Cetyl Trimethylammonium Bromide Medium Research Articles

Exploring the Specific Role of Iron Center in the Catalytic Activity of Human Serum Transferrin: CTAB-Induced Conformational Changes and Sequestration by Mixed Micelles.

Conformational changes play a seminal role in modulating the activity of proteins. This concept becomes all the more relevant in the context of metalloproteins, owing to the formation of specific conformation(s) induced by internal perturbations (like a change in pH, ligand binding, or receptor binding), which may carry out the binding and release of the metal ion/ions from the metal binding center of the protein. Herein, we investigated the conformational changes of an iron-binding protein, monoferric human serum transferrin (Fe-hTF), using several spectroscopic approaches. We could reversibly tune the cetyltrimethylammonium bromide (CTAB)-induced conformation of the protein, exploiting the concept of mixed micelles formed by three sequestrating agents: (3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate) hydrate (CHAPS) and two bile salts, namely, sodium cholate (NaC) and sodium deoxycholate (NaDC). The formation of mixed micelles between CTAB and these reagents (CHAPS/NaC/NaDC) results in the sequestration of CTAB molecules from the protein environment and aids the protein in reattaining its native-like structure. However, the guanidinium hydrochloride-induced denatured Fe-hTF did not acquire its native-like structure using these sequestrating agents, which substantiates the exclusive role of mixed micelles in the present study. Apart from this, we found that the conformation of transferrin (adopted in the presence of CTAB) displays pronounced esterase-like activity toward the para-nitrophenyl acetate (PNPA) substrate as compared to native transferrin. We also outlined the impact of the iron center and amino acids surrounding the iron center on the effective catalytic activity in the CTAB medium. We estimated ∼3 times higher specific catalytic efficiency for the iron-depleted Apo-hTF compared to the fully iron-saturated Fe2-hTF in the presence of CTAB.

Interfacial and surface adsorption phenomenon in the dissolution behavior of 8-hydroxy quinoline

The solubilization and dissolution behavior of 8-hydroxyquinoline was studied in surfactant medium. Anionic surfactant - Sodium dodecyl sulphate (SDS), cationic surfactant - cetyltrimethylammonium bromide (CTAB), non-ionic surfactant - Triton X-100 were put to use while performing the work. Meaningful interaction of surfactant with cationic and anionic surfactants were only observed. In either of the surfactant medium, the solubility vs surfactant concentration profile has shown a maximum at around the concentration of the surfactant at which the micellization of the surfactant has begun i.e., cmc or critical micelle concentration was reached. In CTAB medium, the solubility of 8-hydroxyquinoline has shown double maxima, one of which was in the post-micellar region. The acid dissociation constant, binding constant of 8-hydroxyquinoline, Gibb’s free energy of solubilization and the partition coefficient (molar) between the aqueous and micellar aggregate phases were computed. Based on all the observations suitable explanations are extended. From the experimental results, the micelle-(8-HQ) binding constant, partition coefficient and free energy of solubilization was computed to supplement the assertions made.

Comparative solubilization of reactive dyes in single and mixed surfactants

Physicochemical attributes and solubilization of reactive dyes in single and mixed micellar media are elaborated in this study. The enhanced entrapment of reactive dyes was observed in the mixed-micellar media of cationic surfactant, cetyltrimethylammonium bromide (CTAB) and nonionic surfactant, (Triton X-100) as compared to single-micellar media of CTAB. Two reactive dyes viz. Reactive Black 5 (RB) and Reactive Yellow 145 (RY) were used for this interactional study. The solubilization in terms of partition constant (Kc ), partition coefficient (Kx ), binding constant (Kb ), Gibbs free energies (ΔGp and ΔGb ) and the approximate location of dye molecules in the micelles, was assessed by UV–Vis spectroscopy. From the experimental findings, it was concluded that the mixing of CTAB with a nonionic surfactant is recommended to achieve a superior degree of entrapment of dye molecules as compared to the single surfactant. The RB, the magnitude of Kx was 520 × 105 in CTAB media, whereas this value lowered to 195 × 105 in the mixed-micellar system (MMS). A similar trend was observed in RY and the single and MMSs showed respective Kx values of 207 × 105 and 19.7 × 105. The higher negative magnitudes in the case of single surfactant indicated greater partitioning of dyes while the mixed system caused deep penetration of dyes. The lower values of Gibb’s free energies of partition and binding were indicative of greater penetration of dyes within the micelles.

