Molecular beam resonant two-photon ionization study of caffeine and its hydrated clusters

We investigated electronically excited states of caffeine and its 1:1 complex with water by using resonant two-photon ionization (R2PI) and UV-UV hole-burning techniques. Strong vibronic coupling between a pair of close-lying pi-pi* and n-pi* transitions is proposed to be responsible for the broad spectral feature observed. By comparing the experimental results with those of theoretical calculations, both the O-bonded and N-bonded forms were suggested to be initially produced for the 1:1 complex. The electronic transitions of the O-bonded complex were blueshifted in the R2PI spectrum. For the N-bonded complex, the excited state undergoes an ultrafast decay process, followed by dissociation on a repulsive potential energy surface, which gives rise to a characteristically anomalous cluster distribution in nanosecond experiments.     

Synthesis of perpendicular nanorod arrays with hierarchical architecture and water slipping superhydrophobic properties

The utilization of vertically aligned smooth gold nanorod arrays with and without nanoporous tip architectures as superhydrophobic surfaces is described. Nanoporous architecture was produced on the tips of nanorods by selectively dissolving less noble components from the alloy nanorods. The resulting nanoscopic dual-size roughness features enhanced the surface dewettability after surface modification with low-surface-energy materials such as long-chain normal alkanethiols and fluorinated organic compounds. The surface cleaning properties were also tested with a rolling water droplet.     

Superprotonic Conductivity of MOFs Confining Zwitterionic Sulfamic Acid as Proton Source and Conducting Medium

A few metal–organic frameworks (MOFs), which typically use strong acids as proton sources, display superprotonic conductivity (≈10⁻¹ S cm⁻¹); however, they are rare due to the instability of MOFs in highly acidic conditions. For the first time, we report superprotonic conductivity using a moderately acidic guest, zwitterionic sulfamic acid (HSA), which is encapsulated in MOF-808 and MIL-101. HSA acts not only as a proton source but also as a proton-conducting medium due to its extensive hydrogen bonding ability and zwitterion effect. A new sustained concentration gradient method results in higher HSA encapsulation compared to conventional methods, producing 10HSA@MOF-808-(bSA)₂ and 8HSA@MIL-101. These MOFs show impressive superprotonic conductivity of 2.47×10⁻¹ and 3.06×10⁻¹ S cm⁻¹, respectively, at 85 °C and 98 % relative humidity, and maintain stability for 7 days.     

Dependence of the closed-shell repulsive interaction on the overlap of the electron densities

The relationship between the closed-shell repulsive interactions and overlap of the electron densities is investigated. It is found that the repulsive interactions vary in almost direct proportion to the absolute size of the density overlaps.     

Tuning the Redox Properties of a Nonheme Iron(III)–Peroxo Complex Binding Redox‐Inactive Zinc Ions by Water Molecules

Redox‐inactive metal ions play important roles in tuning chemical properties of metal–oxygen intermediates. Herein we report the effect of water molecules on the redox properties of a nonheme iron(III)–peroxo complex binding redox‐inactive metal ions. The coordination of two water molecules to a Zn²⁺ ion in (TMC)Fe^III‐(O₂)‐Zn(CF₃SO₃)₂ ( 1 ‐Zn²⁺) decreases the Lewis acidity of the Zn²⁺ ion, resulting in the decrease of the one‐electron oxidation and reduction potentials of 1 ‐Zn²⁺. This further changes the reactivities of 1 ‐Zn²⁺ in oxidation and reduction reactions; no reaction occurred upon addition of an oxidant (e.g., cerium(IV) ammonium nitrate (CAN)) to 1 ‐Zn²⁺, whereas 1 ‐Zn²⁺ coordinating two water molecules, (TMC)Fe^III‐(O₂)‐Zn(CF₃SO₃)₂‐(OH₂)₂ [ 1 ‐Zn²⁺‐(OH₂)₂], releases the O₂ unit in the oxidation reaction. In the reduction reactions, 1 ‐Zn²⁺ was converted to its corresponding iron(IV)–oxo species upon addition of a reductant (e.g., a ferrocene derivative), whereas such a reaction occurred at a much slower rate in the case of 1 ‐Zn²⁺‐(OH₂)₂. The present results provide the first biomimetic example showing that water molecules at the active sites of metalloenzymes may participate in tuning the redox properties of metal–oxygen intermediates.     

