Publications by authors named "Naoki Sakamoto"

9 Publications

  • Page 1 of 1

Monitoring Fluorescence Response of Amphiphilic Flapping Molecules in Compressed Monolayers at the Air-Water Interface.

Chem Asian J 2019 Aug 25;14(16):2869-2876. Epub 2019 Jul 25.

World Premier International (WPI) Centre for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, 305-0044, Japan.

The air-water interface, which is the boundary of two phases with a large difference in polarity, gives a distinct environment compared with bulk water or air. Since the interface provides a field for various biomolecules to work, it is important to understand the molecular behaviors at the interface. Here, polarity-independent flapping viscosity probes (FLAP) equipped with hydrophobic/hydrophilic substituents have been synthesized and studied at the air-water interface. In situ fluorescence (FL), which is related to the internal motion and orientation, of three different FLAPs were investigated at the interface, and the internal motion of the molecule was indicated to be suppressed at the interface. In addition, the molecular response was compared with that of conventional viscosity probes (molecular rotors), which indicates the different behaviors of FLAP probably due to the distinct molecular orientation as well as molecular motion.
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http://dx.doi.org/10.1002/asia.201900769DOI Listing
August 2019

Molecular rotors confined at an ordered 2D interface.

Phys Chem Chem Phys 2018 Jan;20(5):3073-3078

World Premier International (WPI) Centre for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba 305-0044, Japan.

Intramolecular rotation of molecules contained in a two-dimensional monolayer or a three-dimensional collapsed film at an air-water interface was investigated by in situ fluorescence spectroscopy of twisted intramolecular charge transfer (TICT) type 9-(2-carboxy-2-cyanovinyl)julolidine (CCVJ) derivatives. The TICT type molecules, CCVJ-C12 and CCVJ-Chol, that contain a linear alkyl dodecyl chain or a cholesteryl group, respectively, as their hydrophobic group, were designed and synthesized to manipulate them at the air-water interface. These lipophilized molecular rotors showed the general properties of TICT molecules in solutions that the fluorescence intensity increases with increasing viscosity of the solvent, which is induced by inhibition of internal molecular rotations. The molecular rotors CCVJ-C12 and CCVJ-Chol formed monolayers at the air-water interface and in situ fluorescence spectroscopy was performed during the in-plane compression of the monolayers. It was revealed that the monomer emissions were suppressed and only after the collapse of monolayers, excimer emission from both layers consisting of CCVJ-C12 or CCVJ-Chol was observed. Suppressed monomer emission from monolayers suggests that intramolecular rotation is not inhibited in dense ordered monolayers. Furthermore, fluorescence spectroscopy of Langmuir-Blodgett (LB) films indicated that molecular rotations are not inhibited in the monolayer transferred on the solid substrates.
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http://dx.doi.org/10.1039/c7cp04256fDOI Listing
January 2018

Relationship between interfacial hydrophobicity and hydroxylation activity of fungal cells located on an organic-aqueous interface.

J Biosci Bioeng 2013 May 29;115(5):544-6. Epub 2012 Dec 29.

Genome Biotechnology Laboratory, Kanazawa Institute of Technology, 3-1 Yatsukaho, Hakusan, Ishikawa 924-0838, Japan.

In a liquid-liquid interface bioreactor, fungal cells locate in a hydrophilic polyacrylonitrile microsphere layer on an aqueous-organic interface. In this article, effects of hydrophobicity of the interface on n-decane hydroxylation activity of Monilliera sp. NAP 00702 was examined. (-)-4-Decanol production was significantly enhanced to 132% by addition of polytetrafluoroethylene.
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http://dx.doi.org/10.1016/j.jbiosc.2012.11.017DOI Listing
May 2013

Enhancement of 6-pentyl-α-pyrone fermentation activity in an extractive liquid-surface immobilization (Ext-LSI) system by mixing anion-exchange resin microparticles.

J Biosci Bioeng 2012 Dec 5;114(6):596-9. Epub 2012 Aug 5.

Genome Biotechnology Laboratory, Kanazawa Institute of Technology, 3-1 Yatsukaho, Hakusan, Ishikawa 924-0838, Japan.

The addition of anion-exchange resin microparticles into a polyacrylonitrile (PAN) ballooned microsphere layer drastically enhanced the fermentative activity of Trichoderma atroviride AG2755-5NM398 in an extractive liquid-surface immobilization (Ext-LSI) system. The production of 6-pentyl-α-pyrone (6PP), a fungicidal secondary metabolite, was 1.92-fold higher than the control (PAN alone).
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http://dx.doi.org/10.1016/j.jbiosc.2012.07.008DOI Listing
December 2012

Profiles of ion beams and plasma parameters on a multi-frequencies microwaves large bore electron cyclotron resonance ion source with permanent magnets.

Rev Sci Instrum 2012 Feb;83(2):02A317

Division of Electrical, Electronic and Information Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita-shi, Osaka 565-0871, Japan.

In order to contribute to various applications of plasma and beams based on an electron cyclotron resonance, a new concept on magnetic field with all magnets on plasma production and confinement has been proposed with enhanced efficiency for broad and dense ion beam. The magnetic field configuration consists of a pair of comb-shaped magnet surrounding plasma chamber cylindrically. Resonance zones corresponding for 2.45 GHz and 11-13 GHz frequencies are positioned at spatially different positions. We launch simultaneously multiplex frequencies microwaves operated individually, try to control profiles of the plasma parameters and the extracted ion beams, and to measure them in detail.
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http://dx.doi.org/10.1063/1.3666184DOI Listing
February 2012

Self-assembly process of peptide amphiphile worm-like micelles.

