When Ions Defy Electrostatics: The Case of Superchaotropic Nanoion Adsorption

Hohenschutz, Max; Dufrêche, Jean‐François; Diat, Olivier; Bauduin, Pierre

doi:10.1021/acs.jpclett.3c00095

Cited by 9 publications

(14 citation statements)

References 39 publications

(104 reference statements)

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“…Recent reports highlight the intriguing properties of certain inorganic polynuclear anions, such as polyoxometalates (POMs) or polynuclear clusters for their extremely high propensity to interact strongly in aqueous solution with zwitterionic lipids or nonionic organic components such as glucoside-based or polyethylene glycol-based surfactants or macrocycles (cyclodextrins or cucurbiturils). − Thermochemical studies supported by theoretical calculations indicated that the chaotropic nature of these ionic species was responsible for these aggregation phenomena, leading to the extension of the Hofmeister series beyond the classical anions (SCN – , ClO 4 – , etc. ). , Besides, the magnitude of the chaotropic effect correlates well with the variation of the charge density along the archetypical Keggin-type POM series . Recently, the Mo-blue ring-shaped giant anion , [Mo 154 O 462 H 14 (H 2 O) 70 ] 14– (abbreviated {Mo 154 } hereafter) has been identified experimentally as the most superchaotropic POM species .…”

Section: Introductionmentioning

confidence: 76%

“…C8G1 is an amphiphilic molecule widely used in biochemistry, especially in the extracting processes of membrane proteins from biological matters. , C8G1 has a high critical micellar concentration (cmc ≈ 25 mM at 25 °C) with a high aggregation number which varies from N Agg = 80 to 130 upon increasing concentration above cmc. , Besides, due to the relative rigidity of the glycoside hydrophilic head, C8G1 has been used frequently as a building block either for the preparation of large unilamellar vesicles or for modeling biomembrane systems that integrate membrane proteins. , Alternatively, C8G1 is used also as an ingredient in the crystallization of membrane proteins . Furthermore, previous studies report on the high affinity of some archetypal POMs such as the superchaotropic Keggin-type anion [PW 12 O 40 ] 3– with the C8G1 surfactant. , Herein, the C8G1–{Mo 154 } supramolecular interactions and related structures were evidenced through a set of complementary methods such as single-crystal X-ray diffraction analysis assisted by molecular modeling, small-angle X-ray scattering (SAXS), and cryo-TEM observations. Furthermore, surface tension measurement using the Du Noüy ring technique, fluid viscosity measurement, 1 H NMR including DOSY, and isothermal titration calorimetry allow us to unravel a multiscale picture of the self-assembly behavior from discrete species to the structure of large single-walled hollow vesicles.…”

Section: Introductionmentioning

confidence: 99%

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Cooperative Self-Assembly Process Involving Giant Toroidal Polyoxometalate as a Membrane Building Block in Nanoscale Vesicles

Falaise,

Khlifi,

Bauduin

et al. 2024

J. Am. Chem. Soc.

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The self-assembly of organic amphiphilic species into various aggregates such as spherical or elongated micelles and cylinders up to the formation of lyotropic hexagonal or lamellar phases results from cooperative processes orchestrated by the hydrophobic effect, while those involving ionic inorganic polynuclear entities and nonionic organic components are still intriguing. Herein, we report on the supramolecular behavior of giant toroidal molybdenum blue-type polyoxometalate, namely, the {Mo 154 } species in the presence of n-octyl-β-glucoside (C8G1), widely used as a surfactant in biochemistry. Structural investigations were carried out using a set of complementary multiscale methods including single-crystal X-ray diffraction analysis supported by molecular modeling, small-angle X-ray scattering and cryo-TEM observations. In addition, liquid NMR, viscosimetry, surface tension measurement, and isothermal titration calorimetry provided further information to decipher the complex aggregation pathway. Elucidation of the assembly process reveals a rich scenario where the presence of the large {Mo 154 } anion disrupts the selfassembly of the C8G1, well-known to produce micelles, and induces striking successive phase transitions from fluid-to-gel and from gel-to-fluid. Herein, intimate organic−inorganic primary interactions arising from the superchaotropic nature of the {Mo 154 } lead to versatile nanoscopic hybrid C8G1−{Mo 154 } aggregates including crystalline discrete assemblies, smectic lamellar liquid crystals, and large uni-or multilamellar vesicles where the large torus {Mo 154 } acts a trans-membrane component.

