Publications by authors named "Mamoru Tamura"

54 Publications

Damage-free light-induced assembly of intestinal bacteria with a bubble-mimetic substrate.

Commun Biol 2021 03 22;4(1):385. Epub 2021 Mar 22.

Department of Physical Science, Graduate School of Science, Osaka Prefecture University, Osaka, Japan.

Rapid evaluation of functions in densely assembled bacteria is a crucial issue in the efficient study of symbiotic mechanisms. If the interaction between many living microbes can be controlled and accelerated via remote assembly, a cultivation process requiring a few days can be ommitted, thus leading to a reduction in the time needed to analyze the bacterial functions. Here, we show the rapid, damage-free, and extremely dense light-induced assembly of microbes over a submillimeter area with the "bubble-mimetic substrate (BMS)". In particular, we successfully assembled 10-10 cells of lactic acid bacteria (Lactobacillus casei), achieving a survival rate higher than 95% within a few minutes without cultivation process. This type of light-induced assembly on substrates like BMS, with the maintenance of the inherent functions of various biological samples, can pave the way for the development of innovative methods for rapid and highly efficient analysis of functions in a variety of microbes.
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http://dx.doi.org/10.1038/s42003-021-01807-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7985151PMC
March 2021

Near-field transmission and reflection spectroscopy for revealing absorption and scattering characteristics of single silver nanoplates.

J Chem Phys 2020 Oct;153(14):144703

Department of Chemistry and Biochemistry, School of Advanced Science and Engineering, Waseda University, Shinjuku, Tokyo 169-8555, Japan.

Near-field optical microscopy visualizes spatial characteristics of elementary excitations induced in metal nanostructures. However, the microscopy is not able to reveal the absorption and scattering characteristics of the object simultaneously. In this study, we demonstrate a method for revealing the absorption and scattering characteristics of silver nanoplate by using near-field transmission and reflection spectroscopy. Near-field transmission and reflection images show characteristic spatial features attributable to the excited plasmon modes. The near-field refection image near the resonance shows a reversed contrast depending on the observed wavelength. Near-field reflection spectra show unique positive and negative resonant features. We reveal that the optical characteristics and the wavelength dependency of the optical contrast originate from the scattering and absorption properties of the plasmons, with the aid of the electromagnetic simulations.
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http://dx.doi.org/10.1063/5.0025328DOI Listing
October 2020

Light-induced assembly of living bacteria with honeycomb substrate.

Sci Adv 2020 02 28;6(9):eaaz5757. Epub 2020 Feb 28.

Research Institute for Light-induced Acceleration System, Osaka Prefecture University, Sakai 599-8570, Japan.

Some bacteria are recognized to produce useful substances and electric currents, offering a promising solution to environmental and energy problems. However, applications of high-performance microbial devices require a method to accumulate living bacteria into a higher-density condition in larger substrates. Here, we propose a method for the high-density assembly of bacteria (10 to 10 cells/cm) with a high survival rate of 80 to 90% using laser-induced convection onto a self-organized honeycomb-like photothermal film. Furthermore, the electricity-producing bacteria can be optically assembled, and the electrical current can be increased by one to two orders of magnitude simply by increasing the number of laser irradiations. This concept can facilitate the development of high-density microbial energy conversion devices and provide new platforms for unconventional environmental technology.
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http://dx.doi.org/10.1126/sciadv.aaz5757DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7048417PMC
February 2020

Interparticle-Interaction-Mediated Anomalous Acceleration of Nanoparticles under Light-Field with Coupled Orbital and Spin Angular Momentum.

Nano Lett 2019 Aug 4;19(8):4873-4878. Epub 2019 Jul 4.

Graduate School of Science , Osaka Prefecture University , 1-2, Gakuen-cho , Naka-ku, Sakai , Osaka 599-8570 , Japan.

Spin-orbit interaction is a crucial issue in the field of nanoscale physics and chemistry. Here, we theoretically demonstrate that the spin angular momentum (SAM) can accelerate and decelerate the orbital motion of nanoparticles (NPs) via light-induced interparticle interactions by a circularly polarized optical vortex. The Laguerre-Gaussian beam as a conventional optical vortex with orbital angular momentum (OAM) induces the orbital and spinning motion of a trapped object depending on the spatial configuration. On the contrary, it is not clear whether circularly polarized light induces the orbital motion for the particles trapped off-axis. The present study reveals that the interparticle light-induced force due to the SAM enhances or weakens the orbital torque and modulates rotational dynamics depending on the number of NPs, where the rotation speed of NPs in the optical field with both positive SAM and OAM can be 4 times faster than that in the optical field with negative SAM and positive OAM. The obtained results will not only clarify the principle for the control of NPs based on OAM-SAM coupling via light-matter interaction but also contribute to the unconventional laser processing technique for nanostructures with various chiral symmetries.
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http://dx.doi.org/10.1021/acs.nanolett.9b00332DOI Listing
August 2019

Mesoscopic Motion of Optically Trapped Particle Synchronized with Photochromic Reactions of Diarylethene Derivatives.

