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Phase separation in amphiphilic systems is an important phenomenon. The temperature at which an amphiphilic solution phase separates is known as Cloud Point (CP). This article reviews in detail the process of phase separation in various amphiphiles (surfactants, polymers and drugs) and effect of different classes of additives on the CP of these amphiphilic systems. Ions affect the CP of drugs in a different way: kosmotropes and hard bases decrease while chaotropes and soft bases increase the CP of nonionic and cationic surfactants. Anionic surfactants show CP in presence of quaternary salts only. Thus, depending upon the nature and concentration of additive, the CP of an amphiphilic system gets increased or decreased and, hence, properties of the system may be tuned as per the need and use. A system with CP at high concentration can be made to phase separate at lower concentration by simply introducing an appropriate additive in it. This makes the system cost effective. On the other hand, if not required, a low CP can be enhanced with the help of another type of a suitable additive. [ABSTRACT FROM AUTHOR]

Herein we provide a detailed result about the effect of various additives, viz. inorganic salts, quaternary ammonium bromides (QABs) and amino acids on clouding behavior of amphiphilic drug amitriptyline hydrochloride (AMT). The continuous increase in the cloud point ( CP ) of drug by increase in inorganic salt concentration and the magnitude of increases rely upon the position of the salts in Hofmeister series and hydrated radii. The QABs also influence continuous increase in the CP , which is illustrated in terms of the alkyl chain length of peculiar QAB. The effect of amino acids on CP of the drug solution is dependent upon the characteristics (acidic, basic, polar or nonpolar) of particular amino acids. The overall behavior of additives has been analyzed and discussed on the basis of electrostatic repulsion or interaction, micellar growth, and mixed micelle formation between the ingredients. In addition to this, thermodynamic parameters are also evaluated. [ABSTRACT FROM AUTHOR]

Herein we have studied the interaction of β-cyclodextrin (β-CD) with the amphiphilic drug promazine hydrochloride (PMZ) by using conductimetry and viscometry. From the observed results it was concluded that critical micelle concentration (cmc) of the pure drug was lower than the apparent critical micelle concentration (cmc ∗ ) of the drug in the presence of β-CD. The cmc ∗ increased on increasing the concentration of β-CD due to the encapsulation of the amphiphilic drug to the hydrophobic cavities of the β-CD which delayed the micelle formation. Viscosity of the solution decreased drastically on the addition of β-CD which further increased on increasing the drug solution. Free energies of micellization (Δ G mic ) were calculated with the help of degrees of micelle ionization and cmc obtained from the specific conductivity−[PMZ] plots. Micellization was found to be less spontaneous in the presence of cyclodextrin. [ABSTRACT FROM AUTHOR]

Tensiometric and NMR techniques have been utilized to study binary mixtures of tetradecyltriphenylphosphonium bromide (TTPB) with a series of gemini surfactants, viz. butanediyl-1,4-bis(dimethyltetradecylammonium bromide) (14- 4 -14, 2Br − ), pentanediyl-1,5-bis(dimethyltetradecylammonium bromide) (14- 5 -14, 2Br − ), hexanediyl-1,6-bis(dimethyltetradecylammonium bromide) (14- 6 -14, 2Br − ), and a conventional surfactant tetradecyltrimethylammonium bromide (TTAB) in aqueous medium at 303 K. The results obtained from tensiometric measurements have been analyzed by considering theoretical models of Clint, Rubingh and Rosen. The mixed surfactant systems show lower critical micelle concentration values than those of the individual components and that predicted by ideal mixing and strong synergism are observed in the systems. Throughout the entire bulk phase compositions of the components, the fractions of TTPB within the micelles and monolayers remain almost same. The 1 H NMR studies reveal that 14- 4 -14, 2Br − is more de-shielded than the other geminis elucidating that these micelles are crowded with more N-methyl protons. [ABSTRACT FROM AUTHOR]

The effect of cationic micelles of cetyltrimethylammonium bromide (CTAB) on the interaction of dipeptide glycyl-tyrosine (Gly-Tyr) with ninhydrin under varying conditions has been studied spectrophotometrically at 70 °C and pH 5.0. The reaction followed first- and fractional-order kinetics with respect to [Gly-Tyr] and [ninhydrin], respectively. Increase in total concentration of CTAB from 0 to 70 × 10 −3 mol dm −3 resulted in an increase in the pseudo-first-order rate constant ( k ψ ) by a factor of ca. 3. Quantitative kinetic analysis of k ψ − [CTAB] data was performed on the basis of pseudo-phase model of the micelles (proposed by Menger and Portnoy and developed by Bunton) and Piszkiewicz model. A possible mechanism has been proposed and the kinetic data have been used to evaluate the micellar binding constants K S (268 mol −1 dm 3 for Gly-Tyr) and K N (64 mol −1 dm 3 for ninhydrin). [ABSTRACT FROM AUTHOR]

