Wyniki wyszukiwania - Biblioteka Nauki

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Time-dependent density functional theory molecular dynamics simulation of doubly charged uracil in gas phase

100%

López-Tarifa P. , Hervé du Penhoat M.-A. , Vuilleumier R. , Gaigeot M.-P. , Rothlisberger U. , Tavernelli I. , Le Padellec A. , Champeaux J.-P. , Alcamí M. , Moretto-Capelle P. , Martín F. , Politis M.-F.

Open Physics

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2014

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tom 12

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nr 2

97-102

EN

We use time-dependent density functional theory and Born-Oppenheimer molecular dynamics methods to investigate the fragmentation of doubly ionized uracil in gas phase. Different initial electronic excited states of the dication are obtained by removing electrons from different inner-shell orbitals of the neutral species. We show that shape-equivalent orbitals lead to very different fragmentation patterns revealing the importance of the intramolecular chemical environment. The results are in good agreement with ionion coincidence measurements of uracil collision with 100 keV protons.

2

Powstanie niebezpiecznych związków podczas chlorowania wody zawierającej uracyl

100%

Kucharski M.

Zeszyty Naukowe Politechniki Białostockiej. Matematyka, Fizyka, Chemia

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1998

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tom Z. 18

9-19

PL

W pracy przedstawiono wyniki badań nad reakcją przebiegającą w wodzie między chlorem (wodnym chlorem pozostałym), a uracylem w zakresie stosunków molowych; wolny chlor pozostały: uracyl (WChP : Ur) wynoszącym od 0,25 do 10 mol/mol. Badano także wpływ pH oraz obecność jonów bromkowych, jodkowych i fluorkowych na przebieg tej reakcji. Ustalono, że przy niskim współczynniku WChP : Ur jedynym produktem chlorowania jest 5-chlorouracyl, a przy wysokim współczynniku (powyżej 10) brak jest chlorouracylu w produktach chlorowania. Obecność w badanych roztworach bromków i jodków powoduje powstawanie 5-bromo- i 5-jodouracylu.

EN

The object of the research was reaction between free available chloride (FAC) and (Ur) over the range FAC to uracil ration between 0,25 and 10 mol/mol and over pH range of 6-9. Determined that, at low FAC/uracil rations chlorination product was only 5-chlorouracil, a the higher FAC/uracil rations inproducts were dichlorouracil and nitrogen trichloride. In presense of added iodide or bromide, the chlorination leads to produce in addition to 5-chlorouracil, important quantities of 5-iodouracil and 5-bromouracil respectively.

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Partial molar heat capacities of aqueous solution of some halo- and amino-derivatives of uracil

100%

Zielenkiewicz A. , Zielenkiewicz W.

Bulletin of the Polish Academy of Sciences. Chemistry

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1999

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tom Vol. 47, No. 3

266-271

EN

Apparent molar heat capacities of aqueous solutions of uracil, 5-fluorouracil, 5-chlorouracil, 6-chlorouracil, 5-bromouracil, 5-iodouracil, 5-aminouracil, 6-aminouracil, 6-amino-1,3-dimethyluracil, 5-nitrouracil were determined at 25 °C, 35 °c and 45 °c using a differential adiabatic scanning microcalorimeter DASM-4. The partial molar heat capacities 02,2 at 25 ° C, 35 ° C and 45 ° C were evaluated, discussed and correlated with surface accessible areas of compounds studied.

4

The pH optimum of native uracil-DNA glycosylase of Archaeoglobus fulgidus compared to recombinant enzyme indicates adaption to cytosolic pH

88%

Knævelsrud I. , Kazazic S. , Birkeland N.-K. , Bjelland S.

Acta Biochimica Polonica

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2014

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tom 61

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nr 2

393-395

EN

Uracil-DNA glycosylase of Archaeoglobus fulgidus (Afung) in cell extracts exhibited maximal activity around pH 6.2 as compared to pH 4.8 for the purified recombinant enzyme expressed in Escherichia coli. Native Afung thus seems to be adapted to the intracellular pH of A. fulgidus, determined to be 7.0±0.1. Both recombinant and native Afung exhibited a broad temperature optimum for activity around 80°C, reflecting the A. fulgidus optimal growth temperature of 83°C. Adaption to the neutral conditions in the A. fulgidus cytoplasm might be due to covalent modifications or accessory factors, or due to a different folding when expressed in the native host.

5

Change of Prototropic Equilibria for Uracil when Going from Neutral Molecule to Charged Radicals. Quantum-Chemical Studies in the Gas Phase

75%

Raczyńska E. D. , Zientara K. , Kolczyńska K. , Stępniewski T. M.

