Interaction Enthalpy of Side Chain and Backbone Amides in Polyglutamine Solution Monomers and Fibrils.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS(2018)
摘要
We determined an empirical correlation that relates the amide I vibrational band frequencies of the glutamine (Q) side chain to the strength of hydrogen bonding, van der Waals, and Lewis acid-base interactions of its primary amide carbonyl. We used this correlation to determine the Q side chain carbonyl interaction enthalpy (Delta H-int) in monomeric and amyloid-like fibril conformations of D(2)Q(10)K(2) (Q10). We independently verified these Delta H-int values through molecular dynamics simulations that showed excellent agreement with experiments. We found that side chain-side chain and side chain-peptide backbone interactions in fibrils and monomers are more enthalpically favorable than are Q side chain- water interactions. Q10 fibrils also showed a more favorable Delta H-int for side chain-side chain interactions compared to backbone-backbone interactions. This work experimentally demonstrates that interamide side chain interactions are important in the formation and stabilization of polyQ fibrils.
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