Blasie J K
Biophys J. 1972 Feb;12(2):191-204. doi: 10.1016/S0006-3495(72)86079-X.
The location of the photopigment molecules relative to the lipid hydrocarbon core of retinal receptor disk membranes was unknown. The photopigment molecules could occur entirely on the surface of the membrane, completely embedded in its hydrocarbon core, or at some intermediate location protruding into both the aqueous surface layer and the lipid core of the disk membrane. To resolve this uncertainty, we collected X-ray intensity data diffracted by the photopigment molecules in wet pellets of oriented frog retinal receptor disk membranes as a function of the electron density of the sedimentation medium. These data were fitted to a model which predicted the integrated intensity diffracted from the photopigment molecules as a function of the electron density of the sedimentation medium and the extent to which the molecule protruded into the aqueous surface layer and the lipid core of the disk membrane. This analysis showed that for the photopigment molecular diameter of approximately 42 A, about 28 A protrudes into the aqueous layer, and about 14 A into the lipid core for unbleached photopigment. Bleaching causes the photopigment to "sink" into the lipid core some 7 A. The partial embedding of the photopigment molecules in the lipid core introduces a correlation of the photopigment molecules with lipid hydrocarbon chains in the plane of the disk membranes.
视色素分子相对于视网膜受体盘膜的脂质烃核心的位置尚不清楚。视色素分子可能完全位于膜的表面，完全嵌入其烃核心，或者处于某个中间位置，突出到盘膜的水表面层和脂质核心中。为了解决这一不确定性，我们收集了定向青蛙视网膜受体盘膜湿颗粒中视色素分子衍射的X射线强度数据，作为沉降介质电子密度的函数。这些数据被拟合到一个模型中，该模型预测了视色素分子衍射的积分强度，作为沉降介质电子密度以及分子突出到盘膜水表面层和脂质核心程度的函数。该分析表明，对于直径约为42埃的视色素分子，未漂白的视色素约有28埃突出到水层中，约14埃突出到脂质核心中。漂白会使视色素“沉入”脂质核心约7埃。视色素分子在脂质核心中的部分嵌入导致视色素分子与盘膜平面中的脂质烃链相关。
