Publications by authors named "Yasuhiro Kubota"

43 Publications

Short Radiative Lifetime and Non-Triplet Sensitization in Near-Infrared-Luminescent Yb(III) Complex with Tripodal Schiff Base.

ChemistryOpen 2021 Jan;10(1):46-55

Graduate School of Environmental Studies, Tohoku University, 6-6-07 Aramaki-aza Aoba, Aoba-ku Sendai, Miyagi, 980-8579, Japan.

We prepared Ln(III) (Ln=Eu, Gd, and Yb) complexes with a tripodal Schiff base, tris[2-(5-methylsalicylideneimino)ethyl]amine (H L) and studied their photophysical properties. Upon ligand excitation, YbL showed Yb(III)-centered luminescence in the near-infrared region. While the overall quantum yield (0.60(1)%) of YbL in acetonitrile was moderate among the reported values for Yb(III) complexes, its radiative lifetime (0.33(2) ms) was significantly shorter than those reported previously. We propose that the ligand-to-metal charge-transfer (LMCT) state mediated the sensitization in YbL. The emission and excitation spectra of EuL indicated the participation of the LMCT state in the sensitization. The radiative lifetime (0.84(7) ms) for EuL in the solid state was rather short compared to those of reported Eu(III) complexes. Our results show that the Yb(III) complex with the Schiff base ligand has two features: the short radiative lifetime and the non-triplet sensitization path.
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http://dx.doi.org/10.1002/open.202000224DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7819271PMC
January 2021

Highly diastereo- and enantioselective organocatalytic synthesis of trifluoromethylated erythritols based on the generation of unstable trifluoroacetaldehyde.

Org Biomol Chem 2021 02;19(6):1296-1304

Department of Chemistry and Biomolecular Science, Gifu University, 1-1, Yanagido, Gifu 501-1193, Japan.

Thus far, only a few methods for the asymmetric synthesis of erythritols bearing a trifluoromethyl group have been developed, and these methods present serious disadvantages such as the requirement of multiple steps for the preparation of their starting materials, low stereoselectivity, and the use of highly toxic reagents. Herein, we have developed a highly diastereo- and enantioselective organocatalytic method to synthesise erythritols bearing a trifluoromethyl group using (1) a commercially available organocatalyst to produce unstable trifluoroacetaldehyde in situ from its corresponding hemiacetal, followed by the simultaneous asymmetric carbon-carbon bond-forming reaction of the organocatalyst with an in situ-generated chiral enamine derived from 2,2-dimethyl-1,3-dioxane-5-one to obtain the corresponding aldol product in good yield (65-80%) with high diastereoselectivity (up to 94% de) and excellent enantioselectivity (up to >98% ee), (2) the highly diastereoselective reduction of the ketone moiety in the aldol product (up to 98% de), and (3) the deprotection of the acetal moiety.
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http://dx.doi.org/10.1039/d0ob02067bDOI Listing
February 2021

Multiple drivers of the COVID-19 spread: The roles of climate, international mobility, and region-specific conditions.

PLoS One 2020 23;15(9):e0239385. Epub 2020 Sep 23.

Faculty of Science, University of the Ryukyus, Okinawa, Japan.

Following its initial appearance in December 2019, coronavirus disease 2019 (COVID-19) quickly spread around the globe. Here, we evaluated the role of climate (temperature and precipitation), region-specific COVID-19 susceptibility (BCG vaccination factors, malaria incidence, and percentage of the population aged over 65 years), and human mobility (relative amounts of international visitors) in shaping the geographical patterns of COVID-19 case numbers across 1,020 countries/regions, and examined the sequential shift that occurred from December 2019 to June 30, 2020 in multiple drivers of the cumulative number of COVID-19 cases. Our regression model adequately explains the cumulative COVID-19 case numbers (per 1 million population). As the COVID-19 spread progressed, the explanatory power (R2) of the model increased, reaching > 70% in April 2020. Climate, host mobility, and host susceptibility to COVID-19 largely explained the variance among COVID-19 case numbers across locations; the relative importance of host mobility and that of host susceptibility to COVID-19 were both greater than that of climate. Notably, the relative importance of these factors changed over time; the number of days from outbreak onset drove COVID-19 spread in the early stage, then human mobility accelerated the pandemic, and lastly climate (temperature) propelled the phase following disease expansion. Our findings demonstrate that the COVID-19 pandemic is deterministically driven by climate suitability, cross-border human mobility, and region-specific COVID-19 susceptibility. The identification of these multiple drivers of the COVID-19 outbreak trajectory, based on mapping the spread of COVID-19, will contribute to a better understanding of the COVID-19 disease transmission risk and inform long-term preventative measures against this disease.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0239385PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7510993PMC
October 2020

Past and future decline of tropical pelagic biodiversity.

Proc Natl Acad Sci U S A 2020 06 26;117(23):12891-12896. Epub 2020 May 26.

