Cation Modulation of Hemoglobin Interaction with Sodium <Emphasis Type="Italic">n</Emphasis>-Dodecyl Sulfate (SDS). I: Calcium Modulation at pH 7.20 |
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Authors: | Ferdinand C Chilaka Charles Okechukwu Nwamba Ali Akabar Moosavi-Movahedi |
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Institution: | (1) Department of Biochemistry, University of Nigeria, Nsukka, Nigeria;(2) Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran |
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Abstract: | 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. |
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