N.M. Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Kosygin St. 4, Moscow 119334, Russia.
N.M. Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Kosygin St. 4, Moscow 119334, Russia.
Spectrochim Acta A Mol Biomol Spectrosc. 2019 Jun 5;216:190-201. doi: 10.1016/j.saa.2019.03.017. Epub 2019 Mar 14.
Spectral-fluorescent properties of polymethine dye probes anionic 3,3'-di(sulfopropyl)-4,5,4',5'-dibenzo-9-ethylthiacarbocyanine-betaine (DEC) and cationic 3,3',9-trimethylthiacarbocyanine iodide (Cyan 2) in the presence of biological surfactants, bile salts sodium cholate (NaC), sodium deoxycholate (NaDC) and sodium taurocholate (NaTC), as well as sodium dodecyl sulfate (SDS), have been studied in a wide range of surfactant concentrations. When a surfactant is introduced into a solution of DEC, changes of the spectral-fluorescent properties are observed due to decomposition of dye dimers into cis-monomers and cis-trans conversion of the resulting monomers. In the presence of SDS, both processes occur in parallel, caused by noncovalent interaction of dye monomers with micelles, and mainly occur near the critical micelle concentration (CMC). In contrast, upon the introduction of increasing concentrations of bile salts, decomposition of dye dimers into the monomers begins at lower concentrations than cis-trans conversion. The former process is almost completed at concentrations close to CMC of secondary micelles (CMC2), while the latter process occurs even at concentrations of bile salts much higher than CMC2. Hence, DEC can serve as a probe that permits estimating the value of CMC2 and is indicative of reorganization of secondary micelles upon an increase in bile salt concentration. Aggregation of DEC and Cyan 2 on bile salts is also observed. Since it is observed at relatively low concentrations of bile salts (<CMC2), the aggregation probably occurs on monomeric molecules of bile salts and their small associates and primary micelles. Decomposition of the aggregates formed begins at concentrations of bile salts above CMC2 (that is, upon the interaction with secondary micelles).
聚甲川染料探针阴离子 3,3'-二（磺丙基）-4,5,4',5'-二苯并-9-乙基噻嗪碳菁甜菜碱（DEC）和阳离子 3,3',9-三甲基噻嗪碳菁碘化物（Cyan 2）在生物表面活性剂、胆汁盐（NaC）、脱氧胆酸钠（NaDC）和牛磺胆酸钠（NaTC）以及十二烷基硫酸钠（SDS）存在下的光谱荧光性质已在广泛的表面活性剂浓度范围内进行了研究。当表面活性剂被引入 DEC 的溶液中时，由于染料二聚体分解为顺式单体和顺式-反式转化，观察到光谱荧光性质的变化。在 SDS 的存在下，两种过程都同时发生，这是由于染料单体与胶束的非共价相互作用引起的，并且主要发生在临界胶束浓度（CMC）附近。相比之下，随着胆汁盐浓度的增加，染料二聚体分解为单体的过程开始于低于顺式-反式转化的浓度。前一过程在接近二级胶束 CMC（CMC2）的浓度时几乎完成，而后一过程即使在胆汁盐浓度远高于 CMC2 时也会发生。因此，DEC 可以用作探针，允许估计 CMC2 的值，并指示在胆汁盐浓度增加时二级胶束的重排。还观察到 DEC 和 Cyan 2 在胆汁盐上的聚集。由于它在相对较低的胆汁盐浓度（<CMC2）下观察到，因此聚集可能发生在胆汁盐的单体分子及其小的配合物和初级胶束上。形成的聚集体的分解始于胆汁盐浓度高于 CMC2（即与二级胶束相互作用时）。
