Review Papers (Misc) - KOUMOTO Kazuya
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Polysaccharide-polynucleotide complexes (IV): Antihydrolysis effect of the schizophyllan/poly(C) complex and the complex dissociation induced by amines
K Koumoto, T Kimura, K Sakurai, S Shinkai
BIOORGANIC CHEMISTRY 29 ( 3 ) 178 - 185 2001.6
Publisher：ACADEMIC PRESS INC
Polymer complexes formed by schizophyllan and poly(C) showed a unique antihydrolysis effect when poly(C) was subjected to hydrolysis under basic conditions. The complexation reduced the hydrolysis rate to 80% of the control (i.e., poly(C) itself). However, when we added oligoamines with the intention of catalyzing the hydrolysis, the oligoamines induced dissociation of the complex instead of acceleration of the hydrolysis. (C) 2001 Academic Press.
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TEM and SEM observations of super-structures constructed in organogel systems from a combination of boronic-acid-appended bola-amphiphiles with chiral diols
K Koumoto, T Yamashita, T Kimura, R Luboradzki, S Shinkai
NANOTECHNOLOGY 12 ( 1 ) 25 - 31 2001.3
Publisher：IOP PUBLISHING LTD
Two bola-amphiphilic alpha, omega -diboronic acids separated by a (CH(2))(11) or (CH(2))(12) group were synthesized. Complexation with chiral diols readily gave new amphiphiles end-capped with the chiral substituents. Some of these acted as good gelators of organic solvents. Transmission electron microscope and scanning electron microscope observations established that a variety of super-structures are created in the organogels, depending on the solvents and the structure of the chiral end-cap groups. In most cases, the fibrous aggregates, the network structure which is the driving-force for gelation, showed a helical higher-order structure reflecting the chirality of the end-cap groups. The results indicate that the combinatorial approach utilizing boronic acid functions and diol compounds is useful in creating a variety of new super-structures in the gel phase.
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A novel technique to specifically separate RNAs by Schizophyllan
Taro Kimira, Kazuya Koumoto, Masami Mizu, Ritsuko Kobayashi, Kazuo Sakurai, Seiji Shinkai
Nucleic Acids Res. Supplement 1 283 - 284 2001
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Application of schizophyllan as a novel gene carrier
Kazuo Sakurai, Taro Kimira, Kazuya Koumoto, Masami Mizu, Ritsuko Kobayashi, Seiji Shinkai
Nucleic Acids Res. Supplement 1 223 - 224 2001
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Thermally induced conformational-transition of polydeoxyadenosine in the complex with schizophyllan and the base-length dependence of its stability
M Mizu, T Kimura, K Koumoto, K Sakurai, S Shinkai
CHEMICAL COMMUNICATIONS ( 5 ) 429 - 430 2001
Publisher：ROYAL SOC CHEMISTRY
A single chain of schizophyllan, one of the beta -1,3-glucan family, can form a stoichiometric complex with poly(dA) and the poly(dA)'s conformation and the complex stability strongly depends on the base length.
DOI： 10.1039/b009943k
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Chemical modification of schizophyllan by introduction of a cationic charge into the side chain which enhances the thermal stability of schizophyllan–poly(C) complexes
Kazuya Koumoto, Taro Kimura, Masami Mizu, Kazuo Sakurai, Seiji Shinkai
Chemical Communications 1 ( 19 ) 1962 - 1963 2001
Combining oxidation with periodate and reductive amination, the amino group is introduced only in the side chain of schizophyllan and the product can bind to poly(C) with a higher dissociation temperature than that of the unmodified schizophyllan and poly(C) complex. © 2001 Royal Society of Chemistry.
DOI： 10.1039/b105609n
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Polysaccharide-polynucleotide complexes (III): A novel interaction between the beta-1,3-glucan family and the single-stranded RNA poly(C)
T Kimura, K Koumoto, K Sakurai, S Shinkai
CHEMISTRY LETTERS ( 11 ) 1242 - 1243 2000.11
Publisher：CHEMICAL SOC JAPAN
We measured circular dichroism spectra to examine the complex-formation capability of various kinds of polysaccharides with poly(C). The results show that schizophyllan and lentinan can interact with poly(C), on the other hand, amylose, pullulan, dextran, and curdlan cannot. This difference clearly indicates that the water soluble beta -1,3-glucan can bind with polynucleotides. The molecular weight dependence of the complex formation has established that at least 30 glucose sequence length is necessary to incorporate the most bases into the complex.
DOI： 10.1246/cl.2000.1242
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Colorimetric sugar sensing method useful in "neutral" aqueous media
K Koumoto, S Shinkai
CHEMISTRY LETTERS ( 8 ) 856 - 857 2000.8
Publisher：CHEMICAL SOC JAPAN
Azobenzene derivatives bearing one or two aminomethylphenylboronic acid groups were synthesized: they were confirmed to be useful for practical colorimetric saccharide sensing in "neutral" aqueous media.
