Studies of interaction between ninhydrin and Gly-Leu dipeptide: Influence of cationic surfactants (m-s-m type Gemini)

Phase separation, aggregation, and complexation of triton-X100 and bovine serum albumin mixture: A combined cloud point and UV-visible spectroscopic approaches

Phase separation and aggregation behaviour of triton X-100 (TX-100) and bovine serum albumin (BSA) mixture were investigated using cloud point and UV-visible spectroscopic techniques. The effects of various hydrotropes (HYTs) - namely, sodium salicylate (SS), sodium benzoate (SB), glycerol (Glyc), and 4-aminobenzoic acid (4-ABA) - on the cloud point (CP) of TX-100 + BSA were determined. The obtained CP values for the mixed system in the presence of HYTs followed the order: The measured critical micellization concentration (CMC) values of the TX-100 + BSA mixture were found to be significantly altered with varying amounts of BSA. The calculated free energy of clouding and micellization indicated the non-spontaneous nature of the phase transition and the spontaneous association of the TX-100 + BSA mixture. The non-spontaneity of phase separation decreased with increasing concentrations of HYTs. The enumerated values of ∆Hco and ∆Sco were consistently recorded as negative and positive magnitudes, respectively, in all aqueous HYTs media. The clouding process occurred due to a combination of hydrophobic and electrostatic interactions. The binding constant of the mixed system was determined employing the UV-vis spectroscopic method using the Benesi-Hildebrand equation.

Insights into the Characterization of the Self-Assembly of Different Types of Amphiphilic Molecules Using Dynamic Light Scattering

The self-assembly of cetyltrimethylammonium bromide, sodium dodecylsulfate, Triton X-100, and sulfobetaine surfactants in aqueous solutions was examined by dynamic light scattering, both in the presence and absence of 0.1 M NaCl salt, across various temperatures. For each surfactant, critical parameters, such as concentration and phase transition temperatures, of micelles were determined by monitoring changes in the hydrodynamic diameter with concentration and temperature. Additionally, we explored the self-assembly behavior of these surfactants when they are introduced alongside polystyrene nanoparticles. Our findings enabled the elucidation of surfactant molecule adsorption mechanisms onto polystyrene nanoparticle surfaces. Furthermore, by analyzing variations in the z-average diameter and zeta potential, we were able to establish the Krafft point, a parameter that remains imperceptible when polystyrene nanoparticles are absent from the solution.

Influence of twin-headed gemini micellar system on the study of methionine amino acid with ninhydrin in buffer solution

The influence of double-headed gemini was examined in the present study by studying the amino acid methionine mixed with ninhydrin in CH₃COOH-CH₃COONa buffer solvent. The absorbance was monitored at fixed time intervals with UV-vis spectroscopy. An impact typical of surfactants was observed on the ninhydrin-methionine reaction and explained by a pseudo-phase model of micelles. The effect of different temperatures (343 to 363 K) was also determined. Based on data showing the impact of temperature on k_ψ , several relevant thermodynamic quantities, ΔH ^#, ΔS ^#, and E _a, were calculated using linear least-squares regression. In addition, the influence of the other reaction ingredients on the reaction, that is, pH and the concentration of ninhydrin and methionine, was studied. The CMC (critical micelle concentration) of pure geminis and the surfactant system with methionine and ninhydrin was evaluated at two temperatures, i.e. at 303 K and 353 K by conductivity measurements. The CMC values of pure gemini surfactants evaluated in the existing case at 303 K are concordant with the results stated before. Moreover, other parameters, including rates and binding constants, were calculated.

Physicochemical Studies on the Interaction between Sodium Dodecyl Sulfate and Methylene Blue in Methanol-Water Mixed Solvent Media

The surface activity and the process of micellization of sodium dodecyl sulfate (SDS) with methylene blue (MB) in a methanol-water mixed solvent system were investigated by tensiometry and conductometry at 298.15 K. The measurements of surface tension and conductivity of SDS-MB complex were carried up to 0.3 volume fractions of methanol because the resulting complex appeared turbid above 0.3 volume fractions of methanol. The critical micelle concentration (CMC) of the SDS was determined from both tensiometry and conductometry. The CMC of SDS increased with the increasing volume fraction of methanol due to the inclusion of methanol in the micelles and decreased in the presence of methylene blue due to the reduction of electrostatic repulsion within the anionic moiety of SDS by the positive charge of the added dye. Different properties like surface excess concentration $\left({\mathrm{\Gamma }}_{\max }\right)$ , minimum surface area $\left(A_{\text{min}}\right)$ , Gibbs free energy of micellization $\left(\mathrm{\Delta }{G}_{\mathrm{m}}^o\right)$ , surface pressure ( ${\pi }_{\text{CMC}}$ ), efficiency of a surfactant ( $\text{p}{C}_{20}$ ), packing parameter $\left(P\right)$ , and standard free energy interfacial adsorption $\left(\mathrm{\Delta }{G}_{\text{ads}}^o\right)$ of SDS in the absence/presence of MB were calculated. On the basis of $\mathrm{\Delta }{G}_{\mathrm{m}}^o$ values, it was noticed that the increasing volume fraction of methanol disfavors the micellization of SDS, while the presence of MB increased the efficiency of SDS making the micellization process more spontaneous.

