Mund-Lagowski Department of Chemistry and Biochemistry, Bradley University, 1501 West Bradley Avenue, Peoria, IL 61625, USA.
CMC Materials, Incorporated, 870 North Commons Drive, Aurora, IL 60504, USA.
Spectrochim Acta A Mol Biomol Spectrosc. 2023 Sep 5;297:122710. doi: 10.1016/j.saa.2023.122710. Epub 2023 Apr 6.
Intermolecular interactions in buffered aqueous solution between the polycation, poly(2-(trimethylamino)ethyl methacrylate) chloride (pTMAEMC) and two anionic xanthene dyes, 2', 7'-difluorofluorescein (Oregon Green 488) and 2, 4, 5, 7-tetraiodofluorescein (Erythrosin B), are characterized using multiple optical spectroscopic methods. Visible absorption spectroscopy indicates the formation of ground-state pTMAEMC-dye complexes. Benesi-Hildebrand binding isotherm analysis of visible absorption spectra for pTMAEMC-dye mixtures quantifies the strength of binding interactions producing the complexes. For both Oregon Green 488 (OG) and Erythrosin B (EB) in mixtures with pTMAEMC, the concentration of the solution's sodium acetate buffer at a fixed pH alters the binding constants, K, suggesting that ionic strength plays a key role in determining the binding affinity of pTMAEMC for the dyes. Comparison of K, for the dyes indicates stronger binding of EB under all solution conditions. Steady-state fluorescence emission spectroscopy, fluorescence quenching, excited-state fluorescence lifetime measurements and fluorescence correlation spectroscopy provide complementary data for the interactions between pTMAEMC and the dyes. Mixtures of pTMAEMC with the dyes produce fluorescence enhancements and fluorescence quenching which exhibit a dependence on the buffer concentration used in the mixture. Excited-state lifetime analysis indicates that OG interacts with pTMAEMC through ground-state interactions while EB exhibits both ground-state and excited-state interactions with pTMAEMC. The spectroscopic measurements suggest that a polyelectrolyte effect for pTMAEMC due to ionic strength variation produced by the buffer concentration affects the dye binding profile of the polycation. This conclusion is supported by fluorescence correlation spectroscopy (FCS) analyses of the hydrodynamic diameter changes in pTMAEMC-OG binding in low buffer concentration (low ionic strength) solution. FCS analyses of pTMAEMC-OG mixtures also reveal diversity in the complexes formed in low ionic strength solution suggesting that other xanthene dyes will exhibit similar binding behaviors in mixtures with pTMAEMC as a function of solution ionic strength.
在缓冲水溶液中，聚阳离子聚（2-（三甲氨基）乙基甲基丙烯酸酯）氯化物（pTMAEMC）与两种阴离子呫吨染料 2'，7'-二氟荧光素（Oregon Green 488）和 2,4,5,7-四碘荧光素（Erythrosin B）之间的分子间相互作用，通过多种光学光谱方法进行了表征。可见吸收光谱表明形成了基态 pTMAEMC-染料配合物。pTMAEMC-染料混合物可见吸收光谱的 Benesi-Hildebrand 结合等温线分析定量了形成配合物的结合相互作用的强度。对于混合物中的 Oregon Green 488（OG）和 Erythrosin B（EB）与 pTMAEMC，固定 pH 值下溶液的醋酸钠缓冲液浓度会改变结合常数 K，表明离子强度在确定 pTMAEMC 与染料的结合亲和力方面起着关键作用。比较染料的 K 值表明，在所有溶液条件下，EB 的结合更强。稳态荧光发射光谱、荧光猝灭、激发态荧光寿命测量和荧光相关光谱为 pTMAEMC 与染料之间的相互作用提供了补充数据。pTMAEMC 与染料的混合物产生荧光增强和荧光猝灭，其表现出对混合物中使用的缓冲液浓度的依赖性。激发态寿命分析表明，OG 通过基态相互作用与 pTMAEMC 相互作用，而 EB 与 pTMAEMC 表现出基态和激发态相互作用。光谱测量表明，缓冲液浓度引起的离子强度变化对 pTMAEMC 的聚电解质效应会影响聚阳离子的染料结合谱。荧光相关光谱（FCS）分析在低缓冲浓度（低离子强度）溶液中 pTMAEMC-OG 结合的水动力直径变化支持了这一结论。pTMAEMC-OG 混合物的 FCS 分析还揭示了低离子强度溶液中形成的复合物的多样性，表明其他呫吨染料在与 pTMAEMC 的混合物中作为溶液离子强度的函数将表现出类似的结合行为。
