organic compounds/polymers show a high transfection potential along with antibacterial activity. It is important that the delocalization of the positive charge of the cationic group in guanidine significantly decreases the toxicity compared to the ammonium functionality. One of the most convenient ways for incorporating guanidine groups is the synthesis of polymers composed of the amino acid arginine (Arg) via either application of Arg-based monomers or chemical modification of polymers with derivatives of Arg. It is also important to have biodegradable cationic polymers that will be cleared from the body after their function as transfection or antimicrobial agent is fulfilled. This chapter deals with a two-step/one-pot synthesis of a new biodegradable cationic polymer-poly(ethylene malamide) containing L-arginine methyl ester covalently attached to the macrochains in β-position of the malamide residue via the α-amino group. The goal cationic polymer was synthesized by in situ interaction of arginine methyl ester dihydrochloride with intermediary poly(ethylene epoxy succinimide) formed by polycondensation of di-p-nitrophenyl-trans-epoxy succinate with ethylenediamine. The cell compatibility study with Chinese hamster ovary (CHO) and insect Schneider 2 cells (S2) within the concentration range of 0.02-500 mg/mL revealed that the new polymer is not cytotoxic. It formed nanocomplexes with pDNA (120-180 nm in size) at low polymer/DNA weight ratios (WR = 5-10). A preliminarily transfection efficiency of the Arg-containing new cationic polymer was assessed using CHO, S2, H5, and Sf9 cells.

  4. Vortices in a Bose-Einstein Condensate

    Science.gov (United States)

    Haljan, Paul C.

    2004-05-01

    Since the advent of Bose-Einstein condensation in the dilute alkalis, there has been considerable interest in observing effects in atomic condensates akin to the hallmark effects associated with superfluidity and superconductivity. In particular, the study of quantized vortices and vortex lattices represents an important connection between the traditional ``super" systems such as liquid Helium and this new atomic system. This thesis explores some of the first vortex experiments in a condensate of magnetically trapped Rubidium-87. Single vortex lines and rings are created using a wavefunction engineering technique, which is an ideal starting point to study the dynamical behavior of vortices within the condensate. An entirely different approach of ``intrinsic nucleation" has been developed to create rapidly rotating condensates with large amounts of vorticity. A novel variation of forced evaporation is used to simultaneously cool and spin up an ultracold gas. In this way, condensates can be formed that are rotating in excess of 95% of the centrifugal limit and contain large, extraordinarily regular lattices of well over 100 vortices. Direct detection of the vortex cores makes it possible to study the microscopic structure of the vortex arrangements both at equilibrium and under dynamical conditions where severe applied stresses distort the lattice far from its equilibrium configuration. In conclusion, the techniques developed in this work have helped to open up a new area of rotating condensate physics and, in the future, may lead to regimes of extreme rotation and quantum Hall physics. This work was performed at the University of Colorado, Boulder, under the supervision of Prof. Eric A. Cornell.

  5. Syntheses and Photodynamic Activity of Pegylated Cationic Zn(II-Phthalocyanines in HEp2 Cells

    Directory of Open Access Journals (Sweden)

    Benson G. Ongarora, Xiaoke Hu, Susan D. Verberne-Sutton, Jayne C. Garno, M. Graça H. Vicente

    2012-01-01

    Full Text Available Di-cationic Zn(II-phthalocyanines (ZnPcs are promising photosensitizers for the photodynamic therapy (PDT of cancers and for photoinactivation of viruses and bacteria. Pegylation of photosensitizers in general enhances their water-solubility and tumor cell accumulation. A series of pegylated di-cationic ZnPcs were synthesized from conjugation of a low molecular weight PEG group to a pre-formed Pc macrocycle, or by mixed condensation involving a pegylated phthalonitrile. All pegylated ZnPcs were highly soluble in polar organic solvents but were insoluble in water; they have intense Q absorptions centered at 680 nm and fluorescence quantum yields of ca. 0.2 in DMF. The non-pegylated di-cationic ZnPc 6a formed large aggregates, which were visualized by atomic force microscopy. The cytotoxicity, cellular uptake and subcellular distribution of all cationic ZnPcs were investigated in human carcinoma HEp2 cells. The most phototoxic compounds were found to be the α-substituted Pcs. Among these, Pcs 4a and 16a were the most effective (IC50 ca. 10 μM at 1.5 J/cm2, in part due to the presence of a PEG group and the two positive charges in close proximity (separated by an ethylene group in these macrocycles. The β-substituted ZcPcs 6b and 4b accumulated the most within HEp2 cells but had low photocytoxicity (IC50 > 100 μM at 1.5 J/cm2, possibly as a result of their lower electron density of the ring and more extended conformations compared with the α-substituted Pcs. The results show that the charge distribution about the Pc macrocycle and the intracellular localization of the cationic ZnPcs mainly determine their photodynamic activity.

  6. Next generation macrocyclic and acyclic cationic lipids for gene transfer: Synthesis and in vitro evaluation.

    Science.gov (United States)

    Jubeli, Emile; Maginty, Amanda B; Abdul Khalique, Nada; Raju, Liji; Abdulhai, Mohamad; Nicholson, David G; Larsen, Helge; Pungente, Michael D; Goldring, William P D

    2015-10-01

    Previously we reported the synthesis and in vitro evaluation of four novel, short-chain cationic lipid gene delivery vectors, characterized by acyclic or macrocyclic hydrophobic regions composed of, or derived from, two 7-carbon chains. Herein we describe a revised synthesis of an expanded library of related cationic lipids to include extended chain analogues, their formulation with plasmid DNA (pDNA) and in vitro delivery into Chinese hamster ovarian (CHO-K1) cells. The formulations were evaluated against each other based on structural differences in the hydrophobic domain and headgroup. Structurally the library is divided into four sets based on lipids derived from two 7- or two 11-carbon hydrophobic chains, C7 and C11 respectively, which possess either a dimethylamine or a trimethylamine derived headgroup. Each set includes four cationic lipids based on an acyclic or macrocyclic, saturated or unsaturated hydrophobic domain. All lipids were co-formulated with the commercial cationic lipid 1,2-dimyristoyl-sn-glycero-3-ethylphosphocholine (EPC) in a 1:1 molar ratio, along with one of two distinct neutral co-lipids, cholesterol or 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) in an overall cationic-to-neutral lipid molar ratio of 3:2. Binding of lipid formulations with DNA, and packing morphology associated with the individual lipid-DNA complexes were characterized by gel electrophoresis and small angle X-ray diffraction (SAXD), respectively. As a general trend, lipoplex formulations based on mismatched binary cationic lipids, composed of a shorter C7 lipid and the longer lipid EPC (C14), were generally associated with higher transfection efficiency and lower cytotoxicity than their more closely matched C11/EPC binary lipid formulation counterparts. Furthermore, the cyclic lipids gave transfection levels as high as or greater than their acyclic counterparts, and formulations with cholesterol exhibited higher transfection and lower cytotoxicity than those

  7. Rapid and quantitative quality control of microarrays using cationic nanoparticles.

    Science.gov (United States)

    Sun, Ye; Fan, Wenhua; McCann, Michael P; Golovlev, Val

    2009-02-15

    The fabrication quality of microarrays significantly influences the accuracy and reproducibility of microarray experiments. In this report, we present a simple and fast quality control (QC) method for spotted oligonucleotide and cDNA microarrays. It employs a nonspecific electrostatic interaction of colloidal gold nanoparticles with the chemical groups of DNA molecules and other biomolecules immobilized on the microarray surface that bear positive or negative charges. An inexpensive flatbed scanner is used to visualize and quantify the binding of cationic gold particles to the anionic DNA probes on the microarray surface. An image analysis software was designed to assess the various parameters of the array spots including spot intensity, shape and array homogeneity, calculate the overall array quality score, and save the detailed array quality report in an Excel file. The gold staining technique is fast and sensitive. It can be completed in 10 min and detect less than 1% of the probe amount commonly recommended for microarrays. Compared to the current microarray QC method that utilizes the hybridization of probes with short random sequence oligonucleotides labeled with fluorophore, our gold staining method requires less time for the analysis, reduces the reagent cost, and eliminates the need for the expensive laser scanner.

