Kumar V V, Baumann W J
Hormel Institute, University of Minnesota, Austin 55912.
Biophys J. 1991 Jan;59(1):103-7. doi: 10.1016/S0006-3495(91)82202-0.
Lysophosphatidylcholine (lysoPC) monomers or micelles in water give rise to a narrow, isotropic phosphorus-31 NMR signal (40.6 ppm; v1/2 1.7 Hz; 32.2 MHz). Upon addition of praseodymium ions, the phosphorus signals are shifted downfield. However, the downfield shifts for the longer-chain lysophosphatidylcholines, which exist in the aggregated state, are far greater than those for the shorter-chain homologues, which exist as monomers. At a Pr3+/lysoPC molar ratio of 0.5, the signals of C12lysoPC through C18lysoPC were shifted by 12.1 ppm, whereas the signals of C6lysoPC and C8lysoPC were shifted by only 2.26 ppm. This very pronounced difference in lanthanide-induced downfield shifts between micelles and monomers can be utilized to determine with accuracy lysoPC critical micelle concentrations (CMC) from downfield shift-vs.-concentration plots. The CMC values we determined were 57 mM for C8lysoPC, 5.7 mM for C10lysoPC, and 0.6 mM for C12lysoPC. The shift reagent phosphorus-31 nuclear magnetic resonance technique particularly lends itself to the measurement of CMC values in the millimolar and high micromolar range. The method can equally be used for measuring critical micelle concentrations of short-chain phosphatidylcholines.
水中的溶血磷脂酰胆碱（lysoPC）单体或胶束会产生一个狭窄的、各向同性的磷-31核磁共振信号（40.6 ppm；半高宽1.7 Hz；32.2 MHz）。加入镨离子后，磷信号会向低场移动。然而，以聚集态存在的长链溶血磷脂酰胆碱的低场位移远大于以单体形式存在的短链同系物的低场位移。在Pr3+/lysoPC摩尔比为0.5时，C12lysoPC至C18lysoPC的信号位移了12.1 ppm，而C6lysoPC和C8lysoPC的信号仅位移了2.26 ppm。胶束和单体之间镧系元素诱导的低场位移的这种非常显著的差异可用于从低场位移-浓度图中准确测定lysoPC的临界胶束浓度（CMC）。我们测定的CMC值对于C8lysoPC为57 mM，对于C10lysoPC为5.7 mM，对于C12lysoPC为0.6 mM。位移试剂磷-31核磁共振技术特别适用于测量毫摩尔和高微摩尔范围内的CMC值。该方法同样可用于测量短链磷脂酰胆碱的临界胶束浓度。
