2-iminibiotin can also bind to avidin, but it does not change absorbance when it binds to avidin. Competition studies with HABA can be used to study the binding of 2-iminiobiotin. If you mix HABA-avidin and 2-iminobiotin, the [HABA-avidin] will be lower than in the absence of 2-iminobiotin because if the 2-iminobiotin binds HABA cant bind. The decrease in [HABA-avidin] will correspond to a decrease in the absorbance at 500 nm. If I have a tube with a set of [HABA] (e.g. 150 M) and avidin and I add 2-iminobiotin, the [HABA-avidin] should decrease and so should the absorbance at 500 nm. Previously, students have reported that the IC50 of 2-iminobiotin at 150 M HABA is 3.5 times the Kd for HABA. Based on your results and previous students results with 2-iminiobiotin, what would you expect the Kd for the avidin-2-iminobiotin interaction to be? The experimental Kd of HABA is 38.6 and the Rt value is 2.01e-5