| Project/Area Number |
02403004
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| Research Category |
Grant-in-Aid for General Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
物理化学一般
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| Research Institution | Kyushu University |
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Principal Investigator |
MAEDA Hiroshi Kyushu University, Facultly of Science, Professor, 理学部, 教授 (20022626)
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| Co-Investigator(Kenkyū-buntansha) |
SASAKI Shigeo Kyushu University, Facultly of Science, Research Associate, 理学部, 助手 (30225867)
KAIBARA Kozue Kyushu University, Facultly of Science, Research Associate, 理学部, 助手 (90080564)
NAKAHARA Tatsuo Kyushu University, Facultly of Science, Research Associate, 理学部, 助手 (20037211)
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| Project Period (FY) |
1990 – 1993
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| Project Status |
Completed (Fiscal Year 1993)
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| Budget Amount *help |
¥24,000,000 (Direct Cost: ¥24,000,000)
Fiscal Year 1993: ¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1992: ¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1991: ¥4,000,000 (Direct Cost: ¥4,000,000)
Fiscal Year 1990: ¥16,000,000 (Direct Cost: ¥16,000,000)
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| Keywords | protein-surfactant interaction / irreversible aggregation of proteins / aggregation number of mixed micelles / stability of mixed micelles / dodecyldimethylamine oxide / oleic acid / swelling of ionic gels / Flory exponent of chains in gels / 混合ミセル / 水素結合 / 光散乱 / 蛍光プローブ法 / チトクロームc / ポリアクリル酸ゲル / 疎水相互作用 / 球状蛋白質の安定性 / 変性蛋白質の不可逆会合 / 高分子イオンゲルの膨潤 / 単分散ポリペプチドの結晶化 / 両親媒性物質 / オイレン酸 / イオン性ゲル |
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| Research Abstract |
1. We have found, for the first time, that nonionic surfactants bind to unfolded proteins. The binding takes place in two steps ; a weak binding step followed by a cooperative one. A measure of the hydrophobicity of unfolded polypeptides is proposed in terms of the onset concentration of the cooperative binding step. A model for the irreversible aggregation of unfolded proteins is also proposed.
2. The aggregation numbers and the critical micelle concentrations (cmc) of dodecyldimethylamine oxide were determined as functions of the degree of ionization of micelle. The aggregation number and the cmc showed, respectively, the maximum and the minimum at a particular value of the degree of ionization of micelle about 0.5. The dependence suggests some attractrive interaction, most probably the hydrogen bond, between cationic/nonionic as well as between cationic species. An interesting result was obtained that the cmc of the cationic species was lower than that of nonionic species in 0.2 M MaCl. A thermodynamic approach is proposed to analyze ionic/nonionic mixed micelles. This theory extracts a new parameter in addition to that employed in the regular solution approach. It plays a significant role in controlling the cmc at low ionic fractions.
3. We have determined reversible titratin curves, for the first time, of heterogeneous systems of a fatty acid in aqueous media in the case of olic acid.
4. We have proposed a new theory to describe the swelling of ionic gels by (a) taking account the effect of charges on the chain configuration in terms of Flory exponent or electrostatic persistence length, (b) taking account the effect of the counterion condensation on the Donnan osmotic pressure, and (c) ignoring the contribution from the mixing free energy of segments with solvent. We have successfully analyzed the swelling behaviors of several ionic gels in terms of our theory.
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