1995 Fiscal Year Final Research Report Summary
Dynamics of molecular recognition
| Project/Area Number |
04101003
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| Research Category |
Grant-in-Aid for Specially Promoted Research
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| Allocation Type | Single-year Grants |
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
OGOSHI Hisanobu Kyoto University, Graduate School of Engineering, Professor, 工学研究科, 教授 (90026188)
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| Co-Investigator(Kenkyū-buntansha) |
SUZUKI Akihiro Nagaoka National College of Technology, Department of Materials Engineering, Ass, 物質工学科, 助手 (60179190)
MASUDA Hideki Nagoya Institute of Technology, Department of Applied Chemistry, Professor, 応用化学科, 助教授 (50209441)
AOYAGI Katsuhiro Fukushima National College of Technology, Department of Industrial Chemistry, As, 工業化学科, 助教授 (40150940)
HAYASHI Takashi Kyoto University, Graduate School of Engineering, Research Associate, 工学研究科, 助手 (20222226)
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| Project Period (FY) |
1992 – 1995
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| Keywords | Molecular Recognition / Porphyrin / Chiral Recognition / Electron Transfer / Thermodynamic Parameter / Conformation / Solvent Effects |
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| Research Abstract |
We have studied four topics to elucidate the dynamics of molecular recognition : (1) Conformational changes induced by molecular recognition, (2) Thermodynamic and spectroscopic studies of multi-point molecular recognition, (3) Electron transfer process regulated by molecular recognition, and (4) Fluoroporphyrins and reconstituted myoglobin.
1.Induced-fit binding of quinones to tetrahydroxyporphyrin results in the atropisomerization in the porphyrin. Also preorganization of flexible nucleobase receptor before binding a target guest was demonstrated by determining thermodynamic parameters of the binding. Porphyrin dimer formation following atropisomerization was also studied kinetically.
2.Circular dichroism was used to investigate the interaction mode of porphyrin-amino acid system. Two-point recognition lead to split-type induced CD,through electrostatic coupling between the chromophores. Novel chiral porphyrins were prepared, which show moderate to high enantioselective binding of amino acid esters. Receptors for tartaric acid, aspartic acid and sugars were also prepared. These receptors showed high regioselectivity for the guest. Enthalpy and entropy changes upon complexation were used to estimate conformational changes during complex formation.
3.Fast electron transfer from singlet state of porphyrin to quinone or viologens driven photochemically was realized by designing a binding site for quenchers. Electron transfer from zinc porphyrin in myoglobin to quinone which is attached by a peptide spacer occurred from a singlet state with a rate one order of magnitude slower than in dichloromethane.
4.Reconstitution of myoglobin by artificial hemes showed that interactions between heme and apoprotein can be split into contributions from non-polar interactions of 1,2,3,4-alkyl groups and polar interactions of 6,7-propionate groups. The polar interactions between propionate groups and protein was found to stabilize oxyheme.
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