J Phys Chem Lett 2018 May 7;9(10):2659-2664. Epub 2018 May 7.

Division of Frontier Materials Science and Center for Promotion of Advanced Interdisciplinary Research, Graduate School of Engineering Science , Osaka University , Toyonaka, Osaka 560-8531 , Japan.

Not only the energy but also the momentum of photons transfers to material via photoabsorption; this momentum transfer, known as radiation pressure, can induce motions of small particles. It can therefore be expected to induce mechanical motions of mesoscopic materials synchronized with the reversible change of their absorption coefficient by external stimuli. We demonstrated quantitative photomechanical motions in mesoscopic regions by combining optical tweezer and photochromic reactions of diarylethene (DAE). A microparticle including DAE was optically trapped with 532 nm laser and the absorption band of the DAE was photoswitched with UV laser, resulting in the modulation of the radiation force through the change in the complex dielectric constant of the particle. In this process, mesoscopic mechanical motions were successfully induced by the photochromic reaction. The present approach is potentially applicable in a wide variety of nano/micromechanical devices and also paves the way for monitoring the absorption of photons by molecules via photomechanical response.
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http://dx.doi.org/10.1021/acs.jpclett.8b00890DOI Listing
May 2018

Mechanism in External Field-mediated Trapping of Bacteria Sensitive to Nanoscale Surface Chemical Structure.

Sci Rep 2017 11 30;7(1):16651. Epub 2017 Nov 30.

Department of Physical Science, Graduate School of Science, Osaka Prefecture University, Sakai, Osaka, 599-8570, Japan.

Molecular imprinting technique enables the selective binding of nanoscale target molecules to a polymer film, within which their chemical structure is transcribed. Here, we report the successful production of mixed bacterial imprinted film (BIF) from several food poisoning bacteria by the simultaneous imprinting of their nanoscale surface chemical structures (SCS), and provide highly selective trapping of original micron-scale bacteria used in the production process of mixed BIF even for multiple kinds of bacteria in real samples. Particularly, we reveal the rapid specific identification of E. coli group serotypes (O157:H7 and O26:H11) using an alternating electric field and a quartz crystal microbalance. Furthermore, we have performed the detailed physicochemical analysis of the specific binding of SCS and molecular recognition sites (MRS) based on the dynamic Monte Carlo method under taking into account the electromagnetic interaction. The dielectrophoretic selective trapping greatly depends on change in SCS of bacteria damaged by thermal treatment, ultraviolet irradiation, or antibiotic drugs, which can be well explained by the simulation results. Our results open the avenue for an innovative means of specific and rapid detection of unknown bacteria for food safety and medicine from a nanoscale viewpoint.
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http://dx.doi.org/10.1038/s41598-017-15086-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5709418PMC
November 2017

Optical Trap-Mediated High-Sensitivity Nanohole Array Biosensors with Random Nanospikes.

J Phys Chem Lett 2017 Jan 6;8(2):370-374. Epub 2017 Jan 6.

Department of Physical Science, Graduate School of Science and ‡Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University , 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan.

We clarify an unconventional principle of the light-driven operation of a biosensor for enhanced sensitivity with the help of random nanospikes added to the surface of a nanohole array. Such a system is capable of optically guiding viruses and trapping them in the vicinity of a highly sensitive site by an anomalous light-induced force arising from random-nanospike-modulated extraordinary optical transmission and the plasmonic mirror image in a virus as a dielectric submicron object. In particular, after guiding the viruses near the apex of nanospikes, there are conditions where the spectral peak shift of extraordinary optical transmission can be greatly increased and reach several hundred nanometers in comparison with that of a conventional nanohole array without random nanospikes. These results will allow for the development of a simple, rapid, and highly sensitive virus detection method based on optical trapping with the help of random-nanospike-modulated extraordinary optical transmission, facilitating convenient medical diagnosis and food inspection.
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http://dx.doi.org/10.1021/acs.jpclett.6b02262DOI Listing
January 2017

Submillimetre Network Formation by Light-induced Hybridization of Zeptomole-level DNA.

Sci Rep 2016 12 5;6:37768. Epub 2016 Dec 5.

Nanoscience and Nanotechnology Research Center, Osaka Prefecture University, 1-2, Gakuencho, Nakaku, Sakai, Osaka 599-8570, Japan.

