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PURPOSE: Cholesterol is a major lipid constituent of biological membranes which could be included in cyclodextrin (CD) cavities. Solubilization and cell extraction of cholesterol have been previously performed in order to study its interaction with beta-CD and methylated beta-derivatives notably. The present work aims at confirming the formation of inclusion complexes between these CDs and cholesterol in order to understand their solubilization and cell extraction capacities. METHODS: In this context, liquid-state NMR spectroscopy (1H NMR studies and ROESY experiments) as well as theoretical studies (molecular modeling) have been performed. RESULTS: Rather than preferential conformations, the spectroscopic studies showed us the possible interactions between cholesterol and dimethyl-beta-CD, trimethyl-beta-CD, randomly methylated beta-CD or Crysmeb®. Weak interactions were detected using the latter one, confirming the advantage of the low substitution to decrease membrane loss of integrity and cytotoxicity. Molecular modeling studies should be used to determine which stoichiometry and conformations are energically more favorable. The semi-empirical AM1 level was used to investigate both 1:1 and 1:2 complexes whereas 1:1 complexes were also studied using minimal or double zeta basis sets. Four conformations for each 1:2 complexes have been envisaged and studied for the methylated CDs. CONCLUSIONS: These studies allowed us to confirm the interactions between cholesterol and beta-CDs especially the methylated derivatives.

RGD peptides are used in biomaterials science for surface modifications with a view to elicit selective cellular responses. Our objective is to replace peptides by small peptidomimetics acting similarly. We designed novel molecules targeting αvβ3integrin and featuring spacer-arms (for surface grafting), which do not disturb the biological activity, from (l) N-(3-(trifluoromethyl)benzenesulfonyl) tyrosine used as scaffold. Various Arg-mimics were fixed on the phenol function, and the ortho position was used for the coupling of OEG spacers. All peptidomimetics were active in the nM range in a binding test toward human αvβ3integrin (IC50= 0.1 to 1.7 nM) and selective versus platelet integrin αIIbβ3. Selected compounds revealed excellent ability to inhibit bone cells adhesion on vitronectin. Modeling and docking studies were performed for comparing the most active RGD peptidomimetic to cilengitide, i.e., cyclo-[RGDfN(Me)V]−. Lastly, the adhesion of endothelial cells on a cultivation support grafted with RGD peptidomimetics was significantly improved. [ABSTRACT FROM AUTHOR]

The energies of the fundamental and several excited states of tetrapeptide radical cations were determined at the outer valence Green's function (OVGF) level, at three geometries corresponding to the lowest energy conformations:  two for the neutral and one for the cation. The conformations were optimized at the density functional theory level within the B3LYP framework. It was found that, from a purely energetic point of view, a charge initially created on the tyrosine chromophore could migrate without any geometrical change and without further activation once the excited electronic state of the ionized chromophore was formed. This migration could reach the NH2terminus for the neutral conformations but should stop at the adjacent peptide link for the cation conformation. These results stress the probable influence of the electronic coupling between the states rather than the existence of a barrier on the charge pathway to explain the difference between the peptides in the charge-transfer process leading to the loss of an iminium NH2CHRcation. The dissociation energy of the asymptote related to the formation of this NH2terminus iminium cation was calculated for few species and it appears that the excess energy available for dissociation is significant when starting from the lowest energy conformations of the neutral or the cation, provided that the charge transfer is effective. It was also found that the amino acids did not conserve their energetic properties and their zero order energy levels turned to a complete new energetic scheme corresponding to the conformation of the peptide. [ABSTRACT FROM AUTHOR]