Studies on the Effect of Amino Acids/Peptide on Micellization of SDS at Different Temperatures

Thermodynamic Insights of the Molecular Interactions of Dopamine (Neurotransmitter) with Anionic Surfactant in Non-Aqueous Media

This study was aimed at establishing the interactions prevailing in an anionic surfactant, sodium dodecyl sulfate, and dopamine hydrochloride in an alcoholic (ethanol) media by using volumetric, conductometric, and tensiometric techniques. Various methods were utilized to estimate the critical micelle concentration (cmc) values at different temperatures. The entire methods yielded the same cmc values. The corresponding thermodynamic parameters viz. the standard free energy of micellization (Gmico), enthalpy of micellization (Hmico), and entropy of micellization (Smico) were predicted by applying the pseudo-phase separation model. The experimental density data at different temperatures (298.15 K, 303.15 K, 308.15 K, and 313.15 K) were utilized to estimate the apparent molar volumes (Vϕo) at an infinite dilution, apparent molar volumes (Vφcmc) at the critical micelle concentration, and apparent molar volumes (ΔVφm) upon micellization. Various micellar and interfacial parameters, for example, the surface excess concentration (Γmax), standard Gibbs free energy of adsorption at the interface (ΔGoad), and the minimum surface area per molecule (Amin), were appraised using the surface tension data. The results were used to interpret the intermolecular interactions prevailing in the mixed systems under the specified experimental conditions.

A Review on Interactions between Amino Acids and Surfactants as Well as Their Impact on Corrosion Inhibition

Amino acid-surfactant interactions are central to numerous studies because of their increased effectiveness in chemical, biological, household and industrial use. This review will focus on the impact and effect of the physicochemical properties, temperature, pH, and surfactant chain length of the amino acid for detailed exploration of amino acids and surfactants in aqueous medium. The impact of cosolvent on self-aggregation, critical micelle concentration (CMC), and binding affinity with other biomolecules, as well as amino acid-surfactant interactions, are the epicenters. The results show that increasing the temperature causes negative enthalpy for ionic surfactants and micellization, implying that micellization and amino acids are thermodynamically spontaneous and exothermic, accompanied by positive entropy. As these physicochemical studies are additive, the amino acid and ionic surfactant interactions provide clues on protein unfolding and denaturation under different media, which further changes with a change in physiological conditions like pH, cosolvent, chain length, and temperature. On varying the pH, the net charge of the amino acid also changes and, subsequently, the binding efficiency of the amino acids to the surfactants. The presence of cosolvent causes a lowering in the hydrophobic chain, which changes the surfactant's CMC. At a reduced CMC, the hydrophobic characteristic of amino acid-surfactant associations is amplified, leading to rapid denaturation of proteins that act as propulsion under the influence of extended chain surfactants. Amino acids are one of the most intriguing classes of chemicals that produce high inhibitory efficacy. Amino acids are also a component of proteins and therefore, found in a significant part of the human body, further making them a promising candidate as corrosion inhibitors. In this review article, authors have also focused on the collection and investigation for application of amino acid-surfactant interactions in corrosion inhibition. Various predictive studies/in silico studies are also reported by many research groups, such as density functional theory (DFT) calculations and molecular dynamics simulations to obtain tentative electronic, structural, and physiochemical characteristics like energies of the highest occupied molecular orbitals and lowest unoccupied molecular orbitals, binding energy, Gibb's free energy, electronegativity, polarizability, and entropy. In silico studies are helpful for the mechanism predictions of the process occurring on metal surfaces.

Effect of amino acid on the surface adsorption and micellar properties of surface active ILs varying in cationic head groups

The interfacial along with bulk characteristics of the aqueous solutions of ILs with dissimilar cationic head group viz. 1-dodecyl-3-methylimidazolium bromide ([C₁₂mim][Br]), and N-dodecyl-N-methylmorpholinium bromide ([Mor_1,12][Br]) in the absence and the presence of an amino acid L-Methionine as an external additive have been examined by electrical conductivity, UV-Visible, surface tension, and DLS measurements. The CMC values, and the lowest maximum surface excess concentration (Г_max) achieved from all three techniques, and surface tension measurements respectively displayed more surface activity of the [C₁₂mim][Br] than the [Mor_1,12][Br]. Also, the morpholinium head group is less hazardous than imidazolium, it can be utilised to design ILs that are greener, mainly in combination with polar, small, and non-toxic side chains and anions.

Study on the Effects of Biologically Active Amino Acids on the Micellization of Anionic Surfactant Sodium Dodecyl Sulfate (SDS) at Different Temperatures

The micellar properties of the anionic surfactant, sodium dodecyl sulfate (SDS) are modified by the biologically active amino acids. Amino acids (AAs) have experienced a variety of interactions and are proposed to influence SDS micelles due to their nominated hydrophobic interactions. The present study determines the critical micellar concentration (CMC) of SDS in aqueous solutions as well as in amino aqueous solutions. Three amino acids (glutamic acid, histidine, and tryptophan) are considered here. The conductometric measurements were carried out using a wide range of SDS concentrations at different temperatures. Surface tension experiments have also been applied to estimate many surface parameters including surface excess concentration (Γmax), surface occupied area per surfactant molecule (Amin), surface tension at CMC (γcmc), surface pressure at CMC (Πcmc) and Gibbs free energy of adsorption (∆Gads°), enthalpy ∆Hm° and the critical packing parameter (CPP). Interestingly, CMC values of SDS in water and in aqueous amino acids estimated by the surface tension method are comparable with the corresponding values obtained by the conductance method. The thermodynamic parameters of SDS micellization were also evaluated in both presence and absence of AAs. The additives of AAs work to reduce the CMC values, as well as the SDS thermodynamic parameters. This reduction is highly dependent on the hydrophobicity of the AA side chain. Negative values of ∆Gm°, ∆Hm° elucidate that micellization of SDS in the presence of amino acids is thermodynamically spontaneous and exothermic. The outcomes here might be utilized for pharmaceutical applications to stabilize proteins and inhibit protein aggregation.

