Steps in the correlation of structure with biological action

Abstract

The three best known sources of selectivity that are available for controlling uneconomic cells were outlined at the end of Chapter 1. Before going on to an expanded treatment of these principles, the narrative must pause to review, in this Chapter, the means by which a foreign substance can influence living matter, whether selectively or not. Experience has shown that to neglect this step and proceed straight into discussion of the principles of selectivity is an unreasonably large jump, as a result of which too many independent variables compete for attention at the same time. It seems better to begin with a simple examination of the sources of foreign molecules’ biological activity, which can assume many forms. This activity is, in fact, the primary force, one that can be tamed in the service of Man by application of the principles of selectivity. Ill advised is the investigator who, esteeming his new candidate drug ‘too toxic’ (meaning, really, ‘insufficiently selective’) changes the molecule in a way that extinguishes the toxicity, and thereby loses the force that could have been made selective by thoughtful molecular modification.