Spontaneous vesicles, disks, threadlike and spherical micelles found in the solubilization of DMPC liposomes by the detergent DTAC.

The spontaneous colloidal nanostructures formed in water by the zwitterionic phospholipid DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine) with the cationic detergent DTAC (n-dodecyltrimethylammonium chloride) were investigated at a fixed DMPC concentration and variable detergent:lipid total molar ratios (D:L). Apparent (neutral-sphere-equivalent) hydrodynamic diameters (Φ(e)) of liposomes and micelles were obtained by dynamic light scattering (DLS). Fluorescence lifetime imaging microscopy (FLIM), using chlorophyll-a as a probe, showed the morphology of giant vesicles and threadlike micelles.

Time evolution of the thermotropic behavior of spontaneous liposomes and disks of the DMPC-DTAC aqueous system.

In this work, solubilization of the phospholipid 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) by the cationic detergent n-dodecyltrimethylammonium chloride (DTAC) was studied in aqueous solution, at a fixed DMPC concentration and variable detergent:lipid (D:L) molar ratios. The colloidal nanostructures present in different stages of the solubilization process were characterized using micro-differential scanning calorimetry (DSC) and dynamic light scattering (DLS) techniques. For total (analytical) D:L molar ratios below approximately 1, DTAC monomers incorporate into the DMPC liposome bilayers, forming smaller and more fluid vesicles than pure DMPC liposomes.

Unfolding kinetics of beta-lactoglobulin induced by surfactant and denaturant: a stopped-flow/fluorescence study.

The beta-->alpha transition of beta-lactoglobulin, a globular protein abundant in the milk of several mammals, is investigated in this work. This transition, induced by the cationic surfactant dodecyltrimethylammonium chloride (DTAC), is accompanied by partial unfolding of the protein. In this work, unfolding of bovine beta-lactoglobulin in DTAC is compared with its unfolding induced by the chemical denaturant guanidine hydrochloride (GnHCl).

Conformational transitions in beta-lactoglobulin induced by cationic amphiphiles: equilibrium studies.

The conformational transition from the native state in water ("beta-state") to a state containing a considerable amount of alpha-helices ("alpha-state") was studied for the protein beta-lactoglobulin (BLG), from bovine milk, in several colloidal solutions containing mixed micelles or spontaneous vesicles. These aggregates were formed in the bicationic system containing the surfactant dodecyltrimethylammonium chloride (DTAC) and the lipid didodecyldimethylammonium bromide (DDAB). The beta-->alpha transition in BLG, investigated by far-ultraviolet circular dichroism spectroscopy, is induced to the same protein alpha-state by pure and mixed DDAB/DTAC micelles or vesicles.