1-methyluracil crystal

Figure 4. Comparison between the experimental (solid bold line) and theoretical v spectra of 1-methyluracil crystal (anharmonic calculation—Dirac 5 functions and thin solid line harmonic calculation—dashed line) for the 1-methyluracil crystal (a) and the deuterated crystal (b). Figure reprinted with permission from Ref. 58. Copyright American Institute of Physics Publishing LLC.

Boyarchuk and Volkenshtein354,355 have studied the IR spectra of the crystals of 5-bromo-l-methyl-, 5-bromo-3-methyluracil, and 1-methylthymine and discussed the effect of the electronegative substituents in the pyrimidine ring on the potential energy curve of dimeric hydrogen-bonded complexes of uracil derivatives. Features of the IR spectrum of 5-bromo-l-methyluracil crystal suggested that the stability of the lactim form 28 increases owing to the influence of the substituents. 

Mixed Crystal Systems. - 2.6.1 Co-crystals. l-Methyluracil 9-ethyladenine (Radicals 31-37)... 

A single crystal l-methyluracil 9-ethyladenine complex was investigated using EPR, ENDOR and FSE.25 Samples were x-irradiated and spectra taken at 10 K. This work is a reinvestigation of a system that had been studied using EPR only after irradiation at 295 K.26 Three radicals were identified in 1-methyluracil, the net methyl-hydrogen-loss radical (31), (see p. 258) the anion radical (32), and the... 

Russo N, Toscano M, Grand A (2000) Theoretical determination of electron affinity and ionization potential of DNAand RNA bases. J Comput Chem 21 1243-1250 Sagstuen E, Hole EO, Nelson WH, Close DM (1998) Radiation damage to DNA base pairs. II. Paramagnetic resonance studies of 1 -methyluracil. 9-ethyladenine complex crystals X-irradiated at 10 K. Radiat Res 149 120-127... 

Although blues prepared from unsubstituted uracil, thymine and related bases (e.g., 6-methyluracil, 5,6-dihydrouracil etc.) were the first to be prepared and tested, their composition is the least clear. The author suspects that there is still long way to go to fully understand the nature of these blues . It is possible that there are even blues built on different principles. A main obstacle to the elucidation of Pt blues derived from the unsubstituted pyrimidine nucleobases lies in their versatility as ligands. Not only is there the possibility that these ligands bind to metal ions, specifically Pt, via N(l) or N(3) or (only with uracil) C(5), but also many possible combinations of two or more binding sites, e.g., N(l),0(2) N(3),0(2) N(3),0(4) N(1),N(3) N(3),0(2),0(4) N(1),0(2),N(3),0(4) etc. (Scheme 6). A series of these binding patterns has been established by X-ray crystal-structure analyses [68-70], and others are likely on the basis of spectroscopic studies [71] [72] or from comparison with results obtained for N(l) substituted derivatives. The possibility of different tautomers of platinated forms being... 

The adenine cation has not been confidently assigned through comparison of calculated HFCCs and those obtained from single crystals of nonprotonated adenine derivatives unless co-crystallized with another base derivative. However, a study performed on the co-crystals of 1-methyluracil and 9-ethyladenine detected the adenine cation at 10 K [100] and the HFCCs agree well with the calculated values. Furthermore, the cation can be observed in protonated crystals [15]. The extreme conditions at which the adenine cation was observed in these studies are not evident in frill DNA. 

LaBrecque et al. (1960), Kilgore and Painter (1964), and Crystal (1963, 1967) established the insect sterilising potency of several known nucleobase-antimetabolites, such as S-fluorouracil (24), S-bromouracil (25), 6-methyluracil (26), S-fluoroorotic acid (27) and 2,6-diaminopurine (28). 

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