Electron Deficient Monomers that Optimize Nucleation and Enhance the Photocatalytic Redox Activity of Carbon Nitrides

Polymeric carbon nitride (PCN) is usually synthesized from nitrogen‐rich monomers such as cyanamide, melamine, and urea, but is rather disordered in many cases. Now, a new allotrope of carbon nitride with internal heterostructures was obtained by co‐condensation of very electron poor monomers (for example, 5‐amino‐tetrazole and nucleobases) in the presence of mild molten salts (for example, NaCl/KCl) to mediate the polymerization kinetics and thus modulate the local structure, charge carrier properties, and most importantly the HOMO and LUMO levels. Results reveal that the as‐prepared NaK‐PHI‐A material shows excellent photo‐redox activities because of a nanometric hetero‐structure which enhances visible light absorption and promotes charge separation in the different domains.     

Quasi-minimality and tightness by range in spaces with unconditional basis

We present a reflexive Banach space with an unconditional basis which is quasi-minimal and tight by range, i.e., of type (4) in the Ferenczi-Rosendal list within the framework of Gowers’ classification program of Banach spaces. The space is an unconditional variant of the Gowers Hereditarily Indecomposable space with an asymptotically unconditional basis.     

Generalizations of Runs and Patterns Distributions for Sequences of Binary Trials

Methodology and Computing in Applied Probability - In the present paper we study the distributions of families of patterns which generalize runs and patterns distributions extensively examined in...     

One-Step Synthesis of 2-Amino-1-methylimidazo[4,5-b]quinoline

The novel title compound, a linear isomer of the food mutagen IQ, has been prepared in 67 % yield by Friedländer synthesis from creatinine and 2-aminobenzaldehyde.     

Global hyperbolicity and completeness

We prove global hyperbolicity of spacetimes under generic regularity conditions on the metric. We then show that these spacetimes are timelike and null geodesically complete if the gradient of the lapse and the extrinsic curvature K are integrable. This last condition is required only for the tracefree part of K if the universe is expanding.     

The silver-oxygen system in catalysis: new insights by near ambient pressure X-ray photoelectron spectroscopy

We addressed the interaction of oxygen with silver by synchrotron based near ambient pressure X-ray photoelectron spectroscopy at temperatures relevant for industrial oxidation reactions performed with silver catalysts. For silver single crystals, polycrystalline foils and powders in equilibrium with gas phase O(2), we observed the dynamics of the formation of five different atomic oxygen species with relative abundances depending on the temperature and time. Correlation of their formation kinetics with spectroscopic features and thermal stability indicates that these are distinct species with different electronic structures, which might relate to the different roles of silver in oxidation reactions.     

Heptanuclear heterometallic [Cu6Ln] clusters: trapping lanthanides into copper cages with artificial amino acids

Employment of the artificial amino acid 2-amino-isobutyric acid, aibH, in Cu(II) and Cu(II)/Ln(III) chemistry led to the isolation and characterization of 12 new heterometallic heptanuclear [Cu(6)Ln(aib)(6)(OH)(3)(OAc)(3)(NO(3))(3)] complexes consisting of trivalent lanthanide centers within a hexanuclear copper trigonal prism (aibH = 2-amino-butyric acid; Ln = Ce (1), Pr (2), Nd (3), Sm (4), Eu (5), Gd (6), Tb (7), Dy (8), Ho (9), Er (10), Tm (11), and Yb (12)). Direct curent magnetic susceptibility studies have been carried out in the 5-300 K range for all complexes, revealing the different nature of the magnetic interactions between the 3d-4f metallic pairs: dominant antiferromagnetic interactions for the majority of the pairs and dominant ferromagnetic interactions for when the lanthanide center is Gd(III) and Dy(III). Furthermore, alternating current magnetic susceptibility studies reveal the possibility of single-molecule magnetism behavior for complexes 7 and 8. Finally, complexes 2, 5-8, 10, and 12 were analyzed using positive ion electrospray mass spectrometry (ES-MS), establishing the structural integrity of the heterometallic heptanuclear cage structure in acetonitrile.     

Biaryl-bridged macrocyclic peptides: conformational constraint via carbogenic fusion of natural amino acid side chains

A general method for constraining peptide conformations via linkage of aromatic sidechains has been developed. Macrocyclization of suitably functionalized tri-, tetra- and pentapeptides via Suzuki-Miyaura cross-coupling has been used to generate side chain to side chain, biaryl-bridged 14- to 21-membered macrocyclic peptides. Biaryl bridges possessing three different configurations, meta-meta, meta-ortho, and ortho-meta, were systematically explored through regiochemical variation of the aryl halide and aryl boronate coupling partners, allowing fine-tuning of the resultant macrocycle conformation. Suzuki-Miyaura macrocyclizations were successfully achieved both in solution and on solid phase for all three sizes of peptide. This approach constitutes a means of constraining peptide conformation via direct carbogenic fusion of side chains of naturally occurring amino acids such as phenylalanine and tyrosine, and so is complementary to strategies involving non-natural, for example, hydrocarbon, bridges.     

Diblock copolymer dynamics

Three aspects of block copolymer dynamics are reviewed with emphasis on the influence of the proximity to the disorder-to-order transition. The relaxation of composition fluctuations in disordered diblocks is discussed over the whole range of wavevectors. The translational motion of individual copolymer chains is reviewed both with respect to the effects of ordering on the long-time diffusional motion and on the motion for short time- and length-scales. Finally, the behavior of the block orientational relaxation is briefly summarized.     

Probing the function of Mycobacterium tuberculosis catalase-peroxidase by site-directed mutagenesis

Catalase-peroxidase is a multi-functional heme-dependent enzyme which is well known for its ability to carry out both catalatic and peroxidatic reactions. Catalase-peroxidase from Mycobacterium tuberculosis(mtCP) is of particular interest because this enzyme activates the pro-antitubercular drug isoniazid. It is estimated that 2 billion people are infected with M. tuberculosis, the principal causative agent of tuberculosis, and that 2 million people die from the disease each year. The rise of drug-resistant strains continues to be of critical concern and it is well documented that mutations which reduce activity or inactivate mtCP lead to increased levels of isoniazid resistance in M. tuberculosis. The recent determination of the crystal structure for M. tuberculosis mtCP has aided the understanding of how the enzyme functions and provides a three-dimensional framework for testing hypotheses about the roles of various residues in the active site. Here we report site-directed mutagenesis studies of three conserved residues located near the heme of mtCP, His-108, Trp-107 and Trp-321 including the construction of the double mutant W107F-W321F. Resulting mutants have been purified and their catalatic and peroxidatic activities have been determined. Data are compared in the context of related studies aimed at dissecting the roles of these residues in the different activities of the enzyme. Analyses of single and double mutants studied here emphasise that the hydrogen bonding network surrounding the heme in the active site appears more important for maintenance of catalatic rather than peroxidatic activity in CP enzymes.