BEAD-MODEL CALCULATION OF SCATTERING DIAGRAMS - BROWNIAN DYNAMICS STUDY OF FLEXIBILITY IN IMMUNOGLOBULIN IGG1

We consider the calculation of the angular dependence of the scatterin g intensities for models composed of spherical elements of arbitrary s ize, in which some of the spheres may have a size close to that of the whole particle. This minimizes the number of spheres and makes it pos sible to use the same bead models for the prediction of scattering dia grams and hydrodynamics properties. A simple expression is employed fo r the scattering intensity. Particularly, we discuss the validity of s ome versions of the Debye scattering equation for bead models. The met hod could be used for any macromolecule either rigid or with conformat ional variability. The application of the method to a simple model for IgG1 shows that influence of flexibility in the scattering curve is s tronger by the end of the first decade of decay and also shows that th e range of linearity in the Guinier region is not a good method to cha racterize flexibility between arms, because it is very likely that exp erimental errors will hide the small differences between the extreme c ases appreciated in our calculations.