Department of Biology, Mashhad Branch, Islamic Azad University, Mashhad, Iran.
Department of Medicinal Chemistry, School of Pharmacy, Mashhad University of Medical Sciences, Mashhad, Iran.
J Biomol Struct Dyn. 2024 Aug;42(12):5995-6012. doi: 10.1080/07391102.2023.2230295. Epub 2023 Jul 4.
The aim of this study was to investigate the behavior interaction of α-Casein-B and β-Casein-B complexes as binary systems through the methods of multiple spectroscopic, zeta potential, calorimetric, and molecular dynamics (MD) simulation. Fluorescence spectroscopy denoted the role ofBas a quencher in both cases of α-Casein and β-Casein fluorescence intensities, which also verifies the existence of interactions. The quenching constants of α-Casein-B and β-Casein-B complexes at 298 K in the first set of binding sites were 2.89 × 10 and 4.41 × 10 M, while the constants of second set of binding sites were 8.56 × 10 and 1.58 × 10 M, respectively. The data of synchronized fluorescence spectroscopy at Δλ = 60 nm were indicative of the closer location of β-Casein-B complex to the Tyr residues. Additionally, the binding distance between B and the Trp residues of α-Casein and β-Casein were obtained in accordance to the Förster's theory of nonradioactive energy transfer to be 1.95 nm and 1.85 nm, respectively. Relatively, the RLS results demonstrated the production of larger particles in both systems, while the outcomes of zeta potential confirmed the formation of α-Casein-B and β-Casein-B complexes and approved the existence of electrostatic interactions. We also evaluated the thermodynamic parameters by considering the fluorescence data at three varying temperatures. According to the nonlinear Stern-Volmer plots of α-Casein and β-Casein in the presence of B in binary systems, the two sets of binding sites indicated the detection of two types of interaction behaviors. Time-resolved fluorescence results revealed that the fluorescence quenching of complexes are static mechanism. Furthermore, the outcomes of circular dichroism (CD) represented the occurrence of conformational changes in α-Casein and β-Casein upon their binding to B as the binary system. The experimental results that were obtained throughout the binding of α-Casein-B and β-Casein-B complexes were confirmed by molecular modeling.Communicated by Ramaswamy H. Sarma.
本研究旨在通过多种光谱学、动电电位、量热法和分子动力学（MD）模拟方法，研究α-酪蛋白-B 和 β-酪蛋白-B 二元体系的行为相互作用。荧光光谱表示 Bas 作为α-酪蛋白和β-酪蛋白荧光强度的猝灭剂，这也验证了相互作用的存在。在第一组结合位点中，298 K 时α-酪蛋白-B 和β-酪蛋白-B 复合物的猝灭常数分别为 2.89×10 和 4.41×10 M，而第二组结合位点的常数分别为 8.56×10 和 1.58×10 M。在Δλ=60nm 处的同步荧光光谱数据表明β-酪蛋白-B 复合物与 Tyr 残基的位置更接近。此外，根据福斯特非放射性能量转移理论，获得了 B 与α-酪蛋白和β-酪蛋白的 Trp 残基之间的结合距离，分别为 1.95nm 和 1.85nm。相对而言，RLS 结果表明两个系统中都产生了更大的颗粒，而动电电位的结果则证实了α-酪蛋白-B 和β-酪蛋白-B 复合物的形成，并证实了静电相互作用的存在。我们还通过考虑三个不同温度下的荧光数据来评估热力学参数。根据二元体系中 B 存在时α-酪蛋白和β-酪蛋白的非线性 Stern-Volmer 图谱，两组结合位点表明检测到两种类型的相互作用行为。时间分辨荧光结果表明，复合物的荧光猝灭是静态机制。此外，圆二色性（CD）的结果表明，在二元体系中，α-酪蛋白和β-酪蛋白与 B 结合时发生构象变化。通过分子建模验证了获得的α-酪蛋白-B 和β-酪蛋白-B 复合物结合的实验结果。由 Ramaswamy H. Sarma 传达。