  8. Knot Solitons in Spinor Bose-Einstein Condensates

    Science.gov (United States)

    Hall, David; Ray, Michael; Tiurev, Konstantin; Ruokokoski, Emmi; Gheorghe, Andrei Horia; Möttönen, Mikko

    2016-05-01

    Knots are familiar entities that appear at a captivating nexus of art, technology, mathematics and science. Following a lengthy period of theoretical investigation and development, they have recently attracted great experimental interest in classical contexts ranging from knotted DNA and nanostructures to vortex knots in fluids. We demonstrate here the controlled creation and detection of knot solitons in the quantum-mechanical order parameter of a spinor Bose-Einstein condensate. Images of the superfluid reveal the circular shape of the soliton core and its associated linked rings. Our observations of the knot soliton establish an experimental foundation for future studies of their stability, dynamics and applications within quantum systems. Supported in part by NSF Grant PHY-1205822.

  9. GENOTOXICITY OF TEN CIGARETTE SMOKE CONDENSATES IN FOUR TEST SYSTEMS: COMPARISONS BETWEEN ASSAYS AND CONDENSATES

    Science.gov (United States)

    What is the study? This the first assessment of a set of cigarette smoke condensates from a range of cigarette types in a variety (4) of short-term genotoxicity assays. Why was it done? No such comparative study of cigarette smoke condensates has been reported. H...

  10. Effect of Non-Condensable Gas Mass Fraction on Condensation Heat Transfer for Water-Ethanol Vapor Mixture

    Science.gov (United States)

    Wang, Shixue; Utaka, Yoshio

    The condensation heat transfer characteristic curves for a ternary vapor mixture of water, ethanol and air (or nitrogen) under several ethanol concentrations and relatively low concentrations of air (or nitrogen) were measured. The effect of non-condensable gas on several different domains in the condensation curves was discussed. The effect of non-condensable gas in the domains controlled by the diffusion resistance and the filmwise condensation was not notable; whereas that in the domain dominated by the condensate resistance of dropwise mode was remarkable. Moreover, variations due to changes in non-condensable gas concentration of several characteristic points representing the curves were discussed.

  11. Carbamate-linked cationic lipids with different hydrocarbon chains for gene delivery.

    Science.gov (United States)

    Shi, Jia; Yu, Shijun; Zhu, Jie; Zhi, Defu; Zhao, Yinan; Cui, Shaohui; Zhang, Shubiao

    2016-05-01

    A series of carbamate-linked cationic lipids containing saturated or unsaturated hydrocarbon chains and quaternary ammonium head were designed and synthesized. After recrystallization, carbamate-linked cationic lipids with high purity (over 95%) were obtained. The structures of these lipids were proved by IR spectrum, HR-ESI-MS, HPLC, (1)H NMR and (13)C NMR. The liposomes were prepared by using these cationic lipids and neutral lipid DOPE. Particle size and zeta-potential were studied to show that they were suitable for gene transfection. The DNA-bonding ability of C12:0, C14:0 and C18:1 cationic liposomes was much better than others. The results of transfection showed that hydrophobic chains of these lipids have great effects on their transfection activity. The lipids bearing C12:0, C14:0 saturated chains or C18:1 unsaturated chain showed relatively higher transfection efficiency and lower cytotoxicity. So these cationic lipids could be used as non-viral gene carriers for further studies. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Condensation of refrigerants on vertical fluted tubes

    Energy Technology Data Exchange (ETDEWEB)

    Combs, S.K.; Mailen, G.S.; Murphy, R.W.

    1978-08-01

    Experiments were run to determine heat transfer performance of single vertical fluted tubes with selected fluids condensing on the outside. Working fluids included six fluorocarbons (Refrigerants 11, 21, 22, 113, 114, and 115) and a hydrocarbon (Refrigerant 600a or isobutane). The nine test tubes were of 2.54-cm (1-in.) nominal outside diameter and 1.2 m (4 ft) in length with from 0 (smooth) to 60 axial flutes. Condensing heat transfer coefficients ranged from 620 to 7900 W/m/sup 2/ . K (110 to 1400 Btu/hr . ft/sup 2/ . /sup 0/F) over the heat flux range of 2000 to 43,000 W/m/sup 2/ (920 to 13,600 Btu/hr . ft/sup 2/). All parameters are based on total condensing surface area. The data show that, for a given heat flux, a fluted tube can increase condensing coefficients up to 6.0 times smooth tube values. Further heat transfer enhancement was achieved by the use of drainage skirts on fluted tubes; these skirts effectively divided the 1.2-m (4-ft) tubes into two, four, and eight equal condensing lengths.

  13. Simulation Prediction of Transient Dropwise Condensation

    Science.gov (United States)

    Macner, Ashley; Daniel, Susan; Steen, Paul

    2014-11-01

    In order to design effective surfaces for large-scale dropwise condensation, an understanding of how surface functionalization affects drop growth and coalescence is needed. The long term technological goal is a set of design conditions to help NASA achieve maximum heat transfer rates of waste heat generated from electronics and habitable environments under microgravity conditions. Prediction of condenser surface heat transfer performance requires accurate simulation and modeling of the evolution of populations of drops in time. At shorter times, drops are primarily isolated and grow mainly by condensation onto the liquid-gas interface. At longer times, drops grow mainly by coalescence with neighbors. Simulation of dropwise condensation on a neutrally wetting surface and comparison with our previous experimental results is reported. A steady-state single drop conduction model is empirically fitted to determine a temperature profile that captures the drop size evolution. The simulation accurately predicts the continuous time evolution of number-density of drops, drop-size distributions, total condensate volume, fractional coverage, and median drop-size for both transient and steady states, all with no free parameters. This work was supported by a NASA Office of the Chief Technologist's Space Technology Research Fellowship.

  14. Energy condensed packaged systems. Composition, production, properties

    Directory of Open Access Journals (Sweden)

    Igor L. Kovalenko

    2015-03-01

    Full Text Available In this paper it is presented the substantiation of choice of fuel phase composition and optimal technology of emulsion production on the basis of binary solution of ammonium and calcium nitrates, which provide the obtaining of energy condensed packaged systems with specified properties. The thermal decomposition of energy condensed systems on the basis of ammonium nitrate is investigated. It is shown that the fuel phase of emulsion systems should be based on esters of polyunsaturated acids or on combinations thereof with petroleum products. And ceresin or petroleum wax can be used as the structuring additive. The influence of the technology of energy condensed systems production on the physicochemical and detonation parameters of emulsion explosives is considered. It is shown the possibility of obtaining of emulsion systems with dispersion of 1.3...1.8 microns and viscosity higher than 103 Pa∙s in the apparatus of original design. The sensitizing effect of chlorinated paraffin CP-470 on the thermolysis of energy condensed emulsion system is shown. The composition and production technology of energy condensed packaged emulsion systems of mark Ukrainit-P for underground mining in mines not dangerous on gas and dust are developed.

  15. The NSF Condensed Matter Physics Program

    Science.gov (United States)

    Sokol, Paul

    The Condensed Matter Physics (CMP) program in the NSF Division of Materials Research (DMR) supports experimental, as well as combined experiment and theory projects investigating the fundamental physics behind phenomena exhibited by condensed matter systems. CMP is the largest Individual Investigator Award program in DMR and supports a broad portfolio of research spanning both hard and soft condensed matter. Representative research areas include: 1) phenomena at the nano- to macro-scale including: transport, magnetic, and optical phenomena; classical and quantum phase transitions; localization; electronic, magnetic, and lattice structure or excitations; superconductivity; topological insulators; and nonlinear dynamics. 2) low-temperature physics: quantum fluids and solids; 1D & 2D electron systems. 3) soft condensed matter: partially ordered fluids, granular and colloid physics, liquid crystals, and 4) understanding the fundamental physics of new states of matter as well as the physical behavior of condensed matter under extreme conditions e.g., low temperatures, high pressures, and high magnetic fields. In this talk I will review the current CMP portfolio and discuss future funding trends for the program. I will also describe recent activities in the program aimed at addressing the challenges facing current and future principal investigators.

