ELECTROSPRAY TANDEM MASS-SPECTROMETRY OF HUMAN HEMOGLOBIN AND A NUMBER OF BETA-CHAIN ABERRANTS

The use of electrospray tandem mass spectrometry is demonstrated for t he characterisation of the polypeptide chains of normal human haemoglo bin and a number of beta-chain variants. Rapid screening of aberrant h aemoglobins is achieved by the analysis of diluted blood without need for pretreatment or sample work-up, Gas-phase sequencing of the intact polypeptide chains shows that almost half of the amino acid sequence may be realised by this approach. More comprehensive coverage of the s equence (in excess of 80%) is given by cyanogen bromide digestion of w hole blood followed by gas-phase sequencing of the resulting peptide f ragments. The simplicity of the cyanogen bromide peptide map, accounti ng for the entire alpha- and beta-chain sequences, is a distinct advan tage of the method, Limitations of characterising aberrant proteins in triple quadrupole instruments are discussed with respect to mass accu racy and the effect of fragment ion charge state on detecting amino ac id substitutions.