THE ACTION OF BETA- AND GAMMA-DINITROPHENOL AND OF THE MONONITROPHENOLS ON YEAST RESPIRATION

¹ Department of Physiology, Stanford University

1. It is shown that beta- and gamma-DNP, as well as p- and m-nitrophenol will stimulate yeast respiration. O-nitrophenol was practically inactive in this respect. In all cases the free acid or undissociated form appears to be the active agent.

2. In the case of each of the active drugs a sufficient increase in the undissociated form caused by a decrease in pH resulted in an inhibition of respiration. Partial recovery occurred on restoration of the original pH level.

3. Percentage stimulation of respiration by the active compounds was markedly greater in the absence of glucose, although the presence of glucose caused no shift in optimal dosage.

4. The position of the compounds in order of capacity to stimulate yeast respiration is changed by the presence of glucose. In phosphate buffer the series in order of decreasing activity is p-nitrophenol, m-nitrophenol, alpha-DNP, meta-DNP, while in glucose phosphate the order is p-nitrophenol, alpha-DNP, beta-DNA, meta-nitrophenol.

5. A basis for the comparison of physiological activity of these nitrated phenols from several points of view is developed.