Unsaturated Phospholipids Research Articles

Combinatorial Action of Different Stress Factors on the Composition of Membrane Lipids and Osmolytes of Aspergillus niger

Adaptive response (changes in the composition of osmolytes and membrane lipids) of the mycelial fungus Aspergillus niger to combinatorial action of oxidative and heat (or osmotic) shocks was studied. Oxidative shock was found to cause no significant changes in the composition of osmolytes. A combination of oxidative shock with other stressors was shown to suppress their adaptive responses, such as accumulation of trehalose (during heat shock) and polyols (during osmotic shock). A common pattern of the changes in membrane lipids observed for all the studied stress factors was an increase in the proportion of non-bilayer phosphatidic acids, which was more pronounced in the case of combinatorial stress effects. No significant changes in the degree of unsaturation of membrane phospholipids were observed. Thus, the studied combinatorial shocks did not result in an additive response and caused a decrease in the amount of osmolytes compared with individual stressors, which weakened the adaptive response of the fungus.

In Situ Monitoring of the Unsaturated Phospholipid Monolayer Oxidation in Ambient Air by HD-SFG Spectroscopy

The pulmonary surfactant monolayer is indispensable for the respiratory system. Recently, it was reported that some unsaturated lipids of the pulmonary surfactants are oxidized by low-level ozone in ambient air. However, the molecular-level understanding of the reaction mechanism is still limited due to technical difficulties. We applied heterodyne-detected sum frequency generation (HD-SFG) spectroscopy to probe the reaction process of an unsaturated phospholipid monolayer (1-palmitoyl-2-oleoyl-glycero-3-phosphocholine, POPC), which is one of the major lipids in the pulmonary surfactant, under low-level ozone (30 ± 5 ppb). The HD-SFG spectroscopy realized the accurate peak assignments of the spectra and the identification of molecular species with high sensitivity, which were impossible with previous measurements. The time-resolved spectra indicated that the C═C moiety in the unsaturated alkyl chain is selectively oxidized by ozone with a time constant of 22 ± 3 min by first-order reaction kinetics. Furthermore, it was revealed for the first time that the reaction product of the POPC monolayer under low-level ozone is not the carboxylic form but the aldehyde form based on the vibrational spectroscopy results. The present study has deepened our molecular-level understanding of the oxidation mechanism of unsaturated lipids that are widely found in many biological systems.

Phase separation behavior of binary mixture of photopolymerizable diacetylene and unsaturated phospholipids in liposomes

Photopolymerizable lipids, such as diacetylene lipids have attracted much attention for their ability to stabilize lipid bilayer structure. In this study, we investigated the phase separation behavior of a lipid bilayer containing 1,2‑bis(10,12‑tricosadiynoyl)‑sn‑glycero‑3‑phosphocholine (DiynePC). The phase separation behavior of liposomes composed of DiynePC and the non-polymerizable lipid, 1,2‑dioleoyl‑sn‑glycero‑3‑phosphocholine (DOPC) was evaluated using a fluorescence resonance energy transfer (FRET) assay during both the cooling and heating processes. The polymerization behavior and orientation of DiynePC was evaluated by measuring the absorbance contributed by polymerized diacetylene groups. The main phase transition temperature (Tm) and orientation temperature (To) of DiynePC were determined from differential scanning calorimetry (DSC) and absorbance measurements. As a comparison, liposomes composed of 1,2‑dipalmitoyl‑sn‑glycero‑3‑phosphocholine (DPPC), which has a similar Tm as DiynePC, but a dissimilar To, were evaluated as well as, DiynePC-containing liposomes. The DPPC/DOPC liposomes showed phase separation at the Tm of DPPC during both the cooling and heating processes. On the other hand, the phase separation of the DiynePC/DOPC liposomes occurred near To of DiynePC but slightly increased during the cooling process. Interestingly, once the liposomes were cooled to a much lower temperature than the To, the phase separation was promoted by the subsequent heating process, and reached a maximum state of the phase separation near the To. These results indicated that the phase separation of DiynePC is affected by both the orientation state and thermal molecular motion.

