Our research group exploits the remarkable properties of laser light in various experiments in bioanalytical chemistry and high resolution mass spectrometry. We are interested in both the development of new techniques and in their application to solving scientific problems. We are currently investigating:

1. Efficient biomolecular ion production. Biological macromolecules tend to be crystalline substances that are stable in aqueous solutions. To measure their molecular masses, we must put them into the gas phase and ionize them. Matrix-assisted laser desorption/ionization (MALDI), a method that was developed in the late 1980's in Germany by Hillenkamp and co-workers, can accomplish this. The current challenge is to detect molecules that we are particularly interested in when they are surrounded by an abundance of background. We therefore work on various sample preparation approaches that enhance the yields of certain biomolecular ions. Some of these involve selective capture of molecules on surfaces. Others involve molecular tagging to increase ion yields. In all cases, our goal is to improve the sensitivity and selectivity of biomolecule mass spectrometry.

2. Proteomics. We are developing mass spectrometric methods for analyzing the protein constituents of cells. This involves chromatographic and electrophoretic fractionation of cellular lysates, robotically controlled sample preparation and MALDI and electrospray ionization mass spectrometry for detection and identification. Proteins are identified by their molecular weights and isoelectric points, through peptide mass maps and by sequencing proteolytically generated representative peptides. Our own in-house proteomics software, which is continuously evolving, keeps track of all this information. A particular focus of this work involves the identification of ribosomal proteins and their post-translational modifications.

3. Fragmentation of peptide ions. Ion fragmentation can be desirable or undesirable, depending on how extensive it is and on the nature of the mass spectrometry experiment. The best situation is to have some control over the fragmentation process. Laser induced photofragmentation provides us with a number of technological advantages over collision induced dissociation that we are exploiting on a number of instrumental platforms.

4. Cellular fingerprinting. For a number of years we have been interested in molecules synthesized by bacteria. Recently we have begun to investigate proteins that bacteria export into their surroundings. Some of these become bound to the outer surface of the bacteria, others diffuse outward into the local environment. Since these proteins play a significant role in bacterial toxicity, we are investigating conditions under which their production varies.

5. Protein structure and protein-protein interactions. The structures of most proteins that are bound to surfaces or involved in interactions with other molecules often cannot be determined by x-ray crystallography. Chemical derivatizations can provide key structural information by establishing regions of interaction. Ribosomes are large complexes of protein and ribonucleic acids that provide an excellent application of this technology.

5. Novel time-of-flight instrumentation. We have been involved in the development of TOF mass spectrometers for many years. Through computer-assisted ion trajectory calculations, we continue to look at new designs in an attempt to optimize the sensitivity and resolution of our instruments. We are currently developing hybrid TOF MS/MS instruments that feature ultraviolet laser-induced ion photofragmentation. They will be invaluable in peptide sequencing and proteomics experiments.