Atomistic Characterization of Healthy and Damaged Hair Surfaces: A Molecular Dynamics Simulation Study of Fatty Acids on Protein Layer.

Amid the bourgeoning demand for in-silico designed, environmentally sustainable, and highly effective hair care formulations, a growing interest is evident in the exploration of realistic computational model for the hair surface. In this work, we present an atomistic model for the outermost layer of the hair surface derived through molecular dynamics simulations, which comprises 18-Methyleicosanoic acid (18-MEA) fatty acid chains covalently bound onto the keratin-associated protein 10-4 (KAP10-4) at a spacing distance of ~1 nm. Remarkably, this hair surface model facilitates the inclusion of free fatty acids (free 18-MEA) into the gaps between chemically bound 18-MEA chains, up to a maximum number that results in a packing density of 0.22 nm2 per fatty acid molecule, consistent with the optimal spacing identified through free energy analysis. Atomistic insights are provided for the organization of fatty acid chains, structural features, and interaction energies on protein-inclusive hair surface models with varying amounts of free 18-MEA (FMEA) depletion, as well as varying degrees of anionic cysteic acid from damaged bound 18-MEA (BMEA), under both dry and wet conditions. In the presence of FMEA and water, the fatty acid chains in a pristine hair surface prefers to adopt a thermodynamically favored extended chain conformation, forming a thicker protective layer (~3 nm) on the protein surface. Our simulation results reveal that, while the depletion of FMEA can induce a pronounced impact on the thickness, tilt angle, and order parameters of fatty acid chains, the removal of BMEA has a marked effect on water penetration. There is a "sweet spot" spacing between the 18-MEA whereby damaged hair surface properties can be reinstated by replenishing FMEA. Through the incorporation of the protein layer and free fatty acids, the hair surface models presented in this study enables a realistic representation of the intricate details within the hair epicuticle, facilitating a molecular scale assessment of surface properties during the formulation design process.

Mimicking the hair surface for neutron reflectometry.

The surface of human hair is normally hydrophobic as it is covered by a lipid layer, mainly composed of 18-methyleicosanoic acid (18-MEA). When the hair is damaged, this layer can be partially or fully removed and more hydrophilic, mainly negatively charged surfaces are formed with a wide variety of physical and chemical characteristics. The cosmetic industry is currently embracing the opportunity of increasing the sustainability of their hair-care products whilst improving product performance. To do this, it is vital to have a deeper understanding of the hair surface and how it interacts with hair-care ingredients. This work contributes to this by harnessing the potential of neutron reflectometry (NR) with scattering contrast variation to describe hierarchical adsorption. Three types of hair-mimetic surfaces have been produced: two "healthy hair" models to probe the role of lipid structure, and one "damaged hair" model, to consider the effect of the surface charge. Adsorption of hair-care ingredients has then been studied. The results for these relatively short lipid models indicate that a methyl branch has little effect on adsorption. The "damaged hair" studies, however, reveal the unexpected apparent adsorption of an anionic surfactant to a negative surface. This preferential adsorption of the otherwise solubilised neutral components demonstrates a facile route to selectively deliver a protective film on a damaged hair fibre, without the need for a cationic species. On a more general note, this study also demonstrates the feasibility of using NR to characterize such complex systems.

Effect of Blanching Pomegranate Seeds on Physicochemical Attributes, Bioactive Compounds and Antioxidant Activity of Extracted Oil.

This study investigated the effect of blanching pomegranate seeds (PS) on oil yield, refractive index (RI), yellowness index (YI), conjugated dienes (K232), conjugated trienes (K270), total carotenoid content (TCC), total phenolic compounds (TPC) and DPPH radical scavenging of the extracted oil. Furthermore, phytosterol and fatty acid compositions of the oil extracted under optimum blanching conditions were compared with those from the oil extracted from unblanched PS. Three different blanching temperature levels (80, 90, and 100 °C) were studied at a constant blanching time of 3 min. The blanching time was then increased to 5 min at the established optimum blanching temperature (90 °C). Blanching PS increased oil yield, K232, K270, stigmasterol, punicic acid, TPC and DPPH radical scavenging, whereas YI, ß-sitosterol, palmitic acid and linoleic acid were decreased. The RI, TCC, brassicasterol, stearic acid, oleic acid and arachidic acid of the extracted oil were not significantly (p > 0.05) affected by blanching. Blanching PS at 90 °C for 3 to 5 min was associated with oil yield, TPC and DPPH. Blanching PS at 90 °C for 3 to 5 min will not only increase oil yield but could also improve functional properties such as antioxidant activity, which are desirable in the cosmetic, pharmaceutical, nutraceutical and food industries.

