Lipid Components Of Membranes Research Articles

Biophysical Insight on the Membrane Insertion of an Arginine-Rich Cell-Penetrating Peptide.

Cell-penetrating peptides (CPPs) are short peptides that can translocate and transport cargoes into the intracellular milieu by crossing biological membranes. The mode of interaction and internalization of cell-penetrating peptides has long been controversial. While their interaction with anionic membranes is quite well understood, the insertion and behavior of CPPs in zwitterionic membranes, a major lipid component of eukaryotic cell membranes, is poorly studied. Herein, we investigated the membrane insertion of RW16 into zwitterionic membranes, a versatile CPP that also presents antibacterial and antitumor activities. Using complementary approaches, including NMR spectroscopy, fluorescence spectroscopy, circular dichroism, and molecular dynamic simulations, we determined the high-resolution structure of RW16 and measured its membrane insertion and orientation properties into zwitterionic membranes. Altogether, these results contribute to explaining the versatile properties of this peptide toward zwitterionic lipids.

Arachidonic Acid Metabolism and Kidney Inflammation

As a major component of cell membrane lipids, Arachidonic acid (AA), being a major component of the cell membrane lipid content, is mainly metabolized by three kinds of enzymes: cyclooxygenase (COX), lipoxygenase (LOX), and cytochrome P450 (CYP450) enzymes. Based on these three metabolic pathways, AA could be converted into various metabolites that trigger different inflammatory responses. In the kidney, prostaglandins (PG), thromboxane (Tx), leukotrienes (LTs) and hydroxyeicosatetraenoic acids (HETEs) are the major metabolites generated from AA. An increased level of prostaglandins (PGs), TxA2 and leukotriene B4 (LTB4) results in inflammatory damage to the kidney. Moreover, the LTB4-leukotriene B4 receptor 1 (BLT1) axis participates in the acute kidney injury via mediating the recruitment of renal neutrophils. In addition, AA can regulate renal ion transport through 19-hydroxystilbenetetraenoic acid (19-HETE) and 20-HETE, both of which are produced by cytochrome P450 monooxygenase. Epoxyeicosatrienoic acids (EETs) generated by the CYP450 enzyme also plays a paramount role in the kidney damage during the inflammation process. For example, 14 and 15-EET mitigated ischemia/reperfusion-caused renal tubular epithelial cell damage. Many drug candidates that target the AA metabolism pathways are being developed to treat kidney inflammation. These observations support an extraordinary interest in a wide range of studies on drug interventions aiming to control AA metabolism and kidney inflammation.

PECULIARITIES OF FATTY ACID PROFILE OF ERYTHROCYTE MEMBRANES IN PATIENTS WITH RESISTANT ARTERIAL HYPERTENSION

Objective: This study aims to evaluate peculiarities of composition and level of fatty acids (FAs) in erythrocyte membranes (EM) of patients with resistant arterial hypertension (RAH) which could be applied in diagnosis of pathogenic aspects of the disease, development of new therapeutic targets. Design and method: 24 males with controlled arterial hypertension (CAH) (stage 1–2), 20 subjects with RAH (53 ± 5.7years), 22 healthy males were included into the study. The Agilent 7000B (USA) GC system was applied to study FAs composition. Results: The patients with CAH demonstrated increase in ratio of saturated, monoenoic FAs as well as decrease of polyenoic ones. Significant increase was registered in levels of C14:0, C17:0, C18:0, C20:0, C18:1 n9 (p = 0.01–0.05). We registered decrease in ratio of n6 unsaturated FAs: (C18:2, C20:4, C22:4) n6, (p = 0.01–0.05). Patients with RAH displayed increase in levels of C15:0, 16:0 FAs, oleic, midic ones (p = 0.03–0.05). The registered increased level of C20:3n9 would compensate synthesis which would take place in cases of deficit of n6, n3 polyunsaturated FAs (PUFA). Increase in ratio (C20:3/C18:1) n9 tends to evoke active synthesis of substrates for formation of prostacyclins, thromboxanes which are known to possess vasoconstrictive properties. Changes in PUFA tended to be most highly pronounced, especially in cases of n3 (C22:5, C22:6; p < 0.01). Patients with RAH demonstrated 2.1-time decrease of total n3 PUFA as compared to subjects with CAH. Increase of arachidonic acid level by up to 37.8% served as an outstanding finding in patients with RAH. That was the sign of deficit of n-3 PUFA. Disbalance in structure of n3, n6 was seen in decreased n3/n6 ratio (p < 0.01). Patients with RAH demonstrated accumulation of saturated, polyunsaturated n6 FA with deficit of n3 PUFA in EM. This speaks in favor of decrease in fluidity of cellular lipid bilayer, inhibition of binding ligands with the receptor, activity of enzymes bound with membrane, including PIEZO1,2 proteins (responsible for sensitivity to pressure). Conclusions: Increase in disorganization of lipid components of cellular membrane causes progression of hypertension with further development of resistant forms, what should be considered an important link in pathogenesis and target for therapy.

