John E. Stuehr
Emeritus Professor of Chemistry
216.368.5099 email@example.com Clapp 207
B.S., Western Reserve University, 1957
Ph.D., Western Reserve University, 1961
NIH Fellow, Max Planck Institute, Gottingen, Germany, 1962-63
NIH Career Development Award, 1972-78
CWRU Sigma Xi Research Award, 1972
Professor Stuehr's research interests focus on several areas in rapid kinetics: dynamics of metal complexation reactions, elementary steps in enzymes, and configurational changes in macromolecules. A wide range of rapid kinetic methods are being applied to these problems, including rapid flow for resolution to the millisecond time range as well as the newer relaxation techniques. The latter permit the measurement of kinetic halftimes down to about 10-2 sec. Specific research areas are:
Metal Complex Formation: Professor Stuehr s group is carrying out detailed rate and mechanism studies of labile metal ion (e.g., Ni2+ , Cu2+ , Zn2+ , Mg2+ ) complexation with ligands such as the coenzyme adenosine triphosphate (ATP). In many biological reactions, the coenzyme participates as a metal ion-coenzyme complex (e.g. MgATP). Different reactions often have different metal ion requirements, suggesting differences in structure and binding in the complexes. The group has found dramatic m echanistic differences among different metal ions in their complexation with nucleotides and phosphates. This work is being extended to other nucleotides, dinucleotides, and flavin coenzymes.
Kinetics and Mechanisms of Elementary Steps in Ribonuclease: Among the processes which are being characterized in ribonuclease are enzyme ionization and isomerization phenomena; interactions of the enzyme with metal ions or small molecules; and enzyme-substrate complex formation and subsequent configurational changes.
Kinetics of Conformational Change: Macromolecules undergo reversible conformational changes in solution. Perhaps the most important and interesting of these changes is the helix-to-coil interconversion. The rate at which a helical segment is converted to a coil segment is of great importance to the understanding of dynamical changes in macromolecules, as well as of biological systems. As a model for such systems Professor Stuehr's group is carrying out kinetic measurements of the helix-coil transition in aqueous polypeptides. Conformational changes are easily initiated by changes in the state of ionization of side chain functional groups. Measurements of the time constant for the conversion (typically 10-5 to 10-7 sec) are being correlated with current theoretical models.
All aspects of the research involve dedicated specialized instrumentation. The stopped-flow and temperaturejump devices include sensitive spectrophotometric detection. Information is acquired digitally on a high-speed transient recorder and permanently stored on computer discs. Data processing uses modern non-linear regression techniques. Thus the experimenter has the opportunity to become familiar with current techniques of on-line data acquisition and processing in addition to rapid kinetic spectroscopy.
- A Rapid Kinetic Study of Divalent Metal lon Interactions with Flavin Coenzymes, Inorg. Chim. Acta, 79(B7) , 255 (1983).
- Thermodynamics and Kinetic Study of the Interactions of Ni(II) with FMN and FAD, J. Am. Chem. Soc., 108, 820 (1986).
- A Temperature-Jump Relaxation Study of the Zn(II)-Chlorophenol Red System, Inorg. Chem., 26, 4029 (1988).
- Thermodynamic and Kinetic Study of the Interactions of Ni(II) with NAD and NADP, Inorg. Chem., 29, 1143 (1990).