Koenig S H, Brown R D, Kurland R, Ohki S
IBM T. J. Watson Research Center, Yorktown Heights, New York 10598.
Magn Reson Med. 1988 Jun;7(2):133-42. doi: 10.1002/mrm.1910070202.
We report the magnetic field dependence (NMRD profiles) of 1/T1 of solvent protons in solutions of unilamellar phosphatidylserine vesicles with added Mn2+ ions, including studies of the variation of the profiles with temperature, extent of coverage of available binding sites by Mn2+ ions, ionic strength, and competition with (nonparamagnetic) Ca2+ ions. ions. In addition, we sketch the theory of screening of the negative surface charges of the vesicles due to both specific binding of Mn2+ ions and nonspecific effects of other mobile solute ions. The major result is that the NMRD profiles, although qualitatively similar, vary systematically as the parameters of the solutions are altered, in a manner consistent with the theory of screening. The profiles of the Mn2+-vesicle complexes are much like those of Mn2+-protein complexes that have the ions in an octahedral ligand environment. In addition, we find that the profiles are similar to those reported for Mn2+ ions in packed liver cells and liver tissue, supporting a previous conjecture that available Mn2+ in liver binds to the polar head groups of cell membranes, saturating these sites before binding elsewhere. Again, it is evident that results for in vitro model systems can be extrapolated reliably to tissue behavior.
我们报告了添加Mn2+离子的单层磷脂酰丝氨酸囊泡溶液中溶剂质子1/T1的磁场依赖性（NMRD谱），包括研究谱随温度、Mn2+离子对可用结合位点的覆盖程度、离子强度以及与（顺磁性）Ca2+离子竞争的变化。此外，我们概述了由于Mn2+离子的特异性结合和其他可移动溶质离子的非特异性效应而对囊泡负表面电荷进行屏蔽的理论。主要结果是，尽管NMRD谱在定性上相似，但随着溶液参数的改变，它们会系统地变化，其方式与屏蔽理论一致。Mn2+ - 囊泡复合物的谱与Mn2+ - 蛋白质复合物的谱非常相似，后者中的离子处于八面体配体环境中。此外，我们发现这些谱与报道的在密集肝细胞和肝组织中的Mn2+离子的谱相似，支持了之前的一个推测，即肝脏中可用的Mn2+与细胞膜的极性头部基团结合，在结合到其他地方之前先使这些位点饱和。同样明显的是，体外模型系统的结果可以可靠地外推到组织行为。
