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Tutorial For Size Distribution Analysis

This page describes an example for the analysis of sedimentation velocity data by Lamm equation distributions c(s).  Other pages contain introduction in the theory and information on how to use the Sedfit menu for c(s), and both are recommended for reading before proceeding with this tutorial.  Goal of this page is to provide a data set that can be downloaded, and give step-by-step instructions with screenshots on how to use Sedfit to do a c(s) analysis, which can be reproduced on your own computer.

For more detailed and up-to-date information, see the book

which as a chapter dedicated to practical data analysis questions.

update October 2018: For information on the new nonideal c(s), see the step-by-step protocols at

 For tutorials, can also consult the step-by-step protocol (this is using fluorescence optical data, but the data analysis applies equally to other optical systems).

The present tutorial contains several parts:

1) Experimental considerations (and location to download the data files of the BSA example)

2) Loading the data and preparing the analysis

3) Selecting the model and setting the initial values for the parameters

4) Interpreting and refining the results

5) Displaying and exporting the distribution

6) Summary and Conclusion

It also has two parts for related analyses in an Appendix:

7) Conversion of a c(s) distribution to a molar mass distribution c(M)

8) Size-and-Shape distribution c(s,M) and general c(s,*)

9) The use of the apparent sedimentation coefficient distribution ls-g*(s)

Because of the many screenshots, the tutorial would be too large to download as a single web page.  Therefore, it is organized in several sections.  However, the different parts are strictly building onto each other and cannot be read independently.

A second example of a data analysis with Sedfit is shown here.  It does not have the level of detail given in the tutorial, but the data can be downloaded and the analysis can be reproduced and compared.  

New in version 8.7:  Please note that corrections for solvent compressibility are now available.  For using those, please read the specific instructions for this Sedfit mode. They have not been included in the above tutorial, yet.  For the c(s) distribution with solvent compressibility, this will mean that the s-values are corrected to standard conditions (water 20C), and that the buffer viscosity and density in the input boxes will refer to standard conditions. 

Note for version 11.0 (December 2007) and later: the user interface has been extended to include new functionalities, as indicated in the different steps.

Other tutorial sites:

Solving the Lamm equation

Systematic noise analysis

Introduction in size-distribution analysis

Introduction to ls-g*(s)

van Holde-Weischet analysis

Compressibility of water and organic solvents

Sedimentation in dynamic self-forming density gradients