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Main Title: Low frequency dynamics of the nitrogenase MoFe protein via femtosecond pump probe spectroscopy
Subtitle: Observation of a candidate promoting vibration
Author(s): Maiuri, Margherita
Delfino, Ines
Cerullo, Giulio
Manzoni, Cristian
Pelmenschikov, Vladimir
Guo, Yisong
Wang, Hongxin
Gee, Leland B.
Dapper, Christie H.
Newton, William E.
Cramer, Stephen P.
Type: Article
Language Code: en
Abstract: We have used femtosecond pump-probe spectroscopy (FPPS) to study the FeMo-cofactor within the nitrogenase (N2ase) MoFe protein from Azotobacter vinelandii. A sub-20-fs visible laser pulse was used to pump the sample to an excited electronic state, and a second sub-10-fs pulse was used to probe changes in transmission as a function of probe wavelength and delay time. The excited protein relaxes to the ground state with a ~ 1.2 ps time constant. With the short laser pulse we coherently excited the vibrational modes associated with the FeMo-cofactor active site, which are then observed in the time domain. Superimposed on the relaxation dynamics, we distinguished a variety of oscillation frequencies with the strongest band peaks at ~ 84, 116, 189, and 226 cm− 1. Comparison with data from nuclear resonance vibrational spectroscopy (NRVS) shows that the latter pair of signals comes predominantly from the FeMo-cofactor. The frequencies obtained from the FPPS experiment were interpreted with normal mode calculations using both an empirical force field (EFF) and density functional theory (DFT). The FPPS data were also compared with the first reported resonance Raman (RR) spectrum of the N2ase MoFe protein. This approach allows us to outline and assign vibrational modes having relevance to the catalytic activity of N2ase. In particular, the 226 cm− 1 band is assigned as a potential ‘promoting vibration’ in the H-atom transfer (or proton-coupled electron transfer) processes that are an essential feature of N2ase catalysis. The results demonstrate that high-quality room-temperature solution data can be obtained on the MoFe protein by the FPPS technique and that these data provide added insight to the motions and possible operation of this protein and its catalytic prosthetic group.
Issue Date: 2015
Date Available: 7-May-2018
DDC Class: 540 Chemie und zugeordnete Wissenschaften
Subject(s): nitrogenase
nuclear resonance vibrational spectroscop
proton transfer
Sponsor/Funder: ERC/ERC-2011-AdG/291198/STRATUS
Journal Title: Journal of Inorganic Biochemistry
Publisher: Elsevier
Publisher Place: Amsterdam
Volume: 153
Publisher DOI: 10.1016/j.jinorgbio.2015.07.005
Page Start: 128
Page End: 135
ISSN: 0162-0134
Appears in Collections:FG Theoretische Chemie - Quantenchemie » Publications

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