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At least 541 records · Page 30Linked to original sources
PubMed1987

D-glucose binding increases secondary structure of human erythrocyte monosaccharide transport protein.

Purified hexose transport protein ("band 4.5") from human erythrocytes, reconstituted in vesicles of its endogenous lipids, displays minima in its circular dichroism (CD) spectrum at 222 and 207 nm, a pattern diagnostic for alpha-helical content of proteins. Upon addition of D-glucose, a saturable increment of +10-12% in negative ellipticity at 222 nm is observed stereospecifically and reproducibly. Addition of L-glucose had no effect on the CD spectrum of the transport protein. Addition of cytochalasin B (CB), a reversible inhibitor of hexose transport, had no effect itself on transporter CD spectra, but restored the spectrum at 222 nm to its original value when added in the presence of D-glucose. The observed D-glucose-induced increase in ordered secondary structure is proposed to result from incorporation into the membrane of a segment of the transport protein originally at a membrane-water interface.

Blood Glucose↗
PubMed1985

1H- and 13C-n.m.r. assignments and conformational analysis of some monosaccharide and oligosaccharide substrate-analogues of lysozyme.

The 1H- and 13C-n.m.r. spectra of solutions of GlcNAc, beta-GlcNAc-(1----4)-GlcNAc, and beta-GlcNAc-(1----4)-beta-GlcNAc-(1----4)-GlcNAc in D2O at 50 degrees are interpreted in terms of the conformations, using a combination of 1D- and 2D-n.m.r. spectroscopy and spectra simulation techniques. Two preferred orientations of the hydroxymethyl group were found for each of these saccharides. The conformations have been compared with those found from X-ray crystallographic data and conformational energy calculations.

Animals↗
PubMed1996

A convenient new pathway for stereospecific epimerization of monosaccharide moieties in disaccharides.

The disaccharides benzyl 4,6-O-benzylidene-2-O-alpha-D-mannopyranosyl-beta- D-glucopyranoside (2), 6-O-beta-D-galactopyranosyl-1,2:3,4-di-O-isopropylidene-alpha-D- galactopyranose (4), and phenyl 4-O-beta-D-galactopyranosyl-1-thio-beta-D-glucopyranoside (7) were selectively acetalated with chloral-dicyclohexylcarbodiimide in a nonclassical pathway. During acetalation, the D-mannopyranosyl moiety of the disaccharide 2 and the unprotected beta-D-galactopyranosyl moieties of 4 and 7 were epimerized at their 3-positions, generating D-altro- and D-gulo-pyranosyl moieties, respectively.

Carbohydrate Conformation↗
PubMed1983

Inhibition by specific monosaccharides of interleukin 2-induced thymocyte proliferation.

When rat thymocytes are cultured for 3 days in serum-free medium and are stimulated to divide by interleukin 2 (IL 2), concanavalin A, or sodium periodate oxidation, addition to the medium of 10-25 mM D-ribose, 2-deoxy-D-ribose, or N-acetyl-D-galactosamine inhibits by 40% or more the incorporation of [3H]thymidine. D-ribose and lectin-free IL 2 generated from sodium periodate oxidation of rat spleen cells were used to study the characteristics of this inhibition and to test possible mechanisms of inhibition. Viability of thymocytes cultured with D-ribose is similar to that of cells cultured without this sugar. In order to be inhibitory, D-ribose has to be added to the cultures within the first 24 hr, and the inhibition can be prevented if the sugar is removed 18-24 hr after the start of culture. D-Ribose does not block the absorption of IL 2 by unstimulated rat thymocytes or by concanavalin A-generated thymic or splenic blast cells. When thymocytes are cultured with D-ribose for 24 hr, inactivated with mitomycin C, and then cultured for 3 days with fresh mitogenically stimulated cells, [3H]thymidine incorporation into the latter is not altered. This suggests that the sugar does not generate suppressor cells or suppressor supernates. D-Ribose does not appear to be a general metabolic inhibitor since [3H]leucine incorporation into thymocyte proteins and the release of [3H]leucine into medium after a 2-hr. [3H]leucine pulse are not altered by D-ribose. Trivial or artifactual effects (nonspecific cytotoxicity, changes in thymidine transport, or changes in isotonicity of the culture medium) cannot explain the inhibition. A hypothetical mechanism of inhibition is discussed.

Animals↗