Interactions between bacteriohopane-32,33,34,35-tetrol and liposomal membranes composed of...

The effects of bacteriohopane-32,33,34,35-tetrol (Tetrol), on liposomal membranes composed of dipalmitoyl-phosphatidylcholine (DPPC) were examined and compared with those of bacteriohopane-32-ol (Monol) and cholesterol (Chol) by means of ESR and NMR techniques. 1H-NMR spectra of Tetrol-incorporated DPPC membranes showed splitting of the signals of the choline N-methyl resonance, whereas Monol- and Chol-incorporated membranes showed not splitting of signals above the transition temperature of DPPC. It was suggested that the incorporation of Tetrol affected only the fluidity near the polar head groups of the DPPC membranes. The characteristics of the interactions between Tetrol and membranes are due to the fact that in DPPC bilayers Tetrol and Monol have an inverted orientation contrary to Chol, and that the hydroxy groups of Tetrol suppress the hydrophobic interaction between DPPC molecules whereas the methyl groups of the hopanoid ring promote this.