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Lipid droplets (LDs) are organelles that are necessary for eukaryotic and prokaryotic metabolism and energy storage. They have a unique structure consisting of a spherical phospholipid monolayer encasing neutral lipids such as triacylglycerol (TAG). LDs have garnered increased interest for their implications in disease and for drug delivery applications. Consequently, there is an increased need for tools to study their structure, composition, and dynamics in biological contexts. In this work, we utilize CHARMM‐GUI Membrane Builder to simulate and analyze LDs with and without a plant LD protein, oleosin. The results show that Membrane Builder can generate biologically relevant all‐atom LD systems with relatively short equilibration times using a new TAG library having optimized headgroup parameters. TAG molecules originally inserted into a lipid bilayer aggregate in the membrane center, forming a TAG‐only core flanked by two monolayers. The TAG‐only core thickness stably grows with increasing TAG mole fraction. A 70 % TAG system has a core that is thick enough to house oleosin without its interactions with the distal leaflet or disruption of its secondary structure. We hope that Membrane Builder can aid in the future study of LD systems, including their structure and dynamics with and without proteins. [ABSTRACT FROM AUTHOR]

The uridine 5'-diphosphobacillosamine and undecaprenyl phosphate are used to demonstrate the ability of PglC to produce undecaprenyl pyrophosphate bacillosamine by using radiolabeled HPLC and mass spectral analysis. The biochemical validation of PglC function adds significant to study of the heptasacchride assembly process and sets the stage for the use of PglC to create native and novel substrates for the bacterial N-linked glycosylation machinery.

Results point out that the conformational dimorphism of the prion protein fragment of residues 110-136 is due to the charge state of a single histidine residue. The helical conformation of prion spans the bilayer.

Oleosin is a hydrophobic protein that punctuates the surface of plant seed lipid droplets, which are 20 nm–100 μm entities that serve as reservoirs for high‐energy metabolites. Oleosin is purported to stabilize lipid droplets, but its exact mechanism of stabilization has not been established. Probing the structure of oleosin directly in lipid droplets is challenging due to the size of lipid droplets and their high degree of light scattering. Therefore, a medium in which the native structure of oleosin is retained, but is also amenable to spectroscopic studies is needed. Here, we show, using a suite of biophysical techniques, that dodecylphosphocholine micelles appear to support the tertiary structure of the oleosin protein (i.e., hairpin conformation) and render the protein in an oligomeric state that is amenable to more sophisticated biophysical techniques such as NMR. [ABSTRACT FROM AUTHOR]

The static and dynamic laser light-scattering methods are used for studying the kinetic properties of the self-assembly of hydrophilic Keplerate-type polyoxometalate (POM) {[Mo.sub.77][Fe.sub.30]} macroanions into single-layer, vesicle-like blackberry structures in solutions. The kinetics of the blackberry formation of the {[Mo.sub.77][Fe.sub.30]} macroanions have shown similarities of the self-assembly of virus capsid proteins into spherical capsid shells, which has shown possible connections between the self-assembly behaviors of inorganic species and biological macromolecules.

The preparation of a water-soluble peptide porphyrin assembly was examined. The preparation involves a conformationally stable peptide strapped over the face of a metalloporphyrin in the absence of a peptide side chain to the porphyrin metal center. A high degree of helical structure in the peptide strap was observed. Furthermore, the conformational stability of the peptide provided structural control of the pocket above the porphyrin metal center.

The kinetic properties of the self-assembly of hydrophilic Keplerate-type polyoxometalate (POM) (Mo72Fe30) macroanions into single-layer, vesicle-like blackberry structures in solutions were monitored by the static and dynamic laser light scattering techniques. In the presence of additional electrolytes, an obvious lag period at the initial stage of self-assembly was observed, followed by a fast increase of the scattered intensity. The whole kinetic curve is sigmoidal with a lag phase. A two-step nucleation-growth mechanism is proposed to explain this lag phase: the (Mo72Fe30) macroanions slowly associate into oligomers (mostly dimers), which are the thermodynamically unfavorable intermediates, at the initial stage; once the oligomers reach a critical concentration, the blackberry formation process is accelerated. Analytical ultracentrifugation (AUC) was used to confirm the oligomeric state in (Mo72Fe30) solution during the lag period. The length of the lag period is dependent on temperature, ionic strength, and the valent states of the additional salts, as well as the solvent content. The kinetics (including the lag period) of the blackberry formation of the (Mo72Fe30) macroanions show similarities to the self-assembly of virus capsid proteins (which are also soluble macroions) into spherical capsid shells, suggesting possible connections between the self-assembly behaviors of inorganic species and biological macromolecules. [ABSTRACT FROM AUTHOR]

There is an increasing demand within the pharmaceutical and cosmetic industries for biofriendly lipid-based active ingredient delivery systems. Micelles, liposomes, and lipid nanoparticles are currently the most used systems despite their limitations. Oleosomes, also known as lipid droplets, are promising alternatives to the existing strategies. Oleosomes are typically found in plant cells and are characterized by a nonpolar triacylglycerol core surrounded by a phospholipid monolayer punctuated with the protein oleosin. Producing oleosomes synthetically allows the customization of their lipid content, size, protein content, and oil core characteristics, expanding their versatility. Herein we demonstrate a proof of concept for the use of synthetic oleosomes to sequester polar molecules by modulating their core polarity with blends of sunflower and castor oils. The physical properties (density, refractive index, and permittivity) of the oil blends are characterized and demonstrate ideal mixing of the oils, which is supported by molecular dynamics simulations. Spectroscopic examination of the oil blends using fluorescent probes shows that the polarity of oil blends increases as the fraction of castor oil increases. Finally, we show that the uptake of a polar fluorescent probe (NBD-glucose) into synthetic oleosomes is enhanced by increasing the polarity of the oil core, but large charged molecules are excluded from the core regardless of polarity. These experiments show that synthetic oleosomes with tunable oil cores can expand the range of molecules that can be loaded into a biofriendly package as desired for biotechnology applications., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Caveolin-1 is a 20.5 kDa integral membrane protein that is involved in a myriad of cellular processes including signal transduction, relieving mechano-stresses on the cell, endocytosis, and most importantly caveolae formation. As a consequence, there is intense interest in characterizing caveolin-1 structurally. Out of the many available structural techniques, nuclear magnetic resonance (NMR) spectroscopy is particularly well suited to investigations on integral membrane proteins like caveolin-1 that have significant unstructured regions and unusual topologies. However, the technique requires relatively large amounts of protein (i.e. concentrations in the 0.5-5 mM range), and obtaining these amounts can be difficult especially for highly hydrophobic membrane proteins such as caveolin-1. Herein, we describe a robust protocol for the preparation of caveolin-1 for structural studies using NMR.