自旋标记法研究不同因素对嗜盐菌紫膜类脂物性的影响

EFFECT OF PHYSICAL CHARACTER OF SOME FACTORS ON PURPLE MEMBRANE LIPID OF HALOBACTERIUM HALOBIUM——SPIN LABEL STUDY

本文用自旋标记方法研究了不同的pH和盐介质对光照前后嗜盐菌(H.halobium)紫膜类脂的影响.在低盐介质中,紫膜类脂序参数S的大小依次为pH2.5>pH7.0>pH12.0:旋转相关时间τ均在10^(-a)sec范围之内.pH12.0的暗适应和光适应悬液的ESR波谱十分相似,其它的ESR波谱均为暗适应>光适应.悬浮于Triton X-100中的紫膜的序参数最小,τ_e值在10^(-9)--10^(-10)sec之间;但其暗适应和光适应的ESR波谱仍有差别.在高盐介质中,紫膜类脂序参数均大于低盐介质,结构最为刚硬.实验表明类脂的序态变化与bR分子的构象改变有密切关系.

Spin labeling was used to probe for changes in lipid environments before and after illumination of the purple membrane (PM) of H. halobium at different pH and Salt medium. In dilute salt medium the difference of order parameter (S) of PM lipid is pH2.5>pH7.0>pH12.0. The rotational correlation time (τc) was given within the limits of 10-8sec. The ESR spectrum of a light adapted and a dark adapted suspension of pH12.0 is very much alike, and the other ESR spectra (pH2.5 and pH7.0) are dark adapted > light adapted. The S of PM suspension in Triton X-100 is smallest than others, and its τc value is between 10-9 sec and 10-10 sec, but its ESR spestra of dark adapted and light adapted are different from each other. In high salt medium the S of PM lipid is higher than dilute salt medium, and its structure is extremely rigid. The result indicates that a change in lipid order degree is closely related with the changes in bR molecular conformation.