Carclnogenesis vol.17 no.12 pp.2661-2671, 1996 Structural characterization by mass spectrometry of hemoglobin adducts formed after in vitro exposure to methyl bromide

'To whom correspondence should be addressed A mass spectrometric procedure is described for the struc-tural study of the adducts formed in human hemoglobin by in vitro exposure of erythrocytes to the alkylating agent methyl bromide using different protein to reagent ratios. Peptide mapping by HPLC and tandem mass spectrometry allowed location of methylated amino acids within the protein sequence. A prominent reactivity of several nucleo-philic side chains in human hemoglobin subunits was observed, which was modulated by the concentration of the alkylating agent Cysteine residues, the main reactive sites, were fully methylated in hemoglobin exposed to a 10-fold excess of methyl bromide, differently from other residues, including histidines, showing a heterogeneous pattern of methylation that was largely directed by thei