Calcium ions induce collapse of charged O-side chains of lipopolysaccharides from Pseudomonas aeruginosa.
Lipopolysaccharide (LPS) monolayers deposited on planar, hydrophobic substrates were used as a defined model of outer membranes of Pseudomonas aeruginosa strain dps 89. To investigate the influence of ions on the (out-of-plane) monolayer structure, we measured specular X-ray reflectivity at high energy (22 keV) to ensure transmission through water. Electron density profiles were reconstructed from the reflectivity curves, and they indicate that the presence of Ca(2+) ions induces a significant change in the conformation of the charged polysaccharide head groups (O-side chains). Monte Carlo simulations based on a minimal computer model of LPS molecules allow for the modelling of 100 or more molecules over 10(-3) s and theoretically explained the tendency found by experiments.
Schneck
Emanuel
E
Biophysical Chemistry II, Institute of Physical Chemistry and BIOQUANT, University of Heidelberg, 69120 Heidelberg, Germany.
Papp-Szabo
Erzsebet
E
Quinn
Bonnie E
BE
Konovalov
Oleg V
OV
Beveridge
Terry J
TJ
Pink
David A
DA
Tanaka
Motomu
M
D002118:Calcium / Q000737:chemistry*; D007477:Ions; D008070:Lipopolysaccharides / Q000737:chemistry*; D008968:Molecular Conformation; D011550:Pseudomonas aeruginosa / Q000378:metabolism*; D014961:X-Ray Diffraction / Q000379:methods*
D007477:Ions; D008070:Lipopolysaccharides; D002118:Calcium