Faculty of Science, University of the Ryukyus, 903-0213 Okinawa, Japan.

A major research question concerning global pelagic biodiversity remains unanswered: when did the apparent tropical biodiversity depression (i.e., bimodality of latitudinal diversity gradient [LDG]) begin? The bimodal LDG may be a consequence of recent ocean warming or of deep-time evolutionary speciation and extinction processes. Using rich fossil datasets of planktonic foraminifers, we show here that a unimodal (or only weakly bimodal) diversity gradient, with a plateau in the tropics, occurred during the last ice age and has since then developed into a bimodal gradient through species distribution shifts driven by postglacial ocean warming. The bimodal LDG likely emerged before the Anthropocene and industrialization, and perhaps ∼15,000 y ago, indicating a strong environmental control of tropical diversity even before the start of anthropogenic warming. However, our model projections suggest that future anthropogenic warming further diminishes tropical pelagic diversity to a level not seen in millions of years.
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http://dx.doi.org/10.1073/pnas.1916923117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7293716PMC
June 2020

Climate and land-use interactively shape butterfly diversity in tropical rainforest and savanna ecosystems of southwestern China.

Insect Sci 2020 May 26. Epub 2020 May 26.

Faculty of Science, University of the Ryukyus, Nishihara, Okinawa, Japan.

Human-induced habitat conversion and degradation, along with accelerating climatic change, have resulted in considerable global biodiversity loss. Nevertheless, how local ecological assemblages respond to the interplay between climate and land-use change remains poorly understood. Here, we examined the effects of climate and land-use interactions on butterfly diversity in different ecosystems of southwestern China. Specifically, we investigated variation in the alpha and beta diversities of butterflies in different landscapes along human-modified and climate gradients. We found that increasing land-use intensity not only caused a dramatic decrease in butterfly alpha diversity but also significantly simplified butterfly species composition in tropical rainforest and savanna ecosystems. These findings suggest that habitat modification by agricultural activities increases the importance of deterministic processes and leads to biotic homogenization. The land-use intensity model best explained species richness variation in the tropical rainforest, whereas the climate and land-use intensity interaction model best explained species richness variation in the savanna. These results indicate that climate modulates the effects of land-use intensity on butterfly alpha diversity in the savanna ecosystem. We also found that the response of species composition to climate varied between sites: specifically, species composition was strongly correlated with climatic distance in the tropical rainforest but not in the savanna. Taken together, our long-term butterfly monitoring data reveal that interactions between human-modified habitat change and climate change have shaped butterfly diversity in tropical rainforest and savanna. These findings also have important implications for biodiversity conservation under the current era of rapid human-induced habitat loss and climate change.
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http://dx.doi.org/10.1111/1744-7917.12824DOI Listing
May 2020

Colonize, radiate, decline: Unraveling the dynamics of island community assembly with Fijian trap-jaw ants.

Evolution 2020 06 10;74(6):1082-1097. Epub 2020 May 10.

Biodiversity and Biocomplexity Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa, 904-0495, Japan.

The study of island community assembly has been fertile ground for developing and testing theoretical ideas in ecology and evolution. The ecoevolutionary trajectory of lineages after colonization has been a particular interest, as this is a key component of understanding community assembly. In this system, existing ideas, such as the taxon cycle, posit that lineages pass through a regular sequence of ecoevolutionary changes after colonization, with lineages shifting toward reduced dispersal ability, increased ecological specialization, and declines in abundance. However, these predictions have historically been difficult to test. Here, we integrate phylogenomics, population genomics, and X-ray microtomography/3D morphometrics, to test hypotheses for whether the ecomorphological diversity of trap-jaw ants (Strumigenys) in the Fijian archipelago is assembled primarily through colonization or postcolonization radiation, and whether species show ecological shifts toward niche specialization, toward upland habitats, and decline in abundance after colonization. We infer that most Fijian endemic Strumigenys evolved in situ from a single colonization and have diversified to fill a large fraction of global morphospace occupied by the genus. Within this adaptive radiation, lineages trend to different degrees toward high elevation, reduced dispersal ability, and demographic decline, and we find no evidence of repeated colonization that displaces the initial radiation. Overall these results are only partially consistent with taxon cycle and associated ideas, while highlighting the potential role of priority effects in assembling island communities.
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http://dx.doi.org/10.1111/evo.13983DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7384189PMC
June 2020

Integrating multiple sources of ecological data to unveil macroscale species abundance.

Nat Commun 2020 04 3;11(1):1695. Epub 2020 Apr 3.

Faculty of Science, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa, 903-0213, Japan.

