Membrane stability in the presence of methacrylate esters.

Bioproduction of polymethyl methacrylate is a fast growing global industry that is limited by cellular toxicity of monomeric methacrylate intermediates to the producer strains. Maintaining high methacrylate concentrations during biofermentation, required by economically viable technologies, challenges bacterial membrane stability and cellular viability. Studying the stability of model lipid membranes in the presence of methacrylates offers unique molecular insights into the mechanisms of methacrylate toxicity, as well as into the fundamental structural bases of membrane assembly. We investigate the structure and stability of model membranes in the presence of high levels of methacrylate esters using solid-state nuclear magnetic resonance (NMR) and small angle X-ray scattering (SAXS). Wideline 31P NMR spectroscopy shows that butyl methacrylate (BMA) can be incorporated into the lipid bilayer at concentrations as high as 75 mol% without significantly disrupting membrane integrity and that lipid acyl chain composition can influence membrane tolerance and ability to accommodate BMA. Using high resolution 13C magic angle spinning (MAS) NMR we show that the presence of 75 mol% BMA lowers the lipid main transition temperature by over 12 degrees, which suggests BMA intercalates between the lipid chains causing uncoupling of collective lipid motions that are typically dominated by chain trans-gauche isomerisation. Potential uncoupling of the bilayer leaflets to accommodate a separate BMA sub-phase was not supported by the SAXS experiments, which showed that membrane thickness remained unchanged even at 80% BMA. Reduced X-ray scattering contrast at the polar/apolar interface suggests BMA localisation in that region between the lipid molecules.