Researchers have explored and cultivated suitable membrane mimetics to preserve a physiological solvent condition for membrane protein functions. This involves emulating the properties of lipid bilayers, particularly within the hydrophobic core. Membrane mimetics exist in diverse forms, such as micelles, bicelles, liposomes, and nanodiscs. Polymers, such as styrene-maleic acid (SMA), have been found to offer a potentially suitable means to solubilize membrane proteins without resorting to detergents. It is widely recognized that various membrane mimetics yield distinct structural and dynamic configurations in membrane proteins. Styrene-maleic acid derivatives (SMADs) are of particular significance in this study; they are known for their ability to generate lipid nanoparticles. It has been hypothesized that using SMA derivatives with the same charge as the target membrane protein preserves the protein's structural and dynamic attributes compared to other bilayer membrane mimetics. This study explores the impact of different charges of SMA derivatives on two bacteriophage-encoded peptides explicitly focusing on their influence as charged peptides. Positively charged, neutral, and negatively charged SMA derivatives interactions with pinholin S and the phage-encoded cationic antimicrobial peptide gp28 lipid vesicles were assessed. These interactions were characterized using dynamic light scattering (DLS) techniques and continuous wave electron paramagnetic resonance (CW-EPR) spectroscopy. From our DLS results, we observed a reduction in size compared to the vesicle control, which is consistent with the formation of SMADLPs (styrene maleic acid derivative lipid nanoparticles). The key outcome was in the identification of how various SMA derivatives affect the interaction of gp28 and pinholin membrane peptides, which is useful when trying to understand how the different SMA polymers can influence the behavior and stability of protein complexes. For gp28 peptide, CW-EPR spectral analysis indicates no line broadening in its profile, suggesting that binding interactions with SMA derivatives do not significantly disrupt the structural integrity or dynamic behavior of the gp28 peptide. SMA-Pos interaction with pinholin shows some minimal perturbation, confirming that it is not as compatible compared to SMA-Neut and SMA-Glu. This study will provide insights into the optimal conditions for studying membrane protein interactions, focusing on the structural dynamics of gp28 and pinholin in the presence of different SMA derivatives.

Nervonic Acid (NA), as a critical component of neural myelin sheaths, maintains nerve cell structural integrity and function. Due to limited synthesis in humans, it is primarily obtained through plant extraction, chemical synthesis, or biosynthetic methods. Its bioactive properties and applications encompass: mitigating oxidative stress and improving cognitive function; balancing pro-/anti-inflammatory factors to alleviate inflammation in organs such as liver or colon while modulating gut microbiota; its level fluctuations being closely associated with psychiatric disorders and metabolic diseases, demonstrating biomarker potential for early diagnosis. Furthermore, nervonic acid exerts multi-dimensional protective effects on cardiovascular health and metabolic homeostasis, while serving as a functional ingredient in dietary supplements and infant formula. This review systematically elaborates on the three primary sources of nervonic acid, discusses its biological functions in neuroprotection, anti-inflammatory activity, and metabolic regulation, and explores its potential applications in biomarker development and functional foods. The review aims to provide an important theoretical foundation for future disease prevention strategies and the development of health-oriented products.

The selection of lipids and their ratios play a critical role in determining drug loading capacity and the structural properties of nanostructured lipid carriers (NLCs), directly impacting their stability. Among liquid lipids, vegetable oils have been explored both as active pharmaceutical ingredients (APIs) and as excipients in NLCs intended for topical use. The pulp oil of Tucumã, derived from Brazilian biodiversity, is known for its anti-inflammatory and antioxidant properties, attributed to its high content of carotenoids. This study focused on evaluating the compatibility of Tucumã oil with various solid lipids (SLs) commonly used in NLC production, developing an optimized NLC formulation containing this oil, and monitoring its stability over a 28-days' period. Lipid screening was performed to assess the compatibility of Tucumã oil with a series of SLs, followed by preliminary formulations to determine the type of SL and surfactant for the experimental design. A 2 experimental factorial design was used to understand and identify the significant effects and interactions of lipid phase and surfactant concentrations on Tucumã oil-loaded NLCs, and the stability of the optimized formulation was monitored by determining the mean particle size (z-Ave), polydispersity index (PI), zeta potential (ZP), and recrystallization index (RI%) over 28 days. Compritol® was identified as the most suitable SL, resulting in round shaped NLCs with z-Ave of 309 nm, PI of 0.23 and high ZP (-25.5 mV). The RI% was shown to be influenced by the storage time and temperature. The optimal formulation contained 8 % of lipid phase (at a 20:80 ratio of oil to SL) and 3 % of Tween® 80 as surfactant, showing stability at 5ºC, 25ºC and 40ºC. The experimental factorial design revealed a positive effect of surfactant concentration on z-Ave and PI, with no significant impact on ZP. Over time, NLCs exhibited a gradual color loss (becoming whiter), with no other signs of instability. These findings support the potential use of Tucumã oil for producing stable NLCs suitable for topical delivery.

