A study of the rates of denaturation of arachin and conarachin II

Abstract The rates of denaturation of arachin and conarachin II with sodium hydroxide and guanidine hydrochloride have been studied. Arachin is more susceptible to denaturation with both reagents. The rates of denaturation of the two proteins with sodium hydroxide or guanidine hydrochloride are decreased by increasing the sodium chloride concentration. Arachin is changed by both denaturants to slowly sedimenting material by way of an intermediate sedimenting component, but no intermediate component has been observed with conarachin II. Whereas the rate of alkaline denaturation of both proteins is very sensitive to temperature changes, with guanidine hydrochloride the rate is not affected appreciably by changes in temperature. This would indicate that an appreciable activation energy is required for the alkaline denaturation. Confirmation of this is seen in that the alkaline denaturation is always completely irreversible whereas with guanidine hydrochloride some reversibility has been observed. Although there was no increase in rate with increase in protein concentration for either protein, in no case did the plot of log concentration vs. time give the straight line graph expected of a reaction which is first order with respect to protein concentration.