[Joey-BadAss]

The enzyme HIV-1 reverse transcriptae (HIV-RT) plays a significant role for the HIV virus and is an important drug target. Assume a concentration [E] of 2.00 µM (i.e. 2.00 x 10-6 mol/l) for HIV-RT. Two potential drug molecules, D1 and D2, were identified, which form stable complexes with the HIV-RT.

The dissociation constant of the complex ED1 formed by HIV-RT and the drug D1 is 1.00 nM (i.e. 1.00 x 10-9 mol/l). The dissociation constant of the complex ED2 formed by HIV-RT and the drug D2 is 100 nM (i.e. 1.00 x 10-7 mol/l).

Compute the total concentration of [D1]tot that is needed to bind 90% of the HIV-RT at the given concentration [E]tot.You do NOT have to consider competition betwwen the drugs D1 and D2! They are administered separately.

Compute the total concentration of [D2]tot that is needed to bind 90% of the HIV-RT at the given concentration [E]tot. You do NOT have to consider competition between the drugs D1 and D2! They are administered separately.

I understand how to calculate the concentration when [E]eq = [ED]eq when 50% of [D]eq is bound to HIV-RT because Kdiss = [D]eq and it makes for a simple calculation because [E]eq and [ED]eq cancel out when calculating Kdiss, but what changes mathematically need to be made to account for the change in ratio (90% rather than 50%)? Any help would be appreciated.

[Babcock_Hall]

Can you show your work so far?  Does your analysis take into account the difference between free versus total enzyme and drug?