Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada.
J Am Soc Mass Spectrom. 2011 Feb;22(2):290-9. doi: 10.1007/s13361-010-0026-3. Epub 2011 Jan 28.
Mass spectra of commercially obtained hemoglobin (Hb) show higher levels of monomer and dimer ions, heme-deficient dimer ions, and apo-monomer ions than hemoglobin freshly prepared from blood. This has previously been attributed to oxidation of commercial Hb. Further, it has been reported that that dimer ions from commercial bovine Hb have lower collision cross sections than low charge state monomer ions. To investigate these effects further, we have recorded mass spectra of fresh human Hb, commercial human and bovine Hb, fresh human Hb oxidized with H(2)O(2), lyophilized fresh human Hb, fresh human Hb both lyophilized and chemically oxidized, and commercial human Hb oxidized with H(2)O(2). Masses of α-monomer ions of all hemoglobins agree with the masses expected from the sequences within 3 Da or better. Mass spectra of the β chains of commercial Hb and oxidized fresh human Hb show a peak or shoulder on the high mass side, consistent with oxidation of the protein. Both commercial proteins and oxidized fresh human Hb produce heme-deficient dimers with masses 32 Da greater than expected and higher levels of monomer and dimer ions than fresh Hb. Lyophilization or oxidation of Hb both produce higher levels of monomer and dimer ions in mass spectra. Fresh human Hb, commercial human Hb, commercial bovine Hb, and oxidized commercial human Hb all give dimer ions with cross sections greater than monomer ions. Thus, neither oxidation of Hb or the difference in sequence between human and bovine Hb make substantial differences to cross sections of ions.
市售血红蛋白（Hb）的质谱显示，单体和二聚体离子、血红素缺失的二聚体离子和脱辅基单体离子的水平高于新鲜血液制备的血红蛋白。这以前归因于商业 Hb 的氧化。此外，据报道，商业牛 Hb 的二聚体离子的碰撞截面比低电荷状态的单体离子低。为了进一步研究这些影响，我们记录了新鲜人 Hb、商业人 Hb 和牛 Hb、用 H（2）O（2）氧化的新鲜人 Hb、冻干新鲜人 Hb、冻干和化学氧化的新鲜人 Hb 以及用 H（2）O（2）氧化的商业人 Hb 的质谱。所有血红蛋白的α-单体离子质量与序列预期的质量相差在 3 Da 或以内。商业 Hb 和氧化新鲜人 Hb 的β链的质谱在高质量侧显示一个峰或肩，与蛋白质的氧化一致。商业蛋白和氧化新鲜人 Hb 都产生质量比预期大 32 Da 的血红素缺失二聚体，以及比新鲜 Hb 更高水平的单体和二聚体离子。Hb 的冻干或氧化都会在质谱中产生更高水平的单体和二聚体离子。新鲜人 Hb、商业人 Hb、商业牛 Hb 和氧化商业人 Hb 都给出了截面大于单体离子的二聚体离子。因此，Hb 的氧化或人 Hb 和牛 Hb 之间序列的差异都不会对离子的截面产生实质性影响。
