Viguera A R, González-Mañas J M, Taneva S, Goñi F M
Department of Biochemistry, University of the Basque Country, Bilbao, Spain.
Biochim Biophys Acta. 1994 Nov 23;1196(1):76-80. doi: 10.1016/0005-2736(94)90297-6.
The purpose of this paper is to explore the reasons by which purple membrane solubilization by detergents takes hours, or even days, to reach equilibrium, while most biomembranes are solubilized in a matter of seconds, or minutes. With that aim, changes in the purple membrane absorption spectrum produced by hydrogenated Triton X-100 under equilibrium conditions (24 h) have been compared to those caused by the same surfactant in the minute, second and sub-second time scale. It is found that the various processes that accompany, or lead to, solubilization are already detected, and even reach an apparent equilibrium, in the 10 s that follow detergent addition. No new phenomena are detected in the following minutes, or hours, that are relevant to the process under study. This leads to the conclusion that the long solubilization process consists of the repeated operation of simple phenomena that are relatively fast in themselves. A hypothesis is proposed according to which the tight crystalline organization of the purple membrane prevents the insertion of detergent monomers in the lipid bilayer; instead, the surfactant would bind the periphery of the patches, i.e., the hydrocarbon-water contact region, and solubilization would take place gradually, from the periphery towards the core of the membrane patches, at a progressively lower rate as the amounts of free detergent and detergent-binding sites are decreased by the previous solubilization steps.
本文的目的是探究为何去污剂使紫膜溶解达到平衡需要数小时甚至数天，而大多数生物膜在数秒或数分钟内就能溶解。为实现该目标，将平衡条件下（24小时）氢化 Triton X - 100 引起的紫膜吸收光谱变化，与相同表面活性剂在分钟、秒和亚秒时间尺度上引起的变化进行了比较。结果发现，在添加去污剂后的10秒内，伴随或导致溶解的各种过程就已被检测到，甚至达到了明显的平衡。在接下来的数分钟或数小时内，未检测到与所研究过程相关的新现象。由此得出结论，漫长的溶解过程是由本身相对较快的简单现象的重复操作组成的。提出了一个假设，即紫膜紧密的晶体结构阻止了去污剂单体插入脂质双层；相反，表面活性剂会结合膜片的周边，即碳氢化合物 - 水接触区域，并且溶解将从周边向膜片核心逐渐发生，随着先前溶解步骤使游离去污剂和去污剂结合位点的量减少，溶解速率会逐渐降低。
