Department of Biochemistry, University of Nigeria, Nsukka, Nigeria.
Cell Biochem Biophys. 2011 Jul;60(3):187-97. doi: 10.1007/s12013-010-9139-3.
A comparative denaturation of HbA and HbS in the R states using sodium n-dodecyl sulfate (SDS) was carried out at pH 7.20 in the presence and absence of Calcium (0-40 μM) and monitored by UV-Vis spectrophotometry in the range of 250-650 nm. In the HbS spectra, the calcium alone caused little or no perturbation of the aromatic region but caused a decrease in oxygen affinity when compared to the HbA. The combinations of [SDS] and [Ca] perturbed the HbS the most, relative to the individual spectra of the [SDS] and [Ca]. However, the presence of Ca appeared to diminish the adverse effects of the SDS on HbA. The denaturation pathway of the HbA involved mainly the formation of heme dimers and some ferryl heme species. For the HbS, heme monomers and a large amount of ferryl species were formed. It is suggested that the greater monomer species formed by the HbS denaturation pathway would result in both Fenton and enhanced enzymatic reactions, compared to the dimer. This could lead ultimately to the formation of ferryl radicals. Thus, at physiological pH for the HbS, the Ca-SDS interaction increases the tendency for protein denaturation in comparison to the HbA.
在 pH 值为 7.20 的条件下，使用十二烷基硫酸钠（SDS）对 R 态下的 HbA 和 HbS 进行比较变性，在 250-650nm 的范围内通过紫外可见分光光度法监测，同时存在和不存在钙（0-40μM）。在 HbS 光谱中，钙单独作用对芳香族区域几乎没有或没有干扰，但与 HbA 相比，氧亲和力降低。与 SDS 和 Ca 的单独光谱相比，[SDS]和[Ca]的组合对 HbS 的干扰最大。然而，钙的存在似乎减轻了 SDS 对 HbA 的不利影响。HbA 的变性途径主要涉及血红素二聚体和一些高铁血红素物种的形成。对于 HbS，形成了血红素单体和大量高铁血红素物种。有人认为，与二聚体相比，HbS 变性途径形成的更大单体物种将导致 Fenton 和增强的酶反应。这最终可能导致高铁自由基的形成。因此，与 HbA 相比，在生理 pH 值下，Ca-SDS 相互作用增加了 HbS 蛋白质变性的趋势。
