The transverse location of the retinal chromophore in the purple membrane by diffusion-enhanced energy transfer.
The transverse location of the retinal chromophore in the purple membrane by diffusion-enhanced energy transfer.
复制标题
通过扩散增强的能量转移，视网膜发色团在紫色膜中的横向位置。
DOI：
10.1016/0022-2836(89)90600-1
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发表时间：
1989
影响因子：
5.6
通讯作者：
Thomas,DD
中科院分区：
文献类型：
--
作者：
Leder,RO;Helgerson,SL;Thomas,DD
我们利用快速扩散限（RDL）内的荧光能量转移来估计紫膜（PM）中视网膜的跨膜深度。Tb（III）的螯合物是PM的视网膜发色团的优良能量供体，具有约62 μ π ι的Förster能量转移的最大Rovalue（假设供体量子产率为1）。能量转移速率从时间分辨的发射动力学的供体进行测量。根据PM片或膜囊泡的几何模型，通过模拟RDL能量传递速率常数来估计螯合物和发色团之间的最接近距离。Tb（III）HED 3A与网膜之间的RDL能量传递的表观速率常数为1.5（± 0.1）× 106 m-1 s-1，相当于网膜发色团的深度约为10±2 μ m.根据RDL能量传递速率常数，估计PM囊外表面至视网膜的深度为10 ± 3 μ m。推导出这种安排的速率常数太低，是一致的最短的视网膜深度推断PM片。因此，CEV的囊内面，对应于细胞的细胞质面，是离细菌视紫红质的发色团更远的表面。
We have used fluorescence energy transfer in the rapid-diffusion limit (RDL) to estimate the trans-membrane depth of retinal in the purple membrane (PM). Chelates of Tb(III) are excellent energy donors for the retinal chromophore of PM, having a maximumRovalue for Förster energy transfer of approximately 62 Å (assuming a donor quantum yield of 1). Energy transfer rates were measured from the time-resolved emission kinetics of the donor. The distance of closest approach between chelates and the chromophore was estimated by simulating RDL energy-transfer rate constants according to geometric models of either PM sheets or membrane vesicles. The apparent rate constant for RDL energy transfer between Tb(III)HED3A and retinal in PM sheets is 1·5(±0·1) × 106m−1s−1, corresponding to a depth of approximately 10±2 Å for the retinal chromophore.Cell envelope vesicles (CEVs) fromHalobacterium halobiumwere studied by using RDL energy transfer to assess the proximity of retinal to either the extracellular or intracellular face of the PM. The estimated depth of retinal from the extravesicular face of the PM is 10 ± 3 Å, based on the RDL energy-transfer rate constant.Energy-transfer levels to retinal in the PM were estimated by an indirect method with energy donors trapped in the innerr-aqueous space of CEVs. The rate constants derived for this arrangement are too low to be consistent with the shortest depth of retinal deduced for PM sheets. Thus, the intravescicular face of CEVs, corresponding to the cytoplasmic face of cells, is the more distant surface from the chromophore of bacteriorhodopsin.