2,4-dienoyl-CoA reductase regulates lipid homeostasis in treatment-resistant prostate cancer

Despite the clinical success of Androgen Receptor (AR)-targeted therapies, reactivation of AR signalling remains the main driver of castration-resistant prostate cancer (CRPC) progression. In this study, we perform a comprehensive unbiased characterisation of LNCaP cells chronically exposed to multiple AR inhibitors (ARI). Combined proteomics and metabolomics analyses implicate an acquired metabolic phenotype common in ARI-resistant cells and associated with perturbed glucose and lipid metabolism. To exploit this phenotype, we delineate a subset of proteins consistently associated with ARI resistance and highlight mitochondrial 2,4-dienoyl-CoA reductase (DECR1), an auxiliary enzyme of beta-oxidation, as a clinically relevant biomarker for CRPC. Mechanistically, DECR1 participates in redox homeostasis by controlling the balance between saturated and unsaturated phospholipids. DECR1 knockout induces ER stress and sensitises CRPC cells to ferroptosis. In vivo, DECR1 deletion impairs lipid metabolism and reduces CRPC tumour growth, emphasizing the importance of DECR1 in the development of treatment resistance.

Plasma membranes are asymmetric in lipid unsaturation, packing and protein shape.

SUMMARY:A fundamental feature of cellular plasma membranes (PM) is asymmetric lipid distribution between the bilayer leaflets. However, neither the detailed, comprehensive compositions of individual PM leaflets, nor how these contribute to structural membrane asymmetries have been defined. We report the distinct lipidomes and biophysical properties of both monolayers in living mammalian PMs. Phospholipid unsaturation is dramatically asymmetric, with the cytoplasmic leaflet being ~2-fold more unsaturated than the exoplasmic. Atomistic simulations and spectroscopy of leaflet-selective fluorescent probes reveal that the outer PM leaflet is more packed and less diffusive than the inner leaflet, with this biophysical asymmetry maintained in the endocytic system. The structural asymmetry of the PM is reflected in asymmetric structures of protein transmembrane domains (TMD). These structural asymmetries are conserved throughout Eukaryota, suggesting fundamental cellular design principles.

Essential oils and lipids from the flowers of two varieties of Ocimum basilicum L. cultivated in Uzbekistan

ABSTRACT In the current work the flowers of green and dark purple Ocimum basilicum L. varieties cultivated in Uzbekistan were comparatively studied in terms of chemical composition of the lipids, essential oils and fatty acids by using TLC, GC-FID and GC-MS techniques. The lipid composition of flowers both basil varieties comprised biologically active substances such as unsaturated fatty acids, phospholipids, phytosterols, carotenoid pigments and essential oils. The flower volatiles were obtained by hydrodistillation technique and subjected to GC analysis. Enantiomeric status of chiral volatile compounds was determined by analysis on chiral RTex cyclodextrin column. It is revealed that the flowers of green and dark purple basil produce essential oils with a high abundance of oxygenated monoterpenes with linalool (52.4% and 72.3%, respectively) as a major constituent. The flower volatiles from the green basil were distinct from that of dark purple variety, having strong sweet-spicy odor due to higher percentage of phenylpropanoid methyl chavicol (19.5%).

Ozonization of Tissue Sections for MALDI MS Imaging of Carbon-Carbon Double Bond Positional Isomers of Phospholipids.

Visualizing the differential distribution of carbon-carbon double bond (C═C db) positional isomers of unsaturated phospholipids (PL) in tissue sections by use of refined matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI MSI) technologies offers a high promise to deeper understand PL metabolism and isomer-specific functions in health and disease. Here we introduce an on-tissue ozonization protocol that enables a particular straightforward derivatization of unsaturated lipids in tissue sections. Collision-induced dissociation (CID) of MALDI-generated ozonide ions (with yields in the several ten percent range) produced the Criegee fragment ion pairs, which are indicative of C═C db position(s). We used our technique for visualizing the differential distribution of Δ9 and Δ11 isomers of phosphatidylcholines in mouse brain and in human colon samples with the desorption laser spot size 15 μm, emphasizing the potential of the technique to expose local isomer-specific metabolism of PLs.

