Optimal data analysis using transmitted light intensities in analytical ultracentrifuge

Abstract

This chapter describes the optimal data analysis, using transmitted light intensities, in analytical ultracentrifuge. Analytical ultracentrifugation machines, such as the Beckman XL-A, may be equipped with absorbance optics that is essentially a dual-beam spectrophotometer, with a xenon lamp and a monochromator. To investigate the state of the solution, solute behavior models are assumed and corresponding mathematical models for the expected concentration profiles are written. The suitability of the assumed models is then tested by attempting to curve fit the mathematical models to the collected absorbance data. The chapter provides assumptions for the correct model and the adequate data points are: (1) the data are independent of each other, (2) there is no other systematic error, and (3) the noise probability distribution is Gaussian. Usually, quantities, such as molecular masses and association constants or sedimentation and diffusion coefficients, are used as the fitting parameters, for modeling sedimentation equilibrium or velocity data, respectively.