I. Studies in the chemistry of sodium dithionite. II. A pH study of the alpha-chymotrypsin catalysed hydrolysis of methyl-hippurate

Citation

Gordon, Thomas Pascoe (1959) I. Studies in the chemistry of sodium dithionite. II. A pH study of the alpha-chymotrypsin catalysed hydrolysis of methyl-hippurate. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-02012006-154755

Abstract

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Part I. The kinetics of the air oxidation of sodium dithionite in alkaline solution suggest the transfer of an electron from [...] radical-ions, which are in equilibrium with [...] ions, to molecular oxygen in the rate determining step.

Electron paramagnetic resonance experiments confirm the presence of [...] radical-ions in equilibrium with [...] ions in solution.

Electrolytic reduction of sulfurous acid solutions at constant potential in the range -0.7v to -0.9v produces dithionite at constant current efficiency.

Thermal decomposition of dithionite solutions occurs slowly at first, apparently by a free radical mechanism, and then rapidly, indicating a degenerate chain-branching mechanism.

Part II. The results of a pH study of the [alpha]-chymotrypsin catalysed hydrolysis of methyl hippurate at three different added salt concentrations are consistent with the postulation of ionizing groups at the active site of the enzyme with [...] values 6.9 +/- 0.1 and 8.6 +/- 0.1. Important interactions of added salt and hydrogen ion concentrations are not indicated.

Hippuric acid and L-tryptophan are shown to be competitive inhibitors.

The development of a negative charge at or near the active site of the enzyme above pH 8 is confirmed.

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