Study of Intermolecular Interactions of CTAB with Amino Acids at Different Temperatures: A Multi Technique Approach

The densities, ρ, viscosities, η and specific conductivities κ, of (0.0002, 0.0004, 0.0006 and 0.0008 m) CTAB in 0.1 m aqueous valine, leucine and isoleucine were measured at different temperatures. The measured data were used to calculate various useful thermodynamic parameters. A complete characterization of any mixture can be performed by means of these thermodynamic properties. The apparent molar volume, ϕv , partial molar volume, ϕ v 0 $\phi _v^0$ and partial molar isobaric expansibilities, ϕ E 0 , $\phi _E^0,$ were calculated using density data. The viscosity data were analyzed using Jones–Dole equation to obtain viscosity coefficients, A- and B-, free energy of activation per mole of solvent, Δμ 1°∗, and solute, Δμ 2°∗, enthalpy, ΔH ∗ and entropy, ΔS ∗ of activation of viscous flow. Measuring the changes in these properties has been found to be an excellent qualitative and quantitative way to obtain information regarding the molecular structure and intermolecular interactions occurring in these mixtures. Various structure-making/breaking ability of solute (cetyltrimethylammonium bromide) in presence of aqueous amino acid solutions were discussed. In addition, fluorescence study using pyrene as a photophysical probe has been carried out, the results of which support the conclusions obtained from other techniques.

Synthesis of Copper Nanoparticles in Ethylene Glycol by Chemical Reduction with Vanadium (+2) Salts

Copper nanoparticles have been synthesized in ethylene glycol (EG) using copper sulphate as a precursor and vanadium sulfate as an atypical reductant being active at room temperature. We have described a technique for a relatively simple preparation of such a reagent, which has been electrolytically produced without using standard procedures requiring an inert atmosphere and a mercury cathode. Several stabilizing agents have been tested and cationic capping agents have been discarded owing to the formation of complex compounds with copper ions leading to insoluble phases contaminating the metallic nanoparticles. The elemental copper nanoparticles, stabilized with polyvinylpyrrolidone (PVP) and sodium dodecyl sulphate (SDS), have been characterized for composition by energy dispersive X-ray spectroscopy (EDS), and for size by dynamic light scattering (DLS), and transmission electron microscopy (TEM), giving a size distribution in the range of 40-50 nm for both stabilizing agents. From a methodological point of view, the process described here may represent an alternative to other wet-chemical techniques for metal nanoparticle synthesis in non-aqueous media based on conventional organic or inorganic reductants.

Surfactant-Amino Acid and Surfactant-Surfactant Interactions in Aqueous Medium: a Review

An overview of surfactant-amino acid interactions mainly in aqueous medium has been discussed. Main emphasis has been on the solution thermodynamics and solute-solvent interactions. Almost all available data on the topic has been presented in a lucid and simple way. Conventional surfactants have been discussed as amphiphiles forming micelles and amino acids as additives and their effect on the various physicochemical properties of these conventional surfactants. Surfactant-surfactant interactions in aqueous medium, various mixed surfactant models, are also highlighted to assess their interactions in aqueous medium. Finally, their applied part has been taken into consideration to interpret their possible uses.

Thermodynamics of Micellization of Triton X-100 in Aqueous Glycine: Tensiometric and Ultrasonic Studies

Surface tension and compressibility behavior of p-(1,1,3,3-tetramethylbutyl) phenoxypoly(oxyethylene glycol) (Triton X-100, TX-100) in aqueous mixture of glycine (Gly) have been studied at 298.15, 303.15, 308.15, and 313.15 K below and above the micellar composition range. Critical micelle concentration, cmc, of the surfactant TX-100 was obtained by surface tension, γ, density, ρ, and ultrasonic velocity, u, measurements at different temperatures. From the surface tension data, the surface excess concentration, Γ  max  σ , minimum area per molecule, A  min , Gibbs free energy, ΔG mic 0, enthalpy, ΔH mic 0, and entropy, ΔS mic 0 of micelle formation have been evaluated. Apparent molar adiabatic compressibility, κ ϕ , was calculated from density and ultrasonic velocity data. The values of κ ϕ and apparent molar adiabatic compressibility at infinite dilution, κ ϕ 0, in the pre-micellar region and apparent molar compressibility upon micellization, Δκ ϕ m , were obtained. The observed cmc of TX-100 in aqueous glycine is found to be smaller than its value in pure water. A comparison of Γ  max  σ in aqueous glycine with that in pure water suggests higher adsorption of TX-100 molecules at the air–liquid interface in the former solvent than in the latter one. This was attributed to the highly hydrophilic nature of glycine molecules, causing dehydration of the surfactant molecules, thereby, facilitating the adsorption of TX-100 molecules at the air–liquid interface in the presence of glycine than in its absence. The calculated values of the Gordon parameter, G parameter, suggest that aqueous glycine acts as a good solvent for the micellization of TX-100 amphiphiles. Negative values of ΔG mic 0 and ΔH mic 0 indicate that the process of micellization of the surfactant is spontaneous and exothermic. Moreover, higher values of − TΔS mic 0 than those of ΔH mic 0 truly endorse the view that micellization of TX-100 in aqueous glycine is primarily governed by the entropy gain due to the transfer of hydrophobic groups of the surfactant from the solvent environment to the interior of the micelle. The trends in the behavior of the compressibility parameters also endorse the micellization of TX-100 in aqueous glycine.