Molecular basis of P450 OleTJE: an investigation of substrate binding mechanism and major pathways.

Cytochrome P450 OleTJE has attracted much attention for its ability to catalyze the decarboxylation of long chain fatty acids to generate alkenes, which are not only biofuel molecule, but also can be used broadly for making lubricants, polymers and detergents. In this study, the molecular basis of the binding mechanism of P450 OleTJE for arachidic acid, myristic acid, and caprylic acid was investigated by utilizing conventional molecular dynamics simulation and binding free energy calculations. Moreover, random acceleration molecular dynamics (RAMD) simulations were performed to uncover the most probable access/egress channels for different fatty acids. The predicted binding free energy shows an order of arachidic acid < myristic acid < caprylic acid. Key residues interacting with three substrates and residues specifically binding to one of them were identified. The RAMD results suggest the most likely channel for arachidic acid, myristic acid, and caprylic acid are 2e/2b, 2a and 2f/2a, respectively. It is suggested that the reaction is easier to carry out in myristic acid bound system than those in arachidic acid and caprylic acid bound system based on the distance of Hß atom of substrate relative to P450 OleTJE Compound I states. This study provided novel insight to understand the substrate preference mechanism of P450 OleTJE and valuable information for rational enzyme design for short chain fatty acid decarboxylation.

Spontaneous nematic alignment of a lipid nanotube in aqueous solutions.

The dispersibility and liquid crystal formation of a self-assembled lipid nanotube (LNT) was investigated in a variety of aqueous solutions. As the lipid component, we chose a bipolar lipid with glucose and tetraglycine headgroups, which self-assembled into an LNT with a small outer diameter of 16 to 17 nm and a high axial ratio of more than 310. The LNT gave a stable colloidal dispersion in its dilute solutions and showed spontaneous liquid crystal (LC) alignment at relatively low concentrations and in a pH region including neutral pH. The LNT samples with shorter length distributions were prepared by sonication, and the relationship between the LNT axial ratio and the minimum LC formation concentration was examined. The robustness of the LNT made the liquid crystal stable in mixed solvents of water/ethanol, water/acetone, and water/tetrahydrofuran (1:1 by volume) and at a temperature of up to 90 °C in water. The observed colloidal behavior of the LNT was compared to those of similar 1D nanostructures such as a phospholipid tubule.

Insights into the structure of covalently bound fatty acid monolayers on a simplified model of the hair epicuticle from molecular dynamics simulations.

The epicuticle is the outermost layer of the human hair, and consists of a monolayer of fatty acids that is predominantly 18-methyleicosanoic acid (18-MEA) covalently bound to a protein matrix. Surprisingly, despite the clear scientific and industrial importance, the detailed molecular structure of this fatty acid layer is still poorly understood. In this work, we aim to gain insight into the structure of this so-called F-layer by performing molecular dynamics simulations on a simplified hair surface model consisting of a monolayer of 18-MEA covalently attached to graphene sheets at various separation distances. The relative free energy of the fatty acid layer was calculated as a function of separation distance in order to obtain the optimal packing density of the fatty acids. Conformational properties such as the thickness, tilt angle, and order parameter of the fatty acid layers were also calculated to characterize the structure of the F-layer. Simulations of the structurally similar eicosanoic acid (EA) were also performed as a comparison and to investigate the role of the anteiso-methyl side chain at the 18th position of 18-MEA. The degree of water penetration into the fatty acid layer at the various separation distances was also investigated. Our simulations suggest that the optimal spacing for the fatty acids is between 0.492 and 0.651 nm, in contrast to the generally accepted literature value of around 0.9-1.0 nm. This results in a packing density of between 0.21 and 0.37 nm(2) per fatty acid molecule and a thickness of around 2.01-2.64 nm. We also show that, at larger separation distances, the 18-MEA fatty acid provides a slightly better hydrophobic layer than the EA fatty acid, suggesting that the 18-MEA fatty acid may have been naturally selected to provide better protection for the hair when it loses some of the fatty acids due to daily wear and tear. To our knowledge, this is the first attempt to systematically investigate the hair surface structure and properties with molecular simulations.

