Critical Assessment of the Strength of Hydrogen Bonds between the Sulfur Atom of Methionine/Cysteine and Backbone Amides in Proteins.
Gas-phase vibrational spectroscopy, coupled cluster (CCSD(T)), and dispersion corrected density functional (B97-D3) methods are employed to characterize surprisingly strong sulfur center H-bonded (SCHB) complexes between cis and trans amide NH and S atom of methionine and cysteine side chain. The amide N-H···S H-bonds are compared with the representative classical σ- and π-type H-bonded complexes such as N-H···O, N-H···O═C and N-H···π H-bonds. With the spectroscopic, theoretical, and structural evidence, amide N-H···S H-bonds are found to be as strong as the classical σ-type H-bonds, despite the smaller electronegativity of sulfur in comparison to oxygen. The strength of backbone-amide N-H···S H-bonds in cysteine and methionine containing peptides and proteins are also investigated and found to be of similar magnitudes as those observed in the intermolecular model complexes studied in this work. All such SCHBs also confirm that the electronegativities of the acceptors are not the sole criteria to predict the H-bond strength.
†School of Chemical Sciences, National Institute of Science Education and Research, Institute of Physics Campus, Sachivalaya Marg, PO: Sainik School, Bhubaneswar 751 005, India.
V Rao
VR
Mundlapati
‡Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005, India.
Sanat
S
Ghosh
‡Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005, India.|§Chemical Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, United States.
Aditi
A
Bhattacherjee
†School of Chemical Sciences, National Institute of Science Education and Research, Institute of Physics Campus, Sachivalaya Marg, PO: Sainik School, Bhubaneswar 751 005, India.
Prince
P
Tiwari
†School of Chemical Sciences, National Institute of Science Education and Research, Institute of Physics Campus, Sachivalaya Marg, PO: Sainik School, Bhubaneswar 751 005, India.
Himansu S
HS
Biswal
D000577:Amides / Q000737:chemistry*; D003545:Cysteine / Q000737:chemistry*; D006860:Hydrogen Bonding; D008715:Methionine / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry; D011506:Proteins / Q000737:chemistry*; D013057:Spectrum Analysis; D013455:Sulfur / Q000737:chemistry*
D000577:Amides; D010455:Peptides; D011506:Proteins; D013455:Sulfur; D008715:Methionine; D003545:Cysteine
IR−UV double resonance; REMPI; SCHB; cysteine; hydrogen bond; methionine