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Articles by T. Katayama
Total Records ( 3 ) for T. Katayama
  S. Alam , T. Suzuki and T. Katayama
  Syringylglycerol-8-O-4'-(sinapyl alcohol) ethers (SGSEs) are lignin substructure dimeric compounds or 8-O-4' neolignans. To investigate biosynthesis of the 8-O-4' neolignans, incubation of sinapyl alcohol (SA) with enzyme preparations of Eucommia ulmoides was performed and formation of optically active SGSEs was found. To clarify the stereochemical mechanism of the SGSE formation, absolute configuration of four stereoisomers, (+)-erythro, (–)-erythro, (+)-threo and (–)-threo isomers, of SGSEs that contain a chiral secondary benzyl alcohol were determined as (7R, 8S), (7S, 8R), (7S, 8S) and (7R, 8R), respectively, by Mosher’s method [1H NMR analysis of tri-(R)-(+)-α-methoxy-α-trifluoromethylphenylacetate (MTPA) of SGSEs] with our related empirical rules. Four stereoisomers of SGSEs were obtained by dehydrogenations of SA with FeCl3 followed by reversed phase HPLC and chiral HPLC.
  S. Falah , T. Suzuki and T. Katayama
  Chemical constituents of the bark of Swietenia macrophylla King (Meliaceae) was investigated not only to develop further bark utilization but also to understand the biochemical function of the bark in the forest environment. A new phenylpropanoid-substituted catechin, namely, swietemacrophyllanin [(2R*,3S*,7"R*)-catechin-8,7"-7,2"-epoxy-(methyl 4",5"-dihydroxyphenylpropanoate)] (1) was isolated from the bark of S. macrophylla together with two known compounds, catechin (2) and epicatechin (3). The structure of 1 was elucidated by spectroscopic data and by comparison of the NMR data with those of catiguanins A and B, phenylpropanoid-substituted epicatechins. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity of the isolated compounds indicated that all of the three compounds have strong activity compared with trolox as a reference. Swietemacrophyllanin (1) had the strongest activity with a 50% inhibitory concentration (IC50) value of 56 μg mL-1.
  H Torigoe , K Sasaki and T. Katayama

Due to instability of pyrimidine motif triplex nucleic acid under physiological pH and low magnesium ion concentration, stabilization of the triplex under the physiological condition is crucial in improving its therapeutic potential to artificially control gene expression in vivo. To this end, we investigated the thermodynamic and kinetic effects of morpholino (MOR) modification of triplex-forming oligonucleotide (TFO) on the triplex formation under the physiological condition. The thermodynamic analyses indicated that the MOR modification of TFO not only significantly increased the thermal stability of the triplex but also increased the binding constant for the triplex formation by nearly 2 orders of magnitude. The consideration of the observed thermodynamic parameters suggested that the increased rigidity of the MOR-modified TFO in the free state relative to the corresponding unmodified TFO may enable the significant increase in the binding constant. Kinetic data demonstrated that the observed increase in the binding constant resulted from the considerable increase in the association rate constant rather than the decrease in the dissociation rate constant. This information will be valuable for designing novel chemically modified TFO with higher binding affinity in the triplex formation under physiological conditions, leading to progress in therapeutic applications of the antigene strategy in vivo.

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