title: Ultrafast excited-state charge-transfer dynamics in laccase type I copper site.
abstract: Femtosecond pump-probe spectroscopy was used to investigate the excited state dynamics of the T1 copper site of laccase from Pleurotus ostreatus, by exciting its 600 nm charge transfer band with a 15-fs pulse and probing over a broad range in the visible region. The decay of the pump-induced ground-state bleaching occurs in a single step and is modulated by clearly visible oscillations. Global analysis of the two-dimensional differential transmission map shows that the excited state exponentially decays with a time constant of 375 fs, thus featuring a decay rate slower than those occurring in quite all the investigated T1 copper site proteins. The ultrashort pump pulse induces a vibrational coherence in the protein, which is mainly assigned to ground state activity, as expected in a system with fast excited state decay. Vibrational features are discussed also in comparison with the traditional resonance Raman spectrum of the enzyme. The results indicate that both excited state dynamics and vibrational modes associated with the T1 Cu laccase charge transfer have main characteristics similar to those of all the T1 copper site-containing proteins. On the other hand, the differences observed for laccase from P. ostreatus further confirm the peculiar hypothesized trigonal T1 Cu site geometry.
authors.affiliation: Dipartimento di Scienze Ecologiche e Biologiche, Università della Tuscia, Largo dell'Università snc, I-01100 Viterbo, Italy. Electronic address: delfino@unitus.it.
authors.forename: Ines
authors.initials: I
authors.lastname: Delfino
authors.affiliation: IFN-CNR, Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy.
authors.forename: Daniele
authors.initials: D
authors.lastname: Viola
authors.affiliation: IFN-CNR, Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy.
authors.forename: Giulio
authors.initials: G
authors.lastname: Cerullo
authors.affiliation: Dipartimento di Medicina Sperimentale, Seconda Università di Napoli, Via Costantinopoli 16, I-80100 Napoli, Italy.
authors.forename: Maria
authors.initials: M
authors.lastname: Lepore
mesh_terms: D001665:Binding Sites; D003300:Copper / Q000737:chemistry*; D042845:Laccase / Q000737:chemistry*; D008958:Models, Molecular; D020076:Pleurotus / Q000737:chemistry / Q000201:enzymology*; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D003300:Copper; D042845:Laccase
keywords: Excited state dynamics; Impulsive Raman; Laccase; Pump–probe spectroscopy; Resonance Raman; T1 Cu site