The effect of gelatin on the micellization behavior of amphiphilic drug nortriptyline hydrochloride (NOT) in aqueous as well as aqueous urea (250 mM) solutions has been studied using conductimetric technique. NOT is indicated for the relief of symptoms of depression. It is a tricyclic antidepressant drug. The drug interacts with gelatin similar to the interaction of surfactants and polymers. The plots of specific conductivity versus concentration of drug were nonlinear with three different linear regions with two clear breaks. The first break point, i.e. , critical aggregation concentration (cac), appeared well below the typical critical micelle concentration (cmc). The second break point is considered as polymer saturation point (psp) that is similar to cmc. The cac value decreases on increasing the gelatin concentration, whereas psp value increases for all fixed concentrations (%, w/v) of gelatin which is a clear signal of the interaction of the drug with gelatin. Free energies of aggregation (ΔGagg) and micellization (ΔGmic) were also evaluated. In the presence of urea the increase in the surface charge of the micelles was observed followed by halt of the aggregation. Effect of NOT (drug) on the secondary structure of gelatin in aqueous solutions was also examined using CD measurements. The measurements verified that the random coil content of gelatin increases with increasing the NOT concentration. [ABSTRACT FROM AUTHOR]

We have assessed the biological properties such as cytotoxicity and antimicrobial activity of a series of biocompatible ester-linked cationic gemini surfactants, ethane-1,2-diyl bis( N , N -dimethyl- N -alkylammoniumacetoxy) dichlorides (m-E2-m, m = 12, 14, 16). The effect of alkyl chain length (12, 14 and 16 carbon atoms) on their antimicrobial activity and cytotoxicity was examined. Antimicrobial activity of m-E2-m, against various prokaryotic and eukaryotic microorganisms, was studied by measuring the diameter of inhibition zone whereas cytotoxicity was evaluated using 3T3-L1 fibroblast cells. Toxic effect against these cells depends upon the type of the target microorganisms, nature of the cells, and hydrophobicity of the molecules. Antimicrobial activity of the gemini surfactant 16-E2-16 is lower than that of its corresponding single-chain counterpart. The gemini surfactants used for the present study (m-E2-m) which have excellent surface properties and much lower cmc values show low toxicity and significant antimicrobial activity. [ABSTRACT FROM AUTHOR]

Three homologues of a novel biodegradable diester-linked cationic gemini surfactant series, C m H 2m+1 (CH 3 ) 2 N + (CH 2 COOCH 2 ) 2 N + (CH 3 ) 2 C m H 2m+1 .2Cl − (m-E2-m; m = 12, 14, 16), were used for investigation of the solubilization of polycyclic aromatic hydrocarbons (PAHs) such as naphthalene, anthracene and pyrene in single as well as binary surfactant solutions. Physicochemical parameters of the pure/mixed systems were derived by conductivity and surface tension measurements. Dissolution capacity of the equimolar binary surfactant solutions towards the PAHs was studied from the molar solubilization ratio ( MSR ), micelle–water partition coefficient (K m ) and free energy of solubilization (Δ G s 0 ) of the solubilizates. Influence of hydrophobic chain length of the dimeric surfactants on solubilization was characterized. Aqueous solubility of the PAHs was enhanced linearly with concentration of the surfactant in all the pure and mixed gemini–gemini surfactant systems. [ABSTRACT FROM AUTHOR]

The micellization and interfacial properties of three homologous dicationic ester-bonded cleavable and biodegradable gemini surfactants, ethane-1,2-diyl bis( N , N -dimethyl- N -alkylammoniumacetoxy) dichlorides, referred as m-E2-m (m = 12, 14, 16), and their binary mixtures were investigated in aqueous solution by performing conductivity and surface tension measurements. The decrease in critical micelle concentration (CMC) indicates nonideality of the mixed systems of different compositions. The unequal hydrophobic chain length might be playing a significant role in the reduction of CMC values. Several theoretical treatments were used to analyze and compare the mutual interaction parameters, counter ion binding, surface parameters, excess free energy of micellization and standard free energies for the mixed surfactant systems as well. The negative values of interaction parameters show an overall attractive force, i.e., synergistic effect in the mixed state. The excess free energy of mixing has negative values for all the systems. [ABSTRACT FROM AUTHOR]

