Sample records for bromouracils

  1. Negative ion states of 5-bromouracil and 5-iodouracil. (United States)

    Kossoski, F; Varella, M T do N


    The valence anion states of the potential radiosensitisers 5-bromouracil and 5-iodouracil were investigated through elastic scattering calculations. These compounds have rich spectra of negative ion states that trigger off different mechanisms for dissociative electron attachment. For each molecule, we obtained a bound π* anion, two π* shape resonances and a low lying σ* anion state, in addition to a dipole-bound state (the latter was obtained using bound-state techniques). The σ* anion, formed by electron attachment to an anti-bonding carbon-halogen orbital, was found to have resonant character in 5-bromouracil, and bound-state character in 5-iodouracil. The present calculations place the σCBr* resonance around 0.7 eV, considerably below the energy inferred from the electron transmission data (1.3 eV). The signature of this anion state, not evident in the measurements, would be obscured by the large background arising from the dipolar interaction, not by the strong signature of the π2*, as presumed. Our results support the π2* resonance as a precursor state to dissociative electron attachment around 1.5 eV in both 5-bromouracil and 5-iodouracil, while the interplay among π1*, σ* and dipole-bound states would be expected close to 0 eV. We also discuss the suppression of the hydrogen elimination channels in these species.

  2. Insights into the deactivation of 5-bromouracil after ultraviolet excitation (United States)

    Peccati, Francesca; Mai, Sebastian; González, Leticia


    5-Bromouracil is a nucleobase analogue that can replace thymine in DNA strands and acts as a strong radiosensitizer, with potential applications in molecular biology and cancer therapy. Here, the deactivation of 5-bromouracil after ultraviolet irradiation is investigated in the singlet and triplet manifold by accurate quantum chemistry calculations and non-adiabatic dynamics simulations. It is found that, after irradiation to the bright ππ* state, three main relaxation pathways are, in principle, possible: relaxation back to the ground state, intersystem crossing (ISC) and C-Br photodissociation. Based on accurate MS-CASPT2 optimizations, we propose that ground-state relaxation should be the predominant deactivation pathway in the gas phase. We then employ different electronic structure methods to assess their suitability to carry out excited-state dynamics simulations. MRCIS (multi-reference configuration interaction including single excitations) was used in surface hopping simulations to compute the ultrafast ISC dynamics, which mostly involves the 1nOπ* and 3ππ* states. This article is part of the themed issue 'Theoretical and computational studies of non-equilibrium and non-statistical dynamics in the gas phase, in the condensed phase and at interfaces'.

  3. Heterogeneous photocatalyzed degradation of uracil and 5-bromouracil in aqueous suspensions of titanium dioxide

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    Singh, H.K. [Department of Chemistry, Aligarh Muslim University, Aligarh 202002 (India); Saquib, M. [Department of Chemistry, Aligarh Muslim University, Aligarh 202002 (India); Haque, M.M. [Department of Chemistry, Aligarh Muslim University, Aligarh 202002 (India); Muneer, M. [Department of Chemistry, Aligarh Muslim University, Aligarh 202002 (India)]. E-mail:


    Photocatalyzed degradation of uracil (1) and 5-bromouracil (2) has been investigated in aqueous suspensions of titanium dioxide under a variety of conditions. The degradation was studied by monitoring the change in substrate concentration employing UV spectroscopic analysis technique and depletion in total organic carbon (TOC) content as a function of irradiation time. The degradation of the compounds under investigation was studied using various parameters such as, different types of TiO{sub 2} powders, pH, catalyst concentration, substrate concentrations, and in the presence of electron acceptors like hydrogen peroxide (H{sub 2}O{sub 2}) and potassium bromate (KBrO{sub 3}) besides molecular oxygen. Photocatalyst Degussa P25 was found to be more efficient for the degradation of both compounds as compared with other TiO{sub 2} powders such as UV100, PC500 and TTP.

  4. Photodimerization in pyrimidine-substituted dipeptides

    DEFF Research Database (Denmark)

    Lohse, Brian; Ramanujam, P.S.; Hvilsted, Søren


    was compared in aqueous solution: it was dependent on the substitution of the pyrimidine ring. N-alpha,N-alpha'-bis-(uracil-1-ylacetyl)-(N-epsilon-glycylomithineamide) and N-alpha,N-alpha'-bis-(5-bromouracil-1-ylacetyl)-(N-epsilon-glycylomithineamide) were identified as possible candidates for optical data...

