Single-nanometer focusing of hard x-rays by Kirkpatrick-Baez mirrors

We have constructed an extremely precise optical system for hard-x-ray nanofocusing in a synchrotron radiation beamline. Precision multilayer mirrors were fabricated, tested, and employed as Kirkpatrick-Baez mirrors with a novel phase error compensator. In the phase compensator, an at-wavelength wavefront error sensing method based on x-ray interferometry and an in situ phase compensator mirror, which adaptively deforms with nanometer precision, were developed to satisfy the Rayleigh criterion to achieve diffraction-limited focusing in a single-nanometer range. The performance of the optics was tested at BL29XUL of SPring-8 and was confirmed to realize a spot size of approximately 7 nm.     

Effects of protonation of pyridine moieties on the 2D assembly of porphyrin layers on Au(111) at electrochemical interfaces

Unique molecular assemblies of a porphyrin derivative are prepared on Au(111) by controlling the protonation/unprotonation of the pyridine groups. The porphyrin derivative, driven by the protonation of the pyridine groups, can provide characteristic assemblies with specific molecular conformations on an Au(111) surface at the electrochemical interface. In situ scanning tunneling microscopy images revealed clear differences in the adlayer structures for the unprotonated and the protonated forms of the molecules that depended upon the electrochemical potential.     

Domino-Redox Reaction Induced by An Electrochemically Triggered Conformational Change

The concept of a domino-type reaction has been applied in a wide range of fields such as synthetic organic chemistry, material engineering, and life science. To extend the domino concept to redox chemistry, we designed and synthesized a dimeric quinodimethane (QD) with a nonplanar dithiin spacer. The domino-redox properties can be activated by raising the temperature, based on a thermally equilibrated twisted conformation of QD, which has a higher HOMO level that is more readily oxidized. After one QD unit is oxidized (trigger), steric repulsion and electronic interaction between electrophores make the neighboring QD unit adopt a twisted conformation (domino process), which facilitates the following oxidation. Thus, a domino-redox reaction was achieved for the first time by a change in the HOMO level due to a drastic change in the molecular conformation.     

Highly sensitive capillary electrophoresis analysis of N-linked oligosaccharides in glycoproteins following fluorescence derivatization with rhodamine 110 and laser-induced fluorescence detection

We describe a highly sensitive CE with laser-induced fluorescence (LIF) detection for the analysis of N-linked oligosaccharides in glycoproteins using rhodamine 110 as a fluorescence derivatization reagent. One CE separation is performed using a fused-silica capillary and neutral pH buffer conditions and allows for the separation of sialo-oligosaccharides according to the number of sialic acids. An alternate separation is performed using the same capillary and acidic pH buffer conditions, enabling the separation of asialo-oligosaccharides according to their sizes. The derivatization and separation conditions for the analysis of sialo- and asialo-oligosaccharides were optimized. Furthermore, we applied the proposed method for the analyses of N-linked sialo- and asialo-oligosaccharides in glycoproteins (ribonuclease B, fetuin, and recombinant human erythropoietin).     

Antioxidant and Antimicrobial Activities of Thai Edible Plant Extracts Prepared Using Different Extraction Techniques

This study investigated the antioxidant and antimicrobial activities of six Thai edible plant leaf extracts, including Cashew (CN), Chamuang (CM), Monpu (MP), Thurianthet (TT), Kradon (KD) and Pakliang (PL), extracted using ethanol extraction (EE), microwave-assisted extraction (MAE), and ultrasonic-assisted extraction (UAE). The leaf extracts were characterized for percentage yield, total phenolic content (TPC), total flavonoid content (TFC), 2,2-diphenyl-1-picrylhydrazyl (DPPH) and-ferric reducing antioxidant power (FRAP) activity, and antimicrobial activity against spoilage. MAE produced the highest percentage yields, among which MAE-extracted MP exhibited the highest yield. Furthermore, the highest TPC and TFC were obtained for MAE, with MAE-extracted KD and CN showing the highest TPC and TFC, respectively, among the samples. The highest DPPH and FRAP values were seen in MAE-processed CN, KD, and MP extracts. The inhibition zone of pathogenic bacteria, minimum inhibitory concentration, and minimum bacterial concentration were determined in all samples except TT. These findings indicate that, compared to EE and UAE, MAE improved the antioxidant and antimicrobial efficacy of the leaf extracts. The aforementioned extracts could be employed as natural food additives to prevent chemical and microbial spoilage of foods.     

