AROMATIC INTERACTIONS IN PROTEINS, DNA AND SYNTHETIC RECEPTORS

Non-covalent interactions between aromatic molecules (pi-pi interactions) play a major role in biological molecular recognition. A simple theoretical model which accounts for the geometric properties of pi-pi interactions is described. The key feature of this model is that it specifically allows for out-of-plane pi-electron density in the calculation of electrostatic interactions. Experimental evidence for the validity of the model comes from studies of the geometric distribution of phenylalanine-phenylalanine interactions in protein X-ray crystal structures. The model has also been used to design a synthetic molecular receptor which recognizes p-benzoquinone using H-bonds and edge-to-face pi-pi interactions. Aromatic stacking interactions provide the crucial link between sequence and three-dimensional structure in double-helical DNA. The pi-pi interaction model has been used to calculate the conformational preferences of all ten DNA base-pair steps and the results provide new insight into the molecular basis of sequence-dependent. DNA structure.