Demonstration of the feasibility of observing nuclear magnetic resonance signals of 77Se covalently attached to proteins

Previous 77Se NMR relaxation time studies established the utility of 77Se NMR spectroscopy in studying low molecular weight (less than 500) selenium-containing molecules. Since the spin rotation and chemical shift anisotrophy mechanisms contributed significantly to the 77Se spin-lattice relaxation in these compounds, it was questionable as to whether the latter mechanism would be efficient enough to enable 77Se resonances to be observed in a reasonable period in high molecular weight selenobiomolecules. Thus, to address this problem, disulfide bonds of ribonuclease-A and lysozyme were reductively cleaved under denaturing conditions, and the resulting 7-8 sulfhydryl groups were treated with a new sulfhydryl group reagent containing selenium, 6,6'-diselenobis(3-nitrobenzoic acid), to give proteins containing covalently attached selenium in the form of selenenyl sulfides. The observation of high resolution 77Se NMR spectra of these proteins under denaturing conditions was accomplished. Five to six 77Se NMR resonances, which fell in a chemical shift range of 14-15 ppm, were observed for each protein and are compared to the chemical shifts of several model selenenyl sulfides derived from cysteine.     

Effect of water stress on some enzymes of nitrogen metabolism in pigeonpea

Water stress created by withholding irrigation at flowering stage (70 days) in pigeonpea resulted in decreased water potential of roots,nodules and leaves. The decreased water potential in nodules resulted in decreased activities of nitrogenase, glutamine synthetase, glutamate dehydrogenase and uricase. However, the activity of allantoinase increased under mild stress with a slight decrease under severe stress. This corresponded with a simultaneous increase in allantoic acid content. Uricase and allantoinase could not be detected in roots and leaves of both control and stressed plants. In roots, the activities of GS and GDH decreased under stress, whereas in leaves, their activities were not affected. Although the water potential recovered in different organs of the stressed plant on re-irrigation, the recovery in the case of some enzymes was not complete.     

Muscle glycolipids in inherited muscular dystrophy of chickens

Gangliosides and neutral glycolipids of muscles from normal and dystrophic chickens were studied. Total glycolipid content of the degenerating muscles was higher than the normal muscles. In addition, the myopathic muscles contained a ganglioside which was absent in the unaffected muscles from normal and dystrophic chickens. Based on the thin-layer chromatographic mobility, treatment with neuraminidases from Vibrio cholerae and Arthrobacter ureafaciens, and reactivity of the asialo-derivative towards anti-ganglio-N-triaosylceramide antibody, the dystrophic-specific ganglioside was tentatively identified as G_M2. Data obtained from young and old dystrophic chickens suggested a direct relationship of this ganglioside to muscular dystrophy.