The Journal of General Physiology, Vol 19, 339-350,
Copyright © 1935 by The Rockefeller University Press
RELATION OF OXYGEN TENSION AND TEMPERATURE TO THE TIME OF REDUCTION OF CYTOCHROME
T. J. B. Stier 1
1 From the Physiological Laboratory, Cambridge, England, and the Biological Laboratories, Harvard University, Cambridge, Massachusetts
The time for the appearance of the cytochrome C absorption band after shaking a suspension of bakers' yeast with various O2-N2 mixtures was determined at each of six temperatures. At each temperature a linear relation between this interval—called the reduction time—and O2 tension was found. It was shown:
1. That under our experimental conditions, absorption bands of cytochrome were seen when the O2 tension of the suspension was reduced to, or below, a certain pressure which was found to be specific for each temperature (this pressure is provisionally considered to be identical with or very near to the "critical O2 tension" usually found in QOO2-O2-tension relationships);
2. That the x-axis intercept obtained from the reduction time - O2-tension plot gives the value of the "critical" O2 pressure at each temperature;
3. That the O2 tension within the suspension is reduced by the respiratory activity of the yeast cells.
An equation describing these observations is given and is used in calculating rates of O2 consumption from measurements of reduction time of cytochrome. The average difference between the calculated values and the manometric measurements of QOO2 was found to be 6.6 per cent. A rapid optical method of measuring rates of O2 consumption based on the findings of these experiments is proposed for use with cytochrome-containing microorganisms.
Accepted on May 6, 1935
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