The effect of vehicle on skin absorption of Mg2+ and Ca2+ from thermal spring water.

Thermal spring waters (TSW) are commonly used as active ingredients in cosmetics. Their biological activities directly depend on the ionic composition of the spring. However, in order to exhibit beneficial properties, the minerals need to reach viable skin layers. The present study addresses the incorporation of marketed TSW in model cosmetic formulations and the impact of the formulation on skin absorption of magnesium and calcium ions that are known to improve skin barrier function. Marketed TSW was introduced into five formulations. Liposomes were prepared using saturated or unsaturated phospholipids mixed with cholesterol by the thin layer evaporation technique. Emulsions water-in-oil (W/O), oil-in-water (O/W) or double: water-in-oil-in-water (W/O/W) were prepared by high-shear mixing. Skin absorption of Mg2+ and Ca2+ from those formulations was studied invitro using static Franz diffusion cells under infinite dose condition and under occlusion of the apparatus. Mg2+ and Ca2+ penetrate skin samples from TSW. Encapsulating TSW into double emulsion (TSW/O/W) increased skin absorption of both cations of interest and kept the Ca2+ /Mg2+ ratio equal to that of TSW in each skin layer. The dermal absorption of Mg2+ from the double emulsion departs from both single emulsions. Application of liposome suspension improved the skin absorption of Ca2+ while keeping constant that of Mg2+ , leading to unbalanced Ca2+ /Mg2+ ratio inside skin. The beneficial effects of TSW are not only due to their action on the skin surface. Their active components, especially Ca2+ and Mg2+ cations, reach viable skin layers in a formulation-dependent manner. The distribution of ions inside skin depends on the type of formulation.

Water-Intake and Water-Molecule Paths to the Active Site of Secretory Phospholipase A2 Studied Using MD Simulations and the Tracking Tool AQUA-DUCT.

Secretory phospholipases A2 (sPLA2s) are a subclass of enzymes that catalyze the hydrolysis at the sn-2 position of glycerophospholipids, producing free fatty acids and lysophospholipids. In this study, different phospholipids with structural modifications close to the scissile sn-2 ester bond were studied to determine the effect of the structural changes on the formation of the Michaelis-Menten complex and the water entry/exit pathways using molecular dynamics simulations and the computational tracking tool AQUA-DUCT. Structural modifications include methylation, dehydrogenation, and polarization close to the sn-2 scissile bond. We found that all water molecules reaching the active site of sPLA2-IIA pass by the aromatic residues Phe5 and Tyr51 and enter the active site through an active-site cleft. The relative amount of water available for the enzymatic reaction of the different phospholipid-sPLA2 complexes was determined together with the distance between key atoms in the catalytic machinery. The results showed that (Z)-unsaturated phospholipid is a good substrate for sPLA2-IIA. The computational results are in good agreement with previously reported experimental data on the ability of sPLA2-IIA to hydrolyze liposomes made from the different phospholipids, and the results provide new insights into the necessary active-site solvation of the Michaelis-Menten complex and can pave the road for rational design in engineering applications.

