TEMPO addition into pre-irradiated fluoropolymers and living-radical graft polymerization of styrene for preparation of polymer electrolyte membranes

We prepared proton exchange membranes (PEMs) by 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO)-mediated living-radical graft polymerization (LRGP) of styrene into fluoropolymer films and subsequent sulfonation. Poly(vinylidene fluoride) (PVDF) and poly(ethylene-co-tetrafluoroethylene) (ETFE) films were first irradiated and then treated with TEMPO solutions in various solvents. TEMPO addition was confirmed by the test of styrene grafting into TEMPO-treated films at 60 °C, at which the LRGP never proceeds. This test enabled us to differentiate the LRGP from the conventional graft polymerization. In order to gain a deep insight about TEMPO-addition reaction, the TEMPO-penetration behavior into the base polymer films was examined by a permeation experiment and computer simulation. Xylene and dioxane were appropriate solvents for the complete introduction of TEMPO into PVDF and ETFE films, respectively. Then, the LRGP of styrene was performed based on the fully TEMPO-capped films at 125 °C with various solvents. By using an alcoholic solvent, the degree of grafting was enhanced and it reached a maximum of 38%. This grafted film was sulfonated to prepare a PEM showing an ion exchange capacity of 2.2 meq/g and proton conductivity of 1.6×10^?1 S/cm.     

Proving and Probing the Presence of the Elusive C−H⋅⋅⋅O Hydrogen Bond in Liquid Solutions at Room Temperature

Hydrogen bonds (H bonds) play a major role in defining the structure and properties of many substances, as well as phenomena and processes. Traditional H bonds are ubiquitous in nature, yet the demonstration of weak H bonds that occur between a highly polarized C?H group and an electron‐rich oxygen atom, has proven elusive. Detailed here are linear and nonlinear IR spectroscopy experiments that reveal the presence of H bonds between the chloroform C?H group and an amide carbonyl oxygen atom in solution at room temperature. Evidence is provided for an amide solvation shell featuring two clearly distinguishable chloroform arrangements that undergo chemical exchange with a time scale of about 2 ps. Furthermore, the enthalpy of breaking the hydrogen bond is found to be 6–20 kJ mol^?1. Ab‐initio computations support the findings of two distinct solvation shells formed by three chloroform molecules, where one thermally undergoes hydrogen‐bond making and breaking.     

Involvement of JNK-initiated p53 accumulation and phosphorylation of p53 in pseudolaric acid B induced cell death

A terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) assay was used to determine that apoptosis causes HeLa cell death induced by pseudolaric acid B. The c-Jun N-terminal kinase (JNK) inhibitor SP600125 decreased p53 protein expression during exposure to pseudolaric acid B. SP600125 decreased the phosphorylation of p53 during pseudolaric acid B exposure, indicating that JNK mediates phosphorylation of p53 during the response to pseudolaric acid B. SP600125 reversed pseudolaric acid B-induced down-regulation of phosphorylated extracellular signal-regulated protein kinase (ERK), and protein kinase C (PKC) was activated by pseudolaric acid B, whereas staurosporine, calphostin C, and H7 partly blocked this effect. These results indicate that p53 is partially regulated by JNK in pseudolaric acid B-induced HeLa cell death and that PKC participates in pseudolaric acid B-induced HeLa cell death.     

Quantification of methamphetamine, amphetamine and enantiomers by semi-micro column HPLC with fluorescence detection; applications on abusers' single hair analyses

Achiral and chiral semi-micro column high-performance liquid chromatographic methods with fluorescence detection to determine methamphetamine and amphetamine in human hair are described. These compounds were extracted into 5% trifluoroacetic acid (TFA) in methanol, derivatized with 4-(4,5-diphenyl-1H-imidazol-2-yl)-benzoyl chloride and separated either on a 250 x 1.5 mm i.d. octadecyl-silane (ODS) or a 150 x 2 mm i.d. OD-RH column. Linear calibration curves extending over a wide range of concentration that covers the practical samples were obtained for amphetamine, methamphetamine and their enantiomers (r = 0.999). Resolution values for amphetamine and methamphetamine enantiomers were 3.4 and 1.1, respectively. Intra- and inter-day variations of both the methods were not larger than 8.9% expressed as relative standard deviations (n >/= 5). The limits of detection at a signal-to-noise ratio of 3 obtained by both the methods were in the range of 1.0-4.7 fmol/5 microL injection with the achiral method being more sensitive. Abusers' hair samples were analyzed by the two methods and only the S(+)-enantiomers were found in eight Japanese abusers' hair samples. The achiral method was used to study the concentrations of these compounds in single black and white hair strands of abusers.     

Evaluation of microwave-assisted extraction for the analysis of organophosphorus and pyrethroid pesticides in green onions

The aim of this study was to evaluate the efficiency of microwave-assisted extraction (MAE) for the analysis of organophosphorus (OP) and pyrethroid (PYR) pesticides in green onions by GC/MS. We optimized MAE extraction solvent, temperature, and time by using a certified reference material. As a result, the concentrations of two OP and two PYR target pesticides obtained by MAE with acetonitrile at 110 degrees C for 10 min were in good agreement with certified concentrations and comparable to the results by homogenization used as reference extraction technique. When the recovery test, performed by spiking the target pesticides into blank samples (5.0 g), was carried out with our optimized MAE conditions, mean recoveries of 16 OP and 10 PYR pesticides were 72-108% for a 1.0 pg spiking level and 70-119% for a 0.2 microg level. These results were acceptable according to the validation guideline for testing method of agricultural chemicals in food by Ministry of Health, Labour, and Welfare in Japan. The results suggested that MAE can be used for the analysis of OP and PYR pesticides in green onions.     

Ultrafast structural dynamics of in-cage isomerization of diiodomethane in solution

Despite extensive studies on the isomer species formed by photodissociation of haloalkanes in solution, the molecular structure of the precursor of the isomer, which is often assumed to be a vibrationally hot isomer formed from the radical pair, and its in-cage isomerization mechanism remain elusive. Here, the structural dynamics of CH₂I₂ upon 267 nm photoexcitation in methanol were probed with femtosecond X-ray solution scattering at an X-ray free-electron laser. The determined molecular structure of the transiently formed species that converts to the CH₂I–I isomer has the I–I distance of 4.17 Å, which is longer than that of the isomer (3.15 Å) by more than 1.0 Å and the mean-squared displacement of 0.45 Ų, which is about 100 times larger than those of typical regular chemical bonds. These unusual structural characteristics are consistent with either a vibrationally hot form of the CH₂I–I isomer or the loosely-bound radical pair (CH₂I˙⋯I˙).

The structural dynamics of in-cage isomerization of CH₂I₂ and the unusual structure of the loosely-bound isomer precursor were unveiled with femtosecond X-ray liquidography (solution scattering).     

Highly regioselective hydroiodination of terminal alkynes and silylalkynes with iodine and phosphorus reagents leading to internal iodoalkenes

Markovnikov-type hydroiodination of terminal alkynes with iodine and Ph₂P(O)H took place selectively to afford the corresponding internal iodoalkenes in good yields. Combination of (PhO)₂P(O)H and Ph₂P(O)OH instead of Ph₂P(O)H also provided internal iodoalkenes in excellent yields. This hydroiodination is advantageous in terms of mild conditions, convenient operation, and tolerance to various functional groups. In addition, direct synthesis of internal iodoalkenes from silylalkynes was also achieved by using a mixed system of iodine and phosphorus reagents.