Sugar, oxidation rate constants

MoFe proteins and, 47 174 oxidation rate constants, 43 156-157 sugar functionality, 43 152 Nuclides, shielded, 2 353-354... 

Rates of Enolization Reactions. For a better understanding of the transformation and oxidation reactions of reducing sugars, methods have been developed to measure the primary rates of enolization (18). One of these methods depends on the rate at which tritium ions are released from aldoses-2- to the solvent. This is measured by separation of the water-, sublimation, and radiochemical assay of the water as the reaction proceeds. The rate constant is calculated from the first-order equation ... 

Rate constant for the oxidation of aldoses k) divided by that of a-D-gluoopy-ranose (k = 32 X 10 min ). The numbers represent the position on which the substituent is axial. In the terminology suggested by Reeves, normal chair conformation is denoted by Cl for n sugars and IC for their enantiomorphs. " The value has been calculated from the rate of oxidation of an equilibrated solution of the aldose. 

Rate Constants for the Ozone Oxidation of Various Aromatic Compounds and Comparison with Simple Sugars... 

Rate Constants for Oxidation of Sugars and Nucleotides by Oxoruthenium(IV) and Diplatinum(II)... 

The rate constants for oxidation of model mononucleotides and sugars are set out in Table I. The rate constants were measured under... 

The kinetic studies also argue strongly for 1 oxidation. First, all of the nucleotides are more reactive than deoxyribose and ribose. This result can be ascribed to more effective activation of the 1 position by the nucleic acid base compared to hydroxyl, which is likely to be less electron-donating. This trend is evident even after correction of rate constants for the electrostatic binding preequilibrium. In fact, this same trend is evident in the Pt2(pop)4 rate constants. Since Pt2(pop)4 is a tetraanion, the reactions of nucleotides are actually discouraged electrostatically relative to those of the neutral sugars—yet nucleotides are more reactive by about an order of magnitude in rate constant. 

Hen egg-white lysozyme (0.125 mAf) was incubated at 37° in water (pH 5.5) with (GlcNAc) 2-Ep (1.0 mAf), and aliquots were taken at various times to determine the residual activity of the enzyme at pH 6.7 and 26° using cells of M. lutetos as substrate. The inactivation was exponential with time, and the enzyme lost 50% of its initial activity in 3 hr under the experimental conditions used. The rate of inactivation was markedly decreased when (GlcNAc)2 (41 mAf) was added to the incubation mixture. In the absence of (GlcNAc)2-Ep and under the same incubation conditions, the enzymic activity remained constant. Incubation of the enzyme with an epoxide without the sugar moiety, such as propylene oxide (up to 0.5 M), did not affect its activity. ... 

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