  5. Sequence-specific electron injection into DNA from an intermolecular electron donor. (United States)

    Morinaga, Hironobu; Takenaka, Tomohiro; Hashiya, Fumitaka; Kizaki, Seiichiro; Hashiya, Kaori; Bando, Toshikazu; Sugiyama, Hiroshi


    Electron transfer in DNA has been intensively studied to elucidate its biological roles and for applications in bottom-up DNA nanotechnology. Recently, mechanisms of electron transfer to DNA have been investigated; however, most of the systems designed are intramolecular. Here, we synthesized pyrene-conjugated pyrrole-imidazole polyamides (PPIs) to achieve sequence-specific electron injection into DNA in an intermolecular fashion. Electron injection from PPIs into DNA was detected using 5-bromouracil as an electron acceptor. Twelve different 5-bromouracil-containing oligomers were synthesized to examine the electron-injection ability of PPI. Product analysis demonstrated that the electron transfer from PPIs was localized in a range of 8 bp from the binding site of the PPIs. These results demonstrate that PPIs can be a useful tool for sequence-specific electron injection.

  6. Two-Step Fuzzy Multicriteria Ranking of Whole Cells Immobilization Methods for Biosensor/Biocatalyst Selection/Synthesis (United States)

    Blancafort, Lluís; Asturiol, David; Migani, Annapaola; Kobyłecka, Monika; Rak, Janusz


    The photochemically induced dimerization of thymine and the photodecomposition of 5-bromouracil are investigated using the CASSCF (complete active space self-consistent field) and CASPT2 (complete active space second order perturbation) methodologies, where excited state reaction paths are calculated with CASSCF, and the energies refined with CASPT2. The studies focus on the central role of conical intersections for the ultrafast decay and the reactivity.


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    Jayaseelan Aravind


    Full Text Available The effect of mutagenic agents on Polyhydroxyalkanoates (PHA accumulation was investigated in two micro-organisms Cupriavidus nectar and Kluyvera intermedia. Three mutagenic agents- ultraviolet light, heat, chemical mutagens (acriflavin and 5 bromouracil were selected for the study. The cultures were treated at various time intervals and chemical at varying concentration and cultured using hydrolyzed grass (cyanodon dactylon as a substrate. It was found that higher accumulation was obtained in C. nectar when treated at a concentration of 50µg/ ml acriflavin and 5 bromouracil (25µg/ ml. K. intermedia showed a higher accumulation at acriflavin concentration of just 25µg/ ml and 5- bromouracil at 50µg/ ml concentrations. It was observed that % PHA accumulation significantly decreased with increase in exposure to UV in both C. nectar (17 % - 1.18% and K. intermedia (15 % - 7%. Exposure of culture to heat resulted in less PHA accumulation in C. nectar (16 % - 11%, K. intermedia (17 % - 19 % compared to their parent strain C. nectar (17 % and K. intermedia (25 %. FTIR spectra revealed the presence of characteristic medium chain length (mcl PHA in the obtained sample.

  8. Effects of some inhibitors of protein synthesis on the chloroplast fine structure, CO2 fixation and the Hill reaction activity

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    S. Więckowski


    Full Text Available A comparative study concerning the effects of chloramphenicol (100 μg ml-1, actidione (10 μg ml-1, 5-bromouracil (190 μg ml-1, actinomycin D (30 μg ml-1 and DL-ethionine (800 μg ml-1 on the chloroplast fine structure, 14CO2 incorporation and the Hill reaction activity was the subject of the experiments presented in this paper. The experiments were conducted on bean seedlings under the conditions when chlorophyll accumulation was inhibited only partially. The results obtained indicate that chloromphenicol is responsible for the reduction of the number of grana per section of plastid and for the formation of numerous vesicles in the stroma. In the presence of actidione, actinomycin D or DL-ethionine the lamellae are poorly differentiated into .stroma and granum regions and there occur disturbances in the typical orientation of lamellae within chloroplasts. Only in the presence of 5-bromouracil the development of chloroplast structure resemble that in control plants. A comparison of the results obtained with those published earlier (Więckowski et al., 1974; Ficek and Więckowski, 1974 shows that such processes as assimilatory pigment accumulation, the rate of CO2 fixation, the Hill reaction activity, and the development of lamellar system are suppressed in a different extent by the inhibitors used.