Riboflavin‐Based Fluorogenic Sensor for Chemo‐ and Enantioselective Detection of Amine Vapors

A novel turn‐on fluorogenic chiral sensory system has been developed using a protonated riboflavin and riboflavin‐derived cationic polymer as a fluorophore precursor and a specific amine receptor, respectively, which enables the solid‐state chemo‐ and enantioselective fluorogenic visual detection of primary and secondary amine vapors.     

Continuous-flow analysis for ethanol with immobilized alcohol dehydrogenase

Alcohol dehydrogenase is immobilized by reaction with glutaraldehyde onto silica gel, which is packed in a column in a flow system. Ethanol (0.1–5 mmol) is determined by catalysis of the reaction with NAD⁺, the NADH produced being detected amperometrically. The reproducibility is ca. 1%.     

Formation of supramolecular nanobelt arrays consisting of cobalt(II) "picket-fence" porphyrin on Au surfaces

Adlayers of cobalt(II) 5,10,15,20-tetrakis(alpha,alpha,alpha,alpha-2-pivalamidophenyl)porphyrin (CoTpivPP) were prepared by immersing either Au(111) or Au(100) substrate in a benzene solution containing CoTpivPP molecules, and they were investigated in 0.1 M HClO4 and 0.1 M H2SO4 by cyclic voltammetry and in situ scanning tunneling microscopy (STM). The adlayer structure and electrochemical properties of CoTpivPP are compared to those of 5,10,15,20-tetraphenyl-21H,23H-porphine cobalt(II) (CoTPP). Characteristic nanobelt arrays consisting of CoTpivPP molecules were produced on both Au(111) and Au(100) surfaces. The stability of the nanobelt arrays was controlled by manipulating the electrode potential. On the other hand, the formation of nanobelt arrays consisting of O2-adducted CoTpivPP molecules depended upon the crystallographic orientation of Au. The state of O2 trapped in the cavity of CoTpivPP was distinctly observed in STM images as a bright spot in the nanobelt array formed on reconstructed Au(100)-(hex) surface, but not on Au(111) surface. This result suggests that the arrangement of underlying Au atoms plays an important role in the formation of nanobelt arrays with the sixth ligand coordination.     

Main-chain optically active riboflavin polymer for asymmetric catalysis and its vapochromic behavior

A novel optically active polymer consisting of riboflavin units as the main chain (poly-1) was prepared from naturally occurring riboflavin (vitamin B(2)) in three steps. The riboflavin residues of poly-1 were converted to 5-ethylriboflavinium cations (giving poly-2), which could be reversibly transformed into the corresponding 4a-hydroxyriboflavins (giving poly-2OH) through hydroxylation/dehydroxylation reactions. This reversible structural change was accompanied by a visible color change along with significant changes in the absorption and circular dichroism (CD) spectra. The nuclear Overhauser effect spectroscopy (NOESY) and CD spectra of poly-2 revealed a supramolecularly twisted helical structure with excess one-handedness through face-to-face stacking of the intermolecular riboflavinium units, as evidenced by the apparent NOE correlations between the interstrand riboflavin units and intense Cotton effects induced in the flavinium chromophore regions. The hydroxylation of poly-2 at the 4a-position proceeded in a diastereoselective fashion via chirality transfer from the induced supramolecular helical chirality assisted by the ribityl pendants, resulting in a 83:17 diastereomeric mixture of poly-2OH. The diastereoselectivity of poly-2 was remarkably higher than that of the corresponding monomeric model (64.5:35.5), indicating amplification of the chirality resulting from the supramolecular chirality induced in the stacked poly-2 backbones. The optically active poly-2 efficiently catalyzed the asymmetric organocatalytic oxidation of sulfides with hydrogen peroxide, yielding optically active sulfoxides with up to 60% enantiomeric excess (ee), whose enantioselectivity was higher than that catalyzed by the monomeric counterpart (30% ee). In addition, upon exposure to primary and secondary amines, poly-2 exhibited unique high-speed vapochromic behavior arising from the formation of 4a-amine adducts in the film.     

Imaging the Belousov-Zhabotinsky reaction in real time using an ion sensitive array

We show how an array of ion-sensitive-field-effect-transistors can be used to both spatially and temporally image the oscillating pH/ion waves produced by the Belousov-Zhabotinsky (BZ) reaction with high resolution.