Droplet Interface Bilayers as a Physico-Chemical Tool to Assess and Investigate the Cellular Membrane Crossing of Small Molecules

The cell membrane interface separates the cellular milieu from the external environment. It is self-assembled as a bilayer and made of phospholipids, cholesterol and proteins. Its main purpose is to regulate chemical gradients between the inside and the outside of the cell. In the frame of pharmacology, understanding the process of drug permeation through the cell membrane is essential. In fact, medicines that feature a poor ability to cross bilayers often fail during the development thread. Therefore, this question is both of research interest and highly valued by the pharmaceutical industry. Several methods have been developed to evaluate the ability of a drug to cross membranes. Design of artificial membrane systems that best mimic that of real cells has come as a good option to reach this objective. However, a clear knowledge of the physical chemistry properties of the produced bilayer is still lacking. Consequently, the main screening technologies mis-predicted drugs permeability. Here, we tackle this question by studying the permeation of fluorophores through droplet interface bilayers (DIBs) made of a range of phospholipids and solvents. We find that both acyl chains and polar heads could independently affect the permeability of artificial bilayers. Our findings offer a clearer understanding of the contribution of phospholipid unsaturation, charge, and shape in membrane permeability. All these parameters alter membrane lateral pressure, i.e. membrane phospholipid packing level, which we identify as a major determinant in membrane permeability. We thereupon determine relevant physical chemistry conditions that properly mimic biological membranes.

Identifying Double Bond Positions in Phospholipids Using Liquid Chromatography-Triple Quadrupole Tandem Mass Spectrometry Based on Oxygen Attachment Dissociation.

Lipids, a class of biomolecules, play a significant role in the physiological system. In this study, gas-phase hydroxyl radicals (OH·) and atomic oxygens (O) were introduced into the collision cell of a triple quadruple mass spectrometer (TQ-MS) to determine the positions of the double bond in unsaturated phospholipids. A microwave-driven compact plasma generator was used as the OH·/O source. The reaction between OH·/O and the precursor ions passing through the collision cell generates product ions that correspond to the double bond positions in the fatty acyl chain. This double bond position specific fragmentation process initiated by the attachment of OH·/O to the double bond of a fatty acyl chain is a characteristic of oxygen attachment dissociation (OAD). A TQ-MS incorporating OAD, in combination with liquid chromatography, permitted a high throughput analysis of the double bond positions in complex biomolecules. It is important to know the precise position of double bonds in lipids, since these molecules can have widely different functionalities based on the position of the double bonds. The assignment of double bond positions in a mixture of eight standard samples of phosphatidylcholines (phospholipids with choline head groups) with multiple saturated fatty acyl chains attached was successfully demonstrated.

2 H NMR of oriented phospholipid/cholesterol bilayers containing an amphiphilic peptide

Lipid bilayers form the basis of cell membranes and the phase behaviour of the membrane has been linked to proper cell function. Model membranes composed of relatively simple mixtures of phospholipids and cholesterol can already exhibit complex phase behaviour. Specifically, liquid ordered–liquid disordered fluid phase coexistence occurs in mixtures which contain one saturated long chain phospholipid and one unsaturated long chain phospholipid and cholesterol. This fluid-fluid two phase region persists over a broad range of temperatures and sample compositions and can be observed experimentally in various sample preparations including multilamellar dispersions, bicelles, and multi-lamellae stacked on glass slides. In order to explore the practicality of using oriented samples with different concentrations of the peptide, we investigated the effect of the addition of a synthetic 22 residue amphiphilic peptide on the orientability and phase behaviour of the lipid mixtures, as well as the orientation and dynamics of the peptide itself via 2H NMR. Increasing the peptide concentration promoted the formation of the liquid ordered phase, suggesting a preferential interaction of the peptide with the thicker ordered phase. However, higher peptide content (> 4 mol%) had a significant negative effect on the alignment of bicelles with their bilayer normal perpendicular to the external magnetic field. In the stacked bilayer samples, 6 mol% peptide eliminated the two phase coexistence region altogether and a single liquid ordered phase was observed from 285 to 311 K. Even so, 2H spectra of the peptide itself did not reveal any preference for the peptide to partition into either the liquid disordered or liquid ordered phase and we found two populations of the peptide, one which undergoes rapid axial reorientation about the bilayer normal and a second (powder component) which does not.

