TY - JOUR
T1 - Infrared spectroscopy studies of cation effects on lipopolysaccharides in aqueous solution
AU - Parikh, Sanjai J.
AU - Chorover, Jon
N1 - Funding Information:
We are grateful to David A. White II for performing the CAC measurements. This research was supported by the National Science Foundation CRAEMS program (Grant CHE-0089156).
PY - 2007/4/1
Y1 - 2007/4/1
N2 - The conformation of amphiphilic lipopolysaccharides (LPS) influences the behavior of free and cell-bound LPS in aqueous environments, including their adhesion to surfaces. Conformational changes in Pseudomonas aeruginosa serotype 10 LPS aggregates resulting from changes in solution pH (3, 6, and 9), ionic strength [I] 1, 10, and 100 mmol L-1, and electrolyte composition (NaCl and CaCl2) were investigated via attenuated total reflectance (ATR) Fourier transform infrared (FTIR) spectroscopy. ATR-FTIR data indicate that LPS forms more stable aggregates in NaCl relative to CaCl2 solutions. Time- and cation-dependent changes in ATR-FTIR data suggest that LPS aggregates are perturbed by Ca2+ complexation at lipid A phosphoryl groups, which leads to reorientation of the lipid A at the surface of a ZnSe ATR internal reflection element (IRE). Polarized ATR-FTIR investigations reveal orientation of LPS dipoles approximately perpendicular to the IRE plane for both Na- and Ca-LPS. The results indicate that changes in solution chemistry strongly impact the conformation, intermolecular and interfacial behavior of LPS in aqueous systems.
AB - The conformation of amphiphilic lipopolysaccharides (LPS) influences the behavior of free and cell-bound LPS in aqueous environments, including their adhesion to surfaces. Conformational changes in Pseudomonas aeruginosa serotype 10 LPS aggregates resulting from changes in solution pH (3, 6, and 9), ionic strength [I] 1, 10, and 100 mmol L-1, and electrolyte composition (NaCl and CaCl2) were investigated via attenuated total reflectance (ATR) Fourier transform infrared (FTIR) spectroscopy. ATR-FTIR data indicate that LPS forms more stable aggregates in NaCl relative to CaCl2 solutions. Time- and cation-dependent changes in ATR-FTIR data suggest that LPS aggregates are perturbed by Ca2+ complexation at lipid A phosphoryl groups, which leads to reorientation of the lipid A at the surface of a ZnSe ATR internal reflection element (IRE). Polarized ATR-FTIR investigations reveal orientation of LPS dipoles approximately perpendicular to the IRE plane for both Na- and Ca-LPS. The results indicate that changes in solution chemistry strongly impact the conformation, intermolecular and interfacial behavior of LPS in aqueous systems.
KW - ATR-FTIR spectroscopy
KW - Endotoxin
KW - LPS
KW - Lipid A
KW - Polarized FTIR
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U2 - 10.1016/j.colsurfb.2006.12.014
DO - 10.1016/j.colsurfb.2006.12.014
M3 - Article
C2 - 17275267
AN - SCOPUS:33847039493
SN - 0927-7765
VL - 55
SP - 241
EP - 250
JO - Colloids and Surfaces B: Biointerfaces
JF - Colloids and Surfaces B: Biointerfaces
IS - 2
ER -