Preliminary crystallographic study of the fab fragment of a monoclonal anti-phenylarsonate antibody possessing a major idiotypic specificity

The Fab fragment from a monoclonal anti- p -azophenylarsonate antibody (R9.3) possessing the major cross-reactive idiotype of anti- p -azophenylarsonate antibodies of A/J mice has been crystallized. Two types of crystals were obtained: monoclinic P 2 1 , and tetragonal P 4 1 (or P 4 3 ). Both crystal forms are suitable for high-resolution X-ray analysis. The determination of the three-dimensional structure of R9.3 Fab, together with that of the previously reported crystalline R19.9 Fab, which does not carry the major cross-reactive idiotype, should provide information on the structural basis of idiotypy and antigen-binding specificity of murine anti- p -azophenylarsonate antibodies.