Slipping of a histidine improved the peroxidase activity of a de novo designed polypeptide packing an iron porphyrin

Hemin-block copolymer micelle as an artificial peroxidase and its applications in chromogenic detection and biocatalysis

Following an inspiration from the fine structure of natural peroxidases, such as horseradish peroxidase (HRP), an artificial peroxidase was constructed through the self-assembly of diblock copolymers and hemin, which formed a functional micelle with peroxidase-like activity. The pyridine moiety in block copolymer poly(ethylene glycol)-block-poly(4-vinylpyridine) (PEG-b-P4VP) can coordinate with hemin, and thus hemin is present in a five-coordinate complex with an open site for binding substrates, which mimics the microenvironment of heme in natural peroxidases. The amphiphilic core-shell structure of the micelle and the coordination interaction of the polymer to the hemin inhibit the formation of hemin μ-oxo dimers, and thereby enhance the stability of hemin in the water phase. Hemin-micelles exhibited excellent catalytic performance in the oxidation of phenolic and azo compounds by H2O2. In comparison with natural peroxidases, hemin-micelles have higher catalytic activity and better stability over wide temperature and pH ranges. Hemin-micelles can be used as a detection system for H2O2 with chromogenic substrates, and they anticipate the possibility of constructing new biocatalysts tailored to specific functions.

Synthesis and the electron transfer reaction of (metallo)-porphyrin linked with a fullerene through an (L)-lysine spacer

A novel visible-light induced electron transfer system composed of the free-base or Zn porphyrin, C60 molecule, and an (L)-lysine was synthesized and characterized. The porphyrin and C60 were covalently linked by the amide bonds through a relatively long and flexible spacer, (L)-lysine. The 1H NMR spectrum of the Zn porphyrin/(L)-lysine/ C60 conjugate (3Zn) suggested that C60 caused the slow molecular motion of this molecule. The steady-state absorption and the emission spectra of 3Zn revealed the intramolecular excited-state electron transfer from the Zn porphyrin moiety to the C60 moiety. The fluorescent lifetime measurement of the excited-state Zn porphyrin in 3Zn indicated the quenching by C60 . The intermolecular electron transfer from the excited-state zinc porphyrin to the viologen derivative in the solution was examined. The Zn porphyrin/(L)-lysine/ C60 conjugate and the free-base porphyrin/(L)-lysine/ C60 conjugate were more effective catalysts than the tetraphenylporphyrin Zn complex, suggesting the intermediacy of the charge separation state, ZnP·+-C60·- .