  16. CFD modelling and validation of wall condensation in the presence of non-condensable gases

    Energy Technology Data Exchange (ETDEWEB)

    Zschaeck, G., E-mail: guillermo.zschaeck@ansys.com [ANSYS Germany GmbH, Staudenfeldweg 12, Otterfing 83624 (Germany); Frank, T. [ANSYS Germany GmbH, Staudenfeldweg 12, Otterfing 83624 (Germany); Burns, A.D. [ANSYS UK Ltd, 97 Milton Park, Abingdon, Oxfordshire OX14 4RY (United Kingdom)

    2014-11-15

    Highlights: • A wall condensation model was implemented and validated in ANSYS CFX. • Condensation rate is assumed to be controlled by the concentration boundary layer. • Validation was done using two laboratory scale experiments. • CFD calculations show good agreement with experimental data. - Abstract: The aim of this paper is to present and validate a mathematical model implemented in ANSYS CFD for the simulation of wall condensation in the presence of non-condensable substances. The model employs a mass sink at isothermal walls or conjugate heat transfer (CHT) domain interfaces where condensation takes place. The model was validated using the data reported by Ambrosini et al. (2008) and Kuhn et al. (1997)

  17. Measurement of liquid-liquid equilibria for condensate + glycol and condensate + glycol + water systems

    DEFF Research Database (Denmark)

    Riaz, Muhammad; Kontogeorgis, Georgios; Stenby, Erling Halfdan

    2011-01-01

    Today's oil and gas production requires the application of various chemicals in large amounts. To evaluate the effects of those chemicals on the environment, it is of crucial importance to know how much of the chemicals are discharged via produced water and how much is dissolved in the crude oil....... The ultimate objective of this work is to develop a predictive thermodynamic model for the mutual solubility of oil, water, and polar chemicals. But for the development and validation of the model, experimental data are required. This work presents new experimental liquid-liquid equilibrium (LLE) data for 1......,2-ethanediol (MEG) + condensate and MEG + water + condensate systems at temperatures from (275 to 323) K at atmospheric pressure. The condensate used in this work is a stabilized natural gas condensate from an offshore field in the North Sea. Compositional analysis of the natural gas condensate was carried out...

  18. [Cell-penetrating chimeric apoptotic peptide AVPI-LMWP/DNA co-delivery system for cancer therapy].

    Science.gov (United States)

    Tan, Jiao; Wang, Ya-Ping; Wang, Hui-Xin; Liang, Jian-Ming; Zhang, Meng; Sun, Xun; Huang, Yong-Zhuo

    2014-12-01

    To develop a cell-penetrating chimeric apoptotic peptide AVPI-LMWP/DNA co-delivery system for cancer therapy, we prepared the AVPI-LMWP/pTRAIL self-assembled complexes containing a therapeutic combination of peptide drug AVPI and DNA drug TRAIL. The chimeric apoptotic peptide AVPI-LMWP was synthesized using the standard solid-phase synthesis. The cationic AVPI-LMWP could condense pTRAIL by electrostatic interaction. The physical-chemical properties of the AVPI-LMWP/pTRAIL complexes were characterized. The cellular uptake efficiency and the inhibitory activity of the AVPI-LMWP/pTRAIL complexes on tumor cell were also performed. The results showed that the AVPI-LMWP/pTRAIL complexes were successfully prepared by co-incubation. With the increase of mass ratio (AVPI-LMWP/DNA), the particle size was decreased and the zeta potential had few change. Agarose gel electrophoresis showed that AVPI-LMWP could fully bind and condense pTRAIL at a mass ratio above 15:1. Cellular uptake efficiency was improved along with the increased ratio of W(AVPI-LMWP)/WpTRAIL. The in vitro cytotoxicity experiments demonstrated that the AVPI-LMWP/pTRAIL (W:W = 20:1) complexes was significantly more effective than the pTRAIL, AVPI-LMWP alone or LMWP/pTRAIL complexes on inhibition of HeLa cell growth. Our studies indicated that the AVPI-LMWP/pTRAIL co-delivery system could deliver plasmid into HeLa cell and induce tumor cell apoptosis efficiently, which showed its potential in cancer therapy using combination of apoptoic peptide and gene drugs.

  19. Nonviral gene-delivery by highly fluorinated gemini bispyridinium surfactant-based DNA nanoparticles.

    Science.gov (United States)

    Fisicaro, Emilia; Compari, Carlotta; Bacciottini, Franco; Contardi, Laura; Pongiluppi, Erika; Barbero, Nadia; Viscardi, Guido; Quagliotto, Pierluigi; Donofrio, Gaetano; Krafft, Marie Pierre

    2017-02-01

    Biological and thermodynamic properties of a new homologous series of highly fluorinated bispyridinium cationic gemini surfactants, differing in the length of the spacer bridging the pyridinium polar heads in 1,1' position, are reported for the first time. Interestingly, gene delivery ability is closely associated with the spacer length due to a structural change of the molecule in solution. This conformation change is allowed when the spacer reaches the right length, and it is suggested by the trends of the apparent and partial molar enthalpies vs molality. To assess the compounds' biological activity, they were tested with an agarose gel electrophoresis mobility shift assay (EMSA), MTT proliferation assay and Transient Transfection assays on a human rhabdomyosarcoma cell line. Data from atomic force microscopy (AFM) allow for morphological characterization of DNA nanoparticles. Dilution enthalpies, measured at 298K, enabled the determination of apparent and partial molar enthalpies vs molality. All tested compounds (except that with the longest spacer), at different levels, can deliver the plasmid when co-formulated with 1,2-dioleyl-sn-glycero-3-phosphoethanolamine (DOPE). The compound with a spacer formed by eight carbon atoms gives rise to a gene delivery ability that is comparable to that of the commercial reagent. The compound with the longest spacer compacts DNA in loosely condensed structures by forming bows, which are not suitable for transfection. Regarding the compounds' hydrogenated counterparts, the tight relationship between the solution thermodynamics data and their biological performance is amazing, making "old" methods the foundation to deeply understanding "new" applications.

  20. Preoperational test report, recirculation condenser cooling systems

    Energy Technology Data Exchange (ETDEWEB)

    Clifton, F.T.

    1997-11-04

    This represents a preoperational test report for Recirculation Condenser Systems, Project W-030. Project W-030 provides a ventilation upgrade for the four Aging Waste Facility tanks. The four system provide condenser cooling water for vapor space cooling of tanks AY1O1, AY102, AZ1O1, AZ102. Each system consists of a valved piping loop, a pair of redundant recirculation pumps, a closed-loop evaporative cooling tower, and supporting instrumentation; equipment is located outside the farm on concrete slabs. Piping is routed to the each ventilation condenser inside the farm via below-grade concrete trenches. The tests verify correct system operation and correct indications displayed by the central Monitor and Control System.

  1. Vector meson condensation in a pion superfluid

    Science.gov (United States)

    Brauner, Tomáš; Huang, Xu-Guang

    2016-11-01

    We revisit the suggestion that charged ρ -mesons undergo Bose-Einstein condensation in isospin-rich nuclear matter. Using a simple version of the Nambu-Jona-Lasinio (NJL) model, we conclude that ρ -meson condensation is either avoided or postponed to isospin chemical potentials much higher than the ρ -meson mass as a consequence of the repulsive interaction with the preformed pion condensate. In order to support our numerical results, we work out a linear sigma model for pions and ρ -mesons, showing that the two models lead to similar patterns of medium dependence of meson masses. As a byproduct, we analyze in detail the mapping between the NJL model and the linear sigma model, focusing on conditions that must be satisfied for a quantitative agreement between the models.

  2. DROPWISE CONDENSATION ON MICRO- AND NANOSTRUCTURED SURFACES

    Energy Technology Data Exchange (ETDEWEB)

    Enright, R; Miljkovic, N; Alvarado, JL; Kim, K; Rose, JW

    2014-07-23

    In this review we cover recent developments in the area of surface-enhanced dropwise condensation against the background of earlier work. The development of fabrication techniques to create surface structures at the micro-and nanoscale using both bottom-up and top-down approaches has led to increased study of complex interfacial phenomena. In the heat transfer community, researchers have been extensively exploring the use of advanced surface structuring techniques to enhance phase-change heat transfer processes. In particular, the field of vapor-to-liquid condensation and especially that of water condensation has experienced a renaissance due to the promise of further optimizing this process at the micro-and nanoscale by exploiting advances in surface engineering developed over the last several decades.

  3. Condensation heat transfer coefficient versus wettability

    Science.gov (United States)

    Roudgar, M.; De Coninck, J.

    2015-05-01

    In this paper we show how condensation on substrates can induce wetting behavior that is quite different from that of deposited or impinging drops. We describe surfaces with the same wettability in ambient conditions presenting different wetting behavior and growth of droplets in condensation. The experimental results show a rapid spread of droplets and formation of the film on the copper surface, while droplets on SU-8 surface remains on the regular shape while they grow within the time, without coalescence, as observed for Cu. Although the heat conductivity of SU-8 is much lower, due to a difference in wetting behavior, the heat transfer coefficient (h) is higher for dropwise condensation on Cu with a thin layer of SU-8 than filmwise on the bare copper.

