Instituto de Química de São Carlos, Universidade de São Paulo, SP, Brazil.
Biophys Chem. 2010 Nov;152(1-3):128-38. doi: 10.1016/j.bpc.2010.08.010. Epub 2010 Sep 7.
Glossoscolex paulistus hemoglobin (HbGp) was studied by dynamic light scattering (DLS), optical absorption spectroscopy (UV-VIS) and differential scanning calorimetry (DSC). At pH 7.0, cyanomet-HbGp is very stable, no oligomeric dissociation is observed, while denaturation occurs at 56°C, 4°C higher as compared to oxy-HbGp. The oligomeric dissociation of HbGp occurs simultaneously with some protein aggregation. Kinetic studies for oxy-HbGp using UV-VIS and DLS allowed to obtain activation energy (E(a)) values of 278-262 kJ/mol (DLS) and 333 kJ/mol (UV-VIS). Complimentary DSC studies indicate that the denaturation is irreversible, giving endotherms strongly dependent upon the heating scan rates, suggesting a kinetically controlled process. Dependence on protein concentration suggests that the two components in the endotherms are due to oligomeric dissociation effect upon denaturation. Activation energies are in the range 200-560 kJ/mol. The mid-point transition temperatures were in the range 50-65 °C. Cyanomet-HbGp shows higher mid-point temperatures as well as activation energies, consistent with its higher stability. DSC data are reported for the first time for an extracellular hemoglobin.
采用动态光散射（DLS）、紫外可见吸收光谱（UV-VIS）和差示扫描量热法（DSC）研究了 Glossoscolex paulistus 血红蛋白（HbGp）。在 pH 7.0 时，氰合-HbGp 非常稳定，未观察到寡聚体解离，而在 56°C 时发生变性，比氧合-HbGp 高 4°C。HbGp 的寡聚体解离与一些蛋白质聚集同时发生。使用 UV-VIS 和 DLS 对氧合-HbGp 的动力学研究可以获得活化能（E(a)）值为 278-262 kJ/mol（DLS）和 333 kJ/mol（UV-VIS）。补充的 DSC 研究表明，变性是不可逆的，吸热强烈依赖于加热扫描速率，表明这是一个动力学控制的过程。对蛋白质浓度的依赖性表明，两个吸热峰中的两个组分是由于寡聚体解离对变性的影响。活化能在 200-560 kJ/mol 范围内。中点转变温度在 50-65°C 范围内。氰合-HbGp 表现出更高的中点温度和活化能，与其更高的稳定性一致。这是首次为细胞外血红蛋白报告 DSC 数据。
