title: Effects of Hofmeister ions on the α-helical structure of proteins.
abstract: The molecular conformation of proteins is sensitive to the nature of the aqueous environment. In particular, the presence of ions can stabilize or destabilize (denature) protein secondary structure. The underlying mechanisms of these actions are still not fully understood. Here, we combine circular dichroism (CD), single-molecule Förster resonance energy transfer, and atomistic computer simulations to elucidate salt-specific effects on the structure of three peptides with large α-helical propensity. CD indicates a complex ion-specific destabilization of the α-helix that can be rationalized by using a single salt-free computer simulation in combination with the recently introduced scheme of ion-partitioning between nonpolar and polar peptide surfaces. Simulations including salt provide a molecular underpinning of this partitioning concept. Furthermore, our single-molecule Förster resonance energy transfer measurements reveal highly compressed peptide conformations in molar concentrations of NaClO(4) in contrast to strong swelling in the presence of GdmCl. The compacted states observed in the presence of NaClO(4) originate from a tight ion-backbone network that leads to a highly heterogeneous secondary structure distribution and an overall lower α-helical content that would be estimated from CD. Thus, NaClO(4) denatures by inducing a molten globule-like structure that seems completely off-pathway between a fully folded helix and a coil state.
authors.affiliation: Cellular Dynamics and Cell Patterning, Max Planck Institute of Biochemistry, Martinsried, Germany. crevenna@biochem.mpg.de
authors.forename: Alvaro H
authors.initials: AH
authors.lastname: Crevenna
authors.forename: Nikolaus
authors.initials: N
authors.lastname: Naredi-Rainer
authors.forename: Don C
authors.initials: DC
authors.lastname: Lamb
authors.forename: Roland
authors.initials: R
authors.lastname: Wedlich-Söldner
authors.forename: Joachim
authors.initials: J
authors.lastname: Dzubiella
mesh_terms: D000595:Amino Acid Sequence; D031541:Fluorescence Resonance Energy Transfer; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry*; D010472:Perchlorates / Q000494:pharmacology; D011489:Protein Denaturation / Q000187:drug effects; D017433:Protein Structure, Secondary / Q000187:drug effects; D011506:Proteins / Q000737:chemistry*; D012492:Salts / Q000494:pharmacology; D017670:Sodium Compounds / Q000494:pharmacology
chemical_list: D010455:Peptides; D010472:Perchlorates; D011506:Proteins; D012492:Salts; D017670:Sodium Compounds; C031068:sodium perchlorate