How many protein do you need for experiment?

The simple answer could be disappointing - from 0.1 to 1 mg both for ITC and DSC. But as almost for all methods it depends on a number of factors. In case of ITC experiments, first of all it depends on enthalpy and constant of binding. The higher enthalpy of binding - the lower concentration can be used for experiment. From the other hand to get good ITC curve and determine all thermodynamic parameters with high accuracy the ratio between concentration and binding constant should varied between 10 and 100.