In this research article we have examined the effect of chloride (Cl − ), sulphate (SO 4 2 − ), phosphate (PO 4 3 − ), anthranilate (An − ) and tosylate (Tos − ) counterions on the physicochemical characteristics of green gemini surfactant, ethane-1,2-diyl bis( N , N- dimethyl- N -tetradecylammoniumacetoxy) dichloride (14-E2-14) through a multidimensional approach. Substantial changes were observed in the physicochemical parameters. Counterions were found to cause reduction in critical micellar concentration (CMC) and minimum area per head group ( A min ) of the 14-E2-14 gemini surfactant. However, increase in aggregation number ( N g ) and surface excess concentration ( Γ max ) of the 14-E2-14 surfactant was observed upon increasing the counterion concentrations. The Gibbs free energies of micellization (Δ G° mic ) and adsorption (Δ G° ads ) were found to be negative, indicating that 14-E2-14 micellization is spontaneous. The order of efficacy of counterions to influence the micellar characteristics was: An − > Tos − > PO 4 3 − > SO 4 2 − > Cl − . Further, 1 H NMR results demonstrated morphological transitions (sphere-to-rod) and newer phase formation. The UV–vis and FT-IR results delineate intercalation of organic counterions (An − and Tos − ) into the palisade layer of 14-E2-14 micelles. TEM micrographs show emergence of non-spheroidal micelles at higher counterion concentrations. This study could be significant to surfactant science scientists in tailoring green surfactants with desirable physicochemical characteristics, so that special-characteristic-tailored surfactants could be exploited in designing and compilation of environmentally benign industrial, cosmetic and biomedical products. [ABSTRACT FROM AUTHOR]

Binding interaction of a synthesized biodegradable gemini surfactant, ethane-1, 2-diyl bis(N, N-dimethyl-N-dodecylammoniumacetoxy) dichloride (12-E2-12), with bovine milk xanthine oxidase (XO) was studied using tensiometry, fluorescence spectroscopy, UV, CD, FT-IR, TEM and molecular docking. Tensiometry revealed lowering in surface tension ( γ ) and critical micelle concentration (CMC) of 12-E2-12 upon XO combination, suggesting a significant interaction between XO and 12-E2-12 (both in the bulk as well as at interface). Intrinsic fluorescence studies depict that 12-E2-12 quenches XO fluorescence intensity through static mechanism. The magnitude of binding parameters infers substantial and effective binding of 12-E2-12 to (XO). ANS and pyrene fluorescence demonstrate the exposure of aromatic residues (tyrosine/tryptophan) to a non-polar environment. UV, circular dichroism (CD) and FT-IR results delineate change in the secondary structure of the enzyme XO. Microscopic TEM micrographs confirm the disrupture of enzyme structure at higher concentrations of 12-E2-12. Molecular docking results show that 12-E2-12 binds to XO in the vicinity of both hydrophobic and hydrophilic residues, inferring that binding is governed by both hydrophilic and hydrophobic forces. This study may be of significance in biomedical world to further interpret mechanistic treatment modes of diseases like gout and hyperuricemia. Moreover, this study provides deeper biophysical insight into surfactant–protein interactions. [ABSTRACT FROM AUTHOR]

The kinetics of the title reaction has been investigated both in the aqueous and aqueous cationic micelles of tetradecyltrimethylammonium bromide (TTABr) solutions using UV–vis spectrophotometry at 343 K and pH 5.0. Ninhydrin reacts with [Cu(II)–Gly- l -Ala] + complex in the stoichiometric ratio of 1:1 in both media. To explain the dependence of the reaction rate on [TTABr], pseudo-phase model proposed by Berezin et al. [27] and developed by Bunton [28] and Vera and Rodenas [29] was used. The reaction follows first- and fractional-order kinetics with respect to [Cu(II)–Gly- l -Ala] T + and [ninhydrin] T , respectively, in aqueous and TTABr micelles. The values of k m , k w , K A , K Nin , E a , ΔH # , ΔS # , and ΔG # have been calculated. The effect of inorganic (NaNO 3 , Na 2 SO 4 , Na 3 PO 4 )/organic (NaBenz, NaSal) salts and organic solvents on the reaction rate has also been seen. A mechanism consistent with observed kinetic data has been proposed. [ABSTRACT FROM AUTHOR]

Surfactant solutions used in practical applications are generally mixtures of ionic and nonionic surfactants. These surfactants mostly show synergism on mixing. In this work, mixing behavior of cationic gemini surfactants, alkanediyl — α, ω — bis(dimethylalkylammonium bromide (alkyl: 14 or 16 and alkane: butane, pentane or hexane)), (m-s-m) and Cremophor RH over the entire mole fraction range was investigated tensiometrically. Results indicate that these mixtures show a negative deviation in the cmc id (cmc value at ideal mixing conditions). Micellar mole fraction of RH (X 1 m ) values indicate that RH has slightly higher contribution in mixed micelles than of geminis. X 1 m values are greater than of X 1 σ (mole fraction of RH at mixed interface). Adjustment of cationic head group of gemini is easier at the planar interface than in curved micellar head group area. Surface excess increases with the increase in α 1 . Different thermodynamic parameters (i.e., ΔG° mic , ΔG° ads , ΔG ex m , ΔG ex σ , G min ) also support mixed micelle formation. R p value and radius of micelles suggest that the mixed micelles at high α 1 are almost cylindrical in shape. [ABSTRACT FROM AUTHOR]

