Reversal of the Hofmeister Series: Specific Ion Effects on Peptides

Paterová, Jana; Rembert, Kelvin B.; Heyda, Jan; Kurra, Yadagiri; Okur, Halil I.; Liu, Wenshe Ray; Hilty, Christian; Cremer, Paul S.; Jungwirth, Pavel

doi:10.1021/jp405683s

Cited by 185 publications

(232 citation statements)

References 40 publications

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“…The fact that anion binding in water can be affected without complete desolvation – even in the absence of traditionally strong supramolecular motifs for anion recognition – suggests an alternative approach to this difficult task. Moreover, these results dovetail with what is known about anions at the air-water interface 31 and the macromolecule-water interface, 32 and regarding the latter, point to other ways than cation-anion or hydrogen bonding that anions can interact with proteins.…”

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confidence: 74%

Binding Hydrated Anions with Hydrophobic Pockets

et al. 2015

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Using a combination of Isothermal Titration Calorimetry and quantum and MD calculations, we demonstrate that relatively soft anions have an affinity for hydrophobic concavity. The results are consistent with the anions remaining partially hydrated upon binding, and suggest a novel strategy for anion recognition. Graphical abstractThe challenges associated with anion recognition are well known. 1 They have a range of geometries, may be pH sensitive, and are larger than the equivalent isoelectronic cations and have a lower charge to radius ratio. This diffuse nature means that across all the classes of functional groups utilized to bring about recognition, 1-2 those involving Coulombic attraction and hydrogen bonding have proven to be the most popular. This is particularly true for anion recognition in aqueous solution, where these strategies have been utilized to counter the strong interactions between the anion and its hydration shell. 3 Thus most of the reported hosts for anions that function in pure/buffered water are cationic. 4 Moving away from this strategy is the idea of utilizing halogen bonds for recognition; 5 an approach that takes advantage of the orthogonality between the requirements for forming halogen bonds, and those for forming hydrogen bonds; if the latter is not utilize, competition with water is less important.An alternative strategy is not to compete with the waters of hydration but to bind the anion with its solvation shell. Although a wide range of ditopic receptors have been synthesized and studied, 6 in general supramolecular chemistry has focused on the recognition of singular species. But why not recognize a hydrated anion rather than a "naked" one? Although this posses many challenges, it sidesteps the energetic requirements of ion desolvation, and has Correspondence to: Steven W. Rick; Bruce C. Gibb. Supporting Information. NMR and ITC titration experiments and details of the quantum and MD simulations. One of the key requirements for the recognition of hydrated anions is undoubtedly a large, well-defined, binding pocket; the circumambient nature of which allows for multi-point recognition. 8,9,10,11 But what are the specifics of such pockets? How many waters of hydration are easily removed from an anion, and is there a preferred hydration geometry for each anion type? Although much has been learned about isolated water clusters 12 and the solvation requirements of ions, 13 what we know of the structural requirements for recognizing hydrated ions is -to our knowledge -limited to the solid state. 14 We recently showed that perchlorate (ClO 4 − ) has an affinity for the hydrophobic pocket of cavitand 1, and that this association is dependent on the nature of other salts. 15 Furthermore, ClO 4 − binding is able to induce Hofmeister effects in the binding of amphiphilic guests to HHS Public Access 1. 16 Here we demonstrate that anion binding to the concavity of 1 is general, use ITC to identify that these complexation events are strongly exothermic and entropically penalized...

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confidence: 74%

Binding Hydrated Anions with Hydrophobic Pockets

et al. 2015

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“…The present results thus strongly indicate that Nandi and Robinson 6 actually did not succeed in capping the C -terminus. This observation, supported by the experimental fact that we were also unable to effectively cap the C -terminus of GGG by their esterification procedure (but instead had to use another synthetic route), 8 has important implications for molecular interpretations of the Hofmeister ordering of ions, as discussed below.…”

mentioning

confidence: 63%

“…However, we have found recently that while the N -terminus can be easily acetylated, it is actually rather difficult to cap the C -terminus of oligoglycines. 8 As a matter of fact, we were not able to effectively cap the C -terminus by the esterification procedure described in Ref. 6.…”

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confidence: 98%

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Effects of End-Group Termination on Salting-Out Constants for Triglycine

Hladílková

Heyda

Rembert

et al. 2013

J. Phys. Chem. Lett.

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Salting out constants for triglycine were calculated for a series of Hofmeister salts using molecular dynamics simulations. Three variants of the peptide were considered with both termini capped, just the N-terminus capped, and without capping. The simulations were supported by NMR and FTIR measurements. The data provide strong evidence that earlier experimental values of salting out constants assigned to the fully capped peptide (as previously assumed) should have been assigned to the half-capped peptide instead. Therefore, these values cannot be used to directly establish Hofmeister ordering of ions at the peptide backbone, since they are strongly influenced by interactions of the ions with the negatively charged C-terminus.

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“…11 Interactions may be better understood through simulations such as molecular dynamics which can probe equilibrium interactions. 12,13,14 However, there is no guarantee that these modelled interactions apply broadly to specific ion effects. Recently, it has been suggested that non-electrostatic ion-specific dispersion forces between solute and ion play a vital role in understanding Hofmeister effects.…”

Section: Introductionmentioning

confidence: 99%

Anion-Specific Effects on the Behavior of pH-Sensitive Polybasic Brushes

et al. 2015

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The anion-specific solvation and conformational behavior of weakly basic poly(2-dimethylamino)ethyl methacrylate (poly(DMA)), poly(2-diethylamino)ethyl methacrylate (poly(DEA)), and poly(2-diisopropylamino)ethyl methacrylate (poly(DPA)) brushes, with correspondingly increasing inherent hydrophobicity, have been investigated using in situ ellipsometric and quartz crystal microbalance with dissipation (QCM-D) measurements. In the osmotic brush regime, as the initial low concentration of salt is increased, the brushes osmotically swell by the uptake of solvent as they become charged and the attractive hydrophobic inter- and intrachain interactions are overcome. With increased ionic strength, the brushes move into the salted brush regime where they desolvate and collapse as their electrostatic charge is screened. Here, as the brushes collapse, they transition to more uniform and rigid conformations, which dissipate less energy, than similarly solvated brushes at lower ionic strength. Significantly, in these distinct regimes brush behavior is not only ionic strength dependent but is also influenced by the nature of the added salt based on its position in the well-known Hofmeister or lyotropic series, with potassium acetate, nitrate, and thiocyanate investigated. The strongly kosmotropic acetate anions display low affinity for the hydrophobic polymers, and largely unscreened electrosteric repulsions allow the brushes to remain highly solvated at higher acetate concentrations. The mildly chaotropic nitrate and strongly chaotropic thiocyanate anions exhibit a polymer hydrophobicity-dependent affinity for the brushes. Increasing thiocyanate concentration causes the brushes to collapse at lower ionic strength than for the other two anions. This study of weak polybasic brushes demonstrates the importance of all ion, solvent, and polymer interactions.

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Reversal of the Hofmeister Series: Specific Ion Effects on Peptides

Cited by 185 publications

References 40 publications

Binding Hydrated Anions with Hydrophobic Pockets

Binding Hydrated Anions with Hydrophobic Pockets

Effects of End-Group Termination on Salting-Out Constants for Triglycine

Anion-Specific Effects on the Behavior of pH-Sensitive Polybasic Brushes

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