The role of cholesterol in the organization and ordering of membrane domains has been well established over the past decades. However, the involvement of cholesterol precursors and byproduct sterols in modulating the physicochemical properties of cell membranes remains less thoroughly explored. In this study, we investigated the effects of cholesterol, two hydroxylated catabolites (24-hydroxycholesterol and 25-hydroxycholesterol), and two biosynthesis precursors (desmosterol and lanosterol) on model of liquid-ordered (Lo) and liquid-disordered (Ld) membrane domains. Membrane ordering and molecular mobility were assessed using two fluorescent probes; Laurdan, which senses polarity near the membrane aqueous interface and cholesterol-pyrene, which senses ordering closer to the center of the membrane bilayer. The results showed that Laurdan can distinguish between environmental polarity and the contribution of membrane domains. The probe mobility varied depending on the sterol and did not strictly correlate with membrane order. Cholesterol-pyrene revealed that the sterols induce varying degrees of ordering around the bilayer center. A notable observation in Ld membranes using different probes was that the ordering effect of sterols was similar near the lipid head groups and at the center of the bilayer. Hydroxycholesterols exhibited a low ordering effect, whereas cholesterol and desmosterol induced a strong effect. In contrast, in Lo membranes, hydroxycholesterols produced a strong ordering effect near the head groups but a reduced effect near the bilayer center.

Branched-chain fatty acids (BCFAs) exhibit potential anticancer activity, but their systematic evaluation and comparison with straight-chain saturated fatty acids (SSFAs) remain limited due to monomer accessibility issues. This study utilized lanolin, a rich BCFA/SSFA mixture, to systematically assess anti-hepatoma activities of 50 fatty acids using multiple linear regression (MLR) and orthogonal partial least squares (OPLS) models combined with HepG2 cell viability, apoptosis, and cell cycle assays. MLR identified iso-C13:0 as a unique protective fatty acid, while OPLS revealed strong explanatory power (R2X = 0.827-0.997, R2Y = 0.718-0.782) and key anti-hepatoma fatty acids, including SSFAs (C12:0, C13:0, C14:0, C19:0, C21:0) and BCFAs (16-19-carbon iso-BCFAs, 14-19-carbon anteiso-BCFAs). Notably, SSFAs outperformed BCFAs in certain activities, and a structure-activity trend emerged: odd-carbon BCFAs favored cell cycle arrest, even-carbon BCFAs promoted apoptosis, and 13-21-carbon fatty acids showed stronger activity. The integrated approach validated lanolin as an ideal matrix for functional lipid screening, providing a methodology to identify anticancer fatty acids in complex mixtures and challenging the conventional superiority of BCFAs.

The intercellular lipid matrix of stratum corneum is composed of many lipid components, including ceramides, free fatty acids, and cholesterol, which nonetheless form regularly arranged structures; short- and long-period lamellar structures, and hexagonal and orthorhombic hydrocarbon-chain packing structures. From the viewpoint of compatibility among the structures, there should be a correlation between a lamellar structure arranged periodically along the long axis of the lipid molecules and a packing structure of the hydrocarbon chains in the plane orthogonal to the long axis. To address this issue, differential scanning calorimetry and temperature-dependent X-ray diffraction experiment were performed on human stratum corneum. A detailed comparative analysis of the results on phase transitions obtained by the two methods revealed that the short-period lamellar structure has the orthorhombic hydrocarbon-chain packing structure that is normally observed, while the long-period lamellar structure has another orthorhombic hydrocarbon-chain packing structure hidden in the normal structure, and furthermore, the hexagonal hydrocarbon-chain packing structure does not appear to form a corresponding multilamellar structure and start to undergo a phase transition to the liquid state approximately at 33 °C. The domain constructed with the short-period lamellar structure and the orthorhombic hydrocarbon-chain packing structure is important in considering the water regulation mechanism in stratum corneum, since it provides evidence not only of the water layer of the former but also of changes in the head group of the latter.

