MTSA--a Matlab program to fit thermal shift data.

Thermal shift analysis is becoming widely used as a method to identify initial hit ligands for inhibitor discovery or to identify ligands that may aid crystallization. The data analysis software provided by the equipment manufacturers or in the public domain is cumbersome to use. We have assessed a number of different approaches to generate a value for the melting temperature (T(m)) and implemented these methods in the program MTSA within the commercial software Matlab to provide an easy-to-use and rapid way to process experimental thermal shift data. The program outputs the T(m), the quality of the fit, and the deviation from a standard value, the thermal shift ΔT(m). Our analysis of these results includes a discussion of some issues with previous publications in this area. We conclude that the most suitable value for T(m) should be taken from the midpoint determined for a curve fitted to the experimental data with a five-parameter equation. In addition, we found that different ranking of ligand binding can be obtained using the different techniques when screening for binding of weak ligands such as fragments. Therefore, the technique should be used with caution for such screening.