Calculation of NMR relaxation, covolume, and scattering related propertiesof bead models using the SOLPRO computer program

The hydrodynamic properties of macromolecules and bioparticles, represented by bead models, can be calculated using methods implemented in the compute r routine HYDRO. Recently, a new computer routine, SOLPRO, has been present ed for the calculation of various SOLution PROperties. These include (1) ti me-dependent electro-optic and spectroscopic properties related to rotation al diffusion, (2) non-dynamic properties like scattering curves, and (3) di mensionless quantities that combine two or more solution properties in a fo rm which depends on the shape of the macromolecule but not on its size. In the present work we describe the inclusion of more of those types of proper ties in a new version of SOLPRO. Particularly, we describe the calculation of relaxation rates in nuclear magnetic resonance (NMR). For dipolar coupli ng, given the direction of the dipole the program calculates values of the spectral density, from which the NMR relaxation times can be obtained. We a lso consider scattering-related properties, namely the distribution of dist ances for the bead model, which is directly related to the angular dependen ce of scattered intensity, and the particle's longest distance. We have dev ised and programmed a procedure to calculate the covolume of the bead model , related to the second virial coefficient and, in general, to the concentr ation dependence of solution properties. Various shape-dependent dimensionl ess quantities involving the covolume are calculated. In this paper we also discuss some aspects, namely bead overlapping and hydration, that are not explicitely included in SOLPRO, but should be considered by the user.