While α-tocopherol is widely studied for its antioxidant role in membranes, its potential as a functional component of liposomal carriers remains underexplored, despite their range of interesting biological activities and growing use in nanocarrier systems. This study systematically evaluates how three tocopherol derivatives - α-tocopherol phosphate (TP), α-tocopherol succinate (TS), and α-tocopherol polyethylene glycol succinate (TPGS)-affect nanoliposomes, focusing on colloidal stability, encapsulation efficiency, and fundamental membrane properties such as fluidity, hydration, and thermotropic behavior. Results showed that all α-tocopherol derivatives significantly altered membrane properties, inducing structural changes in both the lipid chain and polar regions of the liposome bilayer. TS enhanced membrane rigidity and reduced permeability, while TP increased fluidity and promoted payload release. TPGS, with its bulky PEG chain, stabilized liposomes but induced phase heterogeneity. Additionally, all derivatives lowered the lipid main phase transition temperature and altered its thermotropic behavior. Despite these disruptions, the derivatives preserved nanoscale vesicle sizes (∼100 nm) and monodisperse distributions (PDI < 0.3) over extended storage. These experimental observations were further supported by molecular dynamics simulations, which confirmed differences in membrane affinity among the derivatives, with TS showing the strongest binding affinity. The simulations also revealed that the derivatives' positioning within the bilayer and their interactions-mainly hydrogen bonding and hydrophobic contacts-contribute to their distinct effects on membrane structure and dynamics. Collectively, these findings demonstrate that α-tocopherol derivatives distinctly modulate liposomal membrane architecture and behavior in a structure-dependent manner, offering promising tools for tuning nanocarrier performance in pharmaceutical applications.

Vitamin E denotes a cluster of eight molecules, i.e., α-tocopherol, β-tocopherol, δ-tocopherol, γ-tocopherol, α-tocotrienol, β-tocotrienol, δ-tocotrienol and γ-tocotrienol, where the α-tocopherol isoform is the major form. Vitamin E is one of the natural most potent antioxidants and an indispensable molecule for human health, since its major function is the inhibition of free-radical lipid peroxidation propagation. Vitamin E has a lipophilic nature and localize in membranes and lipoproteins and could affect either both its biological properties or membrane structure. I have used molecular dynamics to know the position and orientation of these eight biomolecules in water and inside a biomembrane, besides finding any interactions with their lipidic components. When they are in the membrane, all molecules tend towards their most extended conformation, inserting well between the phospholipid hydrocarbon chains. Our data agree with the general consensus, i.e., the chromanol group is located near the oxygen atom of cholesterol, whereas its hydrophobic chain extends to the membrane middle. This does not prevent the existence of flip-flop between the two monolayers. Significantly, the tocopherol/tocotrienol molecules inside the membrane did not aggregate. Remarkable, α-tocopherol presented a relatively high diffusion coefficient when compared to the other molecules and the α-tocopherol transfer protein seems to be the most suitable for its transport and transfer to the membrane. Although in principle any tocopherol or tocotrienol could function as an antioxidant, nature has chosen α-tocopherol thanks to the sum of a series of very subtle characteristics.

