Tatsuaki Ataka

NEAR-FIELD OPTICAL MICROSCOPY IN LIQUIDS

The scanning near‐field optical microscopy imaging of specimens in liquid and of cultured cells in aqueous solutions is reported. A scanning near‐field optical/atomic‐force microscope (SNOM‐AFM) was developed, in which the scanning of an optical‐fiber probe cantilever over the specimen was controlled by noncontact mode AFM (dynamic mode AFM). This imaging mode reduces damage to the probe and soft specimens. The resonant frequency of the probe cantilever decreased 20% to ≊14 kHz and the Q factor decreased by a factor of 8 to ≊30 in water, compared with these values in air, which was sufficient to perform SNOM‐AFM imaging in liquid.

Piezoelectric Crystal Biosensor System for Detection of Escherichia Coli

Abstract A piezoelectric crystal biosensor system was applied to the detection of Escherichia coli. the system consists of an oscillator, a frequency counter, a flow cell and a modified piezoelectric crystal. Anti-E. coli antibody is immobilized on the surface of the crystal. It is used as an E. coli detection by measuring its resonant frequency shift due to a mass change caused by specific binding of the micro organisms to the surface. the frequency shift correlates with an E. coli concentration in the range of 106−108 cells·cm−3. the resonant frequency shift is increased by further treatment to bind micro-particles modified with anti-E. coli antibody. This method allows us to improve the determination limit to 105 cells · cm−3.

In-situ monitoring of microrheology on electrochemical deposition using an advanced quartz crystal analyzer and its application to polypyrrole deposition

Abstract This paper introduces a technique for studying the microrheology of a thin film on a quartz crystal by considering the contrast of the resonant frequency change and resonant resistance change of the quartz crystal. An advanced measuring system was developed for the in-situ measurement of the resonant resistance on the electrochemical reaction. The system was used to monitor polypyrrole deposition by cyclic voltammetry and the constant current method. In the electrochemical deposition, not only the resonant frequency change but also the resonant resistance increase was observed, i.e. the deposited film was a viscoelastic film. The resonant resistance was changed in the range of 100–600 Ω for the resonant frequency change of 10 000 Hz; it showed a small change in the early stage of film deposition which increased after a resonant frequency change of 5000 Hz. The swelling of the film was observed corresponding to the unusual resonant resistance increase for the constant current deposition of 6 mA cm −2 .

A quartz crystal viscosity sensor for monitoring coagulation reaction and its application to a multichannel coagulation detector

A quartz crystal viscosity sensor was applied to a coagulation reaction monitoring system. The system consists of 16 oscillating circuits, a channel selector, a frequency counter, a temperature controller and a microcomputer. The system is named the Quartz Chemical Analyzer (QCA). AT-cut quartz crystals (9 MHz) were used as viscosity detectors and were attached to a cell in order to expose only one side of the quartz plate. The system was applied to the detection of the blood coagulation factors VIII (F VIII) and IX (F IX). The activity of these factors was assayed by a single-stage method. A linear relationship was obtained in a double-logarithmic diagram of concentration versus coagulation time with respect to F VIII and F IX in the range 0.05-0.4 unit cm-3 and 0.025-0.2 unit cm-3, respectively.

Piezoelectric resonator as a chemical and biochemical sensing device

Abstract This paper introduces the application of the piezoelectric resonator to a chemical and biochemical sensing. The device was used for viscosity and surface mass change measurement. Viscosity measurement was applied for gelation detection; where endotoxin and fibrinogen were determined, and also thermal analysis, where phase transition of liquid crystal was detected. Surface mass change was applied to electrochemical measurement, where Prussian blue film formation and reaction of the film were monitored, and odorant detection, in which n-amyl acetate, citral, β-ionone and menthone were detected.

Observation of Topography and Optical Image of Optical Fiber End by Atomic Force Mode Scanning Near-Field Optical Microscope

A scanning near-field optic/atomic force microscope (SNOAM) was improved using a novel optical fiber probe. The optical fiber probe has a mirror grounded on the ridge for the optical lever of AFM. The resonant characteristics of the optical fiber probe were adequate for a noncontact AFM cantilever: the typical Q factor and resonant frequency were 574 and 10.9 kHz, respectively. The topographical and optical resolution of the SNOAM was better than 100 nm for a standard sample of chromium patterns on a quartz substrate. The SNOAM successfully provided topographies and optical images of optical fiber ends simultaneously. These images indicated that the optical pattern of the core was markedly influenced by the surface roughness of the optical fiber end.

