期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1981
卷号：78
期号：10
页码：5978-5982
DOI：10.1073/pnas.78.10.5978
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Magic-angle single and double cross-polarization 13C and 15N NMR spectra have been obtained of lyophilized soybean cotyledons cultured on media containing, as the only nitrogen source, [4-13C, amide-15N]asparagine. Single cross-polarization NMR shows directly and unambiguously that both labels from asparagine are incorporated extensively and nonrandomly into protein by the developing cotyledon during a 2-week period. A stable-isotope double label tags a chemical bond. The metabolic fate of the asparagine double label was followed by double cross-polarization NMR using the latter's sensitivity to the dipolar coupling between directly bonded 13C and 15N. These experiments show that in culture the direct incorporation of asparagine (with no scrambling of label) accounts for about half of all asparagine residues in soybean protein. This conclusion implies the operation of a regulatory apparatus in soybeans for both direct utilization and degradation of asparagine in protein synthesis.
关键词：double cross-polarization ; 15N NMR ; magic-angle spinning ; stable-isotope chemical bond labeling