Inverse hexagonal phase of poly-unsaturated monogalactolipid: A computer model and analysis

Monogalactosylodiacylglycerol (MGDG) is the main lipid component of thylakoid membranes. In water, MGDG molecules pack preferentially in the hexagonal HII phase, which consists of water-filled lipid cylinders arranged in a hexagonal lattice. The HII phase can also form in the thylakoid membrane where it plays a key role in the photoprotection of the photosynthetic apparatus. In this study an all-atom computer model of the 16-cylinder MGDG HII phase was generated in a 3-μs molecular dynamics simulation and mathematical tools were developed to analyse its structural properties. The model-predicted values of the basic structural parameters, namely hexagonal spacing, circular and effective radii of the water channel, surface area/MGDG, and order parameters for the MGDG acyl chains, were compared with the experimental data available in the literature to validate the model. A stable computer model of the MGDG HII phase and the tools developed may serve further numerical experiments and investigations into the role of this phase in biological processes.

Lipasas de especies Candida: una revisión sobre aspectos bioquímicos, moleculares y patogénicos

In the last half century there was a significant increase in the incidence of fungal infections being likely to become a global health priority. The sophisticated degree of host-Candida interaction is the product of different virulence strategies used by the fungus to invade the tissues and the various defense mechanisms that it develops to control it. There is a significant amount of literature that indicates that this opportunistic commensal fungus has components that can be considered virulence factors related to the stage of the infectious process. Among the virulence factors of this fungus can be mentioned the adherence to cell surfaces, the formation of biofilms and the production of hydrolytic enzymes. The most studied hydrolases secreted by C. albicans are aspartyl proteinases, phospholipases and esterases, while lipases have been the least studied. These enzymes would have the function to facilitate active penetration into the cells, participating in the digestion and synthesis of lipid esters for their nutrition and contributing to the invasion of the tissue by hydrolyzing the lipid components of the host cell membranes. There is also bibliographic evidence that these enzymes are capable to damage cells and molecules of the immune system to avoid the antimicrobial activity.Taking into account the foregoing, this review provides an updated description of biochemical and molecular characteristics of the lipases secreted by Candida, its role as a virulence factor and its potential for the development of new antifungal drugs.

Milk Polar Lipids Reduce Atherogenic Lipoprotein Cholesterol and Attenuate Atherosclerosis Development in LDL-Receptor Knockout Mice Fed a Western-Type Diet (P06-051-19)

