Unravelling hierarchical levels of structure in lipid membranes

Synthetic Lipid Biology

Cells contain thousands of different lipids. Their rapid and redundant metabolism, dynamic movement, and many interactions with other biomolecules have justly earned lipids a reputation as a vexing class of molecules to understand. Further, as the cell's hydrophobic metabolites, lipids assemble into supramolecular structures─most commonly bilayers, or membranes─from which they carry out myriad biological functions. Motivated by this daunting complexity, researchers across disciplines are bringing order to the seeming chaos of biological lipids and membranes. Here, we formalize these efforts as "synthetic lipid biology". Inspired by the idea, central to synthetic biology, that our abilities to understand and build biological systems are intimately connected, we organize studies and approaches across numerous fields to create, manipulate, and analyze lipids and biomembranes. These include construction of lipids and membranes from scratch using chemical and chemoenzymatic synthesis, editing of pre-existing membranes using optogenetics and protein engineering, detection of lipid metabolism and transport using bioorthogonal chemistry, and probing of lipid-protein interactions and membrane biophysical properties. What emerges is a portrait of an incipient field where chemists, biologists, physicists, and engineers work together in proximity─like lipids themselves─to build a clearer description of the properties, behaviors, and functions of lipids and membranes.

Self-assembly of differently charged trimesic based lithocholic amphiphiles and their assessment on antimicrobial and biostimulant properties

Biosurfactant based biostimulants plays a vital role in agriculture filed by enhancing the soil quality, promote plant growth, and eliminate plant pathogens, and increasing nutrient uptake. This manuscript describes the synthesis of trimesic based lithocholic ester functionalized amphiphiles (TMLCEA) with oppositely charged head groups using thiol-yne click chemistry, which is an effective and simple approach. The trimesic based lithocholic ester functionalized zwitterionic penicillamine (TMLCEPA), cationic cysteamine·HCl (TMLCECy), and anionic thiomalic acid (TMLCETM) exhibited hierarchically self-assembled microstructures from below to above the CMC. In below the CMC, TMLCEPA, TMLCECy, and TMLCETM showed a bundle of petals, flower-like morphology, and grass seed-like patterns respectively. The morphology of self-assembly was studied by FE-SEM, DLS, OPM, contact angle, and zeta potential measurements. Among these amphiphiles, TMLCECy exhibited potential antimicrobial activity at above the CMC. The biostimulant effect of different concentration of TMLCEA treated with maize and green gram seeds were evaluated under in vitro condition, wherein TMLCECy showed improved seed germination and seedling parameters at 750 µL/mL as compared to TMLCEPA, TMLCETM and untreated amphiphiles as control. Molecular docking and molecular dynamic simulations show that TMLCEPA and TMLCETM showed higher binding affinity for dengue methyltransferase protein. The result of the present study opens up new avenues for bile acid-based amphiphiles as bio-based and cost-effective biostimulants for sustainable agriculture.

The intricate link between membrane lipid structure and composition and membrane structural properties in bacterial membranes

It is now evident that the cell manipulates lipid composition to regulate different processes such as membrane protein insertion, assembly and function. Moreover, changes in membrane structure and properties, lipid homeostasis during growth and differentiation with associated changes in cell size and shape, and responses to external stress have been related to drug resistance across mammalian species and a range of microorganisms. While it is well known that the biomembrane is a fluid self-assembled nanostructure, the link between the lipid components and the structural properties of the lipid bilayer are not well understood. This perspective aims to address this topic with a view to a more detailed understanding of the factors that regulate bilayer structure and flexibility. We describe a selection of recent studies that address the dynamic nature of bacterial lipid diversity and membrane properties in response to stress conditions. This emerging area has important implications for a broad range of cellular processes and may open new avenues of drug design for selective cell targeting.

Membranes are functionalized by a proteolipid code

Membranes are protein and lipid structures that surround cells and other biological compartments. We present a conceptual model wherein all membranes are organized into structural and functional zones. The assembly of zones such as receptor clusters, protein-coated pits, lamellipodia, cell junctions, and membrane fusion sites is explained to occur through a protein-lipid code. This challenges the theory that lipids sort proteins after forming stable membrane subregions independently of proteins.

Molecular insights into the effects of focused ultrasound mechanotherapy on lipid bilayers: Unlocking the keys to design effective treatments

Administration of focused ultrasounds (US) represents an attractive complement to classical therapies for a wide range of maladies, from cancer to neurological pathologies, as they are non-invasive, easily targeted, their dosage is easy to control, and they involve low risks. Different mechanisms have been proposed for their activity but the direct effect of their interaction with cell membranes is not well understood at the molecular level. This is in part due to the difficulty of designing experiments able to probe the required spatio-temporal resolutions. Here we use Molecular Dynamics (MD) simulations at two resolution levels and machine learning (ML) classification tools to shed light on the effects that focused US mechanotherapy methods have over a range of lipid bilayers. Our results indicate that the dynamic-structural response of the membrane models to the mechanical perturbations caused by the sound waves strongly depends on the lipid composition. The analyses performed on the MD trajectories contribute to a better understanding of the behavior of lipid membranes, and to open up a path for the rational design of new therapies for the long list of diseases characterized by specific lipid profiles of pathological membrane cells.