  4. Nonlocal Condensate Model for QCD Sum Rules

    CERN Document Server

    Hsieh, Ron-Chou

    2009-01-01

    We include effects of nonlocal quark condensates into QCD sum rules (QSR) via the K$\\ddot{\\mathrm{a}}$ll$\\acute{\\mathrm{e}}$n-Lehmann representation for a dressed fermion propagator, in which a negative spectral density function manifests their nonperturbative nature. Applying our formalism to the pion form factor as an example, QSR results are in good agreement with data for momentum transfer squared up to $Q^2 \\approx 10 $ GeV$^2$. It is observed that the nonlocal quark-condensate contribution descends like $1/Q^4$, different from the exponential decrease in $Q^2$ obtained in the literature, and contrary to the linear rise in the local-condensate approximation.

  5. Dropwise condensation on inclined textured surfaces

    CERN Document Server

    Khandekar, Sameer

    2014-01-01

    Dropwise Condensation on Textured Surfaces presents a holistic framework for understanding dropwise condensation through mathematical modeling and meaningful experiments. The book presents a review of the subject required to build up models as well as to design experiments. Emphasis is placed on the effect of physical and chemical texturing and their effect on the bulk transport phenomena. Application of the model to metal vapor condensation is of special interest. The unique behavior of liquid metals, with their low Prandtl number and high surface tension, is also discussed. The model predicts instantaneous drop size distribution for a given level of substrate subcooling and derives local as well as spatio-temporally averaged heat transfer rates and wall shear stress.

  6. Field theories of condensed matter physics

    CERN Document Server

    Fradkin, Eduardo

    2013-01-01

    Presenting the physics of the most challenging problems in condensed matter using the conceptual framework of quantum field theory, this book is of great interest to physicists in condensed matter and high energy and string theorists, as well as mathematicians. Revised and updated, this second edition features new chapters on the renormalization group, the Luttinger liquid, gauge theory, topological fluids, topological insulators and quantum entanglement. The book begins with the basic concepts and tools, developing them gradually to bring readers to the issues currently faced at the frontiers of research, such as topological phases of matter, quantum and classical critical phenomena, quantum Hall effects and superconductors. Other topics covered include one-dimensional strongly correlated systems, quantum ordered and disordered phases, topological structures in condensed matter and in field theory and fractional statistics.

  7. Preoperational test report, recirculation condenser cooling systems

    Energy Technology Data Exchange (ETDEWEB)

    Clifton, F.T.

    1997-11-04

    This represents a preoperational test report for Recirculation Condenser Systems, Project W-030. Project W-030 provides a ventilation upgrade for the four Aging Waste Facility tanks. The four system provide condenser cooling water for vapor space cooling of tanks AY1O1, AY102, AZ1O1, AZ102. Each system consists of a valved piping loop, a pair of redundant recirculation pumps, a closed-loop evaporative cooling tower, and supporting instrumentation; equipment is located outside the farm on concrete slabs. Piping is routed to the each ventilation condenser inside the farm via below-grade concrete trenches. The tests verify correct system operation and correct indications displayed by the central Monitor and Control System.

  8. The condensation of water on adsorbed viruses.

    Science.gov (United States)

    Alonso, José María; Tatti, Francesco; Chuvilin, Andrey; Mam, Keriya; Ondarçuhu, Thierry; Bittner, Alexander M

    2013-11-26

    The wetting and dewetting behavior of biological nanostructures and to a greater degree single molecules is not well-known even though their contact with water is the basis for all biology. Here, we show that environmental electron microscopy (EM) can be applied as a means of imaging the condensation of water onto viruses. We captured the formation of submicrometer water droplets and filaments on single viral particles by environmental EM and by environmental transmission EM. The condensate structures are compatible with capillary condensation between adsorbed virus particles and with known droplet shapes on patterned surfaces. Our results confirm that such droplets exist down to evaporation cycle as expected from their stability in air and water. Moreover we developed procedures that overcome problems of beam damage and of resolving structures with a low atomic number.

  9. Vector meson condensation in a pion superfluid

    CERN Document Server

    Brauner, Tomas

    2016-01-01

    We revisit the suggestion that charged rho-mesons undergo Bose-Einstein condensation in isospin-rich nuclear matter. Using a simple version of the Nambu-Jona-Lasinio (NJL) model, we conclude that rho-meson condensation is either avoided or postponed to isospin chemical potentials much higher than the rho-meson mass as a consequence of the repulsive interaction with the preformed pion condensate. In order to support our numerical results, we work out a linear sigma model for pions and rho-mesons, showing that the two models lead to similar patterns of medium dependence of meson masses. As a byproduct, we analyze in detail the mapping between the NJL model and the linear sigma model, focusing on conditions that must be satisfied for a quantitative agreement between the models.

  10. Cationic lipids bearing succinic-based, acyclic and macrocyclic hydrophobic domains: Synthetic studies and in vitro gene transfer.

    Science.gov (United States)

    Jubeli, Emile; Maginty, Amanda B; Khalique, Nada Abdul; Raju, Liji; Nicholson, David G; Larsen, Helge; Pungente, Michael D; Goldring, William P D

    2017-01-05

    In this communication we describe the construction of four succinic-based cationic lipids, their formulation with plasmid DNA (pDNA), and an evaluation of their in vitro gene delivery into Chinese hamster ovarian (CHO-K1) cells. The cationic lipids employed in this work possess either a dimethylamine or trimethylamine headgroup, and a macrocyclic or an acyclic hydrophobic domain composed of, or derived from two 16-atom, succinic-based acyl chains. The synthesized lipids and a co-lipid of neutral charge, either cholesterol or 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), were formulated in an overall 3:2 cationic-to-neutral lipid molar ratio, then complexed with plasmid DNA (pDNA). The relative transfection performance was evaluated via a comparison between matched versus mismatched formulations defined by the rigidity relationship between the lipids employed. Gel electrophoresis was used to characterize the binding of the lipid formulations with plasmid DNA and the relative degree of plasmid degradation using a DNase I degradation assay. Small angle X-ray diffraction (SAXD) was employed to characterize the packing morphology of the lipid-DNA complexes. In general, the succinic unit embedded within the hydrophobic domain of the cationic lipids was found to improve lipid hydration. The transfection assays revealed a general trend in which mismatched formulations that employed a rigid lipid combined with a non-rigid (or flexible) lipid, outperformed the matched formulations. The results from this work suggest that the design of the cationic lipid structure and the composition of the lipoplex formulation play key roles in governing the transfection performance of nonviral gene delivery agents.

  11. Use of sorption technology for treatment of humidity condensate for potable water

    Science.gov (United States)

    Ajjarapu, Sundara R. M.; Symons, J. M.

    1992-01-01

    This research focused on the testing of the original potable water processor aboard Space Station Freedom that was to produce potable water from the humidity condensate and additional water generated by carbon dioxide reduction. Humidity condensate was simulated by an influent water model 'Ersatz'. The humidity condensate was treated with multifiltration (MF) beds that consisted of a train of sorption beds (referred to as 'Unibed') designed to remove specific contaminants. For the complete simulated MF system runs tested for 100 bed volumes (BV) (volume processed/total column volume), 0.6 percent of the TOC was removed by the SAC/IRN 77 (Strong Acid Cation exchange resin), 39.6 percent of the total organic carbon (TOC) was removed by the WBA/IRA 68 (Weak Base Anion exchange resin), 13.2 percent of the TOC was removed by activated carbon adsorption (580-26), and the remaining sorbent media acted as polishing units to remove an additional 1.6 percent of the TOC at steady state. At steady state, 45 percent of the influent TOC passed through the MF bed.

  12. Performance of monosphere new gel type ion exchange resins for condensate polisher at PWR plants

    Energy Technology Data Exchange (ETDEWEB)

    Nakanishi, S.; Nakamura, M.; Asou, K. [Kansai Electric Power Co., Inc., Osaka (Japan); Izumi, T.; Deguchi, T.; Ino, T.; Hagiwara, M.

