Interaction Of Dodecyltrimethylammonium Bromide Research Articles

Molecular dynamics simulation studies on the concentration-dependent interaction of dodecyltrimethylammonium bromide with curcumin

Curcumin, a natural dietary polyphenol extracted from the roots of the plant Curcumin longa, possesses diverse therapeutic effects. The poor water solubility and instability of curcumin can be improved by encapsulation in surfactant micelles. In this paper, the interaction between curcumin and dodecyltrimethylammonium bromide (DTAB) in aqueous solution was studied by molecular dynamics simulation. Three systems were established by changing the number of added DTAB molecules to explore the interaction mode between curcumin and DTAB in different aggregation states. Distance distribution, number density distribution, electrostatic potential distribution and decomposition of energy were used to clarify binding structures and interaction mechanism. Before forming micelles, changes in the concentration of DTAB resulted in the formation of two different aggregation states, namely monomer and pre-micelle state. DTAB of two different aggregation states interacted with curcumin through electrostatic and hydrophobic interactions, respectively. When the surfactant concentration was above the critical micelle concentration (cmc), curcumin was solubilized into the micelle and located at the palisade layer as expected. The dynamic simulation results can provide a theoretical basis for experimental research and explain the interaction mode between them at the microscopic level. This will provide guidance for the use of surfactants in pharmaceutical formulations.

Interaction of cationic dodecyl-trimethyl-ammonium bromide with oxy-HbGp by isothermal titration and differential scanning calorimetric studies: Effect of proximity of isoelectric point.

In this work, isothermal titration and differential scanning calorimetric methods, in combination with pyrene fluorescence emission and dynamic light scattering have been used to investigate the interaction of dodecyltrimethylammonium bromide (DTAB) with the giant extracellular Glossoscolex paulistus hemoglobin (HbGp) in the oxy-form, at pH values around the isoelectric point (pI ≈ 5.5). Our ITC results have shown that the interaction of DTAB with the hemoglobin is more intense at pH 7.0, with a smaller cac (critical aggregation concentration) value. The increase of protein concentration does not influence the cac value of the interaction, at both pH values. Therefore, the beginning of the DTAB-oxy-HbGp premicellar aggregates formation, in the cac region, is not affected by the increase of protein concentration. HSDSC studies show higher Tm values at pH 5.0, in the absence and presence of DTAB, when compared with pH 7.0. Furthermore, at pH 7.0, an aggregation process is observed with DTAB in the range from 0.75 to 1.5 mmol/L, noticed by the exothermic peak, and similar to that observed for pure oxy-HbGp, at pH 5.0, and in the presence of DTAB. DLS melting curves show a decrease on the hemoglobin thermal stability for the oxy-HbGp-DTAB mixtures and formation of larger aggregates, at pH 7.0. Our present data, together with previous results, support the observation that the protein structural changes, at pH 7.0, occur at smaller DTAB concentrations, as compared with pH 5.0, due to the acidic pI of protein that favors the oxy-HbGp-cationic surfactant interaction at neutral pH.

Conductometric and fluorescence probe investigations of molecular interactions between dodecyltrimethylammonium bromide and dipeptides

The effect of five dipeptides (glycylglycine, glycyl-l-valine, glycyl-l-leucine, glycyl-l-glutamine, and l-alanyl-l-glutamine) on the micellar properties of catonic surfactant dodecyltrimethylammonium bromide (DTAB) has been investigated by electrical conductivity and fluorescence spectroscopy. From the conductivity data, the critical micellar concentration (c cmc), counterion binding constant (β), and thermodynamic parameters of micellization (ΔG m o , ΔH m o and ΔS m o ) have been calculated. The effect of dipeptides on the micellar properties of DTAB depends upon their nature and concentration as well as on temperature and has been used to study the interactions present in the micellar systems. Enthalpy–entropy compensation effect has also been observed. The pyrene fluorescence spectra were used as an index for the estimation of micropolarity of micellar produced by the interaction of DTAB with dipeptides and the aggregation behavior of DTAB. Comparison on the interactions between different types of surfactants and dipeptide showed that the order of the strength for these interactions is TX-100 < DTAB < SAS < SDS.

Spectrometric Study on the Interaction of Dodecyltrimethylammonium Bromide with Curcumin

The interaction between dodecyltrimethylammonium bromide (DTAB) and curcumin has been studied in pH 5.0 sodium phosphate buffer using absorption and fluorescence measurements. With increasing DTAB concentration (C(DTAB)) from 0 to 20 mM, the absorption peak of curcumin at 430 nm, corresponding to the conjugated structure of curcumin, first weakens gradually into a shoulder but increases back into one peak with much higher absorption intensity. On the contrary, as C(DTAB) increases, the initial small absorption shoulder of curcumin at 355 nm, corresponding to the feruloyl unit of curcumin, first increases gradually into a clear peak but decreases back into one shoulder until almost disappeared finally. By remaining at nearly the same wavelength, the fluorescence of curcumin first decreases at C(DTAB) lower than 5 mM and then increases gradually up to C(DTAB) = 10 mM, which is followed by sharp increases of fluorescence intensity with marked blue-shifts at higher C(DTAB). The values of anisotropy and microviscosity of curcumin obtained from the fluorescence polarization technique also showed pronounced changes at different surfactant concentrations. The interaction mechanisms of DTAB with curcumin have been presented at low, intermediate, and high surfactant concentrations, which is relating to interaction forces, surfactant aggregations, as well as structural alterations of curcumin.

