FREE-RADICAL REACTIONS OF MTDQ AND ITS EFFECT ON BIOLOGICAL MEMBRANE

The effect of methylene-bis-2,2,4-trimethyl-1,2-dihydroquinoline (MTDQ ) and its water soluble species (MTDQ-DA) was studied in biological me mbrane and model systems using EPR spectroscopy for detecting molecula r motion and radical formation., Both compounds influenced the rotatio nal mobility of maleimide spin labels attached to proteins of the nerv e membrane: the addition of MTDQ or MTDQ-DA induced an increase of the rigidity of the membrane in the environment of the attaching sites. T he reaction of MTDQ-DA with hydroxyl and superoxide free radicals show ed that this compound was also a competitive OH and superoxide free ra dical scavenger. The reaction rate constant of the formation of MTDQ-D A free radical was k = (4.0 +/- 0.5).10(9) M-(1)s-(1) in the hydroxyl free radical generating system. Simulation of EPR spectra supported th at MTDQ-DA free radical was very likely a stable nitroxide free radica l.