Indole as a scaffold for anion recognition

Indole has an acidic N-H that can be used to form hydrogen bonds to anions and in this paper the synthesis of three new suitably functionalised indole based anion receptors is presented along with their evaluation using (1)H NMR titration techniques.     

High-density targeting of a viral multifunctional nanoplatform to a pathogenic, biofilm-forming bacterium

Nanomedicine directed at diagnosis and treatment of infections can benefit from innovations that have substantially increased the variety of available multifunctional nanoplatforms. Here, we targeted a spherical, icosahedral viral nanoplatform to a pathogenic, biofilm-forming bacterium, Staphylococcus aureus. Density of binding mediated through specific protein-ligand interactions exceeded the density expected for a planar, hexagonally close-packed array. A multifunctionalized viral protein cage was used to load imaging agents (fluorophore and MRI contrast agent) onto cells. The fluorescence-imaging capability allowed for direct observation of penetration of the nanoplatform into an S. aureus biofilm. These results demonstrate that multifunctional nanoplatforms based on protein cage architectures have significant potential as tools for both diagnosis and targeted treatment of recalcitrant bacterial infections.     

Effective gel for gold nanoparticle formation, support and metal oxide templating

Gold nanoparticles were synthesized using agarose as a reducing agent, which gelled to support the gold nanoparticles, then readily functioned as a template to produce a porous, evenly-distributed Au/TiO(2) nano-hybrid.     

Copper(I) cyanide networks: synthesis, luminescence behavior and thermal analysis. Part 1. Diimine ligands

Metal-organic networks of CuCN with diimines (L) = pyrazine (Pyz), 2-aminopyrazine (PyzNH(2)), quinoxaline (Qox), phenazine (Phz), 4,4'-bipyridyl (Bpy), pyrimidine (Pym), 2-aminopyrimidine (PymNH(2)), 2,4-diaminopyrimidine (Pym(NH(2))(2)), 2,4,6-triaminopyrimidine (Pym(NH(2))(3)), quinazoline (Qnz), pyridazine (Pdz), and phthalazine (Ptz) were studied. Open reflux reactions produced complexes (CuCN)(2)(L) for L = Qox, Phz, Bpy, PymNH(2), Pym(NH(2))(2), Qnz, and Pdz and (CuCN)(3)(L) complexes for L = Pyz, PyzNH(2), Qox, Bpy, Pym(NH(2))(3), and Pdz. Also produced were (CuCN)(3)(Pyz)(2), (CuCN)(PyzNH(2)), (CuCN)7(Pym)(2), (CuCN)(5)(Qnz)(2) and (CuCN)(5)(Ptz)(2). X-ray structures are presented for (CuCN)(2)(Pdz), (CuCN)(2)(PymNH(2)), and (CuCN)(7)(Pym)(2). Hydrothermal reactions yielded additional X-ray structures of (CuCN)(2)(PyzNH(2)), (CuCN)(3)(Pym(NH(2))(2)), (CuCN)(4)(Qnz), a second (CuCN)(2)(Pdz) phase, (CuCN)(5)(Pdz)2, (CuCN)(2)(Ptz), and (CuCN)(7)(Ptz)2. Structural trends, including cuprophilic interactions and cyano-bridged Cu(2)(CN)(2) dimer formation, are discussed. Particularly short Cu...Cu interactions are noted for the novel 4- and 5-coordinate Cu(2)(CN)(2) dimers. Thermal analyses show that most of the complexes decompose with loss of L around 160-180 degrees C. Luminescence behavior is relatively weak in the products.     

Metal complexes of thiazyl radicals

A diverse variety of thiazyl radicals is known. Intense study of these heterocycles continues in the pursuit of molecule-based materials with novel, academically interesting, and technologically relevant properties. Coordination of these species to metal atoms and ions has focused primarily on the 1,2,3,5-dithiadiazolyl 2 and 1,3,2-dithiazolyl 6. The potential of these two heterocycles as ligand building-blocks has, by no means, been fully exploited. From the structural and electronic similarities between 2 and the verdazyl and nitronyl nitroxide radicals, it is apparent that similar radical ligand designs ought to be achievable. The sulfur atoms of 2 lend a unique feature to this radical that may yet be employed as a means of controlling intermolecular interactions or developing multi-metal species. The recent report of sulfur coordination to 6 demonstrates that there is yet more design flexibility available from this thiazyl as well. Coordination complexes of other radical thiazyls have begun appearing in the literature. This field is currently in its infancy and is starting to be recognized as an enormous source of untapped potential in the future development of molecule-based materials.     

