How can i give a fit "Top" value or "Bottom" value in the the mode of four parameter by using Graphpad? or choose automatically by the default seting of this software ? If some experiment values are beyond 100% of inhibition rate, how to get IC50? Besides, What is the lowest inhibition rate usually tested by the concentration setting? If the lowest inhibition rate is higher than 50%, is it significant for to caculate the IC50 of drug ?