|Budget Amount *help
¥11,400,000 (Direct Cost : ¥11,400,000)
Fiscal Year 2000 : ¥600,000 (Direct Cost : ¥600,000)
Fiscal Year 1999 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1998 : ¥10,300,000 (Direct Cost : ¥10,300,000)
Seventeen cyclodextrin (hereafter abbreviated as CD) dimers were prepared through linking two cyclodextrins at the primary (C6) or secondary (C3, C2) hydroxyl sides by a disulfide bridge. The association constants between the dimers and methyl orange ranged from 1,500 to 606,000 and 583,000 M^<-1> of (α-CD)3SS6(β-CD) and (β-CD)6SS6(β-CD), respectively. Considering easiness of the preparation, the latter dimer was chosen as the material for constructing the super artificial enzymes. From 6^A,6^X-dideoxy-diiodo-β-CD (X=B, C, D), 6^A,6^X-dideoxy-6^A-mercapto-6^X-imidazolyl-β-CD (X=B, C, D, E, F, G) were regioselectively prepared and then oxidized to the corresponding diimidazolyl homo-dimers (diIm-dimers). Also, six monoimidazolyl dimers (monoIm-dimers) and monoimidazolyl-CD (Im-CD) were prepared. The enzymatic activities of the CD derivatives were evaluated in catalytic hydrolysis of a ester whose acid and alcohol parts were recognized by two CD of the dimers. MonoIm-dimers showed ability of molecular recognition (Km) about ten times larger than Im-CD and catalytic activity (k_c) nearly equal to that of Im-CD.DiIm-dimers and monoIm-dimers showed almost same values in the molecular recognition, while the formers demonstrated the values of k_c four times larger than the latter. Consequently, The 6^A, 6^F-diIm-dimer accelerated the hydrolysis 1000 times compared with the case of the uncatalyzed reaction. The artificial enzyme showed the properties of turn-over, bell-shaped pH profile of catalytic activity demonstrating the cooperation of two imidazolyl groups and so on.