    1998-12-31

    There are two kinds of ion exchange resins of gel type and porous one which are used as condensate polisher in LWR nuclear power plants. In order to estimate the performance of these resins on the condensate polisher at the secondary cycle of Japanese PWR plants, a column test was performed setting the column test device in Ohi power station unit 1 of the Kansai Electric Power Co., Inc. and the variations of the resin properties and the samples at the end of column were analyzed. The column test showed that the cross-linking degree of the new gel resins used was lower than those of porous ones. The new resins captured larger amounts of Matrix-Diffused Crud than the conventional cation resins before regeneration but not after that. Whereas the surface adsorbed crud was less captured by the new resins than conventional anion resins. However, there were little differences among these resins in respects of rinsing characteristics, sphericity, water quality, break through capacity, etc. At the condensate polisher in the secondary system it was confirmed that new gel resins had almost the same performance as one of the conventional ones and could be applied to the actual plant. (M.N.)

  13. Temporal dynamics of Bose-condensed gases

    Energy Technology Data Exchange (ETDEWEB)

    Trujillo Martinez, Mauricio

    2014-03-19

    We perform a detailed quantum dynamical study of non-equilibrium trapped, interacting Bose-condensed gases. We investigate Josephson oscillations between interacting Bose-Einstein condensates confined in a finite size double-well trap and the non-trivial time evolution of a coherent state placed at the center of a two dimensional optical lattice. For the Josephson oscillations three time scales appear. We find that Josephson junction can sustain multiple undamped oscillations up to a characteristic time scale τ{sub c} without exciting atoms out of the condensates. Beyond the characteristic time scale τ{sub c} the dynamics of the junction are governed by fast, non-condensed particles assisted Josephson tunnelling as well as the collisions between non-condensed particles. In the non-condensed particles dominated regime we observe strong damping of the oscillations due to inelastic collisions, equilibrating the system leading to an effective loss of details of the initial conditions. In addition, we predict that an initially self-trapped BEC state will be destroyed by these fast dynamics. The time evolution of a coherent state released at the center of a two dimensional optical lattice shows a ballistic expansion with a decreasing expansion velocity for increasing two-body interactions strength and particle number. Additionally, we predict that if the two-body interactions strength exceeds a certain value, a forerunner splits up from the expanding coherent state. We also observe that this system, which is prepared far from equilibrium, can evolve to a quasistationary non-equilibrium state.

  14. Renormalisation Group Flow and Kaon Condensation

    CERN Document Server

    Krippa, Boris

    2016-01-01

    Functional renormalisation group approach is applied to a system of kaons with finite chemical potential. A set of approximate flow equations for the effective couplings is derived and solved. At high scale the system is found to be at the normal phase whereas at some critical value of the running scale it undergoes the phase transition (PT) to the phase with a spontaneously broken symmetry with the kaon condensate as an order parameter. The value of the condensate turns out to be quite sensitive to the kaon-kaon scattering length.

  15. Bose-Einstein Condensation of Atomic Hydrogen

    CERN Document Server

    Kleppner, D; Killian, T C; Fried, D G; Willmann, L; Landhuis, D; Moss, S C; Kleppner, Daniel; Greytak, Thomas J.; Killian, Thomas C.; Fried, Dale G.; Willmann, Lorenz; Landhuis, David; Moss, Stephen C.

    1998-01-01

    We have observed Bose-Einstein condensation (BEC) of trapped atomic hydrogen, and studied it by two-photon spectroscopy of the 1S-2S transition. In these lecture notes we briefly review the history of spin-polarized atomic hydrogen and describe the final steps to BEC. Laser spectroscopy, which probes the difference in mean field energy of the 1S and 2S states, is used to study the condensate, which has a peak density of 4.8e15 cm^-3 and population of 10^9.

  16. Turbulent meson condensation in quark deconfinement

    Directory of Open Access Journals (Sweden)

    Koji Hashimoto

    2015-06-01

    Full Text Available In a QCD-like strongly coupled gauge theory at large Nc, using the AdS/CFT correspondence, we find that heavy quark deconfinement is accompanied by a coherent condensation of higher meson resonances. This is revealed in non-equilibrium deconfinement transitions triggered by static, as well as quenched electric fields even below the Schwinger limit. There, we observe a “turbulent” energy flow to higher meson modes, which finally results in the quark deconfinement. Our observation is consistent with seeing deconfinement as a condensation of long QCD strings.

  17. Geometric approach to condensates in holographic QCD

    CERN Document Server

    Hirn, J; Sanz, V; Hirn, Johannes; Rius, Nuria; Sanz, Veronica

    2006-01-01

    An SU(Nf)xSU(Nf) Yang-Mills theory on an extra-dimensional interval is considered, with appropriate symmetry-breaking boundary conditions on the IR brane. UV-brane to UV-brane correlators at high energies are compared with the OPE of two-point functions of QCD quark currents. Condensates correspond to departure from AdS of the (different) metrics felt by vector and axial combinations, away from the UV brane. Their effect on hadronic observables is studied: the extracted condensates agree with the signs and orders of magnitude expected from QCD.

  18. Colored condensates deep inside neutron stars

    CERN Document Server

    Blaschke, David

    2014-01-01

    It is demonstrated how in the absence of solutions for QCD under conditions deep inside compact stars an equation of state can be obtained within a model that is built on the basic symmetries of the QCD Lagrangian, in particular chiral symmetry and color symmetry. While in the vacuum the chiral symmetry is spontaneously broken, it gets restored at high densities. Color symmetry, however, gets broken simultaneously by the formation of colorful diquark condensates. It is shown that a strong diquark condensate in cold dense quark matter is essential for supporting the possibility that such states could exist in the recently observed pulsars with masses of 2 $M_\\odot$.

  19. Composition of gases vented from a condenser

    Energy Technology Data Exchange (ETDEWEB)

    Lyon, R.N.

    1980-08-01

    Designers of systems that involve condensers often need to predict the amount of process vapor that accompanies the noncondensable gases that are vented from the condensers. An approximation is given that appears to provide, in many cases, reasonably accurate values for the mole ratio of process vapor to noncondensable gases in the vented mixture. The approximation is particularly applicable to flash and direct-contact power systems for geothermal brines and ocean thermal energy conversion (OTEC). More regorous relationships are available for exceptional cases.

  20. Chiral Lagrangians and quark condensate in nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Delorme, J.; Chanfray, G.; Ericson, M.

    1996-03-01

    The evolution of density of quark condensate in nuclear medium with interacting nucleons, including the short range correlations is examined. Two chiral models are used, the linear sigma model and the non-linear one. It is shown that the quark condensate, as other observables, is independent on the variant selected. The application to physical pions excludes the linear sigma model as a credible one. The non-linear models restricted to pure s-wave pion-nucleon scattering are examined. (author). 28 refs.; Submitted to nuclear Physics, A (NL).

  1. In situ emulsion cationic polymerization of isoprene onto the surface of graphite oxide sheets

    Science.gov (United States)

    Pazat, Alice; Beyou, Emmanuel; Barrès, Claire; Bruno, Florence; Janin, Claude

    2017-02-01

    Grafting of polymers onto graphite oxide sheets (GO) has been widely studied in recent years due to the numerous applications of GO-based composites. Herein, polyisoprene (PI) chains were anchored on the surface of GO by in situ cationic polymerization using a "grafting through" approach with allyltrimethoxysilane-modified GO (GO-ATMS). First, the functionalization of GO sheets through the hydrolysis-condensation of allyltrimethoxysilane (ATMS) molecules was qualitatively evidenced by infra-red spectroscopy and X-ray photoelectron spectrometry and a weight content of 4% grafted ATMS was calculated from thermogravimetric analysis. Then, isoprene was in situ polymerized through a one-pot cationic mechanism by using a highly water-dispersible Lewis acid surfactant combined catalyst. For comparison, it was shown that the cationic polymerization of isoprene in presence of un-functionalized GO sheets led to a polyisoprene weight content on the solid filler divided by 3 compared to GO-ATMS. Finally, the compounding of the modified GO/PI composites was performed at a processing temperature of 80 °C with 2 phr and 15 phr loadings and it was shown a decrease of the air permeability coefficient of 27% for the vulcanizates with 15 phr loading.

  2. Influence of condensation temperature on selected exhaled breath parameters

    Directory of Open Access Journals (Sweden)

    Manini Paola

    2005-09-01

    Full Text Available Abstract Background The effects of changes in cooling temperature on biomarker levels in exhaled breath condensate have been little investigated. The aim of the study was to test the effect of condensation temperature on the parameters of exhaled breath condensate and the levels of selected biomarkers. Methods Exhaled breath condensate was collected from 24 healthy subjects at temperatures of -10, -5, 0 and +5 C degrees. Selected parameters (condensed volume and conductivity and biomarkers (hydrogen peroxide, malondialdehyde were measured. Results There was a progressive increase in hydrogen peroxide and malondialdehyde concentrations, and condensate conductivity as the cooling temperature increased; total condensate volume increased as the cooling temperature decreased. Conclusion The cooling temperature of exhaled breath condensate collection influenced selected biomarkers and potential normalizing factors (particularly conductivity in different ways ex vivo. The temperature of exhaled breath condensate collection should be controlled and reported.

