Theoretical prediction of ELNES/XANES and chemical bondings of AlN polytypes

The first principles calculations of ELNES/XANES of AlN polytypes were carried out by the first-principles OLCAO method using large supercells composed of more than 100 atoms. It can quantitatively reproduce the experimental spectra from wurtzite AlN using a 108-atoms supercell. ELNES from rock-salt and zinc-blend AlN were predicted by using 128 atoms supercells. The spectral features of rock-salt phase are different from other phases, whereas that of zinc-blend phase have numerous similarities with that from wurtzite AlN. Characteristic differences between the wurtzite and zinc-blend phases are predicted to appear at the first peak of Al L(2,3) and K edges. The first peak of zinc-blend AlN is broader than that of wurtzite AlN. The same tendency was found in the case of SiC. In order to elucidate the cause of the broadness at the first peak, partial density of states and chemical bondings were investigated. The theoretical analysis revealed that the broadness of the first peak is related to the covalency of the compounds. This result suggests that the spectral features at the first peak of L(2,3) and K edges contain information about the covalency at the illuminated area.     

A Global Review on Short Peptides: Frontiers and Perspectives

Peptides are fragments of proteins that carry out biological functions. They act as signaling entities via all domains of life and interfere with protein-protein interactions, which are indispensable in bio-processes. Short peptides include fundamental molecular information for a prelude to the symphony of life. They have aroused considerable interest due to their unique features and great promise in innovative bio-therapies. This work focusing on the current state-of-the-art short peptide-based therapeutical developments is the first global review written by researchers from all continents, as a celebration of 100 years of peptide therapeutics since the commencement of insulin therapy in the 1920s. Peptide “drugs” initially played only the role of hormone analogs to balance disorders. Nowadays, they achieve numerous biomedical tasks, can cross membranes, or reach intracellular targets. The role of peptides in bio-processes can hardly be mimicked by other chemical substances. The article is divided into independent sections, which are related to either the progress in short peptide-based theranostics or the problems posing challenge to bio-medicine. In particular, the SWOT analysis of short peptides, their relevance in therapies of diverse diseases, improvements in (bio)synthesis platforms, advanced nano-supramolecular technologies, aptamers, altered peptide ligands and in silico methodologies to overcome peptide limitations, modern smart bio-functional materials, vaccines, and drug/gene-targeted delivery systems are discussed.     

A chelation-assisted transformation: synthesis of maleimides by the Rh-catalyzed carbonylation of alkynes with pyridin-2-ylmethylamine

The reaction of alkynes 1 with CO and pyridin-2-ylmethylamine (2) in the presence of Rh4(CO)12/P(OEt)3 results in the incorporation of two molecules of CO leading to maleimide derivatives 3. The coordination of the pyridine nitrogen in 2 to a rhodium center is essential for the reaction to proceed.     

Selective photocatalytic reduction of nitrate to nitrogen molecules in an aqueous suspension of metal-loaded titanium(IV) oxide particles

Nitrate was photocatalytically reduced to nitrogen molecules with a high selectivity in a basic aqueous suspension of palladium and copper-loaded titanium(IV) oxide powders in the presence of oxalate anion as a hole scavenger.     

Total synthesis of tylonolide,an aglycone of tylosin

The total synthesis of tyionolide, a 16-membered-ring aglycone of a macrolide antibiotic, tyiosin, has been accomplished by coupling two segments of C1-C10 and C11-C17 portions, which are stereospecifically derived from D-glucose.     

Rhenium-catalyzed regio- and stereoselective addition of imines to terminal alkynes leading to N-alkylideneallylamines

The reaction of terminal alkynes with imines using ReBr(CO)(5) as a catalyst results in the production of N-alkylideneallylamines and not the conventional propargylamines. The substituent on the imine nitrogen is important, and a diphenylmethyl group gave the best result. The catalytic cycle of this regioselective C-C bond forming reaction appears to involve the formation of an alkynyl rhenium species and subsequent nucleophilic attack of the alkynyl β-carbon atom on the imine carbon to give a vinylidene rhenium species.     

Nonradiative decay dynamics of methyl-4-hydroxycinnamate and its hydrated complex revealed by picosecond pump-probe spectroscopy

The lifetimes of methyl 4-hydroxycinnamate (OMpCA) and its mono-hydrated complex (OMpCA-H(2)O) in the S(1) state have been measured by picosecond pump-probe spectroscopy in a supersonic beam. For OMpCA, the lifetime of the S(1)-S(0) origin is 8-9 ps. On the other hand, the lifetime of the OMpCA-H(2)O complex at the origin is 930 ps, which is ～100 times longer than that of OMpCA. Furthermore, in the complex the S(1) lifetime shows rapid decrease at an energy of ～200 cm(-1) above the origin and finally becomes as short as 9 ps at ～500 cm(-1). Theoretical calculations with a symmetry-adapted cluster-configuration interaction (SAC-CI) method suggest that the observed lifetime behavior of the two species is described by nonradiative decay dynamics involving trans → cis isomerization. That is both OMpCA and OMpCA-H(2)O in the S(1) state decay due to the trans → cis isomerization, and the large difference of the lifetimes between them is due to the difference of the isomerization potential energy curve. In OMpCA, the trans → cis isomerization occurs smoothly without a barrier on the S(1) surface, while in the OMpCA-H(2)O complex, there exists a barrier along the isomerization coordinate. The calculated barrier height of OMpCA-H(2)O is in good agreement with that observed experimentally.