Macroscopic unique self-assembled structures are produced via double-stranded DNA formation (hybridization) as a specific binding essential in biological systems. However, a large amount of complementary DNA molecules are usually required to form an optically observable structure via natural hybridization, and the detection of small amounts of DNA less than femtomole requires complex and time-consuming procedures. Here, we demonstrate the laser-induced acceleration of hybridization between zeptomole-level DNA and DNA-modified nanoparticles (NPs), resulting in the assembly of a submillimetre network-like structure at the desired position with a dramatic spectral modulation within several minutes. The gradual enhancement of light-induced force and convection facilitated the two-dimensional network growth near the air-liquid interface with optical and fluidic symmetry breakdown. The simultaneous microscope observation and local spectroscopy revealed that the assembling process and spectral change are sensitive to the DNA sequence. Our findings establish innovative guiding principles for facile bottom-up production via various biomolecular recognition events.
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http://dx.doi.org/10.1038/srep37768DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5137144PMC
December 2016

Multiple Resonances Induced by Plasmonic Coupling between Gold Nanoparticle Trimers and Hexagonal Assembly of Gold-Coated Polystyrene Microspheres.

J Phys Chem Lett 2016 Sep 6;7(18):3652-8. Epub 2016 Sep 6.

Department of Chemistry and Biochemistry, School of Advanced Science and Engineering, Waseda University , Shinjuku, Tokyo 169-8555, Japan.

Optical properties of a gold nanoparticle trimer assembly coupled with gold-coated hexagonally close-packed polystyrene microspheres were investigated by linear and nonlinear spectroscopy. The observed reflection spectrum shows multiple peaks from the visible to near-infrared spectral regions. The spectroscopic properties were also examined by a finite-difference time-domain simulation. We found that the optical response of plasmons excited in the gold nanoparticle trimers was significantly modulated by strong coupling of the plasmons and the photonic mode induced in the gold-coated polystyrene assembly. Two-photon induced photoluminescence and Raman scattering from the sample were investigated, and both signals were significantly enhanced at the gold nanoparticle assembly. The simulations reveal that the electric fields can be enhanced site-selectively, not only at the interstitial sites in the nanoparticle assembly but also at the gaps between the particle and the gold film due to plasmonic interactions, by tuning the wavelength and are responsible for the strong optical responses.
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http://dx.doi.org/10.1021/acs.jpclett.6b01493DOI Listing
September 2016

Selective optical assembly of highly uniform nanoparticles by doughnut-shaped beams.

Sci Rep 2013 Oct 25;3:3047. Epub 2013 Oct 25.

1] Division of Frontier Materials Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan [2] Center for Quantum Materials Science under Extreme Conditions, Osaka University, Toyonaka, Osaka 560-8531, Japan [3] PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan.

A highly efficient natural light-harvesting antenna has a ring-like structure consisting of dye molecules whose absorption band changes through selective evolutionary processes driven by external stimuli, i.e., sunlight depending on its territory and thermal fluctuations. Inspired by this fact, here, we experimentally and theoretically demonstrate the selective assembling of ring-like arrangements of many silver nanorods with particular shapes and orientations onto a substrate by the light-induced force of doughnut beams with different colours (wavelengths) and polarizations in conjunction with thermal fluctuations at room temperature. Furthermore, the majority of nanorods are electromagnetically coupled to form a prominent red-shifted collective mode of localized surface plasmons resonant with the wavelength of the irradiated light, where a spectral broadening also appears for the efficient broadband optical response. The discovered principle is a promising route for "bio-inspired selective optical assembly" of various nanomaterials that can be used in the wide field of nanotechnology.
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http://dx.doi.org/10.1038/srep03047DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6505715PMC
October 2013

Fluctuation-mediated optical screening of nanoparticles.

Nano Lett 2012 Oct 13;12(10):5337-41. Epub 2012 Sep 13.

Nanoscience and Nanotechnology Research Center, Osaka Prefecture University, 1-2, Gakuencho, Nakaku, Sakai, Osaka 599-8570, Japan.

Inspired by biological motors, we propose a guiding principle for selectively separating nanoparticles (NPs) by efficiently using the light-induced force (LIF) and thermal fluctuations. We demonstrate the possibility of transporting metallic NPs of different sizes with a size-selection accuracy of less than 10 nm even at room temperature by designing asymmetric spatiotemporal light fields. This technique will lead to unconventional nanoextraction processes based on light and fluctuations.
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http://dx.doi.org/10.1021/nl302716cDOI Listing
October 2012

"Triple Observation Method (TOM)" to discriminate optically autofluorescence from porphyrins versus that from copper-metallothioneins.

J Fluoresc 2011 Mar 25;21(2):835-9. Epub 2010 Nov 25.

