Activation of JNK and p38 in rat hippocampus after kainic acid induced seizure

Kainic acid, an analogue of glutamate, causes limbic seizures and induces cell death in the rat brain. We examined the activation of MAPK family kinases; ERKs, JNKs and p38 kinase in rat hippocampus after KA treatment. Activation of all three kinases were observed at 30 min after the treatment, but, in contrary to ERK phosphorylation, which lasted up to 3 h, the phosphorylation of JNK and p38 returned to the basal level by 2 h. The phosphorylation of' upstream kinases for the MAPK family was distinct. The phosphorylation of MEK1 clearly increased at 30 min but diminished rapidly thereafter. The phosphorylation of MKK6 was also increased but reached peak at 2 h after KA treatment. However, the phosphorylation of other upstream kinases, SEK1 and MKK3, gradually decreased to 3 h after KA treatment. These results indicate that the KA activates all of the three MAPK family kinases with different time patterns and suggest the possibility that MKK3 and MKK6, and SEK1 may not be the upstream kinases for p38 and JNK in rat hippocampus.     

Molecular dynamics simulations of layer-by-layer assembly of polyelectrolytes at charged surfaces: effects of chain degree of polymerization and fraction of charged monomers

We performed molecular dynamics simulations of the electrostatic assembly of multilayers of flexible polyelectrolytes at a charged surface. The multilayer build-up was achieved through sequential adsorption of oppositely charged polymers in a layer-by-layer fashion from dilute polyelectrolyte solutions. The steady-state multilayer growth proceeds through a charge reversal of the adsorbed polymeric film which leads to a linear increase in the polymer surface coverage after completion of the first few deposition steps. Moreover, substantial intermixing between chains adsorbed during different deposition steps is observed. This intermixing is consistent with the observed requirement for several deposition steps to transpire for completion of a single layer. However, despite chain intermixing, there are almost perfect periodic oscillations of the density difference between monomers belonging to positively and negatively charged macromolecules in the adsorbed film. Weakly charged chains show higher polymer surface coverage than strongly charged ones.     

An efficient synthesis of 3(S)-aminopiperidine-5(R)-carboxylic acid as a cyclic β,γ′-diamino acid

An orthogonally protected β,γ′-diamino acid 6 possessing conformationally-constrained ring system was synthesized as a novel cyclic amino acid analogue. This synthesis involves as key steps chemoselective enzymatic hydrolysis of cis-piperidine-3,5-dicarboxylic ester derivative followed by efficient kinetic resolution of the partially resolved half-acid to afford the C₁-symmetric piperidine-3,5-dicarboxylic acid monoester in high enantiomeric excess (>98% ee). The optically active half-acid was transformed to the cyclic amino acid via Curtius-type rearrangement.     

Molecular two-photon sensor for metal ions derived from bis(2-pyridyl)amine

A molecular two-photon sensor for the metal ions derived from bis(2-pyridyl)amine as the receptor is reported. The sensor emits strong two-photon fluorescence when excited by 780 nm laser photons. Moreover, the binding constants measured by the one- and two-photon fluorescence are similar. This result may be useful for the design of efficient two-photon fluorescence probe for biological substrates.     

Noncontact temperature measurement in microliter-sized volumes using fluorescent-labeled DNA oligomers

A new method of noncontact temperature measurement in microliter-sized volumes is demonstrated, based on the temperature sensitivity of the fluorescence lifetime of rhodamine-G when it is attached to a DNA oligomer. As temperature changes, the spacing between the fluorescent dye and a designed sequence of DNA bases is modulated by conformation changes of the DNA chain, and as a result the ability of dye molecules to fluoresce is also modulated according to differential quenching by bases on the DNA. In the system that we studied, the temperature sensitivity of the fluorescence lifetime was 36-42 ps/ degrees C depending on specific solution conditions. Although this strategy of temperature measurement is demonstrated using a specific sequence of DNA, it can also be generalized to a dye attached to any other intrinsic quencher of fluorescence whose conformation changes with temperature.     