ObjectivesPurified milk sphingomyelin (SM), a polar lipid (PL) component of milk fat globule membranes, is protective against dyslipidemia in high-fat, diet-fed mice. However, it is unclear whether ingestion of the total milk PL fraction can have similar hypolipidemic effects as purified SM, and if this confers protection from inflammation and atherosclerosis. To determine this, LDLr-/- mice were fed high-fat, high-cholesterol diets with and without added milk PL from butter serum, a dairy co-product rich in PLs and SM. MethodsMale LDLr-/- mice (age 6 weeks) were fed ad libitum either a high-fat, high-cholesterol diet (CTL; 45% kcal from fat, 0.22% cholesterol added by weight; n = 15), or the same diet supplemented with 1% milk PL (1% MPL; n = 15) or 2% milk PL (2% MPL; n = 15) added by weight from butter serum. All diets were adjusted to match in energy density, macronutrient composition, and calcium content. After 14 weeks on diets, mice were fasted for 6 hours prior to blood and tissue collection/processing at sacrifice. ResultsSupplementation with 2% MPL significantly reduced serum cholesterol (–51%) compared to CTL (p < 0.01), with fast protein liquid chromatography (FPLC) showing dose-dependent effects in lowering VLDL- and LDL-cholesterol. Serum CCL2 was 56% lower in 2% MPL compared to CTL (p < 0.05). No other significant differences were found in serum markers of inflammation or insulin resistance. Compared to CTL, 2% MPL-fed mice had significantly lower mRNA expression of Scd1 and Mip1b in liver, and Ccl2 in epididymal adipose tissue (p < 0.05). Notably, milk PL dose-dependently reduced atherosclerosis development in thoracic aorta, with 2% MPL significantly lowering neutral lipid plaque size by 59% (p < 0.01). Ccl2 mRNA expression was also significantly reduced by 67% in the descending aorta with 2% MPL (p < 0.05). ConclusionsMilk PL strongly reduced atherogenic lipoprotein cholesterol in LDLr-/- mice fed a Western-type diet, and modestly lowered inflammatory markers in the serum, liver, adipose, and aorta. These factors likely contributed to the strong reduction in atherosclerosis development in thoracic aorta seen with 2% MPL. Milk PL content may be important to consider when choosing dairy products as food. Funding SourcesThis work was supported by a research grant to C. Blesso from the National Dairy Council.

Metabolomic Profiling and Lipid Composition of Arctic and Antarctic Strains of Micromycetes Geomyces pannorum and Thelebolus microsporus Grown at Different Temperatures

Adaptive reactions of Arctic and Antarctic strains of psychrophilic micromycetes Geomyces pannorum and Thelebolus microsporus to growth within a broad temperature range were studied. Adaptation of these species to different temperatures was found to result from both morphological and biochemical changes, including changes in the concentration of small molecules and lipid membrane components. These biochemical, morphological, and physiological mechanisms exhibited the patterns common to all strains, as well as species and strain differences. The general patterns included temperature-dependent changes in amounts of monosaccharides, some disaccharides, and free linoleic and linolenic acids. The differences between the Arctic and Antarctic strains were mainly associated with the differences in lipid composition, while interspecies differences resulted from metabolomic modifications. Antarctic strains showed lower ability to survive elevated temperatures, which correlated with weaker manifestation of the lipid-dependent adaptive mechanisms compared to the Arctic strains. Among the interstrain differences, higher growth parameters and mannitol accumulation were found in the Arctic isolates. Adaptation of T. microsporus was characterized by more diverse changes in the concentrations of small organic molecules in the metabolome profile and by pronounced changes in mycelial morphology. The results of metabolomic analysis and their subsequent treatment by the methods of multivariant statistics supported the suggestion of higher dispersion of metabolomic characteristics under unfavorable conditions and of lower dispersion of metabolomic data under optimal conditions.

Membrane effects of zinc oxide nanorods and nanoparticles in human lymphocytes

The study of the physical state of membrane lipids after the exposure of lymphocytes to ZnO NRs revealed a decrease in the lipid microviscosity of the hydrophilic membrane area and its increase in the hydrophobic area (external monolayer). The effects of ZnO NPs on membrane lipid components were not significant. Investigations of the membrane proteins conformation state revealed a rise of the protein NH 2 -groups level on the membrane surface only after the lymphocytes exposure to ZnO NRs. The level of SH-groups of the membrane protein after the action of ZnO NPs increased, otherwise the interaction of ZnO NRs with cells leads to the oxidation of thiol groups. According to the results of SEM, the geometric size of ZnO NPs did not exceed 30-100 nm, the diameter of ZnO NRs was 70-150 nm and the length - more than 500 nm. So the obtained results of toxicological tests can be partly explained by the possibility of ZnO NPs to enter into the cell but the most probable mechanisms for the NRs interaction with the cell are an electrostatic interaction or membrane puncturing.

Coacervation of Lipid Bilayer in Natural Cell Membranes for Extraction, Fractionation, and Enrichment of Proteins in Proteomics Studies.