Synchrotron FTIR microscopy of Langmuir-Blodgett monolayers and polyelectrolyte multilayers at the solid-solid interface.

Synchrotron FTIR microscopy has been used to probe the structure of model boundary lubricant layers confined at the solid-solid interface. The combination of high brightness of the IR source and a novel contact geometry that uses a hemispherical internal reflection element as the means for light delivery has enabled the detection of <2.5 nm thin monolayer lubricant layers in the solid-solid contact, in addition to allowing for spectral acquisition from specific regions of the contact. Spectra of hydration water from within a confined polyelectrolyte multilayer film have also been acquired, highlighting the altered hydrogen bonding environment within the polymer layer.

Molecular depth profiling of buried lipid bilayers using C(60)-secondary ion mass spectrometry.

An organic delta layer system made of alternating Langmuir-Blodgett multilayers of barium arachidate (AA) and barium dimyristoyl phosphatidate (DMPA) was constructed to elucidate the factors that control depth resolution in molecular depth profile experiments. More specifically, one or several bilayers of DMPA (4.4 nm) were embedded in relatively thick (51 to 105 nm) multilayer stacks of AA, resulting in a well-defined delta layer model system closely resembling a biological membrane. 3-D imaging time-of-flight secondary ion mass spectrometry (TOF-SIMS) depth profile analysis was performed on this system using a focused buckminsterfullerene (C(60)) cluster ion beam. The delta layer depth response function measured in these experiments exhibits similar features as those determined in inorganic depth profiling, namely an asymmetric shape with quasi-exponential leading and trailing edges and a central Gaussian peak. The effects of sample temperature, primary ion kinetic energy, and incident angle on the depth resolution were investigated. While the information depth of the acquired SIMS spectra was found to be temperature independent, the depth resolution was found to be significantly improved at low temperature. Ion induced mixing is proposed to be largely responsible for the broadening, rather than topography, as determined by atomic force microscopy (AFM); therefore, depth resolution can be optimized using lower kinetic energy, glancing angle, and liquid nitrogen temperature.

The role of prenucleation clusters in surface-induced calcium phosphate crystallization.

Unravelling the processes of calcium phosphate formation is important in our understanding of both bone and tooth formation, and also of pathological mineralization, for example in cardiovascular disease. Serum is a metastable solution from which calcium phosphate precipitates in the presence of calcifiable templates such as collagen, elastin and cell debris. A pathological deficiency of inhibitors leads to the uncontrolled deposition of calcium phosphate. In bone and teeth the formation of apatite crystals is preceded by an amorphous calcium phosphate (ACP) precursor phase. ACP formation is thought to proceed through prenucleation clusters--stable clusters that are present in solution already before nucleation--as was recently demonstrated for CaCO(3) (refs 15,16). However, the role of such nanometre-sized clusters as building blocks for ACP has been debated for many years. Here we demonstrate that the surface-induced formation of apatite from simulated body fluid starts with the aggregation of prenucleation clusters leading to the nucleation of ACP before the development of oriented apatite crystals.

The Langmuir-Blodgett technique as a tool for homeotropic alignment of fluorinated liquid crystals mixed with arachidic acid.

Some fluoro-substituted liquid crystals mixed with arachidic acid in monolayers formed at air-liquid (Langmuir films) and air-solid substrate (Langmuir-Blodgett films) interfaces were investigated. Molecular organization in Langmuir films was determined on the basis of the analysis of the shape of the surface pressure-mean molecular area isotherm and observations made by means of a Brewster angle microscope. It was found that in the compression process the liquid crystal molecules are pushed out towards the top of the first monolayer being in direct contact with the subphase. Langmuir films were transferred onto the quartz substrates at various surface pressures and mono- and multilayered Langmuir-Blodgett films were obtained. The films were characterized using electronic absorption measurements. The conditions for obtaining the homeotropic orientation of the liquid crystal molecules were determined.

Role of epoxyeicosatrienoic acids as autocrine metabolites in glutamate-mediated K+ signaling in perivascular astrocytes.