The pattern of species abundance, represented by the number of individuals per species within an ecological community, is one of the fundamental characteristics of biodiversity. However, despite their obvious significance in ecology and biogeography, there is still no clear understanding of these patterns at large spatial scales. Here, we develop a hierarchical modelling approach to estimate macroscale patterns of species abundance. Using this approach, estimates of absolute abundance of 1248 woody plant species at a 10-km-grid-square resolution over East Asian islands across subtropical to temperate biomes are obtained. We provide two examples of the basic and applied use of the estimated species abundance for (1) inference of macroevolutionary processes underpinning regional biodiversity patterns and (2) quantitative community-wide assessment of a national red list. These results highlight the potential of the elucidation of macroscale species abundance that has thus far been an inaccessible but critical property of biodiversity.
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http://dx.doi.org/10.1038/s41467-020-15407-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7125090PMC
April 2020

Iron-Promoted Intramolecular Cascade Cyclization for the Synthesis of Selenophene-Fused, Quinoline-Based Heteroacenes.

J Org Chem 2019 07 25;84(13):8602-8614. Epub 2019 Jun 25.

Department of Chemistry and Biomolecular Science, Faculty of Engineering , Gifu University , Gifu 501-1193 , Japan.

Herein, we report the Fe(III)-promoted linear intramolecular cascade cyclization of 1,3-diyne and 1,3,5-triyne for the construction of selenophene-fused, quinoline-based heteroacene scaffolds. In one step, 1,3-diyne and 1,3,5-triyne were cyclized via diversified internal nucleophiles by using diorganyl diselenides. The diorganyl diselenide plays dual role, one as a cyclizing agent and second as insertion of one and/or two selenium atom and one R'-Se group in the final product. This is highly important in terms of atom economy. Diversified internal nucleophiles were used to afford quinoline- and acridine-based cores. The synthesized selenophene-fused derivatives showed λ, F, and Φ values in the range from 370-411 nm, 427-472 nm, and 0.003-0.059, respectively, in dichloromethane solvent.
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http://dx.doi.org/10.1021/acs.joc.9b01061DOI Listing
July 2019

Aromatic Fluorine-Induced One-Pot Synthesis of Ring-Perfluorinated Trimethine Cyanine Dye and Its Remarkable Fluorescence Properties.

J Org Chem 2019 Apr 27;84(7):4372-4380. Epub 2019 Mar 27.

Rigaku Corporation , 3-9-12 Matsubara-cho , Akishima, Tokyo 196-8666 , Japan.

We have developed a novel aromatic fluorine-induced one-pot synthesis of ring-perfluorinated trimethine cyanine dye without the use of a pyridine by reacting hexafluorobenzoindolenine with 5 equiv of methyl trifluoromethanesulfonate in mixed solvents of dimethylformamide and toluene. The thus-obtained ring-perfluorinated trimethine cyanine dye shows much better fluorescence properties, including intensity, quantum yield, and lifetime, than the nonfluorinated dye, not only in CHCl solution and the poly(methyl methacrylate) film but also in the powder state. Furthermore, ring-perfluorinated trimethine cyanine dye 2a shows better photostability toward white light-emitting diode irradiation than nonfluorinated dye trimethine cyanine dye 2b.
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http://dx.doi.org/10.1021/acs.joc.9b00378DOI Listing
April 2019

A geometric approach to scaling individual distributions to macroecological patterns.

J Theor Biol 2019 01 16;461:170-188. Epub 2018 Oct 16.

Biodiversity and Biocomplexity Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa 904-0495, Japan.

Understanding macroecological patterns across scales is a central goal of ecology and a key need for conservation biology. Much research has focused on quantifying and understanding macroecological patterns such as the species-area relationship (SAR), the endemic-area relationship (EAR) and relative species abundance curve (RSA). Understanding how these aggregate patterns emerge from underlying spatial pattern at individual level, and how they relate to each other, has both basic and applied relevance. To address this challenge, we develop a novel spatially explicit geometric framework to understand multiple macroecological patterns, including the SAR, EAR, RSA, and their relationships. First, we provide a general theory that can be used to derive the asymptotic slopes of the SAR and EAR, and demonstrates the dependency of RSAs on the shape of the sampling region. Second, assuming specific shapes of the sampling region, species geographic ranges, and individual distribution patterns therein based on theory of stochastic point processes, we demonstrate various well-documented macroecological patterns can be recovered, including the tri-phasic SAR and various RSAs (e.g., Fisher's logseries and the Poisson lognormal distribution). We also demonstrate that a single equation unifies RSAs across scales, and provide a new prediction of the EAR. Finally, to demonstrate the applicability of the proposed model to ecological questions, we provide how beta diversity changes with spatial extent and its grain over multiple scales. Emergent macroecological patterns are often attributed to ecological and evolutionary mechanisms, but our geometric approach still can recover many previously observed patterns based on simple assumptions about species geographic ranges and the spatial distribution of individuals, emphasizing the importance of geometric considerations in macroecological studies.
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http://dx.doi.org/10.1016/j.jtbi.2018.10.030DOI Listing
January 2019

Wide-Range Near-Infrared Sensitizing 1 H-Benzo[ c, d]indol-2-ylidene-Based Squaraine Dyes for Dye-Sensitized Solar Cells.