Chloromethanesulfonylethene and dichloromethanesulfonylethene: new reagents for tandem Diels-Alder/Ramberg-Bäcklund reactions

[reaction: see text] Chloromethanesulfonylethene (3a) and dichloromethanesulfonylethene (3b) were prepared by oxidation of the adducts of ethylene and ClCH(2)SCl or Cl(2)CHSCl, respectively, followed by NaHCO(3) dehydrochlorination. With dienes, 3a gave Diels-Alder adducts that, with base, underwent Ramberg-B?cklund reaction, giving products corresponding to the adducts of the dienes and allene. Similarly, 3b gave Diels-Alder adducts that, with base in the presence of the novel chlorine source MeSO(2)CCl(3), cleanly afforded products corresponding to the adducts of the dienes and 1,1-dichloropropa-1,2-diene.     

Stable pi-dimer of a tetrathiafulvalene cation radical encapsulated in the cavity of cucurbit[8]uril

The first stable pi-dimer of a tetrathiafulvalene (TTF) cation radical encapsulated in the cavity of cucurbit[8]uril has been isolated at room temperature and fully characterized; it shows absorption bands at 400, 540 and 760 nm, characteristic of the TTF cation radical dimer.     

Temporary inactivation of plasma amine oxidase by alkylhydrazines. A combined enzyme/model study implicates cofactor reduction/reoxidation but cofactor deoxygenation and subsequent reoxygenation in the case of hydrazine itself

It has been known for some time that hydrazine and its methyl and 1,1-dimethyl analogues induce inactivation of the copper-containing quinone-dependent plasma amine oxidase but that the activity recovers over time, suggesting metabolism of all three inhibitors. However, the mechanism responsible for loss and regain of activity has not been investigated. In this study a combination of enzyme studies under a controlled atmosphere along with model studies using 5-tert-butyl-2-hydroxy-1,4-benzoquinone to mimic the 2,4,5-trihydroxyphenylalanine quinone (TPQ) cofactor of the enzyme suggest that regain of enzyme activity represents two different O(2)-dependent processes. In the case of methylhydrazine and 1,1-dimethylhydrazine, we propose that the inactive methylhydrazone/azo form of the enzyme slowly rehydrates and eliminates MeN=NH to give the triol cofactor form, which instantly reoxidizes to the catalytically active quinone form in the presence of O(2). Metabolism of methylhydrazine represents its conversion to CH(4) and N(2), and of 1,1-dimethylhydrazine to CH(2)=O, CH(4), and N(2). In the case of hydrazine itself, however, we propose that the inactive hydrazone/azo form of the enzyme instead undergoes a slow decomposition, probably facilitated by the active-site copper, to give N(2) and a novel 5-desoxy resorcinol form of the cofactor. The latter undergoes a rapid, but noninstantaneous reoxygenation at C5 to restore the active cofactor form, also probably mediated by the active-site copper.     

Analysis of problematic complexing behavior of ferric chloride with N,N-dimethylformamide using combined techniques of FT-IR,XPS, and TGA/DTG

A problematic coordination behavior of highly hygroscopic FeCl(3) in DMF solution was studied. From the compositional and structural analyses for the adduct of FeCl(3)/DMF using various techniques such as FTIR, elemental analysis, UV/vis, XPS, and TGA/DTG, it was found that the iron cation exists in the form of an Fe(3+) cation and coordinates via the carbonyl oxygen atom of amide bond in DMF. The analyses of both FT-IR and XPS C 1s spectra for the adduct revealed that 2.1 molecules of DMF coordinate with a more electron-deficient Fe(3+); otherwise 1.2 molecules of DMF coordinated with a relatively electron-rich Fe(3+). The Cl 2p spectrum indicated that the electron-deficient Fe(3+) coordinated with two chlorine ions and the electron-rich Fe(3+) with four chlorines so that the chemical formula of the adduct is of [FeCl(2)(DMF)(1.2)(H(2)O)(2.7)](+)[FeCl(4)(DMF)(2.1)](-). The water molecules in the adduct were found chemisorbed rather than physisorbed, with a singular binding energy.     

Cesium release during high-temperature pre-treatment of fuel fragments with a burn-up of 61 GWd/tU

The electrolytic reduction process in pyroprocessing of used fuel requires that fuel fragments be pre-treated to remove cesium and iodine. The effect of high temperatures and fuel fragment size on release of cesium was investigated over 10 h at a temperature of 1300–1400 °C for fuel fragments with an O/U ratio of 2.2. Re-fragmentation of the original fragments was observed as changes in cesium release count rates as fuel was heated from 484 to 1329 °C. The release of cesium is highly dependent on the size of fuel fragments and most of the cesium is released as the temperature is held at the maximum target value.