DIFFERENTIAL ACCESSIBILITY OF A HYDROGENATION CATALYST TO ACYL LIPIDS IN THYLAKOID MEMBRANES FROM ATRAZINE-RESISTANT AND ATRAZINE-SUSCEPTIBLE SOLANUM-NIGRUM BIOTYPES

The novel water-soluble palladium complex was used as a probe to test the acyl lipid molecular organization of liposomes and thylakoids originating from triazine-resistant (R) and -susceptible (S) lines of Solanum nigrum. In the present study we report on differing susceptibility of some defined lipid classes towards hydrogenation which shows alterations in the accessibility of the catalyst to lipid substrates within R- compared to S-membranes. Further evidence to support differences in membrane architecture of S- and R-type thylakoids was provided by the lifetime distribution analysis of diphenylhexatriene. The remarkable relative increase of pool size and width of a medium lifetime decay component (4 ns) in S-samples indicates a more diverse molecular organization of this membrane. For an apparently identical lipid class and fatty acid composition and fluidity of thylakoids, the greater environmental heterogeneity of the fluorophore in S-membranes may be attributed to stronger protein-lipid interactions. The possible existence of some intramembraneous domains of acyl lipids, some of which being relatively protected against the catalyst and present only in the atrazine-susceptible biotype, is discussed.