The exchange seems to happen too fast. I think this is probably due to me not knowing how to map the residue's sasa to the residue's exchange probability. All of the OH seems to run out in 50 - 200 ns depending how I change the function mapping sasa to prob. I don't know if there really is a *right* way to do it. but I suppose I can try and fit Lisa's equilibrium data point and then look for the timescales.