Mundlapati V Rao, Gautam Sanjeev, Sahoo Dipak Kumar, Ghosh Arindam, Biswal Himansu S
School of Chemical Sciences, National Institute of Science Education and Research (NISER) , PO-Bhimpur-Padanpur, Via-Jatni, District-Khurda, PIN-752050 Bhubaneswar, India.
Homi Bhabha National Institute , Training School Complex, Anushakti Nagar, Mumbai 400094, India.
J Phys Chem Lett. 2017 Sep 21;8(18):4573-4579. doi: 10.1021/acs.jpclett.7b01810. Epub 2017 Sep 12.
Thioamides are used as potential surrogates of amides to study the structure and dynamics of proteins and nucleic acids. However, incorporation of thioamides in biomolecules leads to changes in their structures and conformations mostly attributed to the strength of the amide-N-H···S═C hydrogen bond. In most cases, it is considered weak owing to the small electronegativity of sulfur, and in some cases, it is as strong as conventional H-bonds. Herein, adopting PDB structure analysis, NMR spectroscopy, and quantum chemistry calculations, we have shown that thioamides in a geometrical and structural constraint-free environment are capable of forming strong H-bonds like their amide counterparts. These studies also enabled us to determine the amide-N-H···S═C H-bond enthalpy (ΔH) very precisely. The estimated ΔH for the amide-N-H···S═C H-bond is ∼-30 kJ/mol, which suggests that the amide-N-H···S═C H-bond is a strong H-bond and merits its inclusion in computational force fields for biomolecular structure simulations to explore the role of amide-N-H···S═C H-bonds in nucleobase pairing and protein folding.
硫代酰胺被用作酰胺的潜在替代物，以研究蛋白质和核酸的结构与动力学。然而，将硫代酰胺掺入生物分子会导致其结构和构象发生变化，这主要归因于酰胺 - N - H···S═C氢键的强度。在大多数情况下，由于硫的电负性较小，该氢键被认为较弱，而在某些情况下，它与传统氢键一样强。在此，通过采用蛋白质数据银行（PDB）结构分析、核磁共振光谱和量子化学计算，我们表明，在无几何和结构限制的环境中，硫代酰胺能够像它们的酰胺对应物一样形成强氢键。这些研究还使我们能够非常精确地确定酰胺 - N - H···S═C氢键的焓变（ΔH）。估计的酰胺 - N - H···S═C氢键的ΔH约为 - 30 kJ/mol，这表明酰胺 - N - H···S═C氢键是一种强氢键，值得将其纳入生物分子结构模拟的计算力场中，以探索酰胺 - N - H···S═C氢键在核碱基配对和蛋白质折叠中的作用。