Effect of CTAB and SDS on base hydrolysis of iron(II)-sulphonated and unsulphonated phenyl-1,2,4-triazine complexes - A kinetic and mechanistic study

The effect of cetyl trimethyl ammonium bromide (CTAB) and sodium dodecyl sulphate (SDS) on base hydrolysis of iron(II)-triazine complexes viz., tris((3-(4-phenyl)-2-pyridyl)-5,6-bis(4-phenyl)-1,2,4-triazine)iron(II), Fe(PPDT)32+ and its sulphonated analogue, tris(3-(4-(4-phenylsulphonic acid)-2-pyridyl)-5,6-bis(4-phenyl sulphonic acid)-1,2,4-triazine)iron(II), Fe(PPDTS)37‐ has been studied under pseudo-first order conditions at 25, 35, 45 and 55°C. These reactions are first order with respect to the substrate and hydroxide ion. The rate of base hydrolysis of Fe(PPDT)32+ decreases with the increase in ionic strength in both aqueous and CTAB media whereas the effect is minimal in SDS medium. In the case of Fe(PPDTS)37‐, the opposite is seen i.e., the rate of hydrolysis increases with the increase in ionic strength in both the aqueous and SDS media whereas in CTAB medium it has little effect. Specific rate constants (k2) and activation parameters, Ea, ΔH#, ΔS# and ΔG# have also been evaluated. The results obtained suggest that these reactions occur essentially by the same mechanism in aqueous and micellar media. About 104 times catalysis and 5 times inhibition were noticed in CTAB and SDS media respectively when compared to aqueous medium. The observed catalysis is ascribed to electrostatic and hydrophobic interactions between hydroxide and CTAB ions, whereas the inhibition is attributed to the electrostatic repulsions between hydroxide ion and dodecyl sulphonate anions. Density functional theory (DFT) calculations were found to support the experimental results.

Base hydrolysis of tris(3-(2-pyridyl)-5,6-bis(4-phenyl sulphonic acid)-1,2,4-triazine)iron(II) in aqueous, SDS and CTAB media: kinetic and mechanistic study

The kinetics and mechanism of base hydrolysis of tris(3-(2-pyridyl)-5,6-bis(4-phenyl sulphonic acid)-1,2,4-triazine)iron(II), $${\text{Fe}}({\text{PDTS}})_{3}^{4 - }$$ have been studied in aqueous, sodium dodecyl sulphate (SDS) and cetyltrimethyl ammonium bromide (CTAB) media at 25, 35 and 45 °C under pseudo-first-order conditions, i.e. $$\left[ {\text{OH}^{ - } } \right]$$ ≫ $${\text{Fe}}({\text{PDTS}})_{3}^{4 - }$$ . The reaction is first order each in $${\text{Fe}}({\text{PDTS}})_{3}^{4 - }$$ and hydroxide ion. The rate increases with increasing ionic strength in aqueous and SDS media, whereas this parameter has little effect in CTAB. In SDS medium, the rate-determining step involves the reaction between $$\left[ {\text{OH}^{ - } } \right]$$ and $${\text{Fe}}({\text{PDTS}})_{3}^{4 - }$$ , whereas in CTAB medium, it involves reaction between a neutral ion pair, { $${\text{Fe}}({\text{PDTS}})_{3}^{4 - }$$ ·4CTA+} and $$\left[ {\text{OH}^{ - } } \right]$$ ions. The specific rate constants and thermodynamic parameters (E a, ΔH #, ΔS # and ΔG 35°C # ) have been evaluated in all three media. The near equal values of ΔG 35°C # obtained in aqueous and SDS media suggest that these reactions occur essentially by the same mechanism. Slightly lower ΔG 35°C # values in CTAB medium can be attributed to a higher concentration of reactants in the Stern layer. The reaction is inhibited in SDS medium but catalysed in CTAB. The former can be attributed to the anionic surfactant creating more repellent space between the reactants. Catalysis in CTAB medium is ascribed to electrophilic and hydrophilic interactions between hydroxide ion/substrate with the cationic Stern layer, resulting in increased local concentrations of both reactants.

