Significant and differential acceleration of dephosphorylation of the insecticides, paraoxon and parathion, caused by alkali metal ethoxides

In the reaction of paraoxon with alkali metal ethoxides, ion-paired EtO-M+ species are more reactive than the dissociated EtO- with the reactivity order EtO-Li+ EtO-Na+ > EtO-K+ > EtO-, while in the reaction of parathion, the reactivity follows the order EtO-K+ > EtO- > EtO-Na+ > EtO-Li+.     

Synthesis of a model system for the preparation of phloroglucinol containing natural products

A model system for the synthesis of phloroglucinol containing natural products was synthesized. Key steps include a manganic acetate-mediated cyclization and the facile conversion of an alkene into a β-bromoenone.     

Water sorption and activation energy in polyimide thin films

The water sorption behavior and the activation energy were investigated for various chemical structure polyimide thin films; BPDA‐PDA, BPDA‐ODA, PMDA‐ODA, and 6FDA‐ODA. The activation energy for the water diffusion varied in the range of 5.53 to 9.27kcal/mol, and was in the increasing order: BPDA‐PDA < BPDA‐ODA < PMDA‐ODA < 6FDA‐ODA. BPDA‐PDA and BPDA‐ODA polyimide films showed relatively well‐ordered morphological structure, which results in relatively low diffusion coefficient and high activation energy. It was found that the diffusion coefficient and the activation energy are significantly related to the in‐plane orientation, crystallinity, and packing order in the polyimide thin films. The morphological structure was predominant factors for the water diffusion coefficient and activation energy in the polyimide thin films. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2714–2720, 2000     

Structural basis for inhibition of protein tyrosine phosphatases by Keggin compounds phosphomolybdate and phosphotungstate

Protein-tyrosine phosphatases (PTPs) constitute a family of receptor-like, and cytoplasmic enzymes, which catalyze the dephosphorylation of phosphotyrosine residues in a variety of receptors and signaling molecules. Together with protein tyrosine kinases (PTKs), PTPs are critically involved in regulating many cellular signaling processes. In this study, diverse compounds were screened for PTP inhibition and selectively screened for inhibitors with the end product inhibition properties. Among phosphate analogues and their derivatives for PTP inhibition, Keggin compounds phosphomolybdate (PM) and phosphotungstate (PT) strongly inhibited both PTP-1B and SHP-1, with K(i) values of 0.06-1.2 micromM in the presence of EDTA. Unlike the vanadium compounds, inhibition potencies of PM and PT were not significantly affected by EDTA. PM and PT were potent, competitive inhibitors for PTPs, but relatively poor inhibitors of Ser/Thr phosphatase. Interestingly, PM and PT did not inhibit alkaline phosphatase at all. The crystal structure of PTP-1B in complex with PM, at 2.0 A resolution, reveals that MoO(3), derived from PM by hydrolysis, binds at the active site. The molybdenium atom of the inhibitor is coordinated with six ligands: three oxo-ligands, two apical water molecules and a S atom of the catalytic cysteine residue. In support of the crystallographic finding, we observed that molybdenium oxides (MoO(3), MoO(2), and MoO(2)Cl(2)) inhibited PTP-1B with IC(50) in the range 5-15 micromM.     

Preparation of the conjugated polyene chains with the 1,4-dimethyl substitution

Allylic sulfones undergo the conjugate addition to diethyl chloroisopropylidenemalonate, followed by intramolecular cyclopropanation. DBU-promoted ring opening and subsequent desulfonation reactions of the resulting adduct produce the conjugated polyene chains with the 1,4-dimethyl substitution.     

