John Allison

Professor

Students in Dr. Allison's group perform their research both in the Chemistry Department and in the NIH/MSU Mass Spectrometry Facility, which is located in the Biochemistry Building. Research topics include fundamental chemical studies, and biochemical applications of mass spectrometry.

Research in mass spectrometry (MS) represents a subset of chemical research in general. The technique is used to answer both fundamental questions and to pursue important applications in chemistry, physics, biochemistry, agriculture, the enviornmental sciences, etc. The 1990's promise to be an exciting decade in the field of mass spectrometry, not only because of its growing applications, but also because of recent instrumental developments. When commercial mass spectrometers were first available, gas phase molecules were converted into ions by electron impact ionization. With this method, compounds with molecular weights up to 500-600 could be characterized. In the past two decades, desorption/ionization techniques such as fast atom bombardment (FAB) were introduced. With FAB, solid samples with molecular weights up to 3500 could now be studied by mass spectrometry. Most recently, the technique of matrix-assisted laser desorption/ionization (MALDI) has been introduced, with a mass limit that appears to be beyond 300,000! In a short period of time, MS analyses have moved from small organic molecules to proteins and carbohydrates.

Unfortunately, commercial developments and opportunities move more quickly than science. While thousands of laboratories around the world use the technique of FAB, very little is known of how it works - what physical and chemical processes operate on a large molecule in the condensed phase to make it an ionized molecule in the gas phase? The same questions have yet to be answered for MALDI. Much of the research in the Allison group involves investigations into the mechanisms through which FAB and MALDI operate. The chemistry is very challenging, but once we understand how energy, in the form of high energy collisions or photons, is used to convert molecules into ions in these methods, we can optimize them and increase their utility.

Also, as the molecular weight of samples amenable to MS analysis increases, the complexity of the samples increases. Specifically, we are now faced with interpreting the mass spectra of highly functionalized molecules, in which secondary structures may be very influential. Most of the work done to understand how to interpret mass spectra - the relationship between the information in the mass spectrum and molecular structure - was done with small, monofunctional molecules. The Mass Spectrometry Community is unprepared for the complex challenges that face us, and a new level of understanding of ionization and fragmentation chemistry for peptides and carbohydrates is now required. The Allison group is also very active in this area.

Representative Publications:

1. "Renaissance of Gas Chromatography/Time-of-Flight Mass Spectrometry: Meeting the Challenge of Capillary Columns with a Beam Deflection Instrument and Time Array Detection", J.T. Watson, G.A. Schultz, R. Tecklenburg and J. Allison, J. Chromatog. 518, 283 (1990).

2. "Modified Residual Gas Analyzers as Sources of Mass-Selected Ion Beams", J.R. Gilbert, G.E. Leroi and J. Allison, Int. J. Mass Spectrom. Ion Proc. 107, 247 (1991).

3. "Selective Detection of the Tolyl Cation Among Other C7H7+ Isomers by Ion/Molecule Reactions with Dimethyl Ether", T.G. Heath, J. Allison and J.T. Watson, J. Am. Soc. Mass Spectrom. 2, 270 (1991).

4. "Bridging the Gap Between What Mass Spectrometrists Want and What Spectroscopists Can Do: An Instrument for Spectroscopic Investigation of Mastrix-Isolated, Mass-Selected Ions", M.S. Sabo, J. Allison, J.G. Gilbert and G.E. Leroi, Appl. Spectrosc. 45, 535 (1991).

5. "Understanding Ion Deceleration Lenses: What Are the Simplicity/Performance Trade-Offs?" P.J. O'Connor, G.E. Leroi and J. Allison, J. Am. Soc. Mass Spectrom. 2, 322 (1991).

6. "Complex Mixture Analysis Based on GC/MS with Time Array Detection Using a Novel Beam Deflection Time-of-Flight Mass Spectrometer", G.A. Schultz, B.A. Chamberlin, C.C. Sweeley, J.T. Watson and J. Allison, J. Chromatogr. 590, 329 (1992).

7. "Injection of Reagent Ions Into the Selvedged Region in Fast Atom Bombardment Mass Spectrometry", J.C. Rouse and J. Allison, J. Am. Soc. Mass Spectrom. 4, 259 (1993).

8. "PMA Induced Phosphorylation of OP18 in Jurkat T Cells: Identification of Physphorylation Sites by Matrix-Assisted Laser Desorption Ionization Mass Spectrometry", Y.K. Wang, P.C. Liao, J. Allison, D.A. Gage, P.C. Andrews, D.M. Lubman, S.M. Hanash and J.R. Strahler, J. Biol. Chem., in press (1993).

This page last updated November 12, 1997.