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：1971
卷号：68
期号：12
页码：3180-3184
DOI：10.1073/pnas.68.12.3180
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：X-ray diffraction techniques have been used to investigate the physical state of the lipids in the membrane of an unsaturated fatty acid auxotroph of Escherichia coli. Thermotropic phase transitions have been detected in membranes prepared from cells grown on various fatty acid supplements. Below the transition temperature, the X-ray diffraction pattern features a sharp ring at 420 pm (4.2 A) due to the close hexagonal packing of the apolar groups of the lipids; above the transition temperature the lipids are in a less organized liquid-crystalline state that gives rise to a diffuse band centered at a Bragg spacing of 460 pm (4.6 A). This transition occurs at or below the temperature at which the cells were grown. Disparities between this transition temperature and the temperature of discontinuities in the Arrhenius plots for proline transport and succinic dehydrogenase activity lead us to conclude that the distribution of lipids within the membrane is heterogeneous.
