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Sample records for affecting membrane fluidity

  1. Even a Chronic Mild Hyperglycemia Affects Membrane Fluidity and Lipoperoxidation in Placental Mitochondria in Wistar Rats

    PubMed Central

    Figueroa-García, María del Consuelo; Espinosa-García, María Teresa; Martinez-Montes, Federico; Palomar-Morales, Martín; Mejía-Zepeda, Ricardo

    2015-01-01

    It is known the deleterious effects of diabetes on embryos, but the effects of diabetes on placenta and its mitochondria are still not well known. In this work we generated a mild hyperglycemia model in female wistar rats by intraperitoneal injection of streptozotocin in 48 hours-old rats. The sexual maturity onset of the female rats was delayed around 6–7 weeks and at 16 weeks-old they were mated, and sacrificed at day 19th of pregnancy. In placental total tissue and isolated mitochondria, the fatty acids composition was analyzed by gas chromatography, and lipoperoxidation was measured by thiobarbituric acid reactive substances. Membrane fluidity in mitochondria was measured with the excimer forming probe dipyrenylpropane and mitochondrial function was measured with a Clark-type electrode. The results show that even a chronic mild hyperglycemia increases lipoperoxidation and decreases mitochondrial function in placenta. Simultaneously, placental fatty acids metabolism in total tissue is modified but in a different way than in placental mitochondria. Whereas the chronic mild hyperglycemia induced a decrease in unsaturated to saturated fatty acids ratio (U/S) in placental total tissue, the ratio increased in placental mitochondria. The measurements of membrane fluidity showed that fluidity of placenta mitochondrial membranes increased with hyperglycemia, showing consistency with the fatty acids composition through the U/S index. The thermotropic characteristics of mitochondrial membranes were changed, showing lower transition temperature and activation energies. All of these data together demonstrate that even a chronic mild hyperglycemia during pregnancy of early reproductive Wistar rats, generates an increment of lipoperoxidation, an increase of placental mitochondrial membrane fluidity apparently derived from changes in fatty acids composition and consequently, mitochondrial malfunction. PMID:26630275

  2. Even a Chronic Mild Hyperglycemia Affects Membrane Fluidity and Lipoperoxidation in Placental Mitochondria in Wistar Rats.

    PubMed

    Figueroa-García, María del Consuelo; Espinosa-García, María Teresa; Martinez-Montes, Federico; Palomar-Morales, Martín; Mejía-Zepeda, Ricardo

    2015-01-01

    It is known the deleterious effects of diabetes on embryos, but the effects of diabetes on placenta and its mitochondria are still not well known. In this work we generated a mild hyperglycemia model in female wistar rats by intraperitoneal injection of streptozotocin in 48 hours-old rats. The sexual maturity onset of the female rats was delayed around 6-7 weeks and at 16 weeks-old they were mated, and sacrificed at day 19th of pregnancy. In placental total tissue and isolated mitochondria, the fatty acids composition was analyzed by gas chromatography, and lipoperoxidation was measured by thiobarbituric acid reactive substances. Membrane fluidity in mitochondria was measured with the excimer forming probe dipyrenylpropane and mitochondrial function was measured with a Clark-type electrode. The results show that even a chronic mild hyperglycemia increases lipoperoxidation and decreases mitochondrial function in placenta. Simultaneously, placental fatty acids metabolism in total tissue is modified but in a different way than in placental mitochondria. Whereas the chronic mild hyperglycemia induced a decrease in unsaturated to saturated fatty acids ratio (U/S) in placental total tissue, the ratio increased in placental mitochondria. The measurements of membrane fluidity showed that fluidity of placenta mitochondrial membranes increased with hyperglycemia, showing consistency with the fatty acids composition through the U/S index. The thermotropic characteristics of mitochondrial membranes were changed, showing lower transition temperature and activation energies. All of these data together demonstrate that even a chronic mild hyperglycemia during pregnancy of early reproductive Wistar rats, generates an increment of lipoperoxidation, an increase of placental mitochondrial membrane fluidity apparently derived from changes in fatty acids composition and consequently, mitochondrial malfunction.

  3. Membrane fluidity sensoring microbial fuel cell.

    PubMed

    Choi, Youngjin; Jung, Eunkyoung; Kim, Sunghyun; Jung, Seunho

    2003-04-01

    A study has been performed to examine the effect of temperature and ethanolic stresses on the coulombic efficiency of a microbial fuel cell. The conventional-type fuel cell containing Gram-negative bacteria, Proteus vulgaris, was investigated as a model system. From current output measurements, it was found that the coulombic yields were altered by environmental stresses such as temperature shock or ethanol treatment to the bacteria. While high-temperature or ethanolic shock led to a remarkable decrement in coulombic output, the low-temperature shock induced a slight increase in microbial fuel cell efficiency. These results indicate that the membrane fluidity is affected considerably by environmental stress, which in turn affects the electron transfer process through the bacterial cell membrane to and from the electrode. This interpretation was confirmed by the cyclic voltammetric study of a mediator on an electrode surface modified with the lipids extracted from the membrane of P. vulgaris under the given stress. Markedly different electrochemical behaviors were observed depending on the environmental stress. A reciprocal relationship between coulomb output and the ratio of saturation/unsaturation of fatty acids has been observed. This is the first report, to our knowledge, that the structural adaptation of membrane fatty acids in response to the environmental shock can regulate the coulombic efficiency of a microbial fuel cell.

  4. Effects of genistein and daidzein on erythrocyte membrane fluidity: an electron paramagnetic resonance study.

    PubMed

    Ajdzanović, Vladimir; Spasojević, Ivan; Filipović, Branko; Sosić-Jurjević, Branka; Sekulić, Milka; Milosević, Verica

    2010-04-01

    The maintenance of erythrocyte membrane fluidity at the physiological level is an important factor affecting the ability of erythrocytes to pass through blood vessels of small luminal diameter. Genistein and daidzein, which are used as alternative therapeutics in cardiovascular conditions, can be incorporated into the cell membrane and change its fluidity. The aim of this study was to examine the effects of genistein and daidzein on erythrocyte membrane fluidity at graded depths. We used electron paramagnetic resonance (EPR) spectroscopy and fatty acid spin probes (5-DS and 12-DS) where EPR spectra were dependent on fluidity. The results showed that genistein significantly (p < 0.05) decreased erythrocyte membrane fluidity near the hydrophilic surface, while daidzein significantly (p < 0.05) increased the same parameter in deeper regions of the membrane. These data suggest that the deep fluidizing effects of daidzein on erythrocyte membranes make it a better therapeutic choice than genistein in some cardiovascular conditions.

  5. Cyclosporin A reduces canalicular membrane fluidity and regulates transporter function in rats.

    PubMed Central

    Yasumiba, S; Tazuma, S; Ochi, H; Chayama, K; Kajiyama, G

    2001-01-01

    Changes of the biliary canalicular membrane lipid content can affect membrane fluidity and biliary lipid secretion in rats. The immunosuppressant cyclosporin A is known to cause intrahepatic cholestasis. This study investigated whether cyclosporin A influenced canalicular membrane fluidity by altering membrane phospholipids or transporter expression. In male Sprague-Dawley rats, a bile-duct cannula was inserted to collect bile, and sodium taurocholate was infused (100 nmol/min per 100 g) for 60 min. During steady-state taurocholate infusion, cyclosporin A (20 mg/kg) or vehicle was injected intravenously and then bile was collected for 80 min. After killing the rats, canalicular membrane vesicles were prepared. Expression of canalicular membrane transporters was assessed by Western blotting and canalicular membrane vesicle fluidity was estimated by fluorescence polarization. Cyclosporin A reduced biliary lipid secretion along with a disproportionate reduction of lipids relative to bile acids. Cyclosporin A significantly decreased canalicular membrane fluidity along with an increase of the cholesterol/phospholipid molar ratio. Only expression of the transporter P-glycoprotein was increased by cyclosporin A. Because canalicular membrane transporter expression was largely unchanged by cyclosporin A despite a marked decrease of biliary lipid secretion, transporter activity may partly depend upon canalicular membrane fluidity. PMID:11237863

  6. Fluidity of pea root plasma membranes under altered gravity

    NASA Astrophysics Data System (ADS)

    Klymchuk, D. O.; Baranenko, V. V.; Vorobyova, T. V.; Dubovoy, V. D.

    This investigation aims to determine whether clinorotation 2 rev min of pea Pisum sativum L seedlings induces the alterations in the physical-chemical properties of cellular membranes including the plasma membrane fluidity The last is an important regulator of functional activity of membrane enzymes The plasma membranes were isolated by aqueous two-phase partitioning from roots of 6-day old pea seedlings The membrane fluidity was examined by fluorescence spectroscopy using pyrene probe The plasma membrane vesicles with known protein concentration were added to the incubation buffer to a final concentration of 50 mu g of protein per ml A small amount by 1 mu l of pyrene solution in 2-propanol was added to the incubation mixture to a final probe concentration 5 mu M at constant mixing Fluorescence spectra were measured using a Perkin-Elmer LS-50 spectrofluorometer Perkin-Elmer England Pyrene was excited at 337 nm and fluorescence intensity of monomers I M and excimers I E were measured at 393 and 470 nm respectively The I E I M ratios were 0 081 pm 0 003 and 0 072 pm 0 004 in preparations obtained from clinorotated and the control seedlings respectively This fact indicates that rotation on the clinostat increases the membrane fluidity Compared with controls clinorotated seedlings have also showed a reduced growth and a higher level of total unsaturated fatty acids determined by gas chromatography The factors that influence on the fluidity of membrane lipids in bilayer appear to be the

  7. Elucidating how bamboo salt interacts with supported lipid membranes: influence of alkalinity on membrane fluidity.

    PubMed

    Jeong, Jong Hee; Choi, Jae-Hyeok; Kim, Min Chul; Park, Jae Hyeon; Herrin, Jason Scott; Kim, Seung Hyun; Lee, Haiwon; Cho, Nam-Joon

    2015-07-01

    Bamboo salt is a traditional medicine produced from sea salt. It is widely used in Oriental medicine and is an alkalizing agent with reported antiinflammatory, antimicrobial and chemotherapeutic properties. Notwithstanding, linking specific molecular mechanisms with these properties has been challenging to establish in biological systems. In part, this issue may be related to bamboo salt eliciting nonspecific effects on components found within these systems. Herein, we investigated the effects of bamboo salt solution on supported lipid bilayers as a model system to characterize the interaction between lipid membranes and bamboo salt. The atomic composition of unprocessed and processed bamboo salts was first analyzed by mass spectrometry, and we identified several elements that have not been previously reported in other bamboo salt preparations. The alkalinity of hydrated samples was also measured and determined to be between pH 10 and 11 for bamboo salts. The effect of processed bamboo salt solutions on the fluidic properties of a supported lipid bilayer on glass was next investigated by fluorescence recovery after photobleaching (FRAP) analysis. It was demonstrated that, with increasing ionic strength of the bamboo salt solution, the fluidity of a lipid bilayer increased. On the contrary, increasing the ionic strength of near-neutral buffer solutions with sodium chloride salt diminished fluidity. To reconcile these two observations, we identified that solution alkalinity is critical for the effects of bamboo salt on membrane fluidity, as confirmed using three additional commercial bamboo salt preparations. Extended-DLVO model calculations support that the effects of bamboo salt on lipid membranes are due to the alkalinity imparting a stronger hydration force. Collectively, the results of this work demonstrate that processing of bamboo salt strongly affects its atomic composition and that the alkalinity of bamboo salt solutions contributes to its effect on membrane

  8. Fullerene inhibits benzo(a)pyrene Efflux from Cyprinus carpio hepatocytes by affecting cell membrane fluidity and P-glycoprotein expression.

    PubMed

    Chen, Qiqing; Hu, Xialin; Wang, Rui; Yuan, Jin; Yin, Daqiang

    2016-05-01

    P-Glycoprotein (P-gp) can protect cells by pumping out toxic compounds, and has been found widely expressed in fish tissues. Here, we illustrate the P-gp efflux ability for benzo(a)pyrene (BaP) in the hepatocytes of common carp (Cyprinus carpio) after exposing to fullerene aqueous suspension (nC60). The results revealed that nC60 increased the membrane fluidity by decreasing the ratio of saturated to unsaturated fatty acids, and increased the cholesterol contents. These findings, combined with 10-38% and 70-75% down-regulation of P-gp mRNA and protein respectively, suggested that nC60 caused inhibition on P-gp efflux transport system. Therefore, we further investigated the cellular efflux ability for BaP. Results showed unequivocally that nC60 is a potent P-gp inhibitor. The retaining BaP amounts after efflux were elevated by 1.7-2.8 fold during the 10 day exposure. Meanwhile, 5mg/L humic acid (one of the important fractions of natural organic matter, which is ubiquitous in aquatic environment) alleviated the nC60 damage to hepatocytes in terms of oxidative damage, cholesterol increment, and P-gp content reduction; and finally attenuated the suppressed P-gp efflux ability. Collectively, this study provides the first evidence of nC60 toxicity to P-gp functionality in fish and illustrates the possible mechanism of the suppressed P-gp efflux ability for BaP.

  9. Effect of changes in the composition of cellular fatty acids on membrane fluidity of Rhodobacter sphaeroides.

    PubMed

    Kim, Eui-Jin; Lee, Jeong K

    2015-02-01

    The cellular fatty acid composition is important for metabolic plasticity in Rhodobacter sphaeroides. We explored the effects of changing the cellular ratio of unsaturated fatty acids (UFAs) to saturated fatty acids (SFAs) in R. sphaeroides by overexpressing several key fatty acid biosynthetic enzymes through the use of expression plasmid pRK415. Bacteria containing the plasmid pRKfabI1 with the fabI1 gene that encodes enoyl-acyl carrier protein (ACP) reductase showed a reduction in the cellular UFA to SFA ratio from 4 (80% UFA) to 2 (65% UFA) and had decreased membrane fluidity and reduced cell growth. Additionally, the ratio of UFA to SFA of the chromatophore vesicles from pRKfabI1 -containing cells was similarly lowered, and the cell had decreased levels of light-harvesting complexes, but no change in intracytoplasmic membrane (ICM) content or photosynthetic (PS) gene expression. Both inhibition of enoyl- ACP reductase with diazaborine and addition of exogenous UFA restored membrane fluidity, cell growth, and the UFA to SFA ratio to wild-type levels in this strain. R. sphaeroides containing the pRKfabB plasmid with the fabB gene that encodes the enzyme β-ketoacyl-ACP synthase I exhibited an increased UFA to SFA ratio from 4 (80% UFA) to 9 (90% UFA), but showed no change in membrane fluidity or growth rate relative to control cells. Thus, membrane fluidity in R. sphaeroides remains fairly unchanged when membrane UFA levels are between 80% and 90%, whereas membrane fluidity, cell growth, and cellular composition are affected when UFA levels are below 80%.

  10. Measurement of Cell Membrane Fluidity by Laurdan GP: Fluorescence Spectroscopy and Microscopy.

    PubMed

    Scheinpflug, Kathi; Krylova, Oxana; Strahl, Henrik

    2017-01-01

    Membrane fluidity is a critical parameter of cellular membranes which cells continuously strive to maintain within a viable range. An interference with the correct membrane fluidity state can strongly inhibit cell function. Triggered changes in membrane fluidity have been postulated to contribute to the mechanism of action of membrane targeting antimicrobials, but the corresponding analyses have been hampered by the absence of readily available analytical tools. Here, we provide detailed protocols that allow straightforward measurement of antibiotic compound-triggered changes in membrane fluidity both in vivo and in vitro.

  11. Local anesthetics structure-dependently interact with anionic phospholipid membranes to modify the fluidity.

    PubMed

    Tsuchiya, Hironori; Ueno, Takahiro; Mizogami, Maki; Takakura, Ko

    2010-01-05

    While bupivacaine is more cardiotoxic than other local anesthetics, the mechanistic background for different toxic effects remains unclear. Several cardiotoxic compounds act on lipid bilayers to change the physicochemical properties of membranes. We comparatively studied the interaction of local anesthetics with lipid membranous systems which might be related to their structure-selective cardiotoxicity. Amide local anesthetics (10-300 microM) were reacted with unilamellar vesicles which were prepared with different phospholipids and cholesterol of varying lipid compositions. They were compared on the potencies to modify membrane fluidity by measuring fluorescence polarization. Local anesthetics interacted with liposomal membranes to increase the fluidity. Increasing anionic phospholipids in membranes enhanced the membrane-fluidizing effects of local anesthetics with the potency being cardiolipin>phosphatidic acid>phosphatidylglycerol>phosphatidylserine. Cardiolipin was most effective on bupivacaine, followed by ropivacaine. Local anesthetics interacted differently with biomimetic membranes consisting of 10mol% cardiolipin, 50mol% other phospholipids and 40mol% cholesterol with the potency being bupivacaine>ropivacaine>lidocaine>prilocaine, which agreed with the rank order of cardiotoxicity. Bupivacaine significantly fluidized 2.5-12.5mol% cardiolipin-containing membranes at cardiotoxicologically relevant concentrations. Bupivacaine is considered to affect lipid bilayers by interacting electrostatically with negatively charged cardiolipin head groups and hydrophobically with phospholipid acyl chains. The structure-dependent interaction with lipid membranes containing cardiolipin, which is preferentially localized in cardiomyocyte mitochondrial membranes, may be a mechanistic clue to explain the structure-selective cardiotoxicity of local anesthetics.

  12. Influence of zinc deficiency on cell-membrane fluidity in Jurkat, 3T3 and IMR-32 cells.

    PubMed Central

    Verstraeten, Sandra V; Zago, M Paola; MacKenzie, Gerardo G; Keen, Carl L; Oteiza, Patricia I

    2004-01-01

    We investigated whether zinc deficiency can affect plasma membrane rheology. Three cell lines, human leukaemia T-cells (Jurkat), rat fibroblasts (3T3) and human neuroblastoma cells (IMR-32), were cultured for 48 h in control medium, in zinc-deficient medium (1.5 microM zinc; 1.5 Zn), or in the zinc-deficient medium supplemented with 15 microM zinc (15 Zn). The number of viable cells was lower in the 1.5 Zn group than in the control and 15 Zn groups. The frequency of apoptosis was higher in the 1.5 Zn group than in the control and 15 Zn groups. Membrane fluidity was evaluated using the 6-(9-anthroyloxy)stearic acid and 16-(9-anthroyloxy)palmitic acid probes. Membrane fluidity was higher in 1.5 Zn cells than in the control cells; no differences were observed between control cells and 15 Zn cells. The effect of zinc deficiency on membrane fluidity at the water/lipid interface was associated with a higher phosphatidylserine externalization. The higher membrane fluidity in the hydrophobic region of the bilayer was correlated with a lower content of arachidonic acid. We suggest that the increased fluidity of the membrane secondary to zinc deficiency is in part due to a decrease in arachidonic acid content and the apoptosis-related changes in phosphatidylserine distribution. PMID:14629198

  13. Selective accumulation and growth inhibition of hybrid liposomes to human hepatocellular carcinoma cells in relation to fluidity of plasma membranes.

    PubMed

    Komizu, Yuji; Ueoka, Hidetsugu; Ueoka, Ryuichi

    2012-02-03

    Hybrid liposomes (HLs), composed of l-α-dimyristoylphosphatidylcholine (DMPC) and polyoxyethylene(23) dodecyl ether, have selectively inhibited the growth of human hepatocellular carcinoma (HCC) cells without affecting normal hepatocytes to trigger apoptosis via caspase-3 activation. Furthermore, HLs distinguished between the HCC and normal cells which had higher and lower membrane fluidities respectively, then fused and accumulated preferentially into the membranes of HCC cells. It is noteworthy that the anti-cancer activity of HLs correlated well with the fluidity of cell membranes for HCC and other cancer cells. These results suggest that HLs could target cancer cell-membranes in relation to their lipid fluidity that provide the possibility of novel nanotherapy for intractable cancer.

  14. Assessment of Membrane Fluidity Fluctuations during Cellular Development Reveals Time and Cell Type Specificity.

    PubMed

    Noutsi, Pakiza; Gratton, Enrico; Chaieb, Sahraoui

    2016-01-01

    Cell membrane is made up of a complex structure of lipids and proteins that diffuse laterally giving rise to what we call membrane fluidity. During cellular development, such as differentiation cell membranes undergo dramatic fluidity changes induced by proteins such as ARC and Cofilin among others. In this study we used the generalized polarization (GP) property of fluorescent probe Laurdan using two-photon microscopy to determine membrane fluidity as a function of time and for various cell lines. A low GP value corresponds to a higher fluidity and a higher GP value is associated with a more rigid membrane. Four different cell lines were monitored such as hN2, NIH3T3, HEK293 and L6 cells. Membrane fluidity was measured at 12h, 72h and 92 h. Our results show significant changes in membrane fluidity among all cell types at different time points. GP values tend to increase significantly within 92 h in hN2 cells and 72 h in NIH3T3 cells and only at 92 h in HEK293 cells. L6 showed a marked decrease in membrane fluidity at 72 h and starts to increase at 92 h. As expected, NIH3T3 cells have more rigid membrane at earlier time points. On the other hand, neurons tend to have the highest membrane fluidity at early time points emphasizing its correlation with plasticity and the need for this malleability during differentiation. This study sheds light on the involvement of membrane fluidity during neuronal differentiation and development of other cell lines.

  15. Assessment of Membrane Fluidity Fluctuations during Cellular Development Reveals Time and Cell Type Specificity

    PubMed Central

    Noutsi, Pakiza; Gratton, Enrico; Chaieb, Sahraoui

    2016-01-01

    Cell membrane is made up of a complex structure of lipids and proteins that diffuse laterally giving rise to what we call membrane fluidity. During cellular development, such as differentiation cell membranes undergo dramatic fluidity changes induced by proteins such as ARC and Cofilin among others. In this study we used the generalized polarization (GP) property of fluorescent probe Laurdan using two-photon microscopy to determine membrane fluidity as a function of time and for various cell lines. A low GP value corresponds to a higher fluidity and a higher GP value is associated with a more rigid membrane. Four different cell lines were monitored such as hN2, NIH3T3, HEK293 and L6 cells. Membrane fluidity was measured at 12h, 72h and 92 h. Our results show significant changes in membrane fluidity among all cell types at different time points. GP values tend to increase significantly within 92 h in hN2 cells and 72 h in NIH3T3 cells and only at 92 h in HEK293 cells. L6 showed a marked decrease in membrane fluidity at 72 h and starts to increase at 92 h. As expected, NIH3T3 cells have more rigid membrane at earlier time points. On the other hand, neurons tend to have the highest membrane fluidity at early time points emphasizing its correlation with plasticity and the need for this malleability during differentiation. This study sheds light on the involvement of membrane fluidity during neuronal differentiation and development of other cell lines. PMID:27362860

  16. Eicosapentaenoic acid reduces membrane fluidity, inhibits cholesterol domain formation, and normalizes bilayer width in atherosclerotic-like model membranes.

    PubMed

    Mason, R Preston; Jacob, Robert F; Shrivastava, Sandeep; Sherratt, Samuel C R; Chattopadhyay, Amitabha

    2016-12-01

    Cholesterol crystalline domains characterize atherosclerotic membranes, altering vascular signaling and function. Omega-3 fatty acids reduce membrane lipid peroxidation and subsequent cholesterol domain formation. We evaluated non-peroxidation-mediated effects of eicosapentaenoic acid (EPA), other TG-lowering agents, docosahexaenoic acid (DHA), and other long-chain fatty acids on membrane fluidity, bilayer width, and cholesterol domain formation in model membranes. In membranes prepared at 1.5:1 cholesterol-to-phospholipid (C/P) mole ratio (creating pre-existing domains), EPA, glycyrrhizin, arachidonic acid, and alpha linolenic acid promoted the greatest reductions in cholesterol domains (by 65.5%, 54.9%, 46.8%, and 45.2%, respectively) compared to controls; other treatments had modest effects. EPA effects on cholesterol domain formation were dose-dependent. In membranes with 1:1 C/P (predisposing domain formation), DHA, but not EPA, dose-dependently increased membrane fluidity. DHA also induced cholesterol domain formation without affecting temperature-induced changes in-bilayer unit cell periodicity relative to controls (d-space; 57Å-55Å over 15-30°C). Together, these data suggest simultaneous formation of distinct cholesterol-rich ordered domains and cholesterol-poor disordered domains in the presence of DHA. By contrast, EPA had no effect on cholesterol domain formation and produced larger d-space values relative to controls (60Å-57Å; p<0.05) over the same temperature range, suggesting a more uniform maintenance of lipid dynamics despite the presence of cholesterol. These data indicate that EPA and DHA had different effects on membrane bilayer width, membrane fluidity, and cholesterol crystalline domain formation; suggesting omega-3 fatty acids with differing chain length or unsaturation may differentially influence membrane lipid dynamics and structural organization as a result of distinct phospholipid/sterol interactions.

  17. Photopolymerization of Dienoyl Lipids Creates Planar Supported Poly(lipid) Membranes with Retained Fluidity.

    PubMed

    Orosz, Kristina S; Jones, Ian W; Keogh, John P; Smith, Christopher M; Griffin, Kaitlyn R; Xu, Juhua; Comi, Troy J; Hall, H K; Saavedra, S Scott

    2016-02-16

    Polymerization of substrate-supported bilayers composed of dienoylphosphatidylcholine (PC) lipids is known to greatly enhance their chemical and mechanical stability; however, the effects of polymerization on membrane fluidity have not been investigated. Here planar supported lipid bilayers (PSLBs) composed of dienoyl PCs on glass substrates were examined to assess the degree to which UV-initiated polymerization affects lateral lipid mobility. Fluorescence recovery after photobleaching (FRAP) was used to measure the diffusion coefficients (D) and mobile fractions of rhodamine-DOPE in unpolymerized and polymerized PSLBs composed of bis-sorbyl phosphatidylcholine (bis-SorbPC), mono-sorbyl-phosphatidylcholine (mono-SorbPC), bis-dienoyl-phosphatidylcholine (bis-DenPC), and mono-dienoyl phosphatidylcholine (mono-DenPC). Polymerization was performed in both the Lα and Lβ phase for each lipid. In all cases, polymerization reduced membrane fluidity; however, measurable lateral diffusion was retained which is attributed to a low degree of polymerization. The D values for sorbyl lipids were less than those of the denoyl lipids; this may be a consequence of the distal location of polymerizable group in the sorbyl lipids which may facilitate interleaflet bonding. The D values measured after polymerization were 0.1-0.8 of those measured before polymerization, a range that corresponds to fluidity intermediate between that of a Lα phase and a Lβ phase. This D range is comparable to ratios of D values reported for liquid-disordered (Ld) and liquid-ordered (Lo) lipid phases and indicates that the effect of UV polymerization on lateral diffusion in a dienoyl PSLB is similar to the transition from a Ld phase to a Lo phase. The partial retention of fluidity in UV-polymerized PSLBs, their enhanced stability, and the activity of incorporated transmembrane proteins and peptides is discussed.

  18. Photopolymerization of dienoyl lipids creates planar supported poly(lipid) membranes with retained fluidity

    PubMed Central

    Orosz, Kristina S.; Jones, Ian W.; Keogh, John P.; Smith, Christopher M.; Griffin, Kaitlyn R.; Xu, Juhua; Comi, Troy J.; Hall, H. K.

    2016-01-01

    Polymerization of substrate-supported bilayers composed of dienoyl phosphatidylcholine (PC) lipids is known to greatly enhance their chemical and mechanical stability, however the effects of polymerization on membrane fluidity have not been investigated. Here planar supported lipid bilayers (PSLBs) composed of dienoyl PCs on glass substrates were examined to assess the degree to which UV-initiated polymerization affects lateral lipid mobility. Fluorescence recovery after photobleaching (FRAP) was used to measure the diffusion coefficients (D) and mobile fractions of rhodamine-DOPE in unpolymerized and polymerized PSLBs composed of bis-sorbyl phosphatidylcholine (bis-SorbPC), mono-sorbyl phosphatidylcholine (mono-SorbPC), bis-dienoyl phosphatidylcholine (bis-DenPC) and mono-dienoyl phosphatidylcholine (mono-DenPC). Polymerization was performed in both the Lα and Lβ phase for each lipid. In all cases, polymerization reduced membrane fluidity, however measurable lateral diffusion was retained which is attributed to a low degree of polymerization. The D values for sorbyl lipids were less than those of the denoyl lipids; this may be a consequence of the distal location of polymerizable group in the sorbyl lipids which may facilitate inter-leaflet bonding. The D values measured after polymerization were 0.1 to 0.8 of those measured before polymerization, a range that corresponds to fluidity intermediate between that of a Lα phase and a Lβ phase. This D range is comparable to ratios of D values reported for liquid-disordered (Ld) and liquid-ordered (Lo) lipid phases, and indicates that the effect of UV polymerization on lateral diffusion in a dienoyl PSLB is similar to the transition from a Ld phase to a Lo phase. The partial retention of fluidity in UV polymerized PSLBs, their enhanced stability, and the activity of incorporated transmembrane proteins and peptides is discussed. PMID:26794208

  19. Influence of nanoparticle-membrane electrostatic interactions on membrane fluidity and bending elasticity.

    PubMed

    Santhosh, Poornima Budime; Velikonja, Aljaž; Perutkova, Šarka; Gongadze, Ekaterina; Kulkarni, Mukta; Genova, Julia; Eleršič, Kristina; Iglič, Aleš; Kralj-Iglič, Veronika; Ulrih, Nataša Poklar

    2014-02-01

    The aim of this work is to investigate the effect of electrostatic interactions between the nanoparticles and the membrane lipids on altering the physical properties of the liposomal membrane such as fluidity and bending elasticity. For this purpose, we have used nanoparticles and lipids with different surface charges. Positively charged iron oxide (γ-Fe2O3) nanoparticles, neutral and negatively charged cobalt ferrite (CoFe2O4) nanoparticles were encapsulated in neutral lipid 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine and negatively charged 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-L-serine lipid mixture. Membrane fluidity was assessed through the anisotropy measurements using the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene. Though the interaction of both the types of nanoparticles reduced the membrane fluidity, the results were more pronounced in the negatively charged liposomes encapsulated with positively charged iron oxide nanoparticles due to strong electrostatic attractions. X-ray photoelectron spectroscopy results also confirmed the presence of significant quantity of positively charged iron oxide nanoparticles in negatively charged liposomes. Through thermally induced shape fluctuation measurements of the giant liposomes, a considerable reduction in the bending elasticity modulus was observed for cobalt ferrite nanoparticles. The experimental results were supported by the simulation studies using modified Langevin-Poisson-Boltzmann model.

  20. Capacitation-associated changes in membrane fluidity in asthenozoospermic human spermatozoa.

    PubMed

    Buffone, Mariano G; Doncel, Gustavo F; Calamera, Juan C; Verstraeten, Sandra V

    2009-08-01

    The fertilizing potential of human spermatozoa relies on their ability to capacitate as they travel through the female reproductive tract. During this process, cholesterol is released from the plasma membrane, altering its architecture and dynamics. Using ISolate gradients, we obtained high (L90)- and low (L45)-quality spermatozoa from asthenozoospermic human semen samples. We tested the hypothesis that the lower fertilizing ability of asthenozoospermic L90 cells could be related to a lower ability to increase their membrane fluidity during capacitation. We assessed two sets of fluorescent probes: (i) DPH, TMA-DPH and PA-DPH which senses the hydrophobic core, cytosolic and exofacial leaflets of the bilayer, respectively and (ii) Laurdan, sensitive to the amount of water molecules intercalated between lipid moieties of the membrane (membrane hydration). Before capacitation, membrane fluidity of asthenozoospermic sperm populations was similar to the corresponding fractions of normozoospermic cells when evaluated with DPH, TMA-DPH or PA-DPH. Asthenozoospermic whole samples displayed lower plasma membrane hydration than normozoospermic cells as evidenced with Laurdan. After capacitation, asthenozoospermic L45 and L90 cells failed to increase their membrane fluidity in opposition to normozoospermic cells. Interestingly, membrane hydration significantly correlated with the main sperm motion parameters analysed, being a low membrane hydration associated with poor sperm movement. These results show that low-motility spermatozoa are unable to respond to capacitation with the necessary changes in membrane fluidity. This defect in sperm plasma membrane rheology may be responsible for their poor functional quality and low fertilizing ability.

  1. Membrane cholesterol modulates the fluid shear stress response of polymorphonuclear leukocytes via its effects on membrane fluidity

    PubMed Central

    Zhang, Xiaoyan; Hurng, Jonathan; Rateri, Debra L.; Daugherty, Alan; Schmid-Schönbein, Geert W.

    2011-01-01

    Continuous exposure of polymorphonuclear leukocytes (PMNLs) to circulatory hemodynamics points to fluid flow as a biophysical regulator of their activity. Specifically, fluid flow-derived shear stresses deactivate leukocytes via actions on the conformational activities of proteins on the cell surface. Because membrane properties affect activities of membrane-bound proteins, we hypothesized that changes in the physical properties of cell membranes influence PMNL sensitivity to fluid shear stress. For this purpose, we modified PMNL membranes and showed that the cellular mechanosensitivity to shear was impaired whether we increased, reduced, or disrupted the organization of cholesterol within the lipid bilayer. Notably, PMNLs with enriched membrane cholesterol exhibited attenuated pseudopod retraction responses to shear that were recovered by select concentrations of benzyl alcohol (a membrane fluidizer). In fact, PMNL responses to shear positively correlated (R2 = 0.96; P < 0.0001) with cholesterol-related membrane fluidity. Moreover, in low-density lipoprotein receptor-deficient (LDLr−/−) mice fed a high-fat diet (a hypercholesterolemia model), PMNL shear-responses correlated (R2 = 0.5; P < 0.01) with blood concentrations of unesterified (i.e., free) cholesterol. In this regard, the shear-responses of PMNLs gradually diminished and eventually reversed as free cholesterol levels in blood increased during 8 wk of the high-fat diet. Collectively, our results provided evidence that cholesterol is an important component of the PMNL mechanotransducing capacity and elevated membrane cholesterol impairs PMNL shear-responses at least partially through its impact on membrane fluidity. This cholesterol-linked perturbation may contribute to dysregulated PMNL activity (e.g., chronic inflammation) related to hypercholesterolemia and causal for cardiovascular pathologies (e.g., atherosclerosis). PMID:21525434

  2. Analysis of the membrane fluidity of erythrocyte ghosts in diabetic, spontaneously hypertensive rats.

    PubMed

    Pérez-Hernández, Ismael H; Avendaño-Flores, Yesica S; Mejía-Zepeda, Ricardo

    2010-12-01

    Diabetes and hypertension are closely related diseases associated with changes in membrane fluidity. Here, we measured the membrane fluidity of erythrocyte ghosts from spontaneously hypertensive rats (SHR), with or without streptozotocin (STZ)-induced diabetes, at the ages of 1, 3 and 6 months, by introducing the use of the intramolecular excimer forming dipyrenylpropane (DPyP) in this model. Type 2 diabetes mellitus (T2DM) was induced in 48-h-old, newborn male SHR by intraperitoneal injection of STZ. We found lower excimer to monomer (I (e)/I (m)) DPyP ratios in diabetic SHR than in control SHR at 3 and 6 months old, indicating a decrease in membrane fluidity. Simultaneously, the composition of fatty acids was determined and it was found that the unsaturated to saturated fatty acids ratio (U/S) was compatible with changes in membrane fluidity. These results suggest that the change in fatty acid composition of erythrocyte ghosts contributes significantly to the decreased membrane fluidity detected with DPyP in diabetic SHR.

  3. Biochemical characterization and membrane fluidity of membranous vesicles isolated from boar seminal plasma.

    PubMed

    Piehl, Lidia L; Cisale, Humberto; Torres, Natalia; Capani, Francisco; Sterin-Speziale, Norma; Hager, Alfredo

    2006-05-01

    Mammalian seminal plasma contains membranous vesicles (MV), which differ in composition and origin. Among these particles, human prostasomes and equine prostasome-like MV have been the most studied. The aim of the present work is to characterize the biochemical composition and membrane fluidity of MV isolated from boar seminal plasma. The MV from boar seminal plasma were isolated by ultracentrifugation and further purification by gel filtration on Sephadex G-200. The MV were examined by electron microscopy (EM), amount of cholesterol, total phospholipid, protein content, and phospholipid composition were analyzed. Membrane fluidity of MV and spermatozoa were estimated from the electron spin resonance (ESR) spectra of the 5-doxilstearic acid incorporated into the vesicle membranes by the order parameter (S). The S parameter gives a measure of degree of structural order in the membrane and is defined as the ratio of the spectral anisotropy in the membranes to the maximum anisotropy obtained in a rigidly oriented system. The S parameter takes into consideration that S = 1 for a rapid spin-label motion of about only one axis and S = 0 for a rapid isotropic motion. Intermediate S values between S = 0 and S = 1 represents the consequence of decreased membrane fluidity. The EM revealed the presence of bilaminar and multilaminar electron-dense vesicles. Cholesterol to phospholipid molar ratio from the isolated MV was 1.8. Phospholipid composition showed a predominance of sphingomyelin. The S parameter for porcine MV and for boar spermatozoa was 0.73 +/- 0.02 and 0.644 +/- 0.008, respectively, with the S for MV being greater (p < 0.001) than the S for spermatozoa. The high order for S found for boar MV was in agreement with the greater cholesterol/phospholipids ratio and the lesser ratio for phosphatidylcholine/sphingomyelin. Results obtained in the present work indicate that MV isolated from boar semen share many biochemical and morphological characteristics with equine

  4. Orientation of paramecium swimming in a static magnetic field: Dependence on membrane lipid fluidity.

    PubMed

    Nakaoka, Yasuo; Itoh, Junya; Shimizu, Kikuo

    2011-01-01

    We studied the swimming orientation of the ciliated protozoan Paramecium aurelia in a static magnetic field (0.78 T). P. aurelia is a complex of species termed syngens, whose cell morphology appears similar on microscopic examination. In the magnetic field, the cells of some syngens gradually changed their swimming orientation so that they were swimming perpendicular or parallel to the magnetic field, although such sensitivity to magnetic fields differs between syngens. When the temperature of the cell suspension was raised, the magnetic sensitivity of the cells was decreased. On the other hand, when the cells were cultured beforehand at a high temperature, their magnetic sensitivity was increased. These results raise the possibility that membrane lipid fluidity, which is inversely proportional to the membrane lipid order, contributes to the magnetic orientation of syngens. In this study, measurements of membrane lipid fluidity obtained using fluorescence image analysis with the lipophilic dye, laurdan (6-lauroyl-2-dimethylaminonaphtalene), showed that the degree of membrane lipid fluidity was correlated with the differences in magnetic orientation between syngens. That is, the syngens with decreased membrane fluidity showed an increased degree of magnetic orientation. Therefore, the membrane lipid order is a key factor in the magnetic orientation of Paramecium swimming.

  5. Effect of oxidative stress on plasma membrane fluidity of THP-1 induced macrophages.

    PubMed

    de la Haba, Carlos; Palacio, José R; Martínez, Paz; Morros, Antoni

    2013-02-01

    Plasma membrane is one of the preferential targets of reactive oxygen species which cause lipid peroxidation. This process modifies membrane properties such as membrane fluidity, a very important physical feature known to modulate membrane protein localization and function. The aim of this study is to evaluate the effect of oxidative stress on plasma membrane fluidity regionalization of single living THP-1 macrophages. These cells were oxidized with H(2)O(2) at different concentrations, and plasma membrane fluidity was analyzed by two-photon microscopy in combination with the environment-sensitive probe Laurdan. Results show a significant H(2)O(2) concentration dependent increase in the frequency of rigid lipid regions, mainly attributable to lipid rafts, at the expense of the intermediate fluidity regions. A novel statistical analysis evaluated changes in size and number of lipid raft domains under oxidative stress conditions, as lipid rafts are platforms aiding cell signaling and are thought to have relevant roles in macrophage functions. It is shown that H(2)O(2) causes an increase in the number, but not the size, of raft domains. As macrophages are highly resistant to H(2)O(2), these new raft domains might be involved in cell survival pathways.

  6. Erythrocyte membrane fluidity and indices of plasmatic oxidative damage after acute physical exercise in humans.

    PubMed

    Berzosa, C; Gómez-Trullén, E M; Piedrafita, E; Cebrián, I; Martínez-Ballarín, E; Miana-Mena, F J; Fuentes-Broto, L; García, J J

    2011-06-01

    Optimal levels of membrane fluidity are essential for numerous cell functions including cell growth, solute transport and signal transduction. Since exercise enhances free radical production, our aim was to evaluate in healthy male subjects the effects of an acute bout of maximal and submaximal exercise on the erythrocyte membrane fluidity and its possible relation to the oxidative damage overproduction due to exercise. Subjects (n = 34) performed three cycloergometric tests: a continuous progressive exercise, a strenuous exercise until exhaustion and an acute bout of exercise at an intensity corresponding to 70% of maximal work capacity for 30 min. Venous blood samples were collected before and immediately after these exercises. Erythrocyte membrane fluidity was assessed by fluorescence spectroscopy. Plasma malondialdehyde (MDA) and 4-hydroxyalkenals (4-HDA) concentrations and carbonyl content of plasmatic proteins were used as an index of lipid and protein oxidation, respectively. Exercise produced a dramatic drop in the erythrocyte membrane fluidity as compared to resting time, but this was not accompanied by significant changes in the plasmatic MDA and 4-HDA concentrations. The highest erythrocyte membrane rigidity was detected immediately after strenuous exercise until exhaustion was performed. Protein carbonyl levels were higher after exhaustive exercises than at rest. Continuous progressive and strenuous exercises until exhaustion, but not submaximal workload, resulted in a significant enhanced accumulation of carbonylated proteins in the plasma. These findings are consistent with the idea that exercise exaggerates oxidative damage, which may contribute, at least partially, to explain the rigidity in the membrane of the erythrocytes due to acute exercise.

  7. LPS-Induced Macrophage Activation and Plasma Membrane Fluidity Changes are Inhibited Under Oxidative Stress.

    PubMed

    de la Haba, Carlos; Morros, Antoni; Martínez, Paz; Palacio, José R

    2016-12-01

    Macrophage activation is essential for a correct and efficient response of innate immunity. During oxidative stress membrane receptors and/or membrane lipid dynamics can be altered, leading to dysfunctional cell responses. Our aim is to analyze membrane fluidity modifications and cell function under oxidative stress in LPS-activated macrophages. Membrane fluidity of individual living THP-1 macrophages was evaluated by the technique two-photon microscopy. LPS-activated macrophage function was determined by TNFα secretion. It was shown that LPS activation causes fluidification of macrophage plasma membrane and production of TNFα. However, oxidative stress induces rigidification of macrophage plasma membrane and inhibition of cell activation, which is evidenced by a decrease of TNFα secretion. Thus, under oxidative conditions macrophage proinflammatory response might develop in an inefficient manner.

  8. Hydrostatic pressure decreases membrane fluidity and lipid desaturase expression in chondrocyte progenitor cells.

    PubMed

    Montagne, Kevin; Uchiyama, Hiroki; Furukawa, Katsuko S; Ushida, Takashi

    2014-01-22

    Membrane biomechanical properties are critical in modulating nutrient and metabolite exchange as well as signal transduction. Biological membranes are predominantly composed of lipids, cholesterol and proteins, and their fluidity is tightly regulated by cholesterol and lipid desaturases. To determine whether such membrane fluidity regulation occurred in mammalian cells under pressure, we investigated the effects of pressure on membrane lipid order of mouse chondrogenic ATDC5 cells and desaturase gene expression. Hydrostatic pressure linearly increased membrane lipid packing and simultaneously repressed lipid desaturase gene expression. We also showed that cholesterol mimicked and cholesterol depletion reversed those effects, suggesting that desaturase gene expression was controlled by the membrane physical state itself. This study demonstrates a new effect of hydrostatic pressure on mammalian cells and may help to identify the molecular mechanisms involved in hydrostatic pressure sensing in chondrocytes.

  9. Effect of superparamagnetic iron oxide nanoparticles on fluidity and phase transition of phosphatidylcholine liposomal membranes

    PubMed Central

    Santhosh, Poornima Budime; Drašler, Barbara; Drobne, Damjana; Kreft, Mateja Erdani; Kralj, Slavko; Makovec, Darko; Ulrih, Nataša Poklar

    2015-01-01

    Superparamagnetic iron oxide nanoparticles (SPIONs) with multifunctional properties have shown great promise in theranostics. The aim of our work was to compare the effects of SPIONs on the fluidity and phase transition of the liposomal membranes prepared with zwitterionic phosphatidylcholine lipids. In order to study if the surface modification of SPIONs has any influence on these membrane properties, we have used four types of differently functionalized SPIONs, such as: plain SPIONs (primary size was shown to bê11 nm), silica-coated SPIONs, SPIONs coated with silica and functionalized with positively charged amino groups or negatively charged carboxyl groups (the primary size of all the surface-modified SPIONs was ~20 nm). Small unilamellar vesicles prepared with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine lipids and multilamellar vesicles prepared with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine lipids were encapsulated or incubated with the plain and surface-modified SPIONs to determine the fluidity and phase transition temperature of the bilayer lipids, respectively. Fluorescent anisotropy and differential scanning calorimetric measurements of the liposomes that were either encapsulated or incubated with the suspension of SPIONs did not show a significant difference in the lipid ordering and fluidity; though the encapsulated SPIONs showed a slightly increased effect on the fluidity of the model membranes in comparison with the incubated SPIONs. This indicates the low potential of the SPIONs to interact with the nontargeted cell membranes, which is a desirable factor for in vivo applications. PMID:26491286

  10. Effect of superparamagnetic iron oxide nanoparticles on fluidity and phase transition of phosphatidylcholine liposomal membranes.

    PubMed

    Santhosh, Poornima Budime; Drašler, Barbara; Drobne, Damjana; Kreft, Mateja Erdani; Kralj, Slavko; Makovec, Darko; Ulrih, Nataša Poklar

    2015-01-01

    Superparamagnetic iron oxide nanoparticles (SPIONs) with multifunctional properties have shown great promise in theranostics. The aim of our work was to compare the effects of SPIONs on the fluidity and phase transition of the liposomal membranes prepared with zwitterionic phosphatidylcholine lipids. In order to study if the surface modification of SPIONs has any influence on these membrane properties, we have used four types of differently functionalized SPIONs, such as: plain SPIONs (primary size was shown to bê11 nm), silica-coated SPIONs, SPIONs coated with silica and functionalized with positively charged amino groups or negatively charged carboxyl groups (the primary size of all the surface-modified SPIONs was ~20 nm). Small unilamellar vesicles prepared with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine lipids and multilamellar vesicles prepared with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine lipids were encapsulated or incubated with the plain and surface-modified SPIONs to determine the fluidity and phase transition temperature of the bilayer lipids, respectively. Fluorescent anisotropy and differential scanning calorimetric measurements of the liposomes that were either encapsulated or incubated with the suspension of SPIONs did not show a significant difference in the lipid ordering and fluidity; though the encapsulated SPIONs showed a slightly increased effect on the fluidity of the model membranes in comparison with the incubated SPIONs. This indicates the low potential of the SPIONs to interact with the nontargeted cell membranes, which is a desirable factor for in vivo applications.

  11. Effects of weight loss on erythrocyte membrane composition and fluidity in overweight and moderately obese women.

    PubMed

    Cazzola, Roberta; Rondanelli, Mariangela; Trotti, Rosita; Cestaro, Benvenuto

    2011-04-01

    A previous study showed chemical and physical impairment of the erythrocyte membrane of overweight and moderately obese women. The present study investigated the effects of a low-calorie diet (800 kcal/day deficit for 8 weeks) on erythrocyte membrane properties in 70 overweight and moderately obese (body mass index, 25-33 kg/m(2)) normotensive, nondiabetic women. At the end of dietary intervention, 24.3% of women dropped out, 45.7% lost less than 5% of their initial weight (Group I) and only 30% of patients lost at least 5% of their initial body weight (Group II). Group I showed no significant changes in erythrocyte membrane composition and function. The erythrocyte membranes of Group II showed significant reductions in malondialdehyde, lipofuscin, cholesterol, sphingomyelin, palmitic acid and nervonic acid and an increase in di-homo-γ-linolenic acid, arachidonic acid and membrane fluidity. Moreover, Group II showed an improvement in total cholesterol, low-density lipoprotein cholesterol, glycemia and insulin resistance. These changes in erythrocyte membrane composition could reflect a virtuous cycle resulting from the reduction in insulin resistance associated with increased membrane fluidity that, in turn, results in a sequence of metabolic events that concur to further improve membrane fluidity.

  12. Membrane fluidity of halophilic ectoine-secreting bacteria related to osmotic and thermal treatment.

    PubMed

    Bergmann, Sven; David, Florian; Clark, Wiebke; Wittmann, Christoph; Krull, Rainer

    2013-12-01

    In response to sudden decrease in osmotic pressure, halophilic microorganisms secrete their accumulated osmolytes. This specific stress response, combined with physiochemical responses to the altered environment, influence the membrane properties and integrity of cells, with consequent effects on growth and yields in bioprocesses, such as bacterial milking. The aim of this study was to investigate changes in membrane fluidity and integrity induced by environmental stress in ectoine-secreting organisms. The halophilic ectoine-producing strains Alkalibacillus haloalkaliphilus and Chromohalobacter salexigens were treated hypo- and hyper-osmotically at several temperatures. The steady-state anisotropy of fluorescently labeled cells was measured, and membrane integrity assessed by flow cytometry and ectoine distribution. Strong osmotic downshocks slightly increased the fluidity of the bacterial membranes. As the temperature increased, the increasing membrane fluidity encouraged more ectoine release under the same osmotic shock conditions. On the other hand, combined shock treatments increased the number of disintegrated cells. From the ectoine release and membrane integrity measurements under coupled thermal and osmotic shock conditions, we could optimize the secretion conditions for both bacteria.

  13. Influence of MLS laser radiation on erythrocyte membrane fluidity and secondary structure of human serum albumin.

    PubMed

    Pasternak, Kamila; Nowacka, Olga; Wróbel, Dominika; Pieszyński, Ireneusz; Bryszewska, Maria; Kujawa, Jolanta

    2014-03-01

    The biostimulating activity of low level laser radiation of various wavelengths and energy doses is widely documented in the literature, but the mechanisms of the intracellular reactions involved are not precisely known. The aim of this paper is to evaluate the influence of low level laser radiation from an multiwave locked system (MLS) of two wavelengths (wavelength = 808 nm in continuous emission and 905 nm in pulsed emission) on the human erythrocyte membrane and on the secondary structure of human serum albumin (HSA). Human erythrocytes membranes and HSA were irradiated with laser light of low intensity with surface energy density ranging from 0.46 to 4.9 J cm(-2) and surface energy power density 195 mW cm(-2) (1,000 Hz) and 230 mW cm(-2) (2,000 Hz). Structural and functional changes in the erythrocyte membrane were characterized by its fluidity, while changes in the protein were monitored by its secondary structure. Dose-dependent changes in erythrocyte membrane fluidity were induced by near-infrared laser radiation. Slight changes in the secondary structure of HSA were also noted. MLS laser radiation influences the structure and function of the human erythrocyte membrane resulting in a change in fluidity.

  14. Decreased fluidity of cell membranes causes a metal ion deficiency in recombinant Saccharomyces cerevisiae producing carotenoids.

    PubMed

    Liu, Peitong; Sun, Liang; Sun, Yuxia; Shang, Fei; Yan, Guoliang

    2016-04-01

    The genome-wide transcriptional responses of S. cerevisiae to heterologous carotenoid biosynthesis were investigated using DNA microarray analysis. The results show that the genes involved in metal ion transport were specifically up-regulated in the recombinant strain, and metal ions, including Cu(2+), Fe(2+), Mn(2+), and Mg(2+), were deficient in the recombinant strain compared to the ion content of the parent strain. The decrease in metal ions was ascribed to a decrease in cell membrane (CM) fluidity caused by lower levels of unsaturated fatty acids and ergosterol. This was confirmed by the observation that metal ion levels were restored when CM fluidity was increased by supplying linoleic acid. In addition, a 24.3 % increase in the β-carotene concentration was observed. Collectively, our results suggest that heterologous production of carotenoids in S. cerevisiae can induce cellular stress by rigidifying the CM, which can lead to a deficiency in metal ions. Due to the importance of CM fluidity in cellular physiology, maintaining normal CM fluidity might be a potential approach to improving carotenoid production in genetically engineered S. cerevisiae.

