| Project/Area Number |
10650875
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
高分子構造・物性(含繊維)
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| Research Institution | HOKKAIDO UNIVERSITY |
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Principal Investigator |
HIRAOKI Toshifumi Hokkaido Univ., Grad. School of Eng., Ass. Pro., 大学院・工学研究科, 助教授 (10125346)
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| Co-Investigator(Kenkyū-buntansha) |
TSUTSUMI Akihiro Hokkaido Univ., Grad. School of Eng., Pro., 大学院・工学研究科, 教授 (80000884)
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| Project Period (FY) |
1998 – 1999
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| Project Status |
Completed (Fiscal Year 1999)
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| Budget Amount *help |
¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 1999: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1998: ¥2,200,000 (Direct Cost: ¥2,200,000)
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| Keywords | helix-sense inversion / poly (β-n-propy L-aspartate) / right-handed α-hellx / p-phenylazobenzene / the side-chain conformation / photo-isomerization / ヘリックスセンス |
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| Research Abstract |
In order to clarify the mechanism of the helix-sense inversion of poly(β-n-propyl L-aspartate)(PnPLA), the conformational transition of PnPLA and its derivative with azobenzene group were investigated by means of NMR.
1) The right-handed α-helix (αィイD2RィエD2)of PnPLA can change thermoreversibly to the left-handed (αィイD2LィエD2) with increasing temperature from 30 to 70℃ in CDClィイD23ィエD2. The midpoint is 50℃, the transition free energy is 110 kJ/mol, and the exchange rate between both conformations is 5 /s at about 50℃. All the ィイD113ィエD1C signals of PnPLA can separate completely between the right- and left-helices, although only the NH and βィイD2sィエD2 proton resonances show the conformational dependence. These results indicate that the side-chain conformation of αィイD2RィエD2-helical PnPLA is different from that of αィイD2LィエD2-helix, as well as the main chain conformation. The αィイD2RィエD2-helix conformation of PnPLA changes to the left-handed, and subsequently to the random-coil with increasing the trifluoroacetic acid concentration. The coil conformation of PnPLA can change to the αィイD2LィエD2-helix with increasing the temperature, and the αィイD2RィエD2-helix is not detected in the high temperatures.
2) PnPLA containing 30% p-phenylazobenzene group in the side chain do not show the helix-sense inversion with the photo-isomerization of azobenzene group. The PnPLA containing more than 50% p-phenylazobenzene group is preparing for further experiments.
3) The internal rotational angle from the spin-spin coupling constant ィイD13ィエD1Jαβ is necessary to determine the side chain conformation. The monomer of L-asp-βィイD2RィエD2-d was successfully synthesized from the fumaric acid in DィイD22ィエD2O/NDィイD24ィエD2OD with the enzyme of L-aspartase to remove the contribution of the residual geminal ィイD12ィエD1Jββ in the signal of βィイD2sィエD2 proton. PnPLA-βィイD2RィエD2-d is preparing for further experiments.
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