The interaction of lower alcohols with apoB in spin labeled human plasma low density lipoproteins (LDL)

In this study the interaction of alcohol with the macromolecular lipid-protein assembly represented by human plasma low density lipoproteins (LDL) was investigated. The spin label which covalently binds to the side chain amino group of lysines as well as terminal amino groups was attached to the spin labeled apoprotein (apoB) of native LDL in order to observe the protein component in the electron spin resonance (ESR) spectrum. The interaction of different lower alcohols (methanol, ethanol, propanol and butanol) with the spin labeled LDL was studied for two alcohol concentrations (0.3 and 3.0 M). The ESR spectra indicate a decrease of the hyperfine splitting and narrowing of the linewidth upon the action of alcohol that leads to the conclusion that alcohol provokes a change in the apoB conformation. These findings are explained by following the arguments of the phospholipid mediated mechanism of alcohol action, through the modulation of the lipid packing free volume which results in the protein conformational change.