  3. Cationically polymerizable monomers derived from renewable sources

    Energy Technology Data Exchange (ETDEWEB)

    Crivello, J.V.

    1992-10-01

    The objectives of this project are to design and synthesize novel monomers which orginate from renewable biological sources and to carry out their rapid, efficient, pollution-free and energy efficient cationic polymerization to useful products under the influence of ultraviolet light or heat. A summary of the results of the past year's research on cationically polymerizable monomers derived from renewable sources is presented. Three major areas of investigation corresponding to the different classes of naturally occurring starting materials were investigated; epoxidized terpenes and natural rubber and vinyl ethers from alcohols and carbohydrates.

  4. Metalated Nitriles: Cation-Controlled Cyclizations

    Science.gov (United States)

    Fleming, Fraser F.; Wei, Yunjing; Liu, Wang; Zhang, Zhiyu

    2008-01-01

    Judicious choice of cation allows the selective cyclization of substituted γ-hydroxynitriles to trans- or cis-decalins and trans- or cis-bicyclo[5.4.0]-undecanes. The stereoselectivities are consistent with deprotonations generating two distinctly different metalated nitriles: an internally coordinated nitrile anion with BuLi, and a C-magnesiated nitrile with i-PrMgCl. Employing cations to control the geometry of metalated nitriles permits stereodivergent cyclizations with complete control over the stereochemistry of the quaternary, nitrile-bearing carbon. PMID:17579448

  5. Cation Effect on Copper Chemical Mechanical Polishing

    Institute of Scientific and Technical Information of China (English)

    WANG Liang-Yong; LIU Bo; SONG Zhi-Tang; FENG Song-Lin

    2009-01-01

    We examine the effect of cations in solutions containing benzotriazole (BTA) and H2O2 on copper chemical mechanical polishing (CMP). On the base of atomic force microscopy (AFM) and material removal rate (MRR) results, it is found that ammonia shows the highest MRR as well as good surface after CMP, while KOH demon-strates the worst performance. These results reveal a mechanism that sma//molecules with lone-pairs rather than molecules with steric effect and common inorganic cations are better for copper CMP process, which is indirectly confirmed by open circuit potential (OCP).

  6. Cation Effect on Copper Chemical Mechanical Polishing

    Science.gov (United States)

    Wang, Liang-Yong; Liu, Bo; Song, Zhi-Tang; Feng, Song-Lin

    2009-02-01

    We examine the effect of cations in solutions containing benzotriazole (BTA) and H2O2 on copper chemical mechanical polishing (CMP). On the base of atomic force microscopy (AFM) and material removal rate (MRR) results, it is found that ammonia shows the highest MRR as well as good surface after CMP, while KOH demonstrates the worst performance. These results reveal a mechanism that small molecules with lone-pairs rather than molecules with steric effect and common inorganic cations are better for copper CMP process, which is indirectly confirmed by open circuit potential (OCP).

  7. Cationically polymerizable monomers derived from renewable sources

    Energy Technology Data Exchange (ETDEWEB)

    Crivello, J.V.

    1992-10-01

    The objectives of this project are to design and synthesize novel monomers which orginate from renewable biological sources and to carry out their rapid, efficient, pollution-free and energy efficient cationic polymerization to useful products under the influence of ultraviolet light or heat. A summary of the results of the past year's research on cationically polymerizable monomers derived from renewable sources is presented. Three major areas of investigation corresponding to the different classes of naturally occurring starting materials were investigated; epoxidized terpenes and natural rubber and vinyl ethers from alcohols and carbohydrates.

  8. Binding of single stranded nucleic acids to cationic ligand functionalized gold nanoparticles.

    Science.gov (United States)

    Nash, Jessica A; Tucker, Tasha L; Therriault, William; Yingling, Yaroslava G

    2016-11-11

    The interactions of nanoparticles (NPs) with single stranded nucleic acids (NAs) have important implications in gene delivery, and nanotechnological and biomedical applications. Here, the complexation of cationic ligand functionalized gold nanoparticles with single stranded deoxyribose nucleic acid (DNA) and ribonucleic acid (RNA) are examined using all atom molecular dynamics simulations. The results indicated that complexation depends mostly on charge of nanoparticle, and, to lesser extent, sequence and type of nucleic acid. For cationic nanoparticles, electrostatic interactions between charged ligands and the nucleic acid backbone dominate binding regardless of nanoparticle charge. Highly charged nanoparticles bind more tightly and cause compaction of the single-stranded NAs through disruption of intrastrand π-π stacking and hydrogen bonding. However, poly-purine strands (polyA-DNA, polyA-RNA) show less change in structure than poly-pyrimidine strands (polyT-DNA, polyU-RNA). Overall, the results show that control over ssNA structure may be achieved with cationic NPs with a charge of more than 30, but the extent of the structural changes depends on sequence.

  9. Enhancing Condensers for Geothermal Systems: the Effect of High Contact Angles on Dropwise Condensation Heat Transfer

    Energy Technology Data Exchange (ETDEWEB)

    Kennedy, John M.; Kim, Sunwoo; Kim, Kwang J.

    2009-10-06

    Phase change heat transfer is notorious for increasing the irreversibility of, and therefore decreasing the efficiency of, geothermal power plants. Its significant contribution to the overall irreversibility of the plant makes it the most important source of inefficiency in the process. Recent studies here have shown the promotion of drop wise condensation in the lab by means of increasing the surface energy density of a tube with nanotechnology. The use of nanotechnology has allowed the creation of surface treatments which discourage water from wetting a tube surface during a static test. These surface treatments are unique in that they create high- contact angles on the condensing tube surfaces to promote drop wise condensation.

  10. Condensation heat transfer on two-tier superhydrophobic surfaces

    Science.gov (United States)

    Cheng, Jiangtao; Vandadi, Aref; Chen, Chung-Lung

    2012-09-01

    We investigated water vapor condensation on a two-tier superhydrophobic surface in an environmental scanning electron microscope (ESEM) and in a customer-designed vapor chamber. We have observed continuous dropwise condensation (DWC) on the textured surface in ESEM. However, a film layer of condensate was formed on the multiscale texture in the vapor chamber. Due to the filmwise condensation, the condensation heat transfer coefficient of the superhydrophobic surface is lower than that of a flat hydrophobic surface especially under high heat flux situations. Our studies indicate that adaptive and prompt condensate droplet purging is the dominant factor for sustaining long-term DWC.

  11. Spatially inhomogeneous condensate in asymmetric nuclear matter

    NARCIS (Netherlands)

    Sedrakian, A

    2001-01-01

    We study the isospin singlet pairing in asymmetric nuclear matter with nonzero total momentum of the condensate Cooper pairs. The quasiparticle excitation spectrum is fourfold split compared to the usual BCS spectrum of the symmetric, homogeneous matter. A twofold splitting of the spectrum into sepa

  12. Neutrino emissivity under neutral kaon condensation

    CERN Document Server

    Kubis, S

    2006-01-01

    Neutrino emissivity from neutron star matter with neutral kaon condensate is considered. It is shown that a new cooling channel is opened, and what is more, all previously known channels acquire the greater emissivity reaching the level of the direct URCA cycle in normal matter.

  13. Initial stages of Bose-Einstein condensation

    NARCIS (Netherlands)

    Stoof, H.T.C.

    1997-01-01

    We present the quantum theory for the nucleation of Bose-Einstein condensation in a dilute atomic Bose gas. This quantum theory has the important advantage that both the kinetic and coherent stages of the nucleation process can be described in a unified way by a single Fokker-Planck equation.

  14. Initial stages of Bose-Einstein condensation

    NARCIS (Netherlands)

    Stoof, H.T.C.

