WeO-07


PROTEIN STRUCTURAL STUDIES IN THE GAS AND SOLUTION PHASE BY FOURIER TRANSFORM MASS SPECTROMETRY

G. H. Kruppa, F. H. Laukien, J. Wronka, J. P. Speir and T. Zhang

Bruker Analytical Systems Inc., Billerica, MA, USA


Electrospray Ionization (ESI) combined with Fourier Transform Mass Spectrometry (FTMS) has proved to be a powerful tool for the study of protein structure and folding. In many ways the information obtained from ESI-MS is complementary to the information obtained from NMR and X-Ray structural studies. Solution phase deuterium exchange experiments can be used to explore the native state structure of proteins, and pulsed labeling experiments allow for the study of folding kinetics in solution. Furthermore, fragmentation of proteins after pulsed labeling may provide site-specific information on the kinetics of folding.

Deuterium exchange reactions and proton abstraction reactions as well as gas phase fragmentations can be used to probe the gas phase structure of proteins. Evidence has been obtained and will be presented for isomeric protein structures in the gas phase analogous to structures observed in solution by NMR. If native-like conformations can be shown to exist in the gas phase, then it may become possible to measure gas-phase thermodynamics and kinetics for non-covalent interactions of proteins.

Results will be shown that illustrate the advantages of using Fourier Transform Mass Spectrometry for these types of studies. The high resolving power and extended m/z range of FTMS allow for the isotopic resolution of multiply charged protein-substrate complexes, even when overlapping species are present. This capability for high resolution is especially important for the successful analysis of the complex spectra that result from the fragmentation of a highly charged protein. Results that allow for the assignment of nearly all fragments in a complex MS/MS spectrum of a whole protein based on the resolution and mass accuracy of the technique will be shown.