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1.
ChemSusChem ; 8(19): 3294-303, 2015 Oct 12.
Artigo em Inglês | MEDLINE | ID: mdl-26280813

RESUMO

Agarose has been functionalized (acetylated/carbanilated) in an ionic liquid (IL) medium of 1-butyl-3-methylimidazolium acetate at ambient conditions. The acetylated agarose showed a highly hydrophobic nature, whereas the carbanilated agarose could be dissolved in water as well as in the IL medium. Thermoreversible ionogels were obtained by cooling the IL sols of carbanilated agarose at room temperature. The ionogel prepared from a protic-aprotic mixed-IL system (1-butyl-3-methylimidazolium chloride and N-(2-hydroxyethyl)ammonium formate) demonstrated a superior self-healing property, as confirmed from rheological measurements. The superior self-healing property of such an ionogel has been attributed to the unique inter-intra hydrogen-bonding network of functional groups inserted in the agarose. The ionogel was tested as a flexible solid electrolyte for an activated-carbon-based supercapacitor cell. The measured specific capacitance was found to be comparable with that of a liquid electrolyte system at room temperature and was maintained for up to 1000 charge-discharge cycles. Such novel functionalized-biopolymer self-healing ionogels with flexibility and good conductivity are desirable for energy-storage devices and electronic skins with superior lifespans and robustness.


Assuntos
Capacitância Elétrica , Sefarose/química , Acetilação , Eletroquímica , Géis , Imidazóis/química , Líquidos Iônicos/química , Fenômenos Mecânicos , Metanol/química
2.
Phys Chem Chem Phys ; 17(15): 10189-99, 2015 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-25798458

RESUMO

Choline dioctylsulfosuccinate [Cho][AOT] (a surface active ionic liquid) has been found to induce all-α to α + ß conformational transition in the secondary structure of enzyme cytochrome c (Cyt c) with an enhanced peroxidase activity in its aqueous vesicular phase at pH 7.0. [Cho][AOT] interacted with Cyt c distinctly at three critical concentrations (aggregation C1, saturation C2 and vesicular C3) as detected from isothermal titration calorimetric analysis. Oxidation of heme iron was observed from the disappearance of the Q band in the UV-vis spectra of Cyt c upon [Cho][AOT] binding above C3. Circular dichroism analysis (CD) has shown the loss in both the secondary (190-240 nm) and tertiary (250-300 nm) structure of Cyt c in the monomeric regime until C1, followed by their stabilization until the pre-vesicular regime (C1 → C3). Loss in both the secondary and tertiary structure has been observed in the post-vesicular regime with the change in Cyt c conformation from all-α to α + ß which is similar to the conformational changes of Cyt c upon binding with mitochondrial membrane (Biochemistry 1998, 37, 6402-6409), thus citing the potential utility of [Cho][AOT] membranes as an artificial analog for in vitro bio-mimicking. Fluorescence correlation spectroscopy (FCS) measurements confirm the unfolding of Cyt c in the vesicular phase. Dynamic light scattering experiments have shown the contraction of [Cho][AOT] vesicles upon Cyt c binding driven by electrostatic interactions observed by charge neutralization from zeta potential measurements. [Cho][AOT] has been found to enhance the peroxidase activity of Cyt c with maximum activity at C3, observed using 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt as the substrate in the presence of hydrogen peroxide. This result shows the relevance of tuning ionic liquids to surfactants for bio-mimicking of specific membrane protein-lipid interactions.


Assuntos
Citocromos c/química , Líquidos Iônicos/química , Peroxidase/metabolismo , Água/química , Calorimetria , Peróxido de Hidrogênio/química , Modelos Moleculares , Conformação Molecular , Oxirredução , Peroxidase/química , Conformação Proteica , Estrutura Secundária de Proteína
3.
J Colloid Interface Sci ; 428: 267-75, 2014 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-24910062

RESUMO

New anionic ionic liquid surfactants have been synthesized by replacing the sodium cation of Aerosol-OT (sodium dioctylsulfosuccinate, [Na]AOT) with various biocompatible moieties, such as 1-butyl-3-methyl imidazolium ([C4mim]), proliniumisopropylester ([ProC3]), cholinium ([Cho]), and guanidinium ([Gua]). The Aerosol-OT derived ionic liquids (AOT-ILs) were found fairly soluble in water and formed vesicles above a critical vesicle concentration (CVC) which depended upon the nature of cation, and followed the order: [ProC3]<[C4mim]<[Gua]<[Cho]

