THE ELLIPS SUITE OF MACROMOLECULAR CONFORMATION ALGORITHMS

This paper describes a series of four programmes for the PC based on e llipsoidal representations of macromolecular shape in solution using U niversal shape functions. ELLIPS1 is based on simple ellipsoid of revo lution models (where two of the three axes of the ellipsoid are fixed equal to each other). If the user types in a value for a shape functio n from sedimentation or other types of hydrodynamic measurement, it wi ll return a value for the axial ratio of the ellipsoid. ELLIPS2 is bas ed on the more general triaxial ellipsoid with the removal of the rest riction of two equal axes. The user enters the three semi-axial dimens ions of the molecule or the equivalent two axial ratios and ELLIPS2 re turns the value of all the hydrodynamic shape functions. It also works of course for ellipsoids of revolution. ELLIPS3 and ELLIPS4 do the re verse of ELLIPS2, that is they both provide a method for the unique ev aluation of the triaxial dimensions or axial ratios of a macromolecule (and without having to guess a value for the so-called ''hydration'') after entering at least three pieces of hydrodynamic information: ELL IPS3 requires EITHER the intrinsic viscosity with the second virial co efficient (from sedimentation equilibrium, light scattering or osmomet ry) and the radius of gyration (from light or x-ray scattering) OR the intrinsic viscosity with the concentration dependence term for the se dimentation coefficient and the (harmonic mean) rotational relaxation time from fluorescence depolarisation measurements. ELLIPS4 evaluates the tri-axial shape of a macromolecule from electro-optic decay based Universal shape functions using another Universal shape function as a constraint in the extraction of the decay constants.