Contains a report on a research project.National Institutes of Health (Grant RG-7803

Hammes, G. G.

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II. BIOPHYSICAL CHEMISTRY*Prof. G. G. HammesDr. S. R. MillerRESEARCH OBJECTIVES AND PRELIMINARY STUDIESThis project is concerned with the elucidation of the mechanism of physiologicallyimportant reactions, primarily through the use of kinetic methods. Very fast reactionsinvolving purified enzymes and simpler model systems will be investigated with the useof several different techniques.A stopped-flow apparatus1 permits the study of reactions occurring in times as fastas milliseconds. This method simply involves rapid mixing of the reactants in a spe-cially designed chamber and observation of the mixed solution after the flow has beenstopped suddenly. The reaction progress is followed through changes either in opticalabsorption or optical rotation.Reactions occurring in even shorter times will be investigated by utilizingrecently developed relaxation techniques.2,3 The principle of these methods isto disturb chemical equilibria by rapidly changing some external parameter (e. g.,temperature, pressure) and studying the subsequent re-establishment of equi-librium. A temperature-jump apparatus, which raises the temperature of areaction mixture 8°C in approximately 5 sec, has been constructed. This tem-perature jump is accomplished by charging a condenser to 30,000 volts andthen discharging it rapidly through the reaction mixture. Changes in opticalabsorption and rotation are followed with photomultipliers and associated elec-tronic equipment.-9The accessible time scale can be extended to 10 sec by measurement ofultrasonic attenuation in equilibrium reaction mixtures. The ultrasonic wave actsas a pressure wave in aqueous solution, and thus perturbs pressure-dependentchemical equilibria. The result is the occurrence of maxima in the attenuationat frequencies that are related in a known way to the formal rate constants ofa given mechanism.These techniques will permit the study of elementary steps in chemical reactions,and thus provide some details of the molecular mechanism. Also, rates of fast con-formational changes in macromolecules can be measured and related to chemical proc-esses. Preliminary experiments have already been carried out and the results will bepresented in a future report.G. G. HammesThis project is supported in part by the National Institutes of Health (GrantRG-7803).(II. BIOPHYSICAL CHEMISTRY)References1. B. Chance and V. Legallais, Discussions Faraday Soc. 17, 125 (1954).2. M. Eigen, Z. Elektrochem. 64, 115 (1960).3. L. De Maeyer, Z. Elektrochem. 64, 65 (1960).

Biophysical Chemistry

Contains research objectives.National Institutes of Health (Grant RG-7803

V. BIOPHYSICAL CHEMISTRYProf. G. G. HammesDr. J. J. BurkeRESEARCH OBJECTIVESIn recent years, considerable effort has been expended in the elucidation of biochem-ical mechanisms by utilizing physical chemical techniques. This project, while we arestill making use of general physical chemical techniques, is primarily concerned withkinetic studies of chemical reactions of biochemical interest. Techniques have recentlybeen developed which permit the study of chemical reactions with half times as short as-10 15 X 1010 sec. The advantage of being able to carry out kinetic studies over an extendedtime range is that the entire course of a chemical reaction can be observed. Since reac-tion intermediates are directly detected, detailed chemical mechanisms can be obtained.In order to better understand complex biological reactions, the behavior of somesimpler model systems is being investigated. This work includes studies of the inter-actions of metal ions with amino acids, peptides, and polymers in an effort to try andunderstand the role of metal ions in enzyme catalysis. Also, since macromoleculesare of extreme importance in biological systems, chemical processes involving simplepolymers, polypeptides, proteins, and polynucleotides are being examined, particularlywith regard to possible fast conformational changes.In addition to model systems, several enzymatic systems are being studied. Fastreaction techniques have already yielded a detailed mechanism for one enzyme system 3and results for other systems will be available soon. Also, the catalytic role of themacromolecule is being explored.By coupling kinetic studies with known information about molecular structures, itultimately should be possible to understand enzymatic mechanisms on a molecular basis.G. G. HammesReferences1. G. G. Hammes, Quarterly Progress Report No. 65, Research Laboratory ofElectronics, M.I.T., April 15, 1962, p. 5.2. G. G. Hammes and J. I. Steinfeld, Relaxation spectra of some Ni(II) and Co(II)complexes, J. Am. Chem. Soc. (in press).3. G. G. Hammes and P. Fasella, A kinetic study of glutamic-aspartic transamin-ase, J. Am. Chem. Soc. (in press).This project is supported in part by the National Institutes of Health (GrantRG-7803).QPR No. 68

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Biophysical Chemistry

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