DOI： 10.1246/cl.2000.856
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The first example of positive allosterism in an aqueous saccharide-binding system designed on a Ce(IV) bis(porphyrinate) double decker scaffold
A Sugasaki, M Ikeda, M Takeuchi, K Koumoto, S Shinkai
TETRAHEDRON 56 ( 27 ) 4717 - 4723 2000.6
Publisher：PERGAMON-ELSEVIER SCIENCE LTD
The first example of a positive, homotropic system in aqueous saccharide-binding has been achieved using a Ce(IV) bis(porphyrinate) double decker scaffold bearing two pairs of boronic acid groups (compound 2). In this system, the binding of the first guest (1:2 saccharide/boronic acid complex) suppresses the rotational freedom of the two porphyrin planes, which facilitates the binding of the second guest. As a result, two pairs of boronic acid groups in 2 can autoacceleratively bind these guests and yield CD-active species. The analyses of CD intensity-guest concentration plots according to the Hill equation resulted in K=3.7x10(4) M-2 and n=2.0 for D-fructose and K=9.6x10(5) M-2 and n=1.6 for D-glucose. The present system which is in action even in aqueous media is widely applicable to allosteric control of drug release, catalytic reaction, information transduction, etc. of saccharide-containing guest molecules. (C) 2000 Elsevier Science Ltd. All rights reserved.
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Super-structures can be constructed in organogels from combination of a boronic-acid-appended bolaamphiphile with chiral diols
T Kimura, T Yamashita, K Koumoto, S Shinkai
TETRAHEDRON LETTERS 40 ( 36 ) 6631 - 6634 1999.9
Publisher：PERGAMON-ELSEVIER SCIENCE LTD
A bolaamphiphile bearing two boronic acid groups at the two ends was synthesized. Complexation with chiral diols readily afforded new amphiphiles end-capped with the chiral substituents. Some of them acted as gelators of organic solvents. TEM and SEM observations established that a variety of super-structures are created in the organogels, depending on the solvents and the structure of the end-cap groups. (C) 1999 Elsevier Science Ltd. All rights reserved.
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Design of a visualized sugar sensing system utilizing a boronic acid azopyridine interaction
K Koumoto, M Takeuchi, S Shinkai
SUPRAMOLECULAR CHEMISTRY 9 ( 3 ) 203 - + 1998
Publisher：TAYLOR & FRANCIS LTD
The boronic acid-amine (B-N) interaction was applied to the molecular design of a visualized sensing system for saccharides. 3-Nitrophenyl-boronic acid (3b) interacts with the pyridine nitrogen of 4-(4-dimethylaminophenyl-azo) pyridine (2) in methanol and changes its color from yellow to orange. Added saccharides form complexes with 3b and enhance the acidity of the boronic acid group. As a result, the B-N interaction becomes stronger and the intensified intramolecular charge-transfer band changes the solution color to red. By combined (1)H-NMR and absorption spectroscopic studies, four association constants governing the present ternary complex system have been determined. In case of D-fructose, the 3b.D-fructose complex can interact with 2240 times more strongly than 3b and the 2.3b complex can associate D-fructose 241 times more strongly than 3b. Clearly, the B-N interaction not only enables the colorimetric saccharide sensing but also enhances the association ability (i.e., sensitivity). Thus, the present paper offers a novel basic concept for molecular design of visualized saccharide sensing systems.
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Efficient glucoside extraction mediated by a boronic acid with an intramolecular quaternary ammonium ion
M Takeuchi, K Koumoto, M Goto, S Shinkai
TETRAHEDRON 52 ( 40 ) 12931 - 12940 1996.9
Publisher：PERGAMON-ELSEVIER SCIENCE LTD
To develop an efficient sugar extractant on the basis of the mechanistic view a phenylboronic acid bearing a trioctylammonium group at the ortho position (4) was synthesized. To avoid the complexity we employed a simple two-phase solvent-extraction system which corresponds to the first step in membrane transport, i.e., extraction from a donating aqueous phase to an organic liquid membrane phase. The extraction rates and equilibria were estimated using alpha-p-nitrophenyl-D-glucopyranoside as a sugar and 1,2-dichloroethane as an organic phase and compared with those of a 2-methylphenylboronic acid (5)/trioctylmethylammonium chloride (TOMAC) 1 : 1 binary system. The extraction rates for 4 were faster by 2.5 - 29 fold than those for 5 + TOMAC. The distribution coefficients were also enhanced by 5 - 8 fold. The results indicate that the intramolecular quaternary ammonium group is very effective to neutralize the anionic charge developed in the boron atom upon sugar-binding and create extractable zwitterionic sugar complexes. Copyright (C) 1996 Elsevier Science Ltd