Relaxation dynamics of Pseudomonas aeruginosa Re(I)(CO)3(alpha-diimine)(HisX)+ (X = 83, 107, 109, 124, 126)Cu(II) azurins.
Photoinduced relaxation processes of five structurally characterized Pseudomonas aeruginosa Re(I)(CO)(3)(alpha-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 (D(2)O, KP(i) buffer, pD = 7.1). Excited-state DFT calculations show that extensive charge redistribution in the Re(I)(CO)(3) --> diimine (3)MLCT state occurs: excitation of this (3)MLCT 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 nu(CO) IR bands that occur with triexponential kinetics: intramolecular vibrational redistribution together with vibrational and solvent relaxation give rise to subps, approximately 2, and 8-20 ps components, while the approximately 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 beta-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.
Blanco-Rodríguez
Ana María
AM
School of Biological and Chemical Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, United Kingdom.
Busby
Michael
M
Ronayne
Kate
K
Towrie
Michael
M
Grădinaru
Cristian
C
Sudhamsu
Jawahar
J
Sýkora
Jan
J
Hof
Martin
M
Zális
Stanislav
S
Di Bilio
Angel J
AJ
Crane
Brian R
BR
Gray
Harry B
HB
Vlcek
Antonín
A
D000042:Absorption; D016880:Anisotropy; D001400:Azurin / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D004579:Electron Transport; D004583:Electrons; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000378:metabolism*; D011487:Protein Conformation; D011550:Pseudomonas aeruginosa; D011789:Quantum Theory; D012211:Rhenium / Q000378:metabolism; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D013997:Time Factors
D009942:Organometallic Compounds; D001400:Azurin; D012211:Rhenium