Ion/molecule reactions in the orifice-skimmer region of an atmospheric pressure Penning ionization mass spectrometer

Atmospheric pressure Penning ionization mass spectra of methanol were measured as functions of Ar or He gas pressure in the first vacuum chamber, the position of the skimmer, and the voltage applied between the orifice and the skimmer. When the orifice and the skimmer were coaxial with a distance of 4 mm, the distribution of CH3OH2+(CH3OH)n clusters was only weakly dependent on both Ar pressure (in the range of 19-220 Pa) and orifice-skimmer voltage (in the range of 1-45 V). The ion/molecule reaction CH3OH2+ + CH3OH --> CH3+(CH3OH) + H2O was observed in the free jet expansion, especially at high orifice-skimmer voltage values. When the orifice and the skimmer were off-centered and the distance between them was increased to 18 mm, the formation of large CH3OH2+(CH3OH)n clusters, as well as their dissociation, were seen. The endothermic proton transfer reaction, CH3+(CH3OH) + CH3OH --> CH3OH2+ + CH3OCH3, occurred at high orifice-skimmer voltage. The collision-induced dissociation of cluster ions by He gas in the first vacuum chamber was much more efficient than by Ar. These results demonstrated that the mass spectra are highly dependent on skimmer position and on orifice-skimmer voltage and that ions observed by mass spectrometry do not necessarily reflect the abundance of ions produced in the atmospheric pressure ion source.     

Distribution of <Superscript>137</Superscript>Cs around Kashiwazaki-Kariwa area

Cesium-137 distribution in several rivers, lakes and their sediments was investigated with HPGe detectors to elucidate the source of this isotope in some fresh waters from Kashiwazaki-Kariwa area, Niigata, Japan. It was suggested that there exists a place abundant in fallout radionuclides in the east side of a mountain which is located by the coast. Great westerly monsoon will contribute significantly to this phenomenon, which seems to be characteristic of mountains along the Sea of Japan.     

Surface functionalization chemistries on highly sensitive silica-based sensor chips

The surfaces of silica-based sensor chips, designed for evanescent-field-coupled waveguide-mode sensors, were functionalized using various surface chemistries. The immobilization of molecular entities on the functionalized silica surfaces was monitored using various microscopic techniques (scanning electron, fluorescence, and atomic force microscopies). Further, gold nanoparticle-based signal enhancement analyses were performed with protein conjugation on different functionalized surfaces using a waveguide-mode sensor. Based on these analyses, the sensor surfaces modified with glutaraldehyde (Glu) and carbonyldiimidazole were found to be good for molecules of different sizes. In addition, it can be inferred that the Glu-modified surface may be suitable for small molecules with diameters around 5 nm owing to its surface roughness. The modified surface with carbonyldiimidazole is suitable for the direct immobilization of larger molecules especially for biomolecular assemblies without intermediate chemical modifications.     

Total synthesis of incednam, the aglycon of incednine

The first total synthesis of incednam (1), the aglycon of antibiotic incednine (2), is described. Incednine has been reported to exhibit significant inhibitory activity against the antiapoptotic oncoproteins Bcl-2 and Bcl-xL. The synthesis of 1 commenced with the preparation of the C1-C13 subunit 3 and the C14-C23 subunit 4. The construction of the novel 24-membered macrocycle was achieved by the application of a Stille coupling between 3 and 4, followed by macrolactamization.     

Evaluation of nucleic acid duplex formation on gold over layers in biosensor fabricated using Czochralski-grown single-crystal silicon substrate

With a view to developing an economical and elegant biosensor chip, we compared the efficiencies of biosensors that use gold-coated single-crystal silicon and amorphous glass substrates. The reflectivity of light over a wide range of wavelengths was higher from gold layer coated single-crystal silicon substrates than from glass substrates. Furthermore, the efficiency of reflection from gold layers of two different thicknesses was examined. The thicker gold layer (100 nm) on the single-crystal silicon showed a higher reflectivity than the thinner gold film (10 nm). The formation of a nucleic acid duplex and aptamer–ligand interactions were evaluated on these gold layers, and a crystalline silicon substrate coated with the 100-nm-thick gold layer is proposed as an alternative substrate for studies of interactions of biomolecules.     