p21Cip/WAF1 activation is an important factor for the ERK pathway dependent anti-proliferation of colorectal cancer cells

p21Cip/WAF1, an important regulator of cell proliferation, is induced by both p53- and extracellular signal regulated kinase (ERK) pathways. The induction of p21Cip/WAF1 occurs by prolonged activation of the ERKs caused by extracellular stimuli, such as zinc. However, not all the cells appeared to respond to ERK pathway dependent p21Cip/WAF1 induction. Here we investigated the cause of such difference using colorectal cancer cells. p21Cip/WAF1 induction and concomitant reduction of bromodeoxyuridine (BrdU) incorporation were observed by zinc treatment within HT-29 and DLD-1. However, HCT-116 cells with high endogenous p21Cip/WAF1 levels did not show any additional increment of p21Cip/WAF1 levels by zinc treatment and did maintain high BrdU incorporation level. The p21Cip/WAF1 induction by zinc depended upon prolonged activation of extracellular signal regulated kinase (ERK) was not observed in HCT-116 cells. The percentage of BrdU positive cells was 50% higher in p21Cip/WAF1 -/- HCT-116 cells compared to p21Cip/WAF1 +/+ HCT- 116 cells, and no cells induced p21Cip/WAF1 incorporated BrdU in its nucleus, yet confirming the importance of p21Cip/WAF1 induction in anti- proliferation. These results again support that p21Cip/WAF1 induction is a determinant in the regulation of colonic proliferation by the ERK pathway.     

Lysophosphatidylcholine suppresses apoptosis and induces neurite outgrowth in PC12 cells through activation of phospholipase D2

Lysophosphatidylcholine (LPC) is a bioactive lipid generated by phospholipase A2-mediated hydrolysis of phosphatidylcholine. In the present study, we demonstrate that LPC stimulates phospholipase D2 (PLD2) activity in rat pheochromocytoma PC12 cells. Serum deprivation induced cell death of PC12 cells, as demonstrated by decreased viability, DNA fragmentation, and increased sub-G1 fraction of cell cycle. LPC treatment protected PC12 cells partially from the cell death and induced neurite outgrowth of the cells. Overexpression of PLD2 drastically enhanced the LPC-induced inhibition of apoptosis and neuritogenesis. Pretreatment of the cells with 1-butanol, a PLD inhibitor, completely abrogated the LPC-induced inhibition of apoptosis and neurite outgrowth in PC12 cells overexpressing PLD2. These results indicate that LPC possesses the neurotrophic effects, such as anti-apoptosis and neurite outgrowth, through activation of PLD2.     

A facile and simple method for the preparation of copoly(TEAMPS/VP)/silver nanocomposites for the humidity-sensing membranes

We developed a simple method for the preparation of polyelectrolyte/silver nanocomposites, where silver nanoparticles were dispersed in a polyelectrolyte. Copoly(TEAMPS/VP)/silver (w/w=100/0, 100/1, 100/2, 100/3 and 100/4) nanocomposites were obtained by a thermal decomposition reaction of silver carbamate complex at 130 degrees C, and well-dispersed silver colloids were stabilized by copolymer of tetraethylammonium 2-acrylamido-2-methyl-1-propanesulfonate (TEAMPS) and N-vinylpyrrolidone (VP). A dark brown solution in its UV-vis absorption spectrum showed surface plasmon resonance absorption bands at 420 nm in solution. The silver precursor and the resulting polyelectrolyte/Ag nanocomposite was characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD), infrared (IR), transmission electron microscopy (TEM). In addition the humidity-sensing properties using copoly(TEAMPS/VP)/Ag nanocomposite films were examined.     

Structural change of 1-butyl-3-methylimidazolium tetrafluoroborate + water mixtures studied by infrared vibrational spectroscopy

Mixtures of ionic liquid (IL, 1-butyl-3-methylimidazolium tetrafluoroborate, [BMIM][BF4]) and water with varying concentrations were studied by attenuated total reflection infrared absorption and Raman spectroscopy. Changes in the peak intensities and peak positions of CHx (x = 1, 2, 3) vibration modes of the cation of the IL and OH vibration modes of the water molecules were investigated. Peaks from normal-mode stretch vibrations of CH bonds belonging to the imidazolium ring of the cation did not change their positions, while those from the terminal methyl group of the butyl chain blueshifted by approximately 10 cm-1 with the addition of water. On the other hand, change in the spectral shape in the OH stretch vibration region shows hydrogen-bonding network of water molecules breaking down rapidly as the IL is added. Trends in the change of the peak positions and the peak intensities suggested qualitative change of the intermolecular structure in the [BMIM][BF4] + H2O mixture at 32 +/- 2 and 45 +/- 2 mol/L of water concentration.