Strength of a bifurcated H bond
| Autor: | Esther S. Feldblum, Isaiah T. Arkin |
|---|---|
| Rok vydání: | 2014 |
| Předmět: |
Carbon Isotopes
Multidisciplinary Hydrogen bond Chemistry Macromolecular Substances Inorganic chemistry Hydrogen Bonding Oxygen Isotopes Biological Sciences Acceptor Crystallography chemistry.chemical_compound Protein structure Models Chemical Amide Spectroscopy Fourier Transform Infrared Density functional theory Fourier transform infrared spectroscopy Amino Acids Conformational isomerism Macromolecule |
| Zdroj: | Proceedings of the National Academy of Sciences |
| ISSN: | 1091-6490 |
| Popis: | Macromolecules are characterized by their particular arrangement of H bonds. Many of these interactions involve a single donor and acceptor pair, such as the regular H-bonding pattern between carbonyl oxygens and amide H(+)s four residues apart in α-helices. The H-bonding potential of some acceptors, however, leads to the phenomenon of overcoordination between two donors and one acceptor. Herein, using isotope-edited Fourier transform infrared measurements and density functional theory (DFT) calculations, we measured the strength of such bifurcated H bonds in a transmembrane α-helix. Frequency shifts of the (13)C=(18)O amide I mode were used as a reporter of the strength of the bifurcated H bond from a thiol and hydroxyl H(+) at residue i + 4. DFT calculations yielded very similar frequency shifts and an energy of -2.6 and -3.4 kcal/mol for the thiol and hydroxyl bifurcated H bonds, respectively. The strength of the intrahelical bifurcated H bond is consistent with its prevalence in hydrophobic environments and is shown to significantly impact side-chain rotamer distribution. |
| Databáze: | OpenAIRE |
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