Mechanistic insights into small molecule activation induced by ligand cooperativity in PCcarbeneP nickel pincer complexes: a quantum chemistry study.

Mechanisms for the activation of water, ammonia, and other small molecules by the PCcarbeneP nickel pincer complex were studied computationally with the aid of density functional theory. The calculation results indicate that the strongly donating, nucleophilic carbene center can engage in a variety of heterolytic splitting of E-H (E=H, C, N, O) bonds, some of which are reversible. The cleavage of E-H bonds across the Ni=C bond represents a new mode of bond activation by ligand cooperativity in nickel pincer complex. On the basis of the calculations, we also demonstrate that reversible H2 activation across the Ir=C bond via the PCcarbeneP iridium pincer complex was observed in the experiments, while other E-H (E=C, N, O) bonds were not activated. Our calculations are in good agreement with experimental observations and could provide new insights into ligand cooperativity in nickel pincer complexes.

Explore the reaction mechanism of the Maillard reaction: a density functional theory study.

The mechanism of Maillard reaction has been investigated by means of density functional theory calculations in the gaseous phase and aqueous solution. The Maillard reaction is a cascade of consecutive and parallel reaction. In the present model system study, glucose and glycine were taken as the initial reactants. On the basis of previous experimental results, the mechanisms of Maillard reaction have been proposed, and the possibility for the formation of different compounds have been evaluated through calculating the relative energy changes for different steps of reaction under different pH conditions. Our calculations reveal that the TS3 in Amadori rearrangement reaction is the rate-determining step of Maillard reaction with the activation barriers of about 66.7 and 68.8 kcal mol(-1) in the gaseous phase and aqueous solution, respectively. The calculation results are in good agreement with previous studies and could provide insights into the reaction mechanism of Maillard reaction, since experimental evaluation of the role of intermediates in the Maillard reaction is quite complicated.

Morphology and functions of astrocytes cultured on water-repellent fractal tripalmitin surfaces.

In the brain, astrocytes play an essential role with their multiple functions and sophisticated structure, as surrounded by a fractal environment which has not been available in our traditional cell culture. Water-repellent fractal tripalmitin (PPP) surfaces can imitate the fractal environment in vivo, so the morphology and biochemical characterization of astrocytes on these surfaces are examined. Water-repellent fractal PPP surface can induce astrocytes to display sophisticated morphology with smaller size of cell area, longer and finer filopodium-like processes, and higher morphological complexity. The super water-repellent fractal PPP surface with water contact angle of 150°âˆ¼160° produces the maximal effects compared with other surfaces at lower water contact angles. The trends of characteristic protein expression, including that of nestin, vimentin, GFAP and glutamine synthetase, for astrocytes cultured on super water-repellent fractal PPP surfaces approximate more to in vivo pattern. The super water-repellent PPP surface also render astrocytes to perform more pronounced promotion of neurogenesis by increasing the release of nerve growth factor in a co-culture system. Altogether, our results suggest that the super water-repellent fractal PPP surface facilitates the astrocytes to mimic their in vivo performance, thus provides a closer-to-natural culture environment for experimental assessment of glial structure and functions.

Intermolecular interactions between gold clusters and selected amino acids cysteine and glycine: a DFT study.

The intermolecular interactions between Au(n) (n = 3-4) clusters and selected amino acids cysteine and glycine have been investigated by means of density functional theory (DFT). Present calculations show that the complexes possessing Au-NH(2) anchoring bond are found to be energetically favored. The results of NBO and frontier molecular orbitals analysis indicate that for the complex with anchoring bonds, lone pair electrons of sulfur, oxygen, and nitrogen atoms are transferred to the antibonding orbitals of gold, while for the complex with the nonconventional hydrogen bonds (Au···H-O), the lone pair electrons of gold are transferred to the antibonding orbitals of O-H bonds during the interaction. Furthermore, the interaction energy calculations show that the complexes with Au-NH(2) anchoring bond have relatively high intermolecular interaction energy, which is consistent with previous computational studies.

[Synthesis, spectral analysis, antibacterial and antitumor activities of Co(II) and Ni(II) ofloxacin complexes].

The interactions of cobalt sulphate and nickel acetate with ofloxacin (ofo, I), a 4-quinoline derivative, were studied. The hydrothermal technique was adopted in this work. The isolated solid complexes were characterized by elemental analysis, infrared spectra, electronic spectra, fluorescence spectra and thermal analysis. The results support the formation of complexes of the formula Co(ofo)2 x 4H2O (II) and Ni(ofo)2 x 4H2O (III). The infrared spectra of the isolated solid complexes suggested that ofo acts as bidentate ligands through one of the oxygen atoms of the carboxylic group and the ring carbonyl oxygen atom. Thermogravimetric (TG) and its differential (DTG) were carried out for the complexes. The data obtained indicated that the thermal decomposition of the two complexes in inert atmosphere proceeded approximately with two main degradation steps. I showed a intense fluorescence in solid state at lamda(ex)/lamda(em) = 365 nm/461 nm, and two complexes displayed weakly similar emission maximum at 470 nm in the powder samples at ambient temperature, while the emission of II and III may be mainly originated from the intraligand excited states of I. I, II and III were assayed against two kinds of gram-positive and two kinds of gram-negative bacteria by in vitro doubling dilutions method. The results indicated that II and III have the similar minimal inhibitory concentration (MIC) as the I against S. Aureus, M. Lutens, E. Coli and P. Aeruginosa. The inhibitory effect of I, II and III on leukemia HL-60 cell line has been measured by using MTT (Methyl-Thiazol-Tetrozolium) method and that on liver cancer BEL-7402 cell line measured by SRB (Sulphurhodamin B) method. The results indicated that the complexes in the high concentration have inhibitory effect on HL-60 cell line.