Structural characterization of monomeric folding intermediates of recombinant human macrophage-colony stimulating factor beta (rhM-CSFbeta) by chemical trapping, chromatographic separation and mass spectrometric peptide mapping.

We have developed a strategy for the characterization of protein folding intermediates that combines selective modification of bis-cysteinyl thiol groups with melarsen oxide (MEL), chromatographic separation and mass spectrometric characterization of the resulting protein derivatives. In the unfolding reaction of recombinant human macrophage-colony stimulating-factor beta (rhM-CSFbeta) we observed monomeric M.4MEL and dimeric D.