Epoxyeicosatrienoic acids (EETs), synthesized and released by astrocytes in response to glutamate, are known to play a pivotal role in neurovascular coupling. In vascular smooth muscle cells (VSMC), EETs activate large-conductance, Ca(2+)-activated K(+) (BK) channels resulting in hyperpolarization and vasodilation. However, the functional role and mechanism of action for glial-derived EETs are still to be determined. In this study, we evaluated the effect of the synthetic EET analog 11-nonyloxy-undec-8(Z)-enoic acid (NUD-GA) on outward K(+) currents mediated by calcium-activated K(+) channels. Addition of NUD-GA significantly increased intracellular Ca(2+) and outward K(+) currents in perivascular astrocytes. NUD-GA-induced currents were significantly inhibited by BK channel blockers paxilline and tetraethylammonium (TEA) (23.4 ± 2.4%; P < 0.0005). Similarly, NUD-GA-induced currents were also significantly inhibited in the presence of the small-conductance Ca(2+)-activated K(+) channel inhibitor apamin along with a combination of blockers against glutamate receptors (12.8 ± 2.70%; P < 0.05). No changes in outward currents were observed in the presence of the channel blocker for intermediate-conductance K(+) channels TRAM-34. Blockade of the endogenous production of EETs with N-methylsulfonyl-6-(2-propargyloxyphenyl)hexanamide (MS-PPOH) significantly blunted (dl)-1-aminocyclopentane-trans-1,3-dicarboxylic acid (t-ACPD)-induced outward K(+) currents (P < 0.05; n = 6). Both NUD-GA and t-ACPD significantly increased BK channel single open probability; the later was blocked following MS-PPOH incubation. Our data supports the idea that EETs are potent K(+) channel modulators in cortical perivascular astrocytes and further suggest that these metabolites may participate in NVC by modulating the levels of K(+) released at the gliovascular space.

Phosphatidylglucoside forms specific lipid domains on the outer leaflet of the plasma membrane.

Phosphatidylglucoside (PtdGlc) is a recently discovered unique glycophospholipid involved in granulocytic differentiation of human promyelocytic leukemia cell line HL60 and in astrocytic differentiation in developing rodent brains. Using a PtdGlc-specific monoclonal antibody in immunofluorescence and immunoelectron microscopy, we showed that PtdGlc forms distinct lipid domains on the outer leaflet of the plasma membrane of HL60 cells and the human alveolar epithelial cell line, A549. Similar to glycosphingolipid, glucosylceramide (GlcCer), the natural form of PtdGlc exhibited a high main phase transition temperature in differential scanning calorimetry (DSC). However, unlike GlcCer, PtdGlc did not exhibit a large difference in the main phase transition temperature between the heating and cooling scans. DSC further indicated that GlcCer, but not PtdGlc, was miscible with sphingomyelin. In addition, DSC and small-angle X-ray scattering (SAXS) experiments revealed that PtdGlc was poorly miscible with phosphatidylcholine. Our results suggest that the lack of tight intermolecular interaction excludes PtdGlc from other lipid domains on the plasma membrane.

Fast diffusion of very long chain saturated fatty acids across a bilayer membrane and their rapid extraction by cyclodextrins: implications for adrenoleukodystrophy.

Abnormalities in the transport of saturated very long chain fatty acids (VLCFA; >C18:0) contribute to their toxic levels in peroxisomal disorders of fatty acid metabolism, such as adrenoleukodystrophy and adrenomyeloneuropathy. We previously showed that VLCFA desorb much slower than normal dietary fatty acids from both albumin and protein-free lipid bilayers. The important step of transbilayer movement (flip-flop) was not measured directly as a consequence of this very slow desorption from donors, and the extremely low aqueous solubility of VLCFA precludes addition of unbound VLCFA to lipid membranes. We have overcome these limitations using methyl-beta-cyclodextrin to solubilize VLCFA for rapid delivery to "acceptor" phosphatidylcholine vesicles (small and large unilamellar) and to cells. VLCFA binding was monitored in real time with the fluorescent probe fluorescein-labeled phosphatidylethanolamine in the outer membrane leaflet, and entrapped pyranine was used to detect flip-flop across the membrane. The upper limit of the rate of flip-flop across the membrane was independent of temperature and media viscosity and was similar for model raft and non-raft membranes as well as living cells. We further showed that cyclodextrins can extract VLCFA rapidly (within seconds) from vesicles and cells, which have implications for the mechanism and potential alternative approaches to treat adrenoleukodystrophy. Because VLCFA diffuse through the lipid bilayer, proteins may not be required for their transport across the peroxisomal membrane.

