Unisoku Co.

Hirakata, Japan

Unisoku Co.

Hirakata, Japan
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By use of a pump light source for repeatedly generating a pump light pulse and a probe light source for repeatedly generating a probe light pulse in a shorter repetition time interval than the pump light pulse, the pump light pulse is repeatedly irradiated on a sample, and the probe light pulse is repeatedly irradiated on the sample every time the pump pulse is irradiated. An intensity of a probe light pulse having passed through the sample is detected. A shift in a delay time of the probe light pulse with respect to the pump light pulse is measured every time the pump light pulse is irradiated. Transient absorption measurement data of the sample is obtained based on the detected data of the probe light pulse intensity obtained in higher time density than repetition time density of the probe light pulse based on the measured shift in the delay time.


Kitahama Y.,Kwansei Gakuin University | Uemura S.,Kwansei Gakuin University | Katayama R.,Kwansei Gakuin University | Suzuki T.,UNISOKU Co. | And 2 more authors.
Applied Physics Letters | Year: 2017

Tip-enhanced Raman scattering (TERS) spectroscopy has high sensitivity and high spatial resolution, although it shows low reproducibility due to the variable optical properties of the tips. In the present study, polarized scattering spectra of localized surface plasmon resonance (LSPR) at the apex of the tip induced by conventional dark field illumination were compared with the corresponding TERS spectra, generated by excitation using polarization not only parallel and perpendicular to the tip, but also vertical to the sample plane (z-polarization). The polarization-dependence of LSPR was consistent with that of the TERS. Thus, the optical properties of the tip can be easily optimized before TERS measurement by excitation polarization that induces the largest LSPR signal. © 2017 Author(s).


Yanagisawa S.,University of Hyogo | Deshpande M.S.,Nara Institute of Science and Technology | Hirota S.,Nara Institute of Science and Technology | Nakagawa T.,UNISOKU Co. | Ogura T.,University of Hyogo
Journal of Raman Spectroscopy | Year: 2017

An improved stopped-flow resonance Raman spectroscopy device was constructed using a stopped-flow mixer with a dead time of 3 ms and a mixing volume of 0.1 mL. The device was tested using myoglobin, where the formation reaction of a high-valent heme species, ferryl-oxo heme, was monitored by time-resolved resonance Raman spectroscopy after mixing a ferric myoglobin solution with a hydrogen peroxide solution. The ferryl-oxo heme formation rate constant obtained by Raman spectroscopy is in good agreement with the rate constant obtained by conventional stopped-flow absorption spectroscopy for the same reaction under the same conditions. It is proved by these results that the present device is generally applicable to enzyme-substrate reactions with a significantly higher time resolution than previously reported. © 2017 John Wiley & Sons, Ltd.


Furutani Y.,Japan Institute for Molecular Science | Furutani Y.,Graduate University for Advanced Studies | Kimura T.,Japan Institute for Molecular Science | Kimura T.,Graduate University for Advanced Studies | Okamoto K.,UNISOKU Co.
Biophysics (Japan) | Year: 2013

Attenuated total reflectance (ATR)-FTIR spectroscopy has been widely used to probe protein structural changes under various stimuli, such as light absorption, voltage change, and ligand binding, in aqueous conditions. Timeresolved measurements require a trigger, which can be controlled electronically; therefore, light and voltage changes are suitable. Here we developed a novel, rapid buffer-exchange system for time-resolved ATR-FTIR spectroscopy to monitor the ligand- or ion-binding reaction of a protein. By using the step-scan mode (time resolution; 2.5ms), we confirmed the completion of the buffer-exchange reaction within ~25ms; the process was monitored by the infrared absorption change of a nitrate band at 1,350 cm-1. We also demonstrated the anionbinding reaction of a membrane protein, Natronomonas pharaonis halorhodopsin (pHR), which binds a chloride ion in the initial anion-binding site near the retinal chromophore. The formation of chloride- or nitrate-bound pHR was confirmed by an increase of the retinal absorption band at 1,528 cm-1. It also should be noted that low sample consumption (~1 μg of protein) makes this new method a powerful technique to understand ligand-protein and ion-protein interactions, particularly for membrane proteins. ©2013 THE BIOPHYSICAL SOCIETY OF JAPAN.


PubMed | UNISOKU Co. and Graduate University for Advanced Studies
Type: | Journal: Biophysics (Nagoya-shi, Japan) | Year: 2016

Attenuated total reflectance (ATR)-FTIR spectroscopy has been widely used to probe protein structural changes under various stimuli, such as light absorption, voltage change, and ligand binding, in aqueous conditions. Time-resolved measurements require a trigger, which can be controlled electronically; therefore, light and voltage changes are suitable. Here we developed a novel, rapid buffer-exchange system for time-resolved ATR-FTIR spectroscopy to monitor the ligand- or ion-binding re-action of a protein. By using the step-scan mode (time resolution; 2.5 ms), we confirmed the completion of the buffer-exchange reaction within 25 ms; the process was monitored by the infrared absorption change of a nitrate band at 1,350 cm(-1). We also demonstrated the anion-binding reaction of a membrane protein, Natronomonas pharaonis halorhodopsin (pHR), which binds a chloride ion in the initial anion-binding site near the retinal chromophore. The formation of chloride- or nitrate-bound pHR was confirmed by an increase of the retinal absorption band at 1,528 cm(-1). It also should be noted that low sample consumption (1 g of protein) makes this new method a powerful technique to understand ligand-protein and ion-protein interactions, particularly for membrane proteins.


