Biophysical study of resin acid effects on phospholipid membrane structure and properties

Hydrophobic resin acids (RAs) are synthesized by conifer trees as part of their defense mechanisms. One of the functions of RAs in plant defense is suggested to be the perturbation of the cellular membrane. However, there is a vast diversity of chemical structures within this class of molecules, and there are no clear correlations to the molecular mechanisms behind the RA's toxicity. In this study we unravel the molecular interactions of the three closely related RAs dehydroabietic acid, neoabietic acid, and the synthetic analogue dichlorodehydroabietic acid with dipalmitoylphosphatidylcholine (DPPC) model membranes and the polar lipid extract of soybeans. The complementarity of the biophysical techniques used (NMR, DLS, NR, DSC, Cryo-TEM) allowed correlating changes at the vesicle level with changes at the molecular level and the co-localization of RAs within DPPC monolayer. Effects on DPPC membranes are correlated with the physical chemical properties of the RA and their toxicity.