Model lipid bilayers, reconstituted by using bacterial lipid extracts, are reliable systems to investigate the physical properties of bacterial membranes, and can be used, for example, to aid the design of new antibiotics. Here, we discuss the optimisation of a protocol for the production of hydrogenous and deuterated glycerophospholipid (GPL) extracts from Escherichia coli, and their reconstitution into model membranes. This protocol stands apart from state-of-the-art methods by introducing an additional purification step, which ensures a better separation of the GPL molecules from other membrane components such as neutral lipids. The composition of these extracts was characterised with different analytical methods. Experimental conditions were optimised for producing bacterial membrane models in the form of vesicles, lipid monolayers at the air/water interface and supported lipid bilayers. A combination of biophysical techniques, including Langmuir isotherms, neutron reflectometry, quartz crystal microbalance with dissipation monitoring, and small angle X-ray scattering provided detailed information on the self-assembled structures, and highlighted interesting differences between hydrogenous and deuterated extracts. Altogether, we report a detailed description of extraction and characterisation of hydrogenous and deuterated E. coli GPL extracts. The study of such complex lipid mixtures is important to recreate highly biologically relevant bacterial membrane models for studies aimed at understanding the biological function of bacterial membranes.

Sphingolipids constitute a class of bioactive lipids essential for the structural and functional integrity of milk fat globule membrane (MFGM). Milk sphingomyelin (milk-SM), as a key component of MFGM, contributes to the stability of milk fat emulsions. Milk-SM and other sphingolipids, like glycosphingolipids (GSL), coexist in the same outer bilayer of MFGM, suggesting significant role of their interaction in shaping the structural properties and functions of MFGM. In this study, using an in-vitro model membrane system, we investigated the impact of various GSLs, including cerebrosides and gangliosides, on the lateral segregation and phase behavior of milk-SM in 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine bilayers. We also incorporated N-palmitoyl-D-erythro-ceramide for a comparative analysis of the impacts of sphingolipid head groups. The lateral segregation of sphingolipid gel phases was assessed using trans-parinaric acid (tPA) fluorescence lifetime analysis, and their thermostability was examined using steady-state fluorescence anisotropy of tPA. Additionally, we assessed the binary interactions between milk-SM and GSLs using the steady-state fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene (DPH). The results indicate that GSLs promote the lateral segregation and stabilization of milk-SM-rich gel phases in the membrane bilayers. The size of the GSL head groups significantly influenced the degree of this stabilization, with larger head groups demonstrating diminished interactions with milk-SM. Our results provide valuable insights into the role of various sphingolipid structures in membrane phase behavior and organization. Comprehensive understanding of the interactions of these important sphingolipids in MFGM environment is crucial due to their structural and functional importance in dairy and nutritional applications.

A variety of studies published in the last decades in the field of lipid biophysics deal with the puzzle regarding the relationship between the signaling power of bioactive lipids (sphingolipids) and their capacity to induce lipid membrane heterogeneity (domains). Advances in technology, particularly Atomic Force Microscopy (AFM), have provided a solid contribution in this regard. Moreover, supported planar bilayers (SPB) have become an established membrane model in the study of lipid-lipid interactions. However, in spite of the large amount of published results in this field, the data remain scattered, and a coherent collection that allows easy access to the investigator is missing. This review summarizes the relevant results obtained in our laboratory through the use of AFM under comparable experimental conditions, offering a collection of data on supported lipid bilayer thicknesses and breakthrough forces. An extensive list of lipid compositions including phospholipids, cholesterol and sphingolipids (sphingomyelins, ceramides), at varying molecular ratios, has been considered.

Atherosclerosis is partially driven by the accumulation of oxidised low-density lipoprotein (oxLDL), which facilitates foam cell formation and vascular inflammation. This research examines the efficacy of bamboo charcoal (BC) as a bioactive agent for neutralising oxLDL using both in silico and in vitro methodologies. Molecular docking demonstrated significant binding affinities between BC and essential constituents of oxLDL, such as oxidised cholesterol and apolipoprotein B-100, facilitated by π-π stacking and electrostatic interactions. Molecular dynamics simulations demonstrated the stability of these complexes over 300 ns, indicating sustained molecular interactions. Quantum chemical calculations employing density functional theory showed a narrow HOMO-LUMO gap of 0.45 eV and a significant dipole moment of approximately 45 D, underscoring the reactive and polar characteristics of BC. Electrostatic potential mapping and thermodynamic analyses provided additional evidence for BC's spontaneous and stable binding to oxLDL components. The Oil Red O staining and total cholesterol estimation assays were conducted on oxLDL-treated RAW 264.7 macrophages in vitro indicated that BC significantly decreased macrophage-derived foam cell formation, thereby confirming its ability to reduce oxLDL-induced lipid accumulation. The findings suggest that BC functions as a physical adsorbent and a participant in direct chemical interactions with oxLDL, providing a dual-action therapeutic approach to atherosclerosis.