J Org Chem 2018 04 3;83(8):4389-4401. Epub 2018 Apr 3.

Department of Chemistry and Biomolecular Scienece, Faculty of Engineering , Gifu University , 1-1 Yanagido , Gifu 501-1193 , Japan.

NIR absorbing squaraine dyes SQ1-SQ7 having 1 H-benzo[ c, d]indol-2-ylidene as a donor moiety were designed for application in DSSCs. Annulation of the benzene ring to an 3 H-indolium-based anchor moiety led to a red-shifted and broadened absorption band on TiO film, which were reflected in the improved short-circuit current density of SQ2 (6.22 mA cm) compared to the nonbenzene fused derivative SQ1 (4.39 mA cm). Although the introduction of a butoxy (SQ4: 806 nm) or dialkylamino group (SQ5-SQ7: 815-820 nm) to the 1 H-benzo[ c, d]indol-2-ylidene-based donor moiety resulted in red-shifted absorption maxima in ethanol compared to the nonsubstituted derivative SQ2 (784 nm), the HOMO energy level of SQ4-SQ7 gave rise to an undesirable approximation to the redox potential of I/I. Thus, the butoxy (SQ4: 0.56) and dialkylamino (SQ5-SQ7: 0.25-0.30) derivatives had relatively lower conversion efficiencies. Since the 2-ethylhexyl derivative SQ3 exhibited red-shifted absorption (λ: 796 nm), suitable HOMO and LUMO energy levels, and relatively efficient restriction of charge recombination, this dye achieved the highest conversion efficiency (1.31%), along with a high IPCE response of over 20% over a wide range from 640 to 860 nm and an onset of IPCE at 1000 nm.
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http://dx.doi.org/10.1021/acs.joc.8b00070DOI Listing
April 2018

Rational Molecular Design and Synthesis of Highly Thermo- and Photostable Near-Infrared-Absorbing Heptamethine Cyanine Dyes with the Use of Fluorine Atoms.

Chemistry 2016 Aug 22;22(35):12282-5. Epub 2016 Jul 22.

Department of Chemistry and Biomolecular Science, Gifu University, 1-1 Yanagido, Gifu, Japan.

Highly thermo- and photostable, near-infrared-absorbing heptamethine cyanine dyes were achieved with the use of fluorine-containing components. In particular, one prepared heptamethine cyanine dye, bearing a tetrakis(pentafluorophenyl)borate as a counter anion and an N-ethyl-2,2,2-trifluoroacetamido group at the meso position, showed not only a high decomposition temperature (Tdt ), but also very high photostability toward white LED irradiation.
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http://dx.doi.org/10.1002/chem.201602955DOI Listing
August 2016

Synthesis and Fluorescence Properties of Pyrimidine-Based Diboron Complexes with Donor-π-Acceptor Structures.

Chemistry 2016 Jan 16;22(5):1816-24. Epub 2015 Dec 16.

Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan.

Pyrimidine-based diboron complexes bearing β-iminoenolate ligands and phenyl groups as bulky substituents on the boron atoms were synthesized as novel fluorescent dyes, and their fluorescence properties were investigated in solution and in the solid state. The diboron complexes with donor-π-acceptor structures showed positive solvatochromism in the fluorescence spectra. The cyano derivative exhibited the most dramatic redshift of the fluorescence maximum Fmax with increasing solvent polarity (from 551 nm in n-hexane to 710 nm in acetonitrile). The diboron complexes showed solid-state fluorescence in the range of 578-706 nm with fluorescence quantum yields of 0.06-0.28. Additionally, the trifluoromethyl derivative exhibited solvent-inclusion solid-state fluorescence. The trifluoromethyl derivative formed toluene-inclusion and ethyl acetate-inclusion crystals. The toluene-inclusion crystal (Fmax = 668 nm, Φf = 0.16) showed a blueshifted Fmax and higher Φf value compared to the original trifluoromethyl derivative (Fmax = 694 nm, Φf = 0.08) in the solid state. On the other hand, the Fmax (709 nm) and Φf (0.04) values of the ethyl acetate-inclusion crystal were redshifted and lower, respectively.
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http://dx.doi.org/10.1002/chem.201503625DOI Listing
January 2016

A Direct, Concise, and Enantioselective Synthesis of 2-Substituted 4,4,4-Trifluorobutane-1,3-diols Based on the Organocatalytic In Situ Generation of Unstable Trifluoroacetaldehyde.

Chem Asian J 2015 Dec 17;10(12):2701-7. Epub 2015 Aug 17.

Department of Chemistry and Biomolecular Science, Gifu University, 1-1 Yanagido, Gifu, Japan.

