Browsing by Author "Shimada, Rintaro"

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Automatic and objective oral cancer diagnosis by Raman spectroscopic detection of keratin with multivariate curve resolution analysis
(2016-01-25)
Chen, Po-Hsiung
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Shimada, Rintaro
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Yabumoto, Sohshi
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Okajima, Hajime
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Ando, Masahiro
We have developed an automatic and objective method for detecting human oral squamous cell carcinoma (OSCC) tissues with Raman microspectroscopy. We measure 196 independent Raman spectra from 196 different points of one oral tissue sample and globally analyze these spectra using a Multivariate Curve Resolution (MCR) analysis. Discrimination of OSCC tissues is automatically and objectively made by spectral matching comparison of the MCR decomposed Raman spectra and the standard Raman spectrum of keratin, a well-established molecular marker of OSCC. We use a total of 24 tissue samples, 10 OSCC and 10 normal tissues from the same 10 patients, 3 OSCC and 1 normal tissues from different patients. Following the newly developed protocol presented here, we have been able to detect OSCC tissues with 77 to 92% sensitivity (depending on how to define positivity) and 100% specificity. The present approach lends itself to a reliable clinical diagnosis of OSCC substantiated by the "molecular fingerprint" of keratin.
Intensity enhancement and selective detection of proximate solvent molecules by molecular near-field effect in resonance hyper-Raman scattering
(2008-07-14)
Shimada, Rintaro
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Kano, Hideaki
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Hamaguchi, Hiro-o
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應用化學系
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應用化學系分子科學碩博班
A new molecular phenomenon associated with resonance hyper-Raman (HR) scattering in solution has been discovered. Resonance HR spectra of all-trans-beta-carotene and all-trans-lycopene in various solvents exhibited several extra bands that were not assignable to the solute but were unequivocally assigned to the solvents. Neat solvents did not show detectable HR signals under the same experimental conditions. Similar experiments with all-trans-retinal did not exhibit such enhancement either. All-trans-beta-carotene and all-trans-lycopene have thus been shown to induce enhanced HR scattering of solvent molecules through a novel molecular effect that is not associated with all-trans-retinal. We call this new effect the "molecular near-field effect." In order to explain this newly found effect, an extended vibronic theory of resonance HR scattering is developed where the vibronic interaction including the proximate solvent molecule (intermolecular vibronic coupling) is explicitly introduced in the solute hyperpolarizability tensor. The potential of "molecular near-field HR spectroscopy," which selectively detects molecules existing in the close vicinity of a HR probe in complex chemical or biological systems, is discussed. (C) 2008 American Institute of Physics.
Molecular near-field antenna effect in resonance hyper-Raman scattering: Intermolecular vibronic intensity borrowing of solvent from solute through dipole-dipole and dipole-quadrupole interactions
(2014-05-28)
Shimada, Rintaro
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Hamaguchi, Hiro-o
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應用化學系
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應用化學系分子科學碩博班
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Department of Applied Chemistry
We quantitatively interpret the recently discovered intriguing phenomenon related to resonance Hyper-Raman (HR) scattering. In resonance HR spectra of all-trans-beta-carotene (beta-carotene) in solution, vibrations of proximate solvent molecules are observed concomitantly with the solute beta-carotene HR bands. It has been shown that these solvent bands are subject to marked intensity enhancements by more than 5 orders of magnitude under the presence of beta-carotene. We have called this phenomenon the molecular-near field effect. Resonance HR spectra of beta-carotene in benzene, deuterated benzene, cyclohexane, and deuterated cyclohexane have been measured precisely for a quantitative analysis of this effect. The assignments of the observed peaks are made by referring to the infrared, Raman, and HR spectra of neat solvents. It has been revealed that infrared active and some Raman active vibrations are active in the HR molecular near-field effect. The observed spectra in the form of difference spectra (between benzene/deuterated benzene and cyclohexane/deuterated cyclohexane) are quantitatively analyzed on the basis of the extended vibronic theory of resonance HR scattering. The theory incorporates the coupling of excited electronic states of beta-carotene with the vibrations of a proximate solvent molecule through solute-solvent dipole-dipole and dipole-quadrupole interactions. It is shown that the infrared active modes arise from the dipole-dipole interaction, whereas Raman active modes from the dipole-quadrupole interaction. It is also shown that vibrations that give strongly polarized Raman bands are weak in the HR molecular near-field effect. The observed solvent HR spectra are simulated with the help of quantum chemical calculations for various orientations and distances of a solvent molecule with respect to the solute. The observed spectra are best simulated with random orientations of the solvent molecule at an intermolecular distance of 10 angstrom. (C) 2014 AIP Publishing LLC.