4.
J Phys Chem B ; 118(1): 115-24, 2014 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-24354643

RESUMO

3-Methyl-1-octylimidazolium dodecylsulfate, [C8mim][C12OSO3], a vesicle forming biamphiphilic ionic liquid (BAIL) (J. Phys. Chem. B 2012, 116, 14363-14374), has been found to induce significant folding alterations in the structure of bovine serum albumin (BSA) in the aqueous medium at pH 7.0. Such alterations have been investigated in detail using various physicochemical and spectroscopic techniques. Different concentration regimes (monomeric, shared aggregation, and post-vesicular) of [C8mim][C12OSO3]-BSA interactions have been defined through adsorption and binding isotherms using tensiometry and isothermal titration calorimetry (ITC). Fluorimetry, circular dichroism (CD), and dynamic light scattering (DLS) measurements have shown that [C8mim][C12OSO3] induces a small unfolding of BSA in the monomeric regime at low concentration (designated as C(f)), which is followed by a refolding up to critical aggregation concentration (CAC) (designated as C1). Above C1, i.e., in the shared aggregation concentration regime, again a small unfolding of BSA was observed up to critical vesicular concentration (CVC) (designated as C2). In the vesicular and post-vesicular regimes, the BSA remained stable against folding alterations. The kinetic stability of BSA in the vesicular concentration regimes was studied for a month using turbidimetry. It has been found that [C8mim][C12OSO3] stabilizes BSA against the aggregation which is the major cause of protein destabilization. The present study gives insights for the design of surface active ILs for protein stabilization as a potential replacement for the mixed micelles of conventional surfactants used in detergent industries for enzyme stabilization and as an artificial chaperone.


Assuntos
Líquidos Iônicos/química , Soroalbumina Bovina/química , Tensoativos/química , Animais , Bovinos , Modelos Moleculares , Conformação Proteica , Dobramento de Proteína , Água/química
5.
J Phys Chem B ; 116(49): 14363-74, 2012 Dec 13.
Artigo em Inglês | MEDLINE | ID: mdl-23171376

RESUMO

Biamphiphilic ionic liquids (BAILs) based on 1,3-dialkylimidazolium cation and alkyl sulfate anions ([C(n)H(2n+1)mim][C(m)H(2m+1)OSO(3)]; n = 4, 6, or 8; m = 8, 12) have been synthesized and characterized for their self-assembling behavior in the aqueous medium. Effects of alteration of alkyl chain length in cation and anion on surfactant properties of BAILs have been examined from surface tension measurements. The effectiveness of surface tension reduction for BAILs has been found to be exceptionally higher as compared to single chain surface active ILs/conventional surfactants. The thermodynamics of the aggregation process has been studied using isothermal titration calorimetry (ITC) and temperature dependent conductivity experiments. Dynamic light scattering (DLS), nuclear magnetic resonance (NMR), and transmission electron microscopy (TEM) studies showed that BAILs formed distinct aggregated structures depending upon the amphiphilic character present in the cation and anion. BAILs ([C(n)H(2n+1)mim][C(m)H(2m+1)OSO(3)]) form micelles when n = 4, 6; m = 8, intermicellar aggregates when n = 4, 6; m = 12, and vesicles when n = 8; m = 8, 12. Gold nanoparticles and microplates have been synthesized in micellar and vesicle solutions of BAILs using a simple photoreduction method. The studies show the potential of BAILs for constructing micelles and supramolecular assemblies, such as bilayer vesicles, which are effective in preparation of nanomaterials of controlled size and morphology.


Assuntos
Ouro/química , Líquidos Iônicos/química , Nanopartículas Metálicas/química , Tensoativos/química , Líquidos Iônicos/síntese química , Micelas , Tamanho da Partícula , Tensão Superficial , Tensoativos/síntese química , Termodinâmica , Água/química
6.
J Phys Chem B ; 115(47): 13847-53, 2011 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-22029384

RESUMO

Self-aggregation of amino acid ionic liquid surfactants (AAILSs) in aqueous solution has been investigated through surface tension, conductivity, steady-state fluorescence, dynamic light scattering (DLS), and transmission electron microscopy (TEM). The critical aggregation concentration (cac) of AAILSs obtained from different techniques showed fairly good agreement. Surface tension measurements have been used to derive surface adsorption properties such as adsorption efficiency (pC(20), effectiveness of surface tension reduction (Π(cac)), and minimum surface area per molecule (A(min)) at the air-water interface. Temperature-dependent conductivity measurements have been used to obtain the degree of counterion binding (ß), and the thermodynamic parameters such as standard free energy (ΔG(agg)(0)), enthalpy (ΔH(agg)(0)), and entropy (ΔS(agg)(0)) of aggregation. The aggregation number (N(agg)) for various AAILSs has been derived by using the fluorescence quenching technique. Size of the aggregates has been obtained from DLS and TEM measurements. The aggregation properties of AAILSs have been analyzed as a function of structure of amino acids and compared with those of analogous ionic liquids (ILs) and conventional ionic surfactants. Surface activity of the AAILSs has been found superior to that of analogous ILs and conventional ionic surfactants of the same alkyl chain length.


Assuntos
Aminoácidos/química , Líquidos Iônicos/química , Tensoativos/química , Condutividade Elétrica , Luz , Espalhamento de Radiação , Tensão Superficial , Temperatura , Termodinâmica , Água/química
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