engleski

Classification of auxin related compounds based on similarity of their interaction fields: extension to a new set of compounds.

Auxins are plant hormones governing many biological processes in higher plants such as: cell enlargement and division, differentiation of vascular tissue, apical dominance, root initiation and signaling. Although they were the first type of plant hormone to be identified, little is known about their molecular mechanism . We present a classification of a set of about 50 compounds with measured auxin activities, according to their interaction properties. We have modelled these compounds and the structures can be viewed in a 3D library of auxins using Chemscape CHIME on the Web. Four classes of compounds were defined: strongly active, weakly active with weak antiauxin behaviour, inactive and inhibitory. All compounds were modeled in two low energy conformations, "P" and "T", so as to obtain the best match to the "planar" and "tilted" conformations, respectively, of indole 3-acetic acid. Each set of conformers was superimposed separately using several different alignment schemes. Molecular interaction energy fields were computed for each molecule with 5 different chemical probes and then compared by computing similarity indices. Similarity analysis showed that the classes are on average distinguishable, with better differentiation achieved for the "T" conformers than the "P" conformers. Further, a screening was developed which could distinguish compounds with auxin activity from inactive compounds and most antiauxins using the "T" conformers. The classifications rationalize ambiguities in activity data found in the literature and should be of value in predicting the activities of new plant growth substances and herbicides.

auxins; molecular alignment; molecular interaction field; molecular modeling; QSAR; similarity index

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