期刊
JOURNAL OF SYNCHROTRON RADIATION
卷 12, 期 -, 页码 598-607出版社
INT UNION CRYSTALLOGRAPHY
DOI: 10.1107/S0909049505019850
关键词
amino acid; hydrogen bonding; high-pressure single-crystal diffraction
The crystal structure of hexagonal L-cystine has been determined at room temperature at pressures between 0.4 and 3.7 GPa; unit-cell dimensions were measured up to 6.4 GPa. The structure of this phase consists of molecules in their zwitterionic form, and crystallizes in the hexagonal space group P6(1)22. The structure consists of hydrogen-bonded layers which are strongly reminiscent of those seen in alpha-glycine, and consist of R-4(4)(16) hydrogen-bonded ring motifs. These layers are connected on one side by the disulfide bridges within the cystine molecules, and on the other by NH center dot center dot center dot O hydrogen bonds to other glycine-like layers. The most compressible unit-cell dimension, and the direction of greatest strain in the structure, is along the c-axis, and application of pressure pushes the layers closer together. The compression occurs approximately equally in the regions of the interlayer hydrogen bonds and the disulfide bridges; in the latter, changes in the C - S - S - C torsion angles allow the cystine molecules to act like springs. The effects of pressure can be interpreted in terms of closing-up of voids in the structure, and this leads to (i) a lessening of the N-C - C - O and C - S - S - C torsional angles, (ii) shortening of the N - H center dot center dot center dot O hydrogen bonds by 0.10 - 0.60 angstrom and (iii) a further shortening of an already short S center dot center dot center dot S contact from 3.444 (4) angstrom to 3.264 (4) angstrom.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据