Interaction of amphotericin B and saturated or unsaturated phospholipid monolayers containing cholesterol or ergosterol at the air-water interface

The antimicrobial activity of amphotericin B (AmB) depends on its interaction with ergosterol-containing cell membranes of fungus. Cholesterol is a sterol in mammalian cell membrane, and its structure is very similar to ergosterol, which caused to the toxic of amphotericin B to mammalian or human cell membranes. Even so, it is still the gold standard for the treatment of fungal infections. The mechanism of its toxicity to mammalian cell membrane has become a hot topic. The toxicity mechanism of amphotericin B on the cell membrane is also related to the phospholipids on the membrane. The effects of saturated and unsaturated fat chains on the interaction of amphotericin B with phospholipid monolayers containing cholesterol or ergosterol were studied at the molecular level using an air-water interface monolayer model. Both atomic force microscope and Brewster angle microscope were used to observe the surface morphology of the monolayer. The analysis of limiting molecular area suggested that the interaction between AmB and the two kinds of sterol is significantly different on the unsaturated lipid monolayer. According to the elastic modulus, the AmB molecules can increase the compressibility or viscoelasticity of the phospholipid/sterol monolayer. However, this impact of AmB on the DOPC/sterol monolayer containing ergosterol was stronger than that containing cholesterol at 25 ~ 50 mN/m. While this impact of AmB on the DPPC/sterol monolayer containing cholesterol was stronger than that containing ergosterol at 32 ~ 56 mN/m. The excess Gibbs free energy of the monolayer showed that, in the presence of saturated fat chain, amphotericin B could make the molecules of the DPPC/cholesterol monolayer and the DPPC/ergosterol monolayer arrange more closely and make intermolecular interaction stronger. There was no significant difference between DPPC/cholesterol monolayer and DPPC/ergosterol monolayer. However, in the presence of unsaturated chain, the effects of amphotericin B on the DOPC/cholesterol monolayer and the DOPC/ergosterol monolayer were significantly different. Amphotericin B made the molecular arrangement of DOPC/ergosterol monolayer more loosed, and the intermolecular force weakened at 5-35 mN/m. AFM images reflect that AmB can perforate the phospholipid-ergosterol monolayer, which was no significant correlation with saturation of the lipid monolayer. But the areas of dark areas shaped holes on the DPPC/ergosterol monolayer were larger than that on the DOPC/ergosterol monolayer. The adsorption of amphotericin B on lipid/sterol monolayer suggests that the orientation of amphotericin B may be different when it is inserted into the monolayer of phospholipid-sterol in the presence of saturated or unsaturated chains. The results are helpful to understand the complex mechanism of toxicity of amphotericin B to cell membrane.

Thermodynamic Analysis of Myelin Basic Protein Adsorbed on Liquid Crystalline Dioleoylphosphatidylcholine Monolayer.

To investigate the stability and dynamic characteristics of monolayer adsorbed on unsaturated lipid dioleoylphosphatidylcholine (DOPC) with varying concentrations of myelin basic protein (MBP), the system is studied by applying Langmuir technique and making atomic force microscope (AFM) observation, which is based on the mass conservation equation analysis method referred to in the thermodynamics theory. As indicated by surface pressure-mean molecular area (π − A) and surface pressure-adsorption time (π − T) isotherms, the physical properties of monolayer derived from the interaction of varying concentrations of MBP with liquid crystalline unsaturated lipid DOPC molecules were qualitatively studied. As revealed by surface morphology analysis with AFM, the micro region was expanded as the concentration of MBP in the subphase was on the increase, suggesting that hydrophobic interactions led to the MBP insertion, thus causing accumulation of the MBP on the surface of the monolayer. Experimental results have demonstrated that the partition coefficient of the interaction between MBP and unsaturated phospholipid DOPC and the molecular area of MBP adsorbed on the monolayer film was calculated using the mass conservation equation. In addition, not only does the varying concentration of MBP in the subphase exerts significant effects on the arrangement and conformation of DOPC monolayer, it also has certain guiding significance to exploring the structural changes to biofilm supramolecular aggregates as well as the pathogenesis and treatment of related diseases.

