The importance of electrostatic interactions in the binding of paraquat to its elicited monoclonal antibody.
In this study the pH-dependent interactions interactions between a paraquat-specific murine monoclonal antibody and two antigens: paraquat (1,1'-dimethyl-4,4'-bipyridinium dichloride), and a p-nitrophenol analogue (1-(N-methyl-4,4'-bipyridinium)-1-(2-hydroxy-5-nitrophenyl)methane dichloride; PQNP) were determined by ELISA. In each case the KAS-pH profile reflected the titration of a single amino acid residue. pK'a values derived from these plots were 8.90 (paraquat) and 8.13 (PQNP). Increasing pH led to a significant increase in the association constant for each antibody complex. A spectrophotometric titration of PQNP in the presence and absence of excess antibody indicated the presence of another charged amino acid residue at the binding site, which could be assigned as a carboxylic acid. From these studies, a model for paraquat-antibody binding has been proposed.
Bowles
M R
MR
University of Queensland, Department of Medicine, Princess Alexandra Hospital, Brisbane, Australia.
Pond
S M
SM
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000937:Antigen-Antibody Reactions; D004797:Enzyme-Linked Immunosorbent Assay; D006863:Hydrogen-Ion Concentration; D007525:Isoelectric Focusing; D007700:Kinetics; D051379:Mice; D010269:Paraquat / Q000031:analogs & derivatives / Q000138:chemical synthesis / Q000276:immunology*; D013057:Spectrum Analysis
D000911:Antibodies, Monoclonal; C066054:1-(N-methyl-4,4'-bipyridinium)-1-(2-hydroxy-5-nitrophenyl)methane; D010269:Paraquat