Department of Chemistry, University of Warsaw, Warsaw, Poland.
Chirality. 2011 Sep;23(8):638-46. doi: 10.1002/chir.20996. Epub 2011 Jul 22.
Hydrodynamic forces are capable of inducing structural order in dispersed solid phases, and of causing symmetry-breaking when chiral crystals precipitate from an achiral liquid phase. Until it was observed upon vortex-assisted fibrillation of insulin, such behavior had been thought to be confined to few unbiological systems. In this paper we are discussing chiroptical properties of two chiral variants of insulin amyloid, termed +ICD and -ICD, which form during the process of chiral bifurcation in vortexed solutions of aggregating insulin. As conventional measurements of circular dichroism of solid, anisotropic substances are particularly vulnerable to overlapping influences of linear birefringence and linear dichroism, we have employed complementary tools including dedicated universal chiroptical spectrophotometer to rule out such artifacts. We propose that the strong chiroptical properties of +ICD and -ICD insulin fibrils are an aspect of genuine superstructural chirality of amyloid fibrils and of powerful excitonic couplings taking place within them. A comparison of thioflavin T complexes with fibrils formed by insulin and polyglutamic acid suggests that the extrinsic Cotton effect stemming from the level of single twisted dye molecules is weaker, although diagnostically useful, and cannot account for the overall magnitude of ICD of the dye bound to ±ICD insulin amyloid.
水动力能够在分散的固相中诱导结构有序，并在手性晶体从非手性液相沉淀时引起对称破缺。直到在涡旋辅助胰岛素纤维状化过程中观察到这种行为之前，人们一直认为这种行为仅限于少数非生物体系。在本文中，我们讨论了在涡旋聚集胰岛素溶液中手性分岔过程中形成的两种胰岛素淀粉样变变体（称为+ICD 和-ICD）的手性光学性质。由于对固体各向异性物质的圆二色性的常规测量特别容易受到线性双折射和线二色性的重叠影响，我们采用了互补的工具，包括专用的通用手性分光光度计，以排除这种假象。我们提出，+ICD 和-ICD 胰岛素原纤维的强手性光学性质是淀粉样原纤维真正超结构手性的一个方面，也是其中发生的强大激子耦合的一个方面。与由胰岛素和聚谷氨酸形成的原纤维的硫黄素 T 复合物的比较表明，尽管具有诊断意义，但源于单个扭曲染料分子水平的外在科顿效应较弱，并且不能说明结合到±ICD 胰岛素淀粉样蛋白的染料的 ICD 的整体幅度。