Microchip electrophoretic separation for the fast diagnosis of Anaplasma phagocytophilum infection in cattle

We report a diagnostic method for Anaplasma phagocytophilum (A. phagocytophilum) infection in cattle using a nested PCR and microchip electrophoresis (ME). A. phagocytophilum causes human granulocytic anaplasmosis and granulocytic ehrlichiosis, which are emerging tick‐borne zoonotic diseases. Nested PCR was used to amplify genomic DNA samples extracted from cattle blood. The amplified PCR products were analyzed under a sieving gel matrix of 0.7% poly(ethyleneoxide) (M_r=8 000 000) in a conventional glass microchip. In the ME assay, A. phagocytophilum was analyzed within 35 s with a relative standard deviation of 1.30% (n=5) using a programmed field strength gradient (PFSG) as follows: 615.3 V/cm for 0–24 s, 66.7 V/cm for 24–34 s, 615.3 V/cm for 34–100 s. The ME‐PFSG assay was clinically validated by comparing the 16S rRNA gene levels obtained by this method with those measured using conventional slab gel electrophoresis performed with ten cattle blood samples suspected of A. phagocytophilum infection. In contrast to slab gel electrophoresis, the proposed ME‐PFSG methodology had increased sensitivity (200–450 pg/μL), a faster analysis time (<35 s), and required a smaller sample volume (～162 fL).     

Aspirin attenuates the anti-inflammatory effects of theophylline via inhibition of cAMP production in mice with non-eosinophilic asthma

Theophylline is commonly used to treat severe asthma and chronic obstructive pulmonary disease (COPD) characterized by non-eosinophilic inflammation. Acetyl salicylic acid (ASA) is one of the most widely used medications worldwide, but up to 20% of patients with asthma experience aggravated respiratory symptoms after taking ASA. Here we evaluated the adverse effect of ASA on the therapeutic effect of theophylline in mice with non-eosinophilic asthma. A non-eosinophilic asthma mouse model was induced by airway sensitization with lipopolysaccharide-containing allergen and then challenged with allergen alone. Therapeutic intervention was performed during allergen challenge. Theophylline inhibited lung inflammation partly induced by T_h1 immune response. ASA attenuated the beneficial effects of theophylline. However, co-administration of the ASA metabolite salicylic acid (SA) showed no attenuating effect on theophylline treatment. The therapeutic effect of theophylline was associated with increase in cAMP levels, which was blocked by co-treatment of theophylline and ASA. ASA co-treatment also attenuated the anti-inflammatory effects of a specific phosphodiesterase 4 inhibitor. These results demonstrate that ASA reverses anti-inflammatory effects of theophylline, and that ASA exerts its adverse effects through the inhibition of cAMP production. Our data suggest that ASA reverses lung inflammation in patients taking theophylline, although clinical evidence will be needed.     

Effect of layer structures of gold nanoparticle films on surface enhanced Raman scattering

Using a method of collecting nanoparticles at a water/hexane interface in a close-packed monolayer film and transferring such films onto a solid substrate, three-dimensional multilayer films of nanoparticles were formed. The packed nanoparticles were gold nanospheres (NS) with a 26 nm diameter or gold nanorods (NR) with a 31 nm diameter and 74 nm length. We investigated variations in the surface enhanced Raman scattering (SERS) intensities from such nanoparticle films as the layer compositions were changed. The films stacked with NR layers generated much higher SERS intensity than those of NS layers. The SERS intensities from both kinds of films increased as the number of layers were increased. However, when the NR layer and NS layer were stacked alternately, SERS intensity varied in a zigzag fashion. It was found that the structure of top layer plays a distinguishable role in generating strong SERS enhancement while the lower layers contribute to SERS with less dependency on structures. Interlayer coupling as well as intralayer coupling was considered in order to explain the observations.