This is the first report where hexafluoroisopropanol (HFIP) was used to induce the coacervation of lipid components in natural cell membranes that would concomitantly result in solubilization, extraction, and enrichment of hydrophobic proteins (e.g., integral membrane proteins, IMP) into the coacervate phase, and extraction of hydrophilic proteins in a separate aqueous phase. The incorporation of this innovative approach in the proteomics workflow would allow the fractionation of proteins in separate aqueous and coacervate phases and would also eliminate the need for using surfactants. Subsequently, proteins can be identified by the bottom-up proteomics approach where samples were digested in solution after phase separation. Yeast cell wall proteins, anchored membrane proteins, and proteins related to some regulatory activities were mostly found in the aqueous-rich phase. On the other hand, most integral membrane proteins, proteins involved in metabolic processes, and proteins responsible for ions or drug binding were identified in the coacervate phase. The detergent-free, facile, and rapid process of natural lipid coacervation increased the number of identified proteins by 8% (vs no-phase separation experiment). The identification of all IMPs and organelle IMPs was improved by 13% and 29%, respectively. In addition, 25% more low-abundance proteins (less than 20 ppm) were identified.

Human CFTR Channel Function is Regulated by Cholesterol

Cholesterol, a major membrane lipid component, has been known to modulate the function of multiple ion channels by specific lipid-protein interactions, by physical property changes of the membrane, or by modification of regulatory proteins associated with the channels in signaling complexes. Previous studies show that epithelial cells expressing the most common mutant version of the Cystic Fibrosis Transmembrane conductance Regulator (CFTR), F508del-CFTR, exhibit increased cholesterol content at the plasma membrane compared to wild type control cells; however, neutrophils derived from CF patients show reduced cholesterol levels in the plasma membrane. But whether cholesterol directly modulates CFTR channel function remains unknown. To answer this question, we combine heterologous expression in oocytes with more physiologically relevant Ussing chamber recordings utilizing polarized Fischer Rat Thyroid (FRT) cells to determine the effects of changing plasma membrane cholesterol levels on CFTR channel function. Here, we report that cholesterol depletion with methyl-β-cyclodextrin (MβCD) or cholesterol oxidase (CO) has no macroscopic effect on the magnitude of CFTR-mediated whole-oocyte currents. However, depletion of cholesterol increased the effect of VX-770, a clinically-used potentiator of CFTR, when channels were activated at high PKA concentrations, but did not change the effect of VX-770 when channels were activated at low PKA concentrations. This change in efficacy of VX-770-mediated potentiation likely reflects the apparent shift in the sensitivity of WT-CFTR to PKA after depletion of membrane cholesterol. In FRT cells, P67L-CFTR also exhibited changes in phosphorylation-dependent activation after depletion of plasma membrane cholesterol. Sensitivity of WT-CFTR to block by GlyH-101 was significantly stronger after plasma membrane cholesterol depletion. These results demonstrate that changes in the cholesterol level of the plasma membrane significantly modulate multiple CFTR channel functions. (Support: CF Fdn. MCCART17G0, NIH T32 GM008602, NIH F31 HL143863-01).

Determining the target of membrane sterols on voltage-gated potassium channels

Cholesterol, an essential lipid component of cellular plasma membranes, regulates fluidity, mechanical integrity, raft structure and may specifically interact with membrane proteins. Numerous effects on ion channels by cholesterol, including changes in current amplitude, voltage dependence and gating kinetics, have been reported. We have previously described such changes in the voltage-gated potassium channel Kv1.3 of lymphocytes by cholesterol and its analog 7-dehydrocholesterol (7DHC). In voltage-gated channels membrane depolarization induces movement of the voltage sensor domains (VSD), which is transmitted by a coupling mechanism to the pore domain (PD) to open the channel. Here, we investigated whether cholesterol effects were mediated by the VSD to the pore or the PD was the direct target. Specificity was tested by comparing Kv1.3 and Kv10.1 channels having different VSD-PD coupling mechanisms. Current recordings were performed with two-electrode voltage-clamp fluorometry, where movement of the VSDs was monitored by attaching fluorophores to external cysteine residues introduced in the channel sequence. Loading the membrane with cholesterol or 7DHC using methyl-β-cyclodextrin induced changes in the steady-state and kinetic parameters of the ionic currents while leaving fluorescence parameters mostly unaffected in both channels. Non-stationary noise analysis revealed that reduction of single channel conductance rather than that of open probability caused the observed current decrease. Furthermore, confocal laser scanning and stimulated emission depletion microscopy demonstrated significant changes in the distribution of these ion channels in response to sterol loading. Our results indicate that sterol-induced effects on ion channel gating directly target the pore and do not act via the VSD.