Department of Health and Environmental Science, Hokkaido Institute of Public Health, North 19 West 12, Sapporo 060-0819 Hokkaido, Japan.

We propose a conclusive difference observed between the excitation conditions required to observe porphyrins and copper-metallothioneins in cells and/or tissues using an ordinary fluorescence microscope. We have emphasized the importance of examining the spectral properties of the emissions to avoid any serious mistakes such as confusing porphyrins with copper-metallothioneins in the liver and kidneys. However, microspectrophotometry is not a conventional method for either histochemical, cytochemical, or pathological studies because microspectrophotometers are both expensive and difficult to operate. Therefore, we demonstrate a simple comparative method using ordinary excitation filter arrangements. When using our technique, it becomes possible to optically discriminate more accurately between the autofluorescence properties arising from porphyrins and those arising from copper-metallothioneins. We would like to name our simple technique "Triple Observation Method (TOM)".
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http://dx.doi.org/10.1007/s10895-010-0773-3DOI Listing
March 2011

Brain oxymetry in the operating room: current status and future directions with particular regard to cytochrome oxidase.

J Biomed Opt 2008 May-Jun;13(3):033001

Kagoshima University Hospital, Division of Intensive Care Medicine, 8-35-1 Sakuragaoka, Kagoshima 890-8520, Japan.

Near-infrared spectroscopy (NIRS) is a cerebral monitoring method that noninvasively and continuously measures cerebral hemoglobin oxygenation and the redox state of cytochrome oxidase using highly tissue-permeable near-infrared light. This technique now has wide clinical application, and its usefulness in the measurement of cerebral hemoglobin oxygenation has been confirmed under global cerebral injury and/or hypoxemic hypoxia; however, regional cerebral infarction located far from the monitoring site may not be detected by NIRS. Furthermore, the specificity and accuracy of the measurement of the redox state of cytochrome oxidase remain controversial. We apply NIRS to both animal and clinical investigations. Based on these results, we discuss the significance of the measurement of cerebral hemoglobin oxygenation and cytochrome oxidase in vivo and in clinical medicine. Using our algorithm, cytochrome oxidase signals are unaffected by hemoglobin signals, even when hematocrit values change from 35 to 5% under cardiopulmonary bypass in a dog model. In the clinical study, cytochrome oxidase during surgery is likely to be a good (though not perfect) predictor of postoperative cerebral outcome. NIRS appears to be a promising technology, but additional investigations are required to establish its clinical efficacy and justify its routine use during operative and perioperative periods.
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http://dx.doi.org/10.1117/1.2940583DOI Listing
September 2008

Clinical evaluation of time-resolved spectroscopy by measuring cerebral hemodynamics during cardiopulmonary bypass surgery.

J Biomed Opt 2007 Nov-Dec;12(6):062112

Hamamatsu Photonics K.K., Central Research Laboratory, 5000 Hirakuchi, Hamamatsu, Shizuoka, 434-8601, Japan.

We developed a three-wavelength time-resolved spectroscopy (TRS) system, which allows quantitative measurement of hemodynamics within relatively large living tissue. We clinically evaluated this TRS system by monitoring cerebral circulation during cardiopulmonary bypass surgery. Oxyhemoglobin, deoxyhemoglobin, total hemoglobin and oxygen saturation (SO(2)) were determined by TRS on the left forehead attached with an optode spacing of 4 cm. We also simultaneously monitored jugular venous oxygen saturation (SjvO(2)) and arterial blood hematocrit (Hct) using conventional methods. The validity and usefulness of the TRS system were assessed by comparing parameters obtained with the TRS and conventional methods. Although the changes in SO(2) were lower than those in SjvO(2), SO(2) obtained by TRS paralleled the fluctuations in SjvO(2), and a good correlation between these values was observed. The only exceptions occurred during the perfusion period. Moreover, there was a good correlation between tHb and Hct values (r(2)=0.63). We concluded that time-resolved spectroscopy reflected the conditions of cerebral hemodynamics of patients during surgical operations.
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http://dx.doi.org/10.1117/1.2804931DOI Listing
March 2008

Adsorption and micellization behavior of novel gluconamide-type gemini surfactants.

J Colloid Interface Sci 2008 Feb 6;318(2):440-8. Epub 2007 Nov 6.

Department of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan.

