Hi, I think the ligand concentration (250nM) is too low for the titration to reach saturation. To get properly saturated thermogram people sugest to use the ligand concentration 15-20 times higher than the macromolecule. On reducing the the ligand concentration you said you have obtained endothermic thermogram. Have you checked if the dP values are comparable or not? Sometimes when using too low concentrations of both protein and ligand may result in giving this kind of results, since the signals for the binding reactions get over-rided by the noise of the experiment. Running a blank experiment may help you to conclude about this confusion.
Madhuparna. ------------------------------------------ Madhuparna Bose. Senior Research Fellow. Department of Biotechnology. IIT Kharagpur. West Bengal. India. On Mon, Dec 15, 2014 at 11:35 AM, sajid akthar <b_sajid_...@yahoo.co.in> wrote: > > Dear All > > I am running ITC experiment for my protein. At 250 nm Ligand concentration > (protein was 40nm) I was getting exothermic thermogram. But it was not > saturated. I reduced Ligand concentration to 15 nm and checked again. I got > endothermic thermogram. I dont understand why I am getting both endothermic > and exothermic thermogram for same protein and ligand. Can some one explain > > Thank you > > Sajid >
