Isotopes sugars

The other example presented of a non-scrambled distribution of isotopes involves the synthesis of collagen. For a mature animal at steady state, we might expect extensive atomic scrambling in the sense that most of the non-essential amino acid content of this protein (78% of its carbon atoms) can be synthesized from the general pool of glycogenic substrates that arise from metabolism of all sugars and fats, although the pathway from fats is restricted... 

White, J. W. (1992). Internal standard stable carbon isotope ratio method for determination of C-4 plant sugars in honey Collaborative trial study, and evaluation of improved protein preparation procedure. J. Assoc. Ojfic. Anal. Chem. 75,543-548. 

The well-known acid-catalyzed conversion of sugars into furan derivatives obviously consists of a complex sequence of reactions, and the industrial heterophasic conversion of pentosans in plant tissues has been discussed in detail.11 The reactions themselves are still not well understood, although xylose and glucuronic acid in deuterium oxide afford 2-furaldehyde without uptake of isotope thus limiting the mechanistic possibilities to those not permitting reversible enolization.12 The bacterial sugar streptose yields... 

In addition to the foregoing examples, periodate oxidation has been applied to isotopically labeled sugars (for the determination of label distribution), 226 -226 to certain branched-chain sugars,227-229 and to some nitrogenous derivatives of the simple sugars.230-236... 

The employment of NMR-active isotopes permits to access experimental parameters which are intrinsically difficult to measure, unless a significant concentration of the sugar is present in the NMR tube. For instance, aqueous solutions of N-acetyIncuraminic acid, labeled with 13C at Cl, C2, and/or C3, were analyzed to detect and quantify the various chemical species present in equilibrium at different pHs. In fact, in addition to the expected a and (3 pyranose forms, acyclic keto, keto hydrate and enol forms were identified on the basis of 13C NMR spectroscopic data. Besides, DFT methods were employed to predict the effect of enol and hydrate structure on the coupling constant values Jc,u and /c c involving C2 and C3, finding that 2/c2,h3 can be safely used to differentiate the cis and tram isomers of the enol forms.9... 

Reduction of aldonolactones and their derivatives with isotopically modified reducing agents leads to sugars labeled at the anomeric center. Glycosides substituted with deuterium or labeled with tritium are widely employed for kinetic isotope-effect measurements, mechanistic studies, isotope-tracing experiments, and so on. 

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