The thickness of 18-MEA on an ultra-high-sulfur protein surface by molecular modeling.

The use of computational chemistry techniques via molecular modeling software provides additional support to the hair surface model by Negri et al. (1) and refines the thickness of the 18-methyl eicosanoic acid (18-MEA) lipid layer attached by thioester linkages to an ultra-high-sulfur protein (UHSP) at 1.08 ± 0.2 nm. This value compares favorably to the thickness of that same layer from X-ray photoelectron spectroscopy (XPS) measurements by Ward et al. (2) at 1.00 ± 0.5 nm on Soxhlet-extracted wool. The model clarifies that the results of Ward et al. via XPS are not an artifact of high vacuum (3), but due to relaxation of the 18-MEA structure onto the wool protein backbone as suggested by Zahn et al. (4). In this molecular model, 18-MEA is attached to beta sheets of an UHSP via thioester linkages as suggested by Negri et al. in their 1993 study (15) and by earlier work by Evans et al. (5). The beta sheets of this model provide an intersheet spacing of 0.7 nm and a beta sheet density of 1.42 g/cm(3) compared with Allworden membrane fractions that varied from 1.39 to 1.54 g/cm(3) (6).

Anti-Inflammatory and Analgesic Effect of Arachic Acid Ethyl Ester Isolated from Propolis.

Inflammatory diseases are a real public health problem worldwide. Many synthetic drugs used in the treatment of inflammatory diseases such as steroidal anti-inflammatory drugs, nonsteroidal anti-inflammatory drugs (NSAIDs) and immunosuppressive drugs have harmful side effects. However, there are natural products like propolis, which is traditionally used in the treatment of pain. The objective of this work was to evaluate the anti-inflammatory and analgesic activities of the ethyl ester of arachic acid, a compound isolated from Cameroonian propolis. The ethyl ester of arachic acid was isolated by chromatography of the ethanolic extract of propolis harvested at Tala-Mokolo (Far North Region of Cameroon) and identified by nuclear magnetic resonance (NMR) spectra and the 1H-1H correlated spectroscopy. The anti-inflammatory and analgesic properties of oral administration of arachic acid ethyl ester (12.5, 25.0, and 50.0 mg/kg bw) were evaluated using carrageenan-induced paw edema, xylene-induced ear edema, cotton pellets-induced granuloma formation, and hot plate test in rat. Arachic acid ethyl ester produced maximum inhibition at 50.0 mg/kg for carrageenan-induced paw edema (62.5%), xylene-induced ear edema (54.5%), cotton pellet-induced granuloma (47.4%), and increased mean latency for hot plate test in rats. These results show clearly that the arachic acid ethyl ester has acute and chronic anti-inflammatory properties as well as central analgesic properties. This justifies the use of propolis in the treatment of pain in traditional medicine.

A function of lung surfactant protein SP-B.

The primary function of lung surfactant is to form monolayers at the alveolar interface capable of lowering the normal surface tension to near zero. To accomplish this process, the surfactant must be capable of maintaining a coherent, tightly packed monolayer that avoids collapse during expiration. The positively charged amino-terminal peptide SP-B1-25 of lung surfactant-specific protein SP-B increases the collapse pressure of an important component of lung surfactant, palmitic acid (PA), to nearly 70 millinewtons per meter. This alteration of the PA isotherms removes the driving force for "squeeze-out" of the fatty acids from the primarily dipalmitoylphosphatidylcholine monolayers of lung surfactant. An uncharged mutant of SP-B1-25 induced little change in the isotherms, suggesting that a specific charge interaction between the cationic peptide and the anionic lipid is responsible for the stabilization. The effect of SP-B1-25 on fatty acid isotherms is remarkably similar to that of simple poly-cations, suggesting that such polymers might be useful as components of replacement surfactants for the treatment of respiratory distress syndrome.

