NMR studies of nucleic acids. Deuterium isotope effects on sup 13 C chemical shifts in hydrogen-bonded complexes of pyrimidines and purines
{sup 13}C NMR spectra were recorded for chloroform solutions of 2',3'-O-isopropylidene-5'-O-acetyladenosine (1), 2',3',5'-O-tribenzoyluridine (2), 2',3'-O-isopropylidene-5'-O-acetyluridine (2a), 2',3'-O-isopropylidene-5'-O-(tert-butyldimethylsilyl)guanosine (3), and 2',3'-O-isopropylidene-5'-O-(tert-butyldimethylsilyl)cytidine (4) in which the imino hydrogens were partially exchanged with deuterium. Upfield two-bond deuterium isotope effects (DIE) on {sup 13}C chemical shifts were detected under conditions of slow exchange as multiple peaks for the appropriate resonances and ranged in magnitude from 40 ppB for the amino interaction with C2 in guanosine to 217 ppB for the imino interaction with C4 in the uridine self-association dimer. {sup 13}C chemical shifts and DIEs for 2 were measured at 12 different concentrations from 219 to 231 K. The data were used in an iterative procedure to estimate chemical shifts at C2 and C4 for monomeric and dimeric forms of 2, equilibrium constants and enthalpies for self-association, and the distribution of isomeric self-association dimers. Enthalpies for formation of hydrogen bonds to C2 and C4 in 2 were similar, {Delta}H = {minus}1.8 kcal/mol. DIEs at C2 and C4 increased upon formation of a hydrogen bond to the carbonyl oxygens. The maximal increase for each center was estimated to be 90 ppB. Small increases were also observed in DIEs when nucleosides 1-4 were mixed with their complementary bases. 38 refs., 3 figs., 7 tabs.
- OSTI ID:
- 5208219
- Journal Information:
- Journal of the American Chemical Society; (USA), Journal Name: Journal of the American Chemical Society; (USA) Vol. 110:23; ISSN 0002-7863; ISSN JACSA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400201* -- Chemical & Physicochemical Properties
400202 -- Isotope Effects
Isotope Exchange
& Isotope Separation
AROMATICS
AZAARENES
AZINES
CARBON 13
CARBON ISOTOPES
DEUTERIUM
EVEN-ODD NUCLEI
HETEROCYCLIC COMPOUNDS
HYDROGEN ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPE EFFECTS
ISOTOPES
LIGHT NUCLEI
NMR SPECTRA
NUCLEI
NUCLEIC ACIDS
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PURINES
PYRIMIDINES
SPECTRA
STABLE ISOTOPES
TRACER TECHNIQUES