Structural Plasticity of EAK-16 Peptide Inducing Vesicle Membrane Leakage

Background: Ionic complementary peptide EAK-16 has been studies for anticancer drug delivery application. This is a 16 residues, short sequence peptide has ability to trosnform into micro/nanoparticle via self-assembly. However, it is still not clear that how this can bind with cell membrane to induce membrane leakage or delivering their cargo inside cell membrane. Objective: The main objective of this work was to understand behaviour of secondary structure conformation of peptide in solution and at lipid membrane interfaces and membrane permeability of synthetic ionic complementary peptide EAK-16. The corresponding secondary structure conformation was evaluated. Methods: We performed biophysical investigation to probe the interaction of synthesised ionic complementary peptide (EAK-16) with dimyristoylphospholcholine (DMPC) and dimyristoylphosphoserine (DMPS) membrane interfaces. The folding behaviours of EAK-16 were studied with Circular Dichroism (CD) spectroscopy. Membrane leakage with peptide was confirmed with calcein leakage assay. Results: Our finding of this study showed that in aqueous phase EAK-16 was predominantly folded into β-sheets. The temperature could alter the β-sheets. However, in DMPC and DMPS membrane interfaces, EAK-16 adopted helical conformation. EAK-16 has preference in perturbing anionic compared Zwitterionic lipid vesicles. This study proposed that hydrophobic grooves of EAK-16 might be a key in the association with lipid bilayers. Secondly, a charge distribution of ionic residues would also support the orientation at lipid bilayers. This peptide membrane association would facilitate the membrane destabilisation. Conclusion: This study demonstrated the supporting evidence that EAK-16 could interact with lipid membranes and conforming to helical structure, while the helical conformation induced the lipid membrane leakage. Overall, this study provides a physical rationale that ionic complementary peptide can be a useful tool for designing and development of novel antibiotics and anticancer agents along its previous drug delivery applications.

The Relationship Between Post-harvest Storage Conditions and Membrane Leakage in the Context of Blackheart in Potato Tubers

The relationship between potato (Solanum tuberosumL.) tuber membrane permeability and storage conditions were examined. Tubers from four potato cultivars were stored for 1 year at 2 °C and4 °C, and tubers transferred from 4 °C to 2 °C for 48 hours. Electrolyte conductivity measurements taken from two discs of four potato cultivars with six biological replicates as well as different tissues types including the pith, cortex and parenchyma. The results showed that the longer the storage time and lower the temperature, the higher the electrolyte conductivity of the tissues. And different tissue types pith, cortex and parenchyma had different electrolyte conductivity susceptibility pattern under different storage conditions. Overall, the parenchyma has highest electrolyte leakage and following are pith, cortex has lowest among three different tissue types. However, cultivars that are resistant to Blackheart, surprisingly had higher electrolyte conductivity compared to the Blackheart-susceptible cultivars. Overall, the work demonstrates that storage conditions have a significant effect on membrane leakage but that this doesn’t appear to relate directly to susceptibility to Blackheart.

Cholesterol suppresses membrane leakage by decreasing water penetrability

In silico simulations and biochemical experiments show that cholesterol decreases water penetrability to inhibit leakage pore formation during membrane fusion.