An electrospray mass spectrometric approach to the identification of a human hemoglobin (Hb) variant involving a Cys residue incorporation is presented. In Hb Ta-Li (beta83Gly --> Cys), Cys83 forms inter-molecular disulfide bridges. Routine analysis of the denatured Hb showed the presence of a minor beta chain variant whose mass apparently was 1 Da less than the expected mass difference of 46 Da for a Gly --> Cys substitution. Reduction of the globin chains with dithiothreitol gave an intense monomer with the expected mass difference for the Gly --> Cys substitution. After reprocessing the original raw data from the denatured Hb and taking into account the possibility of dimer formation, a component was revealed whose mass was consistent with a disulfide linked dimer of Ta-Li beta globins. The mutation was localized to peptide betaT10 by analysis of a tryptic digest. Tandem mass spectrometry and DNA sequencing confirmed the Gly --> Cys substitution occurred at residue 83 of the beta chain. Problems encountered in identifying the components in mixtures of monomers and dimers are discussed.

中文翻译：

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通过电喷雾质谱法表征形成人类Hb变体的难以捉摸的二硫键：Hb Ta-Li beta83（EF7）Gly-> Cys。

提出了一种电喷雾质谱方法，用于鉴定涉及Cys残基掺入的人血红蛋白（Hb）变异体。在Hb Ta-Li（beta83Gly-> Cys）中，Cys83形成分子间二硫键。对变性的Hb进行的常规分析表明，存在一个较小的β链变异体，其质量显然比Gly-> Cys取代的预期质量差46 Da小1 Da。用二硫苏糖醇还原球蛋白链得到强烈的单体，其对于Gly→Cys的取代具有预期的质量差异。在从变性的血红蛋白中重新处理原始原始数据并考虑到形成二聚体的可能性后，发现了一个成分，其质量与Ta-Liβ珠蛋白的二硫键连接的二聚体一致。通过分析胰蛋白酶消化，将该突变定位于肽βT10。串联质谱和DNA测序证实，Gly-> Cys取代发生在β链的第83位残基。讨论了识别单体和二聚体混合物中的组分时遇到的问题。