MSTARA and MSTARI: interactive PC algorithms for simple, model independent evaluation of sedimentation equilibrium data

Abstract

This paper describes a program available for PC's for the evaluation of molecular weights from sedimentation equilibrium. This program, in its two forms – MSTARA for absorption optical records and MSTARI for interference optical records – requires no prior assumption of the nature of the system (ideal, non-ideal, monodisperse, polydisperse, self-associating etc.) and takes into consideration the whole solute distribution (i.e. from solution meniscus to cell base) in the ultracentrifuge cell rather than just a selected data-set. MSTARA or MSTARI are therefore recommended as a first analysis programme of sedimentation equilibrium data coming off an absorption or interference based analytical ultracentrifuge. These programmes are therefore particularly well suited if heterogeneity (polydispersity or interaction phenomena) or non-ideality is suspected. Their use is demonstrated for a series of data-set types (ideal, non-ideal, polydisperse and self-associating). Although MSTARA and MSTARI are model independent, they provide the basis for more detailed analysis of interactions, polydisperse distributions or non-ideality via easy export of ASCII datafiles to model dependent routines.