2004 Fiscal Year Final Research Report Summary
Study on Chiral Recognition of Peptides by Water-Soluble Zinc-Porphyrin Complexes
| Project/Area Number |
15550154
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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 |
Chemistry related to living body
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| Research Institution | Hokuriku University |
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Principal Investigator |
IMAI Hiroyasu Hokuriku Univ., Dep.of Pharm.Sci, Assistant Prof., 薬学部, 講師 (60102761)
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| Project Period (FY) |
2003 – 2004
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| Keywords | Water-soluble zinc porphyrin / Chiral recognition / Receptor for amino acids / Multiple non-covalent interaction / ΔH-ΔS compensation effect |
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| Research Abstract |
Two kinds of water-soluble porphyrinatozinc complexes as receptors for amino acids and peptides were designed and synthesized as the racemic mixture. The complexes were optically separated into the enantiomers on a chiral HPLC column. The association constants K of the each enantiomer with amino acids and peptides in basic aqueous conditions were estimated spectrophotometrically.
The two porphyrin complexes with C_2 symmetry contain a quaternary ammonium group and a phenyl or tertiary butyl group near the central zinc ion. It was demonstrated that both of the complexes show chiral recognition for optically active amino acids and dipeptides (amino carboxylates in those experimental conditions) with a maximum value of 3 to 5 in K ratio for the two enantiomers. From the experimental results obtained, the chiral recognition was reasonably explained in terms of the triple cooperation of the following interactions : (1) Coordination of the amino group of the amino carboxylates to the central zinc, (2) Coulomb interaction between tie carboxylato anion and the ammonium cation of the porphyrins, and (3) Steric repulsion between the amino-acid residue and the phenyl or the tertiary butyl group of the porphyrins.
The ΔH-ΔS compensation effects were discussed based on the thermodynamic data estimated from temperature dependence of K. The results obtained were contrast to that reported for a zinc porphyrin receptor in an organic solvent, but were similar to those reported for cyclodextrins and for crown ethers in aqueous solution, suggesting that hydration-dehydration phenomena significantly affect the association of the zinc porphyrins in this work.
For the chiral recognition, the contribution from entropy was found to be little, suggesting that hydration-dehydration does not act as a chiral-recognition factor.
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