calculation of KD value and problem in reproducing the literature value

1.) does anybody know any formula or method through that we can find the calculate KD value from IC5
2.) I am having trouble reproducing the literature value on my T200 system. KD value what i am getting from interaction analysis its not near about from the reported literature value.
like Neproxen have approx 1uM affinity with HSA but i am getting 40uM or like that and same goes with the warfarin.

1) This is less easy than you would think since many factors are easily overlooked. In general the Cheng Prusoff equation is used to calculate the Ki from the IC50 value.

Some links:
www.sciencesnail.com/science/km-vs-kd-th...ssociation-constants
www.sciencesnail.com/science/the-differe...ic50-and-ec50-values
en.wikipedia.org/wiki/IC50

2) Main problem with comparing values is that they depend on the assay conditions such as buffer composition, pH and temperature. Origin and batch difference can induce some deviation between measurements. In addition, concentration measurements have errors which directly affect the final result. Therefore, careful compare assay conditions if you can find a hint why the difference occurs.

Kind regards
Arnoud