Patatin-like lipolytic acyl hydrolases and galactolipid metabolism in marine diatoms of the genus Pseudo-nitzschia

Diatoms are eukaryotic microalgae that play a pivotal role in biological and geochemical marine cycles. These microorganisms are at the basis of the trophic chain and their lipids are essential components (e.g. eicosapentaenoic acid, EPA) of aquatic food webs. Galactolipids are the primary lipid components of plastid membranes and form the largest lipid family of diatoms. As source of polyunsaturated fatty acids (PUFAs), these compounds are also involved in the synthesis of lipoxygenase (LOX) products such as non-volatile oxylipins and polyunsaturated aldehydes. Here, we report the first identification of two genes, namely PmLAH1 and PaLAH1, coding for lipolytic enzymes in two diatoms of the genus Pseudo-nitzschia. Functional and modeling studies evidence a patatin-like domain endowed with galactolipase and phospholipase activity at the C-terminus of both proteins. Homologues of Pseudo-nitzschia LAH1 genes were retrieved in other diatom species so far sequenced in agreement with conservation of the functional role of these proteins within the lineage.

Thylakoid membrane unstacking increases LHCII thermal stability and lipid phase fluidity.

Thylakoids are highly protein-enriched membranes that harbor a number of multicomponent photosynthetic complexes. Similarly to other biological membranes the protein constituents are heterogeneously distributed laterally in the plane of the membrane, however the specific segregation into stacked (grana patches) and unstacked (stroma lamellae) membrane layers is a unique feature of the thylakoid. Both the lateral and the vertical arrangements of the integral membrane proteins within the three-dimensional thylakoid ultrastructure are thought to have important physiological function. In this work we explore the role of membrane stacking for the thermal stability of the photosynthetic complexes in thylakoid membranes. By means of circular dichroism and differential scanning calorimetry we demonstrate that the thermal stability of the monomeric and trimeric forms of the major light harvesting complex of photosystem II (LHCII) increases upon unstacking. This effect was suggested to be due to the detachment of LHCII from photosystem II and consequent attachment to photosystem I subunits and/or the fluidization of the lipid matrix upon unstacking. The changes in the physical properties of the protein and lipid membrane components upon unstacking result in strongly reduced photosystem II excitation energy utilization.

Cholesterol and Cardiolipin Importance in Local Anesthetics\u2013Membrane Interactions: The Langmuir Monolayer Study

Local anesthetics (LAs) are known to act on membrane level; however, the molecular mechanism of their activity is still not fully understood. One hypothesis holds that these drugs can incorporate into lipid membrane of nerve cells and in this way change conformation of channel proteins responsible for transport of sodium ions. However, the action of anesthetics is not limited to nerve cells. These drugs also affect other types of cells and organelles, causing severe side effects. In this paper, we applied Langmuir monolayers—as model of cellular membranes—and investigated interactions between selected amide-type local anesthetics (lidocaine prilocaine, mepivacaine and ropivacaine, in the form of hydrochlorides) and lipid components of natural membranes: cholesterol, POPC and cardiolipin (CL) and their mixtures (POPC/cholesterol and POPC/CL/cholesterol), which can serve as simplified models of nerve cell membranes, erythrocytes, and mitochondria. The influence of the drug was monitored by registering the surface pressure (π) as a function of surface area per molecule (A) in a monolayer in the presence of the drug in the subphase. The structure of lipid monolayers on subphases containing and devoid of the studied drugs were visualized with Brewster angle microscopy (BAM). Langmuir monolayer studies complemented with surface visualization technique reveal the expansion and fluidization of lipid monolayers, with the most pronounced effect observed for cardiolipin. In mixed systems, the effect of LAs was found to depend on cholesterol proportion. The observed fluidization of membranes by local anesthetics may negatively affect cells functioning and therefore can explain side effects of these drugs both on the cardiovascular and nervous systems.

