Biophysical parameters of linoleic acid hydroperoxides as assessed by surface behavior and Fourier Transform Infra-Red spectrometry: possible pertinence to senescence

Hydroperoxidation of linoleic acid (LA) by two major lipoxygenases (LOX) produced octadecanoic trans, cis (Δ 10, 12) 9-hydroperoxide (9 LAHP) and octadecanoic cis, trans (Δ, 9, 11) 13-hydroperoxide (13, LAHP). The effect of hydroperoxidation on surface tension-related parameters of simulated monolayer membranes was studied. Langmuir-Blodgett isotherms demonstrated that hydroperoxidation of LA markedly reduces molecular area, and hence increases monolayer rigidity. The reduction in the surface area of 13 LAHP was more pronounced than that of 9 LAHP. Surface tension and Contact Angle measurements demonstrated a similar effect. However, in contrast to the molecular area data, both HP species behaved similarly in that as compared to the unoxidized LA, they both increased Contact angles to the same extent. Fourier-Transform Infra-Red studies indicated that 13 LAHP undergoes non-enzymatic cyclization, and hence molecular area reduction. The results described are discussed in terms of membrane senescence and possible relevance to plant prostaglandin-like compounds of the jasmonate group.