  9. Catabolism of exogenously supplied thymidine to thymine and dihydrothymine by platelets in human peripheral blood

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    Pero, R.W.; Johnson, D.; Olsson, A.


    The interference of platelets with the estimation of unscheduled DNA synthesis in human peripheral mononuclear leukocytes following genotoxic exposure was studied. A 96% reduction in the unscheduled DNA synthesis value was achieved by incubating (/sup 3/H)thymidine with platelet-rich plasma for 5 hr at 37 degrees. Using radioactive thymine-containing compounds, together with quantitative analyses based on thin-layer and ion-exchange chromatographies, we have shown that thymidine was converted to thymine which, in turn, was converted to dihydrothymine in platelet-rich plasma. The enzymes responsible were separated from platelet lysates by gel filtration and were identified as thymidine phosphorylase and dihydrothymine dehydrogenase. The phosphorylase reversibly catalyzed the formation of thymine from thymidine and converted bromodeoxyuridine to bromouracil. The dehydrogenase reversibly catalyzed the interconversion of thymine and dihydrothymine in a reaction dependent on NADP(H), and it was inhibited by diazouracil and by thymine. Nearly all the thymidine-catabolizing activity found in whole blood samples supplied exogenously with thymidine was accounted for by the platelets. Since most genetic toxicological tests that use blood samples do not involve removing platelets from the blood cell cultures, then it is concluded that precautions should be taken in the future to determine the influence of platelets on these test systems. This is particularly true for methods dependent on thymidine pulses such as unscheduled DNA synthesis, or those dependent on bromodeoxyuridine, such as sister chromatid exchanges, since this nucleoside is also a substrate for thymidine phosphorylase.

  10. [Influence of the selected pyrimidine compounds on the activity of thymidine phosphorylase from normal and tumor endometrial cells]. (United States)

    Miszczak-Zaborska, Elzbieta; Smolarek, Monika; Dramiński, Marcin; Kubiak, Robert; Józwiak, Barbara; Bartkowiak, Jacek


    The aim of this study was to evaluate the influence of the selected pyrimidine compounds on the activity of thymidine phosphorylase (TP) of normal and tumor endometrial cells. Influence of 28 chemical compounds on the TP activity in the cytosol of the endometrial cells was studied by the spectrophotometric method. The studied group comprised postmenopausal women with endometrial cancer: adenocarcinoma endometrialis (Adeno Ca E). The second group included women with normal endometrium after surgery due to non-oncologic reasons. The most potent inhibitor of TP activity from cancer and endometrium was synthesized 5-bromo-6-acetyloaminouracil, which at the 0.2 mM concentration, by 0.2 mM concentration thymidine reduced the cytosol TP activity by about 80%. 5-bromo-6-aminouracil, 5-nitrouracil and 5-bromouracil reduced this TP activity in statistically significant manner. From among synthesized 1-N-allyloxymethylpyrimidine derivatives 1-N-allyloxymethylthymine was the strongest inhibitor of the TP activity in endometrium, and 1-N-allyloxymethyl-4-hydrokxy-5-nitro-6-oxopyrimidine in endometrial cancer respectively. The most potent activators of TP in endometrial cancer was 5-bromodeoxyuridine and 1-N-allyloxymethyl-5-nitrouracil, which increased the TP activity about 100%. 5-fluorodeoxyuridine, 5-jododeoxyuridine and 2'-deoxyuridine activated the TP in statistically significant manner too, but stronger in case of endometrial cancer than in normal endometrium. The synthesized 5-bromo-6-acetyloaminouracil strongly inhibited the TP activity of endometrial cells and might be useful in reducing endometrial cancer angiogenesis. On the other hand 5-bromodeoxyuridine and the synthesized 1-N-allyloxymethyl-5-nitrouracil might increase the effect of antitumor therapy with the cytostatics. These conclusions ought to be confirmed by analyzing more tumor cases.