JPCL jz300207k Himansu Presentation


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JPCL jz300207k Himansu Presentation

  1. 1. The Strength of NH---S Hydrogen Bondsin Methionine Residues Revealed by Gas Phase IR/UV Spectroscopy Himansu S. Biswal*#†, Eric Gloaguen#, YohanLoquais#, Benjamin Tardivel# and Michel Mons*# # CEA, Laboratoire Francis Perrin, DSM/IRAMIS/SPAM, Bât 522, 91191 Gif-sur- Yvette, France # CNRS, Laboratoire Francis Perrin, URA 2453, 91191 Gif-sur-Yvette, France. † National Institute of Science Education and Research, Sachivalaya Marg, Bhubaneswar - 751 005, India. J. Phys. Chem. Lett. 2012, 3, 755 -759 1
  2. 2. MotivationStudies on intermolecular complexes suggest “sulfur” is a potential H-bond acceptor as “Oxygen”.1The intramolecular H-bonds frequently observed in proteins such asNamide-H···S hydrogen bonds linking the sulfur atom of methionine tobackbone NamideH groups has not yet been received much attention.Open QuestionHow strong is the Namide-H···S H-bond?Does it compete with other intramolecular H-bonds found in peptidesand proteins?How does it control the peptide structure and conformational space?1Biswal,H. S. et al. J. Phys. Chem. A, 2009, 113, 12763; ibid, 2010, 114, 5497; J. Chem. Phys.2011, 135, 134306. Proprietary and Confidential 2 American Chemical Society
  3. 3. Model Peptide and H-bond Pattern O H O N H H3C N N H H O S H3C Ac-Phe-Met-NH2 (FM) CH3 S O H O N HH3C N N H H O Ac-Met-Phe-NH2 (MF) Proprietary and Confidential 3 American Chemical Society
  4. 4. Experimental Strategy Pulsed valve • Laser desorption: hot species in the gas phase • Cooling in the supersonic expansion : Sample molecules are trapped in one or more (Peptide + graphite) conformations Vacuum chamber • Recognition of H-bond network by IR and UV spectroscopy Proprietary and Confidential 4 American Chemical Society
  5. 5. IR Spectra and Structure Assignment Proprietary and Confidential 5 American Chemical Society
  6. 6. Evidence of strong NH---S H-Bonds The „sulfur‟ atom of Methionine forms both intra and inter-residue N-H---S H-bond.intra-residue It is observed from Protein Data Bank 24% Methionine residues displays such local folding pattern. inter-residue Stabilization Energy = 10 kJ/mol Proprietary and Confidential 6 American Chemical Society
  7. 7. Comparison with Protein StructuresProtein with-Met - Phe – Sequence … comparable with isolated structure Ramachandran Angles Proprietary and Confidential 7 American Chemical Society
  8. 8. Conclusions The sulfur atom of methionine is found to be an H-bond Authors acceptor as strong as the oxygen atom of backbone carbonyl groups, despite its less electronegativity (generally considered as a weaker H-bond acceptor). The close similarity of local folding of the model dipeptides and those of proteins suggest that the strong N-H•••S H-bonds acting in dipeptides also occur in Himansu S. Biswal Eric Gloaguen proteins. This observation also suggests that they take part in the local shaping of the protein chain, like the classical N-H•••O interactions, and illustrates the relevance of such gas phase data to biochemical issues. The concept of „Sulfur Center Hydrogen Bonds‟ (SCHBs) needs a proper attention while designing new generation force field for protein structure simulation. Michel Mons Acknowledgments This work was financially supported by the French National Research Agency (ANR) (Grant ANR-08-BLAN- 0158-01) and the “Triangle de la Physique” Foundation (Grant 2008-053T-SERPBIO). Yohan Loquais Benjamin TardivelProprietary and Confidential 8American Chemical Society