title: Construction of a hybrid biocatalyst containing a covalently-linked terpyridine metal complex within a cavity of aponitrobindin.
abstract: A hybrid biocatalyst containing a metal terpyridine (tpy) complex within a rigid β-barrel protein nitrobindin (NB) is constructed. A tpy ligand with a maleimide group, N-[2-([2,2':6',2''-terpyridin]-4'-yloxy)ethyl]maleimide (1), was covalently linked to Cys96 inside the cavity of NB to prepare a conjugate NB-1. Binding of Cu(2+), Zn(2+), or Co(2+) ion to the tpy ligand in NB-1 was confirmed by UV-vis spectroscopy and ESI-TOF MS measurements. Cu(2+)-bound NB-1 is found to catalyze a Diels-Alder reaction between azachalcone and cyclopentadiene in 22% yield, which is higher than that of the Cu(2+)-tpy complex without the NB matrix. The results suggest that the hydrophobic cavity close to the copper active site within the NB scaffold supports the binding of the two substrates, dienophile and diene, to promote the reaction.
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Yamadaoka 2-1, Suita 565-0871, Japan.
authors.forename: Tomoki
authors.initials: T
authors.lastname: Himiyama
authors.affiliation: Institut für Anorganische Chemie, RWTH Aachen University, Landoltweg 1, Aachen 52056, Germany.
authors.forename: Daniel F
authors.initials: DF
authors.lastname: Sauer
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Yamadaoka 2-1, Suita 565-0871, Japan. Electronic address: onoda@chem.eng.osaka-u.ac.jp.
authors.forename: Akira
authors.initials: A
authors.lastname: Onoda
authors.affiliation: Institut für Anorganische Chemie, RWTH Aachen University, Landoltweg 1, Aachen 52056, Germany.
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Spaniol
authors.affiliation: Institut für Anorganische Chemie, RWTH Aachen University, Landoltweg 1, Aachen 52056, Germany. Electronic address: jun.okuda@ac.rwth-aachen.de.
authors.forename: Jun
authors.initials: J
authors.lastname: Okuda
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Yamadaoka 2-1, Suita 565-0871, Japan. Electronic address: thayashi@chem.eng.osaka-u.ac.jp.
authors.forename: Takashi
authors.initials: T
authors.lastname: Hayashi
mesh_terms: D002384:Catalysis; D003035:Cobalt / Q000737:chemistry; D056831:Coordination Complexes / Q000737:chemistry; D003300:Copper / Q000737:chemistry; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry*; D015032:Zinc / Q000737:chemistry
chemical_list: D056831:Coordination Complexes; D009942:Organometallic Compounds; D011725:Pyridines; D003035:Cobalt; D003300:Copper; D015032:Zinc; C023666:pyridine
keywords: Diels–Alder reaction; Hybrid biocatalyst; Metal terpyridine complex