# General Information on Sednterp

Studies of the structures of macromolecules and their complexes are often aided by thermodynamic and hydrodynamic data available from analytical ultracentrifugation. These techniques are amongst the most versatile, rigorous and accurate for estimating useful physical parameters for a wide range of chemical systems. The equations describing sedimentation are derived from first principles. (Ref. 1 2 3) All terms in the mathematical equations that describe sedimentation behavior are either readily and accurately estimable (Ref. 4 5) or experimentally determinable. (Ref. 6 7) The quantity and quality of the information furnished is great given the relatively small effort needed to perform the experiments. The sheer number of calculations and their inter-relations, however, can seem overwhelming to the non-expert. For the full power of analytical sedimentation to be realized it is necessary for many of the routine calculations to be automated.

The use of appropriate polynomial functions to represent tabulated data permits the construction of a program that uses readily available experimental parameters (temperature, buffer composition, etc.) in the computations needed for the interpretation of analytical sedimentation data. Proper design of the program permits the maximum interpretation of data while requiring only a minimum amount of experimental observations. At the same time, those calculations which cannot be made with certainty should not be performed, thus preventing over interpretation of data. The program should is designed so that user-supplied information may always takes precedence in calculations. Thus, as more experimental data is available, more rigorous interpretations may be made.

Sednterp stores the basic physical data and the fitted coefficients for interpretations in the phyconst database file. Storing all of this information in a single file helps in the program set up and in the updating of the algorithms. Likewise, information entered into the program is stored in a single Microsoft Access database allowing users to compile reports and make use of the data in programs other than Sednterp. All computations are carried out using 7-digit precision.