Cytidine monohydrate, crystal structure

Cyclic Trimer Configuration. The a-cytidine [ACYTID] crystal structure contains two cyclic trimer configurations (Fig. 17.32). In one, N(H)H is engaged in a three-center bond, the other is a homodromic cycle stabilized by a- and w-cooperativity. A comparable situation is found in the crystal structure of a-pseudouridine monohydrate [APSURD] (Fig. 17.13). The glycosyl link is to uracil C(6) instead of N(l), and therefore the N(1)H group is free to donate a hydrogen bond in a homodromic cycle. 

If the crystal structures and hydrogen-bonding patterns of uridine and thymidine and their simpler derivatives are compared with those of cytidine, it becomes obvious that the -NH2 functional group has a characteristic influence. The nucleosides without the -NH2 groups have less than average hydrated crystals, although the one nucleotide represented, uridine-3 -monophosphate, crystallizes as a monohydrate. 

Rosenberg JM, Seeman NC, Day RO, Rich A (1976) RNA double-helical fragment at atomic resolution. II. The crystal structure of sodium guanylyl-3, 5 -cytidine monohydrate. J Mol Biol 104 145-167... 

Nucleoades and their Analogues and Derivatives Thereof. - 5-Acetyi-l-(3,5-0-isopropylidene-a-D-xylofuranosyl)uracil monohydrate has the furanose ring in a C2 -endo, C3 -endo conformation and a glycosidic torsion angle of —31°. X-ray structures of adenosine, cytidine, uridine and thymidine were interpreted in terms of C-H-- 0 interactions, while guanosine lacks these interactions. Another structural analysis of cytidine was reported and studies of crystal... 

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