Abstract

The absorption and fluorescence spectral properties of three meso-substituted hydrophilic thiacarbocyanine dyes were studied in solutions and in noncovalent complexes with human and bovine serum albumins (HSA and BSA, respectively). The presence of alkyl substituents at the meso-position of the polymethine chain of the dyes determines the occurrence of a cis–trans equilibrium. Dyes form aggregates in aqueous media; the effect of electrolyte (NaCl) on aggregation has been studied. The interaction of the dyes with albumins leads to the decomposition of the aggregates and is accompanied by a shift in the isomeric equilibrium. Complexation with HSA leads to accumulation of dye monomers in the trans-form. However, in the case of BSA the cis-to-trans isomeric shift is incomplete. Using the fluorescence data, the effective binding constants of the trans-isomers with albumins (K_a) and the detection limits of albumin molecules (LD and LQ) were determined. The data obtained are indicative of high selectivity of some dyes to HSA compared to BSA. The results of molecular docking experiments correspond to the data obtained from the spectra. The influence of the dyes on intrinsic fluorescence of HSA and BSA was also studied, and fluorescence quenching, static in nature, was detected.

Graphic abstract

中文翻译：

---

溶液中和与血清白蛋白复合的亲水性内消旋花菁染料：光谱性质和分子对接研究

摘要

在溶液中以及在与人和牛血清白蛋白（分别为HSA和BSA）的非共价配合物中，研究了三种内消旋取代的亲水性硫杂碳菁花青染料的吸收和荧光光谱性质。在烷基取代基的存在内消旋染料的甲基链的位上确定的发生顺式-反式平衡。染料在水性介质中形成聚集体。研究了电解质（NaCl）对聚集的影响。染料与白蛋白的相互作用导致聚集体的分解，并伴随着异构体平衡的移动。与HSA的络合导致反式染料单体的积累-形成。然而，在BSA的情况下，顺至-反式异构体转变是不完整的。利用荧光数据，确定反式异构体与白蛋白的有效结合常数（K _a）和白蛋白分子的检测限（LD和LQ）。获得的数据表明，与BSA相比，某些染料对HSA的选择性高。分子对接实验的结果与从光谱获得的数据相对应。还研究了染料对HSA和BSA固有荧光的影响，并检测了荧光猝灭的性质。

图形摘要