  15. Electron paramagnetic resonance studies of membrane fluidity in ozone-treated erythrocytes and liposomes.

    PubMed

    Wróbel, A; Gomułkiewicz, J

    1999-01-01

    Doxyl stearate spin probes which differed in the attachment of the nitroxide free radical to the fatty acid have been used to study membrane fluidity in ozone-treated bovine erythrocytes and liposomes. Analysis of EPR spectra of spin labels incorporated into lipid bilayer of the erythrocyte membranes indicates an increase in the mobility and decrease in the order of membrane lipids. In isolated erythrocyte membranes (ghosts) the most significant changes were observed for 16-doxylstearic acid. In intact erythrocytes statistically significant were differences for 5-doxylstearic acid. The effect of ozone on liposomes prepared from a lipid extract of erythrocyte lipids was marked in the membrane microenvironment sampled by all spin probes. Ozone apparently leads to alterations of membrane dynamics and structure but does not cause increased rigidity of the membrane.

  16. The Effect of Lidocaine · HCl on the Fluidity of Native and Model Membrane Lipid Bilayers

    PubMed Central

    Park, Jun-Seop; Jung, Tae-Sang; Noh, Yang-Ho; Kim, Woo-Sung; Park, Won-Ick; Kim, Young-Soo; Chung, In-Kyo; Sohn, Uy Dong; Bae, Soo-Kyung

    2012-01-01

    The purpose of this study is to investigated the mechanism of pharmacological action of local anesthetic and provide the basic information about the development of new effective local anesthetics. Fluorescent probe techniques were used to evaluate the effect of lidocaine·HCl on the physical properties (transbilayer asymmetric lateral and rotational mobility, annular lipid fluidity and protein distribution) of synaptosomal plasma membrane vesicles (SPMV) isolated from bovine cerebral cortex, and liposomes of total lipids (SPMVTL) and phospholipids (SPMVPL) extracted from the SPMV. An experimental procedure was used based on selective quenching of 1,3-di(1-pyrenyl)propane (Py-3-Py) and 1,6-diphenyl-1,3,5-hexatriene (DPH) by trinitrophenyl groups, and radiationless energy transfer from the tryptophans of membrane proteins to Py-3-Py. Lidocaine·HCl increased the bulk lateral and rotational mobility of neuronal and model membrane lipid bilayes, and had a greater fluidizing effect on the inner monolayer than the outer monolayer. Lidocaine·HCl increased annular lipid fluidity in SPMV lipid bilayers. It also caused membrane proteins to cluster. The most important finding of this study is that there is far greater increase in annular lipid fluidity than that in lateral and rotational mobilities by lidocaine·HCl. Lidocaine·HCl alters the stereo or dynamics of the proteins in the lipid bilayers by combining with lipids, especially with the annular lipids. In conclusion, the present data suggest that lidocaine, in addition to its direct interaction with proteins, concurrently interacts with membrane lipids, fluidizing the membrane, and thus inducing conformational changes of proteins known to be intimately associated with membrane lipid. PMID:23269904

  17. Cytoplasmic calcium levels and membrane fluidity of platelets in contact with polyether-polyamide multiblock-copolymer surfaces.

    PubMed

    Yui, N; Okano, T; Sakurai, Y; Kora, S; Ishikawa, K; Hiranuma, T; Yamashita, S

    1996-02-01

    Cytoplasmic calcium levels and the membrane fluidity of rabbit platelets stored in mini blood bags of crystalline-amorphous microstructured polymers (polyether-polyamide multiblock-copolymers) were studied. Fluorescent dye (Fura 2 or 1,6-diphenyl-1,3,5-hexatriene)-loaded platelet suspensions were stored at 37 degrees C for 1 h in the blood bags, and metabolic changes in the platelets during storage were evaluated by the fluorescent spectroscopic technique. The surfaces of poly(vinyl chloride) and polyolefin elastomers, which are used for commercially available blood bags, enhanced the progress of platelet metabolism; i.e., there was a dramatic decrease in membrane fluidity and an increase in [Ca2+]i. Furthermore, the decrease in membrane fluidity was observed prior to the increase in [Ca2+]i. These results suggest that the decrease in membrane fluidity of platelets in contact with polymer surfaces can be the dominant stage in the activation of these platelets. In contrast, the surfaces of polyether-polyamide multiblock-copolymers exhibited few changes in either membrane fluidity or [Ca2+]i levels. These results suggest that the platelets in contact with the crystalline-amorphous microstructured copolymer surfaces can be inert and inactivated in terms of the prevention of a decrease in membrane fluidity.

  18. Effect of Gold Nanoparticle on Structure and Fluidity of Lipid Membrane

    PubMed Central

    Mhashal, Anil R.; Roy, Sudip

    2014-01-01

    This paper deals with the effect of different size gold nanoparticles on the fluidity of lipid membrane at different regions of the bilayer. To investigate this, we have considered significantly large bilayer leaflets and incorporated only one nanoparticle each time, which was subjected to all atomistic molecular dynamics simulations. We have observed that, lipid molecules located near to the gold nanoparticle interact directly with it, which results in deformation of lipid structure and slower dynamics of lipid molecules. However, lipid molecules far away from the interaction site of the nanoparticle get perturbed, which gives rise to increase in local ordering of the lipid domains and decrease in fluidity. The bilayer thickness and area per head group in this region also get altered. Similar trend, but with different magnitude is also observed when different size nanoparticle interact with the bilayer. PMID:25469786

  19. Electron paramagnetic resonance investigation on modulatory effect of benidipine on membrane fluidity of erythrocytes in essential hypertension.

    PubMed

    Tsuda, Kazushi

    2008-03-01

    It has been shown that benidipine, a long-lasting calcium (Ca) channel blocker, may exert its protective effect against vascular disorders by increasing nitric oxide (NO) production. The purpose of the present study was to investigate whether orally administered benidipine might influence the membrane function in patients with essential hypertension. We measured the membrane fluidity of erythrocytes by using an electron paramagnetic resonance (EPR) and spin-labeling method. In the preliminary study using erythrocytes obtained from healthy volunteers, benidipine decreased the order parameter (S) for 5-nitroxide stearate (5-NS) and the peak height ratio (ho/h-1) for 16-NS in the EPR spectra in vitro. The finding indicated that benidipine increased the membrane fluidity and improved the microviscosity of erythrocytes. In addition, it was demonstrated that the effect of benidipine on membrane fluidity of erythrocytes was significantly potentiated by the NO-substrate, L-arginine. In the separate series of the study, we observed that orally administered benidipine for 4 weeks significantly increased the membrane fluidity of erythrocytes with a concomitant increase in plasma NO metabolite levels in hypertensive subjects. The results of the present study demonstrated that benidipine might increase the membrane fluidity and improve the microviscosity of erythrocytes both in vitro and in vivo, to some extent, by the NO-dependent mechanism. Furthermore, it is strongly suggested that orally administered benidipine might have a beneficial effect on the rheologic behavior of erythrocytes and the improvement of the microcirculation in hypertensive subjects.

  20. Pancreatic β-Cell Membrane Fluidity and Toxicity Induced by Human Islet Amyloid Polypeptide Species

    PubMed Central

    Pilkington, Emily H.; Gurzov, Esteban N.; Kakinen, Aleksandr; Litwak, Sara A.; Stanley, William J.; Davis, Thomas P.; Ke, Pu Chun

    2016-01-01

    Aggregation of human islet amyloid polypeptide (hIAPP) into fibrils and plaques is associated with pancreatic β-cell loss in type 2 diabetes (T2D). However, due to the rapidness of hIAPP conversion in aqueous phase, exactly which hIAPP species is responsible for the observed toxicity and through what mechanisms remains ambiguous. In light of the importance of understanding hIAPP toxicity for T2D here we show a biophysical scheme based on the use of a lipophilic Laurdan dye for examining MIN6 cell membranes upon exposure to fresh and oligomeric hIAPP as well as mature amyloid. It has been found that all three hIAPP species, especially fresh hIAPP, enhanced membrane fluidity and caused losses in cell viability. The cell generation of reactive oxygen species (ROS), however, was the most pronounced with mature amyloid hIAPP. The correlation between changes in membrane fluidity and cell viability and their lack of correlation with ROS production suggest hIAPP toxicity is elicited through both physical and biochemical means. This study offers a new insight into β-cell toxicity induced by controlled hIAPP species, as well as new biophysical methodologies that may prove beneficial for the studies of T2D as well as neurological disorders. PMID:26880502

  1. Pancreatic β-Cell Membrane Fluidity and Toxicity Induced by Human Islet Amyloid Polypeptide Species

    NASA Astrophysics Data System (ADS)

    Pilkington, Emily H.; Gurzov, Esteban N.; Kakinen, Aleksandr; Litwak, Sara A.; Stanley, William J.; Davis, Thomas P.; Ke, Pu Chun

    2016-02-01

    Aggregation of human islet amyloid polypeptide (hIAPP) into fibrils and plaques is associated with pancreatic β-cell loss in type 2 diabetes (T2D). However, due to the rapidness of hIAPP conversion in aqueous phase, exactly which hIAPP species is responsible for the observed toxicity and through what mechanisms remains ambiguous. In light of the importance of understanding hIAPP toxicity for T2D here we show a biophysical scheme based on the use of a lipophilic Laurdan dye for examining MIN6 cell membranes upon exposure to fresh and oligomeric hIAPP as well as mature amyloid. It has been found that all three hIAPP species, especially fresh hIAPP, enhanced membrane fluidity and caused losses in cell viability. The cell generation of reactive oxygen species (ROS), however, was the most pronounced with mature amyloid hIAPP. The correlation between changes in membrane fluidity and cell viability and their lack of correlation with ROS production suggest hIAPP toxicity is elicited through both physical and biochemical means. This study offers a new insight into β-cell toxicity induced by controlled hIAPP species, as well as new biophysical methodologies that may prove beneficial for the studies of T2D as well as neurological disorders.

  2. Inhibition of HIV-1 entry by the tricyclic coumarin GUT-70 through the modification of membrane fluidity

    SciTech Connect

    Matsuda, Kouki; Hattori, Shinichiro; Kariya, Ryusho; Komizu, Yuji; Kudo, Eriko; Goto, Hiroki; Taura, Manabu; Ueoka, Ryuichi; Kimura, Shinya; Okada, Seiji

    2015-02-13

    Membrane fusion between host cells and HIV-1 is the initial step in HIV-1 infection, and plasma membrane fluidity strongly influences infectivity. In the present study, we demonstrated that GUT-70, a natural product derived from Calophyllum brasiliense, stabilized plasma membrane fluidity, inhibited HIV-1 entry, and down-regulated the expression of CD4, CCR5, and CXCR4. Since GUT-70 also had an inhibitory effect on viral replication through the inhibition of NF-κB, it is expected to be used as a dual functional and viral mutation resistant reagent. Thus, these unique properties of GUT-70 enable the development of novel therapeutic agents against HIV-1 infection.

  3. Plasma membrane order and fluidity are diversely triggered by elicitors of plant defence

    PubMed Central

    Sandor, Roman; Der, Christophe; Grosjean, Kevin; Anca, Iulia; Noirot, Elodie; Leborgne-Castel, Nathalie; Lochman, Jan; Simon-Plas, Françoise; Gerbeau-Pissot, Patricia

    2016-01-01

    Although plants are exposed to a great number of pathogens, they usually defend themselves by triggering mechanisms able to limit disease development. Alongside signalling events common to most such incompatible interactions, modifications of plasma membrane (PM) physical properties could be new players in the cell transduction cascade. Different pairs of elicitors (cryptogein, oligogalacturonides, and flagellin) and plant cells (tobacco and Arabidopsis) were used to address the issue of possible modifications of plant PM biophysical properties induced by elicitors and their links to other events of the defence signalling cascade. We observed an increase of PM order whatever the elicitor/plant cell pair used, provided that a signalling cascade was induced. Such membrane modification is dependent on the NADPH oxidase-mediated reactive oxygen species production. Moreover, cryptogein, which is the sole elicitor able to trap sterols, is also the only one able to trigger an increase in PM fluidity. The use of cryptogein variants with altered sterol-binding properties confirms the strong correlation between sterol removal from the PM and PM fluidity enhancement. These results propose PM dynamics as a player in early signalling processes triggered by elicitors of plant defence. PMID:27604805

  4. Plasma membrane order and fluidity are diversely triggered by elicitors of plant defence.

    PubMed

    Sandor, Roman; Der, Christophe; Grosjean, Kevin; Anca, Iulia; Noirot, Elodie; Leborgne-Castel, Nathalie; Lochman, Jan; Simon-Plas, Françoise; Gerbeau-Pissot, Patricia

    2016-09-01

    Although plants are exposed to a great number of pathogens, they usually defend themselves by triggering mechanisms able to limit disease development. Alongside signalling events common to most such incompatible interactions, modifications of plasma membrane (PM) physical properties could be new players in the cell transduction cascade. Different pairs of elicitors (cryptogein, oligogalacturonides, and flagellin) and plant cells (tobacco and Arabidopsis) were used to address the issue of possible modifications of plant PM biophysical properties induced by elicitors and their links to other events of the defence signalling cascade. We observed an increase of PM order whatever the elicitor/plant cell pair used, provided that a signalling cascade was induced. Such membrane modification is dependent on the NADPH oxidase-mediated reactive oxygen species production. Moreover, cryptogein, which is the sole elicitor able to trap sterols, is also the only one able to trigger an increase in PM fluidity. The use of cryptogein variants with altered sterol-binding properties confirms the strong correlation between sterol removal from the PM and PM fluidity enhancement. These results propose PM dynamics as a player in early signalling processes triggered by elicitors of plant defence.

  5. FT-IR Investigations Into The Fluidity Of Lipopolysaccharide And Lipid A Membrane Systems

    NASA Astrophysics Data System (ADS)

    Brandenburg, K.; Seydel, U.

    1989-12-01

    Lipopolysaccharides (LPS) are the major amphiphilic components of the outer membrane of Gram-negative bacteria. They are composed of a poly- or oligosaccharide portion being covalently linked to a lipid moiety called lipid A. LPS are also called endotoxins because of their ability to induce harmful effects in organisms. However, they also exhibit beneficial ('adjuvant') activity for example by stimulating the immune system and inducing the production of e.g. the tumor necrosis factor and interleukin 1. The mechanisms leading to a stimulation of the cells of the immune system should mainly be governed by the fluidity and/or the supramolecular structure of the LPS and lipid A assemblies interacting with the cell membrane. In this contribution we report on FT-IR measurements of the fluidity of various LPS and of some lipid A's, and on the influence of the concentration of divalent cations, pH and water content on this parameter. The LPS differ in the headgroup conformation/composition, i.e in the length of the sugar moiety. The lipid A's show variation in their acylation patterns.

  6. Detection of Membrane Fluidity in Submitochondrial Particles of Platelets and Erythrocyte Membranes from Mexican Patients with Alzheimer Disease by Intramolecular Excimer Formation of 1,3 Dipyrenylpropane

    PubMed Central

    Ortiz, G.G.; Pacheco-Moisés, F.; El Hafidi, M.; Jiménez-Delgado, A.; Macías-Islas, M. A.; Corral, S. A. Rosales; de la Rosa, A. Célis; Sánchez-González, V. J.; Arias-Merino, E. D.; Velázquez-Brizuela, I. E.

    2008-01-01

    It has been suggested that mitochondrial dysfunction and defects in membrane structure could be implied in AD pathogenesis. The aim of the present work was the study of membrane fluidity in submitochondrial platelet particles and erythrocyte membranes from Mexican patients. Blood samples were obtained from 30 patients with Alzheimer disease and 30 aged-matched control subjects. Membrane fluidity determinations were done using a very low concentration of the fluorescent dipyrenylpropane probe incorporated in both types of membranes. This probe is able to give excimer and monomer fluorescence, therefore it can be used to monitor fluidity changes in biological membranes. The data obtained showed that in submitochondrial particles from AD patients, the excimer to monomer fluorescent intensity ratio was lower (0.231 ± 0.008) than aged-matched control subjects (0.363 ± 0.014). Therefore, membrane fluidity was lower in AD samples. On the other hand, we found similar membrane fluidity in erythrocytes from AD patients and aged-matched controls: the fluorescent intensity ratios were 0.312 ± 0.03 and 0.305 ± 0.033, respectively. In addition, lipid peroxidation in submitochondrial particles and erythrocyte membranes was higher in AD samples than in aged-matched controls. These data suggest that submitochondrial platelet particles are more sensitive to oxidative stress than erythrocyte membranes. PMID:18334736

  7. Formation and fluidity measurement of supported lipid bilayer on polyvinyl chloride membrane

    NASA Astrophysics Data System (ADS)

    Kobayashi, Takuji; Kono, Akiteru; Futagawa, Masato; Sawada, Kazuaki; Tero, Ryugo

    2014-02-01

    We prepared an artificial lipid bilayer on a plasticized poly(vinyl chloride) (PVC) membrane on a Si3N4 layer deposited on a Si wafer. We optimized the experimental condition for the fabrication of the PVC membrane, and obtained a PVC membrane with a flat and uniform surface on the scale of several hundreds of micrometer suitable for a substrate for supported lipid bilayers (SLBs). The SLB of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) was formed on the PVC membrane by the vesicle fusion method. The observation with a conventional epi-fluorescence microscope and a confocal laser scanning microscope gave geometrically uniform images of the SLB on the PVC membrane. The fluidity and the mobile fraction of the SLB was evaluated by the fluorescence recovery after photobleaching method, and compared with that on a thermally oxidized SiO2/Si substrate. The SLB on the PVC membrane contained immobile fraction ˜30%, but the diffusion in the mobile fraction was two times faster than that in the SLB on SiO2/Si, which had little immobile fraction.

  8. Estradiol Modulates Membrane-Linked ATPases, Antioxidant Enzymes, Membrane Fluidity, Lipid Peroxidation, and Lipofuscin in Aged Rat Liver

    PubMed Central

    Kumar, Pardeep; Kale, R. K.; Baquer, Najma Zaheer

    2011-01-01

    Free radical production and oxidative stress are known to increase in liver during aging, and may contribute to the oxidative damage. These changes increase during menopausal condition in females when the level of estradiol is decreased. The objective of this study was to observe the changes in activities of membrane linked ATPases (Na+K+ ATPase, Ca2+ ATPase), antioxidant enzymes (superoxide dismutase, glutathione-S-transferase), lipid peroxidation levels, lipofuscin content and membrane fluidity occurring in livers of female rats of 3, 12 and 24 months age groups, and to see whether these changes are restored to 3 months control levels rats after exogenous administration of 17-β-estradiol (E2). The aged rats (12 and 24 months) were given subcutaneous injection of E2 (0.1 μg/g body weight) daily for one month. The results obtained in the present work revealed that normal aging was associated with significant decrease in the activities of membrane linked ATPases, antioxidant enzymes, membrane fluidity and an increase in lipid peroxidation and lipofuscin content in livers of aging female rats. The present study showed that E2 treatment reversed the changes to normal levels. E2 treatment may be beneficial in preventing some of the age related changes in the liver by increasing antioxidant defenses. PMID:22007298

  9. Stabilizing effects of coenzyme Q10 on potassium ion release, membrane potential and fluidity of rabbit red blood cells.

    PubMed

    Shinozawa, S; Araki, Y; Oda, T

    1980-09-01

    The effects of coenzyme Q10 (Co Q10) on potassium ion release, membrane potential and fluidity of rabbit red blood cells were studied. Co Q10 inhibited the increased potassium ion release induced by cetylamine or lysolecithin from the cells. Co Q10 slightly decreased the membrane potential monitored by changes in fluorescence intensity of cyanine dye, 3,3'-dipropyl-2,2'-thiodicarbocyanine iodide [diS-C3-(5)], and also slightly decreased the membrane fluidity measured by using 1,6-diphenyl-1,3,5-hexatriene (DPH). These effects of Co Q10 on the membrane are considered to be due to its membrane stabilizing activity by interaction with lipid bilayers of the membrane.

  10. Membrane fluidity profiles as deduced by saturation-recovery EPR measurements of spin-lattice relaxation times of spin labels.

    PubMed

    Mainali, Laxman; Feix, Jimmy B; Hyde, James S; Subczynski, Witold K

    2011-10-01

    There are no easily obtainable EPR spectral parameters for lipid spin labels that describe profiles of membrane fluidity. The order parameter, which is most often used as a measure of membrane fluidity, describes the amplitude of wobbling motion of alkyl chains relative to the membrane normal and does not contain explicitly time or velocity. Thus, this parameter can be considered as nondynamic. The spin-lattice relaxation rate (T(1)(-1)) obtained from saturation-recovery EPR measurements of lipid spin labels in deoxygenated samples depends primarily on the rotational correlation time of the nitroxide moiety within the lipid bilayer. Thus, T(1)(-1) can be used as a convenient quantitative measure of membrane fluidity that reflects local membrane dynamics. T(1)(-1) profiles obtained for 1-palmitoyl-2-(n-doxylstearoyl)phosphatidylcholine (n-PC) spin labels in dimyristoylphosphatidylcholine (DMPC) membranes with and without 50 mol% cholesterol are presented in parallel with profiles of the rotational diffusion coefficient, R(⊥), obtained from simulation of EPR spectra using Freed's model. These profiles are compared with profiles of the order parameter obtained directly from EPR spectra and with profiles of the order parameter obtained from simulation of EPR spectra. It is shown that T(1)(-1) and R(⊥) profiles reveal changes in membrane fluidity that depend on the motional properties of the lipid alkyl chain. We find that cholesterol has a rigidifying effect only to the depth occupied by the rigid steroid ring structure and a fluidizing effect at deeper locations. These effects cannot be differentiated by profiles of the order parameter. All profiles in this study were obtained at X-band (9.5 GHz).

  11. Number of free hydroxyl groups on bile acid phospholipids determines the fluidity and hydration of model membranes.

    PubMed

    Sreekanth, Vedagopuram; Bajaj, Avinash

    2013-10-10

    Interactions of synthetic phospholipids with model membranes determines the drug release capabilities of phospholipid vesicles at diseased sites. We performed 1,6-diphenyl-1,3,5-hexatriene (DPH)-based fluorescence anisotropy, Laurdan-based membrane hydration, and differential scanning calorimetry (DSC) studies to cognize the interactions of three bile acid phospholipids, lithocholic acid-phosphocholine (LCA-PC), deoxycholic acid-phosphocholine (DCA-PC), and cholic acid-phosphocholine (CA-PC) with model membranes. These studies revealed that bile acid phospholipids increases membrane fluidity in DCA-PC > CA-PC > LCA-PC order, indicating that induction of membrane fluidity is contingent on the number and positioning of free hydroxyl groups on bile acids. Similarly, DCA-PC causes maximum membrane perturbations due to the presence of a free hydroxyl group, whereas LCA-PC induces gel phase in membranes due to hydrophobic bile acid acyl chain interactions. These DCA-PC-induced membrane perturbations induce a drastic decrease in phase transition temperature (Tm) as determined by calorimetric studies, whereas doping of LCA-PC causes phase transition broadening without change in Tm. Doping of CA-PC induces membrane perturbations and membrane hydration like DCA-PC but sharpening of phase transition at higher doping suggests self-association of CA-PC molecules. Therefore these differential mode of interactions between bile acid phospholipids and model membranes would help in the future for their use in drug delivery.

  12. Unsaturated Fatty Acids Drive Disintegrin and Metalloproteinase (ADAM)-dependent Cell Adhesion, Proliferation, and Migration by Modulating Membrane Fluidity*

    PubMed Central

    Reiss, Karina; Cornelsen, Isabell; Husmann, Matthias; Gimpl, Gerald; Bhakdi, Sucharit

    2011-01-01

    The disintegrin-metalloproteinases ADAM10 and ADAM17 mediate the release of several cell signaling molecules and cell adhesion molecules such as vascular endothelial cadherin or L-selectin affecting endothelial permeability and leukocyte transmigration. Dysregulation of ADAM activity may contribute to the pathogenesis of vascular diseases, but the mechanisms underlying the control of ADAM functions are still incompletely understood. Atherosclerosis is characterized by lipid plaque formation and local accumulation of unsaturated free fatty acids (FFA). Here, we show that unsaturated FFA increase ADAM-mediated substrate cleavage. We demonstrate that these alterations are not due to genuine changes in enzyme activity, but correlate with changes in membrane fluidity as revealed by measurement of 1,6-diphenyl-1,3,5-hexatriene fluorescence anisotropy and fluorescence recovery after photobleaching analyses. ELISA and immunoblot experiments conducted with granulocytes, endothelial cells, and keratinocytes revealed rapid increase of ectodomain shedding of ADAM10 and ADAM17 substrates upon membrane fluidization. Large amounts of unsaturated FFA may be liberated from cholesteryl esters in LDL that is entrapped in atherosclerotic lesions. Incubation of cells with thus modified LDL resulted in rapid cleavage of ADAM substrates with corresponding functional consequences on cell proliferation, cell migration, and endothelial permeability, events of high significance in atherogenesis. We propose that FFA represent critical regulators of ADAM function that may assume relevance in many biological settings through their influence on mobility of enzyme and substrate in lipid bilayers. PMID:21642425

  13. Unsaturated fatty acids drive disintegrin and metalloproteinase (ADAM)-dependent cell adhesion, proliferation, and migration by modulating membrane fluidity.

    PubMed

    Reiss, Karina; Cornelsen, Isabell; Husmann, Matthias; Gimpl, Gerald; Bhakdi, Sucharit

    2011-07-29

    The disintegrin-metalloproteinases ADAM10 and ADAM17 mediate the release of several cell signaling molecules and cell adhesion molecules such as vascular endothelial cadherin or L-selectin affecting endothelial permeability and leukocyte transmigration. Dysregulation of ADAM activity may contribute to the pathogenesis of vascular diseases, but the mechanisms underlying the control of ADAM functions are still incompletely understood. Atherosclerosis is characterized by lipid plaque formation and local accumulation of unsaturated free fatty acids (FFA). Here, we show that unsaturated FFA increase ADAM-mediated substrate cleavage. We demonstrate that these alterations are not due to genuine changes in enzyme activity, but correlate with changes in membrane fluidity as revealed by measurement of 1,6-diphenyl-1,3,5-hexatriene fluorescence anisotropy and fluorescence recovery after photobleaching analyses. ELISA and immunoblot experiments conducted with granulocytes, endothelial cells, and keratinocytes revealed rapid increase of ectodomain shedding of ADAM10 and ADAM17 substrates upon membrane fluidization. Large amounts of unsaturated FFA may be liberated from cholesteryl esters in LDL that is entrapped in atherosclerotic lesions. Incubation of cells with thus modified LDL resulted in rapid cleavage of ADAM substrates with corresponding functional consequences on cell proliferation, cell migration, and endothelial permeability, events of high significance in atherogenesis. We propose that FFA represent critical regulators of ADAM function that may assume relevance in many biological settings through their influence on mobility of enzyme and substrate in lipid bilayers.

  14. Modulation of arachidonic acid release and membrane fluidity by albumin in vascular smooth muscle and endothelial cells.

    PubMed

    Beck, R; Bertolino, S; Abbot, S E; Aaronson, P I; Smirnov, S V

    1998-11-02

    Albumin is the major plasma protein circulating in blood. Albumin potently decreases capillary permeability, although the mechanisms are not understood completely. Albumin also effectively binds arachidonic acid (AA), which increases capillary permeability. To investigate the interactions of BSA and AA with the cell membrane, the effect of these substances on [3H]AA release and membrane fluidity was studied in vascular myocytes and endothelial cells. BSA (0.2 and 1 mg . mL-1) stimulated a significant release of [3H]AA from both intact rat aorta and cultured smooth muscle cells. This effect was not mimicked by gamma-globulin or myoglobin (both 1 mg . mL-1) in intact tissue. BSA, but not gamma-globulin and myoglobin, decreased the membrane fluidity (assessed as changes in the steady-state fluorescence anisotropy of 1,6-diphenyl-1,3, 5-hexatriene) in a concentration-dependent manner with a half-maximum concentration between 0.007 and 0.4 mg . mL-1 in both freshly isolated and cultured rat aortic myocytes and human umbilical vein endothelial cells. AA (1 to 200 micromol/L) caused the opposite effect, increasing membrane fluidity and antagonizing the effect of BSA. BSA modified at its arginine residues, which are thought to be important in AA binding, did not stimulate [3H]AA release and was significantly less potent than native BSA in altering the membrane fluidity. The effect of BSA can be explained by a high-affinity binding of AA to the protein and extraction of AA from the cell membrane. The interaction between BSA and AA could play a role in the regulation of vascular permeability.

  15. RhoA and Membrane Fluidity Mediates the Spatially Polarized Src/FAK Activation in Response to Shear Stress

    PubMed Central

    Liu, Bo; Lu, Shaoying; Hu, Ying-li; Liao, Xiaoling; Ouyang, Mingxing; Wang, Yingxiao

    2014-01-01

    While Src plays crucial roles in shear stress-induced cellular processes, little is known on the spatiotemporal pattern of high shear stress (HSS)-induced Src activation. HSS (65 dyn/cm2) was applied on bovine aortic endothelial cells to visualize the dynamic Src activation at subcellular levels utilizing a membrane-targeted Src biosensor (Kras-Src) based on fluorescence resonance energy transfer (FRET). A polarized Src activation was observed with higher activity at the side facing the flow, which was enhanced by a cytochalasin D-mediated disruption of actin filaments but inhibited by a benzyl alcohol-mediated enhancement of membrane fluidity. Further experiments revealed that HSS decreased RhoA activity, with a constitutively active RhoA mutant inhibiting while a negative RhoA mutant enhancing the HSS-induced Src polarity. Cytochalasin D can restore the polarity in cells expressing the active RhoA mutant. Further results indicate that HSS stimulates FAK activation with a spatial polarity similar to Src. The inhibition of Src by PP1, as well as the perturbation of RhoA activity and membrane fluidity, can block this HSS-induced FAK polarity. These results indicate that the HSS-induced Src and subsequently FAK polarity depends on the coordination between intracellular tension distribution regulated by RhoA, its related actin structures and the plasma membrane fluidity. PMID:25387906

  16. Tolerance to chitosan by Trichoderma species is associated with low membrane fluidity.

    PubMed

    Zavala-González, Ernesto A; Lopez-Moya, Federico; Aranda-Martinez, Almudena; Cruz-Valerio, Mayra; Lopez-Llorca, Luis Vicente; Ramírez-Lepe, Mario

    2016-07-01

    The effect of chitosan on growth of Trichoderma spp., a cosmopolitan genus widely exploited for their biocontrol properties was evaluated. Based on genotypic (ITS of 18S rDNA) characters, four isolates of Trichoderma were identified as T. pseudokoningii FLM16, T. citrinoviride FLM17, T. harzianum EZG47, and T. koningiopsis VSL185. Chitosan reduces radial growth of Trichoderma isolates in concentration-wise manner. T. koningiopsis VSL185 was the most chitosan tolerant isolate in all culture media amended with chitosan (0.5-2.0 mg ml(-1) ). Minimal Inhibitory Concentration (MIC) and Minimal Fungicidal Concentration (MFC) were determined showing that T. koningiopsis VSL185 displays higher chitosan tolerance with MIC value >2000 μg ml(-1) while for other Trichoderma isolates MIC values were around 10 μg ml(-1) . Finally, free fatty acid composition reveals that T. koningiopsis VSL185, chitosan tolerant isolate, displays lower linolenic acid (C18:3) content than chitosan sensitive Trichoderma isolates. Our findings suggest that low membrane fluidity is associated with chitosan tolerance in Trichoderma spp.

  17. Growth and membrane fluidity of food-borne pathogen Listeria monocytogenes in the presence of weak acid preservatives and hydrochloric acid.

    PubMed

    Diakogiannis, Ioannis; Berberi, Anita; Siapi, Eleni; Arkoudi-Vafea, Angeliki; Giannopoulou, Lydia; Mastronicolis, Sofia K

    2013-01-01

    This study addresses a major issue in microbial food safety, the elucidation of correlations between acid stress and changes in membrane fluidity of the pathogen Listeria monocytogenes. In order to assess the possible role that membrane fluidity changes play in L. monocytogenes tolerance to antimicrobial acids (acetic, lactic, hydrochloric acid at low pH or benzoic acid at neutral pH), the growth of the bacterium and the gel-to-liquid crystalline transition temperature point (T m) of cellular lipids of each adapted culture was measured and compared with unexposed cells. The T m of extracted lipids was measured by differential scanning calorimetry. A trend of increasing T m values but not of equal extent was observed upon acid tolerance for all samples and this increase is not directly proportional to each acid antibacterial action. The smallest increase in T m value was observed in the presence of lactic acid, which presented the highest antibacterial action. In the presence of acids with high antibacterial action such as acetic, hydrochloric acid or low antibacterial action such as benzoic acid, increased T m values were measured. The T m changes of lipids were also correlated with our previous data about fatty acid changes to acid adaptation. The results imply that the fatty acid changes are not the sole adaptation mechanism for decreased membrane fluidity (increased T m). Therefore, this study indicates the importance of conducting an in-depth structural study on how acids commonly used in food systems affect the composition of individual cellular membrane lipid molecules.

  18. Membrane fluidity and surface changes during initiation of 1,2 dimethylhydrazine-induced colon carcinogenesis: protection by zinc.

    PubMed

    Chadha, Vijayta Dani; Dhawan, D K

    2009-01-01

    The present study evaluated the modulatory effects of zinc on colonic membrane fluidity and surface abnormalities following 1,2 dimethylhydrazine (DMH)-induced colon carcinogenesis. Rats were segregated into four groups: normal control, DMH treated, zinc treated, DMH + zinc treated. Colon carcinogenesis was initiated through weekly subcutaneous injections of DMH (30 mg/kg body weight) for 8 weeks. Zinc (in the form of zinc sulphate) was supplemented to rats at a dose level of 227 mg/L in drinking water, ad libitum, for the entire duration of the study. Brush border membranes (BBM) were isolated from the colon of rats and the fluidity parameters were assessed by steady-state fluorescence polarization technique using the membrane extrinsic fluorophore 1,6-diphenyl-1,3,5-hexatriene (DPH). The translational diffusion was measured by using the excimer formation of pyrene incorporated in the membrane. The results demonstrated a significant increase in the polarization and anisotropy, accompanied by an increase in order parameter in the membrane preparations from the colon of DMH-injected rats. Further, studies with pyrene fluorophore indicated a marked decrease in membrane microviscosity following DMH treatment. However, the alterations in membrane fluorescence polarization and the fluidity parameters were completely restored following zinc treatment. Drastic alterations in colon surface were noticed after 8 weeks of DMH treatment. However, zinc treatment to DMH-treated rats greatly restored normalcy in the colonic surface. The study concludes that zinc has a strong membrane stabilizing effect and thus has a positive beneficial effect against chemically induced colonic preneoplastic progression in rats.

  19. Toxicity of terpenes on fibroblast cells compared to their hemolytic potential and increase in erythrocyte membrane fluidity.

    PubMed

    Mendanha, Sebastião A; Moura, Soraia S; Anjos, Jorge L V; Valadares, Marize C; Alonso, Antonio

    2013-02-01

    Terpenes are considered potent skin permeation enhancers with low toxicity. Electron paramagnetic resonance (EPR) spectroscopy of the spin label 5-doxyl stearic acid (5-DSA) was used to monitor the effect of sesquiterpene nerolidol and various monoterpenes on membrane fluidity in erythrocyte and fibroblast cells. In addition, the hemolytic levels and cytotoxic effects on cultured fibroblast cells were also measured to investigate possible relationships between the cellular irritation potentials of terpenes and the ability to modify membrane fluidity. All terpenes increased cell membrane fluidity with no significant differences between the monoterpenes, but the effect of sesquiterpene was significantly greater than that of the monoterpenes. The IC(50) values for the terpenes in the cytotoxicity assay indicated that 1,8-cineole showed lower cytotoxicity and α-terpineol and nerolidol showed higher cytotoxicity. The correlation between the hemolytic effect and the IC(50) values for fibroblast viability was low (R=0.61); however, in both tests, nerolidol was among the most aggressive of terpenes and 1,8-cineole was among the least aggressive. Obtaining information concerning the toxicity and potency of terpenes could aid in the design of topical formulations optimized to facilitate drug absorption for the treatment of many skin diseases.

  20. Comparative effects of technical toxaphene, 2,5-dichloro-3-biphenylol and octabromodiphenylether on cell viability, [Ca2+]i levels and membrane fluidity in mouse thymocytes.

    PubMed

    Sandal, Suleyman; Yilmaz, Bayram; Chen, Chang-Hwei; Carpenter, David O

    2004-08-01

    Flow cytometric studies of mouse thymocytes show that technical toxaphene (10-20 ppm) and 2,5-dichloro-3-biphenylol (PCB 9-OH) (5-10 ppm) kill cells and cause an increase in intracellular calcium concentration, [Ca2+]i, whereas commercial octabromodiphenylether (OBDE) has no effect. The cell death is not a result of the rise of [Ca2+]i, since the divalent cation ionophore, ionomycin, causes a large elevation in [Ca2+]i without cell death. We have studied effects of these compounds on membrane fluorescence polarization, a measure of membrane fluidity, using 1,6-diphenyl-1,3,5-hexatriene (DPH). We find that toxaphene causes a decrease in membrane fluidity in the concentration range associated with cell death, whereas PCB 9-OH causes an increase in fluidity and OBDE has no effect. These observations suggest that alterations of membrane fluidity of thymocytes, whether it be an increase or decrease, can cause cytotoxicity.

  1. Effects of exposure to poultry chemical decontaminants on the membrane fluidity of Listeria monocytogenes and Salmonella enterica strains.

    PubMed

    Alonso-Hernando, Alicia; Alonso-Calleja, Carlos; Capita, Rosa

    2010-02-28

    There is a lack of work comparing the influence of various poultry chemical decontaminants on the membrane fluidity of pathogenic bacteria. In order to assess the possible role of physical membrane changes on bacterial adaptation to decontaminants, fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene (DPH) was measured in Listeria monocytogenes and Salmonella enterica strains before and after growth in the presence of increasing sub-lethal concentrations of decontaminants (trisodium phosphate - TSP, acidified sodium chlorite - ASC, citric acid - CA and peroxyacids - PA). Higher (P<0.05) anisotropy values (lower membrane fluidity) were observed, both before and after exposure to decontaminants, in strains of L. monocytogenes (average 0.206+/-0.008) than in those of S. enterica (0.188+/-0.013). Cells exposed to sub-inhibitory concentrations of acid decontaminants (CA or PA) showed higher (P<0.05) anisotropy values and percentages of survival to acid stress than unexposed cells, suggesting that adaptation to these compounds is related to changes in membrane fluidity. Minimal changes in anisotropy values were observed after growth in presence of TSP or ASC. After treatment with strong concentrations of acid decontaminants (0.05 and 1% ASC, 5% and 10% CA, and 0.1 and 0.25% PA) the highest anisotropy values (highest membrane rigidity) were shown by cells previously grown with sub-inhibitory concentrations of CA or PA, suggesting that the synergistic effects of successive applications of various acids should be minimized. Because of the relationship between high membrane rigidity and high resistance to different stresses, the fact that it is essential to ensure adequate, inhibitory, CA or PA concentrations during poultry decontamination treatments is underlined.

  2. Regulation by membrane fluidity of the allosteric behavior of the (Ca2)-adenosine triphosphatase from Escherichia coli.

    PubMed

    Siñeriz, F; Bloj, B; Farías, R N; Trucco, R E

    1973-09-01

    The allosteric properties of the membrane-bound (Ca(2+))-adenosine triphosphatase of an unsaturated fatty acid auxotroph of Escherichia coli were studied in membranes with different fatty acid compositions. The Hill coefficient of the inhibition by Na(+) ranged from 1.4, in the case where the auxotroph was grown with cis-vaccenic acid as supplement, to 2.8 when grown on linolenic acid. The results indicate that no fatty acid is particularly involved in the allosteric phenomena. A correlation between the values of the Hill coefficient and the double bond index or the ratio of the double bond index saturated to the fatty acids of the membrane was found. These facts are interpreted as a modulation by the membrane fluidity of the allosteric behavior of the membrane-bound enzyme. The general biological character of this phenomenon is discussed in this paper.

  3. Association of resistin with impaired membrane fluidity of red blood cells in hypertensive and normotensive men: an electron paramagnetic resonance study.

    PubMed

    Tsuda, Kazushi

    2016-10-01

    Abnormalities in physical properties of the cell membranes may strongly be linked to hypertension. Recent evidence indicates that resistin may actively participate in the pathophysiology of insulin resistance, diabetes mellitus, hypertension and other circulatory disorders. The present study was undertaken to investigate the possible relationships among plasma resistin, oxidative stress and membrane fluidity (a reciprocal value of membrane microviscosity) in hypertension. We measured the membrane fluidity of red blood cells (RBCs) in hypertensive and normotensive men using an electron paramagnetic resonance (EPR) and spin-labeling method. The order parameter (S) for the spin-label agents (5-nitroxide stearate) in EPR spectra of red blood cell (RBC) membranes was significantly higher in hypertensive men than in normotensive men, indicating that membrane fluidity was decreased in hypertension. Plasma resistin levels were correlated with systolic blood pressure and 8-iso-prostaglandin F2α levels (an index of oxidative stress). Furthermore, the order parameter (S) of RBCs significantly correlated with plasma resistin and plasma 8-isoPG F2α, suggesting that reduced membrane fluidity of RBCs might be associated with hyperresistinemia and increased oxidative stress. Multivariate regression analysis showed that, after adjustment for confounding factors, plasma resistin might be an independent determinant of membrane fluidity of RBCs. The EPR study suggests that resistin might have a close correlation with impaired rheologic behavior of RBCs and microcirculatory dysfunction in hypertension, at least in part, via an oxidative stress-dependent mechanism.

  4. Downregulation of ceramide synthase-6 during epithelial-to-mesenchymal transition reduces plasma membrane fluidity and cancer cell motility.

    PubMed

    Edmond, V; Dufour, F; Poiroux, G; Shoji, K; Malleter, M; Fouqué, A; Tauzin, S; Rimokh, R; Sergent, O; Penna, A; Dupuy, A; Levade, T; Theret, N; Micheau, O; Ségui, B; Legembre, P

    2015-02-19

    Epithelial-to-mesenchymal transition (EMT) promotes cell motility, which is important for the metastasis of malignant cells, and blocks CD95-mediated apoptotic signaling triggered by immune cells and chemotherapeutic regimens. CD95L, the cognate ligand of CD95, can be cleaved by metalloproteases and released as a soluble molecule (cl-CD95L). Unlike transmembrane CD95L, cl-CD95L does not induce apoptosis but triggers cell motility. Electron paramagnetic resonance was used to show that EMT and cl-CD95L treatment both led to augmentation of plasma membrane fluidity that was instrumental in inducing cell migration. Compaction of the plasma membrane is modulated, among other factors, by the ratio of certain lipids such as sphingolipids in the membrane. An integrative analysis of gene expression in NCI tumor cell lines revealed that expression of ceramide synthase-6 (CerS6) decreased during EMT. Furthermore, pharmacological and genetic approaches established that modulation of CerS6 expression/activity in cancer cells altered the level of C16-ceramide, which in turn influenced plasma membrane fluidity and cell motility. Therefore, this study identifies CerS6 as a novel EMT-regulated gene that has a pivotal role in the regulation of cell migration.

  5. Determination of plasma membrane fluidity with a fluorescent analogue of sphingomyelin by FRAP measurement using a standard confocal microscope.

    PubMed

    Klein, Christophe; Pillot, Thierry; Chambaz, Jean; Drouet, Beatrice

    2003-03-01

    Membrane perturbing effects have been described in neurodegenerative process like Alzheimer's disease and prion disorders. For example, non fibrillar amyloid-beta peptides (Abeta) implicated in Alzheimer's disease may exert its toxicity via membrane perturbation. Membrane organisation can be evaluated by its influence on lateral diffusion of lipids, which itself can be measured by FRAP (fluorescence recovery after photobleaching). We used this technique to study the effects of Abeta on membrane fluidity (Pillot et al., manuscript in preparation). We propose here a simple adaptation of FRAP using standard confocal laser scanning microscopy (CLSM). As a test experiment, we analysed the lateral diffusion of a fluorescent analogue of sphingomyelin and were able to demonstrate its increase upon cholesterol depletion induced by methyl-beta-cyclodextrin (cdx).

  6. Two-Step Membrane Binding of NDPK-B Induces Membrane Fluidity Decrease and Changes in Lipid Lateral Organization and Protein Cluster Formation.

    PubMed

    Francois-Moutal, Liberty; Ouberai, Myriam M; Maniti, Ofelia; Welland, Mark E; Strzelecka-Kiliszek, Agnieszka; Wos, Marcin; Pikula, Slawomir; Bandorowicz-Pikula, Joanna; Marcillat, Olivier; Granjon, Thierry

    2016-12-06

    Nucleoside diphosphate kinases (NDPKs) are crucial elements in a wide array of cellular physiological or pathophysiological processes such as apoptosis, proliferation, or metastasis formation. Among the NDPK isoenzymes, NDPK-B, a cytoplasmic protein, was reported to be associated with several biological membranes such as plasma or endoplasmic reticulum membranes. Using several membrane models (liposomes, lipid monolayers, and supported lipid bilayers) associated with biophysical approaches, we show that lipid membrane binding occurs in a two-step process: first, initiation by a strong electrostatic adsorption process and followed by shallow penetration of the protein within the membrane. The NDPK-B binding leads to a decrease in membrane fluidity and formation of protein patches. The ability of NDPK-B to form microdomains at the membrane level may be related to protein-protein interactions triggered by its association with anionic phospholipids. Such accumulation of NDPK-B would amplify its effects in functional platform formation and protein recruitment at the membrane.

  7. Using spin-label W-band EPR to study membrane fluidity profiles in samples of small volume

    NASA Astrophysics Data System (ADS)

    Mainali, Laxman; Hyde, James S.; Subczynski, Witold K.

    2013-01-01

    Conventional and saturation-recovery (SR) EPR at W-band (94 GHz) using phosphatidylcholine spin labels (labeled at the alkyl chain [n-PC] and headgroup [T-PC]) to obtain profiles of membrane fluidity has been demonstrated. Dimyristoylphosphatidylcholine (DMPC) membranes with and without 50 mol% cholesterol have been studied, and the results have been compared with similar studies at X-band (9.4 GHz) (L. Mainali, J.B. Feix, J.S. Hyde, W.K. Subczynski, J. Magn. Reson. 212 (2011) 418-425). Profiles of the spin-lattice relaxation rate (T1-1) obtained from SR EPR measurements for n-PCs and T-PC were used as a convenient quantitative measure of membrane fluidity. Additionally, spectral analysis using Freed's MOMD (microscopic-order macroscopic-disorder) model (E. Meirovitch, J.H. Freed J. Phys. Chem. 88 (1984) 4995-5004) provided rotational diffusion coefficients (R⊥ and R||) and order parameters (S0). Spectral analysis at X-band provided one rotational diffusion coefficient, R⊥. T1-1, R⊥, and R|| profiles reflect local membrane dynamics of the lipid alkyl chain, while the order parameter shows only the amplitude of the wobbling motion of the lipid alkyl chain. Using these dynamic parameters, namely T1-1, R⊥, and R||, one can discriminate the different effects of cholesterol at different depths, showing that cholesterol has a rigidifying effect on alkyl chains to the depth occupied by the rigid steroid ring structure and a fluidizing effect at deeper locations. The nondynamic parameter, S0, shows that cholesterol has an ordering effect on alkyl chains at all depths. Conventional and SR EPR measurements with T-PC indicate that cholesterol has a fluidizing effect on phospholipid headgroups. EPR at W-band provides more detailed information about the depth-dependent dynamic organization of the membrane compared with information obtained at X-band. EPR at W-band has the potential to be a powerful tool for studying membrane fluidity in samples of small volume, ˜30 n

  8. Using spin-label W-band EPR to study membrane fluidity profiles in samples of small volume

    PubMed Central

    Mainali, Laxman; Hyde, James S.; Subczynski, Witold K.

    2012-01-01

    Conventional and saturation-recovery (SR) EPR at W-band (94 GHz) using phosphatidylcholine spin labels (labeled at the alkyl chain [n-PC] and headgroup [T-PC]) to obtain profiles of membrane fluidity has been demonstrated. Dimyristoyl-phosphatidylcholine (DMPC) membranes with and without 50 mol% cholesterol have been studied, and the results have been compared with similar studies at X-band (9.4 GHz) (L. Mainali, J.B. Feix, J.S. Hyde, W.K. Subczynski J. Magn. Reson. 212:418-425 [2011]). Profiles of the spin-lattice relaxation rate (T1−1) obtained from SR EPR measurements for n-PCs and T-PC were used as a convenient quantitative measure of membrane fluidity. Additionally, spectral analysis using Freed’s MOMD (microscopic-order macroscopic-disorder) model (E. Meirovitch, J.H. Freed J. Phys. Chem. 88:4995-5004 [1984]) provided rotational diffusion coefficients (R⊥ and R∥) and order parameters (S0). Spectral analysis at X-band provided one rotational diffusion coefficient, R. T1−1, R⊥, and R∥ profiles reflect local membrane dynamics of the lipid alkyl chain, while the order parameter shows only the amplitude of the wobbling motion of the lipid alkyl chain. Using these dynamic parameters, namely T1−1, R⊥, and R∥, one can discriminate the different effects of cholesterol at different depths, showing that cholesterol has a rigidifying effect on alkyl chains to the depth occupied by the rigid steroid ring structure and a fluidizing effect at deeper locations. The nondynamic parameter, S0, shows that cholesterol has an ordering effect on alkyl chains at all depths. Conventional and SR EPR measurements with T-PC indicate that cholesterol has a fluidizing effect on phospholipids headgroups. EPR at W-band provides more detailed information about the depth-dependent dynamic organization of the membrane compared with information obtained at X-band. EPR at W-band has the potential to be a powerful tool for studying membrane fluidity in samples of small volume

  9. Factors Determining Staphylococcus aureus Susceptibility to Photoantimicrobial Chemotherapy: RsbU Activity, Staphyloxanthin Level, and Membrane Fluidity

    PubMed Central

    Kossakowska-Zwierucho, Monika; Kaźmierkiewicz, Rajmund; Bielawski, Krzysztof P.; Nakonieczna, Joanna

    2016-01-01

    Photoantimicrobial chemotherapy (PACT) constitutes a particular type of stress condition, in which bacterial cells induce a pleiotropic and as yet unexplored effect. In light of this, the key master regulators are of putative significance to the overall phototoxic outcome. In Staphylococcus aureus, the alternative sigma factor σB controls the expression of genes involved in the response to environmental stress. We show that aberration of any sigB operon genes in S. aureus USA300 isogenic mutants causes a pronounced sensitization (>5 log10 reduction in CFU drop) to PACT with selected photosensitizers, namely protoporphyrin diarginate, zinc phthalocyanine and rose bengal. This effect is partly due to aberration-coupled staphyloxanthin synthesis inhibition. We identified frequent mutations in RsbU, a σB activator, in PACT-vulnerable clinical isolates of S. aureus, resulting in σB activity impairment. Locations of significant changes in protein structure (IS256 insertion, early STOP codon occurrence, substitutions A230T and A276D) were shown in a theoretical model of S. aureus RsbU. As a phenotypic hallmark of PACT-vulnerable S. aureus strains, we observed an increased fluidity of bacterial cell membrane, which is a result of staphyloxanthin content and other yet unidentified factors. Our research indicates σB as a promising target of adjunctive antimicrobial therapy and suggests that enhanced cell membrane fluidity may be an adjuvant strategy in PACT. PMID:27486456

  10. Continuous flow atomic force microscopy imaging reveals fluidity and time-dependent interactions of antimicrobial dendrimer with model lipid membranes.

    PubMed

    Lind, Tania Kjellerup; Zielińska, Paulina; Wacklin, Hanna Pauliina; Urbańczyk-Lipkowska, Zofia; Cárdenas, Marité

    2014-01-28

    In this paper, an amphiphilic peptide dendrimer with potential applications against multi-resistant bacteria such as Staphylococcus aureus was synthesized and studied on model cell membranes. The combination of quartz crystal microbalance and atomic force microscopy imaging during continuous flow allowed for in situ monitoring of the very initial interaction processes and membrane transformations on longer time scales. We used three different membrane compositions of low and high melting temperature phospholipids to vary the membrane properties from a single fluid phase to a pure gel phase, while crossing the phase coexistence boundaries at room temperature. The interaction mechanism of the dendrimer was found to be time-dependent and to vary remarkably with the fluidity and coexistence of liquid-solid phases in the membrane. Spherical micelle-like dendrimer-lipid aggregates were formed in the fluid-phase bilayer and led to partial solubilization of the membrane, while in gel-phase membranes, the dendrimers caused areas of local depressions followed by redeposition of flexible lipid patches. Domain coexistence led to a sequence of events initiated by the formation of a ribbon-like network and followed by membrane solubilization via spherical aggregates from the edges of bilayer patches. Our results show that the dendrimer molecules were able to destroy the membrane integrity through different mechanisms depending on the lipid phase and morphology and shed light on their antimicrobial activity. These findings could have an impact on the efficacy of the dendrimers since lipid membranes in certain bacteria have transition temperatures very close to the host body temperature.