Polish Journal of Chemistry

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2009

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tom Vol. 83, nr 5

821-834

EN

To understand various substitution, oxidation or degradation reactions for uracil, quantum-chem i calcalculations were performed for two classes of charged radicals (cations and anions) of uracil (U+ź and U-ź) and model compounds: phenol (P+ź and P-ź) and hydroxyazines (HP1-4+ź and HP1+-4-ź). In calculations, all possible eighteen prototropic tautomers-rotamers of U and all possible five prototropic tautomers-rotamers of P and HP1-4 were considered. Stabilities, internal effects and aromatic character, estimated for charged radicals, were compared with those observed previously for neutral molecules. The great est changes of the tautomeric preferences take place for radical anions. One-electron reduction stabilizes the keto and amide functions in studied compounds, whereas one-electron oxidation favors the enol function for ph nol and the amide function for uracil and hydroxyazines.

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Metody syntezy siarkowych pochodnych zasad pirymidynowych

63%

Nowakowska Z. , Wyrzykiewicz E.

Wiadomości Chemiczne

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1998

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tom [Z] 52, 5-6

449-466

EN

Uracil thio-derivatives have become to play increasingly important roles in biology and medicine. Numerous sulphur-substituted pyrimidines have found applications as clinically useful drugs. Thiouracils have recently been the subject of considerable interest as they inhibit hyperthyroidism in man [1, 2], have been isolated from E. Coli tRNA [3], and inhibit virus [4] and bacterial growth [5] by causing alterations [6] in protein synthesis. Thiouracils are also of interest because of mutagenic [7], anticancer and antithyroid activity [8], kidney stone formation inhibition [9] and antidote properties for mercury poisoning . Two of them, 2-thiouracil and 6-propyl-2-thiouracil, exhibit marked affinities for melanin-producing tissue in vitro and a similar affinity in vivo, where they presumably act as false precursors for melanin [10, 11]. Boron-containing derivatives of thiouracils [12-14] containing a dihydroxyboryl (or 1-o-carboranylalkyl) group in the 5-position are very important because of their potential applications for BNCT. Human immunodeficiency virus type 1 (HIV-1) is the causative agent of acquired immunodeficiency syndrome (AIDS), which is one of the world's most serious health problems. Since the discovery of the acyclic 6-substituted uridine derivative 1-[(2-hydroxyethoxy0methyl]-6-(phenythio)-thymine (HEPT) as a novel lead for specific anti-HIV-1 agents [15], a number of HEPT analogs have been synthesized to increase its potency [16-18]. The studies of the structure-activity relationships of HEPT analogs indicated that replacement of the 2-oxo function with a thine function potentiated their anti-HIV-1 activity [16, 19, 20]. Therofore the synthesis of thio-substituted pyrimidine bases and their derivatives appears to be a challenge for organic chemists. The methods of preparation of these compounds have been reviewed.

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Modelowanie właściwosci wiązań wodorowych na przykładzie kompleksów układ amidowy - woda

63%

Rzepiela K. , Buczek A. , Kupka T. , Kar T. , Broda M. A.

Wiadomości Chemiczne

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2023

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tom [Z] 77, 7-8

629--645

EN

The energy and structure of intermolecular hydrogen bonds between water molecule and N-methylamide (NMA) or uracil (U) are discussed on the basis of DFT calculations. Theoretical methods are applied to calculate properties of cis- and trans- NMA complexes with one water molecule. Subsequently, H-bonds in six uracil – water complexes are analyzed. The influence of dispersion interactions and the polar environment on the hydrogen bond energy was analyzed. Results obtained by B3LYP functional with and without Grimme D3 dispersion correction indicate that dispersion interaction plays a significant role in an association process. In addition, the polar solvent reduces the hydrogen bond energy and this reduction is directly proportional to the hydrogen bond energy.

8

The activity of dihydropyrimidine dehydrogenase and mRNA expression in human blood cells

63%

Van Kuilenburg A. B. P. , Vreken P. , Van Lenthe H. , Meinsma R. , Van Gennip A. H.

Cellular and Molecular Biology Letters

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1999

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tom 04

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nr 3

9

Capillary electrophoresis as a tool for determining the level of orotic acid and uracil in patients with urea cycle defects

63%

Salerno C. , D'Eufemia P. , Celli M. , Finocchiaro R. , Crifo C. , Giardini O.

Cellular and Molecular Biology Letters

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1999

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tom 04

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nr 3

10

Plasmalemma H - ATPase of plant and yeast origin

51%

Kotyk A.

Biophysics of Membrane Transport

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1992

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tom 11

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nr 1