Metabolite-related dietary patterns and the development of islet autoimmunity

The role of diet in type 1 diabetes development is poorly understood. Metabolites, which reflect dietary response, may help elucidate this role. We explored metabolomics and lipidomics differences between 352 cases of islet autoimmunity (IA) and controls in the TEDDY (The Environmental Determinants of Diabetes in the Young) study. We created dietary patterns reflecting pre-IA metabolite differences between groups and examined their association with IA. Secondary outcomes included IA cases positive for multiple autoantibodies (mAb+). The association of 853 plasma metabolites with outcomes was tested at seroconversion to IA, just prior to seroconversion, and during infancy. Key compounds in enriched metabolite sets were used to create dietary patterns reflecting metabolite composition, which were then tested for association with outcomes in the nested case-control subset and the full TEDDY cohort. Unsaturated phosphatidylcholines, sphingomyelins, phosphatidylethanolamines, glucosylceramides, and phospholipid ethers in infancy were inversely associated with mAb+ risk, while dicarboxylic acids were associated with an increased risk. An infancy dietary pattern representing higher levels of unsaturated phosphatidylcholines and phospholipid ethers, and lower sphingomyelins was protective for mAb+ in the nested case-control study only. Characterization of this high-risk infant metabolomics profile may help shape the future of early diagnosis or prevention efforts.

Mapping lipid C=C location isomers in organ tissues by coupling photochemical derivatization and rapid extractive mass spectrometry

Lipid desaturation plays important roles in biological processes and the disease states. Here, we report a simple but efficient method for mapping unsaturated phospholipids including the spatial distribution of lipid C=C location isomers in animal organs by coupling the C=C specific derivatization with direct analysis mass spectrometry (MS). Lipids are sampled directly by a stainless-steel wire from rat brain or kidney, extracted, and derivatized via the Paternò–Büchi reaction in a glass emitter of the nanoelectrospray ionization (nanoESI) source. Subsequent analysis by nanoESI-tandem mass spectrometry reveals C=C locations and relative quantities of lipid C=C location isomers. Unsaturated lipids, such as phospholipids and free fatty acids, have been identified with ion intensities spanning two orders of magnitude in rat brain. Typical sample consumption is less than 10 μg/measurement and the time for each analysis is about 3 min. This method should serve as a complementary method to high spatial resolution mass spectrometry imaging techniques, because it offers a streamlined experimental workflow for rapid profiling of lipids with C=C specificity to enable such applications as point-of-care disease diagnostics.

Excitation of Fluorescent Lipid Probes Accelerates Supported Lipid Bilayer Formation via Photosensitized Lipid Oxidation.

Fluorescent lipid probes are commonly used to label membranes of cells and model membranes like giant vesicles, liposomes, and supported lipid bilayers (SLB). Here, we show that excitation of fluorescent lipid probes with BODIPY-like conjugates results in a significant acceleration of the rupture and SLB formation process for unsaturated phospholipid vesicles on SiO2 surfaces. The resulting SLBs also have smaller measured masses, which is indicative of a reduction in membrane thickness and/or membrane density. The excitation of fluorescent probes with NBD and Texas Red conjugates does not accelerate the SLB formation process. In the absence of fluorescent probes or light, the inclusion of oxidized phospholipids also accelerates SLB formation. The excitation-induced acceleration caused by BODIPY-like probes is eliminated when the probes are present with saturated phospholipids not susceptible to oxidation, and it is attenuated when a lipophilic antioxidant (α-tocopherol) is present. These results suggest that BODIPY-phospholipid conjugates are photosensitizers, and their excitation causes oxidation of lipid membranes, which significantly alters membrane properties.

