AUC 2022

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Time Derivative Sedimentation Velocity Analysis - A short history
Submitter: Borries Demeler
Authors: Walter Stafford
Corresponding Author: Walter Stafford
Title: Time Derivative Sedimentation Velocity Analysis - A short history
Contribution Type: Full Talk
Selected for Presentation Yes
Abstract: I will start from the initial ideas and proceed through the development of the theory, hardware, optics, data acquisition systems, and software necessary to instantiate the ideas and methods. The time derivate method is based on the simple idea that the derivative of a constant is equal to zero; and therefore, taking the time derivative, or time difference, of a signal will remove all time invariant contributions to the signal. The resulting signal reflects the time varying concentration distribution that contains the information in which we are interested. The largest time invariant contribution to the signal is the constant background that is a function of radius only, resulting from inhomogeneities in various components of the optical systems along with dirt, oil, and fingerprints. I will describe the development of algorithms for model dependent curve fitting to sedimentation velocity data employing numerical solutions to the Lamm equation for both interacting and non-interacting systems These algorithms are based on the methods of René Cohen, and of Jean-Michel Claverie, as implemented by Peter Todd and Rudy Haschemeyer in their non-linear least squares curve fitting procedures, and on methods developed by David Cox in the 1980s. Since the late 1990s, when these curve fitting techniques became widely accessible because of the availability more capable desktop computing power, a software package called SEDANAL was developed by me and Peter Sherwood. It included both time derivative, model independent analysis (e.g. DCDT and WDA), and non-linear curve fitting to time difference data of interacting and non-interacting systems. These techniques continue to be developed and recently, over the last ten years, have been directed at highly non-ideal systems such as sedimentation in serum--in collaboration with Jack Correia--and the development of techniques for multi-wavelength analysis of complicated hetero-associating systems and non-interacting mixtures from which both hydrodynamic and spectral information can be derived. The multi- wavelength analytical techniques have been developed in collaboration with Johannes Walter, Max Uttinger, and Simon Wawra in Prof. Wolfgang Peukert's group in Erlangen, Kristian Schilling and Frank Krause at Nanolytics, in Potsdam, and Joe Pearson with Helmut Colfen's group in Konstanz.