SINGLET MOLECULAR OXYGEN QUENCHING BY SATURATED AND UNSATURATED FATTY‐ACIDS AND BY CHOLESTEROL

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Abstract
—: The rate constants of molecular singlet oxygen quenching by saturated and unsaturated fatty‐acids and by cholesterol‐membrane critical components ‐ membrane critical components ‐ have been measured by time resolved detection of the 1270 nm phosphorescence of singlet molecular oxygen [O2(1δg)]. We have determined (i) an increment of 5.7 times 102M‐1s‐1per ‐CH2‐ in C6D6and CD3OD for saturated fatty acids between C4and C20, (ii) an increment of 3 times 104M‐1s‐1per non‐conjugated cu‐double bond for C18unsaturated fatty acids, identical in C6D6and CD3OD, (iii) a lower quenching rate constant by a factor of 2.7 for thetrans‐C16andtrans‐C18as compared to the corresponding cis‐monounsaturated fatty acids, (iv) a rate constant of O2(1δg) quenching by cholesterol of 5.7 times 104M‐ls‐lin benzene. These rate constants are compared to those obtained for other membrane cellular components.