1995 Fiscal Year Final Research Report Summary
Mechanism of Entropy Reduction during Molecular Recognition
| Project/Area Number |
06650980
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
有機工業化学
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
MIZUTANI Tadashi Kyoto University, Graduate School of Engineering, Associate Professor, 工学研究科, 助教授 (40229696)
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| Project Period (FY) |
1994 – 1995
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| Keywords | Molecular Recognition / Entropy / Motional Freedom |
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| Research Abstract |
Molecular recognition, especially multipoint molecular recognition, was studied from the viewpoint of entropy changes during the process. A selective host for aspartic acid dimethyl ester was synthesized by regioselective introduction of three recognition groups into a porphyrin framework. Reference host having no recognition groups were also prepared to evaluate the thermodynamic parameters owing to each recognition interaction. On the other hand, it has been demonstrated that functions necessary for biological processes can be quantitatively evaluated by converting it to entropy quantity. This leads to the optimized design of multi-point recognition host. For example, translational entropy is associated with the capture of guest from a solution of low concentration of it. Internal rotational entropy is associated with the selectivity of guest recognition with internal rotational freedom. We need to specify the motional freedom restricted upon recognition. And the entropy change associated with that motional freedom should be calculated. The calculation of internal rotational entropy is especially important, and we carried out the calculation for the internal rotational entropy of amino acid esters. Experimentally determined rotational entropy along a single bond, which is determined from an experiment of binding of dimethyl aspartate by a trifunctionalized porphyrin host was 5 to 7 cal/K/mol. Comparison of calculated entropy and experimentally determined entropy enable us to evaluate the solvation entropy. This result gives fundamental information on the solvent-related interactions such as hydrophobic interactions.
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