Dynamical Transitions and Diffusion Mechanism in DODAB Bilayer

Abstract

Dioctadecyldimethylammonium bromide (DODAB), a potential candidate for applications in drug transport or DNA transfection, forms bilayer in aqueous media exhibiting a rich phase behavior. Here, we report the detailed dynamical features of DODAB bilayer in their different phases (coagel, gel and fluid) as studied by neutron scattering techniques. Elastic intensity scans show dynamical transitions at 327 K in the heating and at 311 K and 299 K during cooling cycle. These results are consistent with calorimetric studies, identified as coagel-fluid phase transition during heating, and fluid-gel and gel-coagel phase transitions during cooling. Quasielastic Neutron Scattering (QENS) data analysis showed presence of only localized internal motion in the coagel phase. However, in the gel and fluid phases, two distinct motions appear, namely lateral motion of the DODAB monomers and a faster localized internal motion of the monomers. The lateral motion of the DODAB molecule is described by a continuous diffusion model and is found to be about an order of magnitude slower in the gel phase than in the fluid phase. To gain molecular insights, molecular dynamics simulations of DODAB bilayer have also been carried out and the results are found to be in agreement with the experiment.

Mixed Cationic Surfactant Vesicles in (Dioctadecyldimethylammonium Bromide)/NaCl and (Dioctadecyldimethylammonium Chloride)/NaBr Aqueous Dispersions

“…The reverse of this transition occurs at (thermal hysteresis Δ T m ≈ 13 °C), as also reported in (Feitosa et al, ). This is in accord with Dubey et al (Dubey et al, ), who reported a melting temperature of 54 °C (and 38 °C as reverse temperature) for DODAB at 70 mM. At this concentration, there are no vesicles but extended bilayers (Feitosa et al, ).…”

Modulation of Solvation and Molecular Recognition of a Lipid Bilayer under Dynamical Phase Transition

“…Although the structural aspects of almost all the phases of DODAB are explored in detail, [24,25] the hydration properties of the associated water molecules in the close vicinity of the lipid headgroups is relatively less attended in the literature and is one of the motives of the present study. [7] The study reveals slower rotational diffusion of alkyl chain (5.3 10 10 s À1 ) and higher residence time of hydrogen (6.7 ps) in coagel phase compared to those in gel phase (6.8 10 10 s À1 and 5.2 ps). [16] A recent report employing quasi elastic neutron scattering (QENS) and molecular dynamics (MD) simulation studies explored dynamical transition and diffusion mechanism in DODAB bilayer.…”

“…[1][2][3] Although the bilayer lamellar states are relevant to biomembranes, non-bilayer lipid phases, such as hexagonal and cubic phases may relate to transient event in the biomembranes including fusion, fission and pore-formation. [7][8][9] DODAB is a bilayer forming lipid, which reveals lamellar structure analogous to biological membrane. [7][8][9] DODAB is a bilayer forming lipid, which reveals lamellar structure analogous to biological membrane.…”

“…[12][13][14][15] Thus in vitro studies on DODAB bilayers likely provides in depth understanding of the physical properties of biological membranes. [7,16,19,20] Particularly, thermotropic phase behaviours of the system reveals coagel, subgel, gel and liquid crystalline phases. [7,16,19,20] Particularly, thermotropic phase behaviours of the system reveals coagel, subgel, gel and liquid crystalline phases.…”

Dynamical landscape in DODAB membrane system: MD simulation & neutron scattering studies

“…Quasielastic neutron scattering (QENS) has been employed to study DODAB bilayer in coagel, gel and fluid phases [6] with an aim to probe the dynamical transitions and diffusion mechanisms. It has been found that lateral motion of lipids is frozen in the coagel phase, while it's activated in the gel and fluid phases [6]. QENS spectra in the coagel phase are well described considering only the localised motion of the alkyl chains.…”