Gramicidin A (GrA), a well-known ionophore, plays a significant role in modifying the biophysical properties of membranes. However, its mechanism of action in influencing rupture kinetics of vesicles and the stability of membranes under constant mechanical tension remains unclear. To investigate this, giant unilamellar vesicles (GUVs) composed of DOPG and DOPC phospholipids, with varying molar fractions of GrA (ranging from 0 % to 5 %), were synthesized using the natural swelling method. These GUVs were then subjected to mechanical tension using the micropipette aspiration technique. The rupture kinetics were assessed by quantifying the fraction of intact vesicles over time under a fixed mechanical tension, allowing the determination of the rupture rate constant. The results revealed a non-monotonic effect of GrA on membrane rupture: at low concentrations (up to 1 % GrA), GUVs exhibited increased structural stability, while at higher concentrations (1-5 % GrA), rupture probability significantly increased. Additionally, the area compressibility modulus of the GUV membranes was evaluated, showing that GrA incorporation led to alterations in membrane elasticity. These findings provide insights into the molecular mechanisms by which GrA modulates membrane integrity under mechanical stress, offering valuable implications for biophysical studies of ionophore-lipid interactions and membrane stability in biological systems.

The properties of phospholipid bilayers, which are important in various biophysical and biomedical studies, critically depend on the hydration of the lipid bilayer. Interbilayer water in multilamellar vesicles or planar multilayers is a very convenient object for studying the interfacial lipid-water interaction. However, many parameters of the interbilayer water remain incompletely studied, and in some cases different experimental methods yield different parameters of interbilayer water. Here, we developed a Raman spectroscopy method for characterizing interbilayer water in multilayer phospholipid samples. This method was applied to one saturated (DPPC) and one unsaturated (DOPC) phospholipid hydrated at high relative humidity and studied over a wide temperature range. It was found that although above the freezing point of water the OH stretching spectra of interbilayer water were similar to those of bulk water, only about one-fifth of the interbilayer water crystallized at the lowest experimental temperature (110 K). In combination with Raman spectra of aqueous suspensions of phospholipids of known compositions, the number of interbilayer HO molecules per lipid molecule (hydration number) was determined. The hydration number was found for the ordered (gel) and disordered (fluid) phases of hydrated phospholipid bilayers at different temperatures and several relative humidities. The results were compared with values of the hydration number obtained by other methods, and an interpretation was proposed that takes into account the fractions of the free and non-free (perturbed) interbilayer water.

Prostate cancer (PC) is one of the most prevalent malignancies among men, with a staggering 1.5 million new cases and 350,000 deaths reported globally in 2022. Conventional treatment methods, including chemotherapy, radiation therapy, surgery, and hormonal therapy, often encounter significant challenges such as systemic toxicity and diminished efficacy, particularly in the advanced stages of the disease. Treatment of prostate cancer remains a formidable challenge because of the poor water solubility of many chemotherapeutic agents, which severely limits their bioavailability. However, the rise of targeted therapies has catalyzed the development of innovative drug delivery systems designed to enhance the bioavailability and precision of therapeutic agents. Solid lipid nanoparticles (SLNs) are a promising solution that can effectively encapsulate chemotherapeutic agents and genetic materials. Their unique attributes, such as biocompatibility, controlled release profile, and customizable surface properties, make them advantageous alternatives to conventional treatment strategies, effectively addressing the inherent limitations of prostate cancer therapy.

