Kazuma Yasuhara
Nara Institute of Science and Technology
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Publication
Featured researches published by Kazuma Yasuhara.
Macromolecular Bioscience | 2013
Haruko Takahashi; Edmund F. Palermo; Kazuma Yasuhara; Gregory A. Caputo; Kenichi Kuroda
There is an urgent need for new antibiotics which are effective against drug-resistant bacteria without contributing to resistance development. We have designed and developed antimicrobial copolymers with cationic amphiphilic structures based on the mimicry of naturally occurring antimicrobial peptides. These copolymers exhibit potent antimicrobial activity against a broad spectrum of bacteria including methicillin-resistant Staphylococcus aureus with no adverse hemolytic activity. Notably, these polymers also did not result in any measurable resistance development in E. coli. The peptide-mimetic design principle offers significant flexibility and diversity in the creation of new antimicrobial materials and their potential biomedical applications.
Chemical Communications | 2011
Kazuma Yasuhara; Shohei Miki; Hajime Nakazono; Akio Ohta; Jun-ichi Kikuchi
Well-defined hybrid nanodiscs were produced by employing bicelle formation of a binary lipid mixture in water. The resulting nanoparticles have a lipid bilayer coated with ceramic layers, which are formed by the sol-gel reaction among the alkoxysilyl headgroups of the hybrid lipid. The hybrid bicelles displayed significant morphological stability against dry environments and surfactant addition, in stark contrast to conventional phospholipid bicelles.
Colloids and Surfaces B: Biointerfaces | 2008
Kazuma Yasuhara; Yoshihiro Sasaki; Jun-ichi Kikuchi
A novel fluorescent sensor responsive to local viscosity in the lipid bilayer membranes was designed and synthesized. The sensor changes its fluorescence intensity reflecting the local viscosity of its surrounding medium. The fluorescence measurement showed that the sensor is capable of discriminating between different phase states of lipid bilayer. In addition, the sensor visualized liquid-ordered microdomains on giant vesicles in terms of the microviscosity with a simple fluorescence technique.
Journal of the American Chemical Society | 2016
Tomoki Ogoshi; Ryuta Sueto; Kumiko Yoshikoshi; Kazuma Yasuhara; Tada-aki Yamagishi
Mixing cyclic pentagonal pillar[5]quinone with cyclic hexagonal pillar[6]arene in a 12:20 molar feed ratio resulted in spontaneous production of vesicles, while assembly of pillar[6]arene and pillar[5]quinone alone produced hexagonal disks and wires, respectively. Incorporation of pentagonal pillar[5]quinone rings into hexagonal pillar[6]arene sheets gave curvature and contributed to the formation of vesicles. Conventional vesicles are generally synthesized by assembly of amphiphilic molecules containing hydrophobic and hydrophilic parts. Therefore, the co-assembly of pentagonal and hexagonal molecules to obtain spherical vesicles demonstrated in this study is a new concept based on geometric design.
Chemical Communications | 2014
Manami Tsukamoto; Kenichi Kuroda; Ayyalusamy Ramamoorthy; Kazuma Yasuhara
The function and mode of action of curcumin in modulating the formation of lipid raft domains were investigated by microscopic observation using model membranes. Curcumin induces fusion of lipid raft domains at extremely low concentrations through the alteration of the boundary between the ordered and disordered phases.
RSC Advances | 2015
Atsushi Ikeda; Shodai Hino; Tomoya Mae; Yuki Tsuchiya; Kouta Sugikawa; Manami Tsukamoto; Kazuma Yasuhara; Hajime Shigeto; Hisakage Funabashi; Akio Kuroda; Motofusa Akiyama
The water-solubilisation of porphyrin derivatives is very important for biological applications. Although liposomal drug carriers for porphyrin derivatives have shown significant promise in the field of medicinal chemistry (e.g., as sensitisers for photodynamic therapy), it is currently not possible to prepare lipid-membrane-incorporated tetraphenylporphyrin (TPP) with a high concentration of TPP using conventional methods. In this study, we have succeeded in preparing lipid-membrane-incorporated TPP and zinc(II) tetraphenylporphyrin (ZnTPP) from the corresponding TPP or ZnTPP·cyclodextrin complex using the exchange method in lipid-membranes composed of liposomes. Furthermore, the exchange method allowed for the incorporation of TPP or ZnTPP into the plasma membranes of HeLa cells. However, it was not possible to prepare lipid-membrane-incorporated porphyrin derivatives with polar and hydrophilic groups in the meso positions using this exchange reaction.
