Submitted to: Nonlinear Computer Modeling of Chemical and Biochemical Data
Publication Type: Book / Chapter
Publication Acceptance Date: 5/4/1995
Publication Date: N/A
Interpretive Summary: Book chapter: interpretive summary is not required.
Technical Abstract: Chapter 10 deals with sedimentation of macromolecules and nonlinear regression analysis, which with the recent development of the new analytical ultracentrifuge is at the forefront of scientific research. A derivation of the methods for sedimentation velocity and equilibrium from first principles is presented along with their appropriate equations. For sedimentation velocity data, the use of an integral of a Gaussian line shape is an appropriate model to use for analyzing experimental data of homogeneous particles with nonlinear regression methods. Parameters derived from this analysis will lead to the determination of the molecular weight. Since the integral of a Gaussian function is non-analytic, an equation which approximates this function is presented. For nonhomogeneous systems, the velocity profile can be transformed into its derivative data and the derivative profile can be fit with multiple Gaussian line shapes. The number of component bands determines the number of particles with differing sedimentation coefficients. The corresponding sedimentation coefficients can be calculated from the time dependence of the position from the center of rotation for each of the individual Gaussian bands. The use of nonlinear regression analysis for describing sedimentation equilibrium of macromolecules leads to not only the determination of the molecular weight of a particle, but also to the determination of equilibrium constants for interacting systems. Several examples of proteins in solution are presented as successful applications of this methodology.