Hinokitiol (β-thujaplicin) is a natural antimicrobial agent used in cosmetics. The aim of presented studies was to gain insight into the interactions of hinokitiol with lipids in model membranes and to correlate this with the selective effect of hinokitiol on cells. To reach this goal, the toxicity of hinokitiol was evaluated using keratinocyte and fibroblast cell lines, and studies were performed on lipid monolayers (both one component and mixed systems). During investigations the surface pressure - area measurements, penetration studies and Brewster angle microscopy experiments were done. The analysis of the parameters calculated from the experimental data and the comparison of BAM images evidenced that, at membrane - related surface pressure, hinokitiol does not insert into model keratinocyte and fibroblast membranes and its impact on these systems is very weak. This important conclusion correlates with the in vitro experiments. The results for one component systems evidenced that the effect of hinokitiol on mammalian lipid films depends on the monolayer organisation and the lipid structure (especially the lipid polar head). In consequence, the type and proportion of lipids determines the effect of hinokitiol on the mixed films. The latter corroborates with the differences in the influence of hinokitiol on bacteria compared to mammalian lipids. It was concluded that hinokitiol exhibits selective activity toward bacterial cells compared to mammalian cells and their corresponding model membranes. Thus, the predominance of hinokitiol's antibacterial properties over its toxicity to skin cells may therefore be related to interactions of this compound with membrane lipids.

Dynamic interactions between microbes and host are essential to stimulate the immune system, maintain intestinal homeostasis, and prevent pathogen colonization. In recent decades lactic acid bacteria (LAB) have received attention due to their probiotic potential and their impact on gut microbiota and host health. This paper aims to review the main molecular mechanisms by which bile acids (BA) modify the composition of the intestinal microbiota and bacterial viability, with special emphasis on the effect on LAB. The results discussed here suggest that the BA disorganize the structure of the bacterial cell wall, modify their surface properties, their adhesion capacity and compromise the integrity of the membranes, with loss of essential ions and nutrients. They then enter the cell interior, at rates that depend on their hydrobicity. There, they dissociate, causing intracellular acidification and dissipation of membrane potential. This leads to a deficiency in the biological energy needed for critical processes, leading to cell death at high concentrations. In addition, BA causes alteration and oxidation of proteins and nucleic acids. The extent of damage caused by BA is influenced by their structure, physicochemical properties-particularly hydrophobicity-and concentration. The response of LAB depends on both their intrinsic and adaptive mechanisms. Advancing research on these interactions represents a new frontier, enabling the development of strategies to modulate intestinal microbiota composition, ultimately benefiting human health.

Astaxanthin (ASX) is a natural xanthophyll carotenoid recognized for its strong antioxidant bioactive function, and it has been used in the prevention of heart disease, inflammation, neurological disorders, scavenger of environmental produced free radicals and as an anti-aging and anti-cancer biomolecule. ASX is a long lipophilic molecule with two terminal relatively polar rings connected by a long hydrophobic chain. This work describes the dynamics, orientation, location and interactions of ASX in a complex biomembrane. In water, ASX form high-order aggregates where the molecules are joined together by the hydrophobic chain. Depending on the number of ASX molecules, the aggregates can have different structures and the polar groups positioned superficially contacting the solvent. ASX molecules are not able to insert themselves into the membrane, forming high-order aggregates quickly. In the membrane, ASX molecules do not aggregate, remaining all time in the monomeric state. ASX is capable of reaching both membrane surfaces, one at a time. The ASX molecules form an approximate angle of 20º with respect to the membrane perpendicular and it is inserted between the phospholipid hydrocarbon chains, increasing slightly the membrane fluidity. ASX is readily miscible with membrane phospholipids and its location within the membrane is suited for its potent antioxidant activity. Furthermore, since ASX has two polar groups at both ends, the molecule can function in a wide range of depths. ASX is therefore perfectly suited for its antioxidant task in the membrane.

The phenomenological description of a lipid membrane within the frame of the interphase model in which membrane is a bidimensional solution of hydrated lipids allows to make compatible the membrane theory and Ling hypothesis by considering the physical chemical properties of the aqueous lipid interphase. The membrane suffers mechanical stress inducing changes in hydration and changes in composition. These conditions affect the amount of labile active water propense to response to bioeffectors. This behavior is properly described with the approach of thermodynamic of irreversible processes in which the membrane is an open system and is in a metastable state propense to react due to bioeffectors in the adjacent aqueous solution. In terms of this analysis, the hydration shell is inert to bioeffectors and the response of the membrane is given by the excess of water that is labile and osmotically exchangeable.