  11. Changes in membrane fluidity and fatty acid composition of Pseudomonas putida CN-T19 in response to toluene.

    PubMed

    Kim, In Seon; Shim, Jae Han; Suh, Yong Tack

    2002-09-01

    A bacterial isolate, Pseudomonas putida CN-T19, could grow in a two-phase medium with toluene up to 50% (v/v). Changes in fatty acid composition and membrane fluidity of the isolate were investigated to understand how this microorganism responds toluene. The changes in the ratios of unsaturated to saturated fatty acids were insignificant between cells grown with and without toluene. The changes in the ratio of cis- to trans-fatty acids of C16:1 and C18:1 was, however, significantly lower in cells grown with toluene than cells grown without toluene, giving approximately 1.3 and 9.7, respectively. Toluene had a fluidizing effect on the membrane of cells grown without toluene, resulting in decrease in membrane polarization ratio. Less fluidizing effect of toluene on the membrane of cells grown with toluene was observed, giving 11% of polarization percentage, which was significantly lower than 53% in cells grown without toluene. These results suggest that cis/trans isomeration of C16:1 and C18:1 makes cell membranes more rigid to respond toluene, and is an adaptive strategy allowing P. putida CN-T19 to grow in the presence of organic solvent.

  12. Metabolism of Fructooligosaccharides in Lactobacillus plantarum ST-III via Differential Gene Transcription and Alteration of Cell Membrane Fluidity

    PubMed Central

    Chen, Chen; Zhao, Guozhong

    2015-01-01

    Although fructooligosaccharides (FOS) can selectively stimulate the growth and activity of probiotics and beneficially modulate the balance of intestinal microbiota, knowledge of the molecular mechanism for FOS metabolism by probiotics is still limited. Here a combined transcriptomic and physiological approach was used to survey the global alterations that occurred during the logarithmic growth of Lactobacillus plantarum ST-III using FOS or glucose as the sole carbon source. A total of 363 genes were differentially transcribed; in particular, two gene clusters were induced by FOS. Gene inactivation revealed that both of the clusters participated in the metabolism of FOS, which were transported across the membrane by two phosphotransferase systems (PTSs) and were subsequently hydrolyzed by a β-fructofuranosidase (SacA) in the cytoplasm. Combining the measurements of the transcriptome- and membrane-related features, we discovered that the genes involved in the biosynthesis of fatty acids (FAs) were repressed in cells grown on FOS; as a result, the FA profiles were altered by shortening of the carbon chains, after which membrane fluidity increased in response to FOS transport and utilization. Furthermore, incremental production of acetate was observed in both the transcriptomic and the metabolic experiments. Our results provided new insights into gene transcription, the production of metabolites, and membrane alterations that could explain FOS metabolism in L. plantarum. PMID:26319882

  13. Hyperthermic potentiation of cisplatin by magnetic nanoparticle heaters is correlated with an increase in cell membrane fluidity.

    PubMed

    Alvarez-Berríos, Merlis P; Castillo, Amalchi; Mendéz, Janet; Soto, Orlando; Rinaldi, Carlos; Torres-Lugo, Madeline

    2013-01-01

    Magnetic fluid hyperthermia as a cancer treatment method is an attractive alternative to other forms of hyperthermia. It is based on the heat released by magnetic nanoparticles subjected to an alternating magnetic field. Recent studies have shown that magnetic fluid hyperthermia-treated cells respond significantly better to chemotherapeutic treatment compared with cells treated with hot water hyperthermia under the same temperature conditions. We hypothesized that this synergistic effect is due to an additional stress on the cellular membrane, independent of the thermal heat dose effect that is induced by nanoparticles exposed to an alternating magnetic field. This would result in an increase in Cis-diammine-dichloroplatinum (II) (cDDP, cisplatin) uptake via passive transport. To test this hypothesis, we exposed cDDP-treated cells to extracellular copper in order to hinder the human cell copper transporter (hCTR1)-mediated active transport of cDDP. This, in turn, can increase the passive transport of the drug through the cell membrane. Our results did not show statistically significant differences in surviving fractions for cells treated concomitantly with magnetic fluid hyperthermia and cDDP, in the presence or absence of copper. Nonetheless, significant copper-dependent variations in cell survival were observed for samples treated with combined cDDP and hot water hyperthermia. These results correlated with platinum uptake studies, which showed that cells treated with magnetic fluid hyperthermia had higher platinum uptake than cells treated with hot water hyperthermia. Changes in membrane fluidity were tested through fluorescence anisotropy measurements using trimethylamine-diphenylhexatriene. Additional uptake studies were conducted with acridine orange and measured by flow cytometry. These studies indicated that magnetic fluid hyperthermia significantly increases cell membrane fluidity relative to hot water hyperthermia and untreated cells, and hence this could

  14. Membrane Fluidity and Lipid Order in Ternary Giant Unilamellar Vesicles Using a New Bodipy-Cholesterol Derivative

    PubMed Central

    Ariola, Florly S.; Li, Zaiguo; Cornejo, Christine; Bittman, Robert; Heikal, Ahmed A.

    2009-01-01

    Cholesterol-rich, liquid-ordered (Lo) domains are believed to be biologically relevant, and yet detailed knowledge about them, especially in live cells under physiological conditions, is elusive. Although these domains have been observed in model membranes, understanding cholesterol-lipid interactions at the molecular level, under controlled lipid mixing, remains a challenge. Further, although there are a number of fluorescent lipid analogs that partition into liquid-disordered (Ld) domains, the number of such analogs with a high affinity for biologically relevant Lo domains is limited. Here, we use a new Bodipy-labeled cholesterol (Bdp-Chol) derivative to investigate membrane fluidity, lipid order, and partitioning in various lipid phases in giant unilamellar vesicles (GUVs) as a model system. GUVs were prepared from mixtures of various molar fractions of dioleoylphosphatidylcholine, cholesterol, and egg sphingomyelin. The Ld phase domains were also labeled with 1,1′-didodecyl-3,3,3′,3′-tetramethylindocarbocyanine (DiI-C12) for comparison. Two-photon fluorescence lifetime and anisotropy imaging of Bdp-Chol are sensitive to lipid phase domains in GUVs. The fluorescence lifetime of Bdp-Chol in liquid-disordered, single-phase GUVs is 5.50 ± 0.08 ns, compared with 4.1 ± 0.4 ns in the presence of DiI-C12. The observed reduction of fluorescence lifetime is attributed to Förster resonance energy transfer between Bdp-Chol (a donor) and DiI-C12 (an acceptor) with an estimated efficiency of 0.25 and donor-acceptor distance of 2.6 ± 0.2 nm. These results also indicate preferential partitioning (Kp = 1.88) of Bdp-Chol into the Lo phase. One-photon, time-resolved fluorescence anisotropy of Bdp-Chol decays as a triexponential in the lipid bilayer with an average rotational diffusion coefficient, lipid order parameter, and membrane fluidity that are sensitive to phase domains. The translational diffusion coefficient of Bdp-Chol, as measured using fluorescence

  15. A calcium channel blocker, benidipine, improves cell membrane fluidity in human subjects via a nitric oxide-dependent mechanism. An electron paramagnetic resonance investigation.

    PubMed

    Tsuda, Kazushi; Nishio, Ichiro

    2004-12-01

    Recent studies have revealed that benidipine, a long-acting dihydropyridine-type of calcium (Ca) channel blocker, may exert its protective effect against vascular disorders by increasing nitric oxide (NO) production. The purpose of the present study was to investigate the effects of benidipine and NO on the membrane function in human subjects. We measured the membrane fluidity of erythrocytes by using an electron paramagnetic resonance (EPR) and spin-labeling method. Benidipine decreased the order parameter (S) for 5-nitroxide stearate (5-NS) and the peak height ratio (h(o)/h(-1)) for 16-NS obtained from EPR spectra of erythrocyte membranes in a dose-dependent manner in normotensive volunteers. The finding indicated that benidipine increased the membrane fluidity and improved the microviscosity of erythrocytes. The effect of benidipine was significantly potentiated by the NO donor, S-nitroso-n-acetylpenicillamine, and by the cyclic guanosine 3', 5'-monophosphate (cGMP) analog, 8-bromo-cGMP. In contrast, the change evoked by benidipine was counteracted by the NO synthase inhibitors, N(G)-nitro-L-arginine-methyl-ester and asymmetric dimethyl-L-arginine. These results demonstrated that benidipine increased the membrane fluidity of erythrocytes, at least in part, via the NO- and cGMP-dependent mechanism. Furthermore, the data strongly suggest that benidipine might have a beneficial effect on the rheologic behavior of erythrocytes and the improvement of the microcirculation in humans.

  16. Effects of terpenes on fluidity and lipid extraction in phospholipid membranes.

    PubMed

    Mendanha, Sebastião Antonio; Alonso, Antonio

    2015-03-01

    Electron paramagnetic resonance (EPR) spectroscopy was used in a detailed study of the interactions of several terpenes with DPPC membranes. EPR spectra of a spin-label lipid allowed the identification of two well-resolved spectral components at temperatures below and above the main phase transition of the lipid bilayer. Terpenes caused only slight mobility increases in each of these spectral components; however, they substantially increased the population of the more mobile component. In addition, the terpenes reduced the temperature of the main phase transition by more than 8 °C and caused the extraction of the spin-labeled lipid. Nerolidol, which had the highest octanol-water partition coefficient, generated the highest amount of spin label extraction. Acting as spacers, terpenes should cause major reorganization in cell membranes, leading to an increase in the overall molecular dynamics of the membrane. At higher concentrations, terpenes may cause lipid extraction and thus leakage of the cytoplasmic content.

  17. A role for protein kinase C in the regulation of membrane fluidity and Ca²(+) flux at the endoplasmic reticulum and plasma membranes of HEK293 and Jurkat cells.

    PubMed

    Chen, Lihong; Meng, Qingli; Jing, Xian; Xu, Pingxiang; Luo, Dali

    2011-02-01

    Protein kinase C (PKC) plays a prominent role in the regulation of a variety of cellular functions, including Ca²(+) signalling. In HEK293 and Jurkat cells, the Ca²(+) release and Ca²(+) uptake stimulated by several different activators were attenuated by activation of PKC with phorbol myristate acetate (PMA) or 1-oleoyl-2-acetyl-sn-glycerol (OAG) and potentiated by PKC inhibition with Gö6983 or knockdown of PKCα or PKCβ using shRNA. Immunostaining and Western blotting analyses revealed that PKCα and PKCβII accumulated at the plasma membrane (PM) and that these isoforms, along with PKCβI, also translocated to the endoplasmic reticulum (ER) upon activation with PMA. Measurements of membrane fluidity showed that, like the cell membrane stabilizers bovine serum albumin (BSA) and ursodeoxycholate (UDCA), PMA and OAG significantly reduced the fluidity of both the PM and ER membranes; these effects were blocked in PKC-knockdown cells. Interestingly, both BSA and UDCA inhibited the Ca²(+) responses to agonists to the same extent as PMA, whereas Tween 20, which increases membrane fluidity, raised the internal Ca²(+) concentration. Thus, activation of PKC induces both translocation of PKC to the PM and ER membranes and downregulation of membrane fluidity, thereby negatively modulating Ca²(+) flux.

  18. Chemopreventive effects of nonsteroidal anti-inflammatory drugs in the membrane lipid composition and fluidity parameters of the 1,2-dimethylhydrazine-induced colon carcinogenesis in rats.

    PubMed

    Kanwar, Shailender Singh; Vaiphei, Kim; Nehru, Bimla; Sanyal, Sankar N

    2007-01-01

    Nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin, celecoxib, and etoricoxib are reported to act as chemopreventive agents in experimental colon cancer induced by 1,2-dimethylhydrazine (DMH) as they are known cyclooxygenase (COX) enzyme inhibitors. To determine whether NSAIDs can also effectively modulate the membrane lipid compositions and the fluidity parameters of colonic brush border membrane, rats were injected subcutaneously (s.c.) with DMH 30 mg/kg body weight per week for 6 weeks. The animals were simultaneously treated with NSAIDs orally at the dose of aspirin, 60 mg/kg body weight; celecoxib, 6 mg/kg body weight; and etoricoxib, 0.6 mg/kg body weight. The animals were sacrificed after 6 weeks of treatments. Brush border membrane was isolated from proximal and distal portions of the colon. Membrane lipids were extracted and analyzed while the fluidity parameters were assessed by steady-state fluorescence polarization technique using the membrane extrinsic fluorophore 1,6-diphenyl-1,3,5-hexatriene (DPH). The translational diffusion was measured by using the excimer formation of pyrene incorporated in the membrane. Colonic mucosal changes in DMH alone and DMH+NSAID treated animals were assessed histologically. The results demonstrate that (a) there is a distinct occurrence of premalignant alterations in DMH-induced colon in the form of multiple plaque lesions (MPLs), which were greatly reduced by the NSAIDs used, (b) the membrane lipid changes in DMH-induced colon were completely restored back, (c) the alterations in membrane fluorescence polarization and the fluidity parameters are partially recovered, particularly with etoricoxib, and (d) the pyrene excimer formation process was completely restored. It may be concluded that the NSAIDs, particularly the coxib group of the drugs (COX-2 selective), are effective in chemoprevention in the DMH-induced colon carcinogenesis and membrane alterations.

  19. Thermal Regulation of Membrane Lipid Fluidity by a Two-Component System in "Bacillus Subtilis"

    ERIC Educational Resources Information Center

    Bredeston, L. M.; Marciano, D.; Albanesi, D.; De Mendoza, D.; Delfino, J. M.

    2011-01-01

    This article describes a simple and robust laboratory exercise on the regulation of membrane unsaturated fatty acid composition in bacteria by a decrease in growth temperature. We take advantage of the well characterized Des pathway of "Bacillus subtilis", composed of a [delta]5-desaturase (encoded by the "des" gene) and the canonical…

  20. Effects of selenium on peripheral blood mononuclear cell membrane fluidity, interleukin-2 production and interleukin-2 receptor expression in patients with chronic hepatitis

    PubMed Central

    He, Shui-Xiang; Wu, Bing; Chang, Xin-Ming; Li, Hong-Xia; Qiao, Wen

    2004-01-01

    AIM: To study the effect of selenium on peripheral blood mononuclear cell (PBMC) membrane fluidity and immune function in patients with chronic hepatitis. METHODS: PBMCs were pretreated with selenium (1.156 × 10-7 mol/L) for 6 h in vitro or extracted directly from patients after administration of selenium-yeast continuously for 8-12 wk (200 μg/d), and then exposed to Con-A for 48 h. The membrane fluidity, interleukin-2 (IL-2) production and interleukin-2 receptor (IL-2R) expression in PBMCs and malondialdehyde (MDA) concentration in medium and lipid peroxide (LPO) in plasma were determined. RESULTS: The PBMC membrane fluidity, IL-2 production and IL-2R expression in patients with chronic hepatitis were significantly lower than those in healthy blood donators (particle adhesive degree R, 0.17 ± 0.01 vs 0.14 ± 0.01, P < 0.01; IL-2, 40.26 ± 9.55 vs 72.96 ± 11.36, P < 0.01; IL-2R, 31.05 ± 5.09 vs 60.58 ± 10.56, P < 0.01), and the MDA concentration in medium in patients with chronic hepatitis was significantly higher than that in healthy blood donators (1.44 ± 0.08 vs 0.93 ± 0.08, P < 0.01). Both in vitro and in vivo administration of selenium could reverse the above parameters. CONCLUSION: Supplement of selenium can suppress lipid peroxidation, and improve PBMC membrane fluidity and immune function in patients with chronic hepatitis. PMID:15526380

  1. The protective effect of a 17°C holding time on boar sperm plasma membrane fluidity after exposure to 5°C.

    PubMed

    Casas, I; Althouse, G C

    2013-02-01

    The holding time (HT) is the period during which an ejaculate, either in a raw or diluted state, is held at 17°C before further processing for cold-storage. In boars, the HT positively influences select sperm quality parameters of semen cooled from 15 to 5°C, a range in temperature during which plasma membrane remodeling occurs. Objective insight into the effect of HT on plasma membrane organization remains unknown. Therefore, the present work sought to elucidate if HT contributes to minimizing alterations in boar sperm plasma membrane fluidity at the initial step of the cooling process in a cryopreservation practice (holding at 5°C) and in relation with select sperm quality parameters. Nineteen ejaculates from five boars were collected and processed according to different treatments: T1) Fresh diluted semen, 0h at 17°C; T2) Fresh diluted semen, 24h at 17°C (HT); T3) Sperm from T1 in a lactose-egg yolk (LEY) extender, 3h at 5°C; T4) Sperm from T2 in LEY, 3h at 5°C; T5) Sperm from T1 in LEY, 24h at 5°C; T6) Sperm from T2 in LEY, 24h at 5°C. Sperm motility was assessed using CASA, and sperm plasma membrane integrity and fluidity were evaluated by flow cytometry with dual labeling (M540/YO-PRO®-1). Results demonstrated that the lack of exposure to a HT (T5) results in reduced sample motility compared to those having a HT (T6), with sperm exposed to HT exhibiting less plasma membrane fluidity. Collectively, these results provide empirical evidence that incorporation of a HT in semen processing protects boar sperm against cold injury through maintenance of lipid architecture of the plasma membrane.

  2. HACD1, a regulator of membrane composition and fluidity, promotes myoblast fusion and skeletal muscle growth

    PubMed Central

    Blondelle, Jordan; Ohno, Yusuke; Gache, Vincent; Guyot, Stéphane; Storck, Sébastien; Blanchard-Gutton, Nicolas; Barthélémy, Inès; Walmsley, Gemma; Rahier, Anaëlle; Gadin, Stéphanie; Maurer, Marie; Guillaud, Laurent; Prola, Alexandre; Ferry, Arnaud; Aubin-Houzelstein, Geneviève; Demarquoy, Jean; Relaix, Frédéric; Piercy, Richard J.; Blot, Stéphane; Kihara, Akio; Tiret, Laurent; Pilot-Storck, Fanny

    2015-01-01

    The reduced diameter of skeletal myofibres is a hallmark of several congenital myopathies, yet the underlying cellular and molecular mechanisms remain elusive. In this study, we investigate the role of HACD1/PTPLA, which is involved in the elongation of the very long chain fatty acids, in muscle fibre formation. In humans and dogs, HACD1 deficiency leads to a congenital myopathy with fibre size disproportion associated with a generalized muscle weakness. Through analysis of HACD1-deficient Labradors, Hacd1-knockout mice, and Hacd1-deficient myoblasts, we provide evidence that HACD1 promotes myoblast fusion during muscle development and regeneration. We further demonstrate that in normal differentiating myoblasts, expression of the catalytically active HACD1 isoform, which is encoded by a muscle-enriched splice variant, yields decreased lysophosphatidylcholine content, a potent inhibitor of myoblast fusion, and increased concentrations of ≥C18 and monounsaturated fatty acids of phospholipids. These lipid modifications correlate with a reduction in plasma membrane rigidity. In conclusion, we propose that fusion impairment constitutes a novel, non-exclusive pathological mechanism operating in congenital myopathies and reveal that HACD1 is a key regulator of a lipid-dependent muscle fibre growth mechanism. PMID:26160855

  3. Dietary menhaden and corn oils and the red blood cell membrane lipid composition and fluidity in hyper- and normocholesterolemic miniature swine.

    PubMed

    Berlin, E; Bhathena, S J; McClure, D; Peters, R C

    1998-09-01

    Fatty acids in the diet are readily incorporated into lipids in various tissues. However, it is not clear whether all tissues have the same level of incorporation. Second, (n-6) unsaturated fatty acids increase the fluidity of membranes, but this has not been shown for (n-3) fatty acids. In this study, we measured the incorporation of (n-6) and (n-3) fatty acids into erythrocyte membrane lipids and studied their effects on the fluidity of erythrocyte membranes. One group of female miniature swine was made hypercholesterolemic by feeding the swine cholesterol and lard for 2 mo; the other group served as controls and was fed a stock diet. Both groups were then fed either corn oil or menhaden oil or a mixture of the two for 23 additional weeks. Blood was collected at 0, 2, 4, 12 and 23 wk after initialization of the experimental diets, and fatty acid composition of phospholipids was assessed. Membrane phospholipids of pigs fed menhaden oil had elevated (n-3) fatty acids (20:5 and 22:6), and lower 18:2 than those fed corn oil. There was no difference in 20:4 content. The fatty acid changes occurred as early as 2 wk after consumption of the corn oil or menhaden oil in pigs previously fed a stock diet, but it took longer in pigs previously fed lard + cholesterol, indicating residual effects of pretreatment. Menhaden oil increased anisotropy (indicating decreased fluidity) more than corn oil for the nonpolar probe diphenylhexatriene (DPH) at earlier time points, but not at 23 wk. Erythrocyte membrane fluidity was significantly related to membrane polyunsaturate content, with (n-6) fatty acids having a greater influence than (n-3) fatty acids. A comparison of the present red blood cell fatty acid compositions with brain synaptosome fatty acid compositions for the same animals showed poor correlations for some of the fatty acids. There was no significant direct relationship between docosahexaenoate (DHA) concentrations in erythrocyte membranes with DHA concentrations in

  4. Compensatory role of the cis-trans-isomerase and cardiolipin synthase in the membrane fluidity of Pseudomonas putida DOT-T1E.

    PubMed

    Bernal, Patricia; Segura, Ana; Ramos, Juan-Luis

    2007-07-01

    In Gram-negative bacteria, cell membrane fluidity is influenced by phospholipid head group composition and linked fatty acids. Exposure of Pseudomonas putida to stressing agents results in short- and long-term modifications in membrane lipids. The main adaptive change observed in response to organic solvents in the short term is the cis- to trans-isomerization of unsaturated fatty acids in a reaction mediated by cis/trans-isomerase (CTI); whereas in the long term an increase in cardiolipin content takes place. Despite the interest of these genes in the context of stress responses, the transcriptional regulation of the cti and cls genes has not been studied before. The cti and cls (cardiolipin synthase) genes in the solvent-tolerant P. putida DOT-T1E strain form monocistronic units and are expressed from sigma-70 promoters. Expression from the cls promoter is sixfold higher in the stationary phase than in the log phase, and expression of the cls gene is not influenced by solvents. The cti gene is expressed at fairly constant levels in the log and stationary phase, but its level of expression is moderately upregulated in response to toluene. We used fluorescence polarization assays to show that mutants deficient in the cti gene exhibit less rigid membranes than the wild-type strain, whereas mutants with a knockout in the cls gene exhibit increased membrane rigidity. A double cti/cls mutant has similar membrane rigidity as the wild-type strain, which points towards a compensatory effect of the mutations with regard to membrane fluidity. However, the cls and cls/cti mutants were more sensitive to solvents than the wild-type and the cti mutant because of the impaired functioning of efflux drug transporters.

  5. Effects of the Cellcultured Acanthopanax senticosus Extract on Antioxidative Defense System and Membrane Fluidity in the Liver of Type 2 Diabetes Mouse

    PubMed Central

    Hong, Jung-Hee; Cha, Youn-Soo; Rhee, Soon-Jae

    2009-01-01

    This study examined the effect of cellcultured Acanthopanax senticosus (A. senticosus) extract on the antioxidative defense system, oxidative stress and cell membrane fluidity in the liver of type 2 diabetes in the C57BL/6J mouse as an animal which is genetically prone to develop insulin resistance and obesity/diabetes. C57BL/6J mice were randomly divided, control diet (N-C), high fat diet (DM-C), control diet plus A. senticosus extract (N-CASM), and high fat diet plus A. senticosus extract (DM-CASM). The mice were orally administered an A. senticosus extract (0.5 g/kg body weight) in the N-CASM and DM-CASM groups once a day for 12 weeks, and distilled water in the N-C and DM-C groups. Cellcultured A. senticosus extract was found to be excellent for strengthening the antioxidative defense system, reducing the generation of reactive oxygen species (ROS) and damaging oxidative substances, and maintaing membrane fluidity (MF) in the liver of type 2 diabetes mouse. PMID:19590714

  6. Interaction of curcumin with 1,2-dioctadecanoyl-sn-glycero-3-phosphocholine liposomes: Intercalation of rhamnolipids enhances membrane fluidity, permeability and stability of drug molecule.

    PubMed

    Moussa, Zeinab; Chebl, Mazhar; Patra, Digambara

    2017-01-01

    Stability of curcumin in neutral and alkaline buffer conditions has been a serious concern for its medicinal applications. We demonstrate that the stability of curucmin can be improved in 1,2-Dioctadecanoyl-sn-glycero-3-phosphocholine (DSPC) liposomes. Curcumin strongly partition into liquid crystalline phase compared to solid gel phase of DSPC liposomes. Variation of fluorescence intensity of curcumin associated with liposomes with temperature successfully determines phase transition temperature of DSPC liposomes. However, at higher molar ratio curcumin can influence phase transition temperature by intercalating into deep hydrophobic layer of liposomes and facilitating fusion of two membrane phases. Rhamnolipids (RLs) are recently being applied for various biomedical applications. Here, we have explored new insight on intercalation of rhamnolipids with DSPC liposomes. Intercalation of rhamnolipids exceptionally increases partition of curcumin into solid gel phase of DSPC liposomes, whereas this increase is moderate in liquid crystalline phase. Fluorescence quenching study establishes that permeability and fluidity of the DSPC liposomes are enhanced in the presence of RLs. Membrane permeability and fluidity can be improved further by increasing the percentage of RLs in DSPC liposomes. The phase transition temperature of DSPC liposomes decreases with increase in percentage of RLs in DSPC liposomes by encouraging fusion between solid gel and liquid crystalline phases. Intercalation of RLs is found to further boost stability of drug, curcumin, in DSPC liposomes. Thus, mixing RLs with DSPC liposomes could potentially serve as a good candidate for drug delivery application.

  7. How Lipid Membranes Affect Pore Forming Toxin Activity.

    PubMed

    Rojko, Nejc; Anderluh, Gregor

    2015-12-15

    Pore forming toxins (PFTs) evolved to permeate the plasma membrane of target cells. This is achieved in a multistep mechanism that usually involves binding of soluble protein monomer to the lipid membrane, oligomerization at the plane of the membrane, and insertion of part of the polypeptide chain across the lipid membrane to form a conductive channel. Introduced pores allow uncontrolled transport of solutes across the membrane, inflicting damage to the target cell. PFTs are usually studied from the perspective of structure-function relationships, often neglecting the important role of the bulk membrane properties on the PFT mechanism of action. In this Account, we discuss how membrane lateral heterogeneity, thickness, and fluidity influence the pore forming process of PFTs. In general, lipid molecules are more accessible for binding in fluid membranes due to steric reasons. When PFT specifically binds ordered domains, it usually recognizes a specific lipid distribution pattern, like sphingomyelin (SM) clusters or SM/cholesterol complexes, and not individual lipid species. Lipid domains were also suggested to act as an additional concentration platform facilitating PFT oligomerization, but this is yet to be shown. The last stage in PFT action is the insertion of the transmembrane segment across the membranes to build the transmembrane pore walls. Conformational changes are a spontaneous process, and sufficient free energy has to be available for efficient membrane penetration. Therefore, fluid bilayers are permeabilized more readily in comparison to highly ordered and thicker liquid ordered lipid phase (Lo). Energetically more costly insertion into the Lo phase can be driven by the hydrophobic mismatch between the thinner liquid disordered phase (Ld) and large protein complexes, which are unable to tilt like single transmembrane segments. In the case of proteolipid pores, membrane properties can directly modulate pore size, stability, and even selectivity. Finally

  8. Mobility of ribosomes bound to microsomal membranes. A freeze-etch and thin-section electron microscope study of the structure and fluidity of the rough endoplasmic reticulum

    PubMed Central

    1977-01-01

    The lateral mobility of ribosomes bound to rough endoplasmic reticulum (RER) membranes was demonstrated under experimental conditions. High- salt-washed rough microsomes were treated with pancreatic ribonuclease (RNase) to cleave the mRNA of bound polyribosomes and allow the movement of individual bound ribosomesmfreeze-etch and thin-section electron microscopy demonstrated that, when rough microsomes were treated with RNase at 4 degrees C and then maintained at this temperature until fixation, the bound ribosomes retained their homogeneous distribution on the microsomal surface. However, when RNase- treated rough microsomes were brought to 24 degrees C, a temperature above the thermotropic phase transition of the microsomal phospholipids, bound ribosomes were no longer distributed homogeneously but, instead, formed large, tightly packed aggregates on the microsomal surface. Bound polyribosomes could also be aggregated by treating rough microsomes with antibodies raised against large ribosomal subunit proteins. In these experiments, extensive cross-linking of ribosomes from adjacent microsomes also occurred, and large ribosome-free membrane areas were produced. Sedimentation analysis in sucrose density gradients demonstrated that the RNase treatment did not release bound ribosomes from the membranes; however, the aggregated ribosomes remain capable of peptide bond synthesis and were released by puromycin. It is proposed that the formation of ribosomal aggregates on the microsomal surface results from the lateral displacement of ribosomes along with their attached binding sites, nascent polypeptide chains, and other associated membrane proteins; The inhibition of ribosome mobility after maintaining rough microsomes at 4 degrees C after RNase, or antibody, treatment suggests that the ribosome binding sites are integral membrane proteins and that their mobility is controlled by the fluidity of the RER membrane. Examination of the hydrophobic interior of microsomal

  9. Type-1 Cannabinoid Receptors Reduce Membrane Fluidity of Capacitated Boar Sperm by Impairing Their Activation by Bicarbonate

    PubMed Central

    Barboni, Barbara; Bernabò, Nicola; Palestini, Paola; Botto, Laura; Pistilli, Maria Gabriella; Charini, Marco; Tettamanti, Enzo; Battista, Natalia

    2011-01-01

    Background Mammalian spermatozoa acquire their full fertilizing ability (so called capacitation) within the female genital tract, where they are progressively exposed to inverse gradients of inhibiting and stimulating molecules. Methodology/Principal Findings In the present research, the effect on this process of anandamide, an endocannabinoid that can either activate or inhibit cannabinoid receptors depending on its concentration, and bicarbonate, an oviductal activatory molecule, was assessed, in order to study the role exerted by the type 1 cannabinoid receptor (CB1R) in the process of lipid membrane remodeling crucial to complete capacitation. To this aim, boar sperm were incubated in vitro under capacitating conditions (stimulated by bicarbonate) in the presence or in the absence of methanandamide (Met-AEA), a non-hydrolysable analogue of anandamide. The CB1R involvement was studied by using the specific inhibitor (SR141716) or mimicking its activation by adding a permeable cAMP analogue (8Br-cAMP). By an immunocytochemistry approach it was shown that the Met-AEA inhibits the bicarbonate-dependent translocation of CB1R from the post-equatorial to equatorial region of sperm head. In addition it was found that Met-AEA is able to prevent the bicarbonate-induced increase in membrane disorder and the cholesterol extraction, both preliminary to capacitation, acting through a CB1R-cAMP mediated pathway, as indicated by MC540 and filipin staining, EPR spectroscopy and biochemical analysis on whole membranes (CB1R activity) and on membrane enriched fraction (C/P content and anisotropy). Conclusions/Significance Altogether, these data demonstrate that the endocannabinoid system strongly inhibits the process of sperm capacitation, acting as membrane stabilizing agent, thus increasing the basic knowledge on capacitation-related signaling and potentially opening new perspectives in diagnostics and therapeutics of male infertility. PMID:21829686

  10. Restoring effect of selenium on the molecular content, structure and fluidity of diabetic rat kidney brush border cell membrane.

    PubMed

    Gurbanov, Rafig; Bilgin, Mehmet; Severcan, Feride

    2016-04-01

    Diabetic kidney disease (DKD) is a dominant factor standing for kidney impairments during diabetes. In this study, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy was used to disclose the diabetes-induced structural changes in the kidney and evaluate the effects of selenium on diabetes. The increase in the area of the olefinic band indicated increased amount of lipid peroxidation end products in diabetic kidney brush border cell membrane. Moreover, saturated lipid content of this cell membrane considerably diminished. DKD was found to disrupt lipid order and cause a decrease in membrane dynamics. However, the administration of selenium at low and medium doses was shown to improve these conditions by changing the lipid contents toward control values, restoring the ordered structure of the lipids and membrane dynamics. Curve-fitting and artificial neural network (ANN) analyses of secondary structures of proteins demonstrated a relative increase in α-helix and reduction in the β-sheet during diabetes in comparison to the control group, which were ameliorated following selenium treatment at low and medium doses. These findings were further confirmed by applying hierarchical cluster analysis (HCA) and principal component analysis (PCA). A clear separation of the experimental groups was obtained with high heterogeneity in the lipid and protein regions. These chemometric analyses showed that the low and medium doses of selenium-treated diabetic groups are successfully segregated from the diabetic group and clustered closer to the control. The study suggests that medium and, more predominantly, low-dose selenium treatment can be efficient in eliminating diabetes-induced structural alterations.

  11. A Novel Role for an ECF Sigma Factor in Fatty Acid Biosynthesis and Membrane Fluidity in Pseudomonas aeruginosa

    PubMed Central

    Boechat, Ana Laura; Kaihami, Gilberto Hideo; Politi, Mario José; Lépine, François; Baldini, Regina L.

    2013-01-01

    Extracytoplasmic function (ECF) sigma factors are members of cell-surface signaling systems, abundant in the opportunistic pathogen Pseudomonas aeruginosa. Twenty genes coding for ECF sigma factors are present in P. aeruginosa sequenced genomes, most of them being part of TonB systems related to iron uptake. In this work, poorly characterized sigma factors were overexpressed in strain PA14, in an attempt to understand their role in the bacterium´s physiology. Cultures overexpressing SigX displayed a biphasic growth curve, reaching stationary phase earlier than the control strain, followed by subsequent growth resumption. During the first stationary phase, most cells swell and die, but the remaining cells return to the wild type morphology and proceed to a second exponential growth. This is not due to compensatory mutations, since cells recovered from late time points and diluted into fresh medium repeated this behavior. Swollen cells have a more fluid membrane and contain higher amounts of shorter chain fatty acids. A proteomic analysis was performed to identify differentially expressed proteins due to overexpression of sigX, revealing the induction of several fatty acid synthesis (FAS) enzymes. Using qRT-PCR, we showed that at least one isoform from each of the FAS pathway enzymes were upregulated at the mRNA level in the SigX overexpressing strain thus pointing to a role for this ECF sigma factor in the FAS regulation in P. aeruginosa. PMID:24386415

  12. Pseudomonas putida NCTC 10936 balances membrane fluidity in response to physical and chemical stress by changing the saturation degree and the trans/cis ratio of fatty acids.

    PubMed

    Loffhagen, Norbert; Härtig, Claus; Babel, Wolfgang

    2004-02-01

    This study explored the capability of Pseudomonas putida NCTC 10936 to maintain homeoviscosity after changing the growth temperature, incubating resting cells at different temperatures or at a constant temperature in the presence of 4-chlorophenol (4-CP). After raising the growth temperature from 20 to either 30 or 35 degrees C, the degree of saturation of the organism's fatty acids increased and the ratio of trans to cis unsaturated fatty acids decreased somewhat. In contrast, after the incubation temperature of resting cells was raised (grown at 30 degrees C) from 20 to 30 or 35 degrees C the degree of saturation of the fatty acids remained nearly constant, while the ratio of trans to cis unsaturated fatty acids increased. Incubating resting cells (grown at 30 degrees C) at 20 degrees C in the presence of 4-CP again caused no major changes in the degree of saturation, but cis to trans conversion of unsaturated fatty acids was induced, with a corresponding increase in the trans/cis ratios. Increases in both the saturation degree of the fatty acids and the trans/cis ratio of the unsaturated fatty acids correlated with increases in the fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene intercalated in the bilayers of liposomes prepared from the cells of P. putida NCTC 10936. Electron transport phosphorylation (ETP) could be stabilized by adaptive adjustments in the fluidity of the cytoplasmic membrane mediated by changes in fatty acid composition such as those observed. Whether changes in the degree of saturation or in the trans/cis ratio are more effective can be decided by studying P. putida NCTC 10936.

  13. Effect of a Vietnamese Cinnamomum cassia essential oil and its major component trans-cinnamaldehyde on the cell viability, membrane integrity, membrane fluidity, and proton motive force of Listeria innocua.

    PubMed

    Trinh, Nga-Thi-Thanh; Dumas, Emilie; Thanh, Mai Le; Degraeve, Pascal; Ben Amara, Chedia; Gharsallaoui, Adem; Oulahal, Nadia

    2015-04-01

    The antibacterial mechanism of a Cinnamomum cassia essential oil from Vietnam and of its main component (trans-cinnamaldehyde, 90% (m/m) of C. cassia essential oil) against a Listeria innocua strain was investigated to estimate their potential for food preservation. In the presence of C. cassia essential oil or trans-cinnamaldehyde at their minimal bactericidal concentration (2700 μg·mL(-1)), L. innocua cells fluoresced green after staining with Syto9® and propidium iodide, as observed by epifluorescence microscopy, suggesting that the perturbation of membrane did not cause large pore formation and cell lysis but may have introduced the presence of viable but nonculturable bacteria. Moreover, the fluidity, potential, and intracellular pH of the cytoplasmic membrane were perturbed in the presence of the essential oil or trans-cinnamaldehyde. However, these membrane perturbations were less severe in the presence of trans-cinnamaldehyde than in the presence of multicomponent C. cassia essential oil. This indicates that in addition to trans-cinnamaldehyde, other minor C. cassia essential oil components play a major role in its antibacterial activity against L. innocua cells.

  14. Short branched-chain C6 carboxylic acids result in increased growth, novel 'unnatural' fatty acids and increased membrane fluidity in a Listeria monocytogenes branched-chain fatty acid-deficient mutant.

    PubMed

    Sen, Suranjana; Sirobhushanam, Sirisha; Hantak, Michael P; Lawrence, Peter; Brenna, J Thomas; Gatto, Craig; Wilkinson, Brian J

    2015-10-01

    Listeria monocytogenes is a psychrotolerant food borne pathogen, responsible for the high fatality disease listeriosis, and expensive food product recalls. Branched-chain fatty acids (BCFAs) of the membrane play a critical role in providing appropriate membrane fluidity and optimum membrane biophysics. The fatty acid composition of a BCFA-deficient mutant is characterized by high amounts of straight-chain fatty acids and even-numbered iso fatty acids, in contrast to the parent strain where odd-numbered anteiso fatty acids predominate. The presence of 2-methylbutyrate (C5) stimulated growth of the mutant at 37°C and restored growth at 10°C along with the content of odd-numbered anteiso fatty acids. The C6 branched-chain carboxylic acids 2-ethylbutyrate and 2-methylpentanoate also stimulated growth to a similar extent as 2-methylbutyrate. However, 3-methylpentanoate was ineffective in rescuing growth. 2-Ethylbutyrate and 2-methylpentanoate led to novel major fatty acids in the lipid profile of the membrane that were identified as 12-ethyltetradecanoic acid and 12-methylpentadecanoic acid respectively. Membrane anisotropy studies indicated that growth of strain MOR401 in the presence of these precursors increased its membrane fluidity to levels of the wild type. Cells supplemented with 2-methylpentanoate or 2-ethylbutyrate at 10°C shortened the chain length of novel fatty acids, thus showing homeoviscous adaptation. These experiments use the mutant as a tool to modulate the membrane fatty acid compositions through synthetic precursor supplementation, and show how existing enzymes in L. monocytogenes adapt to exhibit non-native activity yielding unique 'unnatural' fatty acid molecules, which nevertheless possess the correct biophysical properties for proper membrane function in the BCFA-deficient mutant.

  15. Assessment of fluidity of different invasomes by electron spin resonance and differential scanning calorimetry.

    PubMed

    Dragicevic-Curic, Nina; Friedrich, Manfred; Petersen, Silvia; Scheglmann, Dietrich; Douroumis, Dennis; Plass, Winfried; Fahr, Alfred

    2011-06-30

    The aim of this study was to investigate the influence of membrane-softening components (terpenes/terpene mixtures, ethanol) on fluidity of phospholipid membranes in invasomes, which contain besides phosphatidylcholine and water, also ethanol and terpenes. Also mTHPC was incorporated into invasomes in order to study its molecular interaction with phospholipids in vesicular membranes. Fluidity of bilayers was investigated by electron spin resonance (ESR) using spin labels 5- and 16-doxyl stearic acid and by differential scanning calorimetry (DSC). Addition of 1% of a single terpene/terpene mixture led to significant fluidity increase around the C16 atom of phospholipid acyl chains comprising the vesicles. However, it was not possible to differentiate between the influences of single terpenes or terpene mixtures. Incorporation of mTHPC into the bilayer of vesicles decreased fluidity near the C16 atom of acyl chains, indicating its localization in the inner hydrophobic zone of bilayers. These results are in agreement with DSC measurements, which showed that terpenes increased fluidity of bilayers, while mTHPC decreased fluidity. Thus, invasomes represent vesicles with very high membrane fluidity. However, no direct correlation between fluidity of invasomes and their penetration enhancing ability was found, indicating that besides fluidity also other phenomena might be responsible for improved skin delivery of mTHPC.

  16. Adaptation to low body temperature influences pulmonary surfactant composition thereby increasing fluidity while maintaining appropriately ordered membrane structure and surface activity.

    PubMed

    Suri, Lakshmi N M; McCaig, Lynda; Picardi, Maria V; Ospina, Olga L; Veldhuizen, Ruud A W; Staples, James F; Possmayer, Fred; Yao, Li-Juan; Perez-Gil, Jesus; Orgeig, Sandra

    2012-07-01

    The interfacial surface tension of the lung is regulated by phospholipid-rich pulmonary surfactant films. Small changes in temperature affect surfactant structure and function in vitro. We compared the compositional, thermodynamic and functional properties of surfactant from hibernating and summer-active 13-lined ground squirrels (Ictidomys tridecemlineatus) with porcine surfactant to understand structure-function relationships in surfactant membranes and films. Hibernating squirrels had more surfactant large aggregates with more fluid monounsaturated molecular species than summer-active animals. The latter had more unsaturated species than porcine surfactant. Cold-adapted surfactant membranes displayed gel-to-fluid transitions at lower phase transition temperatures with reduced enthalpy. Both hibernating and summer-active squirrel surfactants exhibited lower enthalpy than porcine surfactant. LAURDAN fluorescence and DPH anisotropy revealed that surfactant bilayers from both groups of squirrels possessed similar ordered phase characteristics at low temperatures. While ground squirrel surfactants functioned well during dynamic cycling at 3, 25, and 37 degrees C, porcine surfactant demonstrated poorer activity at 3 degrees C but was superior at 37 degrees C. Consequently the surfactant composition of ground squirrels confers a greater thermal flexibility relative to homeothermic mammals, while retaining tight lipid packing at low body temperatures. This may represent the most critical feature contributing to sustained stability of the respiratory interface at low lung volumes. Thus, while less effective than porcine surfactant at 37 degrees C, summer-active surfactant functions adequately at both 37 degrees C and 3 degrees C allowing these animals to enter hibernation. Here further compositional alterations occur which improve function at low temperatures by maintaining adequate stability at low lung volumes and when temperature increases during arousal from

  17. Piroxicam and c-phycocyanin prevent colon carcinogenesis by inhibition of membrane fluidity and canonical Wnt/β-catenin signaling while up-regulating ligand dependent transcription factor PPARγ.

    PubMed

    Saini, Manpreet Kaur; Sanyal, Sankar Nath

    2014-06-01

    The colon cancer tissues from DMH treated rats exhibited higher membrane potential, fluidity and changed lipid order as examined by Merocyanine 540 and 1,6-diphenyl-1,3,5-hexatriene, respectively. A transition from gel to liquid crystalline state was observed by Laurdan fluorescence and also reduced fluorescence quenching of NBD-PE as contributed in the decreased membrane lipid phase separation. With piroxicam, a traditional NSAID and c-phycocyanin, a biliprotein from Spirulina platensis, these effects were normalized. An augmented intracellular Ca(+2) had contributed to the drug mediated apoptosis which is supported by an elevated calpain-9 expression. Histopathologically, a large pool of secreted acid/neutral mucopolysaccrides as well as the presence of blood vessels and dysplastic crypts signifies invasive mucinous adenocarcinoma while both the drugs reduced these neoplastic alterations. Wnt/β-catenin pathway was also found to be up-regulated which served as a crucial indicator for cancer cell growth. A concomitant down regulation of PPARγ was noted in DMH treatment which is associated with tumor progression. The expression of PPARα and δ, the other two isoforms of PPAR family was also modulated. We conclude that piroxicam and c-phycocyanin exert their anti-neoplastic effects via regulating membrane properties, raising calpain-9 and PPARγ expression while suppressing Wnt/β-catenin signaling in experimental colon carcinogenesis.

  18. Relationship Between Liquid Fluidity of Iron Ore and Generated Liquid Content During Sintering

    NASA Astrophysics Data System (ADS)

    Peng, Jun; Zhang, Lei; Liu, Li-xia; An, Sheng-li

    2017-02-01

    The fluidity of sintering liquid phase reflects the effective bonding range of the binder phase in the sintering process of iron ores. In this study, the liquid composition and quantity during sintering was calculated using FactSage 7.0 thermodynamic calculation software. The results show that two liquid phases are formed during sintering. One phase is generated at about 1373 K (1100 °C) and the other is generated at about 1523 K (1250 °C). The liquid fluidity index and the low-temperature liquid phase are closely related. The higher-temperature liquid phase has little influence on the liquid fluidity index. The larger the amount of low-temperature liquid phase generated, the higher the liquid fluidity index is. The alkalinity of the low-temperature liquid phase has insignificant influence on the liquid fluidity index. The content of SiO2 in the iron ore is the main factor that affects the liquid fluidity index during sintering. The liquid fluidity index increases greatly with increasing SiO2 content. In contrast, Al2O3 content has little influence on the liquid fluidity index, with an increase in the Al2O3 content only slightly increasing the liquid fluidity index. An increase in the MgO content of the iron ore can reduce liquid generation, promote the spinel generation, and decrease the liquid fluidity index during sintering.

  19. Neutralizing antibodies decrease the envelope fluidity of HIV-1

    SciTech Connect

    Harada, Shinji Monde, Kazuaki; Tanaka, Yuetsu; Kimura, Tetsuya; Maeda, Yosuke; Yusa, Keisuke

    2008-01-05

    For successful penetration of HIV-1, the formation of a fusion pore may be required in order to accumulate critical numbers of fusion-activated gp41 with the help of fluidization of the plasma membrane and viral envelope. An increase in temperature to 40 {sup o}C after viral adsorption at 25 {sup o}C enhanced the infectivity by 1.4-fold. The enhanced infectivity was inhibited by an anti-CXCR4 peptide, T140, and anti-V3 monoclonal antibodies (0.5{beta} and 694/98-D) by post-attachment neutralization, but not by non-neutralizing antibodies (670-30D and 246-D) specific for the C5 of gp120 and cluster I of gp41, respectively. Anti-HLA-II and an anti-HTLV-I gp46 antibody, LAT27, neutralized the molecule-carrying HIV-1{sub C-2(MT-2)}. The anti-V3 antibodies suppressed the fluidity of the HIV-1{sub C-2} envelope, whereas the non-neutralizing antibodies did not. The anti-HLA-II antibody decreased the envelope fluidity of HIV-1{sub C-2(MT-2)}, but not that of HIV-1{sub C-2}. Therefore, fluidity suppression by these antibodies represents an important neutralization mechanism, in addition to inhibition of viral attachment.

  20. Does Membrane Thickness Affect the Transport of Selective Ions Mediated by Ionophores in Synthetic Membranes?

    PubMed

    Lomora, Mihai; Dinu, Ionel Adrian; Itel, Fabian; Rigo, Serena; Spulber, Mariana; Palivan, Cornelia G

    2015-08-31

    Biomimetic polymer nanocompartments (polymersomes) with preserved architecture and ion-selective membrane permeability represent cutting-edge mimics of cellular compartmentalization. Here it is studied whether the membrane thickness affects the functionality of ionophores in respect to the transport of Ca(2+) ions in synthetic membranes of polymersomes, which are up to 2.6 times thicker than lipid membranes (5 nm). Selective permeability toward calcium ions is achieved by proper insertion of ionomycin, and demonstrated by using specific fluorescence markers encapsulated in their inner cavities. Preservation of polymersome architecture is shown by a combination of light scattering, transmission electron microscopy, and fluorescence spectroscopy. By using a combination of stopped-flow and fluorescence spectroscopy, it is shown that ionomycin can function and transport calcium ions across polymer membranes with thicknesses in the range 10.7-13.4 nm (7.1-8.9 times larger than the size of the ionophore). Thicker membranes induce a decrease in transport, but do not block it due to the intrinsic flexibility of these synthetic membranes. The design of ion selective biomimetic nanocompartments represents a new path toward the development of cellular ion nanosensors and nano-reactors, in which calcium sensitive biomacromolecules can be triggered for specific biological functions.

  1. The Zeamine Antibiotics Affect the Integrity of Bacterial Membranes

    PubMed Central

    Masschelein, Joleen; Clauwers, Charlien; Stalmans, Karen; Nuyts, Koen; De Borggraeve, Wim; Briers, Yves; Aertsen, Abram; Michiels, Chris W.

    2014-01-01

    The zeamines (zeamine, zeamine I, and zeamine II) constitute an unusual class of cationic polyamine-polyketide-nonribosomal peptide antibiotics produced by Serratia plymuthica RVH1. They exhibit potent bactericidal activity, killing a broad range of Gram-negative and Gram-positive bacteria, including multidrug-resistant pathogens. Examination of their specific mode of action and molecular target revealed that the zeamines affect the integrity of cell membranes. The zeamines provoke rapid release of carboxyfluorescein from unilamellar vesicles with different phospholipid compositions, demonstrating that they can interact directly with the lipid bilayer in the absence of a specific target. DNA, RNA, fatty acid, and protein biosynthetic processes ceased simultaneously at subinhibitory levels of the antibiotics, presumably as a direct consequence of membrane disruption. The zeamine antibiotics also facilitated the uptake of small molecules, such as 1-N-phenylnaphtylamine, indicating their ability to permeabilize the Gram-negative outer membrane (OM). The valine-linked polyketide moiety present in zeamine and zeamine I was found to increase the efficiency of this process. In contrast, translocation of the large hydrophilic fluorescent peptidoglycan binding protein PBDKZ-GFP was not facilitated, suggesting that the zeamines cause subtle perturbation of the OM rather than drastic alterations or defined pore formation. At zeamine concentrations above those required for growth inhibition, membrane lysis occurred as indicated by time-lapse microscopy. Together, these findings show that the bactericidal activity of the zeamines derives from generalized membrane permeabilization, which likely is initiated by electrostatic interactions with negatively charged membrane components. PMID:25452285

  2. Buffers affect the bending rigidity of model lipid membranes.

    PubMed

    Bouvrais, Hélène; Duelund, Lars; Ipsen, John H

    2014-01-14

    In biophysical and biochemical studies of lipid bilayers the influence of the used buffer is often ignored or assumed to be negligible on membrane structure, elasticity, or physical properties. However, we here present experimental evidence, through bending rigidity measurements performed on giant vesicles, of a more complex behavior, where the buffering molecules may considerably affect the bending rigidity of phosphatidylcholine bilayers. Furthermore, a synergistic effect on the bending modulus is observed in the presence of both salt and buffer molecules, which serves as a warning to experimentalists in the data interpretation of their studies, since typical lipid bilayer studies contain buffer and ion molecules.

