BACKWARD BINDING AND OTHER STRUCTURAL SURPRISES

From simple to highly complex molecules, examples are cited of 'backwa rd' or retro-binding. In some cases, symmetry dictates the directions observed and in cases not treated here, statistical disorder reveals a veraged forward/backward binding. In most of the cases found, both the receptor and the ligand(s) are asymmetric, so local interactions dict ate the preferred binding mode. A general rationale is presented to ex plain some of these observations and a hypothesis derived from this re view can be tested experimentally.