Study of Methionine and Cumene Hydroperoxide Reaction Kinetics in the Presence of Nonionic Surfactant

The kinetics of the reaction methionine+cumene hydroperoxide in the presence of nonionic surfactant was studied both in the pre-micellar and post-micellar regions at different temperatures by iodometry. It was established that the rate of the methionine + cumene hydroperoxide reaction depends on the molecular/ionic/micellar form of surfactant in the reaction system. In the post-micellar region the rate of methionine+cumene hydroperoxide reaction slows down due to solubilization of the reacting substances in the micelles. Quantification of solubilization of cumene hydroperoxide and methionine in the micelles has been studied by HPLC analysis. It was obtained that about 30% of cumene hydroperoxide, which is more hydrophobic than methionine, is solubilized in the micelles, as a result the concentration of cumene hydroperoxide in the reaction environment decreases and the rate of reaction in the post-micellar region also decreases. Based on the kinetic studies the reaction rate constant was determined and the value of activation energy was obtained.

A Comparative Spectral Study on the Interaction of Organic Dye Congo-Red with Selective Aqueous Micellar Media of CPC, Rhamnolipids and Saponin

The present study is an investigation of the solubilising ability of natural and conventional surfactants saponin (sapindus saponin or reetha saponin), Rhamnolipids (RLs) and N-cetylpyridinium chloride (CPC) respectively via dye-surfactant interaction. The ionic dye Congo Red was examined by absorption spectroscopy method for the study. The dye interacted strongly with oppositely charged surfactant N-cetylpyridinium chloride in the pre-micellar concentration range and formed a stable dye-surfactant complex. The thermodynamic parameter, free energy change for all the systems was calculated at a constant temperature of 25°C. The ΔG0 value for N-cetylpyridinium chloride is found to be −33.269 kJ/mol while for saponin and rhamnolipids the values were −16.084 kJ/mol and −26.006 kJ/mol respectively. The values clearly indicate the efficiency of N-cetylpyridinium chloride surfactant compared to the other two surfactants. The present study aims to understand the dye solubilization in surfactant media in order to develop environmentally friendly, green and cost effective techniques.

Synthesis and characterization of geminis and implications of their micellar solution on ninhydrin and metal amino acid complex

In our study, three gemini dicationic surfactants with different methylene group spacer (16-6-16, 16-5-16 and 16-4-16) have been synthesized and characterized in solution by 1H NMR spectroscopic technique. The implications of gemini micellar solution on ninhydrin and metal amino acid complex ([Cu(II)-Trp]+) were performed by the means of single-beam UV-visible spectroscopy. The absorbance was noted at regular time intervals and values of rate constant (kψ ) were determined by using a computer-based program. Synthesized surfactants proved as an efficient catalyst on the interaction of ninhydrin with metal amino acid complex as compared with conventional surfactant and aqueous systems. The required description regarding the implications of gemini dicationic surfactants are provided in the text in detail. The conductivity technique was applied in order to get critical micelle concentration (cmc) of geminis in the presence and absence of reactants. Catalytic results developed in gemini dicationic surfactant system were explained effectively by pseudo-phase model. Various thermodynamic quantities, viz., activation energy, E a, activation enthalpy, ΔH #, and activation entropy, ΔS #, were obtained on interaction of ninhydrin with [Cu(II)-Trp]+ in gemini systems by applying Eyring equation. A detailed explanation about these evaluated parameters was also made.

Kinetic study of the metal-dipeptide complex with ninhydrin facilitated by gemini (m-s-m) surfactant micelles

The three Gemini (m-s-m; m (head group) = 16 and s (spacer) = 4, 5, 6) surfactants have been synthesized and their impact on reaction of zinc(II)-glycylleucine complex ([Zn(II)-Gly-Leu]⁺) and ninhydrin were studied at temperature (343 K) and pH (5.0) using spectroscopic method. Influence of several factors, viz., [Zn(II)-Gly-Leu]⁺, [ninhydrin], temperature and pH were also carried out on title reaction in geminis. Rates of reaction are the first-order path in concentration of [Zn(II)-Gly-Leu]⁺ complex and fractional order path in concentration of ninhydrin. The catalysis of gemini 16-s-16 surfactant micelles was investigated below and above their critical micelle concentration (cmc) value and detailed elaboration were provided in the text. In the present case, rate constants, k_ψ, increased on increasing geminis ([gemini] are below their cmc, region I) and stayed nearly constant (region II). The shape of (region I and II) surfactants ([gemini] = 0 to 400 × 10^-5 mol dm^-3) are similar to a cetyltrimethylammonium bromide, CTAB (single hydrophilic head group and hydrophobic part). Later, a sharp increment in rate was observed with higher [gemini] (region III, (Fig. 5). The study was catalyzed and accelerated quite enough by geminis (at concentrations below their cmc) compared to aqueous. An appropriate mechanism has been proposed for accounting for the distribution of reactants between aqueous and micellar pseudo phases. Resulting kinetic data were used to determine the binding constants of micelle-substrate (K_B) and micelle-ninhydrin (K_Nin).

Catalytic influence of 16-s-16 gemini surfactants on the rate constant of histidine and ninhydrin

The present paper reports the catalytic influence of 16-s-16 (spacer (s) = 4, 5, 6) gemini surfactants on the rate constant of histidine and ninhydrin at 343 K and pH 5.0 using the spectrophotometric technique. The effect of varying amounts of geminis was made on the rate constant of histidine and ninhydrin keeping other constituents constant. Characteristics of the rate constant (kψ ) versus [gemini] depict the effect of surfactants on the rate constant. A systematic explanation about the effect of surfactants is revealed and discussed in the text. The influence of different parameters that includes [reactants], temperature and pH has also been performed on the study. In order to determine the critical micelle concentration (cmc) of pure surfactants and their solution mixtures, conductivity measurement was employed. By using the Eyring equation, activation parameters at different temperatures have been obtained. The resultant data of kψ versus [gemini] plot were rationalized with the pseudo-phase model of micelles.