Effect of CTAB concentration on the properties of graphene nanosheet produced by laser ablation

Effects of the concentration of cetyltrimethylammonium bromide (CTAB) on the properties of graphene nanosheets produced by laser ablation method in CTAB medium have been studied experimentally. The beam of a Q-switched Nd:YAG laser of 1064nm wavelength at 7ns pulse width with 1.5J/cm2 fluence was employed to irradiate the graphite target in different concentration of CTAB. Produced graphene nanosheets were diagnosed by UV–Vis–NIR spectroscopy, FTIR spectrum, X-ray diffraction pattern, transmission electron microscopy, field emission scanning electron microscopy, Raman scattering spectrum and X-ray photoelectron spectroscopy. Results show that CTAB is a very capable ablation medium for producing graphene and there is a critical concentration of CTAB for producing few layers graphene nanosheets.

Persistence and Viability of Lecanicillium lecanii in Chinese Agricultural Soil.

The entomopathogenic fungus L. lecanii has been developed as biopesticides and used widely for biological control of several insects in agricultural practice. Due to the lack of isolation/count methods for L. lecanii in soil, the persistence of this fungus in soil appears to have attracted no attention. A selective medium and count method for L. lecanii in soil based on cetyl trimethyl ammonium bromide (CTAB) was developed, and then the persistence and viability of this fungus in soil were investigated under field conditions between 2012 and 2014. The results showed that the rate of recovery for L. lecanii in soil on the selective CTAB medium was satisfactory. The minimum CFUs for L. lecanii on the selective medium (0.5 g/L CTAB) was about 102 conidia/g soil. The L. lecanii density in soil declined quickly in the first month after inoculation with fungal conidia, kept stable for 6 to 10 months, and then decreased gradually until undetectable. L. lecanii could persist for at least 14 months in the agricultural soil of northern China. The colony growth, conidia yield and germination rate on plates, as well as the median lethal concentration or times (LC50 or LT50) to aphids, mycelium growth in aphids and sporulation on aphids of L. lecanii did not change significantly during the persistence in soil. In general, the count method developed here was a very useful tool for monitoring the dynamics of natural or introduced L. lecanii populations in soil, and the data on the persistence of L. lecanii in soil reported here were helpful for biological control and environmental risk assessment.

Dilute cationic surfactant-assisted synthesis of polyaniline nanotubes and application as reactive support for various noble metal nanocatalysts

Well-defined and individual polyaniline (PANI) nanotubes have been synthesized by the oxidative polymerization of aniline in dilute solution in the presence of low-concentration cationic surfactant cetyltrimethylammonium bromide (CTAB). The role of the surfactant in the formation of the PANI nanostructures was discussed by changing its concentration in the reaction system, and the polymerization processes of low-concentration aniline in the dilute CTAB medium were deduced to explain the formation mechanism of the PANI nanotubes. Furthermore, noble metal (Au, Ag, Pt or Pd) nanoparticles that were supported on the as-synthesized PANI nanotubes have been achieved by utilizing the reactivity of PANI towards noble metal ions. Control over the size of noble metal nanoparticles, typical Au nanoparticles, that were uniformly supported on the surfaces of the PANI nanotubes has been realized by introducing a functional doping acid as the linkage. In addition, PANI nanotube/Au nanoparticle composites were found to serve as effective catalysts to activate the reduction of 4-nitrophenol (4NP) in the presence of NaBH4, and the size effects of the catalyst on the catalytic activity were also investigated.

