Got endotherm of protein only and protein+ ligand. Can any body point to the right Equation to use to determine binding constant from DSC unfolding curves?
You can determine by Schellmann's model the thermodynamic association constant of a cosolvent to a protein by DSC and by combining DSC to SAXS/SANS data, too. However you have to perform some global fitting procedure (it is not just one equation) and suppose you have equilibria in solution. You can have a look to my recent paper concerning lysozyme and ethanol ( http://jcp.aip.org/resource/1/jcpsa6/v135/i24/p245103_s1?isAuthorized=no ).
Straume & Freire
Two-dimensional differential scanning calorimetry: Simultaneous resolution of intrinsic protein structural energetics and ligand binding interactions by global linkage analysis
http://www.sciencedirect.com/science/article/pii/000326979290311T
Paper: Study of strong to ultratight protein interactions using differential scanning calorimetry. by Brandts JF, Lin LN. Biochemistry 1990 have all the equations needed. However, I recommend to to determine heat capasity Cp with at least three different pH buffers. You can find procedure and equation also from the paper: http://www.ncbi.nlm.nih.gov/pubmed/14660583
If you are using microcal VP-DSC, the analysis software provides a button where you can enter numbers and it will spit out the binding constant.
Thanks for info! we use TA nano capillary DSC and it does not have this software. However we can try using microcal software for data from nano DSC.
Even if you have just numbers, that should suffice. The button in VP-DSC just does the calculation based on the equation. You don;t need to to do the experiment with microcal instrument. That equation is also mentioned in data analysis manual. If you can get your hands on the data analysis manual you can see the equation in the appendix and use it in a spreedsheet program. If used to be freely available but after GE bought microcal, everything is a a secret.
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