Segmental flexibility in pig immunoglobulin G studied by neutron spin‐echo technique

Abstract

Abstract The dynamic behavior of pig immunoglobulin G in deuterium oxide solutions was investigated by the neutron spin‐echo technique. This novel technique makes it possible to study intramolecular motion without introducing probes into the macromolecule. Using neutron spin‐echo, the effective diffusion coefficient, D eff , was obtained as a function of the transferred momentum, κ. For interpretation of the experimental data, two models were designed, and computed D eff values were compared with experimental data. The rigid T‐shape model was compatible with the experimental data only by assuming an unrealistically high rotational diffusion coefficient, and it was therefore unacceptable. Reasonable agreement with all available experimental data was obtained with a flexible model of immunoglobulin G molecule, which the Fab arms are assumed to wobble around the hinge region within an angle of 50°.