The micellization behavior of mixed zwitterionic/cationic solutions, that is, of zwitterionic phospholipid, 1, 2-dioctanoyl- sn -glycero-3-[phospho- L -serine] (sodium salt) (PL) and cationic gemini surfactants, alkanediyl-α,ω-bis(dimethylalkylammonium bromide (alkyl: 14 or 16 and alkane: butane, pentane or hexane) ( m - s - m ), have been studied by surface tension measurements. Various physicochemical properties, viz., critical micelle concentration (cmc), surface excess concentration ( Γ max ), minimum area per molecule ( A min ), interaction parameters ( β m , β σ ), and thermodynamic parameters such as standard Gibbs energy of micellization ( Δ G mic ° ), standard Gibbs energy of adsorption ( Δ G ads ° ), and excess free energy of mixing ( Δ G ex m ,   Δ G ex ° ), have been evaluated. The obtained results indicate that the mole fraction of PL in the mixed micelles, calculated on the basis of Rubingh's model, is different from stoichiometric mole fraction of PL ( α 1 ). The negative values of Δ G mic ° and Δ G ads ° show that the micelle formation and adsorption of surfactants at the air/solution interface is energetically favorable with the magnitude of Δ G ads ° greater than that of Δ G mic ° . The negative values of Δ G ex m and Δ G ex σ indicate better stability of the mixed systems. The insights presented herein on the gemini-phospholipid mixed micelle properties may find use towards their applications in the relevant areas of solubilization/drug delivery/etc. [ABSTRACT FROM AUTHOR]

A multi technique approach was utilized to explore the interaction between a novel green gemini surfactant, ethane-1,2-diyl bis(N,N-dimethyl-N-tetradecylammoniumacetoxy) dichloride (14-E2-14), with bovine milk xanthine oxidase (XO). Tensiometric, spectroscopic, microscopic and molecular modeling results demonstrate significant interaction and structural change of native xanthine oxidase upon 14-E2-14 combination. The results obtained in this study may be beneficial for scientists to calibrate conformation of the enzyme by novel biodegradable/green microstructures; consequently, it would likely add new impetus in understanding the treatment modes of various diseases like gout, hyperuricemia, liver and brain necrosis. Moreover, the 14-E2-14–XO interaction assists to unfurl new routes in the designing/selection of green-surfactant–protein mixtures widely used in food processing, cosmetics, and pharmaceutical industries. [ABSTRACT FROM AUTHOR]

A biodegradable ester-bonded cationic gemini surfactant (ethane-1,2-diyl bis( N , N -dimethyl- N -tetradecylammoniumacetoxy) dichloride), referred to as 14-E2-14, was synthesized whose aggregation behavior in aqueous solutions in the presence of salts (KCl, KNO 3 , KSCN, sodium benzoate (NaBen), and sodium salicylate (NaSal)) was studied using tensiometric, viscometric, fluorimetric, and nuclear magnetic resonance (NMR) measurements. Various parameters such as CMC, maximum surface excess ( Г max ), minimum surface area per molecule ( A min ), standard Gibbs free energy of adsorbtion ( Δ G ads o )/micellization ( Δ G m o ), and aggregation number ( N agg ) were calculated. It was observed that the ability to promote surfactant aggregation decreased in the order NaSal > NaBen > KSCN > KNO 3 > KCl. Experiments have shown that the salt counterions exert a strong influence on the CMC, aggregation number, and size and shape of aggregates. 1 H NMR measurements have provided detailed information in context of the action mechanism of the counterions wherein the formation of nonspherical micelles at relatively low surfactant concentrations is deduced. Furthermore, the 1 H NMR studies have been found useful in locating the salt counterions, especially Ben − and Sal − . [ABSTRACT FROM AUTHOR]

Extensive applications of biomacromolecule-surfactant mixtures in cosmetics, industry, agriculture, laundry and biomedical realms have raised environmental and ecological issues. Therefore, scientists now-a-days are concerned to design environmentally benevolent surfactant-protein mixtures which are not only efficient, but ecological too. In this context, we have studied the solution behaviour of hen egg white lysozyme (HEWL) in the presence of two novel biodegradable gemini surfactants by utilizing various spectroscopic and computational methods. The results confirmed the complex formation between Cm-E2O-Cm and HEWL via static mechanism and hydrophobic forces were found to be major contributing forces during interactions. C12-E2O-C12 was found to bind strongly to HEWL than C14-E2O-C14, owing to its smaller size and better penetration efficacy into the hydrophobic domains of HEWL. Upon Cm-E2O-Cm addition, conformational/microenvironmental alterations in HEWL were revealed, respectively, by circular dichroism and pyrene micro-polarity studies. Molecular modeling demonstrates that Cm-E2O-Cm binds in the locality of aromatic residues (Trp/Tyr). This study in future may lend a hand in designing safe and environmentally green surfactant-protein mixtures for their ultimate exploitation in food, laundry, and agriculture prefecture. [ABSTRACT FROM AUTHOR]

