Geometry, molecular recognition

Once formed, crystals can interact with or adhere to other components. Adhesion can occur directly between crystals to form larger structures which may act as the nidus for further mineralization. Crystals can also interact with metabolites and/or tissues to form such structures. These interactions can and do alter the stereochemical course of crystal assembly, and molecular recognition probably accounts for the striations and intricate geometries adopted by biomineralized structures. The role and composition of metabolites comprising the matrix may be useful to understanding the local and large-scale structure of biominerals. 

A second major area of interest in the design of bioactive molecules is that of the process of molecular recognition which is vital to the formation of the bas-rep complex. The functional groups required for recognition and activity, in their appropriate arrangement in space, or conformation, constitute the pharmacophore of a bas. The study of the possible conformations of a bas may be carried out by molecular mechanics or quantum chemical calculations. Another important factor is the nature and geometry of the receptor site. 

We shall now discuss several recognition processes and describe the main properties of the corresponding molecular receptors. Insofar as receptor molecules have cyclic geometries and contain cavities into which the substrate(s) may bind, the chemistry of molecular recognition also covers macrocyclic chemistry and inclusion chemistry. In view of the extensive literature concerning these domains, the reader is referred to specific monographs, reviews or original papers for more information (see Appendix). 

Because of the multifunctional nature of these photochromic systems, the change in chirality simultaneously triggers the modulation of some particular function, such as fluorescence, molecular recognition, or motion. In most cases, this is the result of a change in the geometry or the electronic properties of the system. 

Geometrical considerations have gained additional importance due to their role in molecular recognition which implies the (molecular) storage and (supramolecular) retrieval of molecular structural information [82], The formation of supramolecular structures necessitates commensurable and compatible geometries of the... 

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