Tracing Local Nanostructure of the Aqueous Solutions of the Biocompatible [Cho][Gly] Ionic Liquid: Importance of Hydrogen Bond Attraction between Like-Charged Ions (original) (raw)
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ACS Central Science, 2018
Long-term storage and stability of DNA is of paramount importance in biomedical applications. Ever since the emergence of ionic liquids (ILs) as alternate green solvents to aqueous and organic solvents, their exploration for the extraction and application of DNA need conscientious understanding of the binding characteristics and molecular interactions between IL and DNA. Choline amino acid ILs (CAAILs) in this regard seem to be promising due to their non-cytotoxic, completely biobased and environment-friendly nature. To unravel the key factors for the strength and binding mechanism of CAAILs with DNA, various spectroscopic techniques, molecular docking, and molecular dynamics simulations were employed in this work. UV−Vis spectra indicate multimodal binding of CAAILs with DNA, whereas dye displacement studies through fluorescence emission confirm the intrusion of IL molecules into the minor groove of DNA. Circular dichorism spectra show that DNA retains its native B-conformation in CAAILs. Both isothermal titration calorimetry and molecular docking studies provide an estimate of the binding affinity of DNA with CAAILs ≈ 4 kcal/mol. The heterogeneity in binding modes of CAAIL-DNA system with evolution of time was established by molecular dynamics simulations. Choline cation while approaching DNA first binds at surface through electrostatic interactions, whereas a stronger binding at minor groove occurs via van der Waals and hydrophobic interactions irrespective of anions considered in this study. We hope this result can encourage and guide the researchers in designing new bio-ILs for biomolecular studies in future.
On the Interactions between Amino Acids and Ionic Liquids in Aqueous Media
Journal of Physical Chemistry B, 2009
The understanding of the molecular-level interactions between biomolecules and ionic liquids (ILs) in aqueous media is crucial for the optimization of a number of relevant biotechnological processes. In this work, the influence of a series of amino acids on the liquid-liquid equilibria between 1-butyl-3-methylimidazolium tricyanomethane and water was studied to evaluate the preferential interactions between these three compounds. The solubility effects observed are dependent on the polarity, size, and charge distribution of the amino acid side chains and are explained in terms of a refined version of the model proposed earlier (Freire et al. J. Phys. Chem. B 2009, 113, 202; Tomé et al. J. Phys. Chem. B 2009, 113, 2815 for ion specific effects on aqueous solutions of imidazolium-based ILs. Although acting through different mechanisms, salting-in and saltingout phenomena possess a common basis which is the competition between water-amino acid side chain, IL-amino acid side chain, and water-IL interactions. The delicate balance between these interactions is dependent on the relative affinities of the biomolecules to water molecules or to IL cation and anion and determines the trend and magnitude of the solubility effect observed.
Journal of Molecular Liquids, 2019
The molecular interactions of amino acids with the different ionic liquids (ILs) are important in order to study the stability and behavior of the amino acids. In this study, we have examined the interactions of glycine in the aque-ous solutions with two aprotic ionic liquids based on cholinium cation, namely, cholinium propanoate [Chl][Pro] and cholinium hexanoate [Chl][Hex]. The different interactions were quantified through their partial molar volumes (V ϕ) where it was found that the shorter chained [Chl][Pro] interacts more with the molecules of the gly-cine, compared to [Chl][Hex]. The derivation of infinite dilution parameter through the application of the Masson equation revealed further insights into the different types of interactions. The calculated limiting partial molar volume of transfer, (ΔV ϕ 0 values for water to aqueous solutions of ILs indicated that hydrophobic-hydrophobic interactions dominates over other attractive interactions in longer chain [Chl][Hex] than in [Chl][Pro]. The calculation of hydration number (n H) revealed that with increasing IL concentrations, lesser number of water molecules remain attached to the glycine, indicating the structure breaking nature of the ILs, which were further confirmed from the Hepler equation.