A direct, concise, and enantioselective synthesis of 2-substituted 4,4,4-trifluorobutane-1,3-diols based on the organocatalytic asymmetric direct aldol reaction of an ethyl hemiacetal of trifluoroacetaldehyde with various aldehydes was examined. A catalytic amount (30 mol %) of commercially available and inexpensive l-prolinamide is quite effective as an organocatalyst for the catalytic in situ generation of gaseous and unstable trifluoroacetaldehyde from its hemiacetal, and a successive asymmetric direct aldol reaction with various aldehydes in dichloromethane at 0 °C, followed by reduction with sodium borohydride, gives 2-substituted 4,4,4-trifluorobutane-1,3-diols in moderate to good yields (31-84%) with low diastereoselectivities and good to excellent enantioselectivities (64-97% ee).
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http://dx.doi.org/10.1002/asia.201500607DOI Listing
December 2015

Synthesis, Absorption, and Electrochemical Properties of Quinoid-Type Bisboron Complexes with Highly Symmetrical Structures.

Org Lett 2015 Jun 11;17(12):3174-7. Epub 2015 Jun 11.

†Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University, Yanagido, Gifu 501-1193, Japan.

Novel bisboron complexes of bidentate ligands consisting of 1,4-benzoquinone and two pyrrole rings were synthesized by using a simple two-step reaction. In solution, the bisboron complexes showed absorption maxima at ∼620 and 800 nm, which were attributed to the allowed S0 → S2 and forbidden S0 → S1 transitions, respectively. The bisboron complexes did not show any fluorescence, probably because of their highly symmetrical structure which forbids the S0 → S1 transition. Bisboron complexes underwent a two-electron reduction to yield the corresponding aromatic dianion, which showed absorption maxima at ∼410 nm.
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http://dx.doi.org/10.1021/acs.orglett.5b01547DOI Listing
June 2015

Strategy to enhance solid-state fluorescence and aggregation-induced emission enhancement effect in pyrimidine boron complexes.

Dalton Trans 2015 Feb;44(7):3326-41

Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan.

The synthesis and the solution/solid-state fluorescence properties of pyrimidine-based monoboron complexes differing in terms of the substituents [either two fluorine atoms (BF2 complex) or two phenyl groups (BPh2 complex)] on the boron atom are reported herein. Unrestricted C-Ar intramolecular rotation in the non-, trifluoromethyl-, and cyano-substituted derivatives resulted in negligible fluorescence in solution. On the other hand, methoxy- and dimethylamino-substituted analogues caused the restriction of the C-Ar intramolecular rotation and consequently resulted in relatively strong fluorescence in solution. The non-, trifluoromethyl-, and cyano-substituted derivatives showed a pronounced aggregation-induced emission enhancement effect. Dimethylamino-substituted derivatives exhibited solvatochromism in the fluorescence spectra. Substitution with BPh2 effectively enhanced the fluorescence quantum yield compared to the corresponding BF2 complexes in the solid-state.
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http://dx.doi.org/10.1039/c4dt03318cDOI Listing
February 2015

Solvatochromic fluorescence properties of pyrazine-boron complex bearing a β-iminoenolate ligand.

J Phys Chem A 2014 Sep 11;118(38):8717-29. Epub 2014 Sep 11.

Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University , 1-1 Yanagido, Gifu 501-1193, Japan.

Pyrazine-based monoboron complexes bearing two fluorine atoms (BF2 complex) or two phenyl groups (BPh2 complex) on the boron atom were synthesized, and the fluorescence properties were investigated. The BPh2 complexes exhibited red-shifted maximum absorption and maximum fluorescence wavelengths and lower molar absorption coefficients than the corresponding BF2 complexes in n-hexane. The fluorescence quantum yields of the BPh2 complexes were higher than or comparable to the corresponding BF2 complexes owing to the relatively low nonradiative rate constants. Although the nonsubstituted and trifluoromethyl-substituted derivatives did not show solvatochromism, the dimethylamino-substituted BF2 and BPh2 complexes exhibited pronounced solvatochromism in the fluorescence spectra. Dual fluorescence was observed for the dimethylamino-substituted BF2 complex in toluene, 1,4-dioxane, and chloroform, corresponding to locally excited (LE) and twisted intramolecular charge-transfer (TICT) states.
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http://dx.doi.org/10.1021/jp506680gDOI Listing
September 2014

Development of Canine Models of Type 1 Diabetes With Partial Pancreatectomy and the Administration of Streptozotocin.

Cell Med 2013 Dec 21;6(1-2):25-31. Epub 2013 Oct 21.

Department of Gastroenterological Surgery, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences , Okayama , Japan.

