Ab initio study of hydroxyl torsional barriers and molecular properties of mono- and di-iodotyrosine.

Phenol rings with one or two iodine atoms bonded to ortho carbons are the essential organic source of iodine for living organisms. The salvage of this halogen fundamental for a variety of biological functions is accomplished through enzymatic processes that rely on recognition of mono- and di-iodotyrosine (MIT and DIT, respectively). Ab initio quantum calculations are used to investigate molecular properties of MIT and DIT associated with their recognition by cognate proteins. Energies, electron density properties, atomic charges, and electrostatic potentials are analyzed in relation with the presence of one or two iodine atoms and internal rotation of hydroxyl hydrogen. The formation of an intramolecular hydrogen bond at some conformations has little effect on the properties that might affect the recognition and further deiodination of MIT and DIT. Polarizability of iodine and the reactive nature of iodinated tyrosines as nucleophilic targets are the essential features revealed in this work.