Thermodynamic Characterization of Acacia Gum-β-Lactoglobulin Complex Coacervation
Thermodynamic Characterization of Acacia Gum-β-Lactoglobulin Complex Coacervation
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DOI：
10.1021/la100705d
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发表时间：
2010-08-03
期刊：
影响因子：
3.9
通讯作者：
Sanchez, Christian
中科院分区：
文献类型：
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作者：
Aberkane, Leila;Jasniewski, Jordane;Sanchez, Christian
已在 pH 4.2 和 25 摄氏度下研究了水溶液中 β-乳球蛋白 (BLG) 与总阿拉伯胶 (TAG) 的相互作用。等温滴定量热法 (ITC) 已用于确定 TAG 与 BLG 络合过程中涉及的能量的类型和大小。动态光散射 (DLS)、电泳迁移率 (mu(E))、浊度测量 (tau) 和光学显微镜被用作滴定模式的补充方法，以更好地理解热力学行为起源的复杂现象的总和。检测到两个不同的结合步骤。热力学参数表明第一个放热步骤的关联常数 K-al 为 (48.4 +/- 3.6) x 10(7) M-1，这似乎主要是由焓驱动的。在静电相互作用的特征处获得了对应的正热容变化。第二个结合步骤，亲和力降低了 45 倍（K-a2 = (1.1 +/- 0.1) x 10(7) M-1），主要是吸热的，更多是由熵驱动的，热容变化为负值，表明疏水性对结合过程的贡献。通过 DLS 确定溶液中不同物种的种群分布及其大小。颗粒的分散浊度显着增加，并在TAG/BLG摩尔比为0.015时达到最大值。在该摩尔比（0.015）下出现了更多数量的凝聚层，并且对于大凝聚层注意到两种不同的形态。 TAG/BLG 摩尔比高于 0.015 时，分散体浊度下降，这可能是由于电泳迁移率测量显示颗粒上带有过量的负电荷。本研究中提出的结果应提供有关 TAG/BLG 结合过程的热力学机制的信息，并将促进形成的超分子组装体作为食品和非食品系统中的功能成分的应用。
The interactions of beta-lactoglobulin (BLG) with total acacia gum (TAG) in aqueous solutions have been investigated at pH 4.2 and 25 degrees C. Isothermal titration calorimetry (ITC) has been used to determine the type and magnitude of the energies involved in the complexation process of TAG to BLG. Dynamic light scattering (DLS), electrophoretic mobility (mu(E)), turbidity measurements (tau), and optical microscopy were used as complementary methods on the titration mode to better understand the sum of complicated phenomena at the origin of thermodynamic behavior. Two different binding steps were detected. Thermodynamic parameters indicate a first exothermic step with an association constant K-al of (48.4 +/- 3.6) x 10(7) M-1 that appeared to be mostly enthalpy-driven. A positive heat capacity change was obtained corresponding at the signature for electrostatic interactions. The second binding step, 45 times less affinity (K-a2 = (1.1 +/- 0.1) x 10(7) M-1), was largely endothermic and more entropy-driven with a negative value of heat capacity change, indicative of a hydrophobic contribution to the binding process. The population distribution of the different species in solution and their sizes were determined through DLS. Dispersion turbidity of particles markedly increased and reached a maximum at a 0.015 TAG/BLG molar ratio. Largely more numerous coacervates appeared at this molar ratio (0.015) and two different kinds of morphologies were noticed for the large coacervates. Above the TAG/BLG molar ratio of 0.015, dispersions turbidity decreased, which might be due to an excess of negative charges onto particles as revealed by electrophoretic mobility measurements. The results presented in this study should provide information about the thermodynamic mechanisms of TAG/BLG binding processes and will facilitate the application of the formed supramolecular assemblies as functional ingredients in food and nonfood systems.