    2001-01-01

    We present the quantum theory for the nucleation of Bose-Einstein condensation in a dilute atomic Bose gas. This quantum theory confirms the results of the semiclassical treatment, but has the important advantage that both the kinetic and coherent stages of the nucleation process can now be describe

  15. Fundamentals of neutron scattering by condensed matter

    Energy Technology Data Exchange (ETDEWEB)

    Scherm, R. [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France)

    1996-12-31

    The purpose of this introductory lecture is to give the basic facts about the scattering of neutrons by condensed matter. This lecture is restricted to nuclear scattering, whereas magnetic scattering will be dealt with in an other course. Most of the formalism, however, can also be easily extended to magnetic scattering. (author) 17 figs., 3 tabs., 10 refs.

  16. Orientifold Planar Equivalence: The Chiral Condensate

    DEFF Research Database (Denmark)

    Armoni, Adi; Lucini, Biagio; Patella, Agostino

    2008-01-01

    The recently introduced orientifold planar equivalence is a promising tool for solving non-perturbative problems in QCD. One of the predictions of orientifold planar equivalence is that the chiral condensates of a theory with $N_f$ flavours of Dirac fermions in the symmetric (or antisymmetric...

  17. Capillary condensation between disks in two dimensions

    DEFF Research Database (Denmark)

    Gil, Tamir; Ipsen, John Hjorth

    1997-01-01

    Capillary condensation between two two-dimensional wetted circular substrates (disks) is studied by an effective free energy description of the wetting interface. The interfacial free-energy potential is developed on the basis of the theory for the wetting of a single disk, where interfacial capi....... The theory can be applied to the description of flocculations in two-dimensional systems of colloids....

  18. Tachyon Condensation in Rotated Brane Configurations

    CERN Document Server

    de Alwis, S P

    1999-01-01

    The decay of rotated brane configurations and the corresponding condensation of tachyons is discussed. In a certain IIB orbifold case a heuristic argument about the mass of the state living on the fixed plane is made. When the rotation angle is $\\pi$ this mass agrees with that obtained by Sen.

  19. ISOSPIN BREAKING AND THE CHIRAL CONDENSATE.

    Energy Technology Data Exchange (ETDEWEB)

    CREUTZ, M.

    2005-07-25

    With two degenerate quarks, the chiral condensate exhibits a jump as the quark masses pass through zero. I discuss how this single transition splits into two Ising like transitions when the quarks are made non-degenerate. The order parameter is the expectation of the neutral pion field. The transitions represent long distance coherent phenomena occurring without the Dirac operator having vanishingly small eigenvalues.

  20. PECVD silicon nitride diaphragms for condenser microphones

    NARCIS (Netherlands)

    Scheeper, P.R.; Voorthuyzen, J.A.; Bergveld, P.

    1991-01-01

    The application of plasma-enhanced chemical vapour deposited (PECVD) silicon nitride as a diaphragm material for condenser microphones has been investigated. By means of adjusting the SiH4/NH3 gas-flow composition, silicon-rich silicon nitride films have been obtained with a relatively low tensile s

  1. Chaos in a Bose-Einstein condensate

    Institute of Scientific and Technical Information of China (English)

    Wang Zhi-Xia; Ni Zheng-Guo; Cong Fu-Zhong; Liu Xue-Shen; Chen Lei

    2010-01-01

    It is demonstrated that Smale-horseshoe chaos exists in the time evolution of the one-dimensional Bose-Einstein condensate driven by time-periodic harmonic or inverted-harmonic potential.A formally exact solution of the timedependent Gross-Pitaevskii equation is constructed,which describes the matter shock waves with chaotic or periodic amplitudes and phases.

  2. Activity, purification, and analysis of condensed tannins

    Science.gov (United States)

    As a class of plant polyphenolic compounds contained in some forages (i.e., sanfoin, big trefoil, birdfoot trefoil), condensed tannins (CTs), also referred to as proanthocyanidins (PAs), exhibit a variety of biological effects on ruminants and on the dairy farm nitrogen cycle. Interest in CTs stems ...

  3. Polariton condensation in a disordered potential

    DEFF Research Database (Denmark)

    Antón, C.; Tosi, G.; Lingg, C. A.;

    2011-01-01

    We study polariton condensation under OPO (Optical Parametric Oscillator) out-of-equilibrium conditions [1] in the presence of linear and point defects. Because of the simultaneous presence of pump, signal and idler emitting at different wave vectors, as well as of photonic disorder, the system i...

  4. Free convective condensation in a vertical enclosure

    Energy Technology Data Exchange (ETDEWEB)

    Fox, R.J.; Peterson, P.F. [Univ. of California, Berkeley, CA (United States); Corradini, M.L.; Pernsteiner, A.P. [Univ. of Wisconsin, Madison, WI (United States)

    1995-09-01

    Free convective condensation in a vertical enclosure was studied numerically and the results were compared with experiments. In both the numerical and experimental investigations, mist formation was observed to occur near the cooling wall, with significant droplet concentrations in the bulk. Large recirculation cells near the end of the condensing section were generated as the heavy noncondensing gas collecting near the cooling wall was accelerated downward. Near the top of the enclosure the recirculation cells became weaker and smaller than those below, ultimately disappearing near the top of the condenser. In the experiment the mist density was seen to be highest near the wall and at the bottom of the condensing section, whereas the numerical model predicted a much more uniform distribution. The model used to describe the formation of mist was based on a Modified Critical Saturation Model (MCSM), which allows mist to be generated once the vapor pressure exceeds a critical value. Equilibrium, nonequilibrium, and MCSM calculations were preformed, showing the experimental results to lie somewhere in between the equilibrium and nonequilibrium predictions of the numerical model. A single adjustable constant (indicating the degree to which equilibrium is achieved) is used in the model in order to match the experimental results.

  5. Bose-Einstein condensation of plexcitons

    CERN Document Server

    Rodriguez, S R K; Rivas, J Gomez

    2013-01-01

    Bosons (particles with integer spin) above a critical density to temperature ratio may macroscopically populate the ground state of a system, in an effect known as Bose-Einstein Condensation (BEC). The observation of BEC in dilute atomic gases was a great triumph of modern physics, a task requiring nK cooling of atoms. Following these demonstrations, a quest for lighter bosons enabling BEC at higher temperatures came to light. Photons in a microcavity were destined to fulfil this quest. Their coupling to semiconductor excitons allowed the condensation of exciton-polaritons at a few K in solid-state, and the condensation of photons was later observed in a liquid-state dye at room-temperature. Distinctly, one of the most actively studied excitations in condensed matter, surface plasmon polaritons - collective oscillations of conduction electrons in metals -, has never been shown or predicted to exhibit BEC. The strong radiative and Ohmic losses in metals, together with the lack of a suitable (e.g. harmonic) pot...

  6. Pollen grains are efficient cloud condensation nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Pope, F D, E-mail: fdp21@cam.ac.uk [Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW (United Kingdom)

    2010-10-15

    This letter presents a laboratory study investigating the ability of pollen grains to act as cloud condensation nuclei. The hygroscopicity of pollen is measured under subsaturated relative humidities using an electrodynamic balance. It is found, along with other results, that pollen exhibits bulk uptake of water under subsaturated conditions. Through the use of an environmental scanning electron microscope it was observed that the surface of pollen is wettable at high subsaturated humidities. The hygroscopic response of the pollen to subsaturated relative humidities is parametrized using {kappa}-Koehler theory and values of the parameter {kappa} for pollen are between 0.05 and 0.1. It is found that while pollen grains are only moderately hygroscopic, they can activate at critical supersaturations of 0.001% and lower, and thus pollen grains will readily act as cloud condensation nuclei. While the number density of pollen grains is too low for them to represent a significant global source of cloud condensation nuclei, the large sizes of pollen grains suggest that they will be an important source of giant cloud condensation nuclei. Low temperature work using the environmental scanning electron microscope indicated that pollen grains do not act as deposition ice nuclei at temperatures warmer than - 15 deg. C.

  7. On condensation of topological defects and confinement

    CERN Document Server

    Gaete, P; Gaete, Patricio; Wotzasek, Clovis

    2004-01-01

    We study the static quantum potential for a theory of anti-symmetric tensor fields that results from the condensation of topological defects, within the framework of the gauge-invariant but path-dependent variables formalism. Our calculations show that the interaction energy is the sum of a Yukawa and a linear potentials, leading to the confinement of static probe charges.

  8. rotor of the SC rotating condenser

    CERN Multimedia

    1974-01-01

    The rotor of the rotating condenser was installed instead of the tuning fork as the modulating element of the radiofrequency system, when the SC accelerator underwent extensive improvements between 1973 to 1975 (see object AC-025). The SC was the first accelerator built at CERN. It operated from August 1957 until it was closed down at the end of 1990.

