Infrared spectroscopy studies of cation effects on lipopolysaccharides in aqueous solution

Sanjai J. Parikh, Jon Chorover

Research output: Contribution to journalArticlepeer-review

37 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)241-250
Number of pages10
JournalColloids and Surfaces B: Biointerfaces
Issue number2
StatePublished - Apr 1 2007


  • ATR-FTIR spectroscopy
  • Endotoxin
  • LPS
  • Lipid A
  • Polarized FTIR

ASJC Scopus subject areas

  • Biotechnology
  • Surfaces and Interfaces
  • Physical and Theoretical Chemistry
  • Colloid and Surface Chemistry


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