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R. Graham Cooks
Professor of Chemistry
The recipient of the Herbert Newby McCoy Award for 1990 is R. Graham Cooks, Henry Bohn Hass Distinguished Professor of Chemistry. Graham Cooks is an analytical chemist whose research interests cover instrument development, fundamentals, and practical applications of mass spectrometers. He was born in South Africa, educated at Cambridge, and entered the United States through Kansas. He has Ph.D.s from the University of Natal and Cambridge University in organic chemistry. He taught at Kansas State University from 1968 to 1971 and since then has been at Purdue University. Apart from research, his main enthusiasms are gardening and poetry. Professor Cooks' work has earned him the Thomas medal for contributions to international mass spectrometry and the Instrumentation Award of the Analytical Division of the American Chemical Society.
Miniscule amounts of particular organic compounds can be detected in the Wabash River, the smoke emitted by the North Power Plant, and the soil around the Entomology Building. Methods for making these measurements are detailed in the Federal Register, and results of these analyses are the frequent subject of litigation. How- ever, even an avid listener to WBAA could be excused for being ignorant of the principal scientific instrument used to make these measurements: this instrument is the mass spectrometer. This talk will describe its remarkable evolution, from its invention by J. J. Thomson for the measurement of the mass of the electron and its contribution to the discovery of isotopes and the mass defects of atoms, to its large scale use in isotope separation during the Manhattan Project. Particular emphasis will go to chemical applications of the device which began in the 1940s with the quantitation of hydrocarbon mixtures during petroleum refining and grew to include molecular weight, molecular formula, and structural characterization of organic, inorganic, and, most recently, biological compounds. Special attention will go to current capabilities of mass spectrometry, including on-line analysis of bioreactors, biopolymer sequencing, and the ability to contain gaseous ions in miniature ion traps where their reactions can be followed and their chemical structures determined. Problems studied in collaboration with other Purdue scientists, such as cactus taxonomy, drug metabolism, chemical carcinogenesis, catalyst characterization, the chemical structure of coal, and the nature of the active principles in traditional herbal remedies will be described.
Graham Cooks studied natural products - including the isolation and structural characterization of alkaloids from mangrove species - for his graduate work. He spent two years on the project before a two-day stint on a mass spectrometer yielded the correct answer. Not quite convinced, he studied organic mechanisms at Cambridge, but simultaneously began a second, largely nocturnal career, examining reactions in the mass spectrometer. Over the past 10 years his group has built eight new mass spectrometers. Several of the instruments have been developed in collaboration with manufacturers and have served as prototypes of commercial instruments. There is a revolution underway in/mass spectrometry, and Cooks and his group are proud to be a part of it. Cooks pioneered the use of tandem mass spectrometers (MS/MS) for the analysis of complex mixtures, recognizing the capabilities of such instruments for rapid isolation of compounds of interest and their molecular characterization through reassembly of the fragments yielded upon collision with gas molecules. The method was developed in 1975 and is now widely used, hundreds of instruments being applied in pharmacological, environmental, and chemical laboratories world-wide. Hand in hand with this applied work, Cooks has studied fundamental aspects of ion chemistry. Of particular interest was the conversion of translational energy of a polyatomic ion into internal energy during a collision. Out of these experiments grew the technique of angle resolved mass spectrometry (ARMS) in which the scattering angle was selected as a route to selecting more or less energetic ions. Other work of fundamental interest concerned the consequences of collisions of polyatomic ions with surfaces in the 10-10,000 eV energy range. Cooks and his group have worked almost alone on this topic over the past five years, delineating the phenomena which occur. They have demonstrated its potential applicability in both surface and molecular characterization. A related topic concerns the characterization of organic compounds on surfaces. Cooks was one of the pioneers of secondary ion mass spectrometry (SIMS), a technique which allows the analysis of thermally labile, non-volatile compounds by mass spectrometry. One result of this work was the extension of mass spectrometry from organic to biological compounds. For mass spectrometry to develop into a major tool in the biological sciences it is necessary that the mass range of mass spectrometers be extended. Working with a new ion trap instrument, the Cooks group recently extended the mass range 100-fold, demonstrating the ability to record mass spectra to about 105 Dalton. The consequences of these capabilities are expect d to include biopolymer and especially peptide and modified DNA sequencing strategies which improve on present methods. Recent work in Cooks' laboratory focused on the ion trap mass spectrometer which uses electric fields to contain about 108 ions in a small volume. The ions trapped can be selected by their mass-to-charge ratios, irradiated with laser beams to study their photochemistry, translationally excited and dissociated and then re- analyzed in an MS/MS experiment. Recently a total sample of 2 attomoles (2 x 10-18 moles) of a small peptide has been shown to be sufficient to perform molecular weight measurements. Professor Cooks has significantly contributed in making mass spectrometry one of the pre-eminent methods of chemical analysis. It is for this contribution that Purdue University awarded Professor Cooks the Herbert Newby McCoy Award in 1990.