Crown ether helical peptides are preferentially inserted in lipid bilayers as a transmembrane ion channels

Oriented circular dichroism was used to study the alignment crown ether-modified peptides. The influence of different N- and C-functionalities was assessed using at variable peptide:lipid ratios from 1:20 to 1:200. Neither the functionalities nor the concentration had any major effect on the orientation. The alignment of the 21-mer peptides was also examined with lipid membranes of different bilayer thickness. The use of synchrotron radiation as light source allowed the study of peptide:lipid molar ratios from 1:20 to 1:1000. For all conditions studied, the peptides were found to be predominantly incorporated as a transmembrane helix into the membrane, especially at low peptide concentration, but started to aggregate on the membrane surface at higher peptide:lipid ratios. The structural information on the preferred trans-bilayer alignment of the crown ether functional groups explains their ion conductivity and is useful for the further development of membrane-active nanochemotherapeutics

Membrane-Active Peptides and the Clustering of Anionic Lipids

AbstractThere is some overlap in the biological activities of cell-penetrating peptides (CPPs) and antimicrobial peptides (AMPs). We compared nine AMPs, seven CPPs, and a fusion peptide with regard to their ability to cluster anionic lipids in a mixture mimicking the cytoplasmic membrane of Gram-negative bacteria, as measured by differential scanning calorimetry. We also studied their bacteriostatic effect on several bacterial strains, and examined their conformational changes upon membrane binding using circular dichroism. A remarkable correlation was found between the net positive charge of the peptides and their capacity to induce anionic lipid clustering, which was independent of their secondary structure. Among the peptides studied, six AMPs and four CPPs were found to have strong anionic lipid clustering activity. These peptides also had bacteriostatic activity against several strains (particularly Gram-negative Escherichia coli) that are sensitive to lipid clustering agents. AMPs and CPPs that did not cluster anionic lipids were not toxic to E. coli. As shown previously for several types of AMPs, anionic lipid clustering likely contributes to the mechanism of antibacterial action of highly cationic CPPs. The same mechanism could explain the escape of CPPs from intracellular endosomes that are enriched with anionic lipids

Unveiling the Potential of Spirulina Biomass—A Glimpse into the Future Circular Economy Using Green and Blue Ingredients

The present work aims to explore Spirulina biomass’ functional and technological marvels and its components, such as C-phycocyanin (C-PC), in modern food systems from a circular economy perspective, evaluating a decade of insights and innovations. This comprehensive review delves into the pivotal studies of the past decade, spotlighting the vital importance of maintaining stability in various food matrices to unleash the full biological impacts. Through the lens of food science intertwined with circular economy principles, this analysis meets health and environmental requisites and explores the harmonious synergy between food systems, economy, and industry. While Spirulina has typically served as a supplement, its untapped potential as a fundamental food ingredient has been unveiled, showcasing its abundant nutritional and functional attributes. Technological hurdles in preserving the vibrant color of C-PC have been triumphantly surmounted through simple temperature control methods or cutting-edge nanotechnology applications. Despite the gap in sensory acceptance studies, the emergence of blue foods introduces groundbreaking functional and innovative avenues for the food industry

Membrane interactions of latarcins: Antimicrobial peptides from spider venom

A group of seven peptides from spider venom with diverse sequences constitute the latarcin family. They have been described as membrane-active antibiotics, but their lipid interactions have not yet been addressed. Using circular dichroism and solid-state 15N-NMR, we systematically characterized and compared the conformation and helix alignment of all seven peptides in their membrane-bound state. These structural results could be correlated with activity assays (antimicrobial, hemolysis, fluorescence vesicle leakage). Functional synergy was not observed amongst any of the latarcins. In the presence of lipids, all peptides fold into amphiphilic α-helices as expected, the helices being either surface-bound or tilted in the bilayer. The most tilted peptide, Ltc2a, possesses a novel kind of amphiphilic profile with a coiled-coil-like hydrophobic strip and is the most aggressive of all. It indiscriminately permeabilizes natural membranes (antimicrobial, hemolysis) as well as artificial lipid bilayers through the segregation of anionic lipids and possibly enhanced motional averaging. Ltc1, Ltc3a, Ltc4a, and Ltc5a are efficient and selective in killing bacteria but without causing significant bilayer disturbance. They act rather slowly or may even translocate towards intracellular targets, suggesting more subtle lipid interactions. Ltc6a and Ltc7, finally, do not show much antimicrobial action but can nonetheless perturb model bilayers