Thermodynamics, size, and dynamics of zwitterionic dodecylphosphocholine and anionic sodium dodecyl sulfate mixed micelles

Abstract

The thermodynamic properties of micellization for dodecylphosphocholine (DPC), sodium dodecyl sulfate (SDS), and their mixtures were studied using isothermal titration calorimetry. NMR relaxation measurements were used to explore molecular mobility of the DPC-containing micelles, whereas the diffusion measurements were taken to determine the micelle size. The DPC/SDS mixed systems reveal a tendency to form two kinds of micelles in buffered solution at lower temperatures. An increase in temperature as well as the transfer of the DPC/SDS mixed micelles from buffered to unbuffered solution results in only a single-step micellization process. The average size of the DPC-containing micelles is only slightly dependent on the SDS fraction. Examination of the data of spin-spin relaxation (T 2 ) shows that methylene protons on the polar headgroup of DPC and methylene protons (H1) on the hydrocarbon chain in the micellar systems studied reveal a heterogeneous dynamic behavior reflected in a twocomponent T 2 relaxation in the whole temperature range. The latter is the main constituent of the rigid interfacial layer core protecting the penetration of water into the hydrophobic interior.

Aggregation behavior of Triton X-114 and Tween 80 at various temperatures and concentrations studied by density and viscosity measurements

“…On the a = f(log C) curves for TX114 and Tween 80 at T = 293 K, there are two break points-the first corresponds to the values of CMC determined from the surface tension measurements and the second is close to C = 10 -3 M. This suggests the existence of the second value of CMC of TX114 and Tween 80 in which the micelle structure changes and/or admicelles are changed into micelles [28]. It is known that amphiphilic molecules generally form spherical aggregates in aqueous solutions above the CMC, but, under certain conditions these spherical micelles grow in size or change their shape resulting in the formation of rodlike structures or even long flexible micelles [29][30][31][32][33]. It is interesting that for both surfactants at T = 293 K, the values of a decrease up to that of the first CMC, then they are almost constant at C between the first and second CMC and next grow up, especially for Tween 80.…”

Structure determination of UL49.5 transmembrane protein from bovine herpesvirus 1 by NMR spectroscopy and molecular dynamics

“…For the peptide bond with P66 residue, the NOE signal of αH G65 -δH P66 , confirmed the presence of a trans peptide bond geometry. In 100 mM DPC-d 38 , the NOESY (Fig. 5S) spectrum of TMC.BHV showed 344 NOE connectives including 2 long-range, 125 intraresidue, 133 sequential, and 84 medium-range effect.…”

“…The peptide concentration was 4.8 mM (N.BHV) and 2.7 mM (TMC.BHV). The DPC-d 38 :peptide ratio was kept approximately to 40:1, and the pH was adjusted to 5.0 [24]. To improve the micelle formation and the binding of the synthesized peptide to the DPC micelle as well as the homogeneity of this complex, each sample was sonicated for 10 min at room temperature.…”

“…The starting coordinates of the DPC micelle-water system were taken from simulations conducted by Tieleman et al [36]. A single molecule of DPC was constructed on the basis of previously published parameters [37,38]. The pre-built hydrated DPC micelle consisted of 65 DPC monomers and 6305 water molecules.…”

Clear distinction between CAC and CMC revealed by high-resolution NMR diffusometry for a series of bis-imidazolium gemini surfactants in aqueous solutions

“…2,3 Accordingly, because considerably lower concentrations can be applied, gemini surfactants are proposed to be better for technological and biological purposes such as cosmetics formulations, oil recovery, detergency, nanotechnology, catalysis as well as drug delivery. [4][5][6][7][8][9][10][11][12][13][14][15] The last one, namely, the drug delivery is of special concern. It involves the application of the micellar solutions, vesicles or lyotropic liquid crystals solutions as colloidal drug carrier systems.…”