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：11
页码：6878-6882
DOI：10.1073/pnas.78.11.6878
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Cosonicated mixtures of egg phosphatidylcholine and small amounts (less than 5% wt/wt) of triolein have been studied by 13C NMR spectroscopy. The 50.3-MHz 13C NMR spectrum of vesicles preparations containing 90% isotopically substituted [1-13C]triolein showed two carbonyl resonances at chemical shift values that indicate hydrogen bonding of H2O molecules with the carbonyl groups. The extent of hydration, estimated from the chemical shift values that indicate hydrogen bonding of H2O molecules with the chemical shift values (173.07 ppm and 172.39 is approximately 50%. The data suggest that the triolein is located in the bilayer with the three carbonyl groups at the aqueous interface. The acyl chains are extended toward the bilayer interior, with a conformation of the glyceryl region such that the primary (alpha) carbonyls are closer to the aqueous medium than is the secondary (beta) carbonyl. Thus, triolein is present in the bilayer in an orientation appropriate for enzymatic hydrolysis, with the second substrate (H2O) in close proximity to the hydrolytic site, and with a conformation that could explain, in part, enzymatic specificity for hydrolysis at the alpha position. Spectra of vesicles containing greater than or equal to 3% triolein showed two additional carbonyl peaks characteristic of pure (neat) triolein. This allowed a determination of the maximum solubility (approximately 2.8%) of surface-oriented triolein in the bilayer phase. Beyond this limit all excess triolein partitions into a separate oil phase.