  3. Iron Deprivation Affects Drug Susceptibilities of Mycobacteria Targeting Membrane Integrity

    PubMed Central

    Pal, Rahul; Hameed, Saif; Fatima, Zeeshan

    2015-01-01

    Multidrug resistance (MDR) acquired by Mycobacterium tuberculosis (MTB) through continuous deployment of antitubercular drugs warrants immediate search for novel targets and mechanisms. The ability of MTB to sense and become accustomed to changes in the host is essential for survival and confers the basis of infection. A crucial condition that MTB must surmount is iron limitation, during the establishment of infection, since iron is required by both bacteria and humans. This study focuses on how iron deprivation affects drug susceptibilities of known anti-TB drugs in Mycobacterium smegmatis, a “surrogate of MTB.” We showed that iron deprivation leads to enhanced potency of most commonly used first line anti-TB drugs that could be reverted upon iron supplementation. We explored that membrane homeostasis is disrupted upon iron deprivation as revealed by enhanced membrane permeability and hypersensitivity to membrane perturbing agent leading to increased passive diffusion of drug and TEM images showing detectable differences in cell envelope thickness. Furthermore, iron seems to be indispensable to sustain genotoxic stress suggesting its possible role in DNA repair machinery. Taken together, we for the first time established a link between cellular iron and drug susceptibility of mycobacteria suggesting iron as novel determinant to combat MDR. PMID:26779346

  4. Factors affecting plant growth in membrane nutrient delivery

    NASA Technical Reports Server (NTRS)

    Dreschel, T. W.; Wheeler, R. M.; Sager, J. C.; Knott, W. M.

    1990-01-01

    The development of the tubular membrane plant growth unit for the delivery of water and nutrients to roots in microgravity has recently focused on measuring the effects of changes in physical variables controlling solution availability to the plants. Significant effects of membrane pore size and the negative pressure used to contain the solution were demonstrated. Generally, wheat grew better in units with a larger pore size but equal negative pressure and in units with the same pore size but less negative pressure. Lettuce also exhibited better plant growth at less negative pressure.

  5. Securin and separase modulate membrane traffic by affecting endosomal acidification.

    PubMed

    Bacac, Marina; Fusco, Carlo; Planche, Anne; Santodomingo, Jaime; Demaurex, Nicolas; Leemann-Zakaryan, Ruzanna; Provero, Paolo; Stamenkovic, Ivan

    2011-05-01

    Securin and separase play a key role in sister chromatid separation during anaphase. However, a growing body of evidence suggests that in addition to regulating chromosome segregation, securin and separase display functions implicated in membrane traffic in Caenorhabditis elegans and Drosophila. Here we show that in mammalian cells both securin and separase associate with membranes and that depletion of either protein causes robust swelling of the trans-Golgi network (TGN) along with the appearance of large endocytic vesicles in the perinuclear region. These changes are accompanied by diminished constitutive protein secretion as well as impaired receptor recycling and degradation. Unexpectedly, cells depleted of securin or separase display defective acidification of early endosomes and increased membrane recruitment of vacuolar (V-) ATPase complexes, mimicking the effect of the specific V-ATPase inhibitor Bafilomycin A1. Taken together, our findings identify a new functional role of securin and separase in the modulation of membrane traffic and protein secretion that implicates regulation of V-ATPase assembly and function.

  6. The formation of ordered nanoclusters controls cadherin anchoring to actin and cell–cell contact fluidity

    PubMed Central

    Strale, Pierre-Olivier; Duchesne, Laurence; Peyret, Grégoire; Montel, Lorraine; Nguyen, Thao; Png, Evelyn; Tampé, Robert; Troyanovsky, Sergey; Hénon, Sylvie; Ladoux, Benoit

    2015-01-01

    Oligomerization of cadherins could provide the stability to ensure tissue cohesion. Cadherins mediate cell–cell adhesion by forming trans-interactions. They form cis-interactions whose role could be essential to stabilize intercellular junctions by shifting cadherin clusters from a fluid to an ordered phase. However, no evidence has been provided so far for cadherin oligomerization in cellulo and for its impact on cell–cell contact stability. Visualizing single cadherins within cell membrane at a nanometric resolution, we show that E-cadherins arrange in ordered clusters, providing the first demonstration of the existence of oligomeric cadherins at cell–cell contacts. Studying the consequences of the disruption of the cis-interface, we show that it is not essential for adherens junction formation. Its disruption, however, increased the mobility of junctional E-cadherin. This destabilization strongly affected E-cadherin anchoring to actin and cell–cell rearrangement during collective cell migration, indicating that the formation of oligomeric clusters controls the anchoring of cadherin to actin and cell–cell contact fluidity. PMID:26195669

  7. Yeast mutants affecting possible quality control of plasma membrane proteins.

    PubMed

    Li, Y; Kane, T; Tipper, C; Spatrick, P; Jenness, D D

    1999-05-01

    Mutations gef1, stp22, STP26, and STP27 in Saccharomyces cerevisiae were identified as suppressors of the temperature-sensitive alpha-factor receptor (mutation ste2-3) and arginine permease (mutation can1(ts)). These suppressors inhibited the elimination of misfolded receptors (synthesized at 34 degrees C) as well as damaged surface receptors (shifted from 22 to 34 degrees C). The stp22 mutation (allelic to vps23 [M. Babst and S. Emr, personal communication] and the STP26 mutation also caused missorting of carboxypeptidase Y, and ste2-3 was suppressed by mutations vps1, vps8, vps10, and vps28 but not by mutation vps3. In the stp22 mutant, both the mutant and the wild-type receptors (tagged with green fluorescent protein [GFP]) accumulated within an endosome-like compartment and were excluded from the vacuole. GFP-tagged Stp22p also accumulated in this compartment. Upon reaching the vacuole, cytoplasmic domains of both mutant and wild-type receptors appeared within the vacuolar lumen. Stp22p and Gef1p are similar to tumor susceptibility protein TSG101 and voltage-gated chloride channel, respectively. These results identify potential elements of plasma membrane quality control and indicate that cytoplasmic domains of membrane proteins are translocated into the vacuolar lumen.

  8. Alteration of membrane phospholipid methylation by adenosine analogs does not affect T lymphocyte activation

    SciTech Connect

    Gormand, F.; Pacheco, Y. ); Fonlupt, P. ); Revillard, J.P. )

    1990-01-01

    Membrane phospholipid methylation has been described during activation of various immune cells. Moreover recent data indicated modulation of immune cells functions by adenosine. As S-adenosyl-methionine and S-adenosyl-homocysteine are adenosine analogs and modulators of transmethylation reactions, the effects of SAH and SAM were investigated on membrane phospholipid methylation and lymphocyte activation. SAM was shown to induce the membrane phospholipid methylation as assessed by the {sup 3}Hmethyl-incorporation in membrane extract. This effect was inhibited by SAH. In contrast SAM and SAH did not affect the phytohemagglutinin-induced proliferative response of peripheral blood mononuclear cells. SAH neither modified the early internalization of membrane CD3 antigens nor did it prevent the late expression of HLA-DR antigens on lymphocytes activated by phytohemagglutinin. These results indicate that in vitro alteration of phospholipid methylation does not affect subsequent steps of human T lymphocyte activation and proliferation.

  9. Membrane fluidization triggers membrane remodeling which affects the thermotolerance in Escherichia coli.

    PubMed

    Shigapova, Natalia; Török, Zsolt; Balogh, Gábor; Goloubinoff, Pierre; Vígh, László; Horváth, Ibolya

    2005-03-25

    Treatment of Escherichia coli with non-lethal doses of heat or benzyl alcohol (BA) causes transient membrane fluidization and permeabilization, and induces the rapid transcription of heat-shock genes in a sigma32-dependent manner. This early response is followed by a rapid adaptation (priming) of the cells to otherwise lethal elevated temperature, in strong correlation with an observed remodeling of the composition and alkyl chain unsaturation of membrane lipids. The acquisition of cellular thermotolerance in BA-primed cells is unrelated to protein denaturation and is not accompanied by the formation of major heat-shock proteins, such as GroEL and DnaK. This suggests that the rapid remodeling of membrane composition is sufficient for the short-term bacterial thermotolerance.

  10. Phosphocreatine interacts with phospholipids, affects membrane properties and exerts membrane-protective effects.

    PubMed

    Tokarska-Schlattner, Malgorzata; Epand, Raquel F; Meiler, Flurina; Zandomeneghi, Giorgia; Neumann, Dietbert; Widmer, Hans R; Meier, Beat H; Epand, Richard M; Saks, Valdur; Wallimann, Theo; Schlattner, Uwe

    2012-01-01

    A broad spectrum of beneficial effects has been ascribed to creatine (Cr), phosphocreatine (PCr) and their cyclic analogues cyclo-(cCr) and phospho-cyclocreatine (PcCr). Cr is widely used as nutritional supplement in sports and increasingly also as adjuvant treatment for pathologies such as myopathies and a plethora of neurodegenerative diseases. Additionally, Cr and its cyclic analogues have been proposed for anti-cancer treatment. The mechanisms involved in these pleiotropic effects are still controversial and far from being understood. The reversible conversion of Cr and ATP into PCr and ADP by creatine kinase, generating highly diffusible PCr energy reserves, is certainly an important element. However, some protective effects of Cr and analogues cannot be satisfactorily explained solely by effects on the cellular energy state. Here we used mainly liposome model systems to provide evidence for interaction of PCr and PcCr with different zwitterionic phospholipids by applying four independent, complementary biochemical and biophysical assays: (i) chemical binding assay, (ii) surface plasmon resonance spectroscopy (SPR), (iii) solid-state (31)P-NMR, and (iv) differential scanning calorimetry (DSC). SPR revealed low affinity PCr/phospholipid interaction that additionally induced changes in liposome shape as indicated by NMR and SPR. Additionally, DSC revealed evidence for membrane packing effects by PCr, as seen by altered lipid phase transition. Finally, PCr efficiently protected against membrane permeabilization in two different model systems: liposome-permeabilization by the membrane-active peptide melittin, and erythrocyte hemolysis by the oxidative drug doxorubicin, hypoosmotic stress or the mild detergent saponin. These findings suggest a new molecular basis for non-energy related functions of PCr and its cyclic analogue. PCr/phospholipid interaction and alteration of membrane structure may not only protect cellular membranes against various insults, but could

  11. Beneficial influence of dietary spices on the ultrastructure and fluidity of the intestinal brush border in rats.

    PubMed

    Prakash, Usha N S; Srinivasan, Krishnapura

    2010-07-01

    The beneficial influence of three common spices was examined in experimental rats on: (i) the membrane fluidity of intestinal brush-border membranes (BBM), (ii) the activity of intestinal membrane-bound enzymes, and (iii) ultrastructural alterations in the intestinal epithelium. Groups of male Wistar rats were maintained on dietary black pepper (0.5 %), red pepper (3.0 %), ginger (0.05 %) and spice bioactive compounds piperine (0.02 %) and capsaicin (0.01 %) for 8 weeks. A membrane fluidity study using an apolar fluorescent probe showed increased BBM fluidity in all the spice-fed animals. This was corroborated by a decreased cholesterol:phospholipid ratio in the jejunal and ileal regions of the intestine. These dietary spices stimulated the activities of BBM enzymes (glycyl-glycine dipeptidase, leucine amino peptidase and gamma-glutamyl transpeptidase) in the jejunal mucosa, suggesting a modulation in membrane dynamics due to the apolar spice bioactive compounds interacting with surrounding lipids and hydrophobic portions in the protein vicinity, which may decrease the tendency of membrane lipids to act as steric constraints to enzyme proteins and thus modify enzyme conformation. Scanning electronic microscopy of the intestinal villi in these spice treatments revealed alterations in the ultrastructure, especially an increase in microvilli length and perimeter which would mean a beneficial increase in the absorptive surface of the small intestine, providing for an increased bioavailability of micronutrients. Thus, dietary spices (black pepper, red pepper and ginger) were evidenced to induce alterations in BBM fluidity and passive permeability property, associated with the induction of an increased microvilli length and perimeter, resulting in an increased absorptive surface of the small intestine.

  12. The depth of porphyrin in a membrane and the membrane's physical properties affect the photosensitizing efficiency.

    PubMed Central

    Lavi, Adina; Weitman, Hana; Holmes, Robert T; Smith, Kevin M; Ehrenberg, Benjamin

    2002-01-01

    Photosensitized biological processes, as applied in photodynamic therapy, are based on light-triggered generation of molecular singlet oxygen by a membrane-residing sensitizer. Most of the sensitizers currently used are hydrophobic or amphiphilic porphyrins and their analogs. The possible activity of the short-lived singlet oxygen is limited to the time it is diffusing in the membrane, before it emerges into the aqueous environment. In this paper we demonstrate the enhancement of the photosensitization process that is obtained by newly synthesized protoporphyrin derivatives, which insert their tetrapyrrole chromophore deeper into the lipid bilayer of liposomes. The insertion was measured by fluorescence quenching by iodide and the photosensitization efficiency was measured with 9,10-dimethylanthracene, a fluorescent chemical target for singlet oxygen. We also show that when the bilayer undergoes a melting phase transition, or when it is fluidized by benzyl alcohol, the sensitization efficiency decreases because of the enhanced diffusion of singlet oxygen. The addition of cholesterol or of dimyristoyl phosphatydilcholine to the bilayer moves the porphyrin deeper into the bilayer; however, the ensuing effect on the sensitization efficiency is different in these two cases. These results could possibly define an additional criterion for the choice and design of hydrophobic, membrane-bound photosensitizers. PMID:11916866

  13. Factors affecting filtration characteristics in membrane-coupled moving bed biofilm reactor.

    PubMed

    Lee, Woo-Nyoung; Kang, In-Joong; Lee, Chung-Hak

    2006-05-01

    Factors affecting filtration characteristics in submerged hollow fiber membrane were investigated in membrane-coupled moving bed biofilm reactor (M-CMBBR). The trend of membrane biofouling in M-CMBBR was quite different from that in a conventional membrane bioreactor (MBR). The M-CMBBR showed much lower biofouling rate than a conventional MBR. Whereas the membrane biofouling in conventional MBR system is known to be dependent mostly on biochemical effects of mixed liquor (soluble COD, EPS, etc.), the extent of biofouling in M-CMBBR was largely dependent on the potential collision energy of biofilm carriers (media) moving freely and colliding with surfaces of submerged hollow fibers. The collisions between circulating media and hollow fiber membranes gave rise to frictional forces which mitigated the formation of biofilms on the outer surface of hollow fibers. Consequently, the membrane permeability was greatly enhanced. The potential collision energy of moving media was dependent on the media volume fraction as well as the air flow rate. The membrane permeability was found to be proportional to the relative potential collision energy of the biofilm carriers. The frictional effect on the morphology of biofilms formed on the surface of organic membrane under various operating condition was also examined and identified through their visualization with SEM and AFM.

  14. Lipid composition affects the rate of photosensitized dissipation of cross-membrane diffusion potential on liposomes

    PubMed Central

    Ytzhak, Shany; Wuskell, Joseph P.; Loew, Leslie M.; Ehrenberg, Benjamin

    2010-01-01

    Hydrophobic or amphiphilic tetrapyrrole sensitizers are taken up by cells and are usually located in cellular lipid membranes. Singlet oxygen is photogenerated by the sensitizer and it diffuses in the membrane and causes oxidative damage to membrane components. This damage can occur to membrane lipids and to membrane-localized proteins. Depolarization of the Nernst electric potential on cells’ membranes has been observed in cellular photosensitization, but it was not established whether lipid oxidation is a relevant factor leading to abolishing the resting potential of cells’ membranes and to their death. In this work we studied the effect of liposomes’ lipid composition on the kinetics of hematoporphyrin-photosensitized dissipation of K+-diffusion electric potential that was generated across the membranes. We employed an electrochromic voltage-sensitive spectroscopic probe that possesses a high fluorescence signal response to the potential. We found a correlation between the structure and unsaturation of lipids and the leakage of the membrane, following photosensitization. As the extent of non-conjugated unsaturation of the lipids is increased from 1 to 6 double bonds, the kinetics of depolarization become faster. We also found that the kinetics of depolarization is affected by the percentage of the unsaturated lipids in the liposome: as the fraction of the unsaturated lipids increases the leakage trough the membrane is enhanced. When liposomes are composed of a lipid mixture similar to that of natural membranes and photosensitization is being carried out under usual photodynamic therapy (PDT) conditions, photodamage to the lipids is not likely to cause enhanced permeability of ions through the membrane, which would have been a mechanism that leads to cell death. PMID:20536150

  15. Possible evolutionary origins of human female sexual fluidity.

    PubMed

    Kanazawa, Satoshi

    2016-05-16

    I propose an evolutionary theory of human female sexual fluidity and argue that women may have been evolutionarily designed to be sexually fluid in order to allow them to have sex with their cowives in polygynous marriage and thus reduce conflict and tension inherent in such marriage. In addition to providing an extensive definition and operationalization of the concept of sexual fluidity and specifying its ultimate function for women, the proposed theory can potentially solve several theoretical and empirical puzzles in evolutionary psychology and sex research. Analyses of the National Longitudinal Study of Adolescent Health (Add Health) confirm the theory's predictions that: (i) women (but not men) who experience increased levels of sexual fluidity have a larger number of children (suggesting that female sexual fluidity, if heritable, may be evolutionarily selected); (ii) women (but not men) who experience marriage or parenthood early in adult life subsequently experience increased levels of sexual fluidity; and (iii) sexual fluidity is significantly positively correlated with known markers of unrestricted sexual orientation among women whereas it is significantly negatively correlated with such markers among men.

  16. Interaction of polyene antibiotics with sterols in phosphatidylcholine bilayer membranes as studied by spin probes.

    PubMed

    Ohki, K; Nozawa, Y; Ohnishi, S I

    1979-06-13

    Interaction of filipin and amphotericin B with sterols in phosphatidylcholine membranes has been studied using various spin probes; epiandrosterone, cholestanone, phosphatidylcholine with 12-nitroxide or 5-nitroxide stearate attached to 2 position and also with tempocholine at the head group. Filipin caused increase in the fluidity of cholesterol-containing phosphatidylcholine membranes near the center, while it rather decreased the fluidity near the polar surface. On the other hand, amphotericin B did not apparently affect the fluidity. In the electron spin resonance spectrum of steriod spin probes in the antibiotic-containing membranes, both bound and free signals were observed and the association constant was calculated from the siganal intensity. In the binding of steriods with filipin, both 3 and 17 positions were involved, while the 17 positions was less involved in the binding with amphotericin B. Phase change in the host membrane markedly affected the interaction of filipin with epiandrosterone probe. The bound fraction jumped from 0.4 to 0.8 on going to the crystalline state and increased further with decrease in temperature. The overall splitting of the bound signal also increased on lowering the temperature below phase transition. This change was attributed to aggregate formation of filipin-steriod complexes in the crystalline state. On the other hand, effect of phase transition was much smaller on the interaction of amphotericin B with the steriod probe.

  17. Sustained Epigenetic Drug Delivery Depletes Cholesterol-Sphingomyelin Rafts from Resistant Breast Cancer Cells, Influencing Biophysical Characteristics of Membrane Lipids.

    PubMed

    Raghavan, Vijay; Vijayaraghavalu, Sivakumar; Peetla, Chiranjeevi; Yamada, Masayoshi; Morisada, Megan; Labhasetwar, Vinod

    2015-10-27

    Cell-membrane lipid composition can greatly influence biophysical properties of cell membranes, affecting various cellular functions. We previously showed that lipid synthesis becomes altered in the membranes of resistant breast cancer cells (MCF-7/ADR); they form a more rigid, hydrophobic lipid monolayer than do sensitive cell membranes (MCF-7). These changes in membrane lipids of resistant cells, attributed to epigenetic aberration, significantly affected drug transport and endocytic function, thus impacting the efficacy of anticancer drugs. The present study's objective was to determine the effects of the epigenetic drug, 5-aza-2'-deoxycytidine (DAC), delivered in sustained-release nanogels (DAC-NGs), on the composition and biophysical properties of membrane lipids of resistant cells. Resistant and sensitive cells were treated with DAC in solution (DAC-sol) or DAC-NGs, and cell-membrane lipids were isolated and analyzed for lipid composition and biophysical properties. In resistant cells, we found increased formation of cholesterol-sphingomyelin (CHOL-SM) rafts with culturing time, whereas DAC treatment reduced their formation. In general, the effect of DAC-NGs was greater in changing the lipid composition than with DAC-sol. DAC treatment also caused a rise in levels of certain phospholipids and neutral lipids known to increase membrane fluidity, while reducing the levels of certain lipids known to increase membrane rigidity. Isotherm data showed increased lipid membrane fluidity following DAC treatment, attributed to decrease levels of CHOL-SM rafts (lamellar beta [Lβ] structures or ordered gel) and a corresponding increase in lipids that form lamellar alpha-structures (Lα, liquid crystalline phase). Sensitive cells showed marginal or insignificant changes in lipid profile following DAC-treatment, suggesting that epigenetic changes affecting lipid biosynthesis are more specific to resistant cells. Since membrane fluidity plays a major role in drug transport

  18. Truncated brush border myosin I affects membrane traffic in polarized epithelial cells.

    PubMed

    Durrbach, A; Raposo, G; Tenza, D; Louvard, D; Coudrier, E

    2000-05-01

    We investigate, in this study, the potential involvement of an acto-myosin-driven mechanism in endocytosis of polarized cells. We observed that depolymerization of actin filaments using latrunculin A decreases the rate of transferrin recycling to the basolateral plasma membrane of Caco-2 cells, and increases its delivery to the apical plasma membrane. To analyze whether a myosin was involved in endocytosis, we produced, in this polarized cell line, truncated, non-functional, brush border, myosin I proteins (BBMI) that we have previously demonstrated to have a dominant negative effect on endocytosis of unpolarized cells. These non-functional proteins affect the rate of transferrin recycling and the rate of transepithelial transport of dipeptidyl-peptidase IV from the basolateral plasma membrane to the apical plasma membrane. They modify the distribution of internalized endocytic tracers in apical multivesicular endosomes that are accessible to fluid phase tracers internalized from apical and basolateral plasma membrane domains. Altogether, these observations suggest that an acto-myosin-driven mechanism is involved in the trafficking of basolaterally internalized molecules to the apical plasma membrane.

  19. α-Synuclein Oligomers Induced by Docosahexaenoic Acid Affect Membrane Integrity

    PubMed Central

    Fecchio, Chiara; De Franceschi, Giorgia; Relini, Annalisa; Greggio, Elisa; Dalla Serra, Mauro; Bubacco, Luigi; Polverino de Laureto, Patrizia

    2013-01-01

    A key feature of Parkinson disease is the aggregation of α-synuclein and its intracellular deposition in fibrillar form. Increasing evidence suggests that the pathogenicity of α-synuclein is correlated with the activity of oligomers formed in the early stages of its aggregation process. Oligomers toxicity seems to be associated with both their ability to bind and affect the integrity of lipid membranes. Previously, we demonstrated that α-synuclein forms oligomeric species in the presence of docosahexaenoic acid and that these species are toxic to cells. Here we studied how interaction of these oligomers with membranes results in cell toxicity, using cellular membrane-mimetic and cell model systems. We found that α-synuclein oligomers are able to interact with large and small unilamellar negatively charged vesicles acquiring an increased amount of α-helical structure, which induces small molecules release. We explored the possibility that oligomers effects on membranes could be due to pore formation, to a detergent-like effect or to fibril growth on the membrane. Our biophysical and cellular findings are consistent with a model where α-synuclein oligomers are embedded into the lipid bilayer causing transient alteration of membrane permeability. PMID:24312431

  20. Deoxygenation affects tyrosine phosphoproteome of red cell membrane from patients with sickle cell disease.

    PubMed

    Siciliano, Angela; Turrini, Franco; Bertoldi, Mariarita; Matte, Alessandro; Pantaleo, Antonella; Olivieri, Oliviero; De Franceschi, Lucia

    2010-04-15

    Sickle cell disease (SCD) is a worldwide distributed hereditary red cell disorder related to the production of a defective form of hemoglobin, hemoglobin S (HbS). One of the hallmarks of SCD is the presence of dense, dehydrate highly adhesive sickle red blood cells (RBCs) that result from persistent membrane damage associated with HbS polymerization, abnormal activation of membrane cation transports and generation of distorted and rigid red cells with membrane perturbation and cytoskeleton dysfunction. Although modulation of phosphorylation state of the proteins from membrane and cytoskeleton networks has been proposed to participate in red cell homeostasis, much still remains to be investigated in normal and diseased red cells. Here, we report that tyrosine (Tyr-) phosphoproteome of sickle red cells was different from normal controls and was affected by deoxygenation. We found proteins, p55 and band 4.1, from the junctional complex, differently Tyr-phosphorylated in SCD RBCs compared to normal RBCs under normoxia and modulated by deoxygenation, while band 4.2 was similarly Tyr-phosphorylated in both conditions. In SCD RBCs we identified the phosphopeptides for protein 4.1R located in the protein FERM domain (Tyr-13) and for alpha-spectrin located near or in a linker region (Tyr-422 and Tyr-1498) involving protein areas crucial for their functions in the context of red cell membrane properties, suggesting that Tyr-phosphorylation may be part of the events involved in maintaining membrane mechanical stability in SCD red cells.

  1. [MORPHOLOGICAL FEATURES OF RAT MUCOUS MEMBRANE OF THE TONGUE EARLY AFFECTED BY ACRYLIC RESIN MONOMER].

    PubMed

    Davydenko, V; Nidzelskiy, M; Starchenko, I; Davydenko, A; Kuznetsov, V

    2016-03-01

    Base materials, made on the basis of various derivatives of acrylic and methacrylic acids, have been widely used in prosthetic dentistry. Free monomer, affecting the tissues of prosthetic bed and the whole body, is always found in dentures. Therefore, study of the effect of acrylic resins' monomer on mucous membrane of the tongue is crucial. Rat tongue is very similar to human tongue, and this fact has become the basis for selecting these animals to be involved into the experiment. The paper presents the findings related to the effect of "Ftoraks" base acrylic resin monomer on the state of rat mucous membrane of the tongue and its regeneration. The microscopy has found that the greatest changes in the mucous membrane of the tongue occur on day 3 and 7 day after applying the monomer and are of erosive and inflammatory nature. Regeneration of tongue epithelium slows down.

  2. Identification of Yeast Genes Involved in K+ Homeostasis: Loss of Membrane Traffic Genes Affects K+ Uptake

    PubMed Central

    Fell, Gillian L.; Munson, Amanda M.; Croston, Merriah A.; Rosenwald, Anne G.

    2011-01-01

    Using the homozygous diploid Saccharomyces deletion collection, we searched for strains with defects in K+ homeostasis. We identified 156 (of 4653 total) strains unable to grow in the presence of hygromycin B, a phenotype previously shown to be indicative of ion defects. The most abundant group was that with deletions of genes known to encode membrane traffic regulators. Nearly 80% of these membrane traffic defective strains showed defects in uptake of the K+ homolog, 86Rb+. Since Trk1, a plasma membrane protein localized to lipid microdomains, is the major K+ influx transporter, we examined the subcellular localization and Triton-X 100 insolubility of Trk1 in 29 of the traffic mutants. However, few of these showed defects in the steady state levels of Trk1, the localization of Trk1 to the plasma membrane, or the localization of Trk1 to lipid microdomains, and most defects were mild compared to wild-type. Three inositol kinase mutants were also identified, and in contrast, loss of these genes negatively affected Trk1 protein levels. In summary, this work reveals a nexus between K+ homeostasis and membrane traffic, which does not involve traffic of the major influx transporter, Trk1. PMID:22384317

  3. Identification of yeast genes involved in k homeostasis: loss of membrane traffic genes affects k uptake.

    PubMed

    Fell, Gillian L; Munson, Amanda M; Croston, Merriah A; Rosenwald, Anne G

    2011-06-01

    Using the homozygous diploid Saccharomyces deletion collection, we searched for strains with defects in K(+) homeostasis. We identified 156 (of 4653 total) strains unable to grow in the presence of hygromycin B, a phenotype previously shown to be indicative of ion defects. The most abundant group was that with deletions of genes known to encode membrane traffic regulators. Nearly 80% of these membrane traffic defective strains showed defects in uptake of the K(+) homolog, (86)Rb(+). Since Trk1, a plasma membrane protein localized to lipid microdomains, is the major K(+) influx transporter, we examined the subcellular localization and Triton-X 100 insolubility of Trk1 in 29 of the traffic mutants. However, few of these showed defects in the steady state levels of Trk1, the localization of Trk1 to the plasma membrane, or the localization of Trk1 to lipid microdomains, and most defects were mild compared to wild-type. Three inositol kinase mutants were also identified, and in contrast, loss of these genes negatively affected Trk1 protein levels. In summary, this work reveals a nexus between K(+) homeostasis and membrane traffic, which does not involve traffic of the major influx transporter, Trk1.

  4. Application of forward osmosis membrane technology for oil sands process-affected water desalination.

    PubMed

    Jiang, Yaxin; Liang, Jiaming; Liu, Yang

    2016-01-01

    The extraction process used to obtain bitumen from the oil sands produces large volumes of oil sands process-affected water (OSPW). As a newly emerging desalination technology, forward osmosis (FO) has shown great promise in saving electrical power requirements, increasing water recovery, and minimizing brine discharge. With the support of this funding, a FO system was constructed using a cellulose triacetate FO membrane to test the feasibility of OSPW desalination and contaminant removal. The FO systems were optimized using different types and concentrations of draw solution. The FO system using 4 M NH4HCO3 as a draw solution achieved 85% water recovery from OSPW, and 80 to 100% contaminant rejection for most metals and ions. A water backwash cleaning method was applied to clean the fouled membrane, and the cleaned membrane achieved 77% water recovery, a performance comparable to that of new FO membranes. This suggests that the membrane fouling was reversible. The FO system developed in this project provides a novel and energy efficient strategy to remediate the tailings waters generated by oil sands bitumen extraction and processing.

  5. Studies of Relationships among Bile Flow, Liver Plasma Membrane NaK-ATPase, and Membrane Microviscosity in the Rat

    PubMed Central

    Keeffe, Emmet B.; Scharschmidt, Bruce F.; Blankenship, Nancy M.; Ockner, Robert K.

    1979-01-01

    Liver plasma membrane (LPM) NaK-ATPase activity, LPM fluidity, and bile acid-independent flow (BAIF) were studied in rats pretreated with one of five experimental agents. Compared with controls, BAIF was increased 24.6% by thyroid hormone and 34.4% by phenobarbital, decreased by ethinyl estradiol, but unchanged by propylene glycol and cortisone acetate. Parallel to the observed changes in BAIF, NaK-ATPase activity also was increased by thyroid hormone (40.8%) and decreased by ethinyl estradiol (26.2%). In contrast, NaK-ATPase activity failed to increase after phenobarbital but did increase 36% after propylene glycol and 34.8% after cortisone acetate. Thus BAIF and NaK-ATPase activity did not always change in parallel. The NaK-ATPase Km for ATP was not affected by any of these agents. LPM fluidity, measured by fluorescence polarization using the probe 1,6-diphenyl-1,3,5-hexatriene, was found to be increased by propylene glycol, thyroid hormone, and cortisone acetate, decreased by ethinyl estradiol, and unaffected by phenobarbital. Thus in these cases, induced changes in LPM fluidity paralleled those in NaK-ATPase activity. In no case did Mg-ATPase or 5′-nucleotidase activities change in the same direction as NaK-ATPase, and the activity of neither of these enzymes correlated with LPM fluidity, thus indicating the selective nature of the changes in LPM enzyme activity caused by the agents. These findings indicate that LPM fluidity correlates with NaK-ATPase activity and may influence the activity of this enzyme. However, the nature of the role of LPM NaK-ATPase in bile secretion is uncertain and needs further study. Images PMID:227937

  6. Beyond Alphabet Soup: Helping College Health Professionals Understand Sexual Fluidity

    ERIC Educational Resources Information Center

    Oswalt, Sara B.; Evans, Samantha; Drott, Andrea

    2016-01-01

    Many college students today are no longer using the terms straight, gay, lesbian, bisexual, or transgender to self-identify their sexual orientation or gender identity. This commentary explores research related to fluidity of sexual identities, emerging sexual identities used by college students, and how these identities interact with the health…

  7. Microvillus inclusion disease: a genetic defect affecting apical membrane protein traffic in intestinal epithelium.

    PubMed

    Ameen, N A; Salas, P J

    2000-01-01

    The striking similarities between microvillus inclusions (MIs) in enterocytes in microvillus inclusion disease (MID) and vacuolar apical compartment in tissue culture epithelial cells, led us to analyze endoscopic biopsies of duodenal mucosa of a patient after the samples were used for diagnostic procedures. Samples from another patient with an unrelated disease were used as controls. The MID enterocytes showed a decrease in the thickness of the apical F-actin layer, and normal microtubules. The immunofluorescence analysis of the distribution of five apical membrane markers (sucrase isomaltase, alkaline phosphatase, NHE-3 Na+/H+ exchanger, cGMP-dependent protein kinase, and cystic fibrosis trans-membrane conductance regulator), showed low levels of these proteins in their standard localization at the apical membrane as compared with normal duodenal epithelium processed in parallel. Instead, four of these markers were found in a diffuse distribution in the apical cytoplasm, below the terminal web (as indicated by co-localization with F-actin and cytokeratin 19), and in MIs as well. The basolateral protein Na(+)-K+ATPase, in contrast, was normally localized. These results support the hypothesis that MID may represent the first genetic defect affecting apical membrane traffic, possibly in a late step of apical exocytosis.

  8. Multi-walled carbon nanotubes affect drug transport across cell membrane in rat astrocytes

    NASA Astrophysics Data System (ADS)

    Chen, Xiao; Schluesener, Hermann J.

    2010-03-01

    The impact of carbon nanotubes on the cell membrane is an aspect of particular importance and interest in the study of carbon nanotubes' interactions with living systems. One of the many functions of the cell membrane is to execute substance transport into and out of the cell. We investigated the influence of multi-walled carbon nanotubes (MWCNTs) on the transport of several compounds across in the cell membrane of rat astrocytes using flow cytometry. These compounds are fluorescein diacetate, carboxyfluorescein diacetate, rhodamine 123 and doxorubicin, which are prosubstrate/substrates of multidrug transporter proteins. Results showed that MWCNTs significantly inhibited cellular uptake of doxorubicin but not the other drugs and the mode of loading made a significant difference in doxorubicin uptake. Retention of fluorescein, carboxyfluorescein and rhodamine 123 was remarkably higher in MWCNT-exposed cells after an efflux period. A kinetics study also demonstrated slower efflux of intracellular fluorescein and rhodamine 123. Data presented in this paper suggest that MWCNTs could affect drug transport across cell membranes. The implications of the findings are discussed.

  9. The Lipid Composition and Physical Properties of the Yeast Vacuole Affect the Hemifusion-Fusion Transition

    PubMed Central

    Karunakaran, Surya; Fratti, Rutilio A.

    2013-01-01

    Yeast vacuole fusion requires the formation of SNARE bundles between membranes. Although the function of vacuolar SNAREs is controlled in part by regulatory lipids, the exact role of the membrane in regulating fusion remains unclear. Because SNAREs are membrane-anchored and transmit the force required for fusion to the bilayer, we hypothesized that the lipid composition and curvature of the membrane aid in controlling fusion. Here, we examined the effect of altering membrane fluidity and curvature on the functionality of fusion-incompetent SNARE mutants that are thought to generate insufficient force to trigger the hemifusion-fusion transition. The hemifusion-fusion transition was inhibited by disrupting the 3Q:1R stoichiometry of SNARE bundles with the mutant SNARE Vam7pQ283R. Similarly, replacing the transmembrane domain of the syntaxin homolog Vam3p with a lipid anchor allowed hemifusion, but not content mixing. Hemifusion-stalled reactions containing either of the SNARE mutants were stimulated to fuse with chlorpromazine, an amphipathic molecule that alters membrane fluidity and curvature. The activity of mutant SNAREs was also rescued by the overexpression of SNAREs, thus multiplying the force transferred to the membrane. Thus, we conclude that either increasing membrane fluidity, or multiplying SNARE-generated energy restored the fusogenicity of mutant SNAREs that are stalled at hemifusion. We also found that regulatory lipids differentially modulated the complex formation of wild-type SNAREs. Together, these data indicate that the physical properties and the lipid composition of the membrane affect the function of SNAREs in promoting the hemifusion-fusion transition. PMID:23438067

  10. PMCA activity and membrane tubulin affect deformability of erythrocytes from normal and hypertensive human subjects.

    PubMed

    Monesterolo, Noelia E; Nigra, Ayelen D; Campetelli, Alexis N; Santander, Verónica S; Rivelli, Juan F; Arce, Carlos A; Casale, Cesar H

    2015-11-01

    Our previous studies demonstrated formation of a complex between acetylated tubulin and brain plasma membrane Ca(2+)-ATPase (PMCA), and the effect of the lipid environment on structure of this complex and on PMCA activity. Deformability of erythrocytes from hypertensive human subjects was reduced by an increase in membrane tubulin content. In the present study, we examined the regulation of PMCA activity by tubulin in normotensive and hypertensive erythrocytes, and the effect of exogenously added diacylglycerol (DAG) and phosphatidic acid (PA) on erythrocyte deformability. Some of the key findings were that: (i) PMCA was associated with tubulin in normotensive and hypertensive erythrocytes, (ii) PMCA enzyme activity was directly correlated with erythrocyte deformability, and (iii) when tubulin was present in the erythrocyte membrane, treatment with DAG or PA led to increased deformability and associated PMCA activity. Taken together, our findings indicate that PMCA activity is involved in deformability of both normotensive and hypertensive erythrocytes. This rheological property of erythrocytes is affected by acetylated tubulin and its lipid environment because both regulate PMCA activity.

  11. Fragmentation, fluidity, and transformation: nonlinear development in middle childhood.

    PubMed

    Knight, Rona

    2011-01-01

    The results of a small group of children studied through ages six through eleven suggest that latency is no longer an accurate term to describe middle childhood and preadolescence. This longitudinal research suggests a more nonlinear process than has previously been documented in psychoanalytic research and supports a dynamic systems approach to development. Self structures break down and remain in an ongoing state of non-linear development. Without stable structural organization, sexual and aggressive thoughts and feelings are less contained and less differentiated throughout this period of development. Gender role identity is in a continuous state of fluidity during middle childhood. While both boys and girls experience gender role fluidity, the meaning of male and female gender identifications and the expression of sexual and aggressive feelings differ for boys and girls.

  12. The fluidity of blood in African elephants (Loxodonta africana).

    PubMed

    Windberger, U; Plasenzotti, R; Voracek, Th

    2005-01-01

    The large cellular volume of erythrocytes and the increased plasma concentration of proteins in elephants are factors which potentially affect blood rheology adversely. To verify blood rheology, routine hemorheologic variables were analyzed in four African elephants (Loxodonta africana), housed in the zoo of Vienna. Whole blood viscosity at three different shear rates (WBV at low shear rate: WBV 0.7 s(-1) and WBV 2.4 s(-1); WBV at high shear rate: WBV 94 s(-1) done by LS30, Contraves) and erythrocyte aggregation (aggregation indices AI by LS30; aggregation indices M0, M1 by Myrenne aggregometer) were high (WBV 94 s(-1): 5.368 (5.246/5.648); WBV 2.4 s(-1): 16.291 (15.605/17.629); WBV 0.7 s(-1): 28.28 (25.537/32.173) mPa s; AI 2.4 s(-1): 0.25 (0.23/0.30); AI 0.7 s(-1): 0.24 (0.23/0.28); M0: 7.8 (6.4/8.4); M1: 30.2 (25/31)). Plasma viscosity (PV) was increased as well (1.865 (1.857/1.912) mPa s) compared to other mammalian species. These parameters would indicate a decrease in blood fluidity in elephants. However, erythrocyte rigidity (LORCA, Mechatronics) was decreased, which in contrast, has a promotive effect on peripheral perfusion. Blood rheology of the elephants was determined by a high whole blood and plasma viscosity as the result of pronounced erythrocyte aggregation and high plasma protein concentration. Thus, in the terminal vessels the resistance to flow will be increased. The large erythrocytes, which might impede blood flow further due to geometrical reasons, however, had a pronounced flexibility. We conclude that the effect of the increased inner resistance to peripheral blood flow was counteracted by the decreased rigidity of the erythrocytes to enable an adequate blood flow in African elephants.

  13. Lipid compositions modulate fluidity and stability of bilayers: characterization by surface pressure and sum frequency generation spectroscopy.

    PubMed

    Liu, Wei; Wang, Zhuguang; Fu, Li; Leblanc, Roger M; Yan, Elsa C Y

    2013-12-03

    Cell membranes are crucial to many biological processes. Because of their complexity, however, lipid bilayers are often used as model systems. Lipid structures influence the physical properties of bilayers, but their interplay, especially in multiple-component lipid bilayers, has not been fully explored. Here, we used the Langmuir-Blodgett method to make mono- and bilayers of 1,2-dihexadecanoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (DPPG), 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (POPG), and 1-hexadecanoyl-2-(9Z-octadecenoyl)-sn-glycero-3-phospho-L-serine (POPS) as well as their 1:1 binary mixtures. We studied the fluidity, stability, and rigidity of these structures using sum frequency generation (SFG) spectroscopy combined with analyses of surface pressure-area isotherms, compression modulus, and stability. Our results show that single-component bilayers, both saturated and unsaturated, may not be ideal membrane mimics because of their low fluidity and/or stability. However, the binary saturated and unsaturated DPPG/POPG and DPPG/POPS systems show not only high stability and fluidity but also high resistance to changes in surface pressure, especially in the range of 25-35 mN/m, the range typical of cell membranes. Because the ratio of saturated to unsaturated lipids is highly regulated in cells, our results underline the possibility of modulating biological properties using lipid compositions. Also, our use of flat optical windows as solid substrates in SFG experiments should make the SFG method more compatible with other techniques, enabling more comprehensive future surface characterizations of bilayers.

  14. Partial calcium depletion during membrane filtration affects gelation of reconstituted milk protein concentrates.

    PubMed

    Eshpari, H; Jimenez-Flores, R; Tong, P S; Corredig, M

    2015-12-01

    Milk protein concentrate powders (MPC) with improved rehydration properties are often manufactured using processing steps, such as acidification and high-pressure processing, and with addition of other ingredients, such as sodium chloride, during their production. These steps are known to increase the amount of serum caseins or modify the mineral equilibrium, hence improving solubility of the retentates. The processing functionality of the micelles may be affected. The aim of this study was to investigate the effects of partial acidification by adding glucono-δ-lactone (GDL) to skim milk during membrane filtration on the structural changes of the casein micelles by observing their chymosin-induced coagulation behavior, as such coagulation is affected by both the supramolecular structure of the caseins and calcium equilibrium. Milk protein concentrates were prepared by preacidification with GDL to pH 6 using ultrafiltration (UF) and diafiltration (DF) followed by spray-drying. Reconstituted UF and DF samples (3.2% protein) treated with GDL showed significantly increased amounts of soluble calcium and nonsedimentable caseins compared with their respective controls, as measured by ion chromatography and sodium dodecyl sulfate-PAGE electrophoresis, respectively. The primary phase of chymosin-induced gelation was not significantly different between treatments as measured by the amount of caseino-macropeptide released. The rheological properties of the reconstituted MPC powders were determined immediately after addition of chymosin, both before and after dialysis against skim milk, to ensure similar serum composition for all samples. Reconstituted samples before dialysis showed no gelation (defined as tan δ=1), and after re-equilibration only control UF and DF samples showed gelation. The gelation properties of reconstituted MPC powders were negatively affected by the presence of soluble casein, and positively affected by the amount of both soluble and insoluble

  15. Membrane transporters and protein traffic networks differentially affecting metal tolerance: a genomic phenotyping study in yeast

    PubMed Central

    Ruotolo, Roberta; Marchini, Gessica; Ottonello, Simone

    2008-01-01

    Background The cellular mechanisms that underlie metal toxicity and detoxification are rather variegated and incompletely understood. Genomic phenotyping was used to assess the roles played by all nonessential Saccharomyces cerevisiae proteins in modulating cell viability after exposure to cadmium, nickel, and other metals. Results A number of novel genes and pathways that affect multimetal as well as metal-specific tolerance were discovered. Although the vacuole emerged as a major hot spot for metal detoxification, we also identified a number of pathways that play a more general, less direct role in promoting cell survival under stress conditions (for example, mRNA decay, nucleocytoplasmic transport, and iron acquisition) as well as proteins that are more proximally related to metal damage prevention or repair. Most prominent among the latter are various nutrient transporters previously not associated with metal toxicity. A strikingly differential effect was observed for a large set of deletions, the majority of which centered on the ESCRT (endosomal sorting complexes required for transport) and retromer complexes, which - by affecting transporter downregulation and intracellular protein traffic - cause cadmium sensitivity but nickel resistance. Conclusion The data show that a previously underestimated variety of pathways are involved in cadmium and nickel tolerance in eukaryotic cells. As revealed by comparison with five additional metals, there is a good correlation between the chemical properties and the cellular toxicity signatures of various metals. However, many conserved pathways centered on membrane transporters and protein traffic affect cell viability with a surprisingly high degree of metal specificity. PMID:18394190

  16. Membrane protein assembly: two cytoplasmic phosphorylated serine sites of Vpu from HIV-1 affect oligomerization

    PubMed Central

    Chen, Chin-Pei; Lin, Meng-Han; Chan, Ya-Ting; Chen, Li-Chyong; Ma, Che; Fischer, Wolfgang B.

    2016-01-01

    Viral protein U (Vpu) encoded by human immunodeficiency virus type 1 (HIV-1) is a short integral membrane protein which is known to self-assemble within the lipid membrane and associate with host factors during the HIV-1 infectivity cycle. In this study, full-length Vpu (M group) from clone NL4-3 was over-expressed in human cells and purified in an oligomeric state. Various single and double mutations were constructed on its phosphorylation sites to mimic different degrees of phosphorylation. Size exclusion chromatography of wild-type Vpu and mutants indicated that the smallest assembly unit of Vpu was a dimer and over time Vpu formed higher oligomers. The rate of oligomerization increased when (i) the degree of phosphorylation at serines 52 and 56 was decreased and (ii) when the ionic strength was increased indicating that the cytoplasmic domain of Vpu affects oligomerization. Coarse-grained molecular dynamic simulations with models of wild-type and mutant Vpu in a hydrated lipid bilayer supported the experimental data in demonstrating that, in addition to a previously known role in downregulation of host factors, the phosphorylation sites of Vpu also modulate oligomerization. PMID:27353136

  17. Effect of liposomal fluidity on skin permeation of sodium fluorescein entrapped in liposomes

    PubMed Central

    Subongkot, Thirapit; Ngawhirunpat, Tanasait

    2015-01-01

    The purpose of this study was to investigate the effect of ultradeformable liposome components, Tween 20 and terpenes, on vesicle fluidity. The fluidity was evaluated by electron spin resonance spectroscopy using 5-doxyl stearic acid and 16-doxyl stearic acid as spin labels for phospholipid bilayer fluidity at the C5 atom of the acyl chain near the polar head group (hydrophilic region) and the C16 atom of the acyl chain (lipophilic region), respectively. The electron spin resonance study revealed that Tween 20 increased the fluidity at the C5 atom of the acyl chain, whereas terpenes increased the fluidity at the C16 atom of the acyl chain of the phospholipid bilayer. The increase in liposomal fluidity resulted in the increased skin penetration of sodium fluorescein. Confocal laser scanning microscopy showed that ultradeformable liposomes with terpenes increase the skin penetration of sodium fluorescein by enhancing hair follicle penetration. PMID:26229462

  18. The evolution of endothermy: role for membranes and molecular activity.

    PubMed

    Else, Paul L; Turner, N; Hulbert, A J

    2004-01-01

    On the basis of the comparative approach and three models of metabolism (endothermic and ectothermic vertebrates, body mass, and mammalian development), we suggest that a few common cellular processes, linked either directly or indirectly to membranes, consume the majority of energy used by most organisms; that membranes act as pacemakers of metabolism through changes in lipid composition, altering membrane characteristics and the working environment of membrane proteins--specifically, that changes in the membrane environment similarly affect the molecular activities (specific rates of activity) of membrane-bound proteins; and that polyunsaturation of membranes increases whereas monounsaturation decreases the activity of membrane proteins. Experiments designed to test this theory using the sodium pump support this supposition. Potential mechanisms considered include fluidity, electrical fields, and related surface area requirements of lipids. In considering the evolution of endothermy in mammals, for example, if the first mammals were small, possibly nocturnal and active organisms, all these factors would favour increased polyunsaturation of membranes. Such changes (from monounsaturated to polyunsaturated membranes) would allow membranes to set the pace of metabolism in the evolution of endothermy.

  19. Microscopic Description of the Granular Fluidity Field in Nonlocal Flow Modeling.

    PubMed

    Zhang, Qiong; Kamrin, Ken

    2017-02-03

    A recent granular rheology based on an implicit "granular fluidity" field has been shown to quantitatively predict many nonlocal phenomena. However, the physical nature of the field has not been identified. Here, the granular fluidity is found to be a kinematic variable given by the velocity fluctuation and packing fraction. This is verified with many discrete element simulations, which show that the operational fluidity definition, solutions of the fluidity model, and the proposed microscopic formula all agree. Kinetic theoretical and Eyring-like explanations shed insight into the obtained form.

  20. Microscopic Description of the Granular Fluidity Field in Nonlocal Flow Modeling

    NASA Astrophysics Data System (ADS)

    Zhang, Qiong; Kamrin, Ken

    2017-02-01

    A recent granular rheology based on an implicit "granular fluidity" field has been shown to quantitatively predict many nonlocal phenomena. However, the physical nature of the field has not been identified. Here, the granular fluidity is found to be a kinematic variable given by the velocity fluctuation and packing fraction. This is verified with many discrete element simulations, which show that the operational fluidity definition, solutions of the fluidity model, and the proposed microscopic formula all agree. Kinetic theoretical and Eyring-like explanations shed insight into the obtained form.

  1. Soluble Amyloid β-Oligomers Affect Dielectric Membrane Properties by Bilayer Insertion and Domain Formation: Implications for Cell Toxicity

    PubMed Central

    Valincius, Gintaras; Heinrich, Frank; Budvytyte, Rima; Vanderah, David J.; McGillivray, Duncan J.; Sokolov, Yuri; Hall, James E.; Lösche, Mathias

    2008-01-01

    It is well established that Alzheimer's amyloid β-peptides reduce the membrane barrier to ion transport. The prevailing model ascribes the resulting interference with ion homeostasis to the formation of peptide pores across the bilayer. In this work, we examine the interaction of soluble prefibrillar amyloid β (Aβ1–42)-oligomers with bilayer models, observing also dramatic increases in ion current at micromolar peptide concentrations. We demonstrate that the Aβ-induced ion conductances across free-standing membranes and across substrate-supported “tethered” bilayers are quantitatively similar and depend on membrane composition. However, characteristic signatures of the molecular transport mechanism were distinctly different from ion transfer through water-filled pores, as shown by a quantitative comparison of the membrane response to Aβ-oligomers and to the bacterial toxin α-hemolysin. Neutron reflection from tethered membranes showed that Aβ-oligomers insert into the bilayer, affecting both membrane leaflets. By measuring the capacitance of peptide-free membranes, as well as their geometrical thicknesses, the dielectric constants in the aliphatic cores of 1,2-dioleoyl-sn-glycero-3-phosphocholine and 1,2-diphytanoyl-sn-glycero-3-phosphocholine bilayers were determined to be ɛ = 2.8 and 2.2, respectively. The magnitude of the Aβ-induced increase in ɛ indicates that Aβ-oligomers affect membranes by inducing lateral heterogeneity in the bilayers, but an increase in the water content of the bilayers was not observed. The activation energy for Aβ-induced ion transport across the membrane is at least three times higher than that measured for membranes reconstituted with α-hemolysin pores, Ea = 36.8 vs. 9.9 kJ/mol, indicating that the molecular mechanisms underlying both transport processes are fundamentally different. The Aβ-induced membrane conductance shows a nonlinear dependence on the peptide concentration in the membrane. Moreover, Ea depends on

  2. Fluidization of membrane lipids enhances the tolerance of Saccharomyces cerevisiae to freezing and salt stress.

    PubMed

    Rodríguez-Vargas, Sonia; Sánchez-García, Alicia; Martínez-Rivas, Jose Manuel; Prieto, Jose Antonio; Randez-Gil, Francisca

    2007-01-01

    Unsaturated fatty acids play an essential role in the biophysical characteristics of cell membranes and determine the proper function of membrane-attached proteins. Thus, the ability of cells to alter the degree of unsaturation in their membranes is an important factor in cellular acclimatization to environmental conditions. Many eukaryotic organisms can synthesize dienoic fatty acids, but Saccharomyces cerevisiae can introduce only a single double bond at the Delta(9) position. We expressed two sunflower (Helianthus annuus) oleate Delta(12) desaturases encoded by FAD2-1 and FAD2-3 in yeast cells of the wild-type W303-1A strain (trp1) and analyzed their effects on growth and stress tolerance. Production of the heterologous desaturases increased the content of dienoic fatty acids, especially 18:2Delta(9,12), the unsaturation index, and the fluidity of the yeast membrane. The total fatty acid content remained constant, and the level of monounsaturated fatty acids decreased. Growth at 15 degrees C was reduced in the FAD2 strains, probably due to tryptophan auxotrophy, since the trp1 (TRP1) transformants that produced the sunflower desaturases grew as well as the control strain did. Our results suggest that changes in the fluidity of the lipid bilayer affect tryptophan uptake and/or the correct targeting of tryptophan transporters. The expression of the sunflower desaturases, in either Trp(+) or Trp(-) strains, increased NaCl tolerance. Production of dienoic fatty acids increased the tolerance to freezing of wild-type cells preincubated at 30 degrees C or 15 degrees C. Thus, membrane fluidity is an essential determinant of stress resistance in S. cerevisiae, and engineering of membrane lipids has the potential to be a useful tool of increasing the tolerance to freezing in industrial strains.