We created canine models of type 1 diabetes that were suitable for the assessment of cell therapies, such as islet transplantation and bioartificial pancreas, with low-dose streptozotocin (STZ) injection and partial pancreatectomy. In our model, a 50% pancreatectomy was performed with general anesthesia, followed by systemic injection of 35 mg/kg STZ into a vein of the foreleg. Four weeks after the administration of STZ, the fasting blood glucose level of our model dogs was found to be over 200 mg/dl twice on different days, and we could not detect any canine insulin by the intravenous glucose tolerance test (IVGTT). We therefore diagnosed the dogs to have induced diabetes. Some studies have reported high-dose STZ to be very toxic for both the kidney and liver, and therefore a lower dose is desirable to induce diabetic models without any associated kidney or liver damage. We think that the combination of a partial pancreatectomy can thus make it possible to reduce the dose of STZ, and it is therefore useful for the creation of type 1 diabetes models. We believe that our model is a safe and reliable model for type 1 diabetes in canines to assess the efficacy of pancreas-targeted cell therapies.
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http://dx.doi.org/10.3727/215517913X674289DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4735883PMC
December 2013

Maintenance of Viability and Function of Rat Islets With the Use of ROCK Inhibitor Y-27632.

Cell Med 2013 Dec 21;6(1-2):15-23. Epub 2013 Oct 21.

Department of Gastroenterological Surgery, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences , Okayama , Japan.

The number of patients with diabetes is on an increasing trend, thus leading to the belief that diabetes will be the largest medical problem of the 21st century. Islet transplantation can improve glycometabolic control in patients with type 1 diabetes. We studied the viability of Rho-associated protein kinase (ROCK) inhibitor Y-27632 in a culture system in vitro on freshly isolated rat islets. Islet isolation was conducted on a Lewis rat, and studies of culture solutions were split into two groups, one group using ROCK inhibitor Y-27632, and another without. On the seventh day of culture, we evaluated the differences for the cell morphology, viability, and insulin secretion. The Y-27632 group maintained form better than the group without Y-27632. With strong expression of Bcl-2 observed with the Y-27632 group, and expression suppressed with Bax, inhibition of apoptosis by Y-27632 was confirmed. The Y-27632 group predominantly secreted insulin. For islet transplantation, Y-27632 inhibited cell apoptosis in a graft and was also effective in promoting insulin secretion. We were able to confirm effective morphological and functional culture maintenance by separating islets from a rat and adding ROCK inhibitor Y-27632 to the medium.
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http://dx.doi.org/10.3727/215517913X674199DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4735882PMC
December 2013

[The impact of guidelines for the management of acute cholecystitis in a rural area of Japan].

Nihon Shokakibyo Gakkai Zasshi 2013 Oct;110(10):1774-82

Department of Internal Medicine, Tsuyama Central Hospital.

We monitored the management of acute cholecystitis in a rural area of Japan to determine the effectiveness of new guidelines for the management of acute cholecystitis and cholangitis. Between January 2000 and September 2011, 366 patients were treated for acute cholecystitis. Of these, 59 had common bile duct stones (CBDS) and 307 did not. Patients in both groups were further subdivided into two groups: a before guidelines group (BGG; n=153) and an after guideline group (AGG; n=154). Among the patients without CBDS, early cholecystectomy was more common in the AGG group (n=53) than in the BGG group. Furthermore, the length of hospital stay was four days shorter in the AGG group than in the BGG group (n=23). Among the patients with CBDS, the timing of cholecystectomy after endoscopic retrograde cholangiography was seven days earlier in the AGG group than in the BGG group. Even in a rural area of Japan, early cholecystectomy appears safe and can decrease the length of hospital stay.
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October 2013

Synthesis and fluorescence properties of pyrimidine mono- and bisboron complexes.

J Org Chem 2013 Jul 5;78(14):7058-67. Epub 2013 Jul 5.

Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan.

Novel fluorescent mono- and bisboron complexes based on pyrimidine bearing β-iminoenolate ligands were synthesized, and their fluorescence properties were investigated. The nonsubstituted and trifluoromethyl-substituted monoboron complexes showed higher fluorescence quantum yield in solid state than in solution. The dimethylamino derivative of the monoboron complex exhibited positive solvatochromism in the fluorescence spectra. The bisboron complex showed significantly higher molar absorption coefficient and red-shifted maximum absorption and maximum fluorescence wavelengths than the corresponding monoboron complex.
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http://dx.doi.org/10.1021/jo400879gDOI Listing
July 2013

Synthesis and fluorescence properties of thiazole-boron complexes bearing a β-ketoiminate ligand.

Org Lett 2012 Sep 28;14(17):4682-5. Epub 2012 Aug 28.

Department of Materials Science and Technology, Faculty of Engineering, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan.

Novel fluorescent dyes, thiazole-boron complexes bearing β-ketoiminate ligands, have been synthesized, and their fluorescence properties were investigated. The BF(2) complexes showed a pronounced aggregation-induced emission enhancement effect because of the restriction of C-Ph intramolecular rotation. The BPh(2) complexes showed higher fluorescence quantum yields than the corresponding BF(2) complexes, both in solution and in the solid state.
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http://dx.doi.org/10.1021/ol302179rDOI Listing
September 2012

Design of NIR-absorbing simple asymmetric squaraine dyes carrying indoline moieties for use in dye-sensitized solar cells with Pt-free electrodes.

Org Lett 2012 Mar 9;14(5):1246-9. Epub 2012 Feb 9.