Long-chain acyl-CoA synthetase 4 participates in the formation of highly unsaturated fatty acid-containing phospholipids in murine macrophages

Long-chain acyl-coenzyme A synthetases (ACSLs) are a family of enzymes that convert free long-chain fatty acids into their acyl-coenzyme A (CoA) forms. ACSL4, belonging to the ACSL family, shows a preferential use of arachidonic acid (AA) as its substrate and plays a role in the remodeling of AA-containing phospholipids by incorporating free AA. However, little is known about the roles of ACSL4 in inflammatory responses. Here, we assessed the roles of ACSL4 on the effector functions of bone marrow-derived macrophages (BMDMs) obtained from mice lacking ACSL4. Liquid chromatography–tandem mass spectrometry analysis revealed that various highly unsaturated fatty acid (HUFA)-derived fatty acyl-CoA species were markedly decreased in the BMDMs obtained from ACSL4-deficient mice compared with those in the BMDMs obtained from wild-type mice. BMDMs from ACSL4-deficient mice also showed a reduced incorporation of HUFA into phosphatidylcholines. The stimulation of BMDMs with lipopolysaccharide (LPS) elicited the release of prostaglandins (PGs), such as PGE2, PGD2 and PGF2α, and the production of these mediators was significantly enhanced by ACSL4 deficiency. In contrast, neither the LPS-induced release of cytokines, such as IL-6 and IL-10, nor the endocytosis of zymosan or dextran was affected by ACSL4 deficiency. These results suggest that ACSL4 has a crucial role in the maintenance of HUFA composition of certain phospholipid species and in the incorporation of free AA into the phospholipids in LPS-stimulated macrophages. ACSL4 dysfunction may facilitate inflammatory responses by an enhanced eicosanoid storm.

Fourier transform infrared spectroscopic signature of blood plasma in the progression of breast cancer with simultaneous metastasis to lungs.

Despite advanced diagnostic techniques used for detecting cancer, this disease still remains a leading cause of death in the developed world. What is more, the greatest danger for patients is not related with growing of tumor but rather with metastasis of cancer cells to the distant organs. In this study, Fourier transform infrared (FTIR) spectroscopy was used to track chemical changes in blood plasma to find spectral markers of metastatic breast cancer during the disease progression. Plasma samples were taken 1-5 weeks after orthotropic inoculation of 4T1 metastatic breast cancer cells to mice. The earliest changes detected by FTIR spectroscopy in plasma were correlated with unsaturation of phospholipids and secondary structures of proteins that appeared 2 and 3 weeks, respectively, after 4T1 cells inoculation (micrometastatic phase). Significant alternations in the content and structure of lipids and carbohydrates were identified in plasma at the later stages (macrometastatic phase). When large primary tumors in breast and macrometastases in lung were developed, all bands in FTIR spectra significantly differed from those at earlier phases of the cancer progression. In conclusion, we showed that each phase of the breast cancer progression and its pulmonary metastasis can be characterized by a specific panel of spectral markers.

Ergosterol-Induced Ordered Phase in Ternary Lipid Mixture Systems of Unsaturated and Saturated Phospholipid Membranes.

The sterol ergosterol (Erg) is ubiquitous in the membranes of lower eukaryotes such as fungi. To investigate the interactions between Erg and phosphocholine (PC) molecules, we studied ternary lipid mixture systems composed of unsaturated 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), saturated 1,2-dipalmitoyl-sn-glycero-3-phophocholine (DPPC), and Erg. Bilayer membrane fluidity and polarity were systematically analyzed using fluorescent probes. The presence of ≥30 mol % of Erg exhibited a significant ordering effect and stabilized membrane properties when temperatures increased, suggesting that Erg has a similar function to cholesterol (Chol) in comparable lipid systems that form a liquid-ordered phase. Erg was also observed to have a significant condensing effect at the monolayer level in saturated PC-enriched systems. The phase behavior of Erg in bilayer systems was compared with that of Chol, with the data suggesting that Erg behaves in a similar manner to Chol in membranes enriched with saturated lipids.