Coiled coils 9-to-5: rational de novo design of α-helical barrels with tunable oligomeric states

The rational design of linear peptides that assemble controllably and predictably in water is challenging. Short sequences must encode unique target structures and avoid alternative states. However, the non-covalent forces that stabilize and discriminate between states are weak. Nonetheless, for α-helical coiled-coil assemblies considerable progress has been made in rational de novo design. In these, sequence repeats of nominally hydrophobic (h) and polar (p) residues, hpphppp, direct the assembly of amphipathic helices into dimeric to tetrameric bundles. Expanding this pattern to hpphhph can produce larger α-helical barrels. Here, we show that pentameric to nonameric barrels are accessed by varying the residue at one of the h sites. In peptides with four L/I–K–E–I–A–x–Z repeats, decreasing the size of Z from threonine to serine to alanine to glycine gives progressively larger oligomers. X-ray crystal structures of the resulting α-helical barrels rationalize this: side chains at Z point directly into the helical interfaces, and smaller residues allow closer helix contacts and larger assemblies.

Systematic de novo design of peptides that form α-helical barrels with functionalisable central channels with a range of internal diameters.     

Unimolecular micelles: Synthesis and characterization of amphiphilic polymer systems

Unimolecular micelles were successfully synthesized from mucic acid, fatty acids, and poly(ethylene glycols) to create biocompatible polymers. These polymers consist of a core‐shell structure that resembles conventional micellar structures but with significant thermodynamic stability in aqueous media. The core of the polymers provide a hydrophobic environment for drug encapsulation via hydrophobic interactions, whereas the shell provides excellent water solubility. The polymers were characterized by nuclear magnetic resonance, infrared and mass spectroscopies, as well as gel permeation chromatography, differential scanning calorimetry, and thermogravimetric and elemental analyses. Encapsulation ability was measured using high‐pressure liquid chromatography to monitor lidocaine, a hydrophobic molecule. Encapsulation capabilities increased as lipophilicity of the core increased. To verify that encapsulation was caused by individual unimolecular micelles, surface tension and dynamic light scattering measurements were performed. The results indicated that these unimolecular micelles have great potential as drug carriers. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 703–711, 1999     

Phase-oriented surface segregation in an aluminium casting alloy

There have been many reports of the surface segregation of minor elements, especially Mg, into surface layers and oxide films on the surface of Al alloys. LM6 casting alloy (Al-12%Si) represents a challenging system to examine such segregation as the alloy features a particularly inhomogeneous phase structure. The very low but mobile Mg content (approximately 0.001 wt.%), and the surface segregation of modifiers such as Na, mean the surface composition responds in a complex manner to thermal treatment conditions. X-ray photoelectron spectroscopy (XPS) has been used to determine the distribution of these elements within the oxide film. Further investigation by dynamic secondary ion mass spectrometry (DSIMS) confirmed a strong alignment of segregated Na and Mg into distinct phases of the structure.     

Rapid Ti(Oi-Pr)4 facilitated synthesis of α,α,α-trisubstituted primary amines by the addition of Grignard reagents to nitriles under microwave heating conditions

A series of carbinamines (α,α,α-trisubstituted amines) have been prepared in a simple and efficient one-pot procedure by the addition of Grignard reagents to a series of aliphatic, aromatic and heteroaromatic nitriles. The resulting magnesium imines are subsequently converted to the desired amine after treatment with Ti(Oi-Pr)₄ and additional microwave heating. Key to this procedure is the use of microwave heating for both steps of the reaction protocol, which significantly improves both reaction yields and reduces reaction times. In general, the Grignard addition reaction is complete within 5-10 min at 100 °C followed by conversion with Ti(Oi-Pr)₄ and additional microwave heating to give the target amines in good yields.