Abstract
Objectives: To determine the cause of an unusual hemoglobin (Hb) pattern detected during HbA(1)c monitoring.
Design and method: Hemolysate was analysed by ESI MS, and individual components purified by reverse phase HPLC. Peptide mapping was used to pinpoint the substitution and DNA sequencing to confirm the mutation.
Results: ESI MS of lysate showed three novel beta chains with mass changes of -83, -51 and +222 Da. Peptide mapping and DNA sequencing indicated a beta 37Trp -> Cys substitution. Reverse phase chromatography showed three new beta globins eluting ahead of beta(A)
Conclusion: The new Hbs result from an initial beta 37Trp -> Cys mutation (-83 Da) followed by oxidation to cysteine sulfinic acid (+32 Da) and the formation of a glutathione adduct (+305 Da). Despite the hydro-phobicity change and the critical location of the side chain on the alpha 1 beta 2 interface, there was no evidence of molecular instability or altered oxygen affinity, and no clear phenotype apart from discordant HbA(1)c. (C) 2011 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.