Dynamical Transitions and Diffusion Mechanism in DODAB Bilayer

Area of Science:

• Materials Science
• Biophysics
• Physical Chemistry

Background:

• Dioctadecyldimethylammonium bromide (DODAB) is a cationic surfactant forming bilayers with potential in drug delivery and DNA transfection.
• Understanding DODAB bilayer phase behavior and dynamics is crucial for optimizing its applications.

Purpose of the Study:

• To investigate the dynamical features of DODAB bilayers in their coagel, gel, and fluid phases.
• To elucidate the molecular motions governing phase transitions in DODAB systems.

Main Methods:

• Neutron scattering techniques, including elastic intensity scans and quasielastic neutron scattering (QENS).
• Calorimetric studies for phase transition identification.
• Molecular dynamics simulations for complementary molecular insights.

Main Results:

• Dynamical transitions observed at 327 K (heating) and 311 K, 299 K (cooling), correlating with calorimetric phase transitions.
• Coagel phase shows only localized internal motion.
• Gel and fluid phases exhibit both lateral monomer diffusion and faster localized internal motion.
• Lateral diffusion is approximately ten times slower in the gel phase compared to the fluid phase.

Conclusions:

• Neutron scattering and simulations reveal distinct molecular dynamics across DODAB phases.
• The study provides a comprehensive understanding of DODAB bilayer dynamics and phase transitions.
• Findings support DODAB's potential in advanced applications requiring controlled molecular mobility.