Author
Takashi Hirota
Other affiliations: Kumamoto University, Nagasaki University
Bio: Takashi Hirota is an academic researcher from Okayama University. The author has contributed to research in topics: Ring (chemistry) & Formamide. The author has an hindex of 18, co-authored 224 publications receiving 1414 citations. Previous affiliations of Takashi Hirota include Kumamoto University & Nagasaki University.
Topics: Ring (chemistry), Formamide, Pyridine, Oxime, Amidine
Papers published on a yearly basis
Papers
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TL;DR: Inhibition of energy metabolism is concluded to be a mechanism of the growth inhibition effect of fullerene derivatives.
99 citations
TL;DR: The present results show that both the peptides have the ability to stimulate the release of membrane fragments out of the cells and this brings about the perforation of molecules of small size, leading to a colloid-osmotic hemolysis.
91 citations
TL;DR: The fullerene derivative C(60)-bis(N,N-dimethylpyrrolidinium iodide), a regio isomer mixture, inhibited Escherichia coli growth and dioxygen uptake caused by E. coli and glucose, indicating that the mechanism of the bacteriostatic effect is the inhibition of energy metabolism.
69 citations
TL;DR: 6-Phenyl analogs of toxoflavin (1-methyl-6-phenylpyrimido[5,4-e]-1,2, 4-triazine-5,7(1H,6H)-diones ) (7a--f) and their 4-oxides (8a- f) were synthesized by nitrosative or nitrative cyclization of the aldehyde hydrazones (6a-f) of
Abstract: 6-Phenyl analogs of toxoflavin (1-methyl-6-phenylpyrimido[5,4-e]-1,2,4-triazine-5,7(1H,6H)-diones ) (7a--f) and their 4-oxides (8a-f) were synthesized by nitrosative or nitrative cyclization of the aldehyde hydrazones (6a-f) of 6-(1-methylhydrazino)-3-phenyluracil (5). Both sets of compounds, 7a-f and 8a-f, gave the corresponding 1-demethyl derivatives (10a-f) upon treatment with nucleophiles such as dimethylformamide (DMF) and acetic acid under heating. The activities of toxoflavins (1a-e), toxoflavin 4-oxides (3a-e) and their 6-phenyl analogs (7a-f and 8a-f) against a variety of bacterial and fungal strains were examined. Most of the compounds showed strong inhibitory activities against gram-positive bacteria. Among the compounds, 1c, 1d, 1e, and 3c exhibited the strongest inhibitions of Micrococcus lutea (0.5 micrograms/ml minimal growth-inhibitory concentration) and Staphylococcus aureus 4R (1 microgram/ml), as well as Bacillus subtilis and Staphylococcus aureus (1-2 micrograms/ml). Most of the compounds had strong antifungal activity (2-100 micrograms/ml minimal growth-inhibitory concentration) against Candida albicans and Saccharomyces cerevisiae.
56 citations
TL;DR: It was concluded that, if peptides can expand greatly the membrane structure of neutral lipids which constitute main parts of the biological membrane, they can stimulate the permeability of cells without any selectivity.
52 citations
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TL;DR: This review critiques existing nanomaterial research in freshwater, marine, and soil environments and illustrates the paucity of existing research and demonstrates the need for additional research.
Abstract: The recent advances in nanotechnology and the corresponding increase in the use of nanomaterials in products in every sector of society have resulted in uncertainties regarding environmental impacts. The objectives of this review are to introduce the key aspects pertaining to nanomaterials in the environment and to discuss what is known concerning their fate, behavior, disposition, and toxicity, with a particular focus on those that make up manufactured nanomaterials. This review critiques existing nanomaterial research in freshwater, marine, and soil environments. It illustrates the paucity of existing research and demonstrates the need for additional research. Environmental scientists are encouraged to base this research on existing studies on colloidal behavior and toxicology. The need for standard reference and testing materials as well as methodology for suspension preparation and testing is also discussed.
2,566 citations
TL;DR: It is concluded that, among naturally produced peptides that are investigated, only alamethicin conforms to the barrel-stave model, and other peptides, including magainins, melittin and protegrins, all appear to induce transmembrane pores that conform to the toroidal model.
1,013 citations
TL;DR: In this paper, the main achievements in the field of excited-state properties of fullerene derivatives are reviewed, and the photosensitizing and electron-acceptor features of some relevant classes of functionalized materials are highlighted.
Abstract: This Account reviews our main achievements in the field of excited-state properties of fullerene derivatives. The photosensitizing and electron-acceptor features of some relevant classes of functionalized fullerene materials are highlighted, considering the impact of functionalization on fullerene characteristics. In addition, the unique optimization in terms of redox potentials, water-solubility, and singlet oxygen generation is presented for several novel fullerene-based materials.
1,010 citations