Esterification of Aryl and Alkyl Amides Enabled by Tailor-Made and Proposed Nickel Catalyst: Insights from Theoretical Investigation.

DFT calculations are used to address the mechanism of Ni-catalyzed esterification of aryl and alkyl amides. The insight of the tailor-made catalysts in the chemo-selectivity is addressed in this work. The reaction steps for esterification of aryl and alkyl amides catalyzed by both Ni(SIPr)2 and Ni(terpyridine)2 include: oxidative addition, metathesis, and reductive elimination processes. Ni(SIPr)2 can catalyze the esterification of aryl amides rather than Ni(terpyridine)2 due to high reaction barrier in oxidative addition process, while Ni(terpyridine)2 can catalyze the esterification of alkyl amides rather than Ni(SIPr)2 due to high reaction barrier in metathesis process. It is found that the charge distribution on Ni is different in these two complexes. An amino-substituted terpyridine Ni complex is designed to catalyze both aryl and alkyl amides through low transition-state energies because of the electron-donating ability of three amino substitutes. The results reveal that the chemo-selectivity is mainly controlled by the electron-donating ability of ligands.

A novel lipopolysaccharide-binding protein (LBP) gene from sweetfish Plecoglossus altivelis: molecular characterization and its role in the immune response of monocytes/macrophages.

Lipopolysaccharide-binding protein (LBP) belongs to the lipid transfer/LBP (LT-LBP) family, and plays a crucial role in the recognition of bacterial components that modulate cellular signals in phagocytic cells. Although several LBPs have been identified in teleosts, the effects of LBP homologs on teleost phagocytic cells are still obscure. Here, we report the cloning a novel full-length cDNA sequence of LBP-like protein (paLBP) gene from sweetfish, Plecoglossus altivelis. The paLBP cDNA encoded a 464 aa polypeptide, which was closest to that of rainbow smelt (Osmerus mordax). paLBP mRNA was detected mainly in the spleen, liver, and head kidney and levels dramatically increased in various tissues after Listonella anguillarum infection. In contrast to mammalian studies, paLBP mRNA could also be detected in sweetfish monocytes/macrophages. Recombinant paLBP showed LPS-binding activity and Western blot results revealed a significant increase of paLBP in the supernatant of sweetfish monocytes/macrophages challenged with L. anguillarum. Moreover, paLBP neutralization led to up-regulation of IL-1ß and TNF-α mRNA as well as respiratory burst activity in sweetfish monocytes/macrophages in response to L. anguillarum or LPS challenge. Therefore, these results suggest that paLBP is an inducible acute-phase protein mediating the immune response of sweetfish monocytes/macrophages upon bacterial challenge.

Molecular characterization of a CXCL8-like protein from ayu and its effect on chemotaxis of neutrophils and monocytes/macrophages.

CXCL8, a CXC-type chemokine, plays a crucial role in acute inflammation by recruiting and mediating neutrophils and other cells. In this study, the cDNA and genomic DNA sequence of a CXCL8-like protein (PaCXCL8l) from ayu (Plecoglossus altivelis) was determined. Sequence analysis showed that PaCXCL8l represented the typical structure of animal CXCL8s. Phylogenetic tree analysis indicated that PaCXCL8l was closest to CXCL8 of Atlantic cod (Gadus morhua). Constitutive expression of PaCXCL8l was detected in all tested tissues and monocytes/macrophages, and its expression dramatically increased upon Listonella anguillarum infection. In vitro, recombinant PaCXCL8l exhibited a significant chemotactic effect on neutrophils at 0.1 µg/ml and on monocytes/macrophages at 1.0 µg/ml. In vivo, the numbers of peritoneal neutrophils and monocytes/macrophages were both up-regulated following intraperitoneal administration of recombinant PaCXCL8l. These results suggest that PaCXCL8l is crucially involved in the immune response of ayu by mediating chemotaxis of neutrophils and monocytes/macrophages.

Density functional theory studies on hydroxylamine mechanism of cyclohexanone ammoximation on titanium silicalite-1 catalyst.

The hydroxylamine mechanism of cyclohexanone ammoximation on defective titanium active site of titanium silicalite-1 (TS-1) was simulated using two-layer ONIOM (M062X/6-31G**:PM6) method. A new energy favorable reaction route was found, which contained two parts: (1) the catalytic oxidation of adsorbed NH3 to form hydroxylamine using the Ti-OOH as an active oxidant formed by reacting H2O2 with the defective Ti active site; (2) the subsequent noncatalytic oximation of desorbed hydroxylamine and cyclohexanone out of TS-1 pores to form cyclohexanone oxime. In the catalytic formation of hydroxylamine on the Ti active site of TS-1, the proposed mechanism of two-step single-proton transfer aided by a lattice oxygen atom bonded to Ti atom need a lower reaction energy than the mechanism proposed before. In the subsequent noncatalytic oximation of hydroxylamine and cyclohexanone, which contained two elementary reaction steps in total, the mechanisms of one-step double-proton transfer in the first elementary reaction step and the subsequent one-step three-proton transfer for the second elementary reaction step were proposed, in which the solvent water molecules played a very important role in assisting and stabilizing the proton transfer processes.