Spectrophotometric Determination of Trace Hg(II) in Cetyltrimethylammonium Bromide Media

The simple and convenient determination of trace Hg(II) with its 2-mercaptobenzothiazole (MBT) complex in cetyltrimethylammonium bromide (CTAB) media has been studied. The UV-visible spectrum of Hg(II)-MBT complex in CTAB media had a good sensitivity and reproducibility. The Hg(II)-MBT complex in CTAB solution was very stable at pH 10.0 and could be quantitatively complexed if MBT were added to the sample solution more than 10 equivalent of Hg(II). The optimum concentration of CTAB was 0.001%. The calibration curve of Hg(II)-MBT complex with good linearity (<TEX>$R^2$</TEX> = 0.9985) was obtained at the concentration range between <TEX>$1.0{\times}10^-7$</TEX> and <TEX>$1.0{\times}10^-5$</TEX> M in 0.001% CTAB media. The detection limit was <TEX>$3.1{\times}10^-8$</TEX> M (6.2 ng m<TEX>$L^{-1}$</TEX>). Hg(II) in the synthetic samples and in the wastewater of the university's wastewater tank and the industrial wastewater tank could also be determined. Based on the experimental results, this proposed technique could be applied to the simple and convenient determination of trace Hg(II) in real samples.

Conformation of gramicidin-A in CTAB micellar media

Gramicidin A (gA) is a linear pentadecapeptide, which exhibits various conformations depending on the environment. The conformational behavior of gA in spherical and rod-shaped cationic micelles formed by cetyltrimethylammonium bromide (CTAB) surfactant has been studied using circular dichroism (CD) and fluorescence spectroscopy, and a probable structure of gramicidin A in CTAB media has been proposed. A CD study shows that gramicidin A assumes β 6.3 helical structure in cationic spherical as well as rod-shaped CTAB micellar media. Modeling studies show the flexibility of the side chain conformation particularly in tryptophan-9. Study of intrinsic fluorescence of tryptophans in gramicidin A indicates three distinct environments for the four-tryptophan residues in CTAB media.

Spectrophotometric determination of germanium in ores, concentrates, zinc-processing products and related materials with phenylfluorone and cetyltrimethylammonium bromide after separation by iron collection and heptane extraction of germanium tetrachloride

A method for determining ~0.2 μg g or more of germanium in ores, concentrates, zinc-processing products and related materials is described. The sample is decomposed by fusion with sodium peroxide and the cooled melt is dissolved in dilute sulphuric acid. Silica, if > 50 mg, is removed by volatilization with hydrofluoric acid. Germanium is separated from sodium salts by co-precipitation with hydrous ferric oxide, the precipitate is dissolved in 3 M hydrochloric acid and germanium is subsequently separated from iron(III) and other co-precipitated elements by a single heptane extraction of germanium tetrachloride from 9̃.4 M hydrochloric acid. The extract is washed with 12 M hydrochloric acid to remove residual iron(III), then germanium is stripped with water and determined spectrophotometrically with phenylfluorone in a 1.4 M hydrochloric acid−0.002 M cetyltrimethylammonium bromide medium in the presence of ascorbic acid as a reductant for co-extracted chlorine. The apparent molar absorptivity of the complex is 1.71 × 10 4 l.mole −1.mm −1 at 507 nm, the wavelength of maximum absorption. Up to 5 mg of tin(IV), 10 mg of antimony(V) and tungsten(VI) and $ ̃ 50 mg of silica do not interfere. Germanium values are given for some Canadian certified reference ores, concentrates and iron-formation samples and for a metallurgical dust.