title: Vibrational dynamics of thiocyanate and selenocyanate bound to horse heart myoglobin.
abstract: The structure and vibrational dynamics of SCN- and SeCN-bound myoglobin have been investigated using polarization-controlled IR pump-probe measurements and quantum chemistry calculations. The complexes are found to be in low and high spin states, with the dominant contribution from the latter. In addition, the Mb:SCN high spin complex exhibits a doublet feature in the thiocyanate stretch IR absorption spectra, indicating two distinct molecular conformations around the heme pocket. The binding mode of the high spin complexes was assigned to occur through the nitrogen atom, contrary to the binding through the sulfur atom that was observed in myoglobin derived from Aplysia Limacina. The vibrational energy relaxation process has been found to occur substantially faster than those of free SCN(-) and SeCN(-) ions and neutral SCN- and SeCN-derivatized molecules reported previously. This supports the N-bound configurations of MbNCS and MbNCSe, because S- and Se-bound configurations are expected to have significantly long lifetimes due to the insulation effect by heavy bridge atom like S and Se in such IR probes. Nonetheless, even though their lifetimes are much shorter than those of corresponding free ions in water, the vibrational lifetimes determined for MbNCS and MbNCSe are still fairly long compared to those of azide and cyanide myoglobin systems studied before. Thus, thiocyanate and selenocyanate can be good local probes of local electrostatic environment in the heme pocket. The globin dependence on binding mode and vibrational dynamics is also discussed.
authors: Department of Chemistry, Korea University, Seoul 136-713, South Korea.
authors: Michał
authors: M
authors: Maj
authors: Department of Chemistry, Korea University, Seoul 136-713, South Korea.
authors: Younjun
authors: Y
authors: Oh
authors: Department of Chemistry, Korea University, Seoul 136-713, South Korea.
authors: Kwanghee
authors: K
authors: Park
authors: Department of Chemistry, Korea University, Seoul 136-713, South Korea.
authors: Jooyong
authors: J
authors: Lee
authors: Department of Chemistry, Chung-Ang University, Seoul 156-756, SouthKorea.
authors: Kyung-Won
authors: KW
authors: Kwak
authors: Department of Chemistry, Korea University, Seoul 136-713, South Korea.
authors: Minhaeng
authors: M
authors: Cho
mesh_terms: D000818:Animals; D003485:Cyanates / Q000737:chemistry*; D006736:Horses; D008968:Molecular Conformation; D009206:Myocardium / Q000737:chemistry; D009211:Myoglobin / Q000737:chemistry*; D018036:Selenium Compounds / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013861:Thiocyanates / Q000737:chemistry*; D014732:Vibration; D014867:Water / Q000737:chemistry
chemical_list: D003485:Cyanates; D009211:Myoglobin; D018036:Selenium Compounds; D013861:Thiocyanates; D014867:Water; C053721:selenocyanic acid; C031760:thiocyanate