The adsorption and micellization behavior of novel sugar-based gemini surfactants (N,N(')-dialkyl-N,N(')-digluconamide ethylenediamine, Glu(n)-2-Glu(n), where n is the hydrocarbon chain length of 8, 10 and 12) has been studied on the basis of static/dynamic surface tension, fluorescence, dynamic light scattering (DLS) and cryogenic transmission electron microscope (cryo-TEM) data. The static surface tension of the aqueous Glu(n)-2-Glu(n) solutions measured at the critical micelle concentration (cmc) is observed to be significantly lower than that of the corresponding monomeric surfactants. This suggests that the gemini surfactants, newly synthesized in the current study, are able to form a closely packed monolayer film at the air/aqueous solution interface. The greater ability in the molecular association is supported by the remarkably (approximately 100-200 times) lower cmc of the gemini surfactants compared with the corresponding monomeric ones. With a combination of the fluorescence and DLS data, a structural transformation of the Glu(n)-2-Glu(n) micelles is suggested to occur with an increase in the concentration. The cryo-TEM measurements clearly confirm the formation of worm-like micelles of Glu(12)-2-Glu(12) at the concentration well above the cmc.
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http://dx.doi.org/10.1016/j.jcis.2007.10.039DOI Listing
February 2008

Detection of prion protein immune complex for bovine spongiform encephalopathy diagnosis using fluorescence correlation spectroscopy and fluorescence cross-correlation spectroscopy.

Anal Biochem 2007 Nov 2;370(2):131-41. Epub 2007 Aug 2.

Laboratory of Supramolecular Biophysics, Research Institute of Electronic Science, Hokkaido University, Sapporo 060-0818, Japan.

Fluorescence correlation spectroscopy (FCS) and fluorescence cross-correlation spectroscopy (FCCS) are powerful techniques to measure molecular interactions with high sensitivity in homogeneous solution and living cells. In this study, we developed methods for the detection of prion protein (PrP) using FCS and FCCS. A combination of a fluorescent-labeled Fab' fragment and another anti-PrP monoclonal antibody (mAb) enabled us to detect recombinant bovine PrP (rBoPrP) using FCS because there was a significant difference in the diffusion coefficients between the labeled Fab' fragment and the trimeric immune complex consisting of rBoPrP, labeled Fab' fragment, and another anti-PrP mAb. On the other hand, FCCS detected rBoPrP using two mAbs labeled with different fluorescence dyes. The detection limit for PrP in FCCS was approximately threefold higher than that in FCS. The sensitivity of FCCS in detection of abnormal isoform of PrP (PrP(Sc)) was comparable to that of enzyme-linked immunosorbent assay (ELISA). Because FCS and FCCS detect the PrP immune complex in homogeneous solution of only microliter samples with a single mixing step and without any washing steps, these features of measurement may facilitate automating bovine spongiform encephalopathy diagnosis.
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http://dx.doi.org/10.1016/j.ab.2007.07.018DOI Listing
November 2007

Expansion of intensity correlation spectroscopy for lifetime measurements--application to intracellular oxygen dynamics measurements.

J Biomed Opt 2007 Mar-Apr;12(2):020503

Hokkaido University, Biophysics Laboratory, Research Institute for Electronic Science, Sapporo 060-0812, JapanHokkaido University, Topological Science and Technology, The 21st COE program, Sapporo 060-8628, Japan.

We report on a simple correlation method for lifetime measurements using a random modulated excitation light source. We use an intensity correlation function of emission for lifetime analyses. In this method, no reference timing of the excitation is required. We apply the correlation method to measure phosphorescence decays and successfully demonstrate in the analysis of the phosphorescence decay from Pd(II) porphine in HeLa cells under aerobic and anaerobic conditions to understand the oxygen dynamics in individual cells. The method is applicable to faster decay time measurements down to a nanosecond range when the detection system is improved. Current fluorescence correlation setups can easily be modified for lifetime measurements, expanding the applicability in biological problems.
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http://dx.doi.org/10.1117/1.2717623DOI Listing
July 2007

Phosphorescence decay time measurements using intensity correlation spectroscopy.

Exp Mol Pathol 2007 Apr 8;82(2):175-83. Epub 2007 Mar 8.

Biophysics Laboratory, Research Institute for Electronic Science, Hokkaido University, N12W6, Sapporo 060-0812, Japan.

In this paper, we report on phosphorescence measurements for oxygen dynamics in cells by means of a correlation method, which is an expansion of the fluorescence correlation spectroscopy. The intensity correlation function of the emission excited by a pulsed light source was measured. With changing the pulse timing, both the fluorescence correlation function and the decay time of phosphorescence could be analyzed. This method was applied for the analysis of the oxygen dynamics in HeLa cells stained by Pd(II)-porphine. The decay function consisted of two exponential components, which might be attributed to free and protein-bound forms of Pd(II)-porphine in the cell, respectively. The relative change of the oxygen concentration under normal and uncoupled respiration conditions was also measured. The simplicity of this method is a great advantage in the biological applications. Although the current system we used was limited in the temporal resolution, the method is in principle applicable to faster decay time measurements down to the nano-second range of the fluorescence decay times.
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http://dx.doi.org/10.1016/j.yexmp.2007.01.004DOI Listing
April 2007

Diffusion analysis of glucocorticoid receptor and antagonist effect in living cell nucleus.

