Oxygen-17 NMR of nucleosides. 2. Hydration and self-association of uridine derivatives

17O NMR of nucleosides. 3—Chemical shifts of substituted uridines and ribothymidines

“…1 for the Urd > CMe, hydrogen bonded dimer at 56 "C) and by others using different t e c h n i q~e s .~~,~~ Therefore, at the concentrations (<0.1 M) and temperatures used in these experiments, such self-association would account for no more than 2-4ppm, as was found in the previous detailed study of -Urd > CMe2. 4 The possibility of intramolecular hydrogen bonding in uridine and thymidine derivatives is more difficult to determine unequivocally using experimental evidence. The possibility of such base to sugar hydrogen bonds between 0-2 and the 2'-OH are precluded in the 2',3'-blocked derivatives.…”

Combined use of Overhauser spectroscopy and NMR diffusion experiments for mapping the hydration structure of nucleosides: structure and dynamics of uridine in water

“…The first one concerns the hydration of the nucleoside 2 0 , 3 0 O-isopropylidene-uridine (IPU), which has been derived two decades earlier by monitoring oxygen-17 chemical shifts specifically enriched at either O4 or O2. 30 The authors have shown that hydrogen bonding between each carbonyl group of the nucleoside and one water molecule is highly likely. Their data are consistent with a model in which an individual H 2 O can form two distinct types of hydrogen bonds, an 'L' bond from a line electron pair on the oxygen and a 'P' bond from the hydrogen.…”

“…Their data are consistent with a model in which an individual H 2 O can form two distinct types of hydrogen bonds, an 'L' bond from a line electron pair on the oxygen and a 'P' bond from the hydrogen. 30 Very recently, by studying solvent effects on the Raman spectra of thymine and thymidine, Loppnow et al 31 have also reported strong hydrogen-bonding interaction between the N-H proton of the thymidine base and the lone pairs of the water molecules, on one hand, and between the water hydrogens and the lone pairs on C O sites, on the other. The main conclusion of these two independent observations is that they are fully consistent with the crude model of uridine hydration, as proposed according to the Scheme 1(a).…”

Calculating the Thermodynamics of Weakly Hydrogen‐Bonded Complexes from Heteronuclear NMR Data: Base‐pairing stabilities of a 5‐methyl(15N2)[O2, O4‐17O2]uridine (= (15N2)[O2,O4‐17O2]ribosylthymine) derivative, and structural implications

“…It should be emphasized that the adenine-uracil pairing and uracil selfpairing thermodynamics were already calculated from IR experiments in the late sixties [ 11 [2]. Similarly, nucleobase and nucleoside pairing properties were studied by 'H- [3], "N- [4], 13C- [5] [6], and I70-NMR spectroscopy [6] [7], but the thermodynamics were calculated only from a minor part of this data. In particular, no thermodynamics of the adenosine-uridine pairing on the nucleoside level were calculated from "N-NMR data.…”

“…According to the literature, I70-NMR spectroscopy is a very sensitive method for the detection of H-bonds involving various compounds (see e.g. [6] [7] [ 151 [ 161). The removal or addition of an 0-bound proton is accompanied by a significant change in the chemical shift d(0); so is the deprotonation of an 0-containing functional group where the proton was not necessarily bound to the 0-atom (e.g.…”