title: Multipeptide-metalloporphyrin assembly on a dendrimer template and photoinduced electron transfer based on the dendrimer structure.
abstract: To construct an artificial photosynthetic system, peptide dendrimers [n-(X-HLY)PAMAMs: X = R, E; Y= L, F; n=4, 8, 16, 32 and 64 segments], in which amphiphilic alpha-helix peptides (X-HLY: R-HLL, E-HLL and R-HLF) were introduced at the end groups of polyamidoamine dendrimers (PAMAMs), were designed and synthesized. The peptide dendrimers 64-(X-HLY)PAMAMs are novel synthetic biopolymers with an enormous molecular weight, about 160 kDa, and with a regulated amino acid sequence and three-dimensional conformation. The peptide dendrimers bound Fe(III)- or Zn(II)-mesoporphyrin IX per two alpha-helices; this afforded a multimetalloporphyrin assembly similar to the natural light-harvesting antennae in photosynthetic bacteria. Circular dichroism studies and peroxidase activity measurements revealed that metalloporphyrins were coordinated to the peptide dendrimers in a regulated manner and packed more densely with the growth of the dendrimer generation. Fluorescence quenching and photoreduction studies with methylviologen demonstrated that the photoinduced electron-transfer function with the peptide dendrimer-multi-Zn-MP was accomplished more effectively as the dendrimer generation increased. Thus, the three-dimensional assembly of metalloporphyrins and peptides in the dendrimer was an effective module for light-harvesting antennae in an artificial photosynthetic system.
authors.affiliation: Department of Bioengineering, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Nagatsuta, Yokohama, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Sakamoto
authors.forename: A
authors.initials: A
authors.lastname: Ueno
authors.forename: H
authors.initials: H
authors.lastname: Mihara
mesh_terms: D000595:Amino Acid Sequence; D002851:Chromatography, High Pressure Liquid; D002942:Circular Dichroism; D004579:Electron Transport; D005290:Ferric Compounds / Q000737:chemistry; D006139:Guaiacol / Q000031:analogs & derivatives / Q000737:chemistry; D008665:Metalloporphyrins / Q000138:chemical synthesis* / Q000737:chemistry*; D008958:Models, Molecular; D008970:Molecular Weight; D010269:Paraquat / Q000737:chemistry; D010455:Peptides / Q000138:chemical synthesis* / Q000737:chemistry*; D009195:Peroxidase / Q000378:metabolism; D010777:Photochemistry / Q000379:methods; D013054:Spectrophotometry, Atomic; D013056:Spectrophotometry, Ultraviolet; D015032:Zinc / Q000737:chemistry
chemical_list: D005290:Ferric Compounds; D008665:Metalloporphyrins; D010455:Peptides; C430963:tetraguaiacol; D006139:Guaiacol; D009195:Peroxidase; D015032:Zinc; D010269:Paraquat