Department of Sciences and Informatics, Muroran Institute of Technology, Mizumoto-cho 27-1, Muroran, Hokkaido050-8585, Japan.
J Phys Chem A. 2023 Feb 16;127(6):1436-1444. doi: 10.1021/acs.jpca.2c07794. Epub 2023 Feb 5.
Thioflavin T (ThT) is a typical fluorescent marker for detecting the formation of amyloid fibrils, because its fluorescence intensity increases by more than 2 orders of magnitude upon complexation with the fibrils. Strong electrostatic fields on protein surfaces are known to be a significant factor in chemical reactions and biological functions. Therefore, ThT bound to amyloid fibrils must experience strong electric fields. This study employed electroabsorption and Stark fluorescence spectroscopies to clarify the effects of external electric fields on the photophysics of ThT. The absorption spectrum shows two bands ascribed to locally excited (LE) and charge transfer (CT) states. Coupling between the LE and CT states is enhanced in the presence of an external electric field, resulting in fluorescence quenching. The electric field strength of the amyloid fibril surface was inferred from the fluorescence quenching efficiency of ThT.
硫黄素 T（ThT）是一种典型的用于检测淀粉样纤维形成的荧光标记物，因为它与纤维复合时荧光强度增加了两个数量级以上。已知蛋白质表面的强静电场是化学反应和生物功能的重要因素。因此，与淀粉样纤维结合的 ThT 必须经历强电场。本研究采用电吸收和 Stark 荧光光谱法来阐明外电场对 ThT 光物理性质的影响。吸收光谱显示两个带归因于局域激发（LE）和电荷转移（CT）态。在外电场存在下，LE 和 CT 态之间的耦合增强，导致荧光猝灭。从 ThT 的荧光猝灭效率推断出淀粉样纤维表面的电场强度。
