I'm checking the interaction between Human Complement Factor H and HRG (Histidine rich glycoprotein). The buffer I am currently using is 50 mM NaCl and 50mM Tris, pH 7.4. First results looked dodgy so I've run a blank control (buffer titrated into buffer) and it showed first exothermic and then endothermic reaction. Buffer was double filtered. Should I change the buffer for something else or increase the concentration of my proteins?