Exp Mol Pathol 2007 Apr 22;82(2):163-8. Epub 2006 Dec 22.

Laboratory of Supramolecular Biophysics, Research Institute for Electronic Science, Hokkaido University, N12W6, Sapporo 060-0812, Japan.

The diffusion properties of hGRalpha in living cells have been analyzed. The hGRalpha translocalized from the cytosol to the nucleus after addition of Dex just as RU486; however, the Brownian motions of the proteins in nucleus were different. In order to analysis microenvironment of the nucleus of living cell, four different tandem EGFPs were constructed. Diffusion of tandem EGFP was dependent on the length of the protein as a rod-like molecule in solution. We found two kinds of mobility, fast diffusional mobility as a major component and much slower diffusional mobility as a major component in living cells nucleoplasm. On the bases of this analysis, we compared the diffusion property of hGRalpha in the nucleus at the presence of Dex or RU486 by distribution of diffusion constants. Our result may suggest that EGFP-hGRalpha is activated by RU486 and kept the stage of binding cofactor, GRE and final complex. Finally this means that dimerization is not required for association with GRE, although it is required for stabilization of a complex of EGFP-hGRalpha.
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http://dx.doi.org/10.1016/j.yexmp.2006.12.001DOI Listing
April 2007

Analysis of intranuclear binding process of glucocorticoid receptor using fluorescence correlation spectroscopy.

FEBS Lett 2007 Feb 18;581(3):389-93. Epub 2007 Jan 18.

Laboratory of Supramolecular Biophysics, Research Institute for Electronic Science, Hokkaido University, N12W6, Kita-ku, Sapporo 060-0812, Japan.

The diffusion properties of EGFP-hGRalpha and mutants C421G, A458T and I566 in living cells were analyzed. The wild type and mutants C421G and A458T translocated from the cytoplasm to the nucleus after addition of Dex; however, the Brownian motions of the proteins were different. The diffusion constant of wild-type GRalpha after addition of Dex slowed to 15.6% of that in the absence of Dex, whereas those of A458T and C421G slowed to 34.8% and 61.7%, respectively. This is the first report that dimer formation is less important than the binding activity of GRalpha to GRE in the living cell.
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http://dx.doi.org/10.1016/j.febslet.2006.12.038DOI Listing
February 2007

Noninvasive near-infrared blood glucose monitoring using a calibration model built by a numerical simulation method: Trial application to patients in an intensive care unit.

Appl Spectrosc 2006 Dec;60(12):1423-31

Matsushita Electric Works Ltd., Kadoma, Osaka 571-8686, Japan.

We have applied a new methodology for noninvasive continuous blood glucose monitoring, proposed in our previous paper, to patients in ICU (intensive care unit), where strict controls of blood glucose levels are required. The new methodology can build calibration models essentially from numerical simulation, while the conventional methodology requires pre-experiments such as sugar tolerance tests, which are impossible to perform on ICU patients in most cases. The in vivo experiments in this study consisted of two stages, the first stage conducted on healthy subjects as preliminary experiments, and the second stage on ICU patients. The prediction performance of the first stage was obtained as a correlation coefficient (r) of 0.71 and standard error of prediction (SEP) of 28.7 mg/dL. Of the 323 total data, 71.5% were in the A zone, 28.5% were in the B zone, and none were in the C, D, and E zones for the Clarke error-grid analysis. The prediction performance of the second stage was obtained as an r of 0.97 and SEP of 27.2 mg/dL. Of the 304 total data, 80.3% were in the A zone, 19.7% were in the B zone, and none were in the C, D, and E zones. These prediction results suggest that the new methodology has the potential to realize a noninvasive blood glucose monitoring system using near-infrared spectroscopy (NIRS) in ICUs. Although the total performance of the present monitoring system has not yet reached a satisfactory level as a stand-alone system, it can be developed as a complementary system to the conventional one used in ICUs for routine blood glucose management, which checks the blood glucose levels of patients every few hours.
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http://dx.doi.org/10.1366/000370206779321508DOI Listing
December 2006

Microenvironment and effect of energy depletion in the nucleus analyzed by mobility of multiple oligomeric EGFPs.

Biophys J 2006 Nov 1;91(10):3921-36. Epub 2006 Sep 1.

Laboratory of Supramolecular Biophysics, Research Institute for Electronic Science, Hokkaido University, Sapporo 060-0812, Japan.

