Relaxation Dynamics of Pseudomonas aeruginosa Re^I(C)O_3(α-diimine)(HisX)^+ (X=83, 107, 109, 124, 126)Cu-^(II) Azurins
Abstract
Photoinduced relaxation processes of five structurally characterized Pseudomonas aeruginosa Re^I(CO)_3(α-diimine)(HisX) (X = 83, 107, 109, 124, 126)Cu^(II) azurins have been investigated by time-resolved (ps−ns) IR spectroscopy and emission spectroscopy. Crystal structures reveal the presence of Re-azurin dimers and trimers that in two cases (X = 107, 124) involve van der Waals interactions between interdigitated diimine aromatic rings. Time-dependent emission anisotropy measurements confirm that the proteins aggregate in mM solutions (D2O, KPi buffer, pD = 7.1). Excited-state DFT calculations show that extensive charge redistribution in the ReI(CO)_3 → diimine ^3MLCT state occurs: excitation of this ^3MLCT state triggers several relaxation processes in Re-azurins whose kinetics strongly depend on the location of the metallolabel on the protein surface. Relaxation is manifested by dynamic blue shifts of excited-state ν(CO) IR bands that occur with triexponential kinetics: intramolecular vibrational redistribution together with vibrational and solvent relaxation give rise to subps, 2, and 8−20 ps components, while the ~10^2 ps kinetics are attributed to displacement (reorientation) of the Re^I(CO)_3(phen)(im) unit relative to the peptide chain, which optimizes Coulombic interactions of the Re^I excited-state electron density with solvated peptide groups. Evidence also suggests that additional segmental movements of Re-bearing β-strands occur without perturbing the reaction field or interactions with the peptide. Our work demonstrates that time-resolved IR spectroscopy and emission anisotropy of Re^I carbonyl−diimine complexes are powerful probes of molecular dynamics at or around the surfaces of proteins and protein−protein interfacial regions.
Additional Information
Copyright © 2009 American Chemical Society. Received April 10, 2009; Publication Date (Web): July 29, 2009. This work was supported by EPSRC (EP/E060544), STFC (CMSD43), COST D35, Ministry of Education of the Czech Republic (OC09043 and LC06063), NSF (CHE-0802907 and CHE-0749997), and NIH (DK019038). Supporting Information: Tables of experimentally determined orientation of the histidine imidazole ligand relative to the Re(CO)_3(phen) unit in the five proteins, DFT-calculated frontier Kohn−Sham orbitals and electronic transitions of Re(Etim) in two conformations, comparison of calculated and experimental ground- and excited-state ν(CO) IR wavenumbers of Re(Etim), and results of stretched-exponential fitting of the A′(1) ν(CO) band shift kinetics at different concentrations. Figures of DFT-calculated structures of Re(Etim) in several ground- and excited-state conformations and time traces of the peak energy of the A′(1) ν(CO) band of 107-dmp, 124-phen, and 126-phen measured at different concentrations. Full text of ref 33 (Gaussian 03 software) is provided. This material is available free of charge via the Internet at http://pubs.acs.org.Attached Files
Supplemental Material - Blancoja902744s_si_001.pdf
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Additional details
- Eprint ID
- 15805
- Resolver ID
- CaltechAUTHORS:20090911-153601363
- EP/E060544
- Engineering and Physical Sciences Research Council
- CMSD43
- Science and Technology Facilities Council
- COST D35
- Engineering and Physical Sciences Research Council
- OC09043
- Ministry of Education of the Czech Republic
- LC06063
- Ministry of Education of the Czech Republic
- CHE-0802907
- NSF
- CHE-0749997
- NSF
- DK019038
- NIH
- Created
-
2009-10-07Created from EPrint's datestamp field
- Updated
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2021-11-08Created from EPrint's last_modified field
- Caltech groups
- CCI Solar Fuels