- Meteorite-catalyzed intermoleculartrans-glycosylation produces nucleosides under proton beam irradiation
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Di-glycosylated adenines act as glycosyl donors in the intermoleculartrans-glycosylation of pyrimidine nucleobases under proton beam irradiation conditions. Formamide and chondrite meteorite NWA 1465 increased the yield and the selectivity of the reaction
- Bizzarri, Bruno Mattia,Fanelli, Angelica,Kapralov, Michail,Krasavin, Eugene,Saladino, Raffaele
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p. 19258 - 19264
(2021/06/03)
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- Effect of base stacking on the acid-base properties of the adenine cation radical [A?+] in solution: ESR and DFT studies
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In this study, the acid-base properties of the adenine cation radical are investigated by means of experiment and theory. Adenine cation radical (A?+) is produced by one-electron oxidation of dAdo and of the stacked DNA-oligomer (dA)6 by Cl2?- in aqueous glass (7.5 M LiCl in H2O and in D2O) and investigated by ESR spectroscopy. Theoretical calculations and deuterium substitution at C8-H and N6-H in dAdo aid in our assignments of structure. We find the pKa value of A?+ in this system to be ca. 8 at 150 K in seeming contradiction to the accepted value of ≤1 at ambient temperature. However, upon thermal annealing to ≥160 K, complete deprotonation of A?+ occurs in dAdo in these glassy systems even at pH ca. 3. A?+ found in (dA)6 at 150 K also deprotonates on thermal annealing. The stability of A?+ at 150 K in these systems is attributed to charge derealization between stacked bases. Theoretical calculations at various levels (DFT B3LYP/6-31G*, MPWB95, and HF-MP2) predict binding energies for the adenine stacked dimer cation radical of 12 to 16 kcal/mol. Further DFT B3LYP/6-31G* calculations predict that, in aqueous solution, monomeric A?+ should deprotonate spontaneously (a predicted pKa of ca. -0.3 for A?+). However, the charge resonance stabilized dimer AA?+ is predicted to result in a significant barrier to deprotonation and a calculated pK a of ca. 7 for the AA?+ dimer which is 7 pH units higher than the monomer. These theoretical and experimental results suggest that A?+ isolated in solution and A?+ in adenine stacks have highly differing acid-base properties resulting from the stabilization induced by hole derealization within adenine stacks.
- Adhikary, Amitava,Kumar, Anil,Khanduri, Deepti,Sevilla, Michael D.
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experimental part
p. 10282 - 10292
(2009/02/03)
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- 2'-deoxy-L-nucleosides
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This invention provides processes for the preparation of compounds having the structure: wherein X and Y are same or different, and H, OH, OR, SH, SR, NH2, NHR′, or NR′R″Z is H, F, Cl, Br, I, CN, or NH2. R is hydrogen, halogen, lower alkyl of C1-C6 or aralkyl, NO2, NH2, NHR′, NR′R″, OH, OR, SH, SR, CN, CONH2, CSNH2, CO2H, CO2R′, CH2CO2H, CH2CO2R′, CH═CHR, CH2CH═CHR, or C═CR. R′ and R″ are same or different, and lower alkyl of C1-C6. R13 is hydrogen, alkyl, acyl, phosphate (monophosphate, diphosphate, triphosphate, or stabilized phosphate) or silyl; and
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Page/Page column 38
(2010/02/11)
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- A new and convenient approach for the synthesis of rffio- and 2′-deoxyrffio-p-l-furanonucleosides starting from β-l-xylofuranonucleosides
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Ribo- and 2′-deoxyribo-β-L-ruranosyladenine have been synthesized. Although these compounds have been already reported in the literature, it seemed to us that a more convenient approach for their synthesis deserved to be developed. Intramolecular substitution as well as Mitsunobu reaction were used to invert the configuration of carbon 3′ of starting β-L-xylofuranosyl intermediates. Copyright
- Boudou
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p. 607 - 609
(2007/10/03)
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- Ionization of purine nucleosides and nucleotides and their components by 193-nm laser photolysis in aqueous solution: Model studies for oxidative damage of DNA 1
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The effect of 20-ns pulses of 193-nm laser light on aqueous solutions of purine bases, (2′-deoxy)nucleosides, and (2′-deoxy)nucleotides was investigated, and monophotonic ionization was observed. Although (deoxy)ribose and (deoxy)ribose phosphates are also ionized by 193-nm light, the photoionization of the (deoxy)nucleosides and -tides takes place predominantly (90%) at the purine moiety, due to the much higher extinction coefficients at 193 nm of the bases as compared to the (deoxy)ribose phosphates. The quantum yields of photoionization (φPl) of the purines are in the range 0.01 to 0.08, based on φ(Cl-) at 193 nm of 0.46. As shown by comparison with data obtained from pulse radiolysis, the ionized purines, i.e., the radical cations, deprotonate in neutral solution, yielding neutral radicals. The radical cation of 1-methylguanosine, produced by photoionization in oxygen-saturated aqueous solution, deprotonates with the rate constant 3.5 × 105 s-1. In the absence of oxygen, the hydrated electrons resulting from the photoionization react with the untransformed purine derivatives to yield the corresponding radical anions. As these are rapidly protonated by water (as concluded from pulse radiolysis), the photoionization in deaerated neutral solution results in two different neutral radicals: a deprotonated radical cation and a protonated radical anion.
- Candeias,Steenken
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p. 699 - 704
(2007/10/02)
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- L-thymidine is phosphorylated by herpes simplex virus type 1 thymidine kinase and inhibits viral growth
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We have demonstrated that herpes simplex 1 (HSV1) thymidine kinase (TK) shows no stereospecificity for D- and L-β-nucleosides. In vitro, L enantiomers are not recognized by human TK, but function as specific substrates for the viral enzyme in the order: L-thymidine (L-T) >> 2'-deoxy- L-guanosine (L-dG) > 2'-deoxy-L-uridine (L-dU) > 2'-deoxy-L-cytidine (L-dC) > 2'-deoxy-L-adenosine (L-dA). HSV1 TK phosphorylates both thymidine enantiomers to their corresponding monophosphates with identical efficiency and the K(i) of L-T (2 μM) is almost identical to the K(m) for the natural substrate D-T (2.8 μM). The L enantiomer reduces the incorporation of exogenous [3H]T into cellular DNA in HeLa TK-/HSV1 TK+ but not in wild-type HeLa cells, without affecting RNA, protein synthesis, cell growth, and viability. L-T markedly reduces HSV1 multiplication in HeLa cells. Our observations could lead to the development of a novel class of antiviral drugs characterized by low toxicity.
- Spadari,Maga,Focher,Ciarrocchi,Manservigi,Arcamone,Capobianco,Carcuro,Colonna,Iotti,Garbesi
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p. 4214 - 4220
(2007/10/02)
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