Four different tandem EGFPs were constructed to elucidate the nuclear microenvironment by quantifying its diffusional properties in both aqueous solution and the nuclei of living cells. Diffusion of tandem EGFP was dependent on the length of the protein as a rod-like molecule or molecular ruler in solution. On the other hand, we found two kinds of mobility, fast diffusional mobility and much slower diffusional mobility depending on cellular compartments in living cells. Diffusion in the cytoplasm and the nucleoplasm was mainly measured as fast diffusional mobility. In contrast, diffusion in the nucleolus was complex and mainly much slower diffusional mobility, although both the fast and the slow diffusional mobilities were dependent on the protein length. Interestingly, we found that diffusion in the nucleolus was clearly changed by energy depletion, even though the diffusion in the cytoplasm and the nucleoplasm was not changed. Our results suggest that the nucleolar microenvironment is sensitive to energy depletion and very different from the nucleoplasm.
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http://dx.doi.org/10.1529/biophysj.105.079467DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1630477PMC
November 2006

Lateral mobility of membrane-binding proteins in living cells measured by total internal reflection fluorescence correlation spectroscopy.

Biophys J 2006 Nov 4;91(9):3456-64. Epub 2006 Aug 4.

Laboratory of Supramolecular Biophysics, Research Institute for Electronic Science, Hokkaido University, Sapporo, Japan.

Total internal reflection fluorescence correlation spectroscopy (TIR-FCS) allows us to measure diffusion constants and the number of fluorescent molecules in a small area of an evanescent field generated on the objective of a microscope. The application of TIR-FCS makes possible the characterization of reversible association and dissociation rates between fluorescent ligands and their receptors in supported phospholipid bilayers. Here, for the first time, we extend TIR-FCS to a cellular application for measuring the lateral diffusion of a membrane-binding fluorescent protein, farnesylated EGFP, on the plasma membranes of cultured HeLa and COS7 cells. We detected two kinds of diffusional motion-fast three-dimensional diffusion (D(1)) and much slower two-dimensional diffusion (D(2)), simultaneously. Conventional FCS and single-molecule tracking confirmed that D(1) was free diffusion of farnesylated EGFP close to the plasma membrane in cytosol and D(2) was lateral diffusion in the plasma membrane. These results suggest that TIR-FCS is a powerful technique to monitor movement of membrane-localized molecules and membrane dynamics in living cells.
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http://dx.doi.org/10.1529/biophysj.105.074625DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1614500PMC
November 2006

Characterization of optical parameters with a human forearm at the region from 1.15 to 1.52 microm using diffuse reflectance measurements.

Phys Med Biol 2006 Jun 24;51(11):2997-3011. Epub 2006 May 24.

Biophysics Laboratory, Research Institute for Electronic Science, Hokkaido University, Sapporo 060-0812, Japan.

Time- and space-resolved diffuse reflectance measurements were used to identify the optical parameters, the reduced scattering and absorption coefficients, of bulk living tissue in the region from 1.15 to 1.52 microm. Although in this region the detector was limited in its temporal resolution, we applied a peak-time shift analysis successfully to determine these coefficients in a human forearm, and then determined the absorption spectrum by space-resolved diffuse reflectance measurements. The absorption spectrum of a water content of 52% determined by magnetic resonance imaging experiments is in good agreement with the absorption coefficient obtained by optical measurements. Moreover, magnetic resonance imaging measurements suggest that the deviation of the absorption coefficients from the water spectrum in the strong water absorption band is caused by the heterogeneity of water distribution in tissue: the low content of water in the skin. These findings indicate that this optical method is potentially applicable to the non-invasive measurement of water in tissue, especially in a region lower than about 1.3-1.35 microm, which may be useful in monitoring oedema and tissue swelling.
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http://dx.doi.org/10.1088/0031-9155/51/11/021DOI Listing
June 2006

New methodology to obtain a calibration model for noninvasive near-infrared blood glucose monitoring.

Appl Spectrosc 2006 Apr;60(4):441-9

Matsushita Electric Works Ltd., Kadoma, Osaka 571-8686, Japan.

