title: Characterization of lipid A profiles from Shigella flexneri variant X lipopolysaccharide.
abstract: BACKGROUND
  In developing countries, Shigella flexneri (Sf) is the major causative agent of the endemic shigellosis (bacillary dysentery) responsible annually for one million fatalities mostly among infants. Lipopolysaccharides (LPSs) are characteristic components of the outer membrane of the overwhelming majority of Gram-negative bacteria. Since lipid A is essential for the viability of the Gram-negative bacteria, it is subject to extensive chemical studies with new analytical techniques.
  
  
  METHODS
  Lipid A was released by mild acid hydrolysis from the lipopolysaccharide which was obtained via the phenol/water extraction, purified and analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and matrix-assisted laser desorption/ionization laser-induced dissociation tandem mass spectrometry (MALDI-LID-MS/MS).
  
  
  RESULTS
  A detailed structural study of the whole lipid A obtained from S. flexneri variant X was carried out for the first time. Thus, we have shown that lipid A is a heterogeneous mixture having different numbers of acylated and phosphoethanolamine groups attached to the diglucosamine backbone. Furthermore, we found in the phenol phase an unusual hepta-acylated lipid A species, although the abundance was very low.
  
  
  CONCLUSIONS
  MALDI-TOF-MS allowed us to unravel the lipid A heterogeneity, which was not previously reported in Sf LPS. It is well known that slight variations of the chemical structure of lipid A may change its biological activity. Thus, the knowledge of the detailed chemical structure represents an essential step for further development of new preventive or therapeutically active compounds.
authors: CIHIDECAR, Departamento de Química Orgánica, Facultad de Cs Exactas y Naturales, Universidad de Buenos Aires, Pabellón II, Cdad. Universitaria, Bs. As., Argentina.
authors: Adriana C
authors: AC
authors: Casabuono
authors: Claudia A
authors: CA
authors: van der Ploeg
authors: Andrés D
authors: AD
authors: Rogé
authors: Susana B
authors: SB
authors: Bruno
authors: Alicia S
authors: AS
authors: Couto
mesh_terms: D008050:Lipid A / Q000737:chemistry*; D008968:Molecular Conformation; D012763:Shigella flexneri / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D053719:Tandem Mass Spectrometry
chemical_list: D008050:Lipid A