Structure and elasticity of genistein and daidzein in lipid membranes using X-ray scattering and MD simulations

Lundbaek et al. estimated the ratio of the volume of the lipid and the decane annulus VH to the aqueous volume VA as VH/VA ≈ 0.001. The hydrocarbon/aqueous partition coefficient K gives the ratio of concentration of bioflavinoid in hydrocarbon cH to its aqueous concentration cA as cH/cA=K. Therefore, the ratio of the amount of bioflavinoid in the hydrocarbon region BH to the amount in the aqueous solution BA is BH/BA = K(VH/VA) ≡ x; using the values of the partition coefficients 31 KG ≈ 1100 and KD ≈ 330, the ratio xG is close to 1 for genistein and xD ≈ 1/3 for daidzein. Therefore, for equal total amounts of bioflavinoid added to the gA experimental apparatus, half the genistein resides in the hydrophobic region compared to only 25% of the daidzein. Consequently, the concentration of genistein in the membrane is twice that of daidzein when both are added to the gA experiment in equal amounts. This alone accounts for genistein increasing the gA channel lifetimes twice as much as daidzein.