This paper reports new methodology to obtain a calibration model for noninvasive blood glucose monitoring using diffuse reflectance near-infrared (NIR) spectroscopy. Conventional studies of noninvasive blood glucose monitoring with NIR spectroscopy use a calibration model developed by in vivo experimental data sets. In order to create a calibration model, we have used a numerical simulation of light propagation in skin tissue to obtain simulated NIR diffuse reflectance spectra. The numerical simulation method enables us to design parameters affecting the prediction of blood glucose levels and their variation ranges for a data set to create a calibration model using multivariate analysis without any in vivo experiments in advance. By designing the parameters and their variation ranges appropriately, we can prevent a calibration model from chance temporal correlations that are often observed in conventional studies using NIR spectroscopy. The calibration model (regression coefficient vector) obtained by the numerical simulation has a characteristic positive peak at the wavelength around 1600 nm. This characteristic feature of the regression coefficient vector is very similar to those obtained by our previous in vitro and in vivo experimental studies. This positive peak at around 1600 nm also corresponds to the characteristic absorption band of glucose. The present study has reinforced that the characteristic absorbance of glucose at around 1600 nm is useful to predict the blood glucose level by diffuse reflectance NIR spectroscopy. We have validated this new calibration methodology using in vivo experiments. As a result, we obtained a coefficient of determination, r2, of 0.87 and a standard error of prediction (SEP) of 12.3 mg/dL between the predicted blood glucose levels and the reference blood glucose levels for all the experiments we have conducted. These results of in vivo experiments indicate that if the parameters and their vibration ranges are appropriately taken into account in a numerical simulation, the new calibration methodology provides us with a very good calibration model that can predict blood glucose levels with small errors without conducting any experiments in advance to create a calibration model for each individual patient. This new calibration methodology using numerical simulation has promising potential for NIR spectroscopy, especially for noninvasive blood glucose monitoring.
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http://dx.doi.org/10.1366/000370206776593780DOI Listing
April 2006

Amphiphilic p-sulfonatocalix[4]arene-coated CdSe/ZnS quantum dots for the optical detection of the neurotransmitter acetylcholine.

Chem Commun (Camb) 2005 Sep 11(34):4300-2. Epub 2005 Jul 11.

Section of Intelligent Materials and Devices, Research Institute for Electronic Science, Hokkaido University, Sapporo 060-0812, Japan.

Water-soluble CdSe/ZnS (core-shell) semiconductor quantum dots surface-modified with tetrahexyl ether derivatives of p-sulfonatocalix[4]arene were synthesized for the optical detection of the neurotransmitter acetylcholine.
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http://dx.doi.org/10.1039/b506608eDOI Listing
September 2005

In vivo fluorescence tracking of bone marrow stromal cells transplanted into a pneumatic injury model of rat spinal cord.

J Neurotrauma 2005 Aug;22(8):907-18

Department of Neurosurgery, Hokkaido University Graduate School of Medicine, Sapporo, Japan.

Recent experimental studies have shown that bone marrow stromal cells (BMSC) differentiate into neural cells and reduce neurological deficits when transplanted into traumatized spinal cord. These findings have been derived primarily from histological analyses. We conducted a study directed chiefly at developing a non-invasive system for tracking BMSC transplanted into the spinal cord of living animals. In this study, we induced spinal cord injury (SCI) in rats with a pneumatic device. BMSC were harvested from transgenic mice expressing green fluorescence protein (BMSC-GFP), and were transplanted stereotactically into a control group of rats without SCI (n = 6) and a group with SCI (n = 3). At 2 and 4 weeks after transplantation, the dura mater was exposed and green fluorescence derived from the transplanted BMSC-GFP was observed. The distribution and differentiation of the transplanted cells were subsequently evaluated with immunohistochemistry. Green fluorescence could be detected around the transplantation site in three of six of the control rats. In all three rats subjected to SCI, green fluorescence was shown to spread from the site of BMSC-GFP injection toward the injury site, suggesting that the transplanted cells had migrated toward the lesion within the 4-week post-transplantation period. Histological evaluation suggested that the detected green fluorescence was emitted by cells that had distributed in the dorsal white matter, and demonstrated that some of the transplanted cells expressed neuronal or astrocytic markers. These results suggest the possibility of tracking BMSC transplanted into the spinal cord in living animals. Such noninvasive bioimaging techniques would be valuable for monitoring the fate of these transplanted cells and assessing the safety and efficacy of their transplantation.
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http://dx.doi.org/10.1089/neu.2005.22.907DOI Listing
August 2005

Calixarene-coated water-soluble CdSe-ZnS semiconductor quantum dots that are highly fluorescent and stable in aqueous solution.

Chem Commun (Camb) 2005 Jun 21(22):2829-31. Epub 2005 Apr 21.

Section of Intelligent Materials and Devices, Research Institute for Electronic Science, Hokkaido University, Sapporo, 060-0812, Japan.

A simple method for the preparation of highly fluorescent and stable, water-soluble CdSe-ZnS quantum dots is reported using calix[4]arene carboxylic acids as surface coating agents; the coating of the surface with the calixarene and the conjugation of antibodies to the quantum dots are confirmed by fluorescence correlation spectroscopy.
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http://dx.doi.org/10.1039/b503178hDOI Listing
June 2005
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