Practice question

In gel filtration, distribution coefficient Kd describes accessibility of solute to internal pore volume. It is defined by Ve = Vo + Kd*Vi, where Vo is void volume outside beads and Vi is internal pore volume. A solute completely excluded from pores cannot enter matrix, its elution volume equals Vo, implying Kd equals zero. A fully penetrating small solute exhibits Kd near one. Intermediate molecules show fractional values. Kd is never greater than one in ideal exclusion. Understanding Kd concept helps predict elution behavior, determine whether molecule is above exclusion limit, and evaluate fractionation range of Sephadex or Sepharose matrices.