Hi Kate,
sorry not to have got back to you sooner on this. The short answer is that this has not changed.
We are going to be putting together some information detailing all the equations, derivations and best practice for titrations. Basically, the assumption is that you are doing the titration in a manner that you keep the protein concentration constant (i.e. using several samples) which makes the fitting independent of the protein concentration - hence you can use the above equation.
If you have done the titration simply by adding your binding partner step-by-step to the same sample tube, then you will need a more complicated equation. Unfortunately, adding additional equations will have to wait until we have finished our current effort to streamline and reorganise some of the program`s code into a new 3.1 release. This will take a few months, but after that it should hopefully become fairly easy to add your own bespoke equations.
Best wishes,
Vicky