Department of Materials Science and Technology Faculty of Engineering, Gifu University, 1-1 Yanagido, Gifu, Japan.

Novel near-infrared (NIR)-sensitizing (up to 800 nm) simple asymmetric squaraine dyes (Sq 31 and Sq 33) carrying indoline moieties that did not require the introduction of any linker groups were developed. DSSCs fabricated with Sq 33 exhibited remarkable characteristics in the long-wavelength visible and NIR region (up to 800 nm), such as a conversion efficiency of 3.75% (AM 1.5G) with an incident photon-to-current conversion efficiency of 63% (650 nm), a short-circuit photocurrent density of 13.64 mA, an open-circuit photovoltage of 0.48, and a fill factor of 0.57.
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http://dx.doi.org/10.1021/ol300054aDOI Listing
March 2012

Synthesis and fluorescence properties of novel pyrazine-boron complexes bearing a β-iminoketone ligand.

Org Lett 2011 Dec 16;13(24):6544-7. Epub 2011 Nov 16.

Department of Materials Science and Technology, Faculty of Engineering, Gifu University, Yanagido, Gifu 501-1193, Japan.

A novel fluorescence dye based on pyrazine-boron complexes bearing a β-iminoketone ligand has been synthesized by using a simple two-step reaction. Synthesized complexes exhibited fluorescence in solution (F(max): 472-604 nm) and in the solid state (F(max): 496-624 nm). These complexes showed a larger Stokes shift (3690-4900 cm(-1)) than well-known boron dipyrromethene dyes (400-600 cm(-1), in most cases).
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http://dx.doi.org/10.1021/ol202819wDOI Listing
December 2011

[A case of advanced gastric cancer showing a complete histological response after S-1/CDDP neoadjuvant chemotherapy].

Gan To Kagaku Ryoho 2011 Aug;38(8):1329-32

Dept. of Surgery, Mihara Red Cross Hospital.

We experienced a case of advanced gastric cancer treated by curative operation after neoadjuvant chemotherapy with S-1/ CDDP. Gastric endoscopy was carried out on a 76-year-old man with epigastric discomfort and revealed a type 1 lesion in his stomach. Papillary adenocarcinoma was pathologically shown by endoscopic biopsy. The patient was initially treated by two courses of neoadjuvant chemotherapy with S-1/CDDP due to the large lymph node metastases around the lesser curvature of the stomach and celiac axis. Completion of chemotherapy resulted in a marked shrinkage of the primary lesion and a reduction of lymph node metastases. Later, total gastrectomy, splenectomy and D2 lymph node dissection were performed. Histopathological examination revealed no cancer cells in either the primary lesion of the stomach or dissected lymph nodes, confirming a pathologically complete response.
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August 2011

Organocatalytic asymmetric direct aldol reactions of trifluoroacetaldehyde ethyl hemiacetal with aromatic methyl ketones.

J Org Chem 2011 May 17;76(9):3545-50. Epub 2011 Mar 17.

Department of Materials Science and Technology, Faculty of Engineering, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan.

The organocatalytic asymmetric direct aldol reaction of trifluoroacetaldehyde ethyl hemiacetal with aromatic methyl ketones in the presence of a catalytic amount of (S)-5-(pyrrolidin-2-yl)-1H-tetrazole in dichloroethane at 40 °C proceeds smoothly to produce (R)-4,4,4-trifluoro-1-aryl-3-hydroxy-1-butanones in high yields with up to 90% ee.
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http://dx.doi.org/10.1021/jo200020zDOI Listing
May 2011

Reversal of diastereoselectivity in reactions of the trifluoroacetaldehyde ethyl hemiacetal with enamines and imines: metal-free, complementary anti- and syn-selective synthesis of 4,4,4-trifluoro-1-aryl-3-hydroxy-2-methyl-1-butanones.

J Org Chem 2011 Jan 3;76(1):285-8. Epub 2010 Dec 3.

Department of Materials Science and Technology, Faculty of Engineering, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan.

A complete reversal of diastereoselectivity was observed for reactions of the trifluoroacetaldehyde ethyl hemiacetal with enamines and imines, derived from propiophenones, that produce 4,4,4-trifluoro-1-aryl-3-hydroxy-2-methyl-1-butanones. This process serves as the first reliable, metal-free, complementary anti- and syn-selective method to prepare 4,4,4-trifluoro-1-aryl-3-hydroxy-2-methyl-1-butanones.
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http://dx.doi.org/10.1021/jo101733jDOI Listing
January 2011

Establishment of an immortalized porcine liver cell line JSNK-1 with retroviral transduction of SV40T.

Cell Transplant 2010 ;19(6):849-56

Department of Gastroenterological Surgery, Okayama University Graduate School of Medicine and Dentistry, Okayama, Japan.

