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：1972
卷号：69
期号：3
页码：590-593
DOI：10.1073/pnas.69.3.590
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：We have used Fourier transform nuclear magnetic resonance methods to measure the spin-lattice and transverse relaxation times at 220 MHz of the choline N-methyl and the fatty-acid [α]-carbonyl, allyl, vinyl, methylene, and methyl protons of sonicated egg-yolk lecithin. Over the temperature range investigated the T1 values were, in general, similar to, but different from, one another, suggesting that the relaxation rates of all of the fatty-acid protons are not determined solely by spin-diffusion to a heat sink. Arrhenius plots of the T1 data gave activation energies similar to those for the barriers to internal rotation in alkanes. The values of the transverse relaxation rate, T2, showed a relatively large variation among the proton resonances; about 20% of the methylene protons had a T2 of 56 msec, while the remaining protons relaxed according to a distribution of values all shorter than 20 msec. Such a distribution of relaxation times is envisioned to arise from a distribution of correlation times stemming from complex motions in which extended angular excursions of the fatty acid chain are coupled to trans[->]gauche conformational transitions.
