Lipid-polypeptide interactions in bilayer lipid membranes.

Area of Science:

• Biophysics
• Membrane Biophysics
• Biochemistry

Background:

• Bilayer lipid membranes (BLMs) are fundamental models for biological membranes.
• Understanding how external molecules interact with and modify membrane properties is crucial.

Purpose of the Study:

• To investigate the electrical property modifications of cholesterol-based BLMs interacting with charged polypeptides.
• To elucidate the mechanisms and conditions influencing these interactions.

Main Methods:

• Studied anionic and cationic cholesterol-based BLMs.
• Introduced charged polypeptides (polylysine, polyglutamic acid) and other agents (RNA, trypsin) to BLMs.
• Measured changes in specific membrane conductance and transmembrane potential.
• Varied ionic strength and pH of the bathing medium.

Main Results:

• Polylysine addition to anionic BLMs caused over 1000-fold conductance increase and a cationic potential (>50 mV).
• Polyglutamic acid addition to cationic BLMs increased conductance and induced an anionic potential.
• These effects were reversed by counter-ions, trypsin, increased ionic strength, or high pH (>11.5).
• Neutral BLMs showed no significant changes upon polypeptide addition.

Conclusions:

• The interactions are predominantly electrostatic, leading to the formation of lipid-polymer membranes.
• The observed phenomena provide insights into current models of membrane structure and function.
• Modulation of membrane electrical properties by charged polymers has potential implications for biomimetic systems.