Maintenance of freshly isolated porcine liver cells in vitro is limited for a short period of time. Therefore, establishment of easy handling cell lines is extremely important for in vitro study for liver cells and their possible utilization for cell differentiation and growth of stem cells. Porcine liver cells were transduced with a retroviral vector SSR#69 expressing SV40T, one of SSR#69-immortalized porcine liver cell lines, JSNK-1, was established and characterized. Morphology of JSNK-1 cells was spindle shaped. When the cells became confluent, JSNK-1 cells revealed hills-and-valleys pattern. In the presence of vitamin A, JSNK-1 cells showed big droplets inside the cytoplasm, which were positive with PAS staining. JSNK-1 cells showed the gene expression of collagen type 1α1, collagen type 1α2, FLT-1, β-actin, and SV40T. Immunostaining study revealed that JSNK-1 cells produced collagen, vimentin, and α-smooth muscle actin. JSNK-1 cells possessed the characteristics of the liver stellate cells. JSNK-1 cells produced hepatocyte growth factor (HGF) in a time-dependent manner. When cocultured with iPS cells towards the hepatic differentiation, JSNK-1 cells facilitated their hepatic differentiation in terms of albumin production. In conclusion, JSNK-1 cells would be valuable in the study of liver stellate cell pathophysiology and contribute to the optimization of hepatic differentiation of iPS cells.
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http://dx.doi.org/10.3727/096368910X508979DOI Listing
January 2011

Hepatic differentiation of mouse iPS cells in vitro.

Cell Transplant 2010 ;19(6):841-7

Department of Gastroenterology and Hepatology, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, Japan.

Induced pluripotent stem (iPS) cells are pluripotent and are able to unlimitedly proliferate in vitro. This technical breakthrough in creating iPS cells from somatic cells has noteworthy implications for overcoming the immunological rejection and the ethical issues associated with the derivation of embryonic stem cells from embryos. In the current work, we present an efficient hepatic differentiation of mouse iPS cells in vitro. iPS cells were cultured free floating to induce the formation of embryoid bodies (EB) for 5 days. EB were transferred to a gelatin-coated plate and treated with 100 ng/ml activin A and 100 ng/ml basic fibroblast growth factor (bFGF) for 3 days to induce definitive endoderm. Cells were further cultured for 8 days with 100 ng/ml hepatocyte growth factor (HGF) to generate hepatocytes. Characterization was performed by RT-PCR assay. Functional analysis for albumin secretion and ammonia removal was also carried out. iPS cell-derived hepatocyte-like cells (iPS-Heps) were obtained at the end of the differentiation program. Expression levels of a gestational hepatocyte gene and lineage-specific hepatic genes intensified in iPS-Heps. The production of albumin increased in a time-dependent manner. iPS-Heps were capable of metabolizing ammonia. We present here instant hepatic differentiation of mouse iPS cells using combined 3-day treatments of activin A and bFGF with subsequent 8-day HGF. Our study will be an important step to generate hepatocytes from human iPS cells as a new source for liver-targeted cell therapies.
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http://dx.doi.org/10.3727/096368910X508960DOI Listing
January 2011

Comparative analysis of endoderm formation efficiency between mouse ES cells and iPS cells.

Cell Transplant 2010 ;19(6):831-9

Department of Gastroenterology and Hepatology, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, Japan.

Definitive endoderm (DE) derived from stem cells holds potential to differentiate into hepatocytes. Stem cell therapy using those cells has potential for a treatment of liver disease. To date, various ways of inducing hepatocytes from embryonic stem (ES) cells have been reported by researchers. However, it has not been proved enough that induced pluripotent stem (iPS) cells behave in the same manner as ES cells in endoderm differentiation. The purpose of this study was to establish an efficient method to induce DE from iPS cells, through comparatively analyzing the efficacy of endoderm formation from mouse ES cells. Furthermore, the efficiency of a serum-free medium in the differentiation into DE was investigated. Mouse ES cells and iPS cells were floated in culture medium for 2 or 5 days and embryoid bodies (EB) were formed. Subsequently, DE was induced with 100 ng/ml activin A and 100 ng/ml basic fibroblast growth factor (bFGF). RT-PCR and real-time PCR analyses were carried out at each step to determine the gene expression of EB markers. The difference in cellular proliferation between serum-containing and serum-free media was examined by an MTS assay in EB and DE induction. iPS cells showed the paralleled mRNA expression to ES cells in each step of differentiation into EB, but the levels of expression of Sox17 and Foxa2 were relatively higher in ES cell-derived DE, whereas Cxcr4 expression was higher in iPS cell-derived DE. The utilization of serum-free medium for iPS cells showed significantly favorable cellular proliferation during EB formation and subsequent DE induction. Forming EB for 5 days and subsequently DE induction with activin A and bFGF with serum-free medium was an appropriate protocol in iPS cells. This may represent an important step for generating hepatocytes from iPS cells for the development of cell therapy.
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http://dx.doi.org/10.3727/096368910X508951DOI Listing
January 2011