Characterization of crystals of an Fab fragment of a murine monoclonal antibody.

Abstract The Fab fragment of an antibody, made against an E2-specific feline infectious peritonitis virus neutralizing antibody, has been crystallized in a form suitable for X-ray diffraction analysis from PEG 4000 using vapor diffusion methods. The Fab fragment crystals diffract to about 2·9 A resolution and are of triclinic space group P 1. Unit cell dimensions, by which the reciprocal lattice can be indexed, are a = 57·16 A , b = 70·85 A , c = 75·81 A , α = 85·11∘ , β = 121·28∘ and γ = 116·33∘. There are two Fab fragments comprising the asymmetric unit of the crystals. The presence of a pseudo-mirror plane in the diffraction pattern suggests the presence of at least an approximate dyad axis relating the two Fab fragments within the asymmetric unit.