J Phys Chem B 2012 Jan 16;116(1):240-3. Epub 2011 Dec 16.

New Business Development, Asahi-Kasei Corporation, Jinbocho, Tokyo, Japan.

Peptide amphiphile molecules (PA) are remarkably versatile and useful as building blocks for construction of complex supramolecular structures in a bottom-up fashion. Worm-like micelles of PA have been demonstrated to have successful application to creation of synthetic extracellular matrix materials for tissue engineering and regenerative medicine. However, the pathway of the self-assembly process of the PA worm-like micelle has not been fully characterized or understood. This work analyzes the self-assembly process leading to worm-like micelle formation in our designed PA with small-angle neutron scattering and atomic force microscopy. The experimental results demonstrate the existence of transient spherical micelles in the early stage of the process and subsequent micelle chain elongation by attachment of spherical micelles to the end of growing cylindrical micelles to form worm-like micelles in a process mimicking chain-growth polymerization.
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http://dx.doi.org/10.1021/jp209105zDOI Listing
January 2012

Production of electron cyclotron resonance plasma by using multifrequencies microwaves and active beam profile control on a large bore electron cyclotron resonance ion source with permanent magnets.

Rev Sci Instrum 2010 Feb;81(2):02A313

Division of Electrical, Electronic and Information Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita-shi, Osaka 565-0871, Japan.

A new concept on magnetic field with all magnets on plasma production and confinement has been proposed to enhance efficiency of an electron cyclotron resonance (ECR) plasma for broad and dense ion beam source under the low pressure. The magnetic field configuration is constructed by a pair of magnets assembly, i.e., comb-shaped magnet which cylindrically surrounds the plasma chamber. The resonance zones corresponding to the fundamental ECR for 2.45 GHz and 11-13 GHz frequencies are constructed at different positions. The profiles of the plasma parameters in the ECR ion source are different from each frequency of microwave. Large bore extractor is set at the opposite side against the microwave feeds. It is found that differences of their profiles also appear at those of ion beam profiles. We conducted to launch simultaneously multiplex frequencies microwaves controlled individually, and tried to control the profiles of the plasma parameters and then those of extracted ion beam.
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http://dx.doi.org/10.1063/1.3277195DOI Listing
February 2010

Characterization of water/AOT/benzene microemulsions during photoreduction to produce silver particles.

J Colloid Interface Sci 2010 Mar 6;343(2):423-32. Epub 2009 Dec 6.

Department of Health Science and Clothing Environment, Faculty of Human Life and Environment, Nara Women's University, Nara 630-8506, Japan.

Colloidal dispersions of silver (Ag) particles were prepared by the photoreduction of silver perchlorate (AgClO(4)) in water/AOT/benzene water-in-oil (w/o) microemulsions consisting of sodium bis(2-ethylhexyl) sulfosuccinate (AOT), water and benzene. Formation mechanisms of Ag particles prepared in the presence of benzoin by photoreduction from Ag(+)-containing w/o microemulsions were investigated by UV-vis, transmission electron microscopy (TEM), extended X-ray absorption fine structure (EXAFS) and small-angle X-ray scattering (SAXS) measurements. By a combination of TEM and EXAFS results, Ag particles show a metallic nature after the photoreduction and the diameter of Ag particles ranges between 5 and 30 nm. In situ time-resolved SAXS measurements show that the integrated rate equation can be applied in the reduction process of Ag(+) ions to Ag(0) atoms, and the autocatalytic Ag particle growth proceeds in the association process of Ag(0) atoms during the photoreduction of Ag(+)-containing w/o microemulsions. The nanometer-sized water droplets microemulsified by AOT in benzene continuous-phase regulated the size of Ag particles, and the size and shape of water droplets were retained during the Ag particle formation.
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http://dx.doi.org/10.1016/j.jcis.2009.12.006DOI Listing
March 2010

Bifunctional enzyme fusion of 3-hexulose-6-phosphate synthase and 6-phospho-3-hexuloisomerase.

Appl Microbiol Biotechnol 2007 Aug 23;76(2):439-45. Epub 2007 May 23.

Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kitashirakawa-Oiwake, Sakyo-ku, 606-8502 Kyoto, Japan.

The formaldehyde-fixing enzymes, 3-Hexulose-6-phosphate synthase (HPS) and 6-phospho-3-hexuloisomerase (PHI), are the key enzymes catalyzing sequential reactions in the ribulose monophosphate (RuMP) pathway. In this study, we generated two fused gene constructs of the hps and phi genes (i.e., hps-phi and phi-hps) from a methylotrophic bacterium Mycobacterium gastri MB19. The gene product of hps-phi exhibited both HPS and PHI activities at room temperature and catalyzed the sequential reactions more efficiently than a simple mixture of the individual enzymes. The gene product of phi-hps failed to display any enzyme activity. Escherichia coli strains harboring the hps-phi gene consumed formaldehyde more efficiently and exhibited better growth in a formaldehyde-containing medium than the host strain. Our results demonstrate that the engineered fusion gene has the possibility to be used to establish a formaldehyde-resistance detoxification system in various organisms.
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http://dx.doi.org/10.1007/s00253-007-1023-8DOI Listing
August 2007
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