Solute-solvent intermolecular vibronic coupling as manifested by the molecular near-field effect in resonance hyper-Raman scattering
(2011-01-21)
Shimada, Rintaro
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Hamaguchi, Hiro-o
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應用化學系
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應用化學系分子科學碩博班
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Department of Applied Chemistry
Vibronic coupling within the excited electronic manifold of the solute all-trans-beta-carotene through the vibrational motions of the solvent cyclohexane is shown to manifest as the "molecular near-field effect," in which the solvent hyper-Raman bands are subject to marked intensity enhancements under the presence of all-trans-beta-carotene. The resonance hyper-Raman excitation profiles of the enhanced solvent bands exhibit similar peaks to those of the solute bands in the wavenumber region of 21 700-25 000 cm(-1) (10 850-12 500 cm(-1) in the hyper-Raman exciting wavenumber), where the solute all-trans-beta-carotene shows a strong absorption assigned to the 1A(g) -> 1B(u) transition. This fact indicates that the solvent hyper-Raman bands gain their intensities through resonances with the electronic states of the solute. The observed excitation profiles are quantitatively analyzed and are successfully accounted for by an extended vibronic theory of resonance hyper-Raman scattering that incorporates the vibronic coupling within the excited electronic manifold of all-trans-beta-carotene through the vibrational motions of cyclohexane. It is shown that the major resonance arises from the B-term (vibronic) coupling between the first excited vibrational level (v = 1) of the 1B(u) state and the ground vibrational level (v = 0) of a nearby A(g) state through ungerade vibrational modes of both the solute and the solvent molecules. The inversion symmetry of the solute all-trans-beta-carotene is preserved, suggesting the weak perturbative nature of the solute-solvent interaction in the molecular near-field effect. The present study introduces a new concept, " intermolecular vibronic coupling," which may provide an experimentally accessible/theoretically tractable model for understanding weak solute-solvent interactions in liquid. (C) 2011 American Institute of Physics. [doi:10.1063/1.3512923]
Superresolution vibrational imaging by simultaneous detection of Raman and hyper-Raman scattering
(2011-07-01)
Matsuzaki, Korenobu
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Shimada, Rintaro
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Hamaguchi, Hiro-o
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應用化學系
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應用化學系分子科學碩博班
We have developed a superresolution vibrational imaging method by simultaneous detection of Raman and hyper-Raman scattering. Raman and hyper-Raman images obtained with the same laser spot carry independent information on the sample spatial distribution, owing to different signal dependence (linear in Raman and quadratic in hyper-Raman) on the incident light intensity. This information can be quantitatively analyzed to recover the incident light intensity distribution at the focal plane. A superresolution vibrational image is then derived by the constrained deconvolution of the images by the obtained incident light intensity distribution. This method has been applied to a TiO(2) nanostructure and the obtained superresolution image was compared with a scanning electron microscopy image. The spatial resolution achieved by the present method is evaluated to be 160 nm, which is more than twice better than the diffraction limited resolution. (C) 2011 Optical Society of America
Two-step photoionization of trans-stilbene in acetonitrile via an ion-pair precursor studied with picosecond time-resolved absorption and Raman spectroscopies
(2012-02-27)
Miki, Hiroko
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Yoshida, Kyousuke
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Kawate, Chieko
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Shimada, Rintaro
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Takaya, Tomohisa
Picosecond time-resolved visible absorption and Raman spectra of trans-stilbene in acetonitrile have been measured. A new transient absorption band is observed at 440 nm, whose decay time constant coincides with that of the rise of the radical cation. In addition to the known Raman bands of the radical cation, a new Raman feature showing a fast decay is found at 1599 cm(-1). We assign the 440 nm absorption band and the 1599 cm(-1) Raman band to a precursor of the radical cation. The precursor may well be an ion pair that holds an ejected electron still around the cation. (C) 2012 Elsevier B. V. All rights reserved.