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：1980
卷号：77
期号：12
页码：6965-6967
DOI：10.1073/pnas.77.12.6965
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：A recently determined x-ray structure of the hydrated gramicidin S-urea complex is compared with a structure predicted by conformational energy minimization. It is shown that the two structures are in good general agreement, including the prediction of a hydrogen bond between the side-chain amino group of ornithine and the backbone carbonyl of phenylalanine. This agreement demonstrates the power of empirical potential energy methods in conformational analysis and illustrates one method for solution of the multiple-minimum problem for small peptides. It is noted that, in the crystal, gramicidin S is a dimer that forms an intermolecular antiparallel four-stranded {beta} sheet and that differences between the predicted and x-ray structures can be explained by this intermolecular interaction. The residual conformational asymmetry of the x-ray structure is shown to be due to the formation of the complex with urea.