  9. Condensation enhancement by means of electrohydrodynamic techniques

    Directory of Open Access Journals (Sweden)

    Butrymowicz Dariusz

    2014-12-01

    Full Text Available Short state-of-the-art on the enhancement of condensation heat transfer techniques by means of condensate drainage is presented in this paper. The electrohydrodynamic (EHD technique is suitable for dielectric media used in refrigeration, organic Rankine cycles and heat pump devices. The electric field is commonly generated in the case of horizontal tubes by means of a rod-type electrode or mesh electrodes. Authors proposed two geometries in the presented own experimental investigations. The first one was an electrode placed just beneath the tube bottom and the second one consisted of a horizontal finned tube with a double electrode placed beneath the tube. The experimental investigations of these two configurations for condensation of refrigerant R-123 have been accomplished. The obtained results confirmed that the application of the EHD technique for the investigated tube and electrode arrangement caused significant increase in heat transfer coefficient. The condensation enhancement depends both on the geometry of the electrode system and on the applied voltage.

  10. Convection in Condensible-rich Atmospheres

    Science.gov (United States)

    Ding, F.; Pierrehumbert, R. T.

    2016-05-01

    Condensible substances are nearly ubiquitous in planetary atmospheres. For the most familiar case—water vapor in Earth’s present climate—the condensible gas is dilute, in the sense that its concentration is everywhere small relative to the noncondensible background gases. A wide variety of important planetary climate problems involve nondilute condensible substances. These include planets near or undergoing a water vapor runaway and planets near the outer edge of the conventional habitable zone, for which CO2 is the condensible. Standard representations of convection in climate models rely on several approximations appropriate only to the dilute limit, while nondilute convection differs in fundamental ways from dilute convection. In this paper, a simple parameterization of convection valid in the nondilute as well as dilute limits is derived and used to discuss the basic character of nondilute convection. The energy conservation properties of the scheme are discussed in detail and are verified in radiative-convective simulations. As a further illustration of the behavior of the scheme, results for a runaway greenhouse atmosphere for both steady instellation and seasonally varying instellation corresponding to a highly eccentric orbit are presented. The latter case illustrates that the high thermal inertia associated with latent heat in nondilute atmospheres can damp out the effects of even extreme seasonal forcing.

  11. Dropwise condensation on a cold gradient substrate

    Science.gov (United States)

    Macner, Ashley; Daniel, Susan; Steen, Paul

    2012-11-01

    Distributions of drops that arise from dropwise condensation evolve by nucleation, growth, and coalescence of drops. An understanding of how surface-energy gradients applied to the substrate affect drop growth and coalescence is needed for design of effective surfaces for large-scale dropwise condensation. Transient dropwise condensation from a vapor phase onto a cold and chemically treated surface is reported. The surfaces were treated to deliver either a uniform contact-angle or a gradient of contact-angles by silanization. The time evolution of drop-size and number-density distributions is reported. For a typical condensation experiment, the drop distributions advance through two stages: an increase in drop density as a result of nucleation and a decrease in drop density as a result of larger scale coalescence events. Because the experiment is transient in nature, the shape of the distribution can be used to predict the number of drop generations and their stage of development. Preliminary results for gradient surfaces will be discussed and compared against observations of behavior on uniformly coated surfaces. NASA Space Technology Research Fellowship (NSTRF).

  12. Condensing Organic Aerosols in a Microphysical Model

    Science.gov (United States)

    Gao, Y.; Tsigaridis, K.; Bauer, S.

    2015-12-01

    The condensation of organic aerosols is represented in a newly developed box-model scheme, where its effect on the growth and composition of particles are examined. We implemented the volatility-basis set (VBS) framework into the aerosol mixing state resolving microphysical scheme Multiconfiguration Aerosol TRacker of mIXing state (MATRIX). This new scheme is unique and advances the representation of organic aerosols in models in that, contrary to the traditional treatment of organic aerosols as non-volatile in most climate models and in the original version of MATRIX, this new scheme treats them as semi-volatile. Such treatment is important because low-volatility organics contribute significantly to the growth of particles. The new scheme includes several classes of semi-volatile organic compounds from the VBS framework that can partition among aerosol populations in MATRIX, thus representing the growth of particles via condensation of low volatility organic vapors. Results from test cases representing Mexico City and a Finish forrest condistions show good representation of the time evolutions of concentration for VBS species in the gas phase and in the condensed particulate phase. Emitted semi-volatile primary organic aerosols evaporate almost completely in the high volatile range, and they condense more efficiently in the low volatility range.

  13. Tachyon condensation and black hole entropy.

    Science.gov (United States)

    Dabholkar, Atish

    2002-03-04

    String propagation on a cone with deficit angle 2pi(1-1 / N) is considered for the purpose of computing the entropy of a large mass black hole. The entropy computed using the recent results on condensation of twisted-sector tachyons in this theory is found to be in precise agreement with the Bekenstein-Hawking entropy.

  14. Capillary condensation as a morphological transition.

    Science.gov (United States)

    Kornev, Konstantin G; Shingareva, Inna K; Neimark, Alexander V

    2002-02-25

    The process of capillary condensation/evaporation in cylindrical pores is considered within the idea of symmetry breaking. Capillary condensation/evaporation is treated as a morphological transition between the wetting film configurations of different symmetry. We considered two models: (i) the classical Laplace theory of capillarity and (ii) the Derjaguin model which takes into account the surface forces expressed in terms of the disjoining pressure. Following the idea of Everett and Haynes, the problem of condensation/evaporation is considered as a transition from bumps/undulations to lenses. Using the method of phase portraits, we discuss the mathematical mechanisms of this transition hidden in the Laplace and Derjaguin equations. Analyzing the energetic barriers of the bump and lens formation, it is shown that the bump formation is a prerogative of capillary condensation: for the vapor-liquid transition in a pore, the bump plays the same role as the spherical nucleus in a bulk fluid. We show also that the Derjaguin model admits a variety of interfacial configurations responsible for film patterning at specific conditions.

  15. Bose-Einstein condensation in quantum glasses

    OpenAIRE

    2009-01-01

    The role of geometrical frustration in strongly interacting bosonic systems is studied with a combined numerical and analytical approach. We demonstrate the existence of a novel quantum phase featuring both Bose-Einstein condensation and spin-glass behaviour. The differences between such a phase and the otherwise insulating "Bose glasses" are elucidated.

  16. Condensate formation in a Bose gas

    NARCIS (Netherlands)

    Stoof, H.T.C.

    1995-01-01

    Using magnetically trapped atomic hydrogen as an example, we investigate the prospects of achieving Bose-Einstein condensation in a dilute Bose gas. We show that, if gas is quenched sufficiently far into the critical region of the phase transition, the typical time scale for the nucleation of the co

  17. Neutrino emissivity under neutral kaon condensation

    OpenAIRE

    Kubis, Sebastian

    2005-01-01

    Neutrino emissivity from neutron star matter with neutral kaon condensate is considered. It is shown that a new cooling channel is opened, and what is more, all previously known channels acquire the greater emissivity reaching the level of the direct URCA cycle in normal matter.

  18. Interaction between ionic lattices and superconducting condensates

    OpenAIRE

    2007-01-01

    The interaction of the ionic lattice with the superconducting condensate is treated in terms of the electrostatic force in superconductors. It is shown that this force is similar but not identical to the force suggested by the volume difference of the normal and superconducting states. The BCS theory shows larger deviations than the two-fluid model.

  19. Ultrafine Condensation Particle Counter Instrument Handbook

    Energy Technology Data Exchange (ETDEWEB)

    Kuang, C. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2016-02-01

    The Model 3776 Ultrafine Condensation Particle Counter (UCPC; pictured in Appendix A) is designed for researchers interested in airborne particles smaller than 20 nm. With sensitivity to particles down to 2.5 nm in diameter, this UCPC is ideally suited for atmospheric and climate research, particle formation and growth studies, combustion and engine exhaust research, and nanotechnology research.

  20. optimal evaporating and condensing temperatures of organic ...

    African Journals Online (AJOL)

    user

    2017-01-01

    Jan 1, 2017 ... optimal condensing temperature (OCT) of a subcritical ORC plant, which is based on thermodynamic .... evaporator driven by heat from a solar collector, an ... Mass flow and energy flow through the plant were ..... Thermal PVT Water Collector,” Sol. ... techniques of hybrid renewable energy systems for.