EFFECT OF DAPTOMYCIN ON THE BAROTROPIC BEHAVIOR OF DIOLEOYLPHOSPHATIDYLGLYCEROL - AN INFRARED SPECTROSCOPIC INVESTIGATION

According to our infrared spectra, the pressure-induced liquid-crystal to gel transition of dioleoylphosphatidylglycerol (DOPG) involves a c onformational change making the glycerol C-sn-1-C-sn-2 bond more paral lel to the bilayer surface and resulting in increased carbonyl groups hydrogen bonding. This conformational change allows a more compact pac king of the cis unsaturated acyl chains. The lipopeptide daptomycin, a t lipid/daptomycin molar ratios of 4:1, impedes the DOPG conformationa l change and induces an increase of the transition pressure from 5.5 ( pure lipid) to 6.8 kbar and a higher disorder in the gel slate. The an alogue (LY298862) of daptomycin containing a myristoyl instead of a de canoyl chain shifts the phase transition to 7.8 kbar at the same molar ratio and reduces more efficiently the lipid conformational change. T he lipopeptide hydrocarbon chain length is thus a critical parameter i n the modulation of the physical effects of this type of compounds, of ten used as antibiotics.