Question

In a gel filtration experiment, Be of unknown protein is 22mL while blue dextran is eluted in 8mL. The total volume gel in the column is 15mL. Calculate distribution/partition coefficient of the unknown protein. What is the significance of calculated distribution coefficient?

Answer 1

Hi

Based on the distribution (partitioning) of the solutes between the mobile and stationary phases, described by a partition coefficient, K:

K = Cs/Cm

where Cs is the solute concentration in the stationary phase and Cm is its concentration in the mobile phase.

For blue dextran

K= 8mL/15mL= 0.533

Now for unknown protein

K= 22mL/15mL= 1.466

In gel filtration, distribution of particular compound between the inner and outer mobile phase is a function of its molecular size, which is represented by distribution coefficient (Kd).The larger molecules which is usually excluded from the gel beads, such molecules will have a Kd value of zero.Certain molecules which is smaller than the pore size of the gel beads enters the pores in the gel matrix hence they will have a Kd value of one.For molecules of intermediate size, they will have Kd value between zero and one.This type of variation in the Kd Values makes it possible to separate molecules in the narrow molecular size range.