Interaction between humic acid and lysozyme, studied by dynamic light scattering and isothermal titration calorimetry.
Interaction between humic acid and lysozyme, studied by dynamic light scattering and isothermal titration calorimetry.
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DOI：
10.1021/es802387u
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发表时间：
2009-02
影响因子：
11.4
通讯作者：
W. Tan;L. Koopal;W. Norde
中科院分区：
文献类型：
--
作者：
W. Tan;L. Koopal;W. Norde
采用动态光散射和等温滴定量热法研究了纯化奥德里奇腐殖酸（PAHA）与蛋白质溶菌酶（LSZ）的相互作用。在所研究的pH值下，溶液中LSZ为正，PAHA为负。高达中等KCl浓度没有发生聚集LSZ和PAHA聚集颗粒的平均半径为80 nm的存在。PAHA与LSZ的络合在PAHA加入LSZ后立即开始，并且当接近络合物的等电点（IEP）时，随后发生聚集。对于50 mM KCl，聚集是逐渐的，而对于低KCl浓度，聚集是突然的。聚集体尺寸在络合物的IEP处最大。在质量比超过IEP时，聚集体部分解聚。在不存在盐的情况下形成的PAHA和LSZ的带正电荷的复合物在盐添加后强烈聚集。LSZ和PAHA的混合最初是由化学驱动的。在IEP附近，络合和聚集是由于疏水力（结构重组）和反离子释放。当蛋白质带正电荷时，观察结果与其他HA-蛋白质系统相关。
Interactions of purified Aldrich humic acid (PAHA) with the protein lysozyme (LSZ) are studied with dynamic light scattering and isothermal titration calorimetry by mixing LSZ and PAHA at various mass ratios. In solution LSZ is positive and PAHA is negative at the investigated pH values. Up to moderate KCl concentrations no aggregation occurs for LSZ and for PAHA aggregated particles with an average radius of 80 nm are present. Complexation of PAHA with LSZ starts as soon as PAHA is added to LSZ and is followed by aggregation when the isoelectric-point (IEP) of the complexes is approached. Aggregation is gradual for 50 mM KCl and sudden for low KCl concentrations. The aggregate size is at its maximum at the IEP of the complexes. At mass ratios beyond the IEP the aggregates partially disaggregate. Positively charged complexes of PAHA and LSZ, formed in the absence of salt strongly aggregate upon salt addition. Mixing of LSZ and PAHA is initially enthalpically driven. Near the IEP complexation and aggregation are due to hydrophobic forces (structural reorganization) and counterion release. The observations are relevant for other HA-protein systems when the protein is positively charged.