This work reports the effects of the bioflavinoids genistein and daidzein on lipid bilayers as determined by volume measurements, X-ray scattering and molecular dynamics simulations. The experimental and simulated total molecular volumes were found to be in outstanding agreement with each other before the addition of genistein and daidzein and also after their addition. Both bioflavinoids inserted into the hydrocarbon region of both DOPC and DiphytanoylPC near the carbonyls of the lipids and both decreased the bilayer thicknesses. The long axes of both bioflavinoids were oriented nearly parallel to the plane of the bilayer with their carbonyl groups preferentially pointed towards the proximal surface. A difference is that daidzein had a solubility limit ~0.14 mole fraction in DOPC (~0.12 mole fraction in DiphytanoylPC) whereas genistein was soluble at least to 0.20 mole fraction in both lipid membranes. Measurements of bending modulus KC and simulation results for area compressibility modulus KA indicate that both bioflavinoids soften bilayers.

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