The Journal of Physical Chemistry B, 2012
Although the understanding of the influence of ionic liquids (ILs) on the solubility behavior of biomolecules in aqueous solutions is relevant for the design and optimization of novel biotechnological processes, the underlying molecular-level mechanisms are not yet consensual or clearly elucidated. In order to contribute to the understanding of the molecular interactions established between amino acids and ILs in aqueous media, classical molecular dynamics (MD) simulations were performed for aqueous solutions of five amino acids with different structural characteristics (glycine, alanine, valine, isoleucine, and glutamic acid) in the presence of 1-butyl-3-methylimidazolium bis(trifluoromethyl)sulfonyl imide. The results from MD simulations enable to relate the properties of the amino acids, namely their hydrophobicity, to the type and strength of their interactions with ILs in aqueous solutions and provide an explanation for the direction and magnitude of the solubility phenomena observed in [IL + amino acid + water] systems by a mechanism governed by a balance between competitive interactions of the IL cation, IL anion, and water with the amino acids.
ACS Sustainable Chemistry & Engineering
Cholinium-based ionic liquids (Cho-ILs) are very attractive compounds for medicinal and pharmaceutical applications as bioavailability enhancers in drug formulations and active components in pharmaceutical ingredients. In this study, we synthesized six Cho-ILs from hydroxycinnamic acids (HCA) ([Cho][HCA] ILs), a group of bioactive compounds with poor water solubility. [Cho][HCA] ILs and their parent acids were evaluated for solubility, thermal stability, and antioxidant activity. Furthermore, [Cho]-[HCA] ILs were screened for their cytotoxicity. To rationalize the experimental antioxidant activities, density functional theory (DFT) calculations were performed. The theoretical approach allowed for identification of the most likely radical scavenging mechanisms involving HCAs and the corresponding ionic forms under the studied experimental conditions and to rationalize the observed activity differences between salts and acids. Overall, our results revealed a higher solubility and free-radical scavenging activity for [Cho][HCA] ILs than corresponding HCAs, a relatively high thermal stability (melting temperature > 100°C) and negligible cytotoxicity activity. Furthermore, DFT calculations showed that both the hydrogen atom transfer and the sequential proton loss electron transfer mechanisms are likely to occur in aqueous and ethanolic solutions. The picture emerging from our results supports the increasingly expressed idea that [Cho][HCA]ILs are promising candidates for applications in pharmaceutical formulation.
Journal of Molecular Liquids, 2020
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The Relationship between the Structure and Properties of Amino Acid Ionic Liquids
Molecules
Ionic liquids based on different l-amino acids (glycine, l-valine, l-leucine, l-isoleucine, l-histidine, l-methionine, l-tyrosine, l-tryptophan, l-arginine, and l-threonine) and different cations (tetrabutylammonium (TBA), tributylmethylammonium (tBMA), didecyldimethylammonium (DDA), (2-hydroxyethyl)trimethylammonium (choline) (Chol), alkyl(C12-C14) dimethylbenzylammonium (benzalkonium) (BA), dodecyltrimethylammonium (DDTMA), hexadecyltrimethylammonium (HDTMA), octadecyltrimethylammonium (ODTMA) and 1-ethyl-3-methylimidazolium (EMIM)) have been synthesized and characterized by NMR and FTIR. Viscosity, specific rotation, surface activity, thermal stability (TG), and phase transformations (DSC) have been determined and compared with available data. Furthermore, benzalkonium, didecyldimethylammonium, dodecyltrimethylammonium, hexadecyltrimethylammonium, and octadecyltrimethylammonium amino acid ionic liquids have been shown to exhibit surface activity. The dissolution of cellulose in a...
This study reports pH dependent stability of protein dispersions of five common proteins, bovine serum albumin (BSA), human serum albumin (HSA), immunoglobulin (IgG), β-lactoglobulin (β-Lg), and gelatin-B (Gel-B), all having isoelectric pH, pI ≈ 5, in room temperature ionic liquid solutions of 1methyl-3-alkyl (hexyl/octyl) imidazolium chloride (concentration 0−0.2% w/v). Molecular hydrophobicity index, (H-index = hydrophobicity/hydrophilicity) of these molecules spanned the range 0.43−0.87. Electrophoretic characteristics, surface tension data and hydrodynamic size information revealed that IL solutions provide dispersion stability owing to specific protein-IL binding which did not alter their pI values though their surface charge was considerably screened. Change in maximum (ζ max ) and minimum (ζ min ) zeta potential values observed at pH ∼3 (maximum protonated state) and pH ∼8 (maximum deprotonated state) could be described universally as function of IL concentration, c as Δζ