Conformational Changes as Driving Force for Phase Recognition: The Case of Laurdan

Area of Science:

• Lipid membrane biophysics
• Fluorescence spectroscopy
• Molecular dynamics simulations

Background:

• Assessing lipid membrane phase is crucial for understanding cellular function.
• Laurdan is a potential fluorescent probe for membrane phase studies.
• Its behavior in solid gel (So) phases needs detailed characterization.

Purpose of the Study:

• To characterize Laurdan's behavior in a dipalmitoylphosphatidylcholine (DPPC) solid gel (So) phase using molecular dynamics simulations.
• To compare Laurdan's conformational dynamics in solid gel versus liquid disordered (Ld) phases.
• To investigate Laurdan's conformational intermixing in different membrane environments.

Main Methods:

• Molecular dynamics simulations of Laurdan in a DPPC (So) lipid membrane.
• Analysis of Laurdan's two distinct conformations (Conf-I and Conf-II).
• Calculation of angle distributions and rotational autocorrelation functions.

Main Results:

• Laurdan exhibits distinct conformations (elongated Conf-I, L-shaped Conf-II) in DPPC (So) phase, opposite to its behavior in Ld phases.
• No intermixing between Laurdan conformations was observed in the DPPC (So) phase.
• Conformational behavior differed significantly between solid gel and fluid membrane environments.

Conclusions:

• Laurdan's conformational dynamics are highly sensitive to lipid membrane phase.
• The distinct behaviors of Laurdan's conformers in different phases can be utilized for phase assessment.
• Molecular dynamics simulations provide valuable insights into probe behavior in lipid membranes.