Journal of the American Chemical Society | 2017
Kazuma Yasuhara; Jin Arakida; Thirupathi Ravula; Sudheer Kumar Ramadugu; Bikash Sahoo; Jun-ichi Kikuchi; Ayyalusamy Ramamoorthy
There is a growing interest in the use of lipid bilayer nanodiscs for various biochemical and biomedical applications. Among the different types of nanodiscs, the unique features of synthetic polymer-based nanodiscs have attracted additional interest. A styrene-maleic acid (SMA) copolymer demonstrated to form lipid nanodiscs has been used for structural biology related studies on membrane proteins. However, the application of SMA polymer based lipid nanodiscs is limited because of the strong absorption of the aromatic group interfering with various experimental measurements. Thus, there is considerable interest in the development of other molecular frameworks for the formation of polymer-based lipid nanodiscs. In this study, we report the first synthesis and characterization of a library of polymethacrylate random copolymers as alternatives to SMA polymer. In addition, we experimentally demonstrate the ability of these polymers to form lipid bilayer nanodiscs through the fragmentation of lipid vesicles by means of light scattering, electron microscopy, differential scanning calorimetry, and solution and solid-state NMR experiments. We further demonstrate a unique application of the newly developed polymer for kinetics and structural characterization of the aggregation of human islet amyloid polypeptide (also known as amylin) within the lipid bilayer of the polymer nanodiscs using thioflavin-T-based fluorescence and circular dichroism experiments. Our results demonstrate that the reported new styrene-free polymers can be used in high-throughput biophysical experiments. Therefore, we expect that the new polymer nanodiscs will be valuable in the structural studies of amyloid proteins and membrane proteins by various biophysical techniques.
Angewandte Chemie | 2016
Kouta Sugikawa; Tatsuya Kadota; Kazuma Yasuhara; Atsushi Ikeda
The behavior of self-assembly processes of nanoscale particles on plasma membranes can reveal mechanisms of important biofunctions and/or intractable diseases. Self-assembly of citrate-coated gold nanoparticles (cAuNPs) on liposomes was investigated. The adsorbed cAuNPs were initially fixed on the liposome surfaces and did not self-assemble below the phospholipid phase transition temperature (Tm ). In contrast, anisotropic cAuNP self-assembly was observed upon heating of the composite above the Tm, where the phospholipids became fluid. The number of self-assembled NPs is conveniently controlled by the initial mixing ratio of cAuNPs and liposomes. Gold nanoparticle protecting agents strongly affected the self-assembly process on the fluidic membrane.
Langmuir | 2014
Atsushi Ikeda; Kazuya Kiguchi; Tomohiro Hida; Kazuma Yasuhara; Kazuyuki Nobusawa; Motofusa Akiyama; Wataru Shinoda
The incorporation of neutral [70]fullerenes (C70) led to bicelle formation in a relatively low lipid concentration range from neutral lipid mixtures (DMPC/DHPC). Furthermore, C70 addition resulted in the formation of large bicelles with a radius of ca. 100 nm, in contrast to C70-free bicelles that were formed from anionic lipid mixtures (DMPC/DHPC/DMPG). The stabilization of these bicelles was attributed to C70 incorporation into the membranes.
ChemBioChem | 2014
Sendy Junedi; Kazuma Yasuhara; Satoshi Nagao; Jun-ichi Kikuchi; Shun Hirota
Monomeric cyt c has been reported to bind to the mitochondrial membrane by electrostatic and hydrophobic interactions with anionic phospholipids. We have previously shown that domain‐swapped oligomeric cyt c retains the secondary structure of the monomer, and its surface possesses a larger area and more charges compared to the monomer. However, the effect of oligomerization of cyt c on cells has yet to be revealed. Herein, we investigated the interaction of oligomeric cyt c with anionic phospholipid‐containing vesicles and the outer membrane of HeLa cells. Oligomeric cyt c interacted more strongly than monomeric cyt c with anionic phospholipid‐containing vesicles and the outer membrane of HeLa cells. Oligomeric cyt c induced lateral phase separation of lipids in LUVs and GUVs, thereby leading to membrane disruption, whereas monomeric cyt c did not. Morphological changes in HeLa cells resulted from interaction with oligomeric cyt c, but little from interaction with the monomer. These results show that domain‐swapped oligomeric proteins might exhibit properties different to those of monomer in cell systems.