Small-angle neutron scattering and coarse-grained molecular dynamics simulations have been used to determine the structural parameters (bilayer thickness D, polar region thickness D(H), interfacial lateral area of the unit cell A(UC) and alcohol partial interfacial area A(CnOH)) of fluid dioleoylphosphatidylcholine:dioleoylphosphatidylserine (PCPS, DOPC:DOPS=24.7mol:mol) bilayers in extruded unilamellar vesicles with incorporated aliphatic alcohols (CnOH, n=8-18 is the even number of carbons in alkyl chain). External ((2))H(2)O/H(2)O contrast variation experiments revealed that D(H) decreases as a function of alkyl chain length and CnOH:PCPS molar ratio. Using measurements at single 100% ((2))H(2)O contrast we found that (i) D decreases with CnOH:PCPS molar ratio and increases with CnOH chain length (at 0.4 molar ratio); (ii) A(UC) significantly increases already in the presence of shortest CnOH studied (at 0.4 molar ratio), further increase is observed with longer CnOHs and at higher molar ratios; (iii) A(CnOH) of alcohol molecules in PCPS bilayer increases linearly with the alkyl chain length, A(CnOH) obtained for CnOHs with n≤10 corresponds to A(CnOH)≤20Å(2) - a value specific for the crystalline or solid rotator phase of alkanes. All these structural modifications induced by studied CnOHs were reproduced in MD simulations. The computational results give an accurate description of the alcohol effects at the molecular level, explaining the experimental data. The anomaly in A(CnOH) is discussed via the "umbrella" effect described for cholesterol.

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Protein-binding interactions are displacement reactions which have been implicated as the causative mechanisms in many drug-drug interactions. Thus, the aim of presented study was to analyse human serum albumin-binding displacement interaction between two ligands, hypoglycaemic drug gliclazide and widely distributed plant flavonoid quercetin. Fluorescence analysis was used in order to investigate the effect of substances on intrinsic fluorescence of human serum albumin (HSA) and to define binding and quenching properties of ligand-albumin complexes in binary and ternary systems, respectively. Both ligands showed the ability to bind to HSA, although to a different extent. The displacement effect of one ligand from HSA by the other one has been described on the basis of the quenching curves and binding constants comparison for the binary and ternary systems. According to the fluorescence data analysis, gliclazide presents a substance with a lower binding capacity towards HSA compared with quercetin. Results also showed that the presence of quercetin hindered the interaction between HSA and gliclazide, as the binding constant for gliclazide in the ternary system was remarkably lower compared with the binary system. This finding indicates a possibility for an increase in the non-bound fraction of gliclazide which can lead to its more significant hypoglycaemic effect. Additionally, secondary and tertiary structure conformational alterations of HSA upon binding of both ligands were investigated using synchronous fluorescence, circular dichroism and FT-IR. Experimental data were complemented with molecular docking studies. Obtained results provide beneficial information about possible interference upon simultaneous co-administration of the food/dietary supplement and drug.

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Abstract. Lamellar phases composed of fluid dioleoylphosphatidylcholine (DOPC) bilayers containing alkan-1-ols (CnOH, n = 8, 10, 14, 16, 18