  3. Fluidization of Membrane Lipids Enhances the Tolerance of Saccharomyces cerevisiae to Freezing and Salt Stress▿

    PubMed Central

    Rodríguez-Vargas, Sonia; Sánchez-García, Alicia; Martínez-Rivas, Jose Manuel; Prieto, Jose Antonio; Randez-Gil, Francisca

    2007-01-01

    Unsaturated fatty acids play an essential role in the biophysical characteristics of cell membranes and determine the proper function of membrane-attached proteins. Thus, the ability of cells to alter the degree of unsaturation in their membranes is an important factor in cellular acclimatization to environmental conditions. Many eukaryotic organisms can synthesize dienoic fatty acids, but Saccharomyces cerevisiae can introduce only a single double bond at the Δ9 position. We expressed two sunflower (Helianthus annuus) oleate Δ12 desaturases encoded by FAD2-1 and FAD2-3 in yeast cells of the wild-type W303-1A strain (trp1) and analyzed their effects on growth and stress tolerance. Production of the heterologous desaturases increased the content of dienoic fatty acids, especially 18:2Δ9,12, the unsaturation index, and the fluidity of the yeast membrane. The total fatty acid content remained constant, and the level of monounsaturated fatty acids decreased. Growth at 15°C was reduced in the FAD2 strains, probably due to tryptophan auxotrophy, since the trp1 (TRP1) transformants that produced the sunflower desaturases grew as well as the control strain did. Our results suggest that changes in the fluidity of the lipid bilayer affect tryptophan uptake and/or the correct targeting of tryptophan transporters. The expression of the sunflower desaturases, in either Trp+ or Trp− strains, increased NaCl tolerance. Production of dienoic fatty acids increased the tolerance to freezing of wild-type cells preincubated at 30°C or 15°C. Thus, membrane fluidity is an essential determinant of stress resistance in S. cerevisiae, and engineering of membrane lipids has the potential to be a useful tool of increasing the tolerance to freezing in industrial strains. PMID:17071783

  4. Heat-induced aggregation of thylakoid membranes affect their interfacial properties.

    PubMed

    Östbring, Karolina; Rayner, Marilyn; Albertsson, Per-Åke; Erlanson-Albertsson, Charlotte

    2015-04-01

    Many of our most popular lipid containing foods are in emulsion form. These foods are often highly palatable with high caloric density, that subsequently increases the risk of overconsumption and possibly lead to obesity. Regulating the lipid bioavailability of high-fat foods is one approach to prevent overconsumption. Thylakoids, the chloroplast membrane, creates a barrier around lipid droplets, which prolong lipolysis and increase satiety as demonstrated both in animal and human studies. However, a reduced lipase inhibiting capacity has been reported after heat treatment but the mechanism has not yet been fully established. The aim of this study was to investigate thylakoids' emulsifying properties post heat-treatment and possible links to alterations in lipase inhibiting capacity and chlorophyll degradation. Heat-treatment of thylakoids at either 60 °C, 75 °C or 90 °C for time interval ranging from 15 s to 4 min reduced ability to stabilise emulsions, having increased lipid droplets sizes, reduced emulsification capacity, and elevated surface load as consequence. Emulsifying properties were also found to display a linear relationship to both chlorophyll and lipase inhibiting capacity. The correlations support the hypothesis that heat-treatment induce chlorophyll degradation which promote aggregation within proteins inside the thylakoid membrane known to play a decisive role in interfacial processes. Therefore, heat-treatment of thylakoids affects both chlorophyll content, lipase inhibiting capacity and ability to stabilise the oil-water interface. Since the thylakoid's appetite reducing properties are a surface-related phenomenon, the results are useful to optimize the effect of thylakoids as an appetite reducing agent.

  5. An in vitro reconstitution system for the assessment of chromatin protein fluidity during Xenopus development

    SciTech Connect

    Aoki, Ryuta; Inui, Masafumi; Hayashi, Yohei; Sedohara, Ayako; Okabayashi, Koji; Ohnuma, Kiyoshi; Murata, Masayuki; Asashima, Makoto

    2010-09-17

    Research highlights: {yields} An in vitro reconstitution system was established with isolated nuclei and cytoplasm. {yields} Chromatin fluidities were measured in the system using FRAP. {yields} Chromatin fluidities were higher in the cytoplasm of earlier-stage embryos. {yields} Chromatin fluidities were higher in the earlier-stage nuclei with egg-extract. {yields} Chromatin fluidity may decrease during embryonic development. -- Abstract: Chromatin fluidity, which is one of the indicators of higher-order structures in chromatin, is associated with cell differentiation. However, little is known about the relationships between chromatin fluidity and cell differentiation status in embryonic development. We established an in vitro reconstitution system that uses isolated nuclei and cytoplasmic extracts of Xenopus embryos and a fluorescence recovery after photobleaching assay to measure the fluidities of heterochromatin protein 1 (HP1) and histone H1 during development. The HP1 and H1 fluidities of nuclei isolated from the tailbuds of early tadpole stage (stage 32) embryos in the cytoplasmic extracts of eggs and of late blastula stage (stage 9) embryos were higher than those in the cytoplasmic extracts of mid-neurula stage (stage 15) embryos. The HP1 fluidities of nuclei isolated from animal cap cells of early gastrula stage (stage 10) embryos and from the neural plates of neural stage (stage 20) embryos were higher than those isolated from the tailbuds of stage 32 embryos in egg extracts, whereas the HP1 fluidities of these nuclei were the same in the cytoplasmic extracts of stage 15 embryos. These results suggest that chromatin fluidity is dependent upon both cytoplasmic and nuclear factors and decreases during development.

  6. Yeast Integral Membrane Proteins Apq12, Brl1, and Brr6 Form a Complex Important for Regulation of Membrane Homeostasis and Nuclear Pore Complex Biogenesis

    PubMed Central

    Lone, Museer A.; Atkinson, Aaron E.; Hodge, Christine A.; Cottier, Stéphanie; Martínez-Montañés, Fernando; Maithel, Shelley; Mène-Saffrané, Laurent

    2015-01-01

    Proper functioning of intracellular membranes is critical for many cellular processes. A key feature of membranes is their ability to adapt to changes in environmental conditions by adjusting their composition so as to maintain constant biophysical properties, including fluidity and flexibility. Similar changes in the biophysical properties of membranes likely occur when intracellular processes, such as vesicle formation and fusion, require dramatic changes in membrane curvature. Similar modifications must also be made when nuclear pore complexes (NPCs) are constructed within the existing nuclear membrane, as occurs during interphase in all eukaryotes. Here we report on the role of the essential nuclear envelope/endoplasmic reticulum (NE/ER) protein Brl1 in regulating the membrane composition of the NE/ER. We show that Brl1 and two other proteins characterized previously—Brr6, which is closely related to Brl1, and Apq12—function together and are required for lipid homeostasis. All three transmembrane proteins are localized to the NE and can be coprecipitated. As has been shown for mutations affecting Brr6 and Apq12, mutations in Brl1 lead to defects in lipid metabolism, increased sensitivity to drugs that inhibit enzymes involved in lipid synthesis, and strong genetic interactions with mutations affecting lipid metabolism. Mutations affecting Brl1 or Brr6 or the absence of Apq12 leads to hyperfluid membranes, because mutant cells are hypersensitive to agents that increase membrane fluidity. We suggest that the defects in nuclear pore complex biogenesis and mRNA export seen in these mutants are consequences of defects in maintaining the biophysical properties of the NE. PMID:26432634

  7. Two coiled-coil domains of Chlamydia trachomatis IncA affect membrane fusion events during infection.

    PubMed

    Ronzone, Erik; Paumet, Fabienne

    2013-01-01

    Chlamydia trachomatis replicates in a parasitophorous membrane-bound compartment called an inclusion. The inclusions corrupt host vesicle trafficking networks to avoid the degradative endolysosomal pathway but promote fusion with each other in order to sustain higher bacterial loads in a process known as homotypic fusion. The Chlamydia protein IncA (Inclusion protein A) appears to play central roles in both these processes as it participates to homotypic fusion and inhibits endocytic SNARE-mediated membrane fusion. How IncA selectively inhibits or activates membrane fusion remains poorly understood. In this study, we analyzed the spatial and molecular determinants of IncA's fusogenic and inhibitory functions. Using a cell-free membrane fusion assay, we found that inhibition of SNARE-mediated fusion requires IncA to be on the same membrane as the endocytic SNARE proteins. IncA displays two coiled-coil domains showing high homology with SNARE proteins. Domain swap and deletion experiments revealed that although both these domains are capable of independently inhibiting SNARE-mediated fusion, these two coiled-coil domains cooperate in mediating IncA multimerization and homotypic membrane interaction. Our results support the hypothesis that Chlamydia employs SNARE-like virulence factors that positively and negatively affect membrane fusion and promote infection.

  8. Ankyrin and band 3 differentially affect expression of membrane glycoproteins but are not required for erythroblast enucleation

    SciTech Connect

    Ji, Peng; Lodish, Harvey F.

    2012-01-27

    Highlights: Black-Right-Pointing-Pointer Ankyrin and band 3 are not required for erythroblasts enucleation. Black-Right-Pointing-Pointer Loss of ankyrin does not affect erythroid membrane glycoprotein expression. Black-Right-Pointing-Pointer Loss of band 3 influences erythroid membrane glycoprotein expression. -- Abstract: During late stages of mammalian erythropoiesis the nucleus undergoes chromatin condensation, migration to the plasma membrane, and extrusion from the cytoplasm surrounded by a segment of plasma membrane. Since nuclear condensation occurs in all vertebrates, mammalian erythroid membrane and cytoskeleton proteins were implicated as playing important roles in mediating the movement and extrusion of the nucleus. Here we use erythroid ankyrin deficient and band 3 knockout mouse models to show that band 3, but not ankyrin, plays an important role in regulating the level of erythroid cell membrane proteins, as evidenced by decreased cell surface expression of glycophorin A in band 3 knockout mice. However, neither band 3 nor ankyrin are required for enucleation. These results demonstrate that mammalian erythroblast enucleation does not depend on the membrane integrity generated by the ankyrin-band 3 complex.

  9. Fractional polymerization of a suspended planar bilayer creates a fluid, highly stable membrane for ion channel recordings.

    PubMed

    Heitz, Benjamin A; Jones, Ian W; Hall, Henry K; Aspinwall, Craig A; Saavedra, S Scott

    2010-05-26

    Suspended planar lipid membranes (or black lipid membranes (BLMs)) are widely used for studying reconstituted ion channels, although they lack the chemical and mechanical stability needed for incorporation into high-throughput biosensors and biochips. Lipid polymerization enhances BLM stability but is incompatible with ion channel function when membrane fluidity is required. Here, we demonstrate the preparation of a highly stable BLM that retains significant fluidity by using a mixture of polymerizable and nonpolymerizable phospholipids. Alamethicin, a voltage-gated peptide channel for which membrane fluidity is required for activity, was reconstituted into mixed BLMs prepared using bis-dienoyl phosphatidylcholine (bis-DenPC) and diphytanoyl phosphatidylcholine (DPhPC). Polymerization yielded BLMs that retain the fluidity required for alamethicin activity yet are stable for several days as compared to a few hours prior to polymerization. Thus, these polymerized, binary composition BLMs feature both fluidity and long-term stability.

  10. Fractional Polymerization of a Suspended Planar Bilayer Creates a Fluid, Highly Stable Membrane for Ion Channel Recordings

    PubMed Central

    Heitz, Benjamin A.; Jones, Ian W.; Hall, Henry K.; Aspinwall, Craig A.; Saavedra, S. Scott

    2010-01-01

    Suspended planar lipid membranes (or black lipid membranes (BLMs)) are widely used for studying reconstituted ion channels, although they lack the chemical and mechanical stability needed for incorporation into high-throughput biosensors and biochips. Lipid polymerization enhances BLM stability but is incompatible with ion channel function when membrane fluidity is required. Here we demonstrate the preparation of a highly stable BLM that retains significant fluidity by using a mixture of polymerizable and nonpolymerizable phospholipids. Alamethicin, a voltage-gated peptide channel for which membrane fluidity is required for activity, was reconstituted into mixed BLMs prepared using bis-dienoyl phosphatidylcholine (bis-DenPC) and diphytanoyl phosphatidylcholine (DPhPC)). Polymerization yielded BLMs that retain the fluidity required for alamethicin activity yet are stable for several days as compared to a few hours prior to polymerization. Thus these polymerized, binary composition BLMs feature both fluidity and long-term stability. PMID:20441163

  11. Sewage sludge treatment in a thermophilic membrane reactor (TMR): factors affecting foam formation.

    PubMed

    Collivignarelli, Maria Cristina; Castagnola, Federico; Sordi, Marco; Bertanza, Giorgio

    2016-11-04

    Foam formation in the excess sludge treatment facilities of biological wastewater treatment plants (WWTPs) may represent a critical issue as it could lead to several operative problems and reduce the overall plant performance. This trouble also affects a novel technology recently proposed for sludge minimization, the thermophilic membrane reactor (TMR), operating with alternate aeration/non-aeration cycles. This technology, which has proven to be extremely resilient and suitable for treating industrial wastewater of different nature, demonstrated a high potential also as a solution for integrating existing WWTPs, aiming at the "zero sludge production." In this work, an experimental study was conducted with a TMR pilot plant (fed daily with thickened sewage sludge) by adjusting the duration of aeration/non-aeration alternate cycles. Extracellular polymeric substance (EPS) concentration (and its soluble and bound fractions) has been monitored along with foaming power indices. The results highlight that foaming can be correlated to the presence of soluble protein fraction of EPS. Moreover, EPS production seems to be reduced by increasing the duration of the non-aeration cycles: optimal operating conditions resulted 2 h of aeration followed by 6 h of non-aeration. These conditions allow to obtain an EPS concentration of 500 mg L(-1) with respect to 2300 mg L(-1) measured at the beginning of experimental work.

  12. LRRK2 Affects Vesicle Trafficking, Neurotransmitter Extracellular Level and Membrane Receptor Localization

    PubMed Central

    Spissu, Ylenia; Sanna, Giovanna; Xiong, Yulan; Dawson, Ted M.; Dawson, Valina L.; Galioto, Manuela; Rocchitta, Gaia; Biosa, Alice; Serra, Pier Andrea; Carri, Maria Teresa; Crosio, Claudia; Iaccarino, Ciro

    2013-01-01

    The leucine-rich repeat kinase 2 (LRRK2) gene was found to play a role in the pathogenesis of both familial and sporadic Parkinson’s disease (PD). LRRK2 encodes a large multi-domain protein that is expressed in different tissues. To date, the physiological and pathological functions of LRRK2 are not clearly defined. In this study we have explored the role of LRRK2 in controlling vesicle trafficking in different cellular or animal models and using various readouts. In neuronal cells, the presence of LRRK2G2019S pathological mutant determines increased extracellular dopamine levels either under basal conditions or upon nicotine stimulation. Moreover, mutant LRRK2 affects the levels of dopamine receptor D1 on the membrane surface in neuronal cells or animal models. Ultrastructural analysis of PC12-derived cells expressing mutant LRRK2G2019S shows an altered intracellular vesicle distribution. Taken together, our results point to the key role of LRRK2 to control vesicle trafficking in neuronal cells. PMID:24167564

  13. Temperature-mediated variations in cellular membrane fatty acid composition of Staphylococcus aureus in resistance to pulsed electric fields.

    PubMed

    Wang, Lang-Hong; Wang, Man-Sheng; Zeng, Xin-An; Liu, Zhi-Wei

    2016-08-01

    Effects of growth temperature on cell membrane fatty acid composition, fluidity and lethal and sublethal injury by pulsed electric fields (PEF) in Staphylococcus aureus ATCC 43300 (S. aureus) in the stationary phase were investigated. Analysis of the membrane fatty acids by gas chromatography-mass spectrometry (GC-MS) revealed that branched chain fatty acids (iso C14:0, iso C15:0, anteiso C15:0 and anteiso C17:0) and straight chain fatty acids (C12:0, C14:0, C16:0, C17:0 and C18:0) were primary constituents in the membrane. The S. aureus changed its membrane fatty acid composition and its overall fluidity when exposed to different temperatures. The PEF lethal and sublethal effects were assessed, and results suggested that the degree of inactivation depended on the cell membrane structure, electric field strength and treatment time. The PEF inactivation kinetics including lethal and sublethal injury fractions were fitted with non-linear Weibull distribution, suggesting that inactivation of the first log cycle of S. aureus population was significantly affected by growth temperature, and the membrane of cells became more fluid, and easier to induce electroportion in low temperatures. Moreover, the morphology of S. aureus cells were investigated by electron microscopy, showing that various temperature-modified cells were distorted to differing extents and some even collapsed due to deep irreversible electroporation after PEF treatment.

  14. Common α2A and α2C adrenergic receptor polymorphisms do not affect plasma membrane trafficking.

    PubMed

    Hurt, Carl M; Sorensen, Matt W; Angelotti, Timothy

    2014-06-01

    Various naturally occurring polymorphic forms of human G protein-coupled receptors (GPCRs) have been identified and linked to diverse pathological diseases, including receptors for vasopressin type 2 (nephrogenic diabetes insipidus) and gonadotropin releasing hormone (hypogonadotropic hypogonadism). In most cases, polymorphic amino acid mutations disrupt protein folding, altering receptor function as well as plasma membrane expression. Other pathological GPCR variants have been found that do not alter receptor function, but instead affect only plasma membrane trafficking (e.g., delta opiate and histamine type 1 receptors). Thus, altered membrane trafficking with retained receptor function may be another mechanism causing polymorphic GPCR dysfunction. Two common human α2A and α2C adrenergic receptor (AR) variants have been identified (α2A N251K and α2C Δ322-325 ARs), but pharmacological analysis of ligand binding and second messenger signaling has not consistently demonstrated altered receptor function. However, possible alterations in plasma membrane trafficking have not been investigated. We utilized a systematic approach previously developed for the study of GPCR trafficking motifs and accessory proteins to assess whether these α2 AR variants affected intracellular trafficking or plasma membrane expression. By combining immunofluorescent microscopy, glycosidic processing analysis, and quantitative fluorescent-activated cell sorting (FACS), we demonstrate that neither variant receptor had altered intracellular localization, glycosylation, nor plasma membrane expression compared to wild-type α2 ARs. Therefore, pathopharmacological properties of α2A N251K and α2C Δ322-325 ARs do not appear to be due to altered receptor pharmacology or plasma membrane trafficking, but may involve interactions with other intracellular signaling cascades or proteins.

  15. How does γ-irradiation affect the properties of a microfiltration membrane constituted of two polymers with different radiolytic behavior?

    NASA Astrophysics Data System (ADS)

    Fortin, Nicolas; Albela, Belén; Bonneviot, Laurent; Rouif, Sophie; Sanchez, Jean-Yves; Portinha, Daniel; Fleury, Etienne

    2012-03-01

    The objective of this work is to present the behavior of a fluorinated microporous membrane composed of poly(vinylidene fluoride) (PVDF) mechanically reinforced by a polyamide-66 (PA-66) fabric under γ-irradiation with dose ranging between 0 and 100 kGy, in inert atmosphere and at room temperature. Particular attention was paid to the evolution of mechanical properties, the surface morphology and pores size distribution of this membrane, in order to study the filtration capacity and selectivity with increasing radiation dose. Moreover, the repartition of the generated radicals onto the two components of the membrane was achieved by electron spin resonance (ESR) spectroscopy. Two different regimes are observed depending on the dose range, and a correlation between the mechanical behavior of the membrane and the evolution of the concentration of the radicals in the PA fabric is observed. Globally, the porosity of the surface membrane does not vary whatever the dose may be, but the mechanical properties of the membrane as well as the permeability are strongly affected, even for low radiation dose such as 10 kGy. These results are related to chain scissions on the PA fabric, which occurred preferentially, compared to cross-linking, in the investigated dose range.

  16. Correlation between structure and fluidity of coal tar pitch fractions studied by ambient {sup 13}C and high temperature in-situ {sup 1}H nuclear magnetic resonance

    SciTech Connect

    Andresen, J.M.; Schober, H.H.; Rusinko, F.J. Jr.

    1999-07-01

    The unique properties of coal tar pitches have resulted in numerous applications for carbon products, such as binders for carbon artifacts. However, as the number of by-product coke ovens is diminishing, the design of superior binders from alternative materials or processes is sought by the carbon industry. Accordingly, structural characterization of coal tar pitches and their solvent fractions, using quantitative analytical techniques is required to successfully obtain this goal. Quantitative solid state {sup 13}C NMR has previously been shown to be a powerful technique to study the overall aromatic ring-size for coal tar pitches and their toluene insoluble (TI) fractions. The TI fraction can further be separated into its quinoline soluble part (beta-resin) and insoluble fraction (QI). Both these fractions affect the overall coking yield and especially the fluidity of the pitches. The assessment of fluidity interactions between coal tar pitch solvent fractions during heating is therefore important for the future design of pitches from untraditional sources or processes. High temperature {sup 1}H NMR is a useful technique to investigate the fluid and rigid components of pitches, especially with its interaction with coal and to quantify mesophase. However, very little work has been performed to correlate the overall fluidity behavior of pitch with the mobility of its different solubility fractions and their structure. Accordingly, this paper addresses the fluidity interactions between different pitch solvent fractions (TS, beta-resin and QI) by high temperature {sup 1}H NMR. Particularly, the fluidity studies on the beta-resin alone can verify whether this fraction becomes plastic during heating.

  17. Launch Conditions Might Affect the Formation of Blood Vessel in the Quail Chorioallantoic Membrane

    NASA Technical Reports Server (NTRS)

    Henry, M. K.; Unsworth, B. R.; Sychev, B. R.; Guryeva, T. S.; Dadasheva, O. A.; Piert, S. J.; Lagel, K. E.; Dubrovin, L. C.; Jahns, G. C.; Boda, K.; Sabo, V.; Samet, M. M.; Lelkes, P. I.

    1998-01-01

    AS 2 part of the first joint USA-Russian MIR/Shuttle program, fertilized quail eggs were flown on the MIR 18 mission. Post-flight examination indicated impaired survival of both the embryos in space and also of control embryos exposed to vibrational and g-forces simulating the conditions experienced during the launch of Progress 227. We hypothesized that excess mechanical forces and/or other conditions during the launch might cause abnormal development of the blood supply in the chorioallantoic membrane (CAM) leading to the impaired survival of the embryos. The CAM, a highly vascularized extraembryonic organ, provides for the oxygen exchange across the egg shell and is thus pivotal for proper embryonic development. To test our hypothesis, we compared angiogenesis In CAMS of eggs which were either exposed to the vibration and g-force profile simulating the conditions at launch of Progress 227 (synchronous controls), or kept under routine conditions in a laboratory Incubator (laboratory controls). At various time points during Incubation, the eggs were fixed in paraformaldehyde for subsequent dissection. At the time of dissection, the CAM was carefully lifted from the egg shell and examined as whole mounts by bright-field and fluorescent microscopy. The development or the vasculature (angiogenesis) was assessed from the density of blood vessels per viewing field and evaluated by computer aided image analysis. We observed a significant decrease In blood-vessel density in the synchronous controls versus "normal" laboratory controls beginning from day 10 of Incubation. The decrease in vascular density was restricted to the smallest vessels only, suggesting that conditions during the launch and/or during the subsequent Incubation of the eggs may affect the normal progress of angiogenesis in the CAM. Abnormal angiogenesis In the CAM might contribute to the impaired survival of the embryos observed in synchronous controls as well as in space.

  18. Factors affecting seasonal variation of membrane filtration resistance caused by Chlorella algae.

    PubMed

    Babel, Sandhya; Takizawa, Satoshi; Ozaki, Hiroaki

    2002-03-01

    A seasonal fluctuation pattern was observed in membrane filtration resistance by Chlorella algae cultured in open ponds in the tropical environment. In order to investigate the causes of this phenomenon, Chlorella was cultivated under controlled conditions and the cake resistance was measured by batch filtration in dead-end mode. The filtration resistance was found to be a function of environmental conditions. Algae could grow favourably and offered low specific cake resistance (R,s) on the order of 10(11) m/g for the culture temperature from 28 degrees C to 35 degrees C. The algal growth was inhibited and the specific cake resistance increased to the order of 10(12) m/g below or above this optimum temperature range. Strong solar radiation, coupled with high temperatures, also inhibited the growth of algae and resulted in higher specific cake resistance. The specific cake resistance of algae cultured at different temperatures increased with the amount of the extracellular organic matter (EOM) extracted by 0.1 N NaOH. Hence EOM, rather than bacteria present in the mono-algal culture, was considered to be the primary factor affecting the cake resistance. The specific cake resistance increased drastically after actively growing cells were stored in nutrient-free water under dark conditions. However, the resistance was slightly decreased when the algal cells were stored in NSIII nutrient media in a dark room, indicating the effect of nutrient availability on the change of the specific cake resistance under the light-limiting conditions. EOM extracted from the cells kept in the nutrient-free water contained less sugar than the fresh culture, whereas the EOM extracted from the cells stored in the NSIII media contained more sugar. The molecular distribution of the EOM shifted from below 1,000 kDa before storage to more than 2,000 kDa after storage in both the nutrient-free and NSIII media.

  19. Potential electrostatic interactions in multiple regions affect human metapneumovirus F-mediated membrane fusion.

    PubMed

    Chang, Andres; Hackett, Brent A; Winter, Christine C; Buchholz, Ursula J; Dutch, Rebecca Ellis

    2012-09-01

    The recently identified human metapneumovirus (HMPV) is a worldwide respiratory virus affecting all age groups and causing pneumonia and bronchiolitis in severe cases. Despite its clinical significance, no specific antiviral agents have been approved for treatment of HMPV infection. Unlike the case for most paramyxoviruses, the fusion proteins (F) of a number of strains, including the clinical isolate CAN97-83, can be triggered by low pH. We recently reported that residue H435 in the HRB linker domain acts as a pH sensor for HMPV CAN97-83 F, likely through electrostatic repulsion forces between a protonated H435 and its surrounding basic residues, K295, R396, and K438, at low pH. Through site-directed mutagenesis, we demonstrated that a positive charge at position 435 is required but not sufficient for F-mediated membrane fusion. Arginine or lysine substitution at position 435 resulted in a hyperfusogenic F protein, while replacement with aspartate or glutamate abolished fusion activity. Studies with recombinant viruses carrying mutations in this region confirmed its importance. Furthermore, a second region within the F(2) domain identified as being rich in charged residues was found to modulate fusion activity of HMPV F. Loss of charge at residues E51, D54, and E56 altered local folding and overall stability of the F protein, with dramatic consequences for fusion activity. As a whole, these studies implicate charged residues and potential electrostatic interactions in function, pH sensing, and overall stability of HMPV F.

  20. Rigidity and Fluidity in Living and Nonliving Matter

    NASA Astrophysics Data System (ADS)

    Lopez, Jorge H.

    complicated problem of jamming, we will gain insight into which constraints affect the nature of the jamming transition and which do not. We find that k = 3-core percolation on the hyperbolic lattice remains a continuous phase transition despite the fact that the loop structure of hyperbolic lattices is different from Euclidean lattices. We also contribute towards numerical techniques for analyzing percolation on hyperbolic lattices. In Chapters 4 and 5 we turn to living matter, which is also nonequilibrium in a very local way in that each constituent has its own internal energy supply. In Chapter 4 we study the fluidity of a cell moving through a confluent tissue, i.e. a group of cells with no gaps between them, via T1 transitions. A T1 transition allows for an edge swap so that a cell can come into contact with new neighbors. Cell migration is then generated by a sequence of such swaps. In a simple four cell system we compute the energy barriers associated with this transition. We then find that the energy barriers in a larger system are rather similar to the four cell case. The many cell case, however, more easily allows for the collection of statistics of these energy barriers given the disordered packings of cell observed in experiments. We find that the energy barriers are exponentially distributed. Such a finding implies that glassy dynamics is possible in a confluent tissue. Finally, in chapter 5 we turn to single cell migration in the extracellular matrix, another native environment of a cell. Experiments suggest that the migration of some cells in the three-dimensional extra cellular matrix bears strong resemblance to one-dimensional cell migration. Motivated by this observation, we construct and study a minimal one-dimensional model cell made of two beads and an active spring moving along a rigid track. The active spring models the stress fibers with their myosin-driven contractility and alpha-actinin-driven extendability, while the friction coefficients of the two

  1. Calcium influx affects intracellular transport and membrane repair following nanosecond pulsed electric field exposure

    NASA Astrophysics Data System (ADS)

    Thompson, Gary Lee; Roth, Caleb C.; Dalzell, Danielle R.; Kuipers, Marjorie; Ibey, Bennett L.

    2014-05-01

    The cellular response to subtle membrane damage following exposure to nanosecond pulsed electric fields (nsPEF) is not well understood. Recent work has shown that when cells are exposed to nsPEF, ion permeable nanopores (<2 nm) are created in the plasma membrane in contrast to larger diameter pores (>2 nm) created by longer micro- and millisecond duration pulses. Nanoporation of the plasma membrane by nsPEF has been shown to cause a transient increase in intracellular calcium concentration within milliseconds after exposure. Our research objective is to determine the impact of nsPEF on calcium-dependent structural and repair systems in mammalian cells. Chinese hamster ovary (CHO-K1) cells were exposed in the presence and absence of calcium ions in the outside buffer to either 1 or 20, 600-ns duration electrical pulses at 16.2 kV/cm, and pore size was determined using propidium iodide and calcium green. Membrane organization was observed with morphological changes and increases in FM1-43 fluorescence. Migration of lysosomes, implicated in membrane repair, was followed using confocal microscopy of red fluorescent protein-tagged LAMP1. Microtubule structure was imaged using mEmerald-tubulin. We found that at high 600-ns PEF dosage, calcium-induced membrane restructuring and microtubule depolymerization coincide with interruption of membrane repair via lysosomal exocytosis.

  2. Calcium influx affects intracellular transport and membrane repair following nanosecond pulsed electric field exposure.

    PubMed

    Thompson, Gary Lee; Roth, Caleb C; Dalzell, Danielle R; Kuipers, Marjorie; Ibey, Bennett L

    2014-05-01

    The cellular response to subtle membrane damage following exposure to nanosecond pulsed electric fields (nsPEF) is not well understood. Recent work has shown that when cells are exposed to nsPEF, ion permeable nanopores (<2  nm) are created in the plasma membrane in contrast to larger diameter pores (>2  nm) created by longer micro- and millisecond duration pulses. Nanoporation of the plasma membrane by nsPEF has been shown to cause a transient increase in intracellular calcium concentration within milliseconds after exposure. Our research objective is to determine the impact of nsPEF on calcium-dependent structural and repair systems in mammalian cells. Chinese hamster ovary (CHO-K1) cells were exposed in the presence and absence of calcium ions in the outside buffer to either 1 or 20, 600-ns duration electrical pulses at 16.2  kV/cm, and pore size was determined using propidium iodide and calcium green. Membrane organization was observed with morphological changes and increases in FM1-43 fluorescence. Migration of lysosomes, implicated in membrane repair, was followed using confocal microscopy of red fluorescent protein-tagged LAMP1. Microtubule structure was imaged using mEmerald-tubulin. We found that at high 600-ns PEF dosage, calcium-induced membrane restructuring and microtubule depolymerization coincide with interruption of membrane repair via lysosomal exocytosis.

  3. Effect of 8-alkylberberine homologues on erythrocyte membrane.

    PubMed

    Yong, Yang; Ye, Xiao-Li; Zhang, Bao-Shun; Li, Xue-Gang

    2011-05-01

    8-alkylberberine homologues (Ber-C8-n, where n indicates carbon atom number of gaseous normal alkyl at 8 position, n = 0, 2, 4, 6, 8, 10, 12, or 16) were synthesized and their effects on the hemolysis of rabbit erythrocyte, the fluidity of membrane and the fluorescence of membrane protein were investigated by fluorescence analysis technique. Ber-C8-n with mediate length alkyl (4 < n < 10) exhibited obvious hemolysis effect on rabbit erythrocyte when their concentration exceed 1.25 x10(-4) mol/L, and Ber-C8-8 displayed the highest hemolysis effect among all tested homologues. All of Ber-C8-n influenced the fluidity of erythrocyte membrane to different extents, which exhibited an obvious dose-effect relationship. The effect of Ber-C8-n on fluidity increased as the length of alkyl chain was elongated and decreased gradually when the alkyl carbon atoms exceeded 8. The fluorescence of erythrocyte membrane protein was quenched by Ber-C8-n, which showed a similar changing tendency on membrane fluidity. Experiments in vitro suggested that disturbing effects of Ber-C8-n on the conformation and function of membrane protein leaded to the changes of membrane fluidity and stability, and then the membrane was broken down.

  4. Altered membrane lipid composition and functional parameters of circulating cells in cockles (Cerastoderma edule) affected by disseminated neoplasia.

    PubMed

    Le Grand, Fabienne; Soudant, Philippe; Marty, Yanic; Le Goïc, Nelly; Kraffe, Edouard

    2013-01-01

    Membrane lipid composition and morpho-functional parameters were investigated in circulating cells of the edible cockle (Cerastoderma edule) affected by disseminated neoplasia (neoplastic cells) and compared to those from healthy cockles (hemocytes). Membrane sterol levels, phospholipid (PL) class and subclass proportions and their respective fatty acid (FA) compositions were determined. Morpho-functional parameters were evaluated through total hemocyte count (THC), mortality rate, phagocytosis ability and reactive oxygen species (ROS) production. Both morpho-functional parameters and lipid composition were profoundly affected in neoplastic cells. These dedifferentiated cells displayed higher THC (5×), mortality rate (3×) and ROS production with addition of carbonyl cyanide m-chloro phenylhydrazone (1.7×) but lower phagocytosis ability (½×), than unaffected hemocytes. Total PL amounts were higher in neoplastic cells than in hemocytes (12.3 and 5.1 nmol×10(-6) cells, respectively). However, sterols and a particular subclass of PL (plasmalogens; 1-alkenyl-2-acyl PL) were present in similar amounts in both cell type membranes. This led to a two times lower proportion of these membrane lipid constituents in neoplastic cells when compared to hemocytes (20.5% vs. 42.1% of sterols in total membrane lipids and 21.7% vs. 44.2% of plasmalogens among total PL, respectively). Proportions of non-methylene interrupted FA- and 20:1n-11-plasmalogen molecular species were the most impacted in neoplastic cells when compared to hemocytes (⅓× and ¼×, respectively). These changes in response to this leukemia-like disease in bivalves highlight the specific imbalance of plasmalogens and sterols in neoplastic cells, in comparison to the greater stability of other membrane lipid components.

  5. In vivo collective cell migration requires an LPAR2-dependent increase in tissue fluidity

    PubMed Central

    Kuriyama, Sei; Theveneau, Eric; Benedetto, Alexandre; Parsons, Maddy; Tanaka, Masamitsu; Charras, Guillaume; Kabla, Alexandre

    2014-01-01

    Collective cell migration (CCM) and epithelial–mesenchymal transition (EMT) are common to cancer and morphogenesis, and are often considered to be mutually exclusive in spite of the fact that many cancer and embryonic cells that have gone through EMT still cooperate to migrate collectively. Here we use neural crest (NC) cells to address the question of how cells that have down-regulated cell–cell adhesions can migrate collectively. NC cell dissociation relies on a qualitative and quantitative change of the cadherin repertoire. We found that the level of cell–cell adhesion is precisely regulated by internalization of N-cadherin downstream of lysophosphatidic acid (LPA) receptor 2. Rather than promoting the generation of single, fully mesenchymal cells, this reduction of membrane N-cadherin only triggers a partial mesenchymal phenotype. This intermediate phenotype is characterized by an increase in tissue fluidity akin to a solid-like–to–fluid-like transition. This change of plasticity allows cells to migrate under physical constraints without abolishing cell cooperation required for collectiveness. PMID:25002680

  6. Acute intrastriatal administration of quinolinic acid affects the expression of the coat protein AP-2 and its interaction with membranes.

    PubMed

    Borgonovo, Janina; Seltzer, Alicia; Sosa, Miguel Angel

    2009-10-01

    Clathrin-coated vesicle endocytosis is thought to be crucial for the maintenance of synaptic transmission and for the cell plasticity at the nervous system. In this study, we demonstrated that acute intrastriatal administration of quinolinic acid (QUIN), an agonist of the N-methyl-D: -aspartate receptor, induces a decrease of the coat protein AP-2 expression and affects their interaction with membranes. By western blot analysis we observed that at 24 h after QUIN intrastriatal injection, alpha1 subunit of AP-2 and alpha2, at lesser extent, were reduced in the striatal membranes. The decrease of both subunits expression was extended to 48 h after treatment, although the soluble proteins were mostly affected. Other areas of the brain were not affected by the treatment, except the cerebellum, where a significant increase of soluble AP-2 (both subunits) was observed at 48 h after injection. Another coat protein, as the phosphoprotein AP-180, was not affected by the injection of QUIN. We also confirmed that QUIN injection causes increasing loss of striatal neurons after the administration of the toxin. We concluded that QUIN may affect the endocytotic machinery of the striatum, by inducing changes in the AP-2 behaviour. Consequently, the internalization of NMDAR and/or AMPAR may be affected, by QUIN, contributing to the excitotoxic effect of the drug.

  7. Treatment of oil sands process-affected water (OSPW) using a membrane bioreactor with a submerged flat-sheet ceramic microfiltration membrane.

    PubMed

    Xue, Jinkai; Zhang, Yanyan; Liu, Yang; Gamal El-Din, Mohamed

    2016-01-01

    The release of oil sands process-affected water (OSPW) into the environment is a concern because it contains persistent organic pollutants that are toxic to aquatic life. A modified Ludzack-Ettinger membrane bioreactor (MLE-MBR) with a submerged ceramic membrane was continuously operated for 425 days to evaluate its feasibility on OSPW treatment. A stabilized biomass concentration of 3730 mg mixed liquor volatile suspended solids per litre and a naphthenic acid (NA) removal of 24.7% were observed in the reactor after 361 days of operation. Ultra Performance Liquid Chromatography/High Resolution Mass Spectrometry analysis revealed that the removal of individual NA species declined with increased ring numbers. Pyrosequencing analysis revealed that Betaproteobacteria were dominant in sludge samples from the MLE-MBR, with microorganisms such as Rhodocyclales and Sphingobacteriales capable of degrading hydrocarbon and aromatic compounds. During 425 days of continuous operation, no severe membrane fouling was observed as the transmembrane pressure (TMP) of the MLE-MBR never exceeded -20 kPa given that the manufacturer's suggested critical TMP for chemical cleaning is -35 kPa. Our results indicated that the proposed MLE-MBR has a good potential for removing recalcitrant organics in OSPW.

  8. Comparative study of metal induced phospholipid modifications in the heavy metal tolerant filamentous fungus Paecilomyces marquandii and implications for the fungal membrane integrity.

    PubMed

    Słaba, Mirosława; Bernat, Przemysław; Różalska, Sylwia; Nykiel, Justyna; Długoński, Jerzy

    2013-01-01

    In this work we compared the effect of five heavy metals: Zn, Pb, Cd, Ni and Cu on phospholipid composition of the ubiquitous soil fungus Paecilomyces marquandii, originating from a strongly metal polluted area and characterized by high tolerance to these elements. Cd, Ni and Cu caused an increase in phosphatidylcholine (PC). Only Pb decreased PC content, which was accompanied by a significant rise in the phosphatidic acids (PA) level, probably due to activation of phospholipase D which hydrolyzes PC to PA. This could result in membrane fluidity disturbance, and thus affect its integrity. The assessment of propidium iodide influx showed strong disturbance of membrane integrity for Cu and Pb stressed mycelia, whereas mycelia treated with Ni were impermeable to this dye. The results obtained revealed a strong Cu and Pb toxicity involving disruption of membrane integrity. Pb action was reflected by lipid composition, whereas changes in Cu treated mycelia did not completely elucidate its harmful effect on the membrane, which was most probably caused by Cu induced lipid peroxidation. Zn did not induce quantitative changes in PC and phosphatidylethanolamine (PE) but caused changes in phospholipid lipid saturation, which appears to be important for fungus adaptation to the presence of metals. The enhanced PC content balanced by higher PC saturation can help in the maintenance of proper membrane fluidity and result in alleviating the Cd and Ni induced stress. These results will allow to clarify the mechanism of Pb toxicity and help to elucidate the cellular basis of fungal membrane adaptation to heavy metals.

  9. Factors affecting alcohol-water pervaporation performance of hydrophobic zeolite-silicone rubber mixed matrix membranes

    EPA Science Inventory

    Mixed matrix membranes (MMMs) consisting of ZSM-5 zeolite particles dispersed in silicone rubber exhibited ethanol-water pervaporation permselectivities up to 5 times that of silicone rubber alone and 3 times higher than simple vapor-liquid equilibrium (VLE). A number of conditi...

  10. Sexual Fluidity and Related Attitudes and Beliefs Among Young Adults with a Same-Gender Orientation.

    PubMed

    Katz-Wise, Sabra L; Hyde, Janet S

    2015-07-01

    Little research has examined whether experiencing sexual fluidity--changes over time in attractions and sexual orientation identity--is related to specific cognitions. This study explored attitudes and beliefs among sexually fluid and non-sexually fluid individuals and developed two new measures of sexuality beliefs based on Diamond's sexual fluidity research and Dweck's psychological theory of intelligence beliefs. Participants were 188 female and male young adults in the United States with a same-gender orientation, ages 18-26 years. Participants completed an online questionnaire which assessed sexual fluidity in attractions and sexual orientation identity, attitudes toward bisexuality, sexuality beliefs, and demographics. Sexual fluidity in attractions was reported by 63 % of females and 50 % of males, with 48 % of those females and 34 % of those males reporting fluidity in sexual orientation identity. No significant gender differences in frequency of sexual fluidity were observed. Sexually fluid females had more positive attitudes toward bisexuality than non-sexually fluid females; however, no significant difference was observed for males. Females were more likely than males to endorse sexual fluidity beliefs and to believe that sexuality is changeable; and sexually fluid persons were more likely than non-sexually fluid persons to hold those two beliefs. Among males, non-sexually fluid individuals were more likely than sexually fluid individuals to believe that sexuality is something an individual is born with. Females were more likely than males to endorse the belief that sexuality is influenced by the environment. Findings from this research link sexual fluidity with specific cognitions.

  11. Laurdan monitors different lipids content in eukaryotic membrane during embryonic neural development

    PubMed Central

    Bonaventura, Gabriele; Barcellona, Maria Luisa; Golfetto, Ottavia; Nourse, Jamison L.; Flanagan, Lisa A.; Gratton, Enrico

    2014-01-01

    We describe a method based on fluorescence lifetime imaging microscopy (FLIM) to assess the fluidity of various membranes in neuronal cells at different stage of development (day 12 (E12) and day 16 (E16) of gestation). For the FLIM measurements, we use the Laurdan probe which is commonly used to asses membrane water penetration in model and in biological membranes using spectral information. Using the FLIM approach we build a fluidity scale based on calibration with model systems of different lipid composition. In neuronal cells we found a marked difference in fluidity between the internal membranes and the plasma membrane, being the plasma membrane the less fluid. However, we found no significant differences between the two cells groups, E12 and E16. Comparison with NIH3T3 cells show that the plasma membranes of E12 and E16 cells are significantly more fluid than the plasma membrane of the cancer cells. PMID:24839062

  12. Voltage- and Tension-Dependent Lipid Mobility in the Outer Hair Cell Plasma Membrane

    NASA Astrophysics Data System (ADS)

    Oghalai, John S.; Zhao, Hong-Bo; Kutz, J. Walter; Brownell, William E.

    2000-01-01

    The mechanism responsible for electromotility of outer hair cells in the ear is unknown but is thought to reside within the plasma membrane. Lipid lateral diffusion in the outer hair cell plasma membrane is a sigmoidal function of transmembrane potential and bathing media osmolality. Cell depolarization or hyposmotic challenge shorten the cell and reduce membrane fluidity by half. Changing the membrane tension with amphipathic drugs results in similar reductions. These dynamic changes in membrane fluidity represent the modulation of membrane tension by lipid-protein interactions. The voltage dependence may be associated with the force-generating motors that contribute to the exquisite sensitivity of mammalian hearing.

  13. Describing Temperature-Dependent Self-Diffusion Coefficients and Fluidity of 1- and 3-Alcohols with the Compensated Arrhenius Formalism.

    PubMed

    Fleshman, Allison M; Forsythe, Grant E; Petrowsky, Matt; Frech, Roger

    2016-09-22

    The location of the hydroxyl group in monohydroxy alcohols greatly affects the temperature dependence of the liquid structure due to hydrogen bonding. Temperature-dependent self-diffusion coefficients, fluidity (the inverse of viscosity), dielectric constant, and density have been measured for several 1-alcohols and 3-alcohols with varying alkyl chain lengths. The data are modeled using the compensated Arrhenius formalism (CAF). The CAF follows a modified transition state theory using an Arrhenius-like expression to describe the transport property, which consists of a Boltzmann factor containing an energy of activation, Ea, and an exponential prefactor containing the temperature-dependent solution dielectric constant, εs(T). Both 1- and 3-alcohols show the Ea of diffusion coefficients (approximately 43 kJ mol(-1)) is higher than the Ea of fluidity (approximately 35 kJ mol(-1)). The temperature dependence of the exponential prefactor in these associated liquids is explained using the dielectric constant and the Kirkwood-Frölich correlation factor, gk. It is argued that the dielectric constant must be used to account for the additional temperature dependence due to variations in the liquid structure (e.g., hydrogen bonding) for the CAF to accurately model the transport property.

  14. Physical properties, lipid composition and enzyme activities of hepatic subcellular membranes from chick embryo after ethanol treatment

    SciTech Connect

    Sanchez-Amate, M.C.; Marco, C.; Segovia, J.L. )

    1992-01-01

    Exposure of chick embryos to ethanol resulted in significant alterations to the lipid composition of various different hepatic subcellular membranes. A marked decrease in cholesterol levels and an increase in the phospholipid content of microsomes and mitochondria was observed. Ethanol also affected the fatty acid profiles, mainly by decreasing the percentage of oleic acid in phosphatidylcholine and phosphatidylethanolamine in the mitochondria and phosphatidylethanolamine in the microsomes. In spite of these changes ethanol only induced alterations in the fluidity of the mitochondrial membranes, which showed a more rigid core, in contrast to the phospholipid-head region, which was not affected. In accordance with the changes observed in the physical state of the membrane, the enzymes involved in the microsomal electron-transport systems were not modified by ethanol, while cytochrome oxidase activity decreased by 50% compared to the activity in the mitochondria from control chick embryos.

  15. How do the full-generation poly(amido)amine (PAMAM) dendrimers activate blood platelets? Platelet membrane zeta potential and other membrane-associated phenomena.

    PubMed

    Watala, Cezary; Karolczak, Kamil; Kassassir, Hassan; Siewiera, Karolina; Maczynska, Katarzyna; Pieniazek, Anna; Labieniec-Watala, Magdalena

    2016-03-16

    We explored the hypothesis that zeta potential altered by polycations affects blood platelet activation and reactivity, the phenomena associated with membrane lipid fluidity and platelet mitochondrial bioenergetics. PAMAM dendrimers generation- and dose-dependently enhanced zeta potential of platelets (from -10.7 mV to -4.3 mV). Increased expressions of activation markers, P-selectin and the active complex αIIbβ3, as well as significantly enhanced fibrinogen binding occurred upon the in vitro incubation of blood platelets in the presence of PAMAMs G3 and G4 (resp. 62.1% and 69.4% vs. 1.4% and 2.7% in control for P-selectin, P<0.0001). PAMAM dendrimers increased fluidity of platelet membrane lipid bilayer, while they did not affect platelet mitochondria respiration. Increased platelet activation and their responses to agonists in vitro were statistically associated with the revealed alterations in zeta potential. Our results support the hypothesis that polycation-mediated "neutralized" zeta potential may underlie the activating effects of PAMAMs on blood platelets.

  16. Self-organizing actin patterns shape membrane architecture but not cell mechanics

    PubMed Central

    Fritzsche, M.; Li, D.; Colin-York, H.; Chang, V. T.; Moeendarbary, E.; Felce, J. H.; Sezgin, E.; Charras, G.; Betzig, E.; Eggeling, C.

    2017-01-01

    Cell-free studies have demonstrated how collective action of actin-associated proteins can organize actin filaments into dynamic patterns, such as vortices, asters and stars. Using complementary microscopic techniques, we here show evidence of such self-organization of the actin cortex in living HeLa cells. During cell adhesion, an active multistage process naturally leads to pattern transitions from actin vortices over stars into asters. This process is primarily driven by Arp2/3 complex nucleation, but not by myosin motors, which is in contrast to what has been theoretically predicted and observed in vitro. Concomitant measurements of mechanics and plasma membrane fluidity demonstrate that changes in actin patterning alter membrane architecture but occur functionally independent of macroscopic cortex elasticity. Consequently, tuning the activity of the Arp2/3 complex to alter filament assembly may thus be a mechanism allowing cells to adjust their membrane architecture without affecting their macroscopic mechanical properties. PMID:28194011

  17. Self-organizing actin patterns shape membrane architecture but not cell mechanics

    NASA Astrophysics Data System (ADS)

    Fritzsche, M.; Li, D.; Colin-York, H.; Chang, V. T.; Moeendarbary, E.; Felce, J. H.; Sezgin, E.; Charras, G.; Betzig, E.; Eggeling, C.

    2017-02-01

    Cell-free studies have demonstrated how collective action of actin-associated proteins can organize actin filaments into dynamic patterns, such as vortices, asters and stars. Using complementary microscopic techniques, we here show evidence of such self-organization of the actin cortex in living HeLa cells. During cell adhesion, an active multistage process naturally leads to pattern transitions from actin vortices over stars into asters. This process is primarily driven by Arp2/3 complex nucleation, but not by myosin motors, which is in contrast to what has been theoretically predicted and observed in vitro. Concomitant measurements of mechanics and plasma membrane fluidity demonstrate that changes in actin patterning alter membrane architecture but occur functionally independent of macroscopic cortex elasticity. Consequently, tuning the activity of the Arp2/3 complex to alter filament assembly may thus be a mechanism allowing cells to adjust their membrane architecture without affecting their macroscopic mechanical properties.

  18. Correlating Membrane Morphological Responses with Micellar Aggregation Behavior of Capric Acid and Monocaprin.

    PubMed

    Yoon, Bo Kyeong; Jackman, Joshua A; Kim, Min Chul; Sut, Tun Naw; Cho, Nam-Joon

    2017-03-21

    The interaction of single-chain lipid amphiphiles with phospholipid membranes is relevant to many scientific fields, including molecular evolution, medicine, and biofuels. Two widely studied compounds within this class are the medium-chain saturated fatty acid, capric acid, and its monoglyceride derivative, monocaprin. To date, most studies about these compounds have involved in vitro evaluation of their biological activities, while mechanistic details of how capric acid and monocaprin interact with phospholipid bilayers remain elusive. Herein, we investigated the effect of these two compounds on the morphological and fluidic properties of prefabricated, supported lipid bilayers (SLBs). The critical micelle concentration (CMC) of each compound was determined by fluorescence spectroscopy measurements. At or above its CMC, capric acid induced the formation of elongated tubules protruding from the SLB, as determined by quartz crystal microbalance-dissipation and fluorescence microscopy experiments. By contrast, monocaprin induced the formation of elongated tubules or membrane buds below and above its CMC, respectively. Fluorescence recovery after photobleaching (FRAP) experiments indicated that capric acid increased bilayer fluidity only above its CMC, whereas monocaprin increased bilayer fluidity both above and below its CMC. We discuss these findings in the context of the two compounds' structural properties, including net charge, molecular length and hydrogen-bonding capacity. Collectively, the findings demonstrate that capric acid and monocaprin differentially affect the morphological and fluidic properties of SLBs, and that the aggregation state of the compounds plays a critical role in modulating their interactions with phospholipid membranes.

