Electronic Structure and Magnetic Circular Dichroism Studies of Proton Transfer by Histidine

Abstract

Proton transport in many known enzymatic reactions is accompanied by the participation of a histidyl residue in the active site. A useful text on enzymes (Gray, 1971) lists such cases for acetylcholinesterase, alpha-amylase, aspartate aminotransferase, carbonic anhydrase, carboxypeptidase, chymotripsin, creatinine kinase, fructose-diphosphate aldolase, glucose-phosphate isomerase, glyceraldehyde-3-phosphate NAD oxidoreductase, ketosteroid delta-4 delta-5 isomerase, papain, phosphoglucomutase, ribonuclease, subtilopeptidase-A and trypsin Because proton transfer is critical in such enzymatic mechanisms and because protons are particles of very low mass, one should ask whether magnetic fields can influence and/or interfere with such processes. To the extent that magnetic effects on biosystems have been documented (Allen, Cleary and Hawkridge, 1989), the next question of where to look for a molecular mechanism brings the histidine proton transfer mechanism under scrutiny. The method of choice in this paper is to use magnetic circular dichroism spectroscopy which measures the chirality induced in the electronic structure of a molecule by immersion in a strong, static magnetic field.KeywordsProton TransferStatic Magnetic FieldMagnetic Circular DichroismMagnetic PerturbationMagnetic Circular Dichroism SpectrumThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.