Strained-layer van der Waals epitaxy in a Langmuir-Blodgett film.

Atomic force microscope images of Langmuir-Blodgett films of lead and manganese fatty acid salts show that these monolayers have long-range order and are oriented with respect to the mica substrate, although the lattice symmetries of the monolayers and substrate are dramatically different. The surface lattice of sequentially thicker films evolves toward the bulk structure while retaining the substrate alignment. This behavior is in distinct contrast to films of cadmium fatty acid salts on mica, or all films on amorphous silicon oxide, in which the monolayer structure is disordered and a three-layer-thick film displays the bulk structure.

Stable ordering in Langmuir-Blodgett films.

Defects in the layering of Langmuir-Blodgett (LB) films can be eliminated by depositing from the appropriate monolayer phase at the air-water interface. LB films deposited from the hexagonal phase of cadmium arachidate (CdA2) at pH 7 spontaneously transform into the bulk soap structure, a centrosymmetric bilayer with an orthorhombic herringbone packing. A large wavelength folding mechanism accelerates the conversion between the two structures, leading to a disruption of the desired layering. At pH > 8.5, though it is more difficult to draw LB films, almost perfect layering is obtained due to the inability to convert from the as-deposited structure to the equilibrium one.

Conformations and coherences in structure determination by ultrafast electron diffraction.

In this article we consider consequences of spatial coherences and conformations in diffraction of (macro)molecules with different potential energy landscapes. The emphasis is on using this understanding to extract structural and temporal information from diffraction experiments. The theoretical analysis of structural interconversions spans an increased range of complexity, from small hydrocarbons to proteins. For each molecule considered, we construct the potential energy landscape and assess the characteristic conformational states available. For molecules that are quasiharmonic in the vicinity of energy minima, we find that the distinct conformer model is sufficient even at high temperatures. If, however, the energy surface is either locally flat around the minima or the molecule includes many degrees of conformational freedom, a Boltzmann ensemble must be used, in what we define as the pseudoconformer approach, to reproduce the diffraction. For macromolecules with numerous energy minima, the ensemble of hundreds of structures is considered, but we also utilize the concept of the persistence length to provide information on orientational coherence and its use to assess the degree of resonance contribution to diffraction. It is shown that the erosion of the resonant features in diffraction which are characteristic of some quasiperiodic structural motifs can be exploited in experimental studies of conformational interconversions triggered by a laser-induced temperature jump.

Effects of saturated and polyunsaturated fatty acids on interactions with cholesterol versus 7-ketocholesterol in Langmuir monolayers and their potential biological implications.

In this work the Langmuir monolayer technique was used to study interactions between cholesterol (chol) and 7-ketocholesterol (7-KC) with saturated (arachidic acid, AA) and polyunsaturated fatty acids (PUFAs) (ω-3 α-linolenic acid, α-LA,and ω-6 γ- linolenic, γ-LA) in order to get insight into their potential role in atherosclerosis. For this study, surface pressure (π)-area (A) isotherms, compressibility modulus (Cs-1) versus π plots, Brewster angle microscopy (BAM) images and excess functions (Aexc and ΔGexc) were analysed. Different behaviour has been observed. For cholesterol/AA mixed monolayers, components immiscibility occurs, whatever the surface pressure or the mixtures composition is, whereas for the 7-KC/AA mixed system, ideal behaviour was observed at low and high surface pressures for all the investigated compositions. However, the remaining mixed studied systems (sterol/PUFA) exhibit negative deviations from the ideality, although some differences do occurr. The magnitude of these deviations depend on the kind of a PUFA (for ω-3 PUFA greater than for ω-6) - attributed to the different geometry of their acyl chains- and the type of a sterol (for 7-KC greater than for cholesterol).The strength of attractive interactions followed the order: chol/ γ-LA <7-KC/γ-LA < chol/α-LA < 7-KC/ α-LA, postulating the formation of stable complexes of 1:2 stoichiometry for 7-KC/α-LA mixed monolayers and 1:1 stoichiometry for chol/α-LA mixed films. For 7-KC/γ-LA system, the formation of a low stability complex of 2:1 stoichiometry was suggested. The existence of these complexes can play an important role in diminishing the circulating sterols in the blood stream, thus decreasing the probability of atherosclerotic plaques formation.