  19. Impact of Embedded Endocannabinoids and Their Oxygenation by Lipoxygenase on Membrane Properties

    PubMed Central

    2012-01-01

    N-Arachidonoylethanolamine (anandamide) and 2-arachidonoylglycerol are the best characterized endocannabinoids. Their biological activity is subjected to metabolic control whereby a dynamic equilibrium among biosynthetic, catabolic, and oxidative pathways drives their intracellular concentrations. In particular, lipoxygenases can generate hydroperoxy derivatives of endocannabinoids, endowed with distinct activities within cells. The in vivo interaction between lipoxygenases and endocannabinoids is likely to occur within cell membranes; thus, we sought to ascertain whether a prototypical enzyme like soybean (Glycine max) 15-lipoxygenase-1 is able to oxygenate endocannabinoids embedded in synthetic vesicles and how these substances could affect the binding ability of the enzyme to different lipid bilayers. We show that (i) embedded endocannabinoids increase membrane fluidity; (ii) 15-lipoxygenase-1 preferentially binds to endocannabinoid-containing bilayers; and that (iii) 15-lipoxygenase-1 oxidizes embedded endocannabinoids and thus reduces fluidity and local hydration of membrane lipids. Together, the present findings reveal further complexity in the regulation of endocannabinoid signaling within the central nervous system, disclosing novel control by oxidative pathways. PMID:22860207

  20. α- tocopherol’s location in membranes is not affected by their composition

    SciTech Connect

    Marquardt, Drew; Kucerka, Norbert; Katsaras, John; Harroun, Thad A.

    2014-10-15

    To this day, α-tocopherol's (aToc) role in humans is not well known. In previous studies, we have tried to connect aToc's biological function with its location in a-lipid bilayer. In the present study, we have determined, by means of small-angle neutron diffraction, that not only is aToc's hydroxyl group located high in the membrane but its tail also resides far from the center of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) bilayers. In addition, we located aToc's hydroxyl group above the lipid backbone in 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE), 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-L-serine (POPS), and Sphingomyelin bilayers, suggesting that aToc's location near the lipid water interface may be a universal property of vitamin E. Lastly, in light of these data, how aToc efficiently terminates lipid hydroperoxy radicals at the membrane center remains an open question.

  1. α- tocopherol’s location in membranes is not affected by their composition

    DOE PAGES

    Marquardt, Drew; Kucerka, Norbert; Katsaras, John; ...

    2014-10-15

    To this day, α-tocopherol's (aToc) role in humans is not well known. In previous studies, we have tried to connect aToc's biological function with its location in a-lipid bilayer. In the present study, we have determined, by means of small-angle neutron diffraction, that not only is aToc's hydroxyl group located high in the membrane but its tail also resides far from the center of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) bilayers. In addition, we located aToc's hydroxyl group above the lipid backbone in 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE), 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-L-serine (POPS), and Sphingomyelin bilayers, suggesting that aToc's location near the lipid water interface may be a universal propertymore » of vitamin E. Lastly, in light of these data, how aToc efficiently terminates lipid hydroperoxy radicals at the membrane center remains an open question.« less

  2. Static Magnetic Field Attenuates Lipopolysaccharide-Induced Inflammation in Pulp Cells by Affecting Cell Membrane Stability

    PubMed Central

    Tsao, Jeng-Ting; Lee, Lin-Wen; Lin, Che-Tong

    2015-01-01

    One of the causes of dental pulpitis is lipopolysaccharide- (LPS-) induced inflammatory response. Following pulp tissue inflammation, odontoblasts, dental pulp cells (DPCs), and dental pulp stem cells (DPSCs) will activate and repair damaged tissue to maintain homeostasis. However, when LPS infection is too serious, dental repair is impossible and disease may progress to irreversible pulpitis. Therefore, the aim of this study was to examine whether static magnetic field (SMF) can attenuate inflammatory response of dental pulp cells challenged with LPS. In methodology, dental pulp cells were isolated from extracted teeth. The population of DPSCs in the cultured DPCs was identified by phenotypes and multilineage differentiation. The effects of 0.4 T SMF on DPCs were observed through MTT assay and fluorescent anisotropy assay. Our results showed that the SMF exposure had no effect on surface markers or multilineage differentiation capability. However, SMF exposure increases cell viability by 15%. In addition, SMF increased cell membrane rigidity which is directly related to higher fluorescent anisotropy. In the LPS-challenged condition, DPCs treated with SMF demonstrated a higher tolerance to LPS-induced inflammatory response when compared to untreated controls. According to these results, we suggest that 0.4 T SMF attenuates LPS-induced inflammatory response to DPCs by changing cell membrane stability. PMID:25884030

  3. α-Tocopherol's Location in Membranes Is Not Affected by Their Composition.

    PubMed

    Marquardt, Drew; Kučerka, Norbert; Katsaras, John; Harroun, Thad A

    2015-04-21

    To this day, α-tocopherol's (aToc) role in humans is not well known. In previous studies, we have tried to connect aToc's biological function with its location in a lipid bilayer. In the present study, we have determined, by means of small-angle neutron diffraction, that not only is aToc's hydroxyl group located high in the membrane but its tail also resides far from the center of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) bilayers. In addition, we located aToc's hydroxyl group above the lipid backbone in 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE), 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-L-serine (POPS), and sphingomyelin bilayers, suggesting that aToc's location near the lipid-water interface may be a universal property of vitamin E. In light of these data, how aToc efficiently terminates lipid hydroperoxy radicals at the membrane center remains an open question.

  4. The Evolutionarily Conserved Protein PHOTOSYNTHESIS AFFECTED MUTANT71 Is Required for Efficient Manganese Uptake at the Thylakoid Membrane in Arabidopsis

    PubMed Central

    Steinberger, Iris; Herdean, Andrei; Gandini, Chiara; Labs, Mathias; Flügge, Ulf-Ingo; Geimer, Stefan; Schmidt, Sidsel Birkelund; Husted, Søren; Spetea, Cornelia; Leister, Dario

    2016-01-01

    In plants, algae, and cyanobacteria, photosystem II (PSII) catalyzes the light-driven oxidation of water. The oxygen-evolving complex of PSII is a Mn4CaO5 cluster embedded in a well-defined protein environment in the thylakoid membrane. However, transport of manganese and calcium into the thylakoid lumen remains poorly understood. Here, we show that Arabidopsis thaliana PHOTOSYNTHESIS AFFECTED MUTANT71 (PAM71) is an integral thylakoid membrane protein involved in Mn2+ and Ca2+ homeostasis in chloroplasts. This protein is required for normal operation of the oxygen-evolving complex (as evidenced by oxygen evolution rates) and for manganese incorporation. Manganese binding to PSII was severely reduced in pam71 thylakoids, particularly in PSII supercomplexes. In cation partitioning assays with intact chloroplasts, Mn2+ and Ca2+ ions were differently sequestered in pam71, with Ca2+ enriched in pam71 thylakoids relative to the wild type. The changes in Ca2+ homeostasis were accompanied by an increased contribution of the transmembrane electrical potential to the proton motive force across the thylakoid membrane. PSII activity in pam71 plants and the corresponding Chlamydomonas reinhardtii mutant cgld1 was restored by supplementation with Mn2+, but not Ca2+. Furthermore, PAM71 suppressed the Mn2+-sensitive phenotype of the yeast mutant Δpmr1. Therefore, PAM71 presumably functions in Mn2+ uptake into thylakoids to ensure optimal PSII performance. PMID:27020959

  5. Cholesterol stimulates and ceramide inhibits Sticholysin II-induced pore formation in complex bilayer membranes.

    PubMed

    Alm, Ida; García-Linares, Sara; Gavilanes, José G; Martínez-Del-Pozo, Álvaro; Slotte, J Peter

    2015-04-01

    The pore forming capacity of Sticholysin II (StnII; isolated from Stichodactyla helianthus) in bilayer membranes containing 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), palmitoylsphingomyelin (PSM) and either cholesterol or palmitoyl ceramide (PCer) has been examined. The aim of the study was to elucidate how the presence of differently ordered PSM domains affected StnII oligomerization and pore formation. Cholesterol is known to enhance pore formation by StnII, and our results confirmed this and provide kinetic information for the process. The effect of cholesterol on bilayer permeabilization kinetics was concentration-dependent. In the concentration regime used (2.5-10nmol cholesterol in POPC:PSM 80:20 by nmol), cholesterol also increased the acyl chain order in the fluid PSM domain and thus decreased bilayer fluidity, suggesting that fluidity per se was not responsible for cholesterol's effect. Addition of PCer (2.5-10nmol) to the POPC:PSM (80:20 by nmol) bilayers attenuated StnII-induced pore formation, again in a concentration-dependent fashion. This addition also led to the formation of a PCer-rich gel phase. Addition of cholesterol to PCer-containing membranes could partially reduce the inhibitory effect of PCer on StnII pore formation. We conclude that the physical state of PSM (as influenced by either cholesterol or PCer) affected StnII binding and pore formation under the conditions examined.

  6. CTP:phosphocholine cytidylyltransferase α (CCTα) and lamins alter nuclear membrane structure without affecting phosphatidylcholine synthesis.

    PubMed

    Gehrig, Karsten; Ridgway, Neale D

    2011-06-01

    CTP:phosphocholine cytidylyltransferase α (CCTα) is a nuclear enzyme that catalyzes the rate-limiting step in the CDP-choline pathway for phosphatidylcholine (PC) synthesis. Lipid activation of CCTα results in its translocation to the nuclear envelope and expansion of an intranuclear membrane network termed the nucleoplasmic reticulum (NR) by a mechanism involving membrane deformation. Nuclear lamins are also required for stability and proliferation of the NR, but whether this unique structure, or the nuclear lamina in general, is required for PC synthesis is not known. To examine this relationship, the nuclear lamina was depleted by RNAi or disrupted by expression of the Hutchinson-Gilford progeria syndrome (HGPS) mutant lamin A (progerin), and the effect on CCTα and choline metabolism was analyzed. siRNA-mediated silencing of lamin A/C or lamin B1 in CHO cells to diminish the NR had no effect on PC synthesis, while double knockdown non-specifically inhibited the pathway. Confirming this minor role in PC synthesis, only 10% of transiently overexpressed choline/ethanolamine phosphotransferase was detected in the NR. In CHO cells, CCTα was nucleoplasmic and co-localized with GFP-progerin in nuclear folds and invaginations; however, HGPS fibroblasts displayed an abnormal distribution of CCTα in the cytoplasm and nuclear envelope that was accompanied by a 2-fold reduction in PC synthesis. In spite of its altered localization, choline-labeling experiments showed that CCT activity was unaffected, and inhibition of PC synthesis was traced to reduced activity of a hemicholinium-sensitive choline transporter. We conclude that CCTα and lamins specifically cooperate to form the NR, but the overall structure of the nuclear envelope has a minimal impact on CCT activity and PC synthesis.

  7. VLDL lipolysis products increase VLDL fluidity and convert apolipoprotein E4 into a more expanded conformation.

    PubMed

    Tetali, Sarada D; Budamagunta, Madhu S; Simion, Catalina; den Hartigh, Laura J; Kálai, Tamás; Hideg, Kálmán; Hatters, Danny M; Weisgraber, Karl H; Voss, John C; Rutledge, John C

    2010-06-01

    Our previous work indicated that apolipoprotein (apo) E4 assumes a more expanded conformation in the postprandial period. The postprandial state is characterized by increased VLDL lipolysis. In this article, we tested the hypothesis that VLDL lipolysis products increase VLDL particle fluidity, which mediates expansion of apoE4 on the VLDL particle. Plasma from healthy subjects was collected before and after a moderately high-fat meal and incubated with nitroxyl-spin labeled apoE. ApoE conformation was examined by electron paramagnetic resonance spectroscopy using targeted spin probes on cysteines introduced in the N-terminal (S76C) and C-terminal (A241C) domains. Further, we synthesized a novel nitroxyl spin-labeled cholesterol analog, which gave insight into lipoprotein particle fluidity. Our data revealed that the order of lipoprotein fluidity was HDL approximately LDLfluidity, VLDL lipolysis products significantly altered apoE4 into a more expanded conformation. Our studies indicate that after every meal, VLDL fluidity is increased causing apoE4 associated with VLDL to assume a more expanded conformation, potentially enhancing the pathogenicity of apoE4 in vascular tissue.

  8. VLDL lipolysis products increase VLDL fluidity and convert apolipoprotein E4 into a more expanded conformation

    PubMed Central

    Tetali, Sarada D.; Budamagunta, Madhu S.; Simion, Catalina; den Hartigh, Laura J.; Kálai, Tamás; Hideg, Kálmán; Hatters, Danny M.; Weisgraber, Karl H.; Voss, John C.; Rutledge, John C.

    2010-01-01

    Our previous work indicated that apolipoprotein (apo) E4 assumes a more expanded conformation in the postprandial period. The postprandial state is characterized by increased VLDL lipolysis. In this article, we tested the hypothesis that VLDL lipolysis products increase VLDL particle fluidity, which mediates expansion of apoE4 on the VLDL particle. Plasma from healthy subjects was collected before and after a moderately high-fat meal and incubated with nitroxyl-spin labeled apoE. ApoE conformation was examined by electron paramagnetic resonance spectroscopy using targeted spin probes on cysteines introduced in the N-terminal (S76C) and C-terminal (A241C) domains. Further, we synthesized a novel nitroxyl spin-labeled cholesterol analog, which gave insight into lipoprotein particle fluidity. Our data revealed that the order of lipoprotein fluidity was HDL∼LDLfluidity, VLDL lipolysis products significantly altered apoE4 into a more expanded conformation. Our studies indicate that after every meal, VLDL fluidity is increased causing apoE4 associated with VLDL to assume a more expanded conformation, potentially enhancing the pathogenicity of apoE4 in vascular tissue. PMID:19965582

  9. Alterations of erythrocyte membrane organization in alcoholics.

    PubMed

    Beaugé, F; Stibler, H; Borg, S

    1987-01-01

    Studies of fluorescence polarization of DPH have shown that erythrocyte membrane "fluidity" and fluidization by ethanol are significantly reduced in alcoholics. By using probes of the polar part of the membrane, ANS and TMA-DPH, in addition to DPH, it was shown in the present study that disturbances also exist in the polar region of the membrane which probably are related to changes in surface glycoconjugates. Furthermore, the acute fluidizing effect of ethanol was correlated with the capacity of the membrane to bind ethanol, which in turn appeared to be linked to the glycans. Chronic ethanol abuse thus causes complex disturbances of membrane organization at different levels of the membrane.

  10. Biophysical characterization of genistein-membrane interaction and its correlation with biological effect on cells - The case of EYPC liposomes and human erythrocyte membranes.

    PubMed

    Pawlikowska-Pawlęga, Bożena; Misiak, Lucjan E; Jarosz-Wilkołazka, Anna; Zarzyka, Barbara; Paduch, Roman; Gawron, Antoni; Gruszecki, Wieslaw I

    2014-08-01

    With application of EPR and (1)H NMR techniques genistein interaction with liposomes formed with egg yolk lecithin and with erythrocyte membranes was assessed. The present study addressed the problem of genistein localization and its effects on lipid membrane fluidity and protein conformation. The range of microscopic techniques was employed to study genistein effects on HeLa cells and human erythrocytes. Moreover, DPPH bioassay, superoxide anion radical test and enzymatic measurements were performed in HeLa cells subjected to genistein. The gathered results from both EPR and NMR techniques indicated strong ordering effect of genistein on the motional freedom of lipids in the head group region and the adjacent hydrophobic zone in liposomal as well as in red blood cell membranes. EPR study of human ghost showed also the changes in the erythrocyte membrane protein conformation. The membrane effects of genistein were correlated with the changes in internal membranes arrangement of HeLa cells as it was noticed using transmission electron microscopic and fluorescent techniques. Scanning electron and light microscopy methods showed that one of the aftermaths of genistein incorporation into membranes was creation of echinocytic form of the red blood cells with reduced diameter. Genistein improved redox status of HeLa cells treated with H2O2 by lowering radicals' level. In conclusion, the capacity of genistein to incorporate, to affect membrane organization and to change its biophysical properties is correlated with the changes inside the cells.

  11. Oncogenic Mutations Differentially Affect Bax Monomer, Dimer, and Oligomeric Pore Formation in the Membrane

    NASA Astrophysics Data System (ADS)

    Zhang, Mingzhen; Zheng, Jie; Nussinov, Ruth; Ma, Buyong

    2016-09-01

    Dysfunction of Bax, a pro-apoptotic regulator of cellular metabolism is implicated in neurodegenerative diseases and cancer. We have constructed the first atomistic models of the Bax oligomeric pore consisting with experimental residue-residue distances. The models are stable, capturing well double electron-electron resonance (DEER) spectroscopy measurements and provide structural details in line with the DEER data. Comparison with the latest experimental results revealed that our models agree well with both Bax and Bak pores, pointed to a converged structural arrangement for Bax and Bak pore formation. Using multi-scale molecular dynamics simulations, we probed mutational effects on Bax transformation from monomer → dimer → membrane pore formation at atomic resolution. We observe that two cancer-related mutations, G40E and S118I, allosterically destabilize the monomer and stabilize an off-pathway swapped dimer, preventing productive pore formation. This observation suggests a mechanism whereby the mutations may work mainly by over-stabilizing the monomer → dimer transformation toward an unproductive off-pathway swapped-dimer state. Our observations point to misfolded Bax states, shedding light on the molecular mechanism of Bax mutation-elicited cancer. Most importantly, the structure of the Bax pore facilitates future study of releases cytochrome C in atomic detail.

  12. Membrane stretch affects gating modes of a skeletal muscle sodium channel.

    PubMed Central

    Tabarean, I V; Juranka, P; Morris, C E

    1999-01-01

    The alpha subunit of the human skeletal muscle Na(+) channel recorded from cell-attached patches yielded, as expected for Xenopus oocytes, two current components that were stable for tens of minutes during 0.2 Hz stimulation. Within seconds of applying sustained stretch, however, the slower component began decreasing and, depending on stretch intensity, disappeared in 1-3 min. Simultaneously, the faster current increased. The resulting fast current kinetics and voltage sensitivity were indistinguishable from the fast components 1) left after 10 Hz depolarizations, and 2) that dominated when alpha subunit was co-expressed with human beta1 subunit. Although high frequency depolarization-induced loss of slow current was reversible, the stretch-induced slow-to-fast conversion was irreversible. The conclusion that stretch converted a single population of alpha subunits from an abnormal slow to a bona fide fast gating mode was confirmed by using gigaohm seals formed without suction, in which fast gating was originally absent. For brain Na(+) channels, co-expressing G proteins with the channel alpha subunit yields slow gating. Because both stretch and beta1 subunits induced the fast gating mode, perhaps they do so by minimizing alpha subunit interactions with G proteins or with other regulatory molecules available in oocyte membrane. Because of the possible involvement of oocyte molecules, it remains to be determined whether the Na(+) channel alpha subunit was directly or secondarily susceptible to bilayer tension. PMID:10423424

  13. Oncogenic Mutations Differentially Affect Bax Monomer, Dimer, and Oligomeric Pore Formation in the Membrane

    PubMed Central

    Zhang, Mingzhen; Zheng, Jie; Nussinov, Ruth; Ma, Buyong

    2016-01-01

    Dysfunction of Bax, a pro-apoptotic regulator of cellular metabolism is implicated in neurodegenerative diseases and cancer. We have constructed the first atomistic models of the Bax oligomeric pore consisting with experimental residue-residue distances. The models are stable, capturing well double electron-electron resonance (DEER) spectroscopy measurements and provide structural details in line with the DEER data. Comparison with the latest experimental results revealed that our models agree well with both Bax and Bak pores, pointed to a converged structural arrangement for Bax and Bak pore formation. Using multi-scale molecular dynamics simulations, we probed mutational effects on Bax transformation from monomer → dimer → membrane pore formation at atomic resolution. We observe that two cancer-related mutations, G40E and S118I, allosterically destabilize the monomer and stabilize an off-pathway swapped dimer, preventing productive pore formation. This observation suggests a mechanism whereby the mutations may work mainly by over-stabilizing the monomer → dimer transformation toward an unproductive off-pathway swapped-dimer state. Our observations point to misfolded Bax states, shedding light on the molecular mechanism of Bax mutation-elicited cancer. Most importantly, the structure of the Bax pore facilitates future study of releases cytochrome C in atomic detail. PMID:27630059

  14. Interactions of divalent calcium ions with head groups of zwitterionic phosphatidylcholine liposomal membranes.

    PubMed

    Santhosh, Poornima Budime; Velikonja, Aljaž; Gongadze, Ekaterina; Iglič, Aleš; Kralj-Iglič, Veronika; Ulrih, Nataša Poklar

    2014-01-01

    The interaction of the divalent calcium ions with the zwitterionic lipid membranes was studied by measuring the lipid order parameter which is inversely proportional to the membrane fluidity. Small unilamellar lipid vesicles were prepared from 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine and then treated with different concentrations of divalent calcium ions. An increase in the order parameter and decrease in the fluidity of the liposomal membranes were observed after treatment with the calcium ions. The presence of positively charged iron oxide nanoparticles in the suspension of liposomes negligibly changed the results. The results of experiments were discussed theoretically within modified Langevin-Poisson-Boltzmann (MLPB) model leading to the conclusion that the membrane fluidity and ordering of the membrane lipids are primarily altered by the accumulation of calcium ions in the region of negatively charged phosphate groups within the head groups of the membrane lipids.

  15. Effect of Sterol Structure on Chain Ordering of an Unsaturated Phospholipid: A 2H-NMR Study of POPC/Sterol Membranes

    NASA Astrophysics Data System (ADS)

    Shaghaghi, Mehran; Thewalt, Jenifer; Zuckermann, Martin

    2012-10-01

    The physical properties of biological membranes are considerably altered by the presence of sterols. In particular, sterols help to maintain the integrity of the cell by adjusting the fluidity of the plasma membrane. Cholesterol is in addition an important component of lipid rafts which are hypothesized to compartmentalize the cell membrane surface thereby making it possible for certain proteins to function. Using 2H-NMR spectroscopy, we studied the effect of a series of different sterols on the chain ordering of POPC, an unsaturated phospholipid present in eukaryotic cell membranes. We were able to assigned specific roles to the structural differences between the sterols by comparing the manner in which they affect the average lipid chain conformation of POPC.

  16. [Effect of extracted ZG from gardenia on Hep-2 cell membrane post infected with parainfluenza virus type 1 (PIV-1)].

    PubMed

    Guo, Shan-Shan; Huang, Yang; Zhao, Ye; Gao, Ying-Jie; Gong, Wen-Feng; Cui, Xiao-Lan

    2007-09-01

    In order to study the anti-viral mechanism of extracted ZG from Gardenia, the effect of extracted ZG on Hep-2 cell membrane potential, Na -K+-ATPase activity and membrane fluidity post infected with parainfluenza virus type 1 (PIV-1) was observed. Acetylcholine which was fluorescent labeled with DiBAC4 (3) was taken as positive control to observe the changes of membrane potential and was measured by flow cytometer. The phosphorus determination method and spectrophotometer were used to measure the Na+-K+-ATPase activity of Hep-2 cell membrane post PIV-1 infection. Hep-2 cell membrane phospholipids was labeled with fluorescent NBD-C6-HPC and membrane fluidity was measured by confocal laser scanning microscope. The results demonstated that after PIV-1 infection the Hep-2 cell membrane potential decreased significantly and the membrane was in the state of hyperpolarization, Na+-K+-ATPase activity increased and membrane fluidity decreased significantly. There was no apparent interferring effect of extracted ZG on the changes of membrane potential and Na+-K+-ATPase activity post PIV-1 infection, while membrane fluidity was improved significantly. Acetylcholine improved the state of hyperpolarization. The changes of membrane potential, Na -K+-ATPase activity and membrane fluidity might be the biomechanism of PIV-1 infectoin. The extracted ZG improved membrane fluidity to prevent from PIV-1 infection by protecting the cell membrane, which was probably the mechanism of anti-PIV-1 activity of the extracted ZG, but ZG probably had nothing to do with membrane potential and Na+-K+-ATPase activity.

  17. It is all about fluidity: Fatty acids and macrophage phagocytosis.

    PubMed

    Schumann, Julia

    2016-08-15

    Phagocytosis is an early and fundamental step for the effective clearance of disease causing agents. The ability to engulf and kill pathogens is considered as a major effector function of macrophages. In their phagocytic role macrophages are part of the first line of innate immune defense. A number of studies investigating fatty acid effects on macrophage phagocytosis have been conducted over many years. In vitro-data consistently report that alterations in macrophage membrane fatty acid composition are linked to an altered phagocytic capacity, i.e. an increase in membrane unsaturated fatty acid content is associated with an increase in engulfment and killing rate. The mode of action of fatty acids seems to be the modulation of the physical nature of the macrophage plasma membrane. It appears that the saturated-to-unsaturated fatty acid ratio of macrophage membrane phospholipids is of importance in determining macrophage phagocytic capacity. Available in vivo-data are less clear. At present, there is a lack of systematic studies elucidating key factors such as fatty acid efficacy, effective dose or dosing intervals. Without this knowledge the targeted modulation of macrophage phagocytosis in vivo by fatty acids is still a distant possibility.

  18. Psoralen and Ultraviolet A Light Treatment Directly Affects Phosphatidylinositol 3-Kinase Signal Transduction by Altering Plasma Membrane Packing.

    PubMed

    Van Aelst, Britt; Devloo, Rosalie; Zachée, Pierre; t'Kindt, Ruben; Sandra, Koen; Vandekerckhove, Philippe; Compernolle, Veerle; Feys, Hendrik B

    2016-11-18

    Psoralen and ultraviolet A light (PUVA) are used to kill pathogens in blood products and as a treatment of aberrant cell proliferation in dermatitis, cutaneous T-cell lymphoma, and graft-versus-host disease. DNA damage is well described, but the direct effects of PUVA on cell signal transduction are poorly understood. Because platelets are anucleate and contain archetypal signal transduction machinery, they are ideally suited to address this. Lipidomics on platelet membrane extracts showed that psoralen forms adducts with unsaturated carbon bonds of fatty acyls in all major phospholipid classes after PUVA. Such adducts increased lipid packing as measured by a blue shift of an environment-sensitive fluorescent probe in model liposomes. Furthermore, the interaction of these liposomes with lipid order-sensitive proteins like amphipathic lipid-packing sensor and α-synuclein was inhibited by PUVA. In platelets, PUVA caused poor membrane binding of Akt and Bruton's tyrosine kinase effectors following activation of the collagen glycoprotein VI and thrombin protease-activated receptor (PAR) 1. This resulted in defective Akt phosphorylation despite unaltered phosphatidylinositol 3,4,5-trisphosphate levels. Downstream integrin activation was furthermore affected similarly by PUVA following PAR1 (effective half-maximal concentration (EC50), 8.4 ± 1.1 versus 4.3 ± 1.1 μm) and glycoprotein VI (EC50, 1.61 ± 0.85 versus 0.26 ± 0.21 μg/ml) but not PAR4 (EC50, 50 ± 1 versus 58 ± 1 μm) signal transduction. Our findings were confirmed in T-cells from graft-versus-host disease patients treated with extracorporeal photopheresis, a form of systemic PUVA. In conclusion, PUVA increases the order of lipid phases by covalent modification of phospholipids, thereby inhibiting membrane recruitment of effector kinases.

  19. Enteric YaiW Is a Surface-Exposed Outer Membrane Lipoprotein That Affects Sensitivity to an Antimicrobial Peptide

    PubMed Central

    Arnold, Markus F. F.; Caro-Hernandez, Paola; Tan, Karen; Runti, Giulia; Wehmeier, Silvia; Scocchi, Marco; Doerrler, William T.; Ferguson, Gail P.

    2014-01-01

    yaiW is a previously uncharacterized gene found in enteric bacteria that is of particular interest because it is located adjacent to the sbmA gene, whose bacA ortholog is required for Sinorhizobium meliloti symbiosis and Brucella abortus pathogenesis. We show that yaiW is cotranscribed with sbmA in Escherichia coli and Salmonella enterica serovar Typhi and Typhimurium strains. We present evidence that the YaiW is a palmitate-modified surface exposed outer membrane lipoprotein. Since BacA function affects the very-long-chain fatty acid (VLCFA) modification of S. meliloti and B. abortus lipid A, we tested whether SbmA function might affect either the fatty acid modification of the YaiW lipoprotein or the fatty acid modification of enteric lipid A but found that it did not. Interestingly, we did observe that E. coli SbmA suppresses deficiencies in the VLCFA modification of the lipopolysaccharide of an S. meliloti bacA mutant despite the absence of VLCFA in E. coli. Finally, we found that both YaiW and SbmA positively affect the uptake of proline-rich Bac7 peptides, suggesting a possible connection between their cellular functions. PMID:24214946

  20. Identification of key water quality characteristics affecting the filterability of biologically treated effluent in low-pressure membrane filtration.

    PubMed

    Nguyen, T; Fan, L; Roddick, F A; Harris, J L

    2010-01-01

    There are many water quality characteristics which could influence the filterability of biologically treated effluent from Melbourne's Western Treatment Plant (WTP). Statistical correlation was used to identify the key water characteristics affecting the microfiltration (MF) and ultrafiltration (UF) filterability in terms of permeate volume of the treated effluent. The models developed showed that turbidity, dissolved organic carbon (DOC) and total suspended solids (TSS) were the key factors which influenced the MF and UF filterability. Turbidity was the dominant factor affecting the accuracy of the model for MF filterability while DOC was the major factor affecting the accuracy of the model for UF filterability. A prediction accuracy of 85% was obtained for MF and 86% for UF filterability of the WTP effluent. The characteristics of the organic components of the wastewater were demonstrated by EEM spectra to have seasonal variation which would have reduced the prediction accuracy. As turbidity, DOC and TSS can be determined on-line, the models would be useful for rapid prediction of the filterability of WTP effluent and this may assist the control of low-pressure membrane filtration processes.

  1. Chemical properties of lipids strongly affect the kinetics of the membrane-induced aggregation of α-synuclein

    PubMed Central

    Brown, James W. P.; Ouberai, Myriam M.; Flagmeier, Patrick; Vendruscolo, Michele; Buell, Alexander K.; Sparr, Emma; Dobson, Christopher M.

    2016-01-01

    Intracellular α-synuclein deposits, known as Lewy bodies, have been linked to a range of neurodegenerative disorders, including Parkinson’s disease. α-Synuclein binds to synthetic and biological lipids, and this interaction has been shown to play a crucial role for both α-synuclein’s native function, including synaptic plasticity, and the initiation of its aggregation. Here, we describe the interplay between the lipid properties and the lipid binding and aggregation propensity of α-synuclein. In particular, we have observed that the binding of α-synuclein to model membranes is much stronger when the latter is in the fluid rather than the gel phase, and that this binding induces a segregation of the lipids into protein-poor and protein-rich populations. In addition, α-synuclein was found to aggregate at detectable rates only when interacting with membranes composed of the most soluble lipids investigated here. Overall, our results show that the chemical properties of lipids determine whether or not the lipids can trigger the aggregation of α-synuclein, thus affecting the balance between functional and aberrant behavior of the protein. PMID:27298346

  2. Effects of unripe Citrus hassaku fruits extract and its flavanone glycosides on blood fluidity.

    PubMed

    Itoh, Kimihisa; Masuda, Megumi; Naruto, Shunsuke; Murata, Kazuya; Matsuda, Hideaki

    2010-01-01

    The enhancement of blood fluidity may lead to improvements in skin problems resulting from unsmooth circulation or blood stagnation. Since a 50% ethanolic extract (CH-ext) obtained from unripe Citrus hassaku fruits may be a useful ingredient in skin-whitening cosmetics, the present study was designed to examine the effect of CH-ext on blood fluidity. CH-ext concentration-dependently inhibited in vitro collagen-induced rabbit platelet aggregation and in vitro polybrene-induced rat erythrocyte aggregation. The CH-ext showed in vitro fibrinolysis activity in fibrin plate assay. Activity-guided fractionation of the CH-ext using antiplatelet activity, inhibitory activity of erythrocyte aggregation, and fibrinolysis activity revealed that these activities of CH-ext were attributable to naringenin-7-glycoside (prunin). Successive oral administration of CH-ext to rats inhibited the lipopolysaccharide (LPS)-induced decrease of blood platelets and fibrinogen, and LPS-induced increase of fibrin degradation products (FDP) in LPS-induced disseminated intravascular coagulation (DIC) model rats. Effects of CH-ext on blood fluidity were analyzed by a micro channel array flow analyzer (MC-FAN). Preventive oral administration of CH-ext to rats showed dose-dependent reduction of the passage time of whole blood flow of the DIC model rats in comparison with that of the vehicle control rats. These results imply that CH-ext may have effects which improve effects on blood fluidity.

  3. Cast B2-phase iron-aluminum alloys with improved fluidity

    DOEpatents

    Maziasz, Philip J.; Paris, Alan M.; Vought, Joseph D.

    2002-01-01

    Systems and methods are described for iron aluminum alloys. A composition includes iron, aluminum and manganese. A method includes providing an alloy including iron, aluminum and manganese; and processing the alloy. The systems and methods provide advantages because additions of manganese to iron aluminum alloys dramatically increase the fluidity of the alloys prior to solidification during casting.

  4. Factors that affect the permeability of commercial hollow-fibre membranes in a submerged anaerobic MBR (HF-SAnMBR) system.

    PubMed

    Robles, A; Ruano, M V; Ribes, J; Ferrer, J

    2013-03-01

    A demonstration plant with two commercial HF ultrafiltration membrane modules (PURON(®), Koch Membrane Systems, PUR-PSH31) was operated with urban wastewater. The effect of the main operating variables on membrane performance at sub-critical and supra-critical filtration conditions was tested. The physical operating variables that affected membrane performance most were gas sparging intensity and back-flush (BF) frequency. Indeed, low gas sparging intensities (around 0.23 Nm(3) h(-1) m(-2)) and low BF frequencies (30-s back-flush for every 10 basic filtration-relaxation cycles) were enough to enable membranes to be operated sub-critically even when levels of mixed liquor total solids were high (up to 25 g L(-1)). On the other hand, significant gas sparging intensities and BF frequencies were required in order to maintain long-term operating at supra-critical filtration conditions. After operating for more than two years at sub-critical conditions (transmembrane flux between 9 and 13.3 LMH at gas sparging intensities of around 0.23 Nm(3) h(-1) m(-2) and MLTS levels from around 10-30 g L(-1)) no significant irreversible/irrecoverable fouling problems were detected (membrane permeability remained above 100 LMH bar(-1) and total filtration resistance remained below 10(13) m(-1)), therefore no chemical cleaning was conducted. Membrane performance was similar to the aerobic HF membranes operated in full-scale MBR plants.

  5. Aspirin inhibits formation of cholesterol rafts in fluid lipid membranes.

    PubMed

    Alsop, Richard J; Toppozini, Laura; Marquardt, Drew; Kučerka, Norbert; Harroun, Thad A; Rheinstädter, Maikel C

    2015-03-01

    Aspirin and other non-steroidal anti-inflammatory drugs have a high affinity for phospholipid membranes, altering their structure and biophysical properties. Aspirin has been shown to partition into the lipid head groups, thereby increasing membrane fluidity. Cholesterol is another well known mediator of membrane fluidity, in turn increasing membrane stiffness. As well, cholesterol is believed to distribute unevenly within lipid membranes leading to the formation of lipid rafts or plaques. In many studies, aspirin has increased positive outcomes for patients with high cholesterol. We are interested if these effects may be, at least partially, the result of a non-specific interaction between aspirin and cholesterol in lipid membranes. We have studied the effect of aspirin on the organization of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) membranes containing cholesterol. Through Langmuir-Blodgett experiments we show that aspirin increases the area per lipid and decreases compressibility at 32.5 mol% cholesterol, leading to a significant increase of fluidity of the membranes. Differential scanning calorimetry provides evidence for the formation of meta-stable structures in the presence of aspirin. The molecular organization of lipids, cholesterol and aspirin was studied using neutron diffraction. While the formation of rafts has been reported in binary DPPC/cholesterol membranes, aspirin was found to locally disrupt membrane organization and lead to the frustration of raft formation. Our results suggest that aspirin is able to directly oppose the formation of cholesterol structures through non-specific interactions with lipid membranes.

  6. Differences in Sexual Orientation Diversity and Sexual Fluidity in Attractions among Gender Minority Adults in Massachusetts

    PubMed Central

    Katz-Wise, Sabra L.; Reisner, Sari L.; White, Jaclyn M.; Keo-Meier, Colton L.

    2015-01-01

    This study characterized sexual orientation identities and sexual fluidity in attractions in a community-based sample of self-identified transgender and gender nonconforming adults in Massachusetts. Participants were recruited in 2013 using bi-model methods (online and in-person) to complete a one-time web-based quantitative survey that included questions about sexual orientation identity and sexual fluidity. Multivariable logistic regression models estimated Adjusted Risk Ratios (aRR) and 95% Confidence Intervals (95% CI) to examine the correlates of self-reported changes in attractions ever in lifetime among the whole sample (n=452) and after transition among those who reported social gender transition (n=205). The sample endorsed diverse sexual orientation identities: 42.7% queer, 19.0% other non-binary, 15.7% bisexual, 12.2% straight, 10.4% gay/lesbian. Overall, 58.2% reported having experienced changes in sexual attractions in their lifetime. In adjusted models, trans masculine individuals were more likely than trans feminine individuals to report sexual fluidity in their lifetime (aRR=1.69; 95% CI=1.34, 2.12). Among those who transitioned, 64.6% reported a change in attractions post-transition and trans masculine individuals were less likely than trans feminine individuals to report sexual fluidity (aRR=0.44; 95% CI=0.28, 0.69). Heterogeneity of sexual orientation identities and sexual fluidity in attractions are the norm rather than the exception among gender minority people. PMID:26156113

  7. miRNAs in the vitreous humor of patients affected by idiopathic epiretinal membrane and macular hole

    PubMed Central

    Ragusa, Marco; Barbagallo, Cristina; Longo, Antonio; Avitabile, Teresio; Uva, Maurizio G.; Bonfiglio, Vincenza; Toro, Mario D.; Caltabiano, Rosario; Mariotti, Cesare; Boscia, Francesco; Romano, Mario; Di Pietro, Cinzia; Barbagallo, Davide; Purrello, Michele; Reibaldi, Michele

    2017-01-01

    Purpose The aim of the present study was to assess the expression of miRNAs in the Vitreous Humor (VH) of patients with Macular Hole (MH) and Epiretinal Membrane (ERM) compared to a control group. Methods In this prospective, comparative study, 2-ml of VH was extracted from the core of the vitreous chamber in consecutive patients who underwent standard vitrectomy for ERM and MH. RNA was extracted and TaqMan® Low Density Arrays (TLDAs) were used to profile the transcriptome of 754 miRNAs. Results were validated by single TaqMan® assays. Finally, we created a biological network of differentially expressed miRNA targets and their nearest neighbors. Results Overall 10 eyes with MH, 16 eyes with idiopathic ERM and 6 controls were enrolled in the study. Profiling data identified 5 miRNAs differentially expressed in patients affected by MH and ERM with respect to controls. Four were downregulated (miR-19b, miR-24, miR-155, miR-451) and 1 was downregulated (miR-29a); TaqMan® assays of the VH of patients affected by MH and ERM, with respect to controls, showed that the most differentially expressed were miR-19b (FC -9.13, p:<0.00004), mir-24 (FC -7.52, p:<0.004) and miR-142-3p (FC -5.32, p:<0.011). Our network data showed that deregulation of differentially expressed miRNAs induces an alteration of several pathways associated with genes involved in both MH and ERM. Conclusion The present study suggests that disregulation of miR-19b, miR-24 and miR-142-3p, might be related to the alterations that characterize patients affected by MH and ERM. PMID:28328945

  8. Fermentation temperature modulates phosphatidylethanolamine and phosphatidylinositol levels in the cell membrane of Saccharomyces cerevisiae.

    PubMed

    Henderson, Clark M; Zeno, Wade F; Lerno, Larry A; Longo, Marjorie L; Block, David E

    2013-09-01

    During alcoholic fermentation, Saccharomyces cerevisiae is exposed to a host of environmental and physiological stresses. Extremes of fermentation temperature have previously been demonstrated to induce fermentation arrest under growth conditions that would otherwise result in complete sugar utilization at "normal" temperatures and nutrient levels. Fermentations were carried out at 15°C, 25°C, and 35°C in a defined high-sugar medium using three Saccharomyces cerevisiae strains with diverse fermentation characteristics. The lipid composition of these strains was analyzed at two fermentation stages, when ethanol levels were low early in stationary phase and in late stationary phase at high ethanol concentrations. Several lipids exhibited dramatic differences in membrane concentration in a temperature-dependent manner. Principal component analysis (PCA) was used as a tool to elucidate correlations between specific lipid species and fermentation temperature for each yeast strain. Fermentations carried out at 35°C exhibited very high concentrations of several phosphatidylinositol species, whereas at 15°C these yeast strains exhibited higher levels of phosphatidylethanolamine and phosphatidylcholine species with medium-chain fatty acids. Furthermore, membrane concentrations of ergosterol were highest in the yeast strain that experienced stuck fermentations at all three temperatures. Fluorescence anisotropy measurements of yeast cell membrane fluidity during fermentation were carried out using the lipophilic fluorophore diphenylhexatriene. These measurements demonstrate that the changes in the lipid composition of these yeast strains across the range of fermentation temperatures used in this study did not significantly affect cell membrane fluidity. However, the results from this study indicate that fermenting S. cerevisiae modulates its membrane lipid composition in a temperature-dependent manner.

  9. N-linked glycans do not affect plasma membrane localization of multidrug resistance protein 4 (MRP4) but selectively alter its prostaglandin E2 transport activity.

    PubMed

    Miah, M Fahad; Conseil, Gwenaëlle; Cole, Susan P C

    2016-01-22

    Multidrug resistance protein 4 (MRP4) is a member of subfamily C of the ATP-binding cassette superfamily of membrane transport proteins. MRP4 mediates the ATP-dependent efflux of many endogenous and exogenous solutes across the plasma membrane, and in polarized cells, it localizes to the apical or basolateral plasma membrane depending on the tissue type. MRP4 is a 170 kDa glycoprotein and here we show that MRP4 is simultaneously N-glycosylated at Asn746 and Asn754. Furthermore, confocal immunofluorescence studies showed that N-glycans do not affect MRP4's apical membrane localization in polarized LLC-PK1 cells or basolateral membrane localization in polarized MDCKI cells. However, vesicular transport assays showed that N-glycans differentially affect MRP4's ability to transport prostaglandin E2, but not estradiol glucuronide. Together these data indicate that N-glycosylation at Asn746 and Asn754 is not essential for plasma membrane localization of MRP4 but cause substrate-selective effects on its transport activity.

  10. Potato tuber expression of Arabidopsis WRINKLED1 increase triacylglycerol and membrane lipids while affecting central carbohydrate metabolism.

    PubMed

    Hofvander, Per; Ischebeck, Till; Turesson, Helle; Kushwaha, Sandeep K; Feussner, Ivo; Carlsson, Anders S; Andersson, Mariette

    2016-09-01

    Tuber and root crops virtually exclusively accumulate storage products in the form of carbohydrates. An exception is yellow nutsedge (Cyperus esculentus) in which tubers have the capacity to store starch and triacylglycerols (TAG) in roughly equal amounts. This suggests that a tuber crop can efficiently handle accumulation of energy dense oil. From a nutritional as well as economic aspect, it would be of interest to utilize the high yield capacity of tuber or root crops for oil accumulation similar to yellow nutsedge. The transcription factor WRINKLED1 from Arabidopsis thaliana, which in seed embryos induce fatty acid synthesis, has been shown to be a major factor for oil accumulation. WRINKLED1 was expressed in potato (Solanum tuberosum) tubers to explore whether this factor could impact tuber metabolism. This study shows that a WRINKLED1 transcription factor could induce triacylglycerol accumulation in tubers of transformed potato plants grown in field (up to 12 nmol TAG/mg dry weight, 1% of dry weight) together with a large increase in polar membrane lipids. The changes in metabolism further affected starch accumulation and composition concomitant with massive increases in sugar content.

  11. The outer membrane protein TolC from Sinorhizobium meliloti affects protein secretion, polysaccharide biosynthesis, antimicrobial resistance, and symbiosis.

    PubMed

    Cosme, Ana M; Becker, Anke; Santos, Mário R; Sharypova, Larissa A; Santos, Pedro M; Moreira, Leonilde M

    2008-07-01

    Sinorhizobium meliloti is capable of establishing a symbiotic nitrogen fixation relationship with Medicago sativa. During this process, it must cope with diverse environments and has evolved different types of transport systems that help its propagation in the plant roots. TolC protein family members are the outer-membrane components of several transport systems involved in the export of diverse molecules, playing an important role in bacterial survival. In this work, we have characterized the protein TolC from S. meliloti 2011. An insertional mutation in the tolC gene strongly affected the resistance phenotype to antimicrobial agents and induced higher susceptibility to osmotic and oxidative stresses. Immunodetection experiments and comparison of the extracellular proteins present in the supernatant of the wild-type versus tolC mutant strains showed that the calcium-binding protein ExpE1, the endoglycanase ExsH, and the product of open reading frame SMc04171, a putative hemolysin-type calcium-binding protein, are secreted by a TolC-dependent secretion system. In the absence of TolC, neither succinoglycan nor galactoglucan were detected in the culture supernatant. Moreover, S. meliloti tolC mutant induced a reduced number of nonfixing nitrogen nodules in M. sativa roots. Taken together, our results confirm the importance of TolC in protein secretion, exopolysaccharide biosynthesis, antimicrobials resistance, and symbiosis.

  12. Putative Membrane-Bound Transporters MFSD14A and MFSD14B Are Neuronal and Affected by Nutrient Availability

    PubMed Central

    Lekholm, Emilia; Perland, Emelie; Eriksson, Mikaela M.; Hellsten, Sofie V.; Lindberg, Frida A.; Rostami, Jinar; Fredriksson, Robert

    2017-01-01

    Characterization of orphan transporters is of importance due to their involvement in cellular homeostasis but also in pharmacokinetics and pharmacodynamics. The tissue and cellular localization, as well as function, is still unknown for many of the solute carriers belonging to the major facilitator superfamily (MFS) Pfam clan. Here, we have characterized two putative novel transporters MFSD14A (HIAT1) and MFSD14B (HIATL1) in the mouse central nervous system and found protein staining throughout the adult mouse brain. Both transporters localized to neurons and MFSD14A co-localized with the Golgi marker Giantin in primary embryonic cortex cultures, while MFSD14B staining co-localized with an endoplasmic retention marker, KDEL. Based on phylogenetic clustering analyses, we predict both to have organic substrate profiles, and possible involvement in energy homeostasis. Therefore, we monitored gene regulation changes in mouse embryonic primary cultures after amino acid starvations and found both transporters to be upregulated after 3 h of starvation. Interestingly, in mice subjected to 24 h of food starvation, both transporters were downregulated in the hypothalamus, while Mfsd14a was also downregulated in the brainstem. In addition, in mice fed a high fat diet (HFD), upregulation of both transporters was seen in the striatum. Both MFSD14A and MFSD14B were intracellular neuronal membrane-bound proteins, expressed in the Golgi and Endoplasmic reticulum, affected by both starvation and HFD to varying degree in the mouse brain. PMID:28179877

  13. Daptomycin inhibits cell envelope synthesis by interfering with fluid membrane microdomains

    PubMed Central

    Müller, Anna; Wenzel, Michaela; Strahl, Henrik; Grein, Fabian; Saaki, Terrens N. V.; Kohl, Bastian; Siersma, Tjalling; Bandow, Julia E.; Sahl, Hans-Georg; Schneider, Tanja; Hamoen, Leendert W.

    2016-01-01

    Daptomycin is a highly efficient last-resort antibiotic that targets the bacterial cell membrane. Despite its clinical importance, the exact mechanism by which daptomycin kills bacteria is not fully understood. Different experiments have led to different models, including (i) blockage of cell wall synthesis, (ii) membrane pore formation, and (iii) the generation of altered membrane curvature leading to aberrant recruitment of proteins. To determine which model is correct, we carried out a comprehensive mode-of-action study using the model organism Bacillus subtilis and different assays, including proteomics, ionomics, and fluorescence light microscopy. We found that daptomycin causes a gradual decrease in membrane potential but does not form discrete membrane pores. Although we found no evidence for altered membrane curvature, we confirmed that daptomycin inhibits cell wall synthesis. Interestingly, using different fluorescent lipid probes, we showed that binding of daptomycin led to a drastic rearrangement of fluid lipid domains, affecting overall membrane fluidity. Importantly, these changes resulted in the rapid detachment of the membrane-associated lipid II synthase MurG and the phospholipid synthase PlsX. Both proteins preferentially colocalize with fluid membrane microdomains. Delocalization of these proteins presumably is a key reason why daptomycin blocks cell wall synthesis. Finally, clustering of fluid lipids by daptomycin likely causes hydrophobic mismatches between fluid and more rigid membrane areas. This mismatch can facilitate proton leakage and may explain the gradual membrane depolarization observed with daptomycin. Targeting of fluid lipid domains has not been described before for antibiotics and adds another dimension to our understanding of membrane-active antibiotics. PMID:27791134

  14. Detection of liposome membrane viscosity perturbations with ratiometric molecular rotors.

    PubMed

    Nipper, Matthew E; Dakanali, Marianna; Theodorakis, Emmanuel; Haidekker, Mark A

    2011-06-01

    Molecular rotors are a form of fluorescent intramolecular charge-transfer complexes that can undergo intramolecular twisting motion upon photoexcitation. Twisted-state formation leads to non-radiative relaxation that competes with fluorescence emission. In bulk solutions, these molecules exhibit a viscosity-dependent quantum yield. On the molecular scale, the fluorescence emission is a function of the local free volume, which in turn is related to the local micro-viscosity. Membrane viscosity, and the inverse; fluidity, are characteristic terms used to describe the ease of movement withing the membrane. Often, changes in membrane viscosity govern intracellular processes and are indicative of a disease state. Molecular rotors have been used to investigate viscosity changes in liposomes and cells, but accuracy is affected by local concentration gradients and sample optical properties. We have developed self-calibrating ratiometric molecular rotors to overcome this challenge and integrated the new molecules into a DLPC liposome model exposed to the membrane-fluidizing agent propanol. We show that the ratiometric emission intensity linearly decreases with the propanol exposure and that the ratiometric intensity is widely independent of the total liposome concentration. Conversely, dye concentration inside liposomes influences the sensitivity of the system. We suggest that the new self-calibrating dyes can be used for real-time viscosity sensing in liposome systems with the advantages of lifetime measurements, but with low-cost steady-state instrumentation.

  15. Diversification of the AlpB Outer Membrane Protein of Helicobacter pylori Affects Biofilm Formation and Cellular Adhesion

    PubMed Central

    Osaki, Takako; Fukutomi, Toshiyuki; Hanawa, Tomoko; Kurata, Satoshi; Zaman, Cynthia; Hojo, Fuhito; Kamiya, Shigeru

    2016-01-01

    ABSTRACT Helicobacter pylori is one of the most common causes of bacterial infection in humans, and it forms biofilms on human gastric mucosal epithelium as well as on in vitro abiotic surfaces. Bacterial biofilm is critical not only for environmental survival but also for successful infection. We previously demonstrated that strain TK1402, which was isolated from a Japanese patient with duodenal and gastric ulcers, has high biofilm-forming ability in vitro relative to other strains. In addition, we showed that outer membrane vesicles (OMV) play an important role in biofilm formation. The aim of this study was to analyze which protein(s) in the OMV contributes to biofilm formation in TK1402. We obtained a spontaneous mutant strain derived from TK1402 lacking biofilm-forming ability. The protein profiles of the OMV were compared between this mutant strain and the wild type, and it was found that AlpB, an outer membrane protein in the OMV of the mutant strain, was markedly decreased compared to that of the wild type. Restoration of TK1402 alpB to the mutant strain fully recovered the ability to form biofilm. However, restoration with alpB from other strains demonstrated incomplete recovery of biofilm-forming ability. We therefore inferred that the variable region of AlpB (amino acid positions 121 to 146) was involved in TK1402 biofilm formation. In addition, diversification of the AlpB sequence was shown to affect the ability to adhere to AGS cells. These results demonstrate a new insight into the molecular mechanisms of host colonization by H. pylori. IMPORTANCE Bacterial biofilm is critical not only for environmental survival but also for successful infection. The mechanism of Helicobacter pylori adherence to host cells mediated by cell surface adhesins has been the focus of many studies, but little is known regarding factors involved in H. pylori biofilm formation. Our study demonstrated that AlpB plays an important role in biofilm formation and that this property

  16. Diversification of the AlpB Outer Membrane Protein of Helicobacter pylori Affects Biofilm Formation and Cellular Adhesion.

