Sedimentation Velocity: A Classical Perspective

Here we give an overview of the history of sedimentation velocity analysis focusing on seminal and fundamental contributions that derived from early ultracentrifugation studies. We introduce the concepts of nonequilibrium thermodynamics and outline the derivation of the Svedberg and the Lamm equations and the requirements for including both hydrodynamic and thermodynamic nonideality. We introduce the phenomenological equations for coupled flows as developed from the principles of nonequilibrium or irreversible thermodynamics and derive a form of the Lamm equation that incorporates cross-diffusion coefficients and coupled gradient terms. We give an historical overview of solutions to the Lamm equation including Fujita-MacCosham solutions and Claverie finite-element numerical solutions and discuss the software that have implemented these solutions. We discuss the three major optical systems (absorbance, interference, and fluorescence) and recently developed multiwavelength systems. We also suggest a number of experimental practices and guidelines for optimizing the determination of s and D and discuss the appropriate centerpiece components and their utility. This chapter complements other recent reviews submitted by the authors (Correia, Lyons, Sherwood, & Stafford, 2015; Stafford, 2015) and should be considered an effort to revive the importance of irreversible thermodynamics in the understanding and analysis of sedimentation velocity ultracentrifugation data.