Multivalent cations binding and exchange in bacterial lipopolysaccharide (Ra-LPS) monolayers: A grazing incidence X-ray fluorescence (GIXF)

The anionic headgroup of lipopolysaccharides (LPS), a key structural and functional component of the Gram-negative bacteria outer membrane, is a main target by cationic antimicrobial actives. Cations are known to influence the biological functions and stability of bacteria, by inducing the rearrangement of the lipid-lipid and lipid-water interaction. However, the mechanisms of how bacterial membrane structural integrity and elasticity changes in response to the varying cationic species remain to be fully understood. Understanding interactions between different multivalent cations and cationic species with LPS is critically important to antibiotic mechanisms and antimicrobial agent design. Here, building on our previous results, we propose a grazing incidence X-ray fluorescence (GIXF) study to investigate the cations (K+, Ca2+ and La3+) binding and exchange in bacterial lipopolysaccharide (E. coli EH100 Ra mutant) monolayers at the air-water interface.