Herein, we have examined the interaction of oxy-diester novel twin tailed (gemini) surfactant, 2,2 ′ -[(oxybis(ethane-1,2-diyl))bis(oxy)]bis(N-hexadecyl-N,Ndimethyl-2-oxoethanaminium) dichloride (C 16 -E2O-C 16 ) with hen egg white lysozyme (HEWL), utilizing a spectroscopic and molecular docking techniques. Steady-state fluorescence infers ground state C 16 -E2O-C 16 -HEWL complex formation. Other spectroscopic results validated the conformational, structural and micro-environmental changes in HEWL upon interaction with C 16 -E2O-C 16 . Molecular modeling has shown that C 16 -E2O-C 16 binds in the proximity of hydrophobic moieties (Trp-62/108). We believe the results of the current study will assist in designing the surfactant-enzyme systems for their end use as ingredients in pharmaceutical, cosmetic, drug delivery and industrial compilations. In terms of scientific literature standpoint, it will also enrich and widen the scope of biomacromolecule-surfactant interactions. [ABSTRACT FROM AUTHOR]

Green gemini surfactants (m-E2-m) containing cleavable ester functionalities were allowed to interact with porcine serum albumin (PSA) and the binding mechanism along with concomitant physicochemical changes were analyzed using a multi-technique approach. Intrinsic fluorescence study reveals that the concerned gemini surfactants have a substantial affinity for PSA at a pH well above its isoelectric point. Static quenching is indicated by the relevant value of bimolecular quenching constant (k q ). Synchronous, three-dimensional and pyrene fluorescence data depict the PSA−m-E2-m complex formation together with significant conformational changes induced in PSA. UV–vis studies are also indicative of ground state complexation involving the biomolecule and the amphiphile. Far-UV CD spectra indicate the stabilization of protein structure as deciphered by the increased α-helical content, whereas near-UV CD spectra signify a tertiary structure close to that of the native state. In order to validate the results obtained by fluorescence, cyclic voltammetry is employed, which unveils the formation of electrochemically inactive PSA−m-E2-m complex. Moreover, it is revealed that gemini with longer chain interacts more efficiently than the one with shorter chain owing to stronger hydrophobic forces. All these findings suggest that in future, the m-E2-m geminis may be potentially utilized as excipients in drug, skincare and immunoassay reagent formulations. Furthermore, results of this research work will also contribute in understanding the physicochemical effect of surfactant architecture on its interaction with biomacromolecules. [ABSTRACT FROM AUTHOR]

Binding of surfactants to biomacromolecules is an active field of current interest at the interface of chemical biology and medicinal chemistry, owing to their diverse applications in industries, biomedical and cosmetic domains. In relevance to this, we have investigated the interactions of two distinctly modified green gemini surfactants (C 12 -E2O-C 12 and C 14 -E2O-C 14 ) with the heme protein hemoglobin (Hb) utilizing different state-of-the-art techniques. These surfactants are employed to explicate the effect of structural variation on the conformation of Hb. Complexation between Hb and C 12 -E2O-C 12 /C 14 -E2O-C 14 were found to follow the same 1:1 stoichiometric pattern but with different binding constants (evaluated through fluorescence and electrochemical measurements). The UV–vis spectra showed the influence of C 12 -E2O-C 12 /C 14 -E2O-C 14 on Hb, displaying a strong concentration-dependent fashion. Furthermore, pyrene, synchronous and 3-D fluorescence spectra of Hb depicted the possible alterations induced in its aromatic microenvironment upon C 12 -E2O-C 12 /C 14 -E2O-C 14 complexation. Far-UV CD results revealed nominal changes in the secondary structure of the Hb while a considerable loss in tertiary structure was observed in the near-UV range, elucidating the formation of molten globule state. The best energy-docked structure in the molecular docking analysis revealed that C 12 -E2O-C 12 /C 14 -E2O-C 14 preferred to bind in the hydrophobic cavity of Hb. Thus, this work provides a comprehensive inspection of Hb-C 12 -E2O-C 12 /C 14 -E2O-C 14 interaction at the molecular level that can be extended potentially to other congeners, which is essential in determining their future use as excipients in pharmaceutical formulations and other related applications. [ABSTRACT FROM AUTHOR]

