Reactivity of hydrophobic nitroxides in lipid bilayers

• Published in: Colloids and surfaces 1990, Vol.45, p.303-312
• Main Authors: Schara, M., Pečar, S., Svetek, J.
• Format: Article
• Language: English
• Subjects: Chemistry; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry
• ISSN: 0166-6622; 1873-4340
• DOI: 10.1016/0166-6622(90)80032-Y

Positional displacements of specific groups on lipophilic molecules in membranes with respect to the lipid bilayer surface were used to describe the reduction of doxylmethyl palmitates by ascorbate in liposomes and erythrocytes. These highly lipophilic molecules are predominantly dissolved in the lipid bilayers of liposome and erythrocyte dispersions. Therefore the reaction rates reflect the probability of finding the nitroxides within the outer polar region of the membrane, which is accessible by ascorbate. A decrease of electron paramagnetic resonance intensity of a series of methyl esters of doxylpalmitic acids with different positions of nitroxides along the acyl chain was studied during the kinetics of ascorbate reduction. Models were introduced to evaluate the amplitudes of longitudinal positional motions of the nitroxides with respect to their equilibrium position within the membrane.