Relationship between protein structural fluctuations and rebinding dynamics in ferric haem nitrosyls

Neil T. Hunt, Gregory M. Greetham, Michael Towrie, Anthony W. Parker, Nicholas P. Tucker

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18 Citations (Scopus)


The interaction of nitric oxide (NO) with haem proteins is widespread in biology. In the current paper, we present the first ultrafast 2D-IR (two-dimensional infrared) spectroscopic analysis of haem nitrosylation, which has been combined with time-resolved IR pump probe studies to investigate the relationship between equilibrium vibrational dynamics of the haem environment and ligand rebinding behaviour following photolysis of NO from the Fe(III)-NO site. Studies of two haem proteins, Mb (myoglobin) and Cc (cytochrome c), which play different physiological roles, reveal marked contrasts in the ultrafast fluctuations of the protein pockets containing the haem, showing that the Mb pocket is somewhat more flexible than that of Cc. This correlates strongly with slower observed photolysis rebinding kinetics of Mb NO compared with Cc NO, and indicates a direct link between ultrafast fluctuations and biological functionality. Furthermore, this indicates the validity of linear response theories in relation to protein ligand binding. Finally, 2D-IR shows that Cc NO displays two distinct structural sub-sites at room temperature that do not exchange on the timescales accessible via the NO vibrational lifetime.

Original languageEnglish
Pages (from-to)459-468
Number of pages10
JournalBiochemical Journal
Early online date11 Nov 2010
Publication statusPublished - 1 Feb 2011


  • biophysics
  • haem protein
  • two-dimensional infrared (2D-IR) spectroscopy
  • ultrafast spectroscopy
  • vibrational echo spectroscopy
  • nitric-oxide binding
  • femtosecond mid-IR
  • Iinfrared spectroscopy
  • molecular dynamics
  • solvation dynamics
  • cytochrome-C
  • 3-Dimentional structure
  • high resolution
  • ligand-binding


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