The interaction between hemoglobin and two surfactants with different charges

The interactions of hemoglobin (Hb) with sodium dodecyl sulfate (SDS) and dodecyl trimethylammonium bromide (DTAB) are investigated by several methods. We observed the formation of hemichrome below the critical micelle concentration (cmc) of surfactant and the release of heme from Hb above the cmc. When pH value of Hb/surfactant system is lower than isoelectric point (p I) of Hb, the interaction of SDS with Hb is both electrostatic and hydrophobic, while the interaction of DTAB with Hb is hydrophobic mainly. On the contrary, when pH > p I, the interaction of SDS with Hb is hydrophobic mainly, while the interaction of DTAB with Hb is both electrostatic and hydrophobic. In the case where both the electrostatic interaction and hydrophobic interaction exist, the electrostatic interaction plays a more important role. Thus, SDS tends to interact with Hb more obviously than DTAB does when pH < p I and the interaction between DTAB and Hb is stronger when pH > p I.

Potentiometric Study on Interaction of Dodecyltrimethylammonium Bromide with α-Amylase

Abstract The binding of dodecyltrimethylammonium bromide (DTAB) with α-amylase was investigated under various experimental conditions, such as pH, ionic strength, urea and protein concentration at 25 °C using surfactant membrane-selective electrodes as a fast and accurate method. The obtained binding isotherms have been analyzed and interpreted using the Wyman binding potential concept. The results represent: a) the self aggregation of protein that occurs at enzyme concentrations of more than 1 mg/mL (this observation was also confirmed by light-scattering measurements), b) the binding affinity at 10−3 M NaBr is more than other salt concentrations, and c) in the concentration range of 3 to 5 M of urea a predominant unfolding of protein occurs.

A microcalorimetry and binding study on interaction of dodecyl trimethylammonium bromide with wigeon hemoglobin

The thermodynamic parameters for the binding of dodecyl trimethylammonium bromide (DTAB) with wigeon hemoglobin (Hb) in aqueous solution at various pH and 27 °C have been measured by equilibrium dialysis and titration microcalorimetry techniques. The Scatchard plots represent unusual features at neutral and alkaline pH and specific binding at acidic pH. This leads us to analyze the binding data by fitting the data to the Hill equation for multiclasses of binding sites. The best fit was obtained with the equation for one class at acidic pH and two classes at neutral and alkaline pH. The thermodynamic analysis of the binding process shows that the strength of binding at neutral pH is more than these at other pH values. This can be related to the more accessible hydrophobic surface area of wigeon hemoglobin at this pH. The endothermic enthalpy data which was measured by microcalorimetry confirms the binding data analysis and represents the more regular and stable structure of wigeon hemoglobin at neutral pH.

Energetic and binding properties of DNA upon interaction with dodecyl trimethylammonium bromide.

The interaction of dodecyl trimethylammonium bromide (DTAB), a cationic surfactant, with calf thymus DNA has been studied by various methods, including potentiometric technique using DTAB-selective plastic membrane electrode at 27 and 37 degreesC, isothermal titration microcalorimetry and UV spectrophotometry at 27 degreesC using 0.05 M Tris buffer and 0.01 M NaCl at pH 7.4. The free energy is calculated from binding isotherms on the basis of Wyman binding potential theory and the enthalpy of binding according to van't Hoff relation. The enthalpy of unfolding has been determined by subtraction of the enthalpy of binding from the microcalorimetric enthalpy. The results show that, after the interaction of first DTAB molecule to DNA (base molarity) through the electrostatic interaction, the second DTAB molecule also binds to DNA through electrostatic interaction. At this stage, the predom-inant DNA conformational change occurs. Afterwards up to 20 DTAB molecules, below the critical micelle concentration of DTAB, bind through hydrophobic interactions.

Studies on Interaction of Dodecyltrimethylammonium Bromide with Na- and Al-Montmorillonite

The adsorption isotherms and adsorption enthalpies of dodecyltrimethylammonium bromide (DDTMAB) on Na- and Al-montmorillonite were determined in the pH range 2–12. The basal spacings of the clays were also studied by X-ray diffraction. Interactions of DDTMAB with the two montmorillonites predominate mostly through cation exchange in the pH range studied. In the case of Na-montmorillonite, the amount of adsorption increases with pH, but adsorption enthalpy decreases with pH. For Al-montmorillonite, adsorption enthalpy exhibits nonmonotonic variation with pH, although the amount of adsorption increases with pH monotonously. The adsorption enthalpies of DDTMAB on the clays are negative. The adsorbed DDTMAB molecules in clay interlayers present a bilayer arrangement at saturation.