Characterization by tandem mass spectrometry of structural modifications in proteins

Tandem mass spectrometry can be used to solve a number of protein structural problems that are not amenable to conventional methods for amino acid sequencing. Typical problems that use this approach involve characterization of peptides with blocked amino termini or peptides that have been otherwise posttranslationally processed, such as, by phosphorylation or sulfation. The structure and homogeneity of synthetic peptides can also be evaluated. Since peptides can be selectively characterized in the presence of other peptides or contaminants, the need for extensive purification is reduced or eliminated.