Instituto de Química de São Carlos, Universidade de São Paulo, São Carlos, SP, Brazil.
Instituto de Química de São Carlos, Universidade de São Paulo, São Carlos, SP, Brazil.
Colloids Surf B Biointerfaces. 2014 Jun 1;118:14-24. doi: 10.1016/j.colsurfb.2014.03.021. Epub 2014 Mar 20.
Glossoscolex paulistus (HbGp) hemoglobin is an oligomeric protein, displaying a quaternary structure constituted by 144 globin and 36 non-globin chains (named linkers) with a total molecular mass of 3.6MDa. CTAC effects on the oxy-HbGp thermal stability were investigated, by DLS and SAXS, at pH 5.0, 7.0 and 9.0. DLS data show that the oxy-HbGp-CTAC interactions induce a significant decrease of the protein thermal stability, with the formation of larger aggregates, at pH 5.0 and 7.0. In the acidic pH, oxy-HbGp 0.5mg/mL, undergoes a partial oligomeric dissociation, on going from 0.2 to 0.6mmol/L of CTAC, accompanied by a decrease in the Dh values from 27±1 to 22±1nm. It is observed, for the first time, that in the absence and in the presence of CTAC, oxy-HbGp undergoes a partial oligomeric dissociation, with increase of temperature, before denaturation and aggregation at pH values 7.0 and 5.0. SAXS data show that oxy-HbGp undergoes denaturation at 60°C, in the presence of CTAC, pH 5.0. At neutral pH 7.0, the aggregation process starts at 20°C, with increase of Rg and Dmax parameters. At both pH values, 5.0 and 7.0, the denaturation and aggregation are accompanied by the sedimentation of the aggregates. At pH 9.0, oxy-HbGp is totally dissociated at 40°C, in the presence of 0.2mmol/L of CTAC, while in the presence of 0.4mmol/L of surfactant the aggregation process starts at 20°C, with the full denaturation of protein at higher temperature. Finally, our data show, for the first time, that the oligomeric dissociation is an important step in the thermal denaturation of oxy-HbGp, in the presence of CTAC, independently of both the pH and the protein concentration.
胶舌螺血红蛋白（HbGp）是一种寡聚蛋白，显示出由 144 个球蛋白和 36 个非球蛋白链（称为连接体）组成的四级结构，总分子量为 3.6MDa。通过动态光散射（DLS）和小角 X 射线散射（SAXS）研究了 CTAC 对氧合-HbGp 热稳定性的影响，实验在 pH5.0、7.0 和 9.0 下进行。DLS 数据表明，氧合-HbGp-CTAC 相互作用导致蛋白质热稳定性显著降低，在 pH5.0 和 7.0 时形成更大的聚集体。在酸性 pH 值下，0.5mg/mL 的氧合-HbGp 会发生部分寡聚体解离，当 CTAC 浓度从 0.2mmol/L 增加到 0.6mmol/L 时，Dh 值从 27±1nm 降低到 22±1nm。这是首次观察到，在不存在和存在 CTAC 的情况下，氧合-HbGp 在 pH7.0 和 5.0 下，在变性和聚集之前，随着温度的升高，会发生部分寡聚体解离。SAXS 数据表明，在 pH5.0 下，存在 CTAC 时，氧合-HbGp 在 60°C 下发生变性。在中性 pH7.0 下，聚合过程在 20°C 时开始，随着 Rg 和 Dmax 参数的增加。在这两个 pH 值（5.0 和 7.0）下，变性和聚集伴随着聚集体的沉淀。在 pH9.0 下，在 0.2mmol/L CTAC 的存在下，氧合-HbGp 在 40°C 时完全解离，而在 0.4mmol/L 表面活性剂的存在下，聚合过程在 20°C 时开始，随着温度的升高，蛋白质完全变性。最后，我们的数据首次表明，寡聚体解离是 CTAC 存在下氧合-HbGp 热变性的重要步骤，这与 pH 值和蛋白质浓度无关。
