Vibrational assignments of six-coordinate ferrous heme nitrosyls: new insight from nuclear resonance vibrational spectroscopy.
This Communication addresses a long-standing problem: the exact vibrational assignments of the low-energy modes of the Fe-N-O subunit in six-coordinate ferrous heme nitrosyl model complexes. This problem is addressed using nuclear resonance vibrational spectroscopy (NRVS) coupled to (15)N(18)O isotope labeling and detailed simulations of the obtained data. Two isotope-sensitive features are identified at 437 and 563 cm(-1). Normal coordinate analysis shows that the 437 cm(-1) mode corresponds to the Fe-NO stretch, whereas the 563 cm(-1) band is identified with the Fe-N-O bend. The relative NRVS intensities of these features determine the degree of vibrational mixing between the stretch and the bend. The implications of these results are discussed with respect to the trans effect of imidazole on the bound NO. In addition, a comparison to myoglobin-NO (Mb-NO) is made to determine the effect of the Mb active site pocket on the bound NO.
Paulat
Florian
F
Department of Chemistry, The University of Michigan, 930 N. University, Ann Arbor, Michigan 48109-1055, USA.
Berto
Timothy C
TC
DeBeer George
Serena
S
Goodrich
Lauren
L
Praneeth
V K K
VK
Sulok
Corinne D
CD
Lehnert
Nicolai
N
D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D006418:Heme / Q000737:chemistry*; D007700:Kinetics; D008958:Models, Molecular; D008968:Molecular Conformation; D009587:Nitrogen Isotopes; D009589:Nitrogen Oxides / Q000737:chemistry*; D010103:Oxygen Isotopes; D013057:Spectrum Analysis; D013816:Thermodynamics; D014732:Vibration
D009587:Nitrogen Isotopes; D009589:Nitrogen Oxides; D010103:Oxygen Isotopes; D006418:Heme