Patent ID: 8778617

Claim:
A method for determining the binding constant of a high affinity compound of interest to proteins comprising the following steps: a) adding the high affinity compound to a two-chamber system, wherein the two chambers are separated by a semipermeable membrane, which is permeable for the high affinity compound of interest, and determining the amount of the high affinity compound of interest in one of the chambers after the distribution equilibrium has been reached, b) adding a sink compound wherein the sink compound is polyvinylpyrrolidone(PVP) or cyclodextrin to either one of the chambers whereby the sink compound can not permeate the membrane, and determining the distribution coefficient of the high affinity compound of interest to the sink compound after the distribution equilibrium has been reached, c) adding a plasma protein to the other chamber used in step b) wherein the high affinity compound of interest and the sink compound have been added, whereby the plasma protein can not permeate the membrane, and determining the distribution coefficient of the high affinity compound of interest to the plasma protein in the presence of a sink compound after the distribution equilibrium has been reached, wherein said plasma protein is serum albumin and d) determining the binding constant of the high affinity compound of interest with the distribution coefficient of steps b) and c).