ELECTROSPRAY-IONIZATION MASS-SPECTROMETRY FOR THE STUDY OF NONCOVALENT COMPLEXES - AN EMERGING TECHNOLOGY

The detection of non-covalent complexes in the mass range 19 000-34 00 0 Da, using electrospray ionization mass spectrometry (ESI-MS), is rev iewed. The examples discussed include (1) a protein-ligand interaction (ras-GDP), (2) an inhibitor-protein-ligand interaction (SCH 54292/SCH 54341-ras-GDP), (3) a protein-protein interaction (gamma-IFN homodime r) and (4) a protein-metal complex [HCV (1-181)-Zn]. In each case, the ESI-MS method is capable of releasing the intact non-covalent complex from its native solution state into the gas phase in the form of mult iply-charge ions. The molecular masses of these complexes were determi ned with a mass accuracy of better than 0.01%, which is far superior t o the traditional methods of sodium dodecyl sulfate polyacrylamide gel electrophoresis and gel permeation chromatography. The method provide s the researcher with a quick, reliable and reproducible method for pr obing difficult biological problems. The key to success in the study o f non-covalent complexes depends on careful understanding and manipula tion of ESI source parameters and sample solution conditions; special care must be taken with the source orifice potential and the solution pH and organic co-solvents must be avoided. This paper also illustrate s the usefulness of ESI-MS for addressing biological problems leading to the discovery of new therapeutics; the approach involves the rapid screening of potential drug candidates, such as weakly bound inhibitor s. (C) 1998 John Wiley & Sons, Ltd.