Development of near-field optic/atomic force microscope for biological materials in aqueous solutions.

This paper reports improvements of optical fiber cantilevers and the scanning near-field optical microscopy imaging of biological materials in liquid. In our scanning near-field optical/atomic-force microscope (SNOAM), the scanning of an optical fiber cantilever over the specimen was controlled by dynamic mode AFM to reduce damage to the probe and soft specimens. The typical resonant frequency of the optical fiber cantilever was 19.5 kHz, while it was 23.0 kHz in air. The Q-factor of the cantilever depended on the vibration amplitude and was typically 260-600 in air and 40-240 in water. The relationship between the vibration amplitude and the average sample-probe separation indicated that the cantilever worked in the non-contact mode in water, while it worked in the cyclic-contact mode in air. Cultured cells in aqueous solutions were visualized by the SNOAM, indicating that the SNOAM is suitable to observe soft specimens.

Approaches for submicrosequencing

From a conventional SDS-acrylamide gel plate, protein (≈1 μg), even after staining by dye, was extracted with 70% formic acid and purified by Biogel P-10 column chromatography in 70% formic acid. The recovery was 60–99% and the protein purified by this method was free from SDS, dyes, glycine, and buffer salts and ready to use for protein composition and sequence studies. The method can avoid the protease digestion of the protein that has often been observed in the electroelution method. For amino acid analysis, protein was hydrolyzed with a gas of a HCL/trifluoroacetic acid/H2O mixture at 158°C for 22.5 and 45 min to avoid contamination (less than 1 pmole). The method provided sufficient hydrolysis even for hydrophobic protein. It is under process of automation. Carboxyl-terminal analysis was performed with carboxypeptidases A, B, and P in the presence of alcohols and detergents. The effects on the carboxypeptidases (and several proteases) are summarized. These additions increased the solubility of proteins and enhanced the digestion. For N-terminal sequencing, conventional Edman degradation was followed up to the ATZ-derivative and this ATZ-derivative was reacted with primary amines such as 125I-histamine or 1-aminopyrene to produce a phenylthiocarbamyl-amino acid-amine derivative with a yield as high as 95%. The conventional procedure of Edman degradation was preserved, but instead of the acid conversion to PTH derivatives, the above coupling procedure was introduced in order to increase the sensitivity to the 1–100f mole range.

Scanning near-field optical images of ordered polystyrene particle layers in transmission and luminescence excitation modes

Scanning near-field optical images of hexagonally close-packed layers of polystyrene spherical particles with a diameter of 1.0 microm have been investigated. The layers were composed of particles that were doped either totally or partially with an organic fluorescent dye. Observations were made in the transmission and luminescence excitation modes with a scanning near-field optical microscope (SNOM) with a spatial resolution shorter than the wavelength of light. The patterns observed in the SNOM images are significantly dependent on the microstructures of layers, that is, the layers are either single or double layered, and the particles are either totally or partially doped. These results are discussed in terms of specific modes of electromagnetic waves transmitting across and along the layers after the local excitation at the tip end of the scanning microprobe.

Micro-rheology changes of Nafion® films with electrochemical mass-transport in hydroquinone solutions and in situ measurement using a quartz crystal analyzer

Abstract This paper shows that the electrochemical mass transport in film-coated electrodes involves the rheology change of the films and that these changes can be detected by measuring the resonant frequency and resonant resistance of a coated quartz crystal. We used a Nafion®-coated quartz crystal and measured the cyclic voltammograms in hydroquinone solution. The changes of the resonant frequency and resonant resistance showed that mass transport and viscoelastic changes had occurred in the Nafion films. The diagrammed resonant frequency and resonant resistance changes suggested that the Na ion de-doping from the films decreased the film mass and increased the film rigidity in the first oxidation process, the benzoquinone accumulation and anion doping increased the film mass in the following oxidation process, while the Na ion re-doped in the first reduction process, and benzoquinone was reduced from the films in the final reduction process. Study of the charge expended from the reaction suggested the participation of anion or water transport.