This service affords an opportunity for protein structure determinations based on the pattern of product ions produced upon fragmentation of the species of interest. Routinely, ESI-MS/MS is used to verify the predicted sequence of an expressed recombinant protein (and to identify sites of unintended mutations), as well as to quantify the extent of chemical modifications introduced into a purified protein in vitro (e.g., phosphorylation, biotinylation, fluorescein labeling). Structural information on low mass, non-volatile polar compounds (synthetic or natural) can also often be provided. Non-routine application of ESI-MS/MS include identification of the nature and sites of in vivo protein modifications, protein multimeric status, cysteine residues engaged in disulfide bonds, amino acid sequence analysis, and non-covalent protein-protein interactions. It is also useful in microheterogeneity studies of isolated proteins, and can provide some tertiary structure information on native and partially denatured proteins. It should be appreciated that these non-routine applications of ESI-MS/MS utilize approaches that may be successfully applied in some, but not all cases. ESI-MS/MS samples should be provided in volatile polar/aqueous solvents containing less than 500 µM salt. Necessary protein quantities may range from 20-500 pmol, depending on the specific information desired.
Eugene J. Davidov, Ph.D., Director
Yale University, 219 Prospect St, KBT, 700, New Haven, CT 06520