title: The interaction of cations with lipopolysaccharide from Escherichia coli C as shown by measurement of binding constants and aggregation reactions.
abstract: Lipopolysaccharide from Escherichia coli C interacts with polyvalent cations at low ionic strength at more than one site. The first site has high affinity with a KD value of 10(-8) M for Ca2+ and even stronger binding for [(NH3)5CoNH2Co(NH3)5]5+ and La3+. The high-affinity site for the latter cations is beyond the sensitivity of the assay method. The second, low-affinity, site for bivalent cations has a Km of 10(-3) M, whereas, for tervalent and quinquevalent metal cations and spermine and hexacyclen (1,4,7,10,13,16-hexa-azacyclo-octadecane), this constant has a value of 10(-5) M. Binding of cations to the high-affinity site does not alter the aggregation state of the lipopolysaccharide, but combination with the low-affinity site gives particles twice the size of those of the sodium salt. Very high Ca2+ concentrations (30 mM) give particles eight times the size of those of the sodium salt.
authors.affiliation: Virus Reference Laboratory, Central Public Health Laboratory, London.
authors.forename: A M
authors.initials: AM
authors.lastname: Field
authors.forename: E
authors.initials: E
authors.lastname: Rowatt
authors.forename: R J
authors.initials: RJ
authors.lastname: Williams
mesh_terms: D001150:Arsenazo III; D001665:Binding Sites; D002412:Cations; D004926:Escherichia coli / Q000502:physiology*; D008070:Lipopolysaccharides / Q000502:physiology*; D008854:Microscopy, Electron; D013053:Spectrophotometry
chemical_list: D002412:Cations; D008070:Lipopolysaccharides; D001150:Arsenazo III