SIGNIFICANCE OF THE SPHINGOMYELIN CHANGES IN CORD BLOOD LYMPHOCYTES FOR THE ACTIVITY OF CENTRAL NERVOUS SYSTEM IN PRETERM NEWBORNS

Abstract.Different neuropsychical pathologies are revealed in preterm infants during the subsequent stages of ontogenesis. Violation of the phospholipids composition of cell membranes is one of the essential pathogenetic mechanisms of the psychoneurological pathology.Objective:to study the content of phospholipid fractions of cord blood lymphocytes in preterm infants at different gestation terms.The spectrumof phospholipids was determined by thin layer chromatography in 39 healthy full-term newborns and in 65 preterm children (28-36 weeks). We revealed an increased content of sphingomyelin in cord blood lymphocytes in preterm infants. The highest rates were found in children with a gestation term of less than 32 weeks (p = 0.004 compared with full-term infants). Sphingomyelin, unlike other phospholipids of cell membranes, is concentrated mainly in the brain, which indicates its special role for CNS activity.Recently, there has been formed the idea on the importance of lipid components of fat globule membranes of breast milk for optimal neurological development of children. Given the changes in the sphingomyelin content in the cell membranes of preterm newborns and its important structural and functional role for CNS activity, we believe that special attention should be paid to its content in the formulas for preterm infants among standard components.

A conserved motif promotes HpaB-regulated export of type III effectors from Xanthomonas.

SummaryThe type III secretion (T3S) system, an essential pathogenicity factor in most Gram‐negative plant‐pathogenic bacteria, injects bacterial effector proteins directly into the plant cell cytosol. Here, the type III effectors (T3Es) manipulate host cell processes to suppress defence and establish appropriate conditions for bacterial multiplication in the intercellular spaces of the plant tissue. T3E export depends on a secretion signal which is also present in ‘non‐effectors’. The latter are secreted extracellular components of the T3S apparatus, but are not translocated into the plant cell. How the T3S system discriminates between T3Es and non‐effectors is still enigmatic. Previously, we have identified a putative translocation motif (TrM) in several T3Es from Xanthomonas campestris pv. vesicatoria (Xcv). Here, we analysed the TrM of the Xcv effector XopB in detail. Mutation studies showed that the proline/arginine‐rich motif is required for efficient type III‐dependent secretion and translocation of XopB and determines the dependence of XopB transport on the general T3S chaperone HpaB. Similar results were obtained for other effectors from Xcv. As the arginine residues of the TrM mediate specific binding of XopB to cardiolipin, one of the major lipid components in Xanthomonas membranes, we assume that the association of T3Es to the bacterial membrane prior to secretion supports type III‐dependent export.

Attempt to Untangle the Prion-Like Misfolding Mechanism for Neurodegenerative Diseases.

The misfolding and aggregation of proteins is the neuropathological hallmark for numerous diseases including Alzheimer’s disease, Parkinson’s disease, and prion diseases. It is believed that misfolded and abnormal β-sheets forms of wild-type proteins are the vectors of these diseases by acting as seeds for the aggregation of endogenous proteins. Cellular prion protein (PrPC) is a glycosyl-phosphatidyl-inositol (GPI) anchored glycoprotein that is able to misfold to a pathogenic isoform PrPSc, the causative agent of prion diseases which present as sporadic, dominantly inherited and transmissible infectious disorders. Increasing evidence highlights the importance of prion-like seeding as a mechanism for pathological spread in Alzheimer’s disease and Tauopathy, as well as other neurodegenerative disorders. Here, we report the latest findings on the mechanisms controlling protein folding, focusing on the ER (Endoplasmic Reticulum) quality control of GPI-anchored proteins and describe the “prion-like” properties of amyloid-β and tau assemblies. Furthermore, we highlight the importance of pathogenic assemblies interaction with protein and lipid membrane components and their implications in both prion and Alzheimer’s diseases

Movement of giant lipid vesicles induced by millimeter wave radiation change when they contain magnetic nanoparticles.