Low bending loss and effectively single-mode all-solid photonic bandgap fiber with an effective area of 650 μm2

A large-mode-area all-solid photonic bandgap fiber with a seven-cell core and five high-index rod rings is investigated. Numerical simulations show that an effective area of more than 500 μm(2), a bending loss of less than 0.1 dB/m at a bending radius of 10 cm and effectively single-mode operation can be achieved simultaneously. A core diameter of 44.8 μm and an effective area of 650 μm(2) at 1064 nm are achieved in a fabricated fiber. Bending loss at 1064 nm is 0.09 dB/m at a bending radius of 7 cm. Effectively single-mode operation is also realized at a bending radius of 10 cm.     

Electrosprayed droplet impact/secondary ion mass spectrometry

A new ionization method, electrosprayed droplet impact ionization (EDI), has been developed for mass spectrometry. The charged droplets formed by electrospraying 1 M acetic acid aqueous solution are sampled through an orifice with a diameter of 400 μm into the first vacuum chamber, transported into a quadrupole ion guide and accelerated by 10 kV after exiting the ion guide. The m/z of the primary droplet projectiles range from 10 000 to 50 000. The droplets impact on a dry solid sample deposited on a stainless steel substrate. No matrix was used for the sample preparation. The secondary ions formed by the impact are transported to a second quadrupole ion guide and mass-analyzed by an orthogonal TOF-MS. Intense molecular-related ions are detected for drugs, amino acids, peptides and proteins. EDI is found to be very sensitive to molecules present near the surface of the sample.     

Strain amplification of the 4k_(F) chain instability in Sr14Cu24O41

We used resonant soft x-ray scattering to study the chain ordering in Sr14Cu24O41 (SCO). We observed, for the first time, both the chain and ladder orders in SCO with the same probe. We found that the chain modulation in SCO is incommensurate with wave vector L_(c)=0.318, is strongly temperature (T) dependent, and is accompanied by a substantial hole modulation. By contrast, the chain modulation in a hole-depleted control sample La6Ca8Cu24O41 was commensurate (L_(c)=0.3), T independent, and purely structural. We conclude that the chain charge order in SCO is a 4k_(F) charge density wave stabilized by the misfit strain between the ladder and chain substructures.     

Study on ion formation in electrospray droplet impact secondary ion mass spectrometry

A new type of cluster secondary ion mass spectrometry (SIMS), named electrospray droplet impact (EDI), has been developed in our laboratory. In general, rather strong negative ions as well as positive ions can be generated by EDI compared with conventional SIMS. In this work, various aspects of ion formation in EDI are investigated. The Brønsted bases (proton acceptor) and acids (proton donor) mixed in the analyte samples enhanced the signal intensities of deprotonated molecules (negative ions) and protonated molecules (positive ions), respectively, for analytes. This suggests the occurrence of heterogeneous proton transfer reactions (i.e. M + M′ → [M+H]⁺ + [M′? H]^?) in the shockwave‐heated selvedge of the colliding interface between the water droplet and the solid sample deposited on the metal substrate. EDI‐SIMS shows a remarkable tolerance to the large excess of salts present in samples. The mechanism for desorption/ionization in EDI is much simpler than those for MALDI and SIMS because only very thin sample layers take part in the shockwave‐heated selvedge and complicated higher‐order reactions are largely suppressed. Copyright © 2007 John Wiley & Sons, Ltd.     

Antioxidant hydroxycinnamic acid derivatives isolated from Brazilian bee pollen

One novel and three known hydroxycinnamic acid derivatives having antioxidant activities were isolated from a Brazilian bee pollen. They were identified as kaempferol 3-O-[2-O-p-coumaroyl]-alpha-L-arabinopyranoside, N(1), N(5), N(10)-tri-p-coumaroyl spermidine, N(1), N(5), N(10), N(14)-tetra-p-coumaroyl spermine, and monocaffeoyl-tri-p-coumaroyl spermine, respectively. The structure of the kaempferol glycoside was established on the basis of spectroscopic and chemical investigations. Among the isolated compounds, monocaffeoyl-tri-p-coumaroyl spermine showed the strongest free radical-scavenging activity, which was almost identical to that of alpha-tocopherol. On the other hand, the antioxidant effect of tri-p-coumaroyl spermidine on autooxidation of linoleic acid was strongest and nearly equal to that of alpha-tocopherol.