Removal of zero-quantum interference in NOESY spectra of proteins by utilizing the natural inhomogeneity of the radiofrequency field

Summary A single scan method for the suppression of signals arising from zero-quantum coherences (ZQC) is analysed with respect to its application to NMR experiments on proteins. The ZQC are dephased during a spinlock period due to the natural RF inhomogeneity of a commercial probe. A quantitative analysis of a ZQC-compensated NOESY experiment is given. Although the build-up curve for the cross peaks in ZQC-compensated NOESY experiments differ from those in uncompensated experiments, interproton distances in medium-sized proteins can be evaluated with high accuracy. The proposed method is compared with other techniques for ZQC suppression.     

Nitrogen catabolite repression in a glutamate auxotroph of Saccharomyces cerevisiae

The biosynthesis of asparaginase II in Saccharomyces cerevisiae is subject to nitrogen catabolite repression. In the present study we examined the physiological effects of glutamate auxotrophy on cellular metabolism and on the nitrogen catabolite repression of asparaginase II. Glutamate auxotrophic cells, incubated without a glutamate supplement, had a diminished internal pool of alpha-ketoglutarate and a concomitant inability to equilibrate ammonium ion with alpha-amino nitrogen. In the glutamate auxotroph, asparaginase II biosynthesis exhibited a decreased sensitivity to nitrogen catabolite repression by ammonium ion but normal sensitivity to nitrogen catabolite repression by all amino acids tested.     

Role of vitamin E in the etiology of spontaneous hemorrhagic necrosis of the central nervous system of fetal hamsters

The intraperitoneal inoculation of pregnant hamsters with vitamin E during the first half of gestation reduced the severity or eliminated the occurrence of grossly observable effects of spontaneous hemorrhagic necrosis (SHN) of the central nervous system in their offspring and improved the pre-weaning viability of their litters. The addition of corn oil (16%) or linoleic acid (8%) to a ration associated with the occurrence of SHN in fetal hamsters enhanced the incidence and severity of the disease, and these effects were moderated by inoculation of the dams with vitamin E. Experimental data indicated that, among multifactorial contributions to the cause of SHN in hamsters, vitamin E availability and levels of dietary polyunsaturated fatty acid played a significant and interrelated role.