Galactose isotopically labeled

Topper and Stetten (T2) fed rats on galactose isotopically labeled with Cu on carbon atom 1. They found that the glycogen formed in the liver was isotopically labeled and 70% of the C14 was on C-l of the glucose units. They concluded that galactose could not be split into 2 triose units which would then recombine, but that a Walden-type inversion must occur at C-4. 

G. P. Akulov, N. A. Korsakova, and B. K. Kudelin, Use of kinetic isotope effects in enzymatic oxidation of D-[6-3H]galactose for increasing its molar activity, J. Labelled Comp. Radiopharm., 27 (1989) 803-810. 

Since a wide range of F-18 reactive intermediates is now available, any published synthesis of a fluorocarbohydrate can in principle be adapted to use the radioisotope. The synthesis must be completed within at most an hour or two, which necessitates considerable attention to the rate of each step which occurs after incorporation of the isotope. This incorporation step should be as late in the synthetic scheme as possible. Christman et al. ( ) investigated the influence of several reaction parameters on the synthesis of 6-deoxy 6-fluoro-D-galactose. They used a labeled tetraalkylammonium fluoride solution in acetonitrile to displace a variety of leaving groups in the 6-position of... 

Uniformly labeled D-glucose, D-fructose, and sucrose are prepared by photosynthesis using an appropriate plant and isotopic carbon dioxide 248), Similarly, uniformly labeled D-galactose is obtained by photosynthesis with C 02 and the red alga Irideae laminarioides, where it occurs as a 2-glycerol D-galactopyranoside (65). 

Similar studies designed to measure the turnover of cerebrosides of brain tissue have been carried out by a number of investigators. Davison et al. (1959) employed serine-3-to label brain cerebrosides and computed the turnover rate to be near 200 days. On the other hand Hajra and Rad in (1964) administered acetate-and measured the rate of loss of radioactivity from the fatty acid moieties of the cerebrosides. In the latter experiments the half-time was near 42 days. When the hexose of the cerebrosides is labeled by means of glucose-1- C or galactose-1- C, the rate of depletion of the isotope indicated a half-time of near 40 days (Burton, et al, 19 ). These data indicate that cerebrosides turn over slowly in brain, at a rate near 40 days, as measured by the hexose and fatty acid moieties. The data derived from the serine experiment undoubtedly indicates that the sphingosine pool in brain is small and that this compound is reused in the synthesis of the sphingolipids. 

The large kinetic isotope effect observed in the oxidation of d-[6- H] galactose by galactose oxidase has been exploited to increase its specific activity. As the unlabelled substrate is oxidised faster, incomplete oxidation leaves the starting material enriched in labelled component. In the Bleomycin-mediated oxidative degradation of DNA, 2 -deo qr-4 -pentulose is released. A mechanistic study with 0-labeIled O2 and H2O revealed that the solvent is the source of the 4 -carbonyl oxygen atom. ... 

Fig. 4. Double-label gel profiles of isolated mitochondria obtained during petite induction. Log-phase cultures of 55-R5-3C and 1121 were grown on 2% galactose for 5-6 doublings at 18°C (A), or at 28°C in the presence of 3 mg per ml of chloramphenicol (B), and were labeled with [ H]leucine or [ C]leucine in the presence of 200 Mg per ml cycloheximide. After labeling, mitochondria were isolated and the protein was separated on 10% SDS polyacrylamide gels. After electrophoresis, the gels were sliced and counted. The data are normalized to the total radioactivity recovered from the gels after correction for spillover of the two isotopes. (From Weislogel and Butow. )...

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