A tripropargylammonium surfactant with a methacrylate-terminated hydrophobic tail was combined with a bile salt derivative, divinyl benzene (DVB), and a photo-cross-linker above its critical micelle concentration (CMC). Surface-cross-linking with a diazide, surface-functionalization with an azido sugar derivative, and free-radical-core-cross-linking under UV irradiation yielded molecularly imprinted nanoparticles (MINPs) with template-specific binding pockets. The MINPs resemble protein receptors in size, complete watersolubility, and tailored binding sites in their hydrophobic cores. Strong and selective binding of bile salt derivatives was obtained, depending on the cross-linking density of the system. Disciplines Chemistry CommentsReprinted (adapted) ABSTRACT: A tripropargylammonium surfactant with a methacrylate-terminated hydrophobic tail was combined with a bile salt derivative, divinyl benzene (DVB), and a photo-cross-linker above its critical micelle concentration (CMC). Surface-cross-linking with a diazide, surfacefunctionalization with an azido sugar derivative, and freeradical-core-cross-linking under UV irradiation yielded molecularly imprinted nanoparticles (MINPs) with template-specific binding pockets. The MINPs resemble protein receptors in size, complete water-solubility, and tailored binding sites in their hydrophobic cores. Strong and selective binding of bile salt derivatives was obtained, depending on the cross-linking density of the system. M

Multivalent interactions occur frequently between biological entities.1 When strong binding is not achievable with a single receptor-ligand pair, multivalency, or simultaneous binding between multiple receptors and ligands, becomes an effective strategy to enhance the binding. Significant efforts have been devoted in recent years to synthetic multivalent ligands and their interactions with biological hosts.2 Two of the most widely used scaffolds in multivalency are dendrimers and gold nanoparticles protected with functionalized thiols.

The hydroxyl at the C-3 of cholic acid was converted to an amino group, and the resulting aminofunctionalized cholic acid was used as a monomer to prepare amide-linked oligomeric cholates. These cholate oligomers fold into helical structures with nanometer-sized hydrophilic internal cavities in solvent mixtures consisting of mostly nonpolar solvents such as carbon tetrachloride or ethyl acetate/hexane and 2−5% of a polar solvent such as methanol or DMSO. The conformations of the foldamers were studied by UV, fluorescence, fluorescence quenching, and fluorescence resonance energy transfer. The nature of the polar/ nonpolar solvents and their miscibility strongly influenced the folding reaction. Folding was cooperative, as evidenced by the sigmoidal curves in solvent denaturation experiments. The folded conformers became more stable with an increase in the chain length. The folding/unfolding equilibrium was highly sensitive toward the amount of polar solvent. One percent variation in the solvent composition could change the folding free energies by 0.5−1.4 kcal/mol. Disciplines Chemistry CommentsReprinted (adapted) Abstract:The hydroxyl at the C-3 of cholic acid was converted to an amino group, and the resulting aminofunctionalized cholic acid was used as a monomer to prepare amide-linked oligomeric cholates. These cholate oligomers fold into helical structures with nanometer-sized hydrophilic internal cavities in solvent mixtures consisting of mostly nonpolar solvents such as carbon tetrachloride or ethyl acetate/hexane and 2-5% of a polar solvent such as methanol or DMSO. The conformations of the foldamers were studied by UV, fluorescence, fluorescence quenching, and fluorescence resonance energy transfer. The nature of the polar/nonpolar solvents and their miscibility strongly influenced the folding reaction. Folding was cooperative, as evidenced by the sigmoidal curves in solvent denaturation experiments. The folded conformers became more stable with an increase in the chain length. The folding/unfolding equilibrium was highly sensitive toward the amount of polar solvent. One percent variation in the solvent composition could change the folding free energies by 0.5-1.4 kcal/mol.

A general method for sequence-specific binding of peptides remains elusive despite decades of research. By creating an array of “hydrophobically coded dimples” on the surface of a surface–core doubly cross-linked micelle, we synthesized water-soluble nanoparticle receptors to recognize peptides by the location, number, and nature of their hydrophobic side chains. Minute differences in the side chains could be distinguished and affinities up to 20 nM were obtained for biologically active oligopeptides in water.

Several water-soluble calix [4]arenes were synthesized via Huisgen 1,3-dipolar cycloaddition between azides and alkynes. Cationic, anionic, and nonionic calixarenes were prepared from a common azidocalixarene intermediate. Azidocalixarenes performed better than alkynylcalixarenes as precursors. The aggregation behavior of the water-soluble calixarenes was studied by 1H NMR spectroscopy. Disciplines Chemistry CommentsReprinted (adapted)

No abstract

A single- and a double-tailed cationic surfactant with the triallylammonium headgroup formed reverse micelles (RMs) in heptane/chloroform containing a small amount of water. The reverse micelles were cross-linked at the interface upon UV irradiation in the presence of a water-soluble dithiol cross-linker and a photoinitiator. The resulting interfacially cross-linked reverse micelles (ICRMs) of the single-tailed surfactant aggregated in a solvent-dependent fashion, whereas those of the double-tailed were identical in size as the corresponding RMs. The ICRMs could extract anionic metal salts, such as AuCl(4)(-) and PtCl(6)(2-), from water into the organic phase. Au and Pt metal nanoparticles were produced upon reduction of metal salts. The covalent nature of the ICRMs made the template synthesis highly predictable, with the size of the metal particles controlled by the amount of the metal salt and the method of reduction. Nanoalloys were obtained by combining two metal precursors in the same reaction. Reduction of the ICRM-entrapped aurate also occurred without any external reducing agents, and the gold nanoparticles differed dramatically from those obtained through sodium borohydride reduction. The same template allowed the preparation of luminescent Au(4), Au(8), and Au(13)-Au(23) clusters, as well as gold nanoparticles several nanometers in size, simply by using different amounts of gold precursor and reducing conditions.

Molecular recognition of carbohydrates plays vital roles in biology but has been difficult to achieve with synthetic receptors. Through covalent imprinting of carbohydrates in boroxole-functionalized cross-linked micelles, we prepared nanoparticle receptors for a wide variety of mono- and oligosaccharides. The boroxole functional monomer bound the sugar templates through cis-1,2-diol, cis-3,4-diol, and trans-4,6-diol. The protein-sized nanoparticles showed excellent selectivity for D-aldohexoses in water with submillimolar binding affinities and completely distinguished the three biologically important hexoses (glucose, mannose, and galactose). Glycosides with nonpolar aglycon showed stronger binding due to enhanced hydrophobic interactions. Oligosaccharides were distinguished based on their monosaccharide building blocks, glycosidic linkages, chain length, as well as additional functional groups that could interact with the nanoparticles.