Superparamagnetic iron oxide nanoparticles are used in a rapidly expanding number of research and practical applications in biotechnology and biomedicine. Recent developments in iron oxide nanoparticle design and understanding of nanoparticle membrane interactions have led to applications in magnetically triggered, liposome delivery vehicles with controlled structure. Here we study the effect of external physical stimuli-such as millimeter wave radiation-on the induced movement of giant lipid vesicles in suspension containing or not containing iron oxide maghemite (γ-Fe2O3) nanoparticles (MNPs). To increase our understanding of this phenomenon, we used a new microscope image-based analysis to reveal millimeter wave (MMW)-induced effects on the movement of the vesicles. We found that in the lipid vesicles not containing MNPs, an exposure to MMW induced collective reorientation of vesicle motion occurring at the onset of MMW switch "on." Instead, no marked changes in the movements of lipid vesicles containing MNPs were observed at the onset of first MMW switch on, but, importantly, by examining the course followed; once the vesicles are already irradiated, a directional motion of vesicles was induced. The latter vesicles were characterized by a planar motion, absence of gravitational effects, and having trajectories spanning a range of deflection angles narrower than vesicles not containing MNPs. An explanation for this observed delayed response could be attributed to the possible interaction of MNPs with components of lipid membrane that, influencing, e.g., phospholipids density and membrane stiffening, ultimately leads to change vesicle movement.

Old muscle in young body: an aphorism describing the Chronic Fatigue Syndrome.

The chronic fatigue syndrome (CFS) otherwise known as myalgic encephalomyelitis (ME), is a debilitating syndrome whose identification is very complex due to lack of precise diagnostic criteria. This pathology begins with limitations in duration and intensity of exercise and rapid onset of pain during physical activity. Its etiology is unknown, and symptoms are not limited to the muscles. Epidemiology is rather difficult to delimit, even if it affects mainly young (20-40 years), female subjects. The results of muscular research show some peculiarities that can justify what has been observed in vivo. In particular, 1. presence of oxidative damage of lipid component of biological membranes and DNA not compensated by the increase of the scavenger activity; 2. Excitation-Contraction (E-C) alteration with modification of Ca2+ transport; 3. passage from slow to fast fiber phenotype; 4. inability to increase glucose uptake; 5. presence of mitochondrial dysfunction; and 6. genes expressed differentially (particularly those involved in energy production). The skeletal muscles of CFS / ME patients show a significant alteration of the oxidative balance due to mitochondrial alteration and of the fiber phenotype composition as shown in sarcopenic muscles of the elderly. Vice versa, the muscle catabolism does not appear to be involved in the onset of this syndrome. The data support the hypothesis that patients with CFS are subjected to some of the problems typical for muscle aging, which is probably related to disorders of muscle protein synthesis and biogenesis of mitochondria. Patients with CFS can benefit from an appropriate training program because no evidence suggests that physical exercise worsens symptoms. Type, intensity and duration of any physical activity that activates muscle contraction (including Electrical Stimulation) require further investigation even if it is known that non-exhaustive physical activity decreases painful symptomatology.

Thermotropic phase behavior of milk sphingomyelin and role of cholesterol in the formation of the liquid ordered phase examined using SR-XRD and DSC

Sphingomyelin (SM) and cholesterol are major lipid components of biological membranes involved in the formation of ordered domains. In this study, we investigated the biophysical properties of milk-SM bilayers and determined the effect of cholesterol. The thermotropic phase behaviours of milk-SM and milk-SM/cholesterol mixtures were characterized using differential scanning calorimetry (DSC) and high flux synchrotron radiation X-ray diffraction (SR-XRD). The melting phase transition temperature determined for fully hydrated milk-SM bilayers was Tm = 34.3 ± 0.1 °C. The thermotropic phase behavior of milk-SM is complex, reflecting the mixture of different molecular species. Structural reorganisations successively occurring on heating of fully hydrated milk-SM bilayers were interpreted as follows: i) melting of C16:0-SM, ii) conversion of long and saturated SM species from fully interdigitated (Lβ1) to mixed interdigitated (Lβ2) lamellar structures evidencing gel phase polymorphism and then iii) transition to the fluid liquid-crystal Lα phase. We demonstrated that cholesterol modulates the physical properties of milk-SM bilayers and that building up of the lamellar liquid-ordered Lo phase is completed for 33 mol% of cholesterol. The ordering effect of cholesterol on milk-SM bilayers and the temperature-independent behavior of the Lo phase formed by milk-SM/cholesterol complexes were characterized. The findings of this work will contribute in a better understanding of the biological functions exerted by the milk-SM as a function of its phase state and interactions with cholesterol (e.g. hypocholesterolemic effect).