    PubMed

    Yonezawa, Hideo; Osaki, Takako; Fukutomi, Toshiyuki; Hanawa, Tomoko; Kurata, Satoshi; Zaman, Cynthia; Hojo, Fuhito; Kamiya, Shigeru

    2017-03-15

    Helicobacter pylori is one of the most common causes of bacterial infection in humans, and it forms biofilms on human gastric mucosal epithelium as well as on in vitro abiotic surfaces. Bacterial biofilm is critical not only for environmental survival but also for successful infection. We previously demonstrated that strain TK1402, which was isolated from a Japanese patient with duodenal and gastric ulcers, has high biofilm-forming ability in vitro relative to other strains. In addition, we showed that outer membrane vesicles (OMV) play an important role in biofilm formation. The aim of this study was to analyze which protein(s) in the OMV contributes to biofilm formation in TK1402. We obtained a spontaneous mutant strain derived from TK1402 lacking biofilm-forming ability. The protein profiles of the OMV were compared between this mutant strain and the wild type, and it was found that AlpB, an outer membrane protein in the OMV of the mutant strain, was markedly decreased compared to that of the wild type. Restoration of TK1402 alpB to the mutant strain fully recovered the ability to form biofilm. However, restoration with alpB from other strains demonstrated incomplete recovery of biofilm-forming ability. We therefore inferred that the variable region of AlpB (amino acid positions 121 to 146) was involved in TK1402 biofilm formation. In addition, diversification of the AlpB sequence was shown to affect the ability to adhere to AGS cells. These results demonstrate a new insight into the molecular mechanisms of host colonization by H. pyloriIMPORTANCE Bacterial biofilm is critical not only for environmental survival but also for successful infection. The mechanism of Helicobacter pylori adherence to host cells mediated by cell surface adhesins has been the focus of many studies, but little is known regarding factors involved in H. pylori biofilm formation. Our study demonstrated that AlpB plays an important role in biofilm formation and that this property depends

  17. Lipid domains in intact fiber-cell plasma membranes isolated from cortical and nuclear regions of human eye lenses of donors from different age groups.

    PubMed

    Raguz, Marija; Mainali, Laxman; O'Brien, William J; Subczynski, Witold K

    2015-03-01

    The results reported here clearly document changes in the properties and the organization of fiber-cell membrane lipids that occur with age, based on electron paramagnetic resonance (EPR) analysis of lens membranes of clear lenses from donors of age groups from 0 to 20, 21 to 40, and 61 to 80 years. The physical properties, including profiles of the alkyl chain order, fluidity, hydrophobicity, and oxygen transport parameter, were investigated using EPR spin-labeling methods, which also provide an opportunity to discriminate coexisting lipid domains and to evaluate the relative amounts of lipids in these domains. Fiber-cell membranes were found to contain three distinct lipid environments: bulk lipid domain, which appears minimally affected by membrane proteins, and two domains that appear due to the presence of membrane proteins, namely boundary and trapped lipid domains. In nuclear membranes the amount of boundary and trapped phospholipids as well as the amount of cholesterol in trapped lipid domains increased with the donors' age and was greater than that in cortical membranes. The difference between the amounts of lipids in domains uniquely formed due to the presence of membrane proteins in nuclear and cortical membranes increased with the donors' age. It was also shown that cholesterol was to a large degree excluded from trapped lipid domains in cortical membranes. It is evident that the rigidity of nuclear membranes was greater than that of cortical membranes for all age groups. The amount of lipids in domains of low oxygen permeability, mainly in trapped lipid domains, were greater in nuclear than cortical membranes and increased with the age of donors. These results indicate that the nuclear fiber cell plasma membranes were less permeable to oxygen than cortical membranes and become less permeable to oxygen with age. In clear lenses, age-related changes in the lens lipid and protein composition and organization appear to occur in ways that increase fiber

  18. Lipid Domains in Intact Fiber-Cell Plasma Membranes Isolated from Cortical and Nuclear Regions of Human Eye Lenses of Donors from Different Age Groups

    PubMed Central

    Raguz, Marija; Mainali, Laxman; O’Brien, William J.; Subczynski, Witold K.

    2015-01-01

    The results reported here clearly document changes in the properties and the organization of fiber-cell membrane lipids that occur with age, based on electron paramagnetic resonance (EPR) analysis of lens membranes of clear lenses from donors of age groups from 0 to 20, 21 to 40, and 61 to 80 years. The physical properties, including profiles of the alkyl chain order, fluidity, hydrophobicity, and oxygen transport parameter, were investigated using EPR spin-labeling methods, which also provide an opportunity to discriminate coexisting lipid domains and to evaluate the relative amounts of lipids in these domains. Fiber-cell membranes were found to contain three distinct lipid environments: bulk lipid domain, which appears minimally affected by membrane proteins, and two domains that appear due to the presence of membrane proteins, namely boundary and trapped lipid domains. In nuclear membranes the amount of boundary and trapped phospholipids as well as the amount of cholesterol in trapped lipid domains increased with the donors’ age and was greater than that in cortical membranes. The difference between the amounts of lipids in domains uniquely formed due to the presence of membrane proteins in nuclear and cortical membranes increased with the donors’ age. It was also shown that cholesterol was to a large degree excluded from trapped lipid domains in cortical membranes. It is evident that the rigidity of nuclear membranes was greater than that of cortical membranes for all age groups. The amount of lipids in domains of low oxygen permeability, mainly in trapped lipid domains, were greater in nuclear than cortical membranes and increased with the age of donors. These results indicate that the nuclear fiber cell plasma membranes were less permeable to oxygen than cortical membranes and become less permeable to oxygen with age. In clear lenses, age-related changes in the lens lipid and protein composition and organization appear to occur in ways that increase fiber

  19. Do the interfacial fluidities of cationic reverse micelles enhance with an increase in the water content?

    NASA Astrophysics Data System (ADS)

    Mali, K. S.; Dutt, G. B.

    2009-11-01

    The role of cosurfactant and water on the interfacial fluidities of reverse micelles formed with the cationic surfactant, cetyltrimethylammonium bromide (CTAB) has been examined by measuring the fluorescence anisotropies of two structurally similar ionic solutes, rhodamine 110 and fluorescein. For this purpose, reverse micellar systems with (CTAB/1-pentanol/cyclohexane/water) and without a cosurfactant (CTAB/chloroform-isooctane/water) have been chosen. In this study, the mole ratio of water to surfactant W has been varied in the region of 4-25. Experimental results indicate that the average reorientation time of the probe, which is a measure of the fluidity near the interfacial region, decreases by a factor of 1.5 and 1.4 for rhodamine 110 and fluorescein, respectively, as W goes up from 5 to 25 in CTAB/1-pentanol/cyclohexane/water reverse micellar system. In contrast, the average reorientation time, remains invariant for both the probe molecules in CTAB/chloroform-isooctane/water reverse micellar system despite an increase in W from 4 to 24. In case of CTAB/1-pentanol/cyclohexane/water reverse micellar system, the added water binds to bromide counter ions and also the hydroxyl groups of the cosurfactant, 1-pentanol, which results in an increase in the effective head group area. Such an increase in the effective head group area leads to a decrease in the packing parameter, and hence an increase in the interfacial fluidity. On the other hand, in CTAB/chloroform-isooctane/water system, the added water merely hydrates the bromide ions, thereby leaving the effective head group area unchanged. Thus, the interfacial fluidities remain invariant upon the addition of water in the absence of a cosurfactant.

  20. Effects of the cannabinoids on physical properties of brain membranes and phospholipid vesicles: fluorescence studies.

    PubMed

    Hillard, C J; Harris, R A; Bloom, A S

    1985-03-01

    The effects of four cannabinoids on the physical properties of brain synaptic plasma membranes (SPM), lipid extracts of SPM and phospholipid vesicles were evaluated using fluorescence probes. In vitro, the psychoactive cannabinoids, delta 9-tetrahydrocannabinol (delta 9-THC) and 11-hydroxyl-delta 9-tetrahydrocannabinol (11-OH-delta 9-THC) at concentrations of 1 and 3 microM decreased polarization of the fluorescence emission of 1,6-diphenyl-1,3,5-hexatriene (DPH) in SPM. At the same concentrations, cannabidiol (CBD) and cannabinol, cannabinoids devoid of marijuana-like psychoactivity, had no effect on DPH polarization. The effects of 11-OH-delta 9-THC and CBD on vesicles made from lipids extracted from SPM were identical to their effects on intact SPM. These changes in DPH polarization were not due to changes in fluorescence lifetime and indicate that, at low concentrations, the psychoactive cannabinoids increase the rotational mobility of DPH in the membrane core. In contrast, in SPM-extracted lipids, both 11-OH-delta 9-THC and CBD decreased the mobility of stearic acid with an anthroyloxy label at both the second (2-AS) and twelfth (12-AS) carbon atoms. Studies of DPH polarization in various phosphatidylcholines (PC) demonstrated that the actions of the cannabinoids were dependent on initial bilayer fluidity. 11-OH-delta 9-THC was less effective at decreasing polarization of trimethylammonium DPH (TMA-DPH), a probe of the bilayer surface, than of DPH whereas CBD affected mobility of the two probes equally. Neither CBD nor 11-OH-delta 9-THC altered DPH mobility in phosphatidylethanolamine, phosphatidylserine vesicles. These findings indicate that the psychoactive cannabinoids increase fluidity in the hydrophobic core of brain membranes and support a membrane perturbant hypothesis of the mechanism of delta 9-THC action.

  1. Effect of Melatonin and Cholesterol on the Structure of DOPC and DPPC Membranes

    SciTech Connect

    Drolle, E; Kucerka, Norbert; Hoopes, M I; Choi, Y; Katsaras, John; Karttunen, M; Leonenko, Z

    2013-01-01

    The cell membrane plays an important role in the molecular mechanism of amyloid toxicity associated with Alzheimer's disease. The membrane's chemical composition and the incorporation of small molecules, such as melatonin and cholesterol, can alter its structure and physical properties, thereby affecting its interaction with amyloid peptides. Both melatonin and cholesterol have been recently linked to amyloid toxicity. Melatonin has been shown to have a protective role against amyloid toxicity. However, the underlying molecular mechanism of this protection is still not well understood, and cholesterol's role remains controversial. We used small-angle neutron diffraction (SAND) from oriented lipid multi-layers, small-angle neutron scattering (SANS) from unilamellar vesicles experiments andMolecular Dynamics (MD) simulations to elucidate non-specific interactions of melatonin and cholesterol with 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1,2-dipalmitoyl-snglycero-3-phosphocholine (DPPC) model membranes. We conclude that melatonin decreases the thickness of both model membranes by disordering the lipid hydrocarbon chains, thus increasing membrane fluidity. This result is in stark contrast to the much accepted ordering effect induced by cholesterol, which causes membranes to thicken.

  2. Ankyrin and band 3 differentially affect expression of membrane glycoproteins but are not required for erythroblast enucleation.

    PubMed

    Ji, Peng; Lodish, Harvey F

    2012-01-27

    During late stages of mammalian erythropoiesis the nucleus undergoes chromatin condensation, migration to the plasma membrane, and extrusion from the cytoplasm surrounded by a segment of plasma membrane. Since nuclear condensation occurs in all vertebrates, mammalian erythroid membrane and cytoskeleton proteins were implicated as playing important roles in mediating the movement and extrusion of the nucleus. Here we use erythroid ankyrin deficient and band 3 knockout mouse models to show that band 3, but not ankyrin, plays an important role in regulating the level of erythroid cell membrane proteins, as evidenced by decreased cell surface expression of glycophorin A in band 3 knockout mice. However, neither band 3 nor ankyrin are required for enucleation. These results demonstrate that mammalian erythroblast enucleation does not depend on the membrane integrity generated by the ankyrin-band 3 complex.

  3. Lipid fluidity at different regions in LDL and HDL of {beta}-thalassemia/Hb E patients

    SciTech Connect

    Morales, Noppawan Phumala . E-mail: scnpm@mahidol.ac.th; Charlermchoung, Chalermkhwan; Luechapudiporn, Rataya; Yamanont, Paveena; Fucharoen, Suthat; Chantharaksri, Udom

    2006-11-24

    Atherosclerosis-related vascular complications in {beta}-thalassemia/hemoglobin E ({beta}-thal/Hb E) patients may result from iron induced oxidation of lipoproteins. To identify the specific site of oxidative damage, changes in lipid fluidity at different regions in LDL and HDL particle were investigated using two fluorescence probes and two ESR spin probes. The magnitude of increased lipid fluidity in thalassemic lipoproteins was dependent on the location of the probes. In hydrophobic region, the rotational correlation times for 16-doxyl stearic acid and DPH anisotropy were markedly changed in LDL and HDL of the patients. In the surface region, there was only a slight change in the order parameter (S) for 5-doxyl stearic acid and TMA-DPH anisotropy. Lipid fluidity at the core of LDL and HDL showed good correlation with oxidative stress markers, the ratio of CL/CO, and the level of {alpha}-tocopherol, suggesting that hydrophobic region of thalassemic lipoprotein was a target site for oxidative damage.

  4. Evaluation on the combined effect of Sesamin and Schisandra extract on blood fluidity.

    PubMed

    Tsi, Daniel; Tan, Amabel

    2008-01-27

    Several studies have demonstrated a link between blood viscosity and various forms of liver dysfunction. Therefore, we investigated the effect of liver protective herbal materials, Sesamin combined with extract of Schisandra chinensis berry (Schisandra) for its potential to improve blood fluidity in humans. Ten human subjects were recruited to study the effect of sesamin combined with schisandra extract (SCH) for two weeks on blood viscosity. Blood fluidity was measured as the transit time for 100mul of heparinized whole blood to pass through a micro-channel array setup at baseline, 1 week and 2 weeks. For safety assessment, blood biochemistry, hematology and urine analysis were taken at baseline, 1 week and 2 weeks after SCH administration. No safety concern and adverse effects were observed during the 2-week continuous intake period. Intake of SCH reduced blood passage time by 9.0% and 9.7% at 1 and 2 weeks, respectively. In conclusion, this pilot clinical study indicates that the combined administration of sesamin with schisandra extract could improve blood fluidity after 1 week of oral intake and this effect was sustained up to 2 weeks.

  5. Glutaraldehyde cross-linking of amniotic membranes affects their nanofibrous structures and limbal epithelial cell culture characteristics.

    PubMed

    Lai, Jui-Yang; Ma, David Hui-Kang

    2013-01-01

    Given that the cells can sense nanometer dimensions, the chemical cross-linking-mediated alteration in fibrillar structure of collagenous tissue scaffolds is critical to determining their cell culture performances. This article explores, for the first time, the effect of nanofibrous structure of glutaraldehyde (GTA) cross-linked amniotic membrane (AM) on limbal epithelial cell (LEC) cultivation. Results of ninhydrin assays demonstrated that the amount of new cross-links formed between the collagen chains is significantly increased with increasing the cross-linking time from 1 to 24 hours. By transmission electron microscopy, the AM treated with GTA for a longer duration exhibited a greater extent of molecular aggregation, thereby leading to a considerable increase in nanofiber diameter and resistance against collagenase degradation. In vitro biocompatibility studies showed that the samples cross-linked with GTA for 24 hours are not well-tolerated by the human corneal epithelial cell cultures. When the treatment duration is less than 6 hours, the biological tissues cross-linked with GTA for a longer time may cause slight reductions in 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt, and anti-inflammatory activities. Nevertheless, significant collagen molecular aggregation also enhances the stemness gene expression, indicating a high ability of these AM matrices to preserve the progenitors of LECs in vitro. It is concluded that GTA cross-linking of collagenous tissue materials may affect their nanofibrous structures and corneal epithelial stem cell culture characteristics. The AM treated with GTA for 6 hours holds promise for use as a niche for the expansion and transplantation of limbal epithelial progenitor cells.

  6. The Role of the Membrane-Initiated Heat Shock Response in Cancer

    PubMed Central

    Bromberg, Zohar; Weiss, Yoram

    2016-01-01

    The heat shock response (HSR) is a cellular response to diverse environmental and physiological stressors resulting in the induction of genes encoding molecular chaperones, proteases, and other proteins that are essential for protection and recovery from cellular damage. Since different perturbations cause accumulation of misfolded proteins, cells frequently encounter fluctuations in the environment which alter proteostasis. Since tumor cells use their natural adaptive mechanism of coping with stress and misfolded proteins, in recent years, the proteostasis network became a promising target for anti-tumor therapy. The membrane is the first to be affected by heat shock and therefore may be the first one to sense heat shock. The membrane also connects between the extracellular and the intracellular signals. Hence, there is a “cross talk” between the HSR and the membranes since heat shock can induce changes in the fluidity of membranes, leading to membrane lipid remodeling that occurs in several diseases such as cancer. During the last decade, a new possible therapy has emerged in which an external molecule is used that could induce membrane lipid re-organization. Since at the moment there are very few substances that regulate the HSR effectively, an alternative way has been searched to modulate chaperone activities through the plasma membrane. Recently, we suggested that the use of the membrane Transient Receptor Potential Vanilloid-1 (TRPV1) modulators regulated the HSR in cancer cells. However, the primary targets of the signal transduction pathway are yet un-known. This review provides an overview of the current literature regarding the role of HSR in membrane remodeling in cancer since a deep understanding of the membrane biology in cancer and the membrane heat sensing pathway is essential to design novel efficient therapies. PMID:27200359

  7. Interaction of Spin-Labeled Lipid Membranes with Transition Metal Ions

    PubMed Central

    2015-01-01

    The large values of spin relaxation enhancement (RE) for PC spin-labels in the phospholipid membrane induced by paramagnetic metal salts dissolved in the aqueous phase can be explained by Heisenberg spin exchange due to conformational fluctuations of the nitroxide group as a result of membrane fluidity, flexibility of lipid chains, and, possibly, amphiphilic nature of the nitroxide label. Whether the magnetic interaction occurs predominantly via Heisenberg spin exchange (Ni) or by the dipole–dipole (Gd) mechanism, it is essential for the paramagnetic ion to get into close proximity to the nitroxide moiety for efficient RE. For different salts of Ni the RE in phosphatidylcholine membranes follows the anionic Hofmeister series and reflects anion adsorption followed by anion-driven attraction of paramagnetic cations on the choline groups. This adsorption is higher for chaotropic ions, e.g., perchlorate. (A chaotropic agent is a molecule in water solution that can disrupt the hydrogen bonding network between water molecules.) However, there is no anionic dependence of RE for model membranes made from negatively charged lipids devoid of choline groups. We used Ni-induced RE to study the thermodynamics and electrostatics of ion/membrane interactions. We also studied the effect of membrane composition and the phase state on the RE values. In membranes with cholesterol a significant difference is observed between PC labels with nitroxide tethers long enough vs not long enough to reach deep into the membrane hydrophobic core behind the area of fused cholesterol rings. This study indicates one must be cautious in interpreting data obtained by PC labels in fluid membranes in terms of probing membrane properties at different immersion depths when it can be affected by paramagnetic species at the membrane surface. PMID:26490692

  8. Interaction of Spin-Labeled Lipid Membranes with Transition Metal Ions.

    PubMed

    Dzikovski, Boris; Livshits, Vsevolod; Freed, Jack

    2015-10-22

    The large values of spin relaxation enhancement (RE) for PC spin-labels in the phospholipid membrane induced by paramagnetic metal salts dissolved in the aqueous phase can be explained by Heisenberg spin exchange due to conformational fluctuations of the nitroxide group as a result of membrane fluidity, flexibility of lipid chains, and, possibly, amphiphilic nature of the nitroxide label. Whether the magnetic interaction occurs predominantly via Heisenberg spin exchange (Ni) or by the dipole-dipole (Gd) mechanism, it is essential for the paramagnetic ion to get into close proximity to the nitroxide moiety for efficient RE. For different salts of Ni the RE in phosphatidylcholine membranes follows the anionic Hofmeister series and reflects anion adsorption followed by anion-driven attraction of paramagnetic cations on the choline groups. This adsorption is higher for chaotropic ions, e.g., perchlorate. (A chaotropic agent is a molecule in water solution that can disrupt the hydrogen bonding network between water molecules.) However, there is no anionic dependence of RE for model membranes made from negatively charged lipids devoid of choline groups. We used Ni-induced RE to study the thermodynamics and electrostatics of ion/membrane interactions. We also studied the effect of membrane composition and the phase state on the RE values. In membranes with cholesterol a significant difference is observed between PC labels with nitroxide tethers long enough vs not long enough to reach deep into the membrane hydrophobic core behind the area of fused cholesterol rings. This study indicates one must be cautious in interpreting data obtained by PC labels in fluid membranes in terms of probing membrane properties at different immersion depths when it can be affected by paramagnetic species at the membrane surface.

  9. Sucrose delays membrane deterioration of chrysanthemum flowers induced by gamma-rays

    NASA Astrophysics Data System (ADS)

    Kikuchi, O. K.; Todoriki, S.; Hayashi, T.

    1998-06-01

    Fluidity of the flower membranes of cut chrysanthemums ( Dendranthema grandiflorum Kitamura) decreased soon after gamma-irradiation at 750Gy and continued to decrease during storage following irradiation. Holding chrysanthemum cut inflorescence in 2% sucrose suppressed the decrease. The results suggest that sugars reduce radiation-induced physiological deterioration of chrysanthemum flower membranes.

  10. Interaction forces and membrane charge tunability: Oleic acid containing membranes in different pH conditions.

    PubMed

    Kurniawan, James; Suga, Keishi; Kuhl, Tonya L

    2017-02-01

    Oleic acid is known to interact with saturated lipid molecules and increase the fluidity of gel phase lipid membranes. In this work, the thermodynamic properties of mixed monolayers of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and oleic acid at the air-water interface were determined using Langmuir isotherms. The isotherm study revealed an attractive interaction between oleic acid and DPPC. The incorporation of oleic acid also monotonically decreased the elastic modulus of the monolayer indicative of higher fluidity with increasing oleic acid content. Using the surface force apparatus, intermembrane force-distance profiles were obtained for substrate supported DPPC membranes containing 30mol% oleic acid at pH5.8 and 7.4. Three different preparation conditions resulted in distinct force profiles. Membranes prepared in pH5.8 subphase had a low number of nanoscopic defects ≤1% and an adhesion magnitude of ~0.6mN/m. A slightly higher defect density of 1-4% was found for membranes prepared in a physiological pH7.4 subphase. The presence of the exposed hydrophobic moieties resulted in a higher adhesion magnitude of 2.9mN/m. Importantly, at pH7.4, some oleic acid deprotonates resulting in a long-range electrostatic repulsion. Even though oleic acid increased the DPPC bilayer fluidity and the number of defects, no membrane restructuring was observed indicating that the system maintained a stable configuration.

  11. The absence of chlorophyll b affects lateral mobility of photosynthetic complexes and lipids in grana membranes of Arabidopsis and barley chlorina mutants.

    PubMed

    Tyutereva, Elena V; Evkaikina, Anastasiia I; Ivanova, Alexandra N; Voitsekhovskaja, Olga V

    2017-04-05

    The lateral mobility of integral components of thylakoid membranes, such as plastoquinone, xanthophylls, and pigment-protein complexes, is critical for the maintenance of efficient light harvesting, high rates of linear electron transport, and successful repair of damaged photosystem II (PSII). The packaging of the photosynthetic pigment-protein complexes in the membrane depends on their size and stereometric parameters which in turn depend on the composition of the complexes. Chlorophyll b (Chlb) is an important regulator of antenna size and composition. In this study, the lateral mobility (the mobile fraction size) of pigment-protein complexes and lipids in grana membranes was analyzed in chlorina mutants of Arabidopsis and barley lacking Chlb. In the Arabidopsis ch1-3 mutant, diffusion of membrane lipids decreased as compared to wild-type plants, but the diffusion of photosynthetic complexes was not affected. In the barley chlorina f2 3613 mutant, the diffusion of pigment-protein complexes significantly decreased, while the diffusion of lipids increased, as compared to wild-type plants. We propose that the size of the mobile fractions of pigment-protein complexes in grana membranes in vivo is higher than reported previously. The data are discussed in the context of the protein composition of antennae, characteristics of the plastoquinone pool, and production of reactive oxygen species in leaves of chlorina mutants.

  12. Membrane remodeling by the M2 amphipathic helix drives influenza virus membrane scission

    PubMed Central

    Martyna, Agnieszka; Bahsoun, Basma; Badham, Matthew D.; Srinivasan, Saipraveen; Howard, Mark J.; Rossman, Jeremy S.

    2017-01-01

    Membrane scission is a crucial step in all budding processes, from endocytosis to viral budding. Many proteins have been associated with scission, though the underlying molecular details of how scission is accomplished often remain unknown. Here, we investigate the process of M2-mediated membrane scission during the budding of influenza viruses. Residues 50–61 of the viral M2 protein bind membrane and form an amphipathic α-helix (AH). Membrane binding requires hydrophobic interactions with the lipid tails but not charged interactions with the lipid headgroups. Upon binding, the M2AH induces membrane curvature and lipid ordering, constricting and destabilizing the membrane neck, causing scission. We further show that AHs in the cellular proteins Arf1 and Epsin1 behave in a similar manner. Together, they represent a class of membrane-induced AH domains that alter membrane curvature and fluidity, mediating the scission of constricted membrane necks in multiple biological pathways. PMID:28317901

  13. Mediterranean-style diet effect on the structural properties of the erythrocyte cell membrane of hypertensive patients: the Prevencion con Dieta Mediterranea Study.

    PubMed

    Barceló, Francisca; Perona, Javier S; Prades, Jesús; Funari, Sérgio S; Gomez-Gracia, Enrique; Conde, Manuel; Estruch, Ramon; Ruiz-Gutiérrez, Valentina

    2009-11-01

    A currently ongoing randomized trial has revealed that the Mediterranean diet, rich in virgin olive oil or nuts, reduces systolic blood pressure in high-risk cardiovascular patients. Here, we present a structural substudy to assess the effect of a Mediterranean-style diet supplemented with nuts or virgin olive oil on erythrocyte membrane properties in 36 hypertensive participants after 1 year of intervention. Erythrocyte membrane lipid composition, structural properties of reconstituted erythrocyte membranes, and serum concentrations of inflammatory markers are reported. After the intervention, the membrane cholesterol content decreased, whereas that of phospholipids increased in all of the dietary groups; the diminishing cholesterol:phospholipid ratio could be associated with an increase in the membrane fluidity. Moreover, reconstituted membranes from the nuts and virgin olive oil groups showed a higher propensity to form a nonlamellar inverted hexagonal phase structure that was related to an increase in phosphatidylethanolamine lipid class. These data suggest that the Mediterranean-style diet affects the lipid metabolism that is altered in hypertensive patients, influencing the structural membrane properties. The erythrocyte membrane modulation described provides insight in the structural bases underlying the beneficial effect of a Mediterranean-style diet in hypertensive subjects.

  14. Influence of membrane lipid composition on flavonoid-membrane interactions: Implications on their biological activity.

    PubMed

    Selvaraj, Stalin; Krishnaswamy, Sridharan; Devashya, Venkappayya; Sethuraman, Swaminathan; Krishnan, Uma Maheswari

    2015-04-01

    The membrane interactions and localization of flavonoids play a vital role in altering membrane-mediated cell signaling cascades as well as influence the pharmacological activities such as anti-tumour, anti-microbial and anti-oxidant properties of flavonoids. Various techniques have been used to investigate the membrane interaction of flavonoids. These include partition coefficient, fluorescence anisotropy, differential scanning calorimetry, NMR spectroscopy, electrophysiological methods and molecular dynamics simulations. Each technique will provide specific information about either alteration of membrane fluidity or localization of flavonoids within the lipid bilayer. Apart from the diverse techniques employed, the concentrations of flavonoids and lipid membrane composition employed in various studies reported in literature also are different and together these variables contribute to diverse findings that sometimes contradict each other. This review highlights different techniques employed to investigate the membrane interaction of flavonoids with special emphasis on erythrocyte model membrane systems and their significance in understanding the nature and extent of flavonoid-membrane interactions. We also attempt to correlate the membrane localization and alteration in membrane fluidity with the biological activities of flavonoids such as anti-oxidant, anti-cancer and anti-microbial properties.

  15. Purinergically induced membrane fluidization in ciliary cells: characterization and control by calcium and membrane potential.

    PubMed

    Alfahel, E; Korngreen, A; Parola, A H; Priel, Z

    1996-02-01

    To examine the role of membrane dynamics in transmembrane signal transduction, we studied changes in membrane fluidity in mucociliary tissues from frog palate and esophagus epithelia stimulated by extracellular ATP. Micromolar concentrations of ATP induced strong changes in fluorescence polarization, possibly indicating membrane fluidization. This effect was dosage dependent, reaching a maximum at 10-microM ATP. It was dependent on the presence of extracellular Ca2+ (or Mg2+), though it was insensitive to inhibitors of voltage-gated calcium channels. It was inhibited by thapsigargin and by ionomycin (at low extracellular Ca2+ concentration), both of which deplete Ca2+ stores. It was inhibited by the calcium-activated potassium channel inhibitors quinidine, charybdotoxin, and apamine and was reduced considerably by replacement of extracellular Na+ with K+. Hyperpolarization, or depolarization, of the mucociliary membrane induced membrane fluidization. The degree of membrane fluidization depended on the degree of hyperpolarization or depolarization of the ciliary membrane potential and was considerably lower than the effect induced by extracellular ATP. These results indicate that appreciable membrane fluidization induced by extracellular ATP depends both on an increase in intracellular Ca2+, mainly from its internal stores, and on hyperpolarization of the membrane. Calcium-dependent potassium channels couple the two effects. In light of recent results on the enhancement of ciliary beat frequency, it would appear that extracellular ATP-induced changes both in ciliary beat frequency and in membrane fluidity are triggered by similar signal transduction pathways.

  16. Vascular endothelial cell membranes differentiate between stretch and shear stress through transitions in their lipid phases.

    PubMed

    Yamamoto, Kimiko; Ando, Joji

    2015-10-01

    Vascular endothelial cells (ECs) respond to the hemodynamic forces stretch and shear stress by altering their morphology, functions, and gene expression. However, how they sense and differentiate between these two forces has remained unknown. Here we report that the plasma membrane itself differentiates between stretch and shear stress by undergoing transitions in its lipid phases. Uniaxial stretching and hypotonic swelling increased the lipid order of human pulmonary artery EC plasma membranes, thereby causing a transition from the liquid-disordered phase to the liquid-ordered phase in some areas, along with a decrease in membrane fluidity. In contrast, shear stress decreased the membrane lipid order and increased membrane fluidity. A similar increase in lipid order occurred when the artificial lipid bilayer membranes of giant unilamellar vesicles were stretched by hypotonic swelling, indicating that this is a physical phenomenon. The cholesterol content of EC plasma membranes significantly increased in response to stretch but clearly decreased in response to shear stress. Blocking these changes in the membrane lipid order by depleting membrane cholesterol with methyl-β-cyclodextrin or by adding cholesterol resulted in a marked inhibition of the EC response specific to stretch and shear stress, i.e., phosphorylation of PDGF receptors and phosphorylation of VEGF receptors, respectively. These findings indicate that EC plasma membranes differently respond to stretch and shear stress by changing their lipid order, fluidity, and cholesterol content in opposite directions and that these changes in membrane physical properties are involved in the mechanotransduction that activates membrane receptors specific to each force.

  17. Ageing-related changes in Mycoplasma canadense membranes.

    PubMed

    Muñoz, G E; Sotomayor, C P

    1992-01-01

    Fluidity and composition of cell membranes during progression of Mycoplasma canadense cultures grown in a serum-free medium was assessed. The fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene at 25 degrees C of intact cells and liposomes in the exponential and stationary phases of growth was compared. A decrease in fluidity and an increase in the ratio of saturated to unsaturated fatty acids was detected in cell membranes on aging. Nevertheless, membrane density remained unaltered although the molar ratio of cholesterol to phospholipids decreased. It is proposed that the increase in lipid order is primarily due to the increase in the ratio of saturated to unsaturated membrane fatty acids, being the diminished molar ratio of cholesterol to phospholipids involved in the reduced unsaturated fatty acid uptake.

  18. Carotenoids in DPPC vesicles: membrane dynamics

    NASA Astrophysics Data System (ADS)

    Socaciu, Carmen; Lausch, Carsten; Diehl, Horst A.

    1999-09-01

    Incorporation of carotenoids into membranes is supposed to change their physical properties with consequences to signal transduction and membrane protein activities. Here the physical parameters membrane fluidity, micropolarity and anisotropy are considered and measured in multilamellar and unilamellar vesicles of dipalmitoylphosphatidyicholine (DPPC) after incorporation of 1, 2.5 and 5 mol% β-carotene, lutein, zeaxanthin, canthaxanthin, or astaxhanthin using 4 mol% pyrene or 1 μM 1,6-diphenyl-1,3,5-hexatriene (DPH) as fluorescent labels. Contrary to other investigations, no significant change in membrane fluidity (as evaluated by the pyrene excimer method) can be found. But a change of micropolarity in the pyrene label environment is obtained from the pyrene monomer fluorescence emission fine structure after incorporation of carotenoids. The membrane anisotropy is enhanced significantly only by those carotenoids which incorporate worst into the membrane. This leads to the hypothesis that carotenoid incorporation into membranes is governed not only by carotenoid polarity hut also by their ability to change membrane anisotropy.

  19. Imp2, the PSTPIP homolog in fission yeast, affects sensitivity to the immunosuppressant FK506 and membrane trafficking in fission yeast

    SciTech Connect

    Kita, Ayako; Higa, Mari; Doi, Akira; Satoh, Ryosuke; Sugiura, Reiko

    2015-02-13

    Cytokinesis is a highly ordered process that divides one cell into two cells, which is functionally linked to the dynamic remodeling of the plasma membrane coordinately with various events such as membrane trafficking. Calcineurin is a highly conserved serine/threonine protein phosphatase, which regulates multiple biological functions, such as membrane trafficking and cytokinesis. Here, we isolated imp2-c3, a mutant allele of the imp2{sup +} gene, encoding a homolog of the mouse PSTPIP1 (proline-serine-threonine phosphatase interacting protein 1), using a genetic screen for mutations that are synthetically lethal with calcineurin deletion in fission yeast. The imp2-c3 mutants showed a defect in cytokinesis with multi-septated phenotypes, which was further enhanced upon treatment with the calcineurin inhibitor FK506. Notably, electron micrographs revealed that the imp2-c3 mutant cells accumulated aberrant multi-lamella Golgi structures and putative post-Golgi secretory vesicles, and exhibited fragmented vacuoles in addition to thickened septa. Consistently, imp2-c3 mutants showed a reduced secretion of acid phosphatase and defects in vacuole fusion. The imp2-c3 mutant cells exhibited a weakened cell wall, similar to the membrane trafficking mutants identified in the same genetic screen such as ypt3-i5. These findings implicate the PSTPIP1 homolog Imp2 in Golgi/vacuole function, thereby affecting various cellular processes, including cytokinesis and cell integrity. - Highlights: • We isolated imp2-c3, in a synthetic lethal screen with calcineurin in fission yeast. • The imp2{sup +} gene encodes a component of the actin contractile ring similar to Cdc15. • The imp2-c3 mutants showed defects in cytokinesis, which were exacerbated by FK506. • The imp2-c3 mutants were defective in membrane trafficking and cell wall integrity. • Our study revealed a novel role for Imp2 in the Golgi/vacuolar membrane trafficking.

  20. Fluidity: a fully-unstructured adaptive mesh computational framework for geodynamics

    NASA Astrophysics Data System (ADS)

    Kramer, S. C.; Davies, D.; Wilson, C. R.

    2010-12-01

    Fluidity is a finite element, finite volume fluid dynamics model developed by the Applied Modelling and Computation Group at Imperial College London. Several features of the model make it attractive for use in geodynamics. A core finite element library enables the rapid implementation and investigation of new numerical schemes. For example, the function spaces used for each variable can be changed allowing properties of the discretisation, such as stability, conservation and balance, to be easily varied and investigated. Furthermore, unstructured, simplex meshes allow the underlying resolution to vary rapidly across the computational domain. Combined with dynamic mesh adaptivity, where the mesh is periodically optimised to the current conditions, this allows significant savings in computational cost over traditional chessboard-like structured mesh simulations [1]. In this study we extend Fluidity (using the Portable, Extensible Toolkit for Scientific Computation [PETSc, 2]) to Stokes flow problems relevant to geodynamics. However, due to the assumptions inherent in all models, it is necessary to properly verify and validate the code before applying it to any large-scale problems. In recent years this has been made easier by the publication of a series of ‘community benchmarks’ for geodynamic modelling. We discuss the use of several of these to help validate Fluidity [e.g. 3, 4]. The experimental results of Vatteville et al. [5] are then used to validate Fluidity against laboratory measurements. This test case is also used to highlight the computational advantages of using adaptive, unstructured meshes - significantly reducing the number of nodes and total CPU time required to match a fixed mesh simulation. References: 1. C. C. Pain et al. Comput. Meth. Appl. M, 190:3771-3796, 2001. doi:10.1016/S0045-7825(00)00294-2. 2. B. Satish et al. http://www.mcs.anl.gov/petsc/petsc-2/, 2001. 3. Blankenbach et al. Geophys. J. Int., 98:23-28, 1989. 4. Busse et al. Geophys

  1. The absence of myristic acid decreases membrane binding of p60src but does not affect tyrosine protein kinase activity.

    PubMed Central

    Buss, J E; Kamps, M P; Gould, K; Sefton, B M

    1986-01-01

    We have constructed two point mutants of Rous sarcoma virus in which the amino-terminal glycine residue of the transforming protein, p60src, was changed to an alanine or a glutamic acid residue. Both mutant proteins failed to become myristylated and, more importantly, no longer transformed cells. The lack of transformation could not be attributed to defects in the catalytic activity of the mutant p60src proteins. In vitro phosphorylation of the peptide angiotensin or of the cellular substrate proteins enolase and p36 revealed no significant differences in the Km or specific activity of the mutant and wild-type p60src proteins. However, when cellular fractions were prepared, less than 12% of the nonmyristylated p60src proteins was bound to membranes. In contrast, more than 82% of the wild-type protein was associated with membranes. Wild-type p60src was phosphorylated by protein kinase C, a protein kinase which associates with membranes when activated. The mutant proteins were not. This finding supports the idea that within the intact cell the nonmyristylated p60src proteins are cytoplasmic and suggests that this apparent solubility is not an artifact of the cell fractionation procedure. The myristyl groups of p60src apparently encourages a tight association between protein and membranes and, by determining the cellular location of the enzyme, allows transformation to occur. Images PMID:3009860

  2. Removal from the membrane affects the interaction of rat osseous plate ecto-nucleosidetriphosphate diphosphohydrolase-1 with substrates and ions.

    PubMed

    Garçon, Daniela P; Masui, Douglas C; Furriel, Rosa P M; Leone, Francisco A

    2008-01-01

    We have characterized the kinetic properties of ectonucleoside triphosphate diphosphohydrolase 1 (E-NTPDase1) from rat osseous plate membranes. A novel finding of the present study is that the solubilized enzyme shows high- and low-affinity sites for the substrate in contrast with a single substrate site for the membrane-bound enzyme. In addition, contrary to the Michaelian chraracteristics of the membrane-bound enzyme, the site-site interactions after solubilization with 0.5% digitonin plus 0.1% lysolecithin resulted in a less active ectonucleoside triphosphate diphosphohydrolase, showing activity of about 398.3 nmol Pi min(-1) mg(-1). The solubilized enzyme has M (r) of 66-72 kDa, and its catalytic efficiency was significantly increased by magnesium and calcium ions; but the ATP/ADP activity ratio was always <2.0. Partial purification and kinetic characterization of the rat osseous plate E-NTPDase1 in a solubilized form may lead to a better understanding of a possible function of the enzyme as a modulator of nucleotidase activity or purinergic signaling in matrix vesicle membranes. The simple procedure to obtain the enzyme in a solubilized form may also be attractive for comparative studies of particular features of the active sites from this and other ATPases.

  3. Chronic kidney disease predicts impaired membrane microviscosity of red blood cells in hypertensive and normotensive subjects.

    PubMed

    Tsuda, Kazushi

    2013-01-01

    Current evidence indicates that abnormalities in physical properties of the cell membranes may be strongly linked to hypertension and other circulatory disorders. Recent studies have shown that chronic kidney disease (CKD) might be a risk factor for cardiovascular and cerebrovascular outcomes. The purpose of the present study was to examine the possible relationship between kidney function and membrane fluidity (a reciprocal value of membrane microviscosity) of red blood cells (RBCs) in hypertensive and normotensive subjects using an electron spin resonance (ESR) and spin-labeling method. The order parameter (S) for the ESR spin-label agent (5-nitroxide stearate) in RBC membranes was significantly higher in hypertensive subjects than in normotensive subjects, indicating that membrane fluidity was decreased in hypertension. The order parameter (S) of RBCs was inversely correlated with estimated glomerular filtration rate (eGFR), suggesting that a decreased eGFR value might be associated with reduced membrane fluidity of RBCs. Multivariate regression analysis also demonstrated that, after adjustment for general risk factors, eGFR might be a significant predictor of membrane fluidity of RBCs. The reduced levels of both membrane fluidity of RBCs and eGFR were associated with increased plasma 8-iso-prostaglandin F2α (an index of oxidative stress) and decreased plasma nitric oxide (NO)-metabolites, suggesting that kidney function could be a determinant of membrane microviscosity of RBCs, at least in part, via oxidative stress- and NO-dependent mechanisms. The ESR study suggests that CKD might have a close correlation with impaired rheologic behavior of RBCs and microcirculatory disorders in hypertensive subjects.

  4. Gender and chronological age affect erythrocyte membrane oxidative indices in citrate phosphate dextrose adenine-formula 1 (CPDA-1) blood bank storage condition.

    PubMed

    Erman, Hayriye; Aksu, Uğur; Belce, Ahmet; Atukeren, Pınar; Uzun, Duygu; Cebe, Tamer; Kansu, Ahmet D; Gelişgen, Remisa; Uslu, Ezel; Aydın, Seval; Çakatay, Ufuk

    2016-07-01

    It is well known that in vitro storage lesions lead to membrane dysfunction and decreased number of functional erythrocytes. As erythrocytes get older, in storage media as well as in peripheral circulation, they undergo a variety of biochemical changes. In our study, the erythrocytes with different age groups in citrate phosphate dextrose adenine-formula 1 (CPDA-1) storage solution were used in order to investigate the possible effect of gender factor on oxidative damage. Oxidative damage biomarkers in erythrocyte membranes such as ferric reducing antioxidant power, pro-oxidant-antioxidant balance, protein-bound advance glycation end products, and sialic acid were analyzed. Current study reveals that change in membrane redox status during blood-bank storage condition also depends on both gender depended homeostatic factors and the presence of CPDA-1. During the storage period in CPDA-1, erythrocytes from the male donors are mostly affected by free radical-mediated oxidative stress but erythrocytes obtained from females are severely affected by glyoxidative stress.

  5. Enterococcus faecalis plasmid pAD1-encoded Fst toxin affects membrane permeability and alters cellular responses to lantibiotics.

    PubMed

    Weaver, Keith E; Weaver, Dariel M; Wells, Carol L; Waters, Christopher M; Gardner, Marshall E; Ehli, Erik A

    2003-04-01

    Fst is a peptide toxin encoded by the par toxin-antitoxin stability determinant of Enterococcus faecalis plasmid pAD1. Intracellular overproduction of Fst resulted in simultaneous inhibition of all cellular macromolecular synthesis concomitant with cell growth inhibition and compromised the integrity of the cell membrane. Cells did not lyse or noticeably leak intracellular contents but had specific defects in chromosome partitioning and cell division. Extracellular addition of synthetic Fst had no effect on cell growth. Spontaneous Fst-resistant mutants had a phenotype consistent with changes in membrane composition. Interestingly, overproduction of Fst sensitized cells to the lantibiotic nisin, and Fst-resistant mutants were cross-resistant to nisin and the pAD1-encoded cytolysin.

  6. The tolC locus of Escherichia coli affects the expression of three major outer membrane proteins.

    PubMed Central

    Morona, R; Reeves, P

    1982-01-01

    tolC mutants, which are resistant to colicin E1 and also highly sensitive to detergents and dyes, were shown to lack the OmpF outer membrane protein. There was little effect on transcription as judged by the use of an ompF-lac operon fusion strain, and the tolC effect was probably due to a post-transcriptional effect. The NmpC protein and protein 2 were also tolC dependent. Images PMID:6281230

  7. Ice slurry cooling research: Microscale study of ice particles characteristics, role of freezing point depressant, and influence on slurry fluidity

    SciTech Connect

    Hayashi, K.; Kasza, K.

    2000-05-03

    The influences of freezing-point-depressants on ice slurry characteristics in the form of ice slurry fluidity and on the microscale ice particle features are studied. The results identify microscale features of ice particles such as surface roughness that greatly influence slurry fluidity that are altered favorably by the use of a freezing point depressant. The engineering of a workable and efficient ice slurry cooling system depends very strongly on the characteristics of the individual ice particles in the slurry and, in turn, on the method of ice production. Findings from this study provide guidance on the fluidity and handleability of slurry produced by several methods currently under development and already many achieved.

  8. Thyroid status affects membranes susceptibility to free radicals and oxidative balance in skeletal muscle of Muscovy ducklings (Cairina moschata).

    PubMed

    Rey, Benjamin; Romestaing, Caroline; Bodennec, Jacques; Dumet, Adeline; Fongy, Anaïs; Duchamp, Claude; Roussel, Damien

    2014-10-01

    Thyroid hormones (TH) are major contributor to oxidative stress in mammals because they (1) stimulate reactive oxygen species generation (ROS), (2) impair antioxidant defenses, and (3) increase the susceptibility to free radicals of most tissues. Unlike mammals, THs seem to diminish mitochondrial ROS while they have limited effect on the antioxidant machinery in birds. However, how THs modify the susceptibility to ROS has never been explored in an avian model, and very little is known about their effect on oxidative balance in birds. Therefore, the objective of our study was to examine the effect of chronic pharmacological hypo- and hyperthyroidism on (i) the susceptibility of mitochondrial membranes to ROS; and (ii) the level of oxidative stress assessed by measuring oxidative damage to lipids, nucleic acids and proteins in the gastrocnemius muscle of ducklings. We show that hypothyroidism had no effect on the susceptibility of mitochondrial membranes to free radicals. Hypothyroid ducklings had lower oxidized lipids (-31%) and DNA (-25%) but a similar level of protein carbonylation relative to controls. Conversely, mitochondrial membranes of hyperthyroid ducklings exhibited higher unsaturation (+12%) and peroxidation (+31%) indexes than in controls indicating a greater susceptibility to free radicals. However, hyperthyroid ducklings exhibited more oxidative damages on proteins (+67%) only, whereas lipid damages remained unchanged, and there was a slight reduction (-15%) in damages to DNA compared to euthyroid controls. Our results indicate that birds and mammals present fundamental differences in their oxidative stress response to thyroid status.

  9. How pulse modes affect proton-barriers and anion-exchange membrane mineral fouling during consecutive electrodialysis treatments.

    PubMed

    Cifuentes-Araya, Nicolás; Pourcelly, Gérald; Bazinet, Laurent

    2013-02-15

    Mineral fouling of cation-exchange membrane (CEM) was recently reduced by pulsed electric fields (PEFs) during the electrodialysis (ED) of solutions containing high Mg(2+)/Ca(2+) ratios. However, a fouling layer appeared on the diluate side of anion-exchange membrane (AEM) once the pause lapse surpassed certain duration. Recent studies presented a multilayer mineral growth on CEM, but the case of AEM needs yet to be cleared. The current study reveals the mechanisms involved in AEM fouling growth when applying pulse modes of current in comparison with dc current. The results showed that dc current generated steady proton barriers given by water splitting at AEM interfaces that impeded fouling on both membrane sides. The higher frequency of PEF ratio 1 (Ton/Toff=10s/10s) acted removing completely an initial mineral deposit on the concentrate side of AEM, keeping it clean after two and three consecutive runs. Particularly, an undesirable brucite layer was formed on the AEM-diluate side for longer pause lapses as for a PEF ratio 0.3 (Ton/Toff=10s/33.3s) current regime. This structure caused violent water splitting resulting in amorphous magnesium hydroxide formation and consequently in fouling precipitation on the concentrate side during a third run through current exaltation.

  10. Religion and Sexual Identity Fluidity in a National Three-Wave Panel of U.S. Adults.

    PubMed

    Scheitle, Christopher P; Wolf, Julia Kay

    2017-03-29

    Research has shown that cross-sectional estimates of sexual identities overlook fluidity in those identities. Research has also shown that social factors, such as competing identities, can influence sexual identity fluidity. We contributed to this literature in two ways. First, we utilized a representative panel of US adults (N = 1034) surveyed in 2010, 2012, and 2014 by the General Social Survey. The addition of a third observation allowed us to examine more complexity in sexual identity fluidity. We found that 2.40% of US adults reported at least one change in sexual identity across the 4 years, with 1.59% reporting one change and 0.81% reporting two changes. Our second contribution came from examining the role of religion, as past research has suggested that religion can destabilize and prolong sexual identity development. We found that lesbian or gay individuals (N = 17), bisexuals (N = 15), and females (N = 585) showed more sexual identity fluidity compared to heterosexuals (N = 1003) and males (N = 450), respectively. Marital status, age, race, and education did not have significant associations with sexual identity fluidity. Regarding the role of religion, we found that participants identifying as more religious in Wave 1 showed more fluidity in sexual identity across later observations. Further analysis showed that higher levels of religiosity make it more likely that lesbian or gay individuals will be fluid in sexual identity, but this is not the case for heterosexual individuals. This finding reinforces past qualitative research that has suggested that religion can extend or complicate sexual minorities' identity development.

  11. Tespa1 is a novel component of mitochondria-associated endoplasmic reticulum membranes and affects mitochondrial calcium flux.

    PubMed

    Matsuzaki, Hiroshi; Fujimoto, Takahiro; Tanaka, Masatoshi; Shirasawa, Senji

    2013-04-12

    Regulation of intracellular Ca(2+) concentration is critical in numerous biological processes. Inositol 1,4,5-trisphosphate receptor (IP3R) functions as the Ca(2+) release channel on endoplasmic reticulum (ER) membranes. Much attention has been dedicated to mitochondrial Ca(2+) uptake via mitochondria-associated ER membranes (MAM) which is involved in intracellular Ca(2+) homeostasis; however, the molecular mechanisms that link the MAM to mitochondria still remain elusive. We previously reported that Tespa1 (thymocyte-expressed, positive selection-associated gene 1) expressed in lymphocytes physically interacts with IP3R. In this study, we first performed double-immunocytochemical staining of Tespa1 with a mitochondrial marker or an ER marker on an acute T lymphoblastic leukemia cell line, Jurkat cells, by using anti-ATP synthase or anti-calnexin antibody, respectively, and demonstrated that Tespa1 was localized very close to mitochondria and the Tespa1 localization was overlapped with restricted portion of ER. Next, we examined the effects of Tespa1 on the T cell receptor (TCR) stimulation-induced Ca(2+) flux by using Ca(2+) imaging in Jurkat cells. Reduction of Tespa1 protein by Tespa1-specific siRNA diminished TCR stimulation-induced Ca(2+) flux into both mitochondria and cytoplasm through the analyses of the mitochondrial Ca(2+) indicator (Rhod-2) and the cytoplasmic Ca(2+) indicator (Fluo-4), respectively. Furthermore, co-immunoprecipitation assay in HEK293 cells revealed that exogenous Tespa1 protein physically interacted with a MAM-associated protein, GRP75 (glucose-regulated protein 75), but not with an outer mitochondrial membrane protein, VDAC1 (voltage-dependent anion channel 1). All these results suggested that Tespa1 will participate in the molecular link between IP3R-mediated Ca(2+) release and mitochondrial Ca(2+) uptake in the MAM compartment.

  12. Fluorescence and polarization imaging of membrane dynamics in living cells

    NASA Astrophysics Data System (ADS)

    Wagner, M.; Weber, P.; Bruns, T.; Strauss, W. S. L.; Schneckenburger, H.

