Kitts Catherine C, Vanden Bout David A
Department of Chemistry and Biochemistry, Center for Nano and Molecular Science and Technology, and Texas Materials Institute, University of Texas at Austin, Austin, Texas 78712, USA.
J Phys Chem B. 2009 Sep 3;113(35):12090-5. doi: 10.1021/jp903509u.
The binding of two amyloid fibril stain dyes, thioflavin T (ThT) and its neutral analog 2-[4'-(dimethylamino)phenyl]-benzothiazole (BTA-2), are measured using near-field scanning optical microscopy (NSOM), which is able to image individual amyloid fibrils. Polarized NSOM images reveal that both dyes bind to the fibrils with the long axis of the molecule aligned parallel to the long axis of the fibrils. This indicates that the dyes bind along the surface of the beta-sheet within the grooves of the fibril that run parallel to the fibril axis. The similarity in the binding motifs of the two dyes shows that electrostatic interaction of the charged amine group on the ThT dye plays a minimal role in the affinity of the dyes for the amyloids. The polarized NSOM images confirm that the enhanced fluorescence of the ThT and BTA-2 result from binding of the monomeric dye rather than micelles or excimer species.
使用能够对单个淀粉样纤维进行成像的近场扫描光学显微镜（NSOM），测量了两种淀粉样纤维染色染料硫黄素T（ThT）及其中性类似物2-[4'-(二甲氨基)苯基]-苯并噻唑（BTA-2）的结合情况。偏振NSOM图像显示，两种染料均以分子的长轴与纤维的长轴平行的方式结合到纤维上。这表明染料沿着与纤维轴平行的纤维凹槽内的β-折叠表面结合。两种染料结合模式的相似性表明，ThT染料上带电荷的胺基团的静电相互作用在染料与淀粉样蛋白的亲和力中起最小作用。偏振NSOM图像证实，ThT和BTA-2增强的荧光是由单体染料的结合而非胶束或准分子物种引起的。
