Photoinactivation of Transfer RNA in the Presence of Acridine Orange

Abstract

Photoinactivation of amino acid-acceptor ability of purified phenylalanine transfer RNA was investigated in the presence of acridine orange under various experimental conditions. The photoinactivation showed unique reaction kinetics: (1) The initial first-order reaction was followed by a reaction with a slower inactivation rate and (2) The relative amounts of the two components depended on dye preparation and concentration of Mg2+ in the system. Several possible mechanisms for these kinetics are discussed. Under the standard conditions the inactivation reaction was found to be independent of light intensity and almost independent of temperature over the range of 5-40°C. The oxygen dependence of the inactivation was rather sharp at low oxygen concentration and then leveled off at about 200 mm Hg. As the pH was raised, the photoinactivation increased gradually, reached a maximum around pH 9, and then decreased.