A comparative study of the effect of cholesterol on bicelle model membranes using X-band and Q-band EPR spectroscopy

The potential of antifungal peptide Sesquin as natural food preservative

Sesquin is a wide spectrum antimicrobial peptide displaying a remarkable activity on fungi. Contrarily to most antimicrobial peptides, it presents an overall negative charge. In the present study, we elucidate the molecular basis of its mode of action towards biomimetic membranes by NMR and MD experiments. While a specific recognition of phosphatidylethanolamine (PE) might explain its activity in a variety of different organisms (including bacteria), a further interaction with ergosterol accounts for its strong antifungal activity. NMR data reveal a charge gradient along its amide protons allowing the peptide to reach the membrane phosphate groups despite its negative charge. Subsequently, the peptide gets structured inside the bilayer, reducing its order. MD simulations predict that its activity is retained in conditions commonly used for food preservation: low temperatures, high pressure, or the presence of electric field pulses, making Sesquin a good candidate as food preservative.

Crystallization of membrane proteins in bicelles

The structural biology of membrane proteins remains a challenging field, partly due to the difficulty in obtaining high-quality crystals. We developed the bicelle method as a tool to aid with the production of membrane protein crystals. Bicelles are bilayer discs that are formed by a mixture of a detergent and a lipid. They combine the ease of use of detergents with the benefits of a lipidic medium. Bicelles maintain membrane proteins in a bilayer milieu, which is more similar to their native environment than detergent micelles. At the same time, bicelles are liquid at certain temperatures and they can be integrated into standard crystallization techniques without the need for specialized equipment.