Aqueous organometallic reactions of rhodium porphyrins: equilibrium thermodynamics

The reactivity and equilibrium thermodynamic studies of tetra-p-sulfonatophenyl porphyrin rhodium hydride ([(TSPP)Rh-D]-4) with CO, aldehydes and olefins that produce formyl, alpha-hydroxyalkyl and alkyl complexes have been explored in water and compared with the related reactions in non-aqueous media.     

Zero Divisor Graphs of Finite Direct Products of Finite Rings

We determine the number of edges of the finite direct product of finite rings. We apply this result to finite rings without idempotents, in particular direct products of ? _m .     

Flow-Injection Differential Spectrophotometric pH Selectivity System for the Determination of Cyclamate Contaminants

A flow-injection system with differential spectrophotometric detection is proposed for the simultaneous determination of aniline and cyclohexylamine based on their reaction with 1,2-naphthoquinone-4-sulfonate (NQS). The pH is chosen to achieve selectivity since only aniline reacts at acidic pH whereas the two amines are derivatized in basic medium. The flow manifold comprises two reactors and two detection cells for developing and monitoring the reaction under selective and general (non-selective) conditions. A double beam spectrophotometer is used for differential detection, with two flow cells placed in the sample and reference holders. Figures of merit such as sensitivity, linear range, detection limit and precision are established. The evaluation of accuracy using a series of synthetic mixtures indicates overall prediction errors of 3% and 5% for aniline and cyclohexylamine, respectively. The method is applied to the determination of amine impurities in commercial sweeteners. Good concordance between the proposed and the standard chromatographic methods is found.     

GSK3B induces autophagy by phosphorylating ULK1

Unc-51-like autophagy activating kinase 1 (ULK1), a mammalian homolog of the yeast kinase Atg1, has an essential role in autophagy induction. In nutrient and growth factor signaling, ULK1 activity is regulated by various posttranslational modifications, including phosphorylation, acetylation, and ubiquitination. We previously identified glycogen synthase kinase 3 beta (GSK3B) as an upstream regulator of insulin withdrawal-induced autophagy in adult hippocampal neural stem cells. Here, we report that following insulin withdrawal, GSK3B directly interacted with and activated ULK1 via phosphorylation of S405 and S415 within the GABARAP-interacting region. Phosphorylation of these residues facilitated the interaction of ULK1 with MAP1LC3B and GABARAPL1, while phosphorylation-defective mutants of ULK1 failed to do so and could not induce autophagy flux. Furthermore, high phosphorylation levels of ULK1 at S405 and S415 were observed in human pancreatic cancer cell lines, all of which are known to exhibit high levels of autophagy. Our results reveal the importance of GSK3B-mediated phosphorylation for ULK1 regulation and autophagy induction and potentially for tumorigenesis.Subject terms: Macroautophagy, Phosphorylation     

MD Simulation of an Infinitely Dilute Aqueous Solution of Formamide. Study of Thermodynamic, Structural, Dynamic, and Spectroscopic Properties

A molecular dynamics simulation of an infinitely dilute aqueous solution of formamide was carried out using an MP2-CP ab initio potential to describe the solute–solvent interaction. Various static and dynamic properties were calculated using this potential obtained by fitting the formamide–water interaction energies to a 12-6-1 type function. These energies were calculated with the supermolecular approach by considering the MP2 correlation and the CP superposition. The values presented for the thermodynamic functions (H _S–W = –25.5 kcal-mol^–1 and G _S–W = –15.9 kcal-mol^–1), the structure of the first hydration layer (with 5 to 6 solvent molecules bonded to the solute), the solute's translational (D= 1.50 × 10^–5 cm²-s^–1) and rotational ( = 6.6 ps) mobility in the surrounding medium, and the positions of the H···O hydrogen bond spectral bands corresponding to these motions (_i = 92, 246, 379, and 636 cm^–1), are in agreement with the available results for this and other similar systems. In addition, the results are compared with those obtained by using parameters transferred from other systems. We observed that these values depend strongly on the potential used and concluded that it is advisable to avoid the use of such parameters.     

Structural and spectroscopic studies of nickel(II) complexes with a library of Bis(oxime)amine-containing ligands

A library of tripodal amine ligands with two oxime donor arms and a variable coordinating or noncoordinating third arm has been synthesized, including two chiral ligands based on l-phenylalanine. Their Ni(II) complexes have been synthesized and characterized by X-ray crystallography, UV-vis absorption, circular dichroism, and FTIR spectroscopy, mass spectrometry, and room-temperature magnetic susceptibility. At least one crystal structure is reported for all but one Ni/ligand combination. All show a six-coordinate pseudo-octahedral coordination geometry around the nickel center, with the bis(oxime)amine unit coordinating in a facial mode. Three distinct structure types are observed: (1) for tetradentate ligands, six-coordinate monomers are formed, with anions and/or solvent filling out the coordination sphere; (2) for tridentate ligands, six-coordinate monomers are formed with Ni(II)(NO(3))(2), with one monodentate and one bidentate nitrate filling the remaining coordination positions; (3) for tridentate ligands, six-coordinate, bis(mu-Cl) dimers are formed with Ni(II)Cl(2), with one terminal and two bridging chlorides filling the coordination sphere. The UV-vis absorption spectra of the complexes show that the value of 10 Dq varies according to the nature of the third arm of the ligand. The trend based on the third arm follows the order alkyl/aryl < amide < carboxylate < alcohol < pyridyl < oxime.