Characterization of horse kidney metallothionein isoforms by electrospray MS and reversed-phase HPLC-electrospray MS.
Résumé
Pneumatically assisted electrospray mass spectrometry (ESMS) in the direct mode and as a chromatog. detection technique was developed for the characterization of horse kidney metallothionein isoforms. Direct anal. in an acidic medium showed the presence of three major and five minor isoforms, the mol. masses of which were detd. The presence of the major isoforms (two of which matched the mol. masses calcd. according to the published sequences) was confirmed by complexation with Cd at pH 4.0 and the detn. of the stoichiometry of the complexes formed. Reversed-phase chromatog. of Cd7-MT complexes (pH 6.0) gave two signals corresponding to the MT-1A and MT-1B isoforms. A post-column acidification procedure was developed to eliminate the possibility of artifacts assocd. with the formation of mixed-metal (Cd, Zn) complexes during chromatog. in neutral media, to improve the accuracy of the detn. of the mol. mass of MT isoforms. [on SciFinder(R)]