Lanio M E, Alvarez C, Pazos F, Martinez D, Martínez Y, Casallanovo F, Abuin E, Schreier S, Lissi E
Faculty of Biology, University of Habana, La Habana, Cuba.
Toxicon. 2003 Jan;41(1):65-70. doi: 10.1016/s0041-0101(02)00210-6.
The effect of sodium dodecyl sulfate (SDS) upon the conformation and hemolytic activity of St I and St II strongly depends on its concentration. At relatively low surfactant concentrations (ca. 0.5-5mM range) the surfactant leads to the formation of aggregates, as suggested by the turbidity observed even at relatively low (micromolar range) protein concentrations. In this surfactant range, the proteins show an increase in intrinsic fluorescence intensity and reduced quenching by acrylamide, with an almost total loss of its hemolytic activity. At higher surfactant concentrations the protein adducts disaggregates. This produces a decrease in fluorescence intensity, increase in quenching efficiency by acrylamide, loss of the native tertiary conformation (as reported by the near UV-CD spectra), and increase in alpha-helix content (as evidenced by the far UV-CD spectra). However, and in spite of these substantial changes, the toxins partially recover their hemolytic activity. The reasons for this recovering of the activity at high surfactant concentrations is discussed.
十二烷基硫酸钠（SDS）对St I和St II的构象及溶血活性的影响很大程度上取决于其浓度。在相对较低的表面活性剂浓度（约0.5 - 5mM范围）下，即使在相对较低（微摩尔范围）的蛋白质浓度时观察到的浊度表明，表面活性剂会导致聚集体的形成。在这个表面活性剂浓度范围内，蛋白质的固有荧光强度增加，丙烯酰胺淬灭作用减弱，且其溶血活性几乎完全丧失。在较高的表面活性剂浓度下，蛋白质加合物会解聚。这导致荧光强度降低，丙烯酰胺淬灭效率增加，天然三级构象丧失（如近紫外圆二色光谱所报道），α - 螺旋含量增加（如远紫外圆二色光谱所证明）。然而，尽管发生了这些显著变化，毒素仍部分恢复了其溶血活性。本文讨论了在高表面活性剂浓度下活性恢复的原因。
