Sedfit Version 3.1 This is a software for the analysis of analytical ultracentrifuge data files by direct fitting with numerical solutions of the Lamm equations. Different models are implemented, currently for one or more single ideal components, and for rapid monomer-dimer or monomer-trimer systems of selfassociating species. The known molar mass can be entered as prior knowledge (strongly recommended, where possible), or alternatively diffusion coefficients can be calculated. All systems are implemented with the Claverie method and with a new moving frame of reference finite element method. It allows the algebraic calculation of time-invariant and radial-invariant noise components. Also, it can be used for extracting time-invariant noise contributions from approach-to-equilibrium scans, for correcting the sedimentation equilibrium profiles. The numerical methods are described in the references given below. Finally, it can take experimental scans as initial distributions, which is useful in synthetic boundary experiments. The software runs under Windows 95, and takes XLA or XLI data files. It has a help section, which is accessible by pressing the F1 key while a menu point is highlighted. The careful reading of the help sections is strongly recommended before invoking the menu functions, because in the help file it was attempted to describe in detail all the steps in a given operation, some of which may not be obvious or intuitiv. In the current version, the program is incomplete in several respects (i.e. time-invariant noise decomposition is only avaliable for ideal non-interacting species, global analysis of multiple experiments is only available to a limited extent, etc.), and there can be no guarantee that it doesn't have some other bugs. Also, it contains a few yet undocumented and not entirely debugged features, but these are explicitely marked as such. At the same time, it may already be useful for many applications in its current state. For installation, just put the two files sedfit.exe sedfit.hlp in the same directory. The file xladata.otw is a simple spreadsheet template for Origin, which can be helpful for making graphics by pasting data tables into this spreadsheed from the clipboard, In case problems or bugs are encountered, I would highly appreciate if you could contact me at Peter_Schuck@nih.gov phone: (301) 435-1950 or mail to Peter Schuck NIH, Bldg. 13, Rm 3N17 13 South Drive, Bethesda, MD 20892 Bethesda, October 21, 1998 References (updated 1/18/2000) P. Schuck (1998) Sedimentation analysis of non-interacting and self-associating solutes using numerical solutions to the Lamm equation. Biophysical Journal, 75:1503-1512 P. Schuck, C.E. McPhee, and G.J. Howlett (1998) Determination of Sedimentation Coefficients for Small Peptides. Biophysical Journal, 74:466-474 P. Schuck and B. Demeler. (1999) Direct sedimentation analysis of interference-optical data in analytical ultracentrifugation. Biophysical Journal, 76:2288-2296 P. Schuck (1999) Sedimentation equilibrium analysis of interference optical data by systematic noise decomposition. Analytical Biochemistry 272:199-208 P. Schuck (2000) Size distribution analysis of macromolecules by sedimentation velocity ultracentrifugation and Lamm equation modeling. Biophysical Journal (in press) P. Schuck and P. Rossmanith. Determination of the sedimentation coefficient distribution g*(s) by least-squares boundary modeling. (submitted)