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Section: Introductionmentioning

confidence: 76%

Section: Introductionmentioning

confidence: 99%

Cooperative Self-Assembly Process Involving Giant Toroidal Polyoxometalate as a Membrane Building Block in Nanoscale Vesicles

Falaise,

Khlifi,

Bauduin

et al. 2024

J. Am. Chem. Soc.

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“…One of the most striking features of superchaotropic ions is their enthalpically driven binding to polar interfaces . One example is the interaction with nonionic BrijO10 surfactants .…”

Section: Resultsmentioning

confidence: 99%

“…The tendency of ions to bind to the hydrophobic air–water surface or to polar tetraethylene glycol increases with increasing size and is a motif different from hydrophobic binding that can already be observed on the level of a single ion. These properties can drive recent observations that superchaotropic ions bind to nonionic micelles like noninteracting particles . Further effects like aggregation of polyoxometalates in the presence of large tetrabutylammonium counterions will require another study addressing the interactions between nanoions and their respective counterions.…”

Section: Discussionmentioning

confidence: 99%

Solvation of Nanoions in Aqueous Solutions

Dullinger,

Horinek

2023

J. Am. Chem. Soc.

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In recent years it has been increasingly recognized that different classes of large ions with multiple valency have effects conceptually similar to weakly solvated ions in the Hofmeister series, also labeled by the term chaotropic. The term “superchaotropic effect” has been coined because these effects are much more strongly pronounced for nanometer-sized ions, whose adsorption properties often resemble typical surfactants. Despite this growing interest in these nanometer-sized ions, a simple conceptual extension of the Hofmeister series toward nanoions has not been achieved because an extrapolation of the one-dimensional surface charge density scale does not lead to the superchaotropic regime. In this work, we discuss a generic model that is broadly applicable to ions of nearly spherical shape and thus includes polyoxometalates and boron clusters. We present a qualitative classification scheme in which the ion size appears as a second dimension. Ions of different sizes but the same charge density differ in their bulk solvation free energy. As the ions grow bigger at constant surface charge density, they become more stable in solution, but the adsorption behavior is still governed by the surface charge density. A detailed molecular dynamics simulation study of large ions that is based on a shifted Lennard-Jones potential is presented that supports the presented classification scheme.

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“…Scientific breakthroughs since 2015 showed that some Keggin POMs such as PW 12 O 40 3– (PW) and SiW 12 O 40 4– (SiW) spontaneously bind to nonionic hydrated matter, such as nonionic polymers, , surfactants, , or small organic molecules. , A water-mediated driving force, called the chaotropic effect, − causes the POMs to bind to nonionic interfaces/molecules. Upon binding, water molecules in the hydration shells of the POM and of the interface are released and recover H-bonds in the water bulk, which makes the chaotropic binding processes enthalpically driven.…”

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confidence: 99%

Nonionic Microgels Adapt to Ionic Guest Molecules: Superchaotropic Nanoions

Simons,

Hazra,

Petrunin

et al. 2024

ACS Nano

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Microgels are commonly applied as solute carriers, where the size, density, and functionality of the microgels depend on solute binding. As representatives for ionic solutes with high affinity for the microgel, we study here the effect of superchaotropic Keggin polyoxometalates (POMs) PW 12 O 40 3− (PW) and SiW 12 O 40 4− (SiW) on the aqueous swelling and internal structure of nonionic poly(N-isopropylacrylamide) (pNiPAM) microgels by light scattering techniques and smallangle X-ray scattering. Due to their weak hydration, these POMs bind spontaneously to the microgels at millimolar concentrations. The microgels thus become charged and swell at low POM concentration, surprisingly without strongly increasing the volume phase transition temperature, and deswell at higher POM concentration. The swelling arises because of the osmotic pressure of dissociated counterions of the POMs, while the deswelling is due to POMs acting as physical cross-links in the microgels under screened electrostatics in NaCl or excess POM solution. This swelling/deswelling transition is sharper for PW than for SiW related to the lower charge density, weaker hydration, and stronger binding of PW. The POMs elicit qualitatively and quantitatively different swelling effects from ionic surfactants and classical salts. Moreover, the network softness and topology govern the swelling response upon POM binding. The softer the microgel, the stronger is the swelling response, while, inside the microgel, regions of high polymer density swell/contract more upon electric charging/cross-linking than regions with low polymer density. POM binding thus enables fine-tuning of microgel properties and highlights the role of network topology in microgel swelling. Because POMs decompose at an alkaline pH, these POM/microgel systems also exhibit pH-responsive swelling in addition to the typical temperature responsiveness of pNiPAM microgels.

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When Ions Defy Electrostatics: The Case of Superchaotropic Nanoion Adsorption

Cited by 9 publications

References 39 publications

Cooperative Self-Assembly Process Involving Giant Toroidal Polyoxometalate as a Membrane Building Block in Nanoscale Vesicles

Cooperative Self-Assembly Process Involving Giant Toroidal Polyoxometalate as a Membrane Building Block in Nanoscale Vesicles

Solvation of Nanoions in Aqueous Solutions

Nonionic Microgels Adapt to Ionic Guest Molecules: Superchaotropic Nanoions

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