| 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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| 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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