title: Evidences for Cooperative Resonance-Assisted Hydrogen Bonds in Protein Secondary Structure Analogs.
abstract: Cooperative behaviors of the hydrogen bonding networks in proteins have been discovered for a long time. The structural origin of this cooperativity, however, is still under debate. Here we report a new investigation combining excess infrared spectroscopy and density functional theory calculation on peptide analogs, represented by N-methylformamide (NMF) and N-methylacetamide (NMA). Interestingly, addition of the strong hydrogen bond acceptor, dimethyl sulfoxide, to the pure analogs caused opposite effects, namely red- and blue-shift of the N-H stretching infrared absorption in NMF and NMA, respectively. The contradiction can be reconciled by the marked lowering of the energy levels of the self-associates between NMA molecules due to a cooperative effect of the hydrogen bonds. On the contrary, NMF molecules cannot form long-chain cooperative hydrogen bonds because they tend to form dimers. Even more interestingly, we found excellent linear relationships between changes on bond orders of N-H/N-C/C = O and the hydrogen bond energy gains upon the formation of hydrogen bonding multimers in NMA, suggesting strongly that the cooperativity originates from resonance-assisted hydrogen bonds. Our findings provide insights on the structures of proteins and may also shed lights on the rational design of novel molecular recognition systems.
authors.affiliation: Key Laboratory of Bioorganic Phosphorous Chemistry and Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University, Beijing 100084, P. R. China.|School of Chemistry and Chemical Engineering, Qingdao University, Qingdao 266071, P. R. China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Key Laboratory of Bioorganic Phosphorous Chemistry and Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University, Beijing 100084, P. R. China.
authors.forename: Geng
authors.initials: G
authors.lastname: Deng
authors.affiliation: Key Laboratory of Bioorganic Phosphorous Chemistry and Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University, Beijing 100084, P. R. China.
authors.forename: Yan-Zhen
authors.initials: YZ
authors.lastname: Zheng
authors.affiliation: Key Laboratory of Bioorganic Phosphorous Chemistry and Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University, Beijing 100084, P. R. China.
authors.forename: Jing
authors.initials: J
authors.lastname: Xu
authors.affiliation: Key Laboratory of Bioorganic Phosphorous Chemistry and Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University, Beijing 100084, P. R. China.
authors.forename: Hamad
authors.initials: H
authors.lastname: Ashraf
authors.affiliation: Key Laboratory of Bioorganic Phosphorous Chemistry and Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University, Beijing 100084, P. R. China.
authors.forename: Zhi-Wu
authors.initials: ZW
authors.lastname: Yu
mesh_terms: D019295:Computational Biology; D006860:Hydrogen Bonding; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry*; D013055:Spectrophotometry, Infrared
chemical_list: D011506:Proteins