Nakagawa T.,Unisoku Co. | Okamoto K.,Unisoku Co. | Hanada H.,Unisoku Co. | Katoh R.,Nihon University
Optics Letters | Year: 2016

Despite the long-standing importance of transient absorption (TA) spectroscopy, many researchers remain frustrated by the difficulty of measuring the nanosecond range in a wide spectral range. To address this shortcoming, we propose a TA spectrophotometer in which there is no synchronization between a pump pulse and a train of multiple probe pulses from a picosecond supercontinuum light source, termed the randomly-interleaved-pulse-train (RIPT) method. For each pump pulse, many monochromatized probe pulses impinge upon the sample, and the associated pump-probe time delays are determined passively shot by shot with subnanosecond accuracy. By repeatedly pumping with automatically varying time delays, a TA temporal profile that covers a wide dynamic range from subnanosecond to milliseconds is simultaneously obtained. By scanning wavelength, this single, simple apparatus acquires not only wide time range TA profiles, but also broadband TA spectra from the visible through the near-infrared regions. Furthermore, we present a typical result to demonstrate how the RIPT method may be used to correct for fluorescence, which often pollutes TA curves. © 2016 Optical Society of America.


Irita M.,Tokyo University of Science | Homma Y.,Tokyo University of Science | Miura T.,UNISOKU Co.
e-Journal of Surface Science and Nanotechnology | Year: 2013

A single-walled carbon nanotube (SWNT) with well-defined structure has a potential as a probe of scanning microscopy. However, SWNT tip has not been applied to practical use yet because of the difficulty in the tip preparation. We have developed a technology for fabrication of SWNT tips with the yield rate of 25%. Various lengths and shapes of SWNT tips were examined as the probe of ultrahigh vacuum scanning tunneling microscopy (STM). We found that the length of SWNT was a crucial factor for the application to STM. Atomic-scale resolution could be obtained on the surface of highly oriented pyrolytic graphite with an SWNT tip shorter than 300 nm. In the case of ring type SWNT tip, which used the side wall of SWNT, the STM images depended on the scan direction due to the half-ring shape, and atomic-scale resolution could be obtained when scanned along the circumference direction of the ring. Although the stability of the SWNT tip during scanning needs to be improved, present results prove the potential of SWNT for STM probes. © 2013 The Surface Science Society of Japan.


Suzuki T.,Kwansei Gakuin University | Yan X.,Kwansei Gakuin University | Kitahama Y.,Kwansei Gakuin University | Sato H.,Kwansei Gakuin University | And 3 more authors.
Journal of Physical Chemistry C | Year: 2013

Tip-enhanced Raman scattering (TERS) spectral measurements of nanocomposite styrene-butadiene rubber (SBR) and multiwalled carbon nanotubes (MWCNTs) films were used to explore the local molecular interaction between nanocomposites. TERS spectra from geographically separated points were attributable to SBR or MWCNTs, showing great potential for investigating local film inhomogeneity within several tens of nanometers. Such inhomogeneity has never been observed by confocal Raman measurements. TERS bands due to SBR phenyl groups were strong when MWCNT bands were strong, whereas vinyl-group TERS bands were strong when the MWCNT bands were weak. Analysis of the findings suggests that the local distribution of polymer chains is modified with changes in the orientation of the phenyl rings by π-π interactions between the polymer chains and the MWCNTs. © 2012 American Chemical Society.


Kitahama Y.,Kwansei Gakuin University | Ikemachi T.,Kwansei Gakuin University | Suzuki T.,Kwansei Gakuin University | Miura T.,UNISOKU Co. | Ozaki Y.,Kwansei Gakuin University
Chemical Communications | Year: 2014

On an AgNO3 crystal, an equilateral or a right-angle triangle-shaped Ag trimer was selectively fabricated through near-field photo-reduction and observed in situ by using an apertured cantilever coupled with an atomic force microscope. By using the different triangle-shaped Ag trimers, irradiation wavelength and polarization dependence of surface-enhanced Raman scattering were investigated. This journal is © the Partner Organisations 2014.


PubMed | UNISOKU Co., University of Tokyo and Kwansei Gakuin University
Type: Journal Article | Journal: Physical chemistry chemical physics : PCCP | Year: 2015

Single-layer graphene microislands with smooth edges and no visible grain boundary were epitaxially grown on the C-face of 4H-SiC and then characterized at the nanoscale using tip-enhanced Raman spectroscopy (TERS). Although these graphene islands appear highly homogeneous in micro-Raman imaging, TERS reveals the nanoscale strain variation caused by ridge nanostructures. A G band position shift up to 9 cm(-1) and a band broadening up to 30 cm(-1) are found in TERS spectra obtained from nanoridges, which is explained by the compressive strain relaxation mechanism. The small size and refined nature of the graphene islands help in minimizing the inhomogeneity caused by macroscale factors, and allow a comparative discussion of proposed mechanisms of nanoridge formation.

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