Toshio Yanaki

Correlation between the antitumor activity of a polysaccharide schizophyllan and its triple-helical conformation in dilute aqueous solution

Eight samples of a polysaccharide schizophyllan ranging in weight-average molecular weight Mw (in water) from 5 x 10(3) to 1.3 x 10(5) were prepared and their antitumor activity (expressed in terms of the tumor inhibition ratio) against Sarcoma 180 ascites, intrinsic viscosities [eta], and gel-filtration chromatograms in aqueous solution were determined. The tumor inhibition ratio was essentially unity for samples with Mw higher than 9 x 10(4), but reduced to zero or even to a negative value when Mw was lower than 10(4). The [eta] data combined with the chromatographic data showed that above Mw approximately 9 x 10(4) the predominant species of schizophyllan in aqueous solution is the previously found rigid triple helix, whereas below Mw approximately 9 x 10(4) both triple helices and single chains coexist in the solution and the fraction of triple helices decreases monotonically to zero as Mw is decreased to 5 x 10(3). From these findings it was concluded that the antitumor potency of schizophyllan in water is related to the amount of triple helices relative to that of single chains.

Melting behaviour of a triple helical polysaccharide schizophyllan in aqueous solution

Abstract Two sonicated samples of schizophyllan in aqueous solution at temperatures from 20 to 160°C were investigated by viscometry. The temperature dependence of the viscosity coefficient η showed that schizophyllan in water undergoes an irreversible thermal transition at about 135°C. The values of (ln η r ) c ( ηr is the relative viscosity and c is the polymer concentration (w/v)) at 25°C determined after preheating aqueous schizophyllan indicated that the major conformations of schizophyllan in water at 120 and 150°C are triple helix and single random coil, respectively. Thus, it was concluded that the change in η at about 135°C with an increase in temperature is due to the melting of triple helices to single chains. Schizophyllan denatured to single chains at about 150°C did not restore the intact triple helix, but formed aggregates, when the solution was cooled to 25°C. It was also found that the aggregates form a gel when c is higher than a certain value.

Solubilization properties of N-substituted amphiphilic acrylamide copolymers

Amphiphilic copolymers of sodium 2-acrylamido-2-methylpropanesulfonate (AMPS) and dodecylmethacrylamide (DodMAAm) were synthesized. The ratio of the reduced viscosities of these copolymers in water and in 0.2 mol/L NaCl solution shows that these copolymers containing from 50 to 66 mol % of DodMAAm have a relatively small and constant hydrodynamic size. Viscometric and static light scattering measurements indicated that the copolymers shrinked and intermolecularly associated, forming interchain aggregates in water through hydrophobic interactions. These copolymers solubilize dl-α-tocopherol acetate, giving a transparent solution; but the solution became turbid in a month due to increasing intermolecular association. To suppress this excess intermolecular association, polymers with four different crosslinking ratios were synthesized. The polymer of a crosslinking ratio of 0.5 mol % showed a strong solubilization property, resulting in transparent solution with an improved stability. The fluorescence spectra of pyrene in the polymer solution proved that these copolymers could form strong hydrophobic domains, which solubilize a hydrophobic compound, in less than 30 w/w % ethanol solution. These copolymers could have an excellent function of sustained release of perfume as a novel function.

Differential scanning calorimetry studies on the mechanism of skin-softening effect of sodium acetylhyaluronate ☆

A novel humectant, sodium acetylhyaluronate (AcHA), was found to have an excellent skin-softening effect on the stratum corneum. To clarify the mechanism of the skin-softening effect, the hydration behavior of AcHA was investigated by using differential scanning calorimetry (DSC). The results suggested that the amount of adsorbed water of AcHA in powder form was equal to that of HA. However, the DSC results showed that the bound water content in the stratum corneum treated with AcHA was markedly greater than that of HA-treated stratum corneum. Apparently, AcHA could enhance the intrinsic water holding capacity of stratum corneum. These findings indicate that the excellent skin-softening effect of AcHA is due to the enhancement of the bound water content in the stratum corneum.

A High Performance Hair Treatment to Enhance Hair Strength Based on a Novel Self Cross-Linking Polymer

毛髪にハリコシを付与する方法として毛髪自体の育成を助ける生物学的アプローチと, 外部からある基剤を塗布して補強する物理的アプローチが考えられる。前者は軟毛の悩みを根本的に解決できる可能性があるが, 効果が得られるまでに長期間を要する, 効果に個人差がある, などの課題がある。一方, 後者は即効性はあるものの通常洗髪などにより効果が失われるなど, 持続性に乏しいため毎日の適用が必要となる。そこで即効性に優れ, しかもその効果が長期的に持続するハリコシ向上トリートメントの開発を目的として検討を行った。本基剤に求められる基本的条件として, 1. 優れた耐水性, 2. 1本1本の毛髪を独立してコートできること, の2点が挙げられる。そこで耐水性の付与を目的としてアルコキシシランの縮合反応によるネットワーク形成を利用し, 極性をコントロールすることで毛髪への付着性を向上させ, 1本ずつの毛髪を均一な皮膜でコーティング可能な基剤とした。さらに毛髪上に形成される皮膜の強度, 平滑性を検討し, 優れたハリコシ付与効果と良好な使用性を併せ持つへアトリートメントとすることに成功した。

Characterization of Ethyl Cellulose as W/O-Type Emulsifier and Application for Sunscreen

化粧品において皮膜剤として用いられてきたエチルセルロースについて, その両親媒性構造に着目し, 乳化剤としての可能性を検討した。種々の油分を用いて乳化を試みた結果, エチルセルロースが極性油をW/O乳化可能であることが見出された。蛍光ラベル化したエチルセルロースを用いた評価系の結果から, エチルセルロースは界面に吸着層を形成すると同時に連続相に構造体を形成することで, W/O型エマルションを安定化することが示唆された。このエチルセルロースを用いたW/O型エマルションは, イソステアリン酸とカルボキシメチルセルロースNaの添加によりさらに安定化し, 化粧品として要求されるレベルまで安定化できることがわかった。本基剤の特長は, 従来乳化が困難であった極性油を安定にW/O乳化できる点にあるため, サンスクリーン剤への応用を次に試みた。この結果, エチルセルロースは乳化剤として作用し, エマルションが調製されると同時に, 塗布後は皮膜剤として作用し, 高い耐水性を与えることが示された。