    2009-02-01

    Methods of wide field fluorescence microscopy for measuring membrane dynamics in living cells are described. These methods are based on laser pulse excitation of the membrane marker 6-dodecanoyl-2-dimethylamino naphthalene (laurdan) whose emission spectra, fluorescence decay kinetics and anisotropies are sensitive to membrane stiffness and fluidity. Plasma membranes are selected by illumination with an evanescent electromagnetic field and distinguished from intracellular membranes assessed by whole cell illumination. While fluorescence spectra of laurdan appeared red-shifted with decreasing membrane stiffness, fluorescence anisotropy and rotational relaxation times were reduced with increasing membrane fluidity. Membrane stiffness was found to increase with decreasing temperature and increasing amounts of cholesterol. In addition, membrane stiffness of the plasma membrane was always higher than that of intracellular membranes. These effects may have some influence on pathogenesis of certain diseases, uptake of pharmaceutical agents or cell aging. Present experiments are limited to fluorescence microscopy with total internal reflection (TIR) or epi-illumination, but corresponding methods can also be used for screening of larger cell collectives, e.g. in microtiter plates.

  13. Free to Be You and Me: Normal Gender-Role Fluidity--Commentary on Diane Ehrensaft's "Listening and Learning from Gender-Nonconforming Children".

    PubMed

    Knight, Rona

    2014-01-01

    This paper suggests that gender role fluidity is a normal self state throughout development. It discusses the nonlinear progression of gender role identity that is constantly fluid and reactive to biological, environmental, and psychological changes. Given the normal fluidity of gender role identity, it argues that giving puberty blockers to young children is against the best interests of the child's development.

  14. Properties of Membranes Derived from the Total Lipids Extracted from the Human Lens Cortex and Nucleus

    PubMed Central

    Mainali, Laxman; Raguz, Marija; O’Brien, William J.; Subczynski, Witold K.

    2013-01-01

    Human lens lipid membranes prepared using a rapid solvent exchange method from the total lipids extracted from the clear lens cortex and nucleus of 41- to 60-year-old donors were investigated using electron paramagnetic resonance spin-labeling. Profiles of the phospholipid alkyl-chain order, fluidity, oxygen transport parameter, and hydrophobicity were assessed across coexisting membrane domains. Membranes prepared from the lens cortex and nucleus were found to contain two distinct lipid environments, the bulk phospholipid-cholesterol domain and the cholesterol bilayer domain (CBD). The alkyl chains of phospholipids were strongly ordered at all depths, indicating that the amplitude of the wobbling motion of alkyl chains was small. However, profiles of the membrane fluidity, which explicitly contain time (expressed as the spin-lattice relaxation rate) and depend on the rotational motion of spin labels, show relatively high fluidity of alkyl chains close to the membrane center. Profiles of the oxygen transport parameter and hydrophobicity have a rectangular shape and also indicate a high fluidity and hydrophobicity of the membrane center. The amount of CBD was greater in nuclear membranes than in cortical membranes. The presence of the CBD in lens lipid membranes, which at 37°C showed a permeability coefficient for oxygen about 60% smaller than across a water layer of the same thickness, would be expected to raise the barrier for oxygen transport across the fiber cell membrane. Properties of human membranes are compared with those obtained for membranes made of lipids extracted from cortex and nucleus of porcine and bovine eye lenses. PMID:23438364

  15. The Novel Membrane-Bound Proteins MFSD1 and MFSD3 are Putative SLC Transporters Affected by Altered Nutrient Intake.

    PubMed

    Perland, Emelie; Hellsten, Sofie V; Lekholm, Emilia; Eriksson, Mikaela M; Arapi, Vasiliki; Fredriksson, Robert

    2017-02-01

    Membrane-bound solute carriers (SLCs) are essential as they maintain several physiological functions, such as nutrient uptake, ion transport and waste removal. The SLC family comprise about 400 transporters, and we have identified two new putative family members, major facilitator superfamily domain containing 1 (MFSD1) and 3 (MFSD3). They cluster phylogenetically with SLCs of MFS type, and both proteins are conserved in chordates, while MFSD1 is also found in fruit fly. Based on homology modelling, we predict 12 transmembrane regions, a common feature for MFS transporters. The genes are expressed in abundance in mice, with specific protein staining along the plasma membrane in neurons. Depriving mouse embryonic primary cortex cells of amino acids resulted in upregulation of Mfsd1, whereas Mfsd3 is unaltered. Furthermore, in vivo, Mfsd1 and Mfsd3 are downregulated in anterior brain sections in mice subjected to starvation, while upregulated specifically in brainstem. Mfsd3 is also attenuated in cerebellum after starvation. In mice raised on high-fat diet, Mfsd1 was specifically downregulated in brainstem and hypothalamus, while Mfsd3 was reduced consistently throughout the brain.

  16. Membrane Protein Crystallization in Lipidic Mesophases. Hosting lipid affects on the crystallization and structure of a transmembrane peptide.

    PubMed

    Höfer, Nicole; Aragão, David; Lyons, Joseph A; Caffrey, Martin

    2011-04-06

    Gramicidin is an apolar pentadecapeptide antibiotic consisting of alternating D-and L-amino acids. It functions, in part, by creating pores in membranes of susceptible cells rendering them leaky to monovalent cations. The peptide should be able to traverse the host membrane either as a double stranded, intertwined double helix (DSDH) or as a head-to-head single stranded helix (HHSH). Current structure models are based on macromolecular X-ray crystallography (MX) and nuclear magnetic resonance (NMR). However, the HHSH form has only been observed by NMR. The shape and size of the different gramicidin conformations differ. We speculated therefore that reconstituting it into a lipidic mesophase with bilayers of different microstructures would preferentially stabilize one form over the other. By using such mesophases for in meso crystallogenesis the expectation was that at least one would generate crystals of gramicidin in the HHSH form for structure determination by MX. This was tested using commercial and in-house synthesised lipids that support in meso crystallogenesis. Lipid acyl chain lengths were varied from 14 to 18 carbons to provide mesophases with a range of bilayer thicknesses. Unexpectedly, all lipids produced high quality, structure-grade crystals with gramicidin only in the DSDH conformation.

  17. Membrane Protein Crystallization in Lipidic Mesophases. Hosting lipid affects on the crystallization and structure of a transmembrane peptide

    PubMed Central

    Höfer, Nicole; Aragão, David; Lyons, Joseph A.; Caffrey, Martin

    2012-01-01

    Gramicidin is an apolar pentadecapeptide antibiotic consisting of alternating D-and L-amino acids. It functions, in part, by creating pores in membranes of susceptible cells rendering them leaky to monovalent cations. The peptide should be able to traverse the host membrane either as a double stranded, intertwined double helix (DSDH) or as a head-to-head single stranded helix (HHSH). Current structure models are based on macromolecular X-ray crystallography (MX) and nuclear magnetic resonance (NMR). However, the HHSH form has only been observed by NMR. The shape and size of the different gramicidin conformations differ. We speculated therefore that reconstituting it into a lipidic mesophase with bilayers of different microstructures would preferentially stabilize one form over the other. By using such mesophases for in meso crystallogenesis the expectation was that at least one would generate crystals of gramicidin in the HHSH form for structure determination by MX. This was tested using commercial and in-house synthesised lipids that support in meso crystallogenesis. Lipid acyl chain lengths were varied from 14 to 18 carbons to provide mesophases with a range of bilayer thicknesses. Unexpectedly, all lipids produced high quality, structure-grade crystals with gramicidin only in the DSDH conformation. PMID:22933857

  18. Presynaptic Membrane Potential Affects Transmitter Release in an Identified Neuron in Aplysia by Modulating the Ca2+ and K+ Currents

    NASA Astrophysics Data System (ADS)

    Shapiro, Eli; Castellucci, Vincent F.; Kandel, Eric R.

    1980-01-01

    We have examined the relationships between the modulation of transmitter release and of specific ionic currents by membrane potential in the cholinergic interneuron L10 of the abdominal ganglion of Aplysia californica. The presynaptic cell body was voltage-clamped under various pharmacological conditions and transmitter release from the terminals was assayed simultaneously by recording the synaptic potentials in the postsynaptic cell. When cell L10 was voltage-clamped from a holding potential of -60 mV in the presence of tetrodotoxin, graded transmitter release was evoked by depolarizing command pulses in the membrane voltage range (-35 mV to +10 mV) in which the Ca2+ current was also increasing. Depolarizing the holding potential of L10 results in increased transmitter output. Two ionic mechanisms contribute to this form of plasticity. First, depolarization inactivates some K+ channels so that depolarizing command pulses recruit a smaller K+ current. In unclamped cells the decreased K+ conductance causes spike-broadening and increased influx of Ca2+ during each spike. Second, small depolarizations around resting potential (-55 mV to -35 mV) activate a steady-state Ca2+ current that also contributes to the modulation of transmitter release, because, even with most presynaptic K+ currents blocked pharmacologically, depolarizing the holding potential still increases transmitter release. In contrast to the steady-state Ca2+ current, the transient inward Ca2+ current evoked by depolarizing clamp steps is relatively unchanged from various holding potentials.

  19. Anti-glomerular basement membrane antibody disease: a rare autoimmune disorder affecting the kidney and the lung.

    PubMed

    Lahmer, Tobias; Heemann, Uwe

    2012-12-01

    Anti-glomerular basement membrane antibody disease is a rare, but well characterized cause of glomerulonephritis. By definition serum anti-GBM antibody and/or a linear binding of IgG detected by direct immunofluorescence (IF) in a histological specimen of the kidney or the lung have to be detected. These antibodies can lead to acute rapid progressive glomerulonephritis(RPGN) and/or pulmonary hemorrhage (PH) because of collagen similarities in the basement membrane. Principally anti-GBM antibody disease can be divided into two groups: anti-GBM antibody disease without PH was regarded as renal-limited anti-GBM antibody disease and that with PH was defined as Goodpasture's syndrome (GPS). The important determinant for the response of therapy and long term diagnosis on anti-GBM disease is early diagnosis to prevent endstage renal disease. Therefore, standard treatment is a combined therapy of plasmapherisis, prednisolone and cyclophosphamide. The aim of this review is an overview of the pathogenesis, clinical presentation, diagnosis and treatment of anti-GBM disease.

  20. Membrane omega-3 fatty acids modulate the oligomerisation kinetics of adenosine A2A and dopamine D2 receptors

    PubMed Central

    Guixà-González, Ramon; Javanainen, Matti; Gómez-Soler, Maricel; Cordobilla, Begoña; Domingo, Joan Carles; Sanz, Ferran; Pastor, Manuel; Ciruela, Francisco; Martinez-Seara, Hector; Selent, Jana

    2016-01-01

    Membrane levels of docosahexaenoic acid (DHA), an essential omega-3 polyunsaturated fatty acid (ω-3 PUFA), are decreased in common neuropsychiatric disorders. DHA modulates key cell membrane properties like fluidity, thereby affecting the behaviour of transmembrane proteins like G protein-coupled receptors (GPCRs). These receptors, which have special relevance for major neuropsychiatric disorders have recently been shown to form dimers or higher order oligomers, and evidence suggests that DHA levels affect GPCR function by modulating oligomerisation. In this study, we assessed the effect of membrane DHA content on the formation of a class of protein complexes with particular relevance for brain disease: adenosine A2A and dopamine D2 receptor oligomers. Using extensive multiscale computer modelling, we find a marked propensity of DHA for interaction with both A2A and D2 receptors, which leads to an increased rate of receptor oligomerisation. Bioluminescence resonance energy transfer (BRET) experiments performed on living cells suggest that this DHA effect on the oligomerisation of A2A and D2 receptors is purely kinetic. This work reveals for the first time that membrane ω-3 PUFAs play a key role in GPCR oligomerisation kinetics, which may have important implications for neuropsychiatric conditions like schizophrenia or Parkinson’s disease. PMID:26796668

  1. Membrane omega-3 fatty acids modulate the oligomerisation kinetics of adenosine A2A and dopamine D2 receptors

    NASA Astrophysics Data System (ADS)

    Guixà-González, Ramon; Javanainen, Matti; Gómez-Soler, Maricel; Cordobilla, Begoña; Domingo, Joan Carles; Sanz, Ferran; Pastor, Manuel; Ciruela, Francisco; Martinez-Seara, Hector; Selent, Jana

    2016-01-01

    Membrane levels of docosahexaenoic acid (DHA), an essential omega-3 polyunsaturated fatty acid (ω-3 PUFA), are decreased in common neuropsychiatric disorders. DHA modulates key cell membrane properties like fluidity, thereby affecting the behaviour of transmembrane proteins like G protein-coupled receptors (GPCRs). These receptors, which have special relevance for major neuropsychiatric disorders have recently been shown to form dimers or higher order oligomers, and evidence suggests that DHA levels affect GPCR function by modulating oligomerisation. In this study, we assessed the effect of membrane DHA content on the formation of a class of protein complexes with particular relevance for brain disease: adenosine A2A and dopamine D2 receptor oligomers. Using extensive multiscale computer modelling, we find a marked propensity of DHA for interaction with both A2A and D2 receptors, which leads to an increased rate of receptor oligomerisation. Bioluminescence resonance energy transfer (BRET) experiments performed on living cells suggest that this DHA effect on the oligomerisation of A2A and D2 receptors is purely kinetic. This work reveals for the first time that membrane ω-3 PUFAs play a key role in GPCR oligomerisation kinetics, which may have important implications for neuropsychiatric conditions like schizophrenia or Parkinson’s disease.

  2. Response Mechanisms of Bacterial Degraders to Environmental Contaminants on the Level of Cell Walls and Cytoplasmic Membrane

    PubMed Central

    2014-01-01

    Bacterial strains living in the environment must cope with the toxic compounds originating from humans production. Surface bacterial structures, cell wall and cytoplasmic membrane, surround each bacterial cell and create selective barriers between the cell interior and the outside world. They are a first site of contact between the cell and toxic compounds. Organic pollutants are able to penetrate into cytoplasmic membrane and affect membrane physiological functions. Bacteria had to evolve adaptation mechanisms to counteract the damage originated from toxic contaminants and to prevent their accumulation in cell. This review deals with various adaptation mechanisms of bacterial cell concerning primarily the changes in cytoplasmic membrane and cell wall. Cell adaptation maintains the membrane fluidity status and ratio between bilayer/nonbilayer phospholipids as well as the efflux of toxic compounds, protein repair mechanisms, and degradation of contaminants. Low energy consumption of cell adaptation is required to provide other physiological functions. Bacteria able to survive in toxic environment could help us to clean contaminated areas when they are used in bioremediation technologies. PMID:25057269

  3. Altered membrane lipid dynamics and chemoprevention by non-steroidal anti inflammatory drugs during colon carcinogenesis.

    PubMed

    Singh Kanwar, S; Vaish, V; Nath Sanyal, S

    2011-01-01

    The present work focuses on the anti-neoplastic role of non steroidal anti-inflammatory drugs (NSAIDs) in modulating the biophysical parameters of the colonic membranes in 1,2-dimethylhydrazine dihydrochloride (DMH) induced carcinogenesis. The steady-state fluorescence polarization technique was applied to assess membrane fluidity, membrane polarity and lipid phase states. The decline in cholesterol content, biosynthesis and cholesterol: phospholipids ratio with DMH treatment indicates more fluidity associated with carcinogenesis. The DMH group had shown lower order parameter indicating more fluidity whereas NSAIDs resulted in increasing the membrane lipid order. The converging effects of these changes were more in membrane phase separations and membrane phase state. In DMH treatment membrane shows lesser phase separation or high polarity, and more liquid crystalline state while for NSAID groups membranes have higher phase separations or low polarity, and more of the gel phase. Further, NSAIDs induced anti-proliferative effects were evidently observed by apoptosis in the colonocytes by using acridine orange-ethidium bromide fluorescent staining and Terminal de-oxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. The results suggest that NSAIDs induced alteration in the membrane biophysical parameters may be an important initiating event for the chemopreventive action.

  4. Grape tannin catechin and ethanol fluidify oral membrane mimics containing moderate amounts of cholesterol: Implications on wine tasting?

    PubMed

    Furlan, Aurélien L; Saad, Ahmad; Dufourc, Erick J; Géan, Julie

    2016-11-01

    Wine tasting results in interactions of tannin-ethanol solutions with proteins and lipids of the oral cavity. Among the various feelings perceived during tasting, astringency and bitterness most probably result in binding events with saliva proteins, lipids and receptors. In this work, we monitored the conjugated effect of the grape polyphenol catechin and ethanol on lipid membranes mimicking the different degrees of keratinization of oral cavity surfaces by varying the amount of cholesterol present in membranes. Both catechin and ethanol fluidify the membranes as evidenced by solid-state (2)H NMR of perdeuterated lipids. The effect is however depending on the cholesterol proportion and may be very important and cumulative in the absence of cholesterol or presence of 18 mol % cholesterol. For 40 mol % cholesterol, mimicking highly keratinized membranes, both ethanol and catechin can no longer affect membrane dynamics. These observations can be accounted for by phase diagrams of lipid-cholesterol mixtures and the role played by membrane defects for insertion of tannins and ethanol when several phases coexist. These findings suggest that the behavior of oral membranes in contact with wine should be different depending of their cholesterol content. Astringency and bitterness could be then affected; the former because of a potential competition between the tannin-lipid and the tannin-saliva protein interaction, and the latter because of a possible fluidity modification of membranes containing taste receptors. The lipids that have been up to now weakly considered in oenology may be become a new actor in the issue of wine tasting.

  5. Lipid, Detergent, and Coomassie Blue G-250 Affect the Migration of Small Membrane Proteins in Blue Native Gels

    PubMed Central

    Crichton, Paul G.; Harding, Marilyn; Ruprecht, Jonathan J.; Lee, Yang; Kunji, Edmund R. S.

    2013-01-01

    Blue native gel electrophoresis is a popular method for the determination of the oligomeric state of membrane proteins. Studies using this technique have reported that mitochondrial carriers are dimeric (composed of two ∼32-kDa monomers) and, in some cases, can form physiologically relevant associations with other proteins. Here, we have scrutinized the behavior of the yeast mitochondrial ADP/ATP carrier AAC3 in blue native gels. We find that the apparent mass of AAC3 varies in a detergent- and lipid-dependent manner (from ∼60 to ∼130 kDa) that is not related to changes in the oligomeric state of the protein, but reflects differences in the associated detergent-lipid micelle and Coomassie Blue G-250 used in this technique. Higher oligomeric state species are only observed under less favorable solubilization conditions, consistent with aggregation of the protein. Calibration with an artificial covalent AAC3 dimer indicates that the mass observed for solubilized AAC3 and other mitochondrial carriers corresponds to a monomer. Size exclusion chromatography of purified AAC3 in dodecyl maltoside under blue native gel-like conditions shows that the mass of the monomer is ∼120 kDa, but appears smaller on gels (∼60 kDa) due to the unusually high amount of bound negatively charged dye, which increases the electrophoretic mobility of the protein-detergent-dye micelle complex. Our results show that bound lipid, detergent, and Coomassie stain alter the behavior of mitochondrial carriers on gels, which is likely to be true for other small membrane proteins where the associated lipid-detergent micelle is large when compared with the mass of the protein. PMID:23744064

  6. Inhibition of free radical scavenging enzymes affects mitochondrial membrane permeability transition during growth and aging of yeast cells.

    PubMed

    Deryabina, Yulia; Isakova, Elena; Sekova, Varvara; Antipov, Alexey; Saris, Nils-Erik L

    2014-12-01

    In this study, we investigated the change in the antioxidant enzymes activity, cell respiration, reactive oxygen species (ROS), and impairment of membrane mitochondria permeability in the Endomyces magnusii yeasts during culture growth and aging. We showed that the transition into stationary phase is the key tool to understanding interaction of these processes. This growth stage is distinguished by two-fold increase in ROS production and respiration rate as compared to those in the logarithmic phase. It results in induction of alternative oxidase (AO) in the stationary phase, decline of the main antioxidant enzymes activities, ROS-production, and mitochondria membrane permeability. Significant increase in the share of mitochondrial isoform of superoxide dismutase (SOD2) occurred in the stationary phase from 51.8% (24 h of cultivation) to 68.6% (48 h of cultivation). Upon blocking the essential ROS-scavenging enzymes, SODs and catalases (CATs) some heterogeneity of cell population was observed: 80-90% of cells displayed evident signs of early apoptosis (such as disorientation of mitochondria cristae, mitochondrial fragmentation and deformation of nuclear chromatine). However, 10-20% of the population were definitely healthy. It allowed to draw the conclusion that a complete system of cell antioxidant protection underlies normal mitochondria functioning while the E. magnusii yeasts grow and age. Moreover, this system provides unimpaired cell physiology under oxidative stress during culture aging in the stationary phase. Failures in mitochondria functions due to inhibition of ROS-scavenging enzymes of CATs and SODs could lead to damage of the cells and some signs of early apoptosis.

  7. The absence of protein Y4yS affects negatively the abundance of T3SS Mesorhizobium loti secretin, RhcC2, in bacterial membranes

    PubMed Central

    Mercante, Virginia; Duarte, Cecilia M.; Sánchez, Cintia M.; Zalguizuri, Andrés; Caetano-Anollés, Gustavo; Lepek, Viviana C.

    2015-01-01

    Mesorhizobium loti MAFF303099 has a functional type III secretion system (T3SS) that is involved in the determination of nodulation competitiveness on Lotus. The M. loti T3SS cluster contains gene y4yS (mlr8765) that codes for a protein of unknown function (Y4yS). A mutation in the y4yS gene favors the M. loti symbiotic competitive ability on Lotus tenuis cv. Esmeralda and affects negatively the secretion of proteins through T3SS. Here we localize Y4yS in the bacterial membrane using a translational reporter peptide fusion. In silico analysis indicated that this protein presents a tetratricopeptide repeat (TPR) domain, a signal peptide and a canonical lipobox LGCC in the N-terminal sequence. These features that are shared with proteins required for the formation of the secretin complex in type IV secretion systems and in the Tad system, together with its localization, suggest that the y4yS-encoded protein is required for the formation of the M. loti T3SS secretin (RhcC2) complex. Remarkably, analysis of RhcC2 in the wild-type and M. loti y4yS mutant strains indicated that the absence of Y4yS affects negatively the accumulation of normal levels of RhcC2 in the membrane. PMID:25688250

  8. Lead accumulation reduces photosynthesis in the lead hyper-accumulator Salvinia minima Baker by affecting the cell membrane and inducing stomatal closure.

    PubMed

    Leal-Alvarado, Daniel A; Espadas-Gil, Francisco; Sáenz-Carbonell, Luis; Talavera-May, Carlos; Santamaría, Jorge M

    2016-02-01

    Salvinia minima Baker accumulates a fair amount of lead in its tissues; however, no studies have investigated the effect of lead on the physiological processes that affect photosynthesis in this species. The objective of the present study was to assess whether the high amounts of lead accumulated by S. minima can affect its photosynthetic apparatus. The physiological changes in the roots and leaves in response to lead accumulation were analyzed. An exposure to 40 μM Pb(NO3)2 for 24 h (first stage) was sufficient to reduce the photosynthetic rate (Pn) by 44%. This reduction in Pn was apparently the result of processes at various levels, including damage to the cell membranes (mainly in roots). Interestingly, although the plants were transferred to fresh medium without lead for an additional 24 h (second stage), Pn not only remained low, but was reduced even further, which was apparently related to stomatal closure, and may have led to reduced CO2 availability. Therefore, it can be concluded that lead exposure first decreases the photosynthetic rate by damaging the root membrane and then induces stomatal closure, resulting in decreased CO2 availability.

  9. The absence of protein Y4yS affects negatively the abundance of T3SS Mesorhizobium loti secretin, RhcC2, in bacterial membranes.

    PubMed

    Mercante, Virginia; Duarte, Cecilia M; Sánchez, Cintia M; Zalguizuri, Andrés; Caetano-Anollés, Gustavo; Lepek, Viviana C

    2015-01-01

    Mesorhizobium loti MAFF303099 has a functional type III secretion system (T3SS) that is involved in the determination of nodulation competitiveness on Lotus. The M. loti T3SS cluster contains gene y4yS (mlr8765) that codes for a protein of unknown function (Y4yS). A mutation in the y4yS gene favors the M. loti symbiotic competitive ability on Lotus tenuis cv. Esmeralda and affects negatively the secretion of proteins through T3SS. Here we localize Y4yS in the bacterial membrane using a translational reporter peptide fusion. In silico analysis indicated that this protein presents a tetratricopeptide repeat (TPR) domain, a signal peptide and a canonical lipobox LGCC in the N-terminal sequence. These features that are shared with proteins required for the formation of the secretin complex in type IV secretion systems and in the Tad system, together with its localization, suggest that the y4yS-encoded protein is required for the formation of the M. loti T3SS secretin (RhcC2) complex. Remarkably, analysis of RhcC2 in the wild-type and M. loti y4yS mutant strains indicated that the absence of Y4yS affects negatively the accumulation of normal levels of RhcC2 in the membrane.

  10. The Maximum Fluidity Length of Solidifying Sn-Cu-Ag-Ni Solder Alloys

    NASA Astrophysics Data System (ADS)

    Gourlay, C. M.; Read, J.; Nogita, K.; Dahle, A. K.

    2008-01-01

    During wave soldering, it is important that a solder is able to flow easily to fill joints and to drain away to leave tidy fillets. The maximum fluidity length ( L f) is a simple measure of the flow behavior of solidifying alloys, defined as the distance a cooling and solidifying alloy can flow in a constant cross-section before the developing microstructure arrests flow. This paper explores the influence of alloy composition on L f in Sn-rich Sn-Cu-Ag-Ni alloys with compositions relevant to wave soldering. Significant differences in L f are measured among candidate lead-free solder alloys, which are discussed with respect to the phase diagrams and the mode of solidification.

  11. Influence of Basicity and MgO on Fluidity and Desulfurization Ability of High Aluminum Slag

    NASA Astrophysics Data System (ADS)

    Wang, Ping; Meng, Qing-min; Long, Hong-ming; Li, Jia-xin

    2016-08-01

    The viscosity of experimental slag, which was mixed based on the composition of a practical blast furnace slag, was measured in this paper. The influence of Al2O3 and MgO content, basicity R2 = w(CaO)/w(SiO2) on the fluidity of slag was studied. The stepwise regression analysis in SPSS was used to reveal the relationship between sulfur distribution coefficient LS and slag composition as well as furnace temperature. The results show that increasing of MgO up to 12% can decrease the slag viscosity. The w(MgO) should be controlled below 8% when there is 20% Al2O3 in the slag. Temperature of hot metal and content of CaO in slag are the two dominant factors on the desulfurization capacity of slag.

  12. An Examination of Organizational Fluidity and Workplace Quality in a Community College Setting: An Internal Multi-Stakeholder Perspective

    ERIC Educational Resources Information Center

    Porter, Catherine L.

    2013-01-01

    Community colleges today are experiencing monumental shifts in their operating environments. Some of these changes are known, but many of them are not. They include shifts in curriculum, funding, and societal expectation to name a few. Through the constructs of high quality work environment and organizational fluidity theory, this research…

  13. Membrane structure and surface coat of Entamoeba histolytica. Topochemistry and dynamics of the cell surface: cap formation and microexudate.

    PubMed

    Silva, P P; Martínez-Palomo, A; Gonzalez-Robles, A

    1975-03-01

    Treatment of living entamoeba histolytica cells with low concentrations of concanavalin A (con A) and peroxidase results in redistribution of the plasma membrane con A receptors to one pole of the cell where a morphologically distinct region--the uroid--is formed. Capping of con A receptors is not accompanied by parallel accumulation of ruthenium red-stainable components. In capped cells, the pattern of distribution of acidic sites ionized at pH 1.8 (labeled by colloidal iron) at the outer surface and of membrane particles (integral membrane components revealed by freeze-fracture) is not altered over the uroid region. Cytochemistry of substrate-attached microexudate located in regions adjacent to E. histolytica cells demonstrates the presence of con A binding sites and ruthenium red- and alcian blue-stainable components and the absent of colloidal iron binding sites. In a previous report we demonstrated that glycerol-induced aggregation of the plasma membrane particles is accompanied by a discontinuous distribution of colloidal iron binding sites, while con A receptors and acidic sites ionized at pH 4.0 remain uniformly distributed over the cell surface. Taken together, our experiments show that, in E. histolytica cells, peripheral membrane components may move independently of integral components and, also, that certain surface determinants may redistribute independently of others. These results point to the complexity of the membrane structure-cell surface relationship in E. histolytica plasma membranes relative to the membrane of the erythrocyte ghost where integral components (the membrane-intercalated particles) contain all antigens, receptors, and anionic sites labeled so far. We conclude that fluidity of integral membrane components (integral membrane fluidity) cannot be inferred from the demonstration of the mobility of surface components nor, conversely, can the fluidity of peripheral membrane components (peripheral membrane fluidity) be assumed from

  14. Effects of argon laser radiation on aortic endothelial cells: Early membrane changes and proliferative response

    SciTech Connect

    Franceschi, D.; Graham, D.; Alexander, J.J.; Koehler, K. )

    1989-06-01

    Membrane fluidity, transmembrane signaling responses, and proliferative characteristics of endothelial cells were studied to characterize biochemical and molecular changes after treatment with argon laser energy. Bovine aortic endothelial cells grown in monolayers were irradiated at 50, 100, and 200 J with an argon laser (wavelength, 488 and 514 nm). Proliferation, assayed by ({sup }3H)thymidine incorporation, was measured daily for 6 days. An initial lag phase was observed for irradiated cells when compared to nonirradiated controls (P less than 0.03), with eventual recovery by the third day. Membrane fluidity, determined by fluorescence anisotropy, was measured 1 hr after irradiation. A decrease in static rotational motion of 1,6-diphenyl-1,3,5-hexatriene (DPH) was noted in irradiated versus nonirradiated cells indicating a decrease in membrane fluidity (P less than 0.02). Dynamic studies of intracellular calcium and pH flux utilizing fluorescent probes demonstrated a preserved response to mitogenic stimulation. An increase in intracellular Ca2+ with a concomitant alkalinization of the intracellular milieu was observed in irradiated and non-irradiated cells in response to stimulation with endothelial cell growth factor (ECGF). These responses resemble those characterized for other mitogens. Argon laser energy applied to aortic endothelial cells decreases membrane fluidity early after irradiation. These alterations probably cause the initial lag observed in their proliferative response; however, the capacity to respond to exogenous mitogenic stimulation is maintained.

  15. Edelfosine and miltefosine effects on lipid raft properties: membrane biophysics in cell death by antitumor lipids.

    PubMed

    Castro, Bruno M; Fedorov, Aleksander; Hornillos, Valentin; Delgado, Javier; Acuña, A Ulises; Mollinedo, Faustino; Prieto, Manuel

    2013-07-03

    Edelfosine (1-O-octadecyl-2-O-methyl-sn-glycero-phosphocholine) and miltefosine (hexadecylphosphocholine) are synthetic alkylphospholipids (ALPs) that are reported to selectively accumulate in tumor cell membranes, inducing Fas clustering and activation on lipid rafts, triggering apoptosis. However, the exact mechanism by which these lipids elicit these events is still not fully understood. Recent studies propose that their mode of action might be related with alterations of lipid rafts biophysical properties caused by these lipid drugs. To achieve a clear understanding of this mechanism, we studied the effects of pharmacologically relevant amounts of edelfosine and miltefosine in the properties of model and cellular membranes. The influence of these molecules on membrane order, lateral organization, and lipid rafts molar fraction and size were studied by steady-state and time-resolved fluorescence methods, Förster resonance energy transfer (FRET), confocal and fluorescence lifetime imaging microscopy (FLIM). We found that the global membrane and lipid rafts biophysical properties of both model and cellular membranes were not significantly affected by both the ALPs. Nonetheless, in model membranes, a mild increase in membrane fluidity induced by both alkyl lipids was detected, although this effect was more noticeable for edelfosine than miltefosine. This absence of drastic alterations shows for the first time that ALPs mode of action is unlikely to be directly linked to alterations of lipid rafts biophysical properties caused by these drugs. The biological implications of this result are discussed in the context of ALPs effects on lipid metabolism, mitochondria homeostasis modulation, and their relationship with tumor cell death.

  16. Dynamics of Membrane Proteins within Synthetic Polymer Membranes with Large Hydrophobic Mismatch.

    PubMed

    Itel, Fabian; Najer, Adrian; Palivan, Cornelia G; Meier, Wolfgang

    2015-06-10

    The functioning of biological membrane proteins (MPs) within synthetic block copolymer membranes is an intriguing phenomenon that is believed to offer great potential for applications in life and medical sciences and engineering. The question why biological MPs are able to function in this completely artificial environment is still unresolved by any experimental data. Here, we have analyzed the lateral diffusion properties of different sized MPs within poly(dimethylsiloxane) (PDMS)-containing amphiphilic block copolymer membranes of membrane thicknesses between 9 and 13 nm, which results in a hydrophobic mismatch between the membrane thickness and the size of the proteins of 3.3-7.1 nm (3.5-5 times). We show that the high flexibility of PDMS, which provides membrane fluidities similar to phospholipid bilayers, is the key-factor for MP incorporation.

  17. Axially resolved polarisation microscopy of membrane dynamics in living cells

    NASA Astrophysics Data System (ADS)

    Wagner, Michael; Weber, Petra; Schneckenburger, Herbert

    2007-07-01

    Membrane dynamics has a large impact on cellular uptake and release of various metabolites or pharmaceutical agents. For a deeper understanding of the cellular processes involved, we used U373-MG human glioblastoma cells as a model system. As conventional microscopy does not permit to investigate individual layers in living cells, we used structured illumination techniques and total internal reflection fluorescence microscopy (TIRFM) to analyse the plasma membrane and intracellular membranes of living cells selectively. Optical image sections provide a high resolution and the possibility of 3D reconstruction. Membranes of living cells were characterized by the membrane marker 6-dodecanoyl-2-dimethylamino naphthalene (laurdan). Due to its spectral and kinetic properties this fluorescence marker appears appropriate for measuring membrane stiffness and fluidity. After excitation with linearly polarized laser pulses, membrane fluidity of human glioblastoma cells was determined by measurements of steady-state and time-resolved fluorescence anisotropy r(t), since with increasing viscosity of the environment, the rotation of an excited molecule is impeded. The corresponding time constant τ r of molecular relaxation decreased with temperature and increased with the amount of cholesterol. In addition, fluorescence anisotropy r(t) values of the plasma membrane were larger than the values of intracellular membranes for all temperatures in the range of 16°C<=T<=41°C.

  18. Dietary fat effects on brush border membrane composition and enzyme activities in rat intestine.

    PubMed

    Kaur, M; Kaur, J; Ojha, S; Mahmood, A

    1996-01-01

    The effect of dietary fats on the chemical composition and enzyme activities has been studied in intestinal brush border membranes (BBM) or rats. Animals were given commercial rat pellet diet (RP) or semisynthetic diet rich in either saturated [coconut oil (CCO))] or polyunsaturated [n-6, corn oil (CO) or n-3, fish oil (FO)] fat at the 10% level for 5 weeks. The membrane cholesterol/phospholipid ratio was augmented in CO- or RP-fed rats. There was an increase in level of saturated fatty acids in BBM from CCO- or FO-fed animals. n-3 polyunsaturated fatty acid content was raised in FO-fed rats, while the proportion of linoleic acid and arachidonic acid was enhanced in animals given a CO diet. Membrane fluidity was in the order of CCO < RP = CO < FO. The membrane hexose content was high (p < 0.05) in the CCO group. Hexosamines were elevated (p < 0.05) in CCO- or FO-fed rat brush borders. Membrane fucose was unaltered, while sialic acid content was elevated in CO- (p < 0.05) and FO- (p < 0.01) fed vs. CCO-fed rats. Lectin binding to brush borders corroborated these findings. The activities of alkaline phosphatase, sucrase and lactase were augmented (p < 0.001) in CCO-fed animals. Leucine-aminopeptidase and sucrase activities were depressed by FO feeding. The activities of PNP-beta-glycosidases were the highest in FO-fed rats. These results indicate that dietary fat quality markedly affects microvillus membrane lipid composition, glycosylation and enzyme functions in rat intestine.

  19. Movement imagery for speech in healthy women: influences on articulation accuracy and fluidity, imagery times, and expectations of success.

    PubMed

    Mantie-Kozlowski, Alana; Netsell, Ronald; Daniel, Todd

    2012-12-01

    The use of movement imagery in speech performance has received less attention than it has in many other professional disciplines. 30 healthy monolingual native English speakers participated in this within-subjects study. Participants' speech accuracy and fluidity was compared when they used movement imagery and when they did not. The timing of imagery and articulation were compared using a chronometric paradigm. Participants' expectations of improvement when using movement imagery for speech were compared to their actual performance. The results from this study support the use of movement imagery for speech with a single imaging event for the purpose of improving speech fluidity, but not for improving articulation accuracy. The chronometric system as a tool for monitoring adherence to the movement imagery protocol for speech proved valuable. Finally, while estimation inflation has been reported by some using movement imagery techniques, this was not the case for the participants of this study.

  20. Agarose Gel Electrophoresis Reveals Structural Fluidity of a Phage T3 DNA Packaging Intermediate

    PubMed Central

    Serwer, Philip; Wright, Elena T.

    2012-01-01

    We find a new aspect of DNA packaging-associated structural fluidity for phage T3 capsids. The procedure is (1) glutaraldehyde cross-linking of in vivo DNA packaging intermediates for stabilization of structure and then (2) determining of effective radius by two-dimensional agarose gel electrophoresis (2d-AGE). The intermediates are capsids with incompletely packaged DNA (ipDNA) and without an external DNA segment; these intermediates are called ipDNA-capsids. We initially increase production of ipDNA-capsids by raising NaCl concentration during in vivo DNA packaging. By 2d-AGE, we find a new state of contracted shell for some particles of one previously identified ipDNA-capsid. The contracted shell-state is found when ipDNA length/mature DNA length (F) is above 0.17, but not at lower F. Some contracted-shell ipDNA-capsids have the phage tail; others do not. The contracted-shell ipDNA-capsids are explained by premature DNA maturation cleavage that makes accessible a contracted-shell intermediate of a cycle of the T3 DNA packaging motor. The analysis of ipDNA-capsids, rather than intermediates with uncleaved DNA, provides a simplifying strategy for a complete biochemical analysis of in vivo DNA packaging. PMID:22222979

  1. Recycling of tailings from Korea Molybdenum Corporation as admixture for high-fluidity concrete.

    PubMed

    Jung, Moon Young; Choi, Yun Wang; Jeong, Jae Gwon

    2011-01-01

    The main objective of this study is to develop an eco-friendly and a large recycling technique of flotation Tailings from korea (TK) from metal mines as construction materials such as admixtures for high-fluidity concrete (HFC). TK used in this study was obtained from the Korea Molybdenum Corporation in operation. TK was used as the alternative material to adjust flowability and viscosity of HFC in the form of powder agent which enables adjustment of concrete compressive strength. In this study, we have performed concrete rheological tests and concrete flowability tests to obtain the quality characteristics of TK for using as the admixture in producing HFC. The results indicated that the adequate mix ratio of cement to TK should be 8:2 (vol%). It is more effective to use the TK as admixture to control flowability, viscosity and strength of HFC than the normal concrete. It was found that TK could be recycled construction materials in bulk such as admixture for HFC, in terms of the economic and eco-friendly aspects.

  2. Agarose gel electrophoresis reveals structural fluidity of a phage T3 DNA packaging intermediate.

    PubMed

    Serwer, Philip; Wright, Elena T

    2012-01-01

    We find a new aspect of DNA packaging-associated structural fluidity for phage T3 capsids. The procedure is (i) glutaraldehyde cross-linking of in vivo DNA packaging intermediates for the stabilization of structure and then (ii) determining effective radius by two-dimensional agarose gel electrophoresis (2D-AGE). The intermediates are capsids with incompletely packaged DNA (ipDNA) and without an external DNA segment; these intermediates are called ipDNA-capsids. We initially increase the production of ipDNA-capsids by raising NaCl concentration during in vivo DNA packaging. By 2D-AGE, we find a new state of contracted shell for some particles of one previously identified ipDNA-capsid. The contracted shell-state is found when the ipDNA length/mature DNA length (F) is above 0.17, but not at lower F. Some contracted-shell ipDNA-capsids have the phage tail; others do not. The contracted-shell ipDNA-capsids are explained by premature DNA maturation cleavage that makes accessible a contracted-shell intermediate of a cycle of the T3 DNA packaging motor. The analysis of ipDNA-capsids, rather than intermediates with uncleaved DNA, provides a simplifying strategy for a complete biochemical analysis of in vivo DNA packaging.

  3. "None Must Meddle Betueene Man and Wife": assessing family and the fluidity of public and private in early modern Scotland.

    PubMed

    Nugent, Janay

    2010-01-01

    The physical and ideological boundaries between public and private in early modern Scotland were constantly contested, resulting in a shifting reality of what was public and private. This fluidity has been recognized by historians, but how, when, and why the shifting took place is not as clear. The moral church courts (Kirk Sessions) of Reformation Scotland allow a unique opportunity to begin to understand the largely elusive boundaries between public and private in the early modern era.

  4. Shear viscosity to entropy density ratios and implications for (im)perfect fluidity in Fermionic and Bosonic superfluids

    NASA Astrophysics Data System (ADS)

    Boyack, Rufus; Guo, Hao; Levin, K.

    2015-03-01

    Recent experiments on both unitary Fermi gases and high temperature superconductors (arxiv:1410.4835 [cond-mat.quant-gas], arxiv:1409.5820 [cond-mat.str-el].) have led to renewed interest in near perfect fluidity in condensed matter systems. This is quantified by studying the ratio of shear viscosity to entropy density. In this talk we present calculations of this ratio in homogeneous bosonic and fermionic superfluids, with the latter ranging from BCS to BEC. While the shear viscosity exhibits a power law (for bosons) or exponential suppression (for fermions), a similar dependence is found for the respective entropy densities. As a result, strict BCS and (true) bosonic superfluids have an analogous viscosity to entropy density ratio, behaving linearly with temperature times the (T-dependent) dissipation rate; this is characteristic of imperfect fluidity in weakly coupled fluids. This is contrasted with the behavior of fermions at unitarity which we argue is a consequence of additional terms in the entropy density thereby leading to more perfect fluidity. (arXiv:1407.7572v1 [cond-mat.quant-gas])

  5. Preliminary Evidence for Cell Membrane Amelioration in Children with Cystic Fibrosis by 5-MTHF and Vitamin B12 Supplementation: A Single Arm Trial

    PubMed Central

    Scambi, Cinzia; De Franceschi, Lucia; Guarini, Patrizia; Poli, Fabio; Siciliano, Angela; Pattini, Patrizia; Biondani, Andrea; La Verde, Valentina; Bortolami, Oscar; Turrini, Francesco; Carta, Franco; D'Orazio, Ciro; Assael, Baroukh M.; Faccini, Giovanni; Bambara, Lisa M.

    2009-01-01

    Background Cystic fibrosis (CF) is one of the most common fatal autosomal recessive disorders in the Caucasian population caused by mutations of gene for the cystic fibrosis transmembrane conductance regulator (CFTR). New experimental therapeutic strategies for CF propose a diet supplementation to affect the plasma membrane fluidity and to modulate amplified inflammatory response. The objective of this study was to evaluate the efficacy of 5-methyltetrahydrofolate (5-MTHF) and vitamin B12 supplementation for ameliorating cell plasma membrane features in pediatric patients with cystic fibrosis. Methodology and Principal Findings A single arm trial was conducted from April 2004 to March 2006 in an Italian CF care centre. 31 children with CF aged from 3 to 8 years old were enrolled. Exclusion criteria were diabetes, chronic infections of the airways and regular antibiotics intake. Children with CF were supplemented for 24 weeks with 5-methyltetrahydrofolate (5-MTHF, 7.5 mg /day) and vitamin B12 (0.5 mg/day). Red blood cells (RBCs) were used to investigate plasma membrane, since RBCs share lipid, protein composition and organization with other cell types. We evaluated RBCs membrane lipid composition, membrane protein oxidative damage, cation content, cation transport pathways, plasma and RBCs folate levels and plasma homocysteine levels at baseline and after 24 weeks of 5-MTHF and vitamin B12 supplementation. In CF children, 5-MTHF and vitamin B12 supplementation (i) increased plasma and RBC folate levels; (ii) decreased plasma homocysteine levels; (iii) modified RBC membrane phospholipid fatty acid composition; (iv) increased RBC K+ content; (v) reduced RBC membrane oxidative damage and HSP70 membrane association. Conclusion and Significance 5-MTHF and vitamin B12 supplementation might ameliorate RBC membrane features of children with CF. Trial Registration ClinicalTrials.gov NCT00730509 PMID:19277125

  6. Chronic administration of a melatonin membrane receptor antagonist, luzindole, affects hippocampal neurogenesis without changes in hopelessness-like behavior in adult mice.

    PubMed

    Ortiz-López, Leonardo; Pérez-Beltran, Carlos; Ramírez-Rodríguez, Gerardo

    2016-04-01

    Melatonin is involved in the regulation of hippocampal neuronal development during adulthood. Emerging evidence indicates that exogenous melatonin acts during different events of the neurogenic process and exerts antidepressant-like behavior in rodents. Thus, melatonin might act through different mechanism, including acting as an antioxidant, interacting with intracellular proteins and/or activating membrane receptors. The melatonin membrane receptors (MMRs; Mt1/Mt2) are distributed throughout the hippocampus with an interesting localization in the hippocampal neurogenic microenvironment (niche), suggesting the involvement of these receptors in the beneficial effects of melatonin on hippocampal neurogenesis and behavior. In this study, we analyzed the participation of MMRs in the baseline neurogenesis in C57BL/6 mice. To this end, we used a pharmacological approach, administering luzindole (10 mg/kg) for 14 days. We observed a decrease in the absolute number of doublecortin-positive cells (49%) without changes in either the dendrite complexity of mature doublecortin-cells or the number of apoptotic cells (TUNEL). However, after the chronic administration of luzindole, cell proliferation (Ki67) significantly decreased (36%) with increasing (>100%) number of neural stem cells (NSCs; GFAP(+)/Sox2(+)) in the subgranular zone of the dentate gyrus of the hippocampus. In addition, luzindole did not affect hopelessness-like behavior in the forced swim test (FST) or changes in the novelty suppressed feeding test (NST) after 14 days of treatment either neuronal activation in the dentate gyrus after FST. These results suggest that the MMRs are involved in the effects of endogenous melatonin to mediate the transition from NSCs and proliferative cells to the following developmental stages implicated in the hippocampal neurogenic process of adult female C57BL/6 mice.

  7. Effect of Pulsed Electric Field on Membrane Lipids and Oxidative Injury of Salmonella typhimurium

    PubMed Central

    Yun, Ou; Zeng, Xin-An; Brennan, Charles S.; Han, Zhong

    2016-01-01

    Salmonella typhimurium cells were subjected to pulsed electric field (PEF) treatment at 25 kV/cm for 0–4 ms to investigate the effect of PEF on the cytoplasmic membrane lipids and oxidative injury of cells. Results indicated that PEF treatment induced a decrease of membrane fluidity of Salmonella typhimurium (S. typhimuriumi), possibly due to the alterations of fatty acid biosynthesis-associated gene expressions (down-regulation of cfa and fabA gene expressions and the up-regulation of fabD gene expression), which, in turn, modified the composition of membrane lipid (decrease in the content ratio of unsaturated fatty acids to saturated fatty acids). In addition, oxidative injury induced by PEF treatment was associated with an increase in the content of malondialdehyde. The up-regulation of cytochrome bo oxidase gene expressions (cyoA, cyoB, and cyoC) indicated that membrane damage was induced by PEF treatment, which was related to the repairing mechanism of alleviating the oxidative injury caused by PEF treatment. Based on these results, we achieved better understanding of microbial injury induced by PEF, suggesting that micro-organisms tend to decrease membrane fluidity in response to PEF treatment and, thus, a greater membrane fluidity might improve the efficiency of PEF treatment to inactivate micro-organisms. PMID:27556460

  8. Physicochemical constraints of elevated pH affect efficient membrane interaction and arrest an abortive membrane-bound oligomeric intermediate of the beta-barrel pore-forming toxin Vibrio cholerae cytolysin.

    PubMed

    Rai, Anand Kumar; Kundu, Nidhi; Chattopadhyay, Kausik

    2015-10-01

    Vibrio cholerae cytolysin (VCC) is a potent membrane-damaging cytotoxic protein. VCC causes permeabilization of the target cell membranes by forming transmembrane oligomeric beta-barrel pores. Membrane pore formation by VCC involves following key steps: (i) membrane binding, (ii) formation of a pre-pore oligomeric intermediate, (iii) membrane insertion of the pore-forming motifs, and (iv) formation of the functional transmembrane pore. Membrane binding, oligomerization, and subsequent pore-formation process of VCC appear to be facilitated by multiple regulatory mechanisms that are only partly understood. Here, we have explored the role(s) of the physicochemical constraints, specifically imposed by the elevated pH conditions, on the membrane pore-formation mechanism of VCC. Elevated pH abrogates efficient interaction of VCC with the target membranes, and blocks its pore-forming activity. Under the elevated pH conditions, membrane-bound fractions of VCC remain trapped in the form of abortive oligomeric species that fail to generate the functional transmembrane pores. Such an abortive oligomeric assembly appears to represent a distinct, more advanced intermediate state than the pre-pore state. The present study offers critical insights regarding the implications of the physicochemical constraints for regulating the efficient membrane interaction and pore formation by VCC.

  9. Membrane fluidization by animycotic bifonazole.

    PubMed

    Albertini, G; Bossi, G; Dubini, B; Phadke, R S; Ponzi Bossi, M G; Pugnaloni, A; Srivastava, S

    1995-01-01

    Calorimetry, nuclear magnetic resonance and X-ray diffraction techniques have been used to obtain thermodynamic and structural information on dipalmitoyl phosphatidylcholine (DPPC) liposomes doped by the antimycotic drug bifonazole in the range 0 < R < 1, where R = moles of bifonazole/moles of DPPC. The technique of spin labeling electron spin resonance (ESR) has also been used to study permeability and fluidity properties. The decrease of the cooperativity at the gel to liquid crystalline phase transition, as shown by ESR an DSC measurements, indicates that bifonazole imparts higher fluidity to the lipid matrix. Increase in permeability of ascorbate ions, after incorporation of bifonazole in the membrane, has been detected by ESR experiments using spin label 5-SASL. 13C NMR spectra indicate that the drug molecule is highly immobilized. X-ray diffraction and freeze fracture TEM results show that the equilibrated phase at room temperature is lamellar and unidimensional together with the presence of small particles and pits of uniform size. A marked hysteresis is evident in the formation of this phase.

  10. Trans-cis isomerization of lipophilic dyes probing membrane microviscosity in biological membranes and in live cells.

    PubMed

    Chmyrov, Volodymyr; Spielmann, Thiemo; Hevekerl, Heike; Widengren, Jerker

    2015-06-02

    Membrane environment and fluidity can modulate the dynamics and interactions of membrane proteins and can thereby strongly influence the function of cells and organisms in general. In this work, we demonstrate that trans-cis isomerization of lipophilic dyes is a useful parameter to monitor packaging and fluidity of biomembranes. Fluorescence fluctuations, generated by trans-cis isomerization of the thiocarbocyanine dye Merocyanine 540 (MC540), were first analyzed by fluorescence correlation spectroscopy (FCS) in different alcohol solutions. Similar isomerization kinetics of MC540 in lipid vesicles could then also be monitored, and the influence of lipid polarity, membrane curvature, and cholesterol content was investigated. While no influence of membrane curvature and lipid polarity could be observed, a clear decrease in the isomerization rates could be observed with increasing cholesterol contents in the vesicle membranes. Finally, procedures to spatially map photoinduced and thermal isomerization rates on live cells by transient state (TRAST) imaging were established. On the basis of these procedures, MC540 isomerization was studied on live MCF7 cells, and TRAST images of the cells at different temperatures were found to reliably detect differences in the isomerization parameters. Our studies indicate that trans-cis isomerization is a useful parameter for probing membrane dynamics and that the TRAST imaging technique can provide spatial maps of photoinduced isomerization as well as both photoinduced and thermal back-isomerization, resolving differences in local membrane microviscosity in live cells.

  11. The ataxia related G1107D mutation of the plasma membrane Ca(2+) ATPase isoform 3 affects its interplay with calmodulin and the autoinhibition process.

    PubMed

    Calì, Tito; Frizzarin, Martina; Luoni, Laura; Zonta, Francesco; Pantano