The determination of the energetics of the temperature-dependent two-state N $ S pseudorotational equilibrium through 3JHH analysis in 36 nucleos(t)ides and 3 abasic sugars has allowed us for the first time to quantify the strength of various nucleobase-dependent anomeric and gauche effects, and how their interplay finally steers the sugar conformation. The plots of the pDdependent thermodynami...

Molecular orbital calculations have been carried out on 2-fluorotetrahydropyran and 2-chlorotetrahydropyran as models for examining the anomeric effect in glycosyl halides. The calculated population of chair conformers depends on the solvent and for the axial form of fluoro derivative decreases from 90.6 % in dioxan to 37.0 % in water. For chloro derivative the dependence is less pronounced; th...

A set of hypotheses is proposed that explains the anomeric specificity of aldopyranose dehydrogenases in terms of an evolutionarily selected function. The first hypothesis, based on stereoelectronic theory, argues that, in the "allowed" transition state for oxidation at the anomeric carbon, the two oxygens attached to the anomeric carbon each bear a lone pair of electrons antiperiplanar to the ...

A natural bonding orbital (NBO) analysis of phosphate bonding and connection to experimental phosphotransfer potential is presented. Density functional calculations with the 6-311++G(d,p) basis set carried out on 10 model phosphoryl compounds verify that the wide variability of experimental standard free energies of hydrolysis (a phosphotransfer potential benchmark) is correlated with the insta...

The conformational and structural properties of the inhalational anesthetic isoflurane (1-chloro-2,2,2-trifluoroethyl difluoromethyl ether) have been probed in a supersonic jet expansion using Fourier-transform microwave (FT-MW) spectroscopy. Two conformers of the isolated molecule were identified from the rotational spectrum of the parent and several (37)Cl and (13)C isotopologues detected in ...

Accurate ab initio calculations including basis set limit (BSL) extrapolations, removal of intramolecular basis set superposition error (BSSE), solvent effect corrections, and thermal effects have been carried out to compare the structure and the anomeric and exo-anomeric effect in 2-methoxytetrahydropyran and 2-methoxythiane. The effect of intramolecular BSSE on the energetics was outlined for...

Sugar phosphates play an important role in metabolism and signaling, but also as constituents of macromolecular structures. Selective phosphorylation of sugars is chemically difficult, particularly at the anomeric center. We report phosphatase-catalyzed diastereoselective "anomeric" phosphorylation of various aldose substrates with α-D-glucose 1-phosphate, derived from phosphorylase-catalyzed c...

The synthesis of S-glycosyl sulfonamides wherein the primary sulfonamide functional group (-SO(2)NH(2)) is directly attached to the anomeric position of a carbohydrate moiety is reported. Our general approach consists of first introducing a thioacetate group at the anomeric center of a per-O-acetylated sugar derivative. From this follows formation of a glycosyl sulfenamide (sugar-SNR(2)), oxida...

Introduction: In base excision repair (BER), " small " oxidative DNA base damage is repaired in a series of steps initiated with a damage specific glycosylase that locates and removes the damaged base leaving a toxic abasic site. A damage general endonuclease (Endo IV or APE1) then binds to the abasic site, introduces a ~67° kink in the DNA and nicks the phosphodiester backbone. Subsequently, D...

The 13C n.m.r. spectrum of Forssman hapten was obtained at 25.16 MHz in [3H] chloroform/[2H] methanol (1:1, v/v), using purified glycosphinogolipid from canine intestinal mucosa (glycolipid I). All amide, olefin, anomeric, intersaccharide glycosidic ether, amide linkage, methyl and many methylene resonances were resolved and assigned. Analysis of the anomeric region reveals the following pentag...