| Project/Area Number |
11650924
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
高分子構造・物性(含繊維)
|
|---|
| Research Institution | TOKYO INSTITUTE OF TECHNOLOGY |
|---|
Principal Investigator |
FURUYA Hidemine Tokyo Institute of Technology, Department of Organic and Polymeric Materials, Associate Professor, 大学院・理工学研究科, 助教授 (90251652)
|
|---|
| Project Period (FY) |
1999 – 2000
|
| Project Status |
Completed (Fiscal Year 2000)
|
| Budget Amount *help |
¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 2000: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1999: ¥2,600,000 (Direct Cost: ¥2,600,000)
|
|---|
| Keywords | Polyaspartate / Helix-helix Transition / Helix-coil Transition / Conformation / NMR Measurement / CD Measurement |
|---|
| Research Abstract |
Poly (β-phenethyl L-aspartate)(PPLA) exhibits a transformation from right-handed to left-handedα-helix to in 1,1,2,2-tetrachloroethane with an increase in temperatures. The primary cause responsible for such a highly cooperative helix-helix transition was found to reside in a small free-energy difference in the conformational states of the side chain flanking the spiral backbone of the opposite handedness. The mechanism of the highly cooperative helix sense reversal has been investigated by using block copolymers which consist of β-phenethyl L-aspartate chain and perfectly rigid helical γ-benzyl L-glutamate chain. We have carried out ^1H-NMR and CD measurements to determine the screw sense of the block copolymers. The variation for triblock copolymer is similar to that of PBLG which exhibits no helix-helix transition. This result indicates that the helical sense of the PA chain does not transform. We found that the helix transition did not occur from the center of the PPLA chain, and that the helix-sense completely reversed from the N-terminus.
The mechanism of the helix-coil transition has been also investigated by using block copolymers which consist of poly(γ-benzyl L-glutamate)(PBLG) and poly (L-alanine)(PLA) chain. From the results, the transition temperature for diblock and triblock copolymers in dilute solution was found to be similar to that for PBLG.The helix-coil transition for PBLG in dilute solution can occur from anywhere in the helix chain. Phase behavior for the concentrated solution was observed by polarizing microscope. For triblock copolymer, the transition temperature from liquid crystal state to isotropic state coupled with the helix-coil transformation was obtained to become lower. In the concentrated solution, the helix-coil transition predominantly proceeds from the terminus of PBLG helix chain.
|
