Enhanced resolution of sedimentation coefficient distribution profiles by extrapolation to infinite time.

Sedimentation velocity experiments can be used to identify two or more independent non-interacting macromolecules, which differ in their size by only a few percent. The procedure requires the extrapolation of differential apparent sedimentation coefficient distributions obtained at different running time to t --> infinity and works because it eliminates or greatly reduces diffusion effects. Here, we present an improved time extrapolation function of sedimentation distribution profiles originally presented by Stafford (In: Harding, Rowe, Horton (eds.

An improved approximate solution of the Lamm equation for the simultaneous estimation of sedimentation and diffusion coefficients from sedimentation velocity experiments.

Sedimentation and diffusion coefficients are important parameters to describe size and shape of macromolecules in solution. The data can be obtained from sedimentation velocity experiments by a nonlinear fitting procedure using approximate solutions for the Lamm equation. Here, we present a modification of such a model function that was originally proposed by Fujita [H.

Self-association of adrenodoxin studied by using analytical ultracentrifugation.

The mitochondrial steroid hydroxylase system of vertebrates utilizes adrenodoxin (Adx), a small iron-sulfur cluster protein of about 14 kDa as an electron carrier between a reductase and cytochrome P450. Although the crystal structure of this protein has been elucidated, the solution structure of Adx was discussed contrary in the literature [I.A.

Sedimentation equilibrium: a valuable tool to study homologous and heterogeneous interactions of proteins or proteins and nucleic acids.

We present a short overview of our experience in analyzing the affinity and stoichiometry of self-associating and heterologous interactions by using the sedimentation equilibrium technique. Data acquisition and the fitting procedure employing the computer programs that we have developed, Polymole and Virial, are utilized for obtaining reliable results under ideal as well as non-ideal conditions. Such data derived from biologically important macromolecules find utility in understanding physiological events such as cell regulation.

A new approximate whole boundary solution of the Lamm differential equation for the analysis of sedimentation velocity experiments.

Sedimentation velocity is one of the best-suited physical methods for determining the size and shape of macromolecular substances or their complexes in the range from 1 to several thousand kDa. The moving boundary in sedimentation velocity runs can be described by the Lamm differential equation. Fitting of suitable model functions or solutions of the Lamm equation to the moving boundary is used to obtain directly sedimentation and diffusion coefficients, thus allowing quick determination of size, shape and other parameters of macromolecules.