Analysis of artificial proteins by matrix-assisted laser desorption mass spectrometry

The growing use of recombinant DNA methods for the preparation of artificial proteins has created a pressing need for techniques for the rapid analysis of macromolecular structure. We report herein the use of matrix-assisted laser desorption mass spectrometry to determine the structure and purity of an artificial copolypeptide prepared as part of our ongoing investigation of the crystallization behavior of periodic protein. The mass spectra demonstrate that SDS polyacrylamide gel electrophoresis (SDS-PAGE) is insensitive to the presence of degraded fragments of the artificial protein and that molecular masses estimated by SDS-PAGE may be in error by more than 100%. Furthermore, accurate mass determination by matrix-assisted laser desorption mass spectrometry allowed the discovery of two previously undetected mutations in the DNA code for the protein.