Electrocatalytic nitrate hydrogenation over an H+ -conducting solid polymer electrolyte membrane-modified cathode assembly

Selective electrocatalytic hydrogenation of NO3- to N2 in water has successfully been achieved at room temperature using a membrane-electrode assembly (MEA) consisting of an H+ -conducting solid polymer electrolyte (Nafion-117) and a surface-modified Pt cathode.     

Site-specific transition of cytosine to uracil via reversible DNA photoligation

We report that deamination coupled with 5-carboxyvinyldeoxyuridine-mediated photobranching causes the heat-induced transition of cytosine to uracil with high efficiency without any side reaction.     

Structure-directing agent location and non-centrosymmetric structure of fluoride-containing zeolite SSZ-55

Single crystals of pure silica zeolite SSZ-55 were prepared using the fluoride route. Single-crystal X-ray diffraction at a synchrotron source revealed the framework structure of the material, but the unit cell (orthorhombic a = 12.905(2) A, b = 21.344(4) A, c = 5.1279(10)) is too small to accommodate ordered arrays of the organic structure-directing agent. Molecular modeling was used to simulate the docking of the structure-directing agent in the channels of the material, and this revealed a strong space-filling interaction with a number of possible orientations of the organic cation. The overall non-centrosymmetric structure of the solid (spacegroup C222(1)) was confirmed using second harmonic generation experiments.     

10 kHz 40 W Ti:sapphire regenerative ring amplifier

A cryogenically cooled Ti:sapphire regenerative ring amplifier was developed as a laser for generating a laser-produced plasma light source. With a 10 kHz 180 W pump laser, the amplifier output is 40 W before compression and 26 W after compression. We believe it to be the current highest average-power output from a single stage Ti:sapphire amplifier. The effective focal length of the thermal lens is measured to be 2.2 m at 100 K for 180 W of pump power. With a 1 m focal length lens placed in the resonator, the effect of a thermal lens on the resonator mode is suppressed. High conversion efficiency is achieved for the whole pumping power range without any additional measures for thermal compensation.     

Generalized two-dimensional correlation analysis of NMR and Raman spectra for structural evolution characterizations of silk fibroin

Generalized two-dimensional (2D) correlation spectroscopy was used to characterize the structural evolution of silk fibroin as the pH changed from 6.8 to 4.8, demonstrating that the conformational transitions of silk fibroin are induced step by step as the pH decreases. 2D homo- and hetero-spectral correlation spectroscopy was used to establish the relationship between information extracted from NMR and Raman spectroscopy. This novel method reveals the structural evolution using two probes with different frequency scales (10(5-9) Hz for nuclear spin motion and 10(12-14) Hz for molecular vibration motion), reflecting the different spatial scale sensitivity to the molecular conformational change. The transition order is identified as silk I state (helix dominant) --> silk I intermediate state --> silk II intermediate state --> silk II state (beta-sheet dominant), as the pH decreases. The results may rationalize the silkworm spinning process, which undergoes the conformational transition steadily from the soluble helix state to the insoluble beta-sheet state as the pH decreases from the posterior to anterior glands.     

Angle-dependent terahertz time-domain spectroscopy of amino acid single crystals

The measurement of absorption spectra using angle-dependent terahertz (THz) time-domain spectroscopy for amino acid single crystals of l-cysteine and l-histidine is reported for the first time. Linearly polarized THz radiation enables us to observe angle-dependent far-infrared absorption spectra of amino acid single crystals and determine the direction of the oscillating dipole of the molecules in the 20-100 cm(-1) range. By comparing the THz spectra of a single crystal and powder, we found that there was a clear hydrogen-bond peak in the crystal spectrum as a result of the larger hydrogen-bond network. The low-temperature THz spectra of amino acid microcrystals showed more intermolecular vibrational modes than those measured at room temperature. An ab initio frequency calculation of a single amino acid molecule was used to predict the intramolecular vibrational modes. The validity of the calculation models was confirmed by comparing the results with experimentally obtained data in the Raman spectral region.     

One-pot synthesis of N-substituted diaza[12]annulenes

N-Substituted diaza[12]annulenes are obtained by one -pot reaction of N-(2,4-dinitrophenyl)pyridinium chloride with amines in moderate to high yields. The 1H NMR spectrum reveals that diamagnetic ring current is generated in the diaza[12]annulene ring. The N-substituted diaza[12]annulenes are electrochemically active in solution.     

Formation and Reactivity of a Molecular Magnesium Hydride with a Terminal MgH Bond

A complex featuring a terminal magnesium hydride bond supported by an NNNN macrocyclic ligand, [Mg{Me₃TACD ? Al(iBu)₃}H] ( 3 ), was formed from its labile Al(iBu)₃ adduct. Use of Al(iBu)₃ to block the amido nitrogen of the NNNN macrocyclic ligand was essential to prevent aggregation. The structurally characterized compound 3 reacted with BH₃ to give the BH₄ derivative, whereas Me₃SiC?CH and PhSiH₃ led to the corresponding acetylide and silyl derivative under H₂ elimination. Pyridine is inserted into the Mg?H bond to give selectively the 1,4‐dihydropyridinate.     

Polycyclic N‐Heterocyclic Compounds 73: Synthesis and Evaluation of 5‐Substituted 1,2‐Dihydrofuro[2,3‐c]isoquinolines as Inducers of Lipoprotein Lipase mRNA Expression

Several 5‐substituted 1,2‐dihydro[2,3‐c]isoquinoline derivatives were synthesized as part of our research to develop new diabetes drugs. Amines and sulfanyls were used as substituents at the 5th‐position. Evaluation of the effects of the newly synthesized compounds on lipoprotein lipase mRNA expression in 3T3‐L1 preadipocytes revealed one promising candidate with potency comparable to that of troglitazone.