The present work describes strength modulation of carboxymethylcellulose (CMC) hydrogel on addition of biodegradable diester-bonded gemini surfactants. These CMC-surfactant hybrid hydrogels were prepared using carboxymethylcellulose sodium salt and gemini surfactants in urea solution. The structure and morphology of the synthesized hybrid hydrogels were characterised using FT-IR spectroscopy and scanning electron microscopy. The gelling behaviour of synthesized hybrid hydrogels were investigated in distilled water in presence of different salts and differing pH's. The swelling capacity of these hydrogels were found to decrease with an increase in the charge of the metal cation ions (Al 3 + < Ca 2 + < Na + ). The rheometric observations reveal an increase in the elastic modulus (G) of the CMC hydrogel on addition of surfactant, indicating an increase in the mechanical strength of the hydrogel. However, at higher surfactant concentrations the G value progressively decreased. The effect of added surfactants on gelation temperature of CMC was investigated through oscillating temperature sweep. The gelation temperature of CMC-urea + 16-E2-16 surfactant was found to be higher than that of CMC-urea + 14-E2-14 gemini surfactant. The encapsulation capacity of synthesized CMC-urea + surfactant hybrid hydrogel systems were explored for sorption capacity of various hazardous polynuclear aromatic hydrocarbons (PAHs) from their aqueous solutions. The observed results suggest that sorption of PAHs using CMC-urea + surfactant hydrogel systems can be a valuable approach towards safer remediation of groundwater contaminated by toxic organic compounds. [ABSTRACT FROM AUTHOR]

Keeping in mind the contemporary environmental concern raised over the disposal of surfactants into water bodies, we synthesized biodegradable cationic gemini surfactant ethane-1,2-diyl bis( N , N -dimethyl- N -hexadecylammoniumacetoxy) dichloride (16-E2-16), which bears easily cleavable ester functionalities (betaine type arrangement) in its spacer. This research article encompasses an in vitro analysis of the interaction between the synthesized gemini surfactant and a serum transport protein, porcine serum albumin (PSA) under physiological mimetic conditions. A multi-technique approach was exploited to explore the structural alterations induced in PSA at different concentrations of 16-E2-16. Fluorescence measurements unraveled a substantial interaction between PSA and 16-E2-16 (K b ∼ 10 4 M −1 ). Synchronous and three-dimensional fluorescence spectra further validated the binding of 16-E2-16 with PSA. Pyrene emission fluorescence depicted an increased hydrophilicity experienced by the probe molecules on account of their expulsion into the solvent due to a comparatively stronger binding of the gemini surfactant with PSA. The UV–vis studies established the ground state complexation of the gemini with PSA. Interestingly, far-UV CD results demonstrated the stabilization of secondary structure of PSA at concentrations below and above the CMC of 16-E2-16. Near-UV CD spectra revealed negligible changes in the tertiary structure of PSA. Additonally, CV scans depicted electrochemically inactive 16-E2-16−PSA complex formation and thus reinforced the findings of spectroscopic investigations. Overall, it is inferred that 16-E2-16 binds efficiently with PSA affecting both its microenvironment and conformation. Owing to these favorable interactions, 16-E2-16 may find its application as a prospective excipient in drug, skincare and immunoassay reagent formulations, in which serum albumins are frequently used. [ABSTRACT FROM AUTHOR]

Surfactant-protein mixtures have attracted considerable research interest in recent years at the interface of chemical biology and medicinal chemistry. Herein, the interaction between a green gemini surfactant (C 16 -E2O-C 16 ) and a redox protein hemoglobin was examined through a series of in vitro experimental techniques with an attempt to provide a comprehensive knowledge of the surfactant-protein binding interactions. Quantitative appraisal of the fluorescence/CV data showed that the binding of C 16 -E2O-C 16 to Hb leads to the formation of thermodynamically favorable non-covalent adduct with 1:1 stoichiometry. UV–vis spectra demonstrated that the effect of C 16 -E2O-C 16 on Hb is highly concentration dependent. Far-UV and near-UV CD spectra together elucidated the formation of molten globule state of Hb upon C 16 -E2O-C 16 addition. Temperature dependent CD explicated the effect of C 16 -E2O-C 16 on the thermal stability of Hb. Furthermore, the structural investigation of Hb via pyrene/synchronous/three-dimensional fluorescence and FT-IR spectroscopy provided the complementary information related to its microenvironmental and conformational changes. Computational studies delineated that C 16 -E2O-C 16 binds in the vicinity of β-37 Trp at the α 1 β 2 interface of Hb. Overall, this study is expected to clarify the binding mechanism between Hb/other congeners and surfactant at the molecular level that are known to have immense potential in biomedical and industrial areas. [ABSTRACT FROM AUTHOR]

Surfactant–protein/enzyme interactions have gained widespread interest in modern research due to their implications in various domains like pharmaceuticals, cosmetics, paints, biotechnology, etc. Thus, spectroscopic, microscopic and molecular modeling approaches have been employed to explore the interaction of a novel series of oxy-diester hybrid cationic gemini surfactants, 2,2′-[(oxybis(ethane-1,2-diyl))bis(oxy)]bis( N -alkyl- N , N -dimethyl-2-oxoethanaminium) dichloride (C 12 -E2O-C 12 , C 14 -E2O-C 14 and C 16 -E2O-C 16 ), with bovine milk xanthine oxidase (XO). Intrinsic fluorescence studies revealed that the concerned gemini surfactants quenched the XO fluorescence through static quenching mechanism. The trend for K sv values was: C 12 -E2O-C 12 < C 14 -E2O-C 14 < C 16 -E2O-C 16 while the inverse trend was observed for K b values (C 12 -E2O-C 12 > C 14 -E2O-C 14 > C 16 -E2O-C 16 ). Negative Δ G b o values confirmed the spontaneity of C m -E2O-C m + XO interactions. The results of other techniques (viz., pyrene fluorescence, UV, CD and TEM) also indicated that the concerned gemini surfactants induce conformational changes in XO. Moreover, the actual binding site of C m -E2O-C m gemini surfactants into hydrophobic domains of XO was confirmed by molecular docking. This study elucidates the interaction mechanism of high performance gemini surfactants with XO, which in general may be significant to compile the green amphiphilic systems, for industrial and pharmaceutical implications (more specifically to develop chemical entities for prevention and treatment of various diseases like gout, hyperuricemia, etc.). [ABSTRACT FROM AUTHOR]

Interaction of surfactants with biomacromolecules is an essential subject of biophysical chemistry to address their diverse applications in industry, biomedical, and cosmetic domains. In this context, we have examined the binding interactions of three ester-functionalized surfactants (m-E2-m) with bovine liver catalase (BLC, 10 μM) by employing a multi-technique approach. The m-E2-m geminis quench fluorescence intensity of BLC through static procedure. The binding ability of concerned gemini surfactants was found to be in the order 12-E2-12 (K b = 2.3 × 10 2 ) > 16-E2-16 (K b = 1.1 × 10 2 ) > 14-E2-14 (K b = 1.0 × 10 2 ). Quenching efficacy, as determined by K sv values, were observed as 12-E2-12 (3.0 × 10 2 ) > 16-E2-16 (1.4 × 10 2 ) > 14-E2-14 (1.0 × 10 2 ). The negative ΔG° b values (12-E2-12 (−13.48 kJ/mol) > 16-E2-16 (−11.65 kJ/mol) > 14-E2-14 (−11.41 kJ/mol)) indicate spontaneous nature of m-E2-m–BLC interactions. UV–vis spectroscopy, circular dichroism (CD) and micropolarity (F 1 /F 3 ) assessments indicate conformational changes in BLC upon m-E2-m combination. ITC confirms the stability of BLC upon gemini combination. Docking provides support to fluorescence results by presenting the localization site of m-E2-m surfactants near to aromatic residues (mainly Tyr, Trp and Phe). Moreover, since surfactant-protein interactions have essential miscellaneous implications, therefore, this study can be significant for industrial and biomedical realms. [ABSTRACT FROM AUTHOR]

Designing and compilation of novel chemical molecules to optimize the structural characteristics of biomolecules is an interesting and fascinating domain of research at the interface of chemistry and molecular biology. In this context, we have synthesized a green/biocompatible gemini surfactant, ethane-1, 2-diyl bis( N , N -dimethyl- N -hexadecylammoniumacetoxy) dichloride (16-E2-16), and examined its interaction with the model enzyme hen egg white lysozyme (HEWL) utilizing sophisticated spectroscopic, microscopic, calorimetric and molecular modeling techniques. The results obtained through multidimensional approach demonstrate that 16-E2-16 is able to influence the structural aspects of HEWL. The intrinsic fluorescence and UV spectroscopic results reflect HEWL-16-E2-16 complex formation. Synchronous, three-dimensional and pyrene fluorescences show substantial changes in microenviroment around tyrosine and tryptophan residues. CD results demonstrate conformational change in HEWL upon 16-E2-16 combination. ITC suggests the contribution of hydrophobic forces and spontaneous nature of 16-E2-16-HEWL interaction. Molecular modeling confirms the binding of 16-E2-16 gemini surfactant near predominant fluorophores (Trp-62/Trp-108). TEM micrographs infer structural changes in HEWL. This study is thought to have good potential to help scientists to further interpret the surfactant–HEWL interaction at the molecular level, which will be significant to compile surfactant–protein mixtures in general for pharmaceutical and industrial purposes. [ABSTRACT FROM AUTHOR]

Herein we report the interaction of a biodegradable gemini surfactant, ethane-1,2-diyl bis(N,N-dimethyl-N-hexadecylammoniumacetoxy) dichloride (16-E2-16) with bovine milk xanthine oxidase (XO), employing tensiometry, fluorescence spectroscopy, UV spectroscopy, far-UV circular dichroism spectroscopy (CD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and computational molecular modeling. Surface tension results depict substantial changes in the micellar as well as interfacial parameters ( CMC , Π CMC , γ CMC , Γ max , A min , Δ G mic ° and Δ G ads ° ) of 16-E2-16 gemini surfactant upon XO combination, deciphering the interaction of XO with the gemini surfactant. Fluorescence measurements reveal that 16-E2-16 gemini surfactant causes quenching in the xanthine oxidase (XO) fluorescence spectra via static procedure and the values of various evaluated binding parameters ( K SV , K b , k q , Δ G b ° and n ) describe that 16-E2-16 effectively binds to XO. Three dimensional fluorescence, 8-anilino-1-naphthalene sulfonic acid (ANS) binding, F 1 F 3 ratio, UV, CD, FTIR, SEM and TEM results delineate changes in the secondary structure of xanthine oxidase. Molecular docking results provide complement to the steady-state fluorescence findings and support the view that quenching occurs due to non-polar environment experienced by aromatic residues of the enzyme. The results of this study can help scientists to tune the conformation of an enzyme (XO) with biocompatible amphiphilic microstructures, which will help to unfold further understanding in the treatment modes of various diseases like gout, hyperuricemia, liver and brain necrosis. [ABSTRACT FROM AUTHOR]

This paper deals with a comprehensive study of the biodegradability, cleavability, hemolytic activity, and physicochemical properties of an ester-linked gemini surfactant, ethane-1,2-diyl bis( N , N -dimethyl- N -tetradecylammoniumacetoxy) dichloride (14-E2-14), along with the gemini-conventional mixed surfactant systems at different mole fractions of 14-E2-14. Some typical conventional surfactants of different polarities were used in the investigation at 303.15 K in aqueous medium by performing conductometric and tensiometric measurements. The data from both the techniques were used to obtain the critical micelle concentration ( cmc ) of mixed surfactant systems at different mole fractions. The decrease in cmc values indicates nonideality of the binary systems, and also occurrence of mixed micellization. Interaction parameters ( β m and β σ ) along with energetics of mixed micellization were evaluated by using theoretical models suggested by Clint, Rubingh, Rosen, Motomura and Maeda for mixed surfactant systems. Negative values of β indicate an overall attractive force in the mixed state. Also, the excess free energy of mixing has negative values for all the systems. The hydrophilic spacer of the gemini surfactant 14-E2-14 shows strong interaction with the conventional surfactants used as well as with the biological membranes such as human erythrocytes (RBC). [ABSTRACT FROM AUTHOR]

In this study, the solubilization of anthracene and pyrene was investigated in micellar solutions of ethane-1,2-diyl bis( N , N -dimethyl- N -dodecylammoniumacetoxy) dichloride (C 12 H 25 (CH 3 ) 2 N + (CH 2 COOCH 2 ) 2 N + (CH 3 ) 2 C 12 H 25 ·2Cl − , 12-E2-12) and its equimolar binary mixtures of conventional cationic, anionic and nonionic surfactants in water. Critical micelle concentration ( cmc ) and other physicochemical parameters were determined by the surface tension and conductivity measurements at 30 °C. Much lower cmc value was obtained for 12-E2-12 than the corresponding monomeric surfactant dodecyltrimethylammonium chloride (DTAC). Lower experimental cmc than the ideal cmc and the negative interaction parameters imply synergistic interaction between the surfactants in the binary solutions. Order of solubilization capacity of the pure/mixed surfactant micelles, for anthracene and pyrene, are not the same. Among the pure surfactants, Brij 58 has highest and SDBS has least efficiency for dissolution of the solutes. The mixed systems 12-E2-12 + SDS and 12-E2-12 + Brij 58 have highest dissolution power for anthracene and pyrene, respectively. Solubility enhancement was observed for both the solutes in the equivalent binary mixtures of the dicationic gemini 12-E2-12 with the anionic conventional surfactants SDS and SDBS. To determine the toxicity of 12-E2-12 and to quantify its interaction with erythrocytes, we have performed the hemolytic assessment. As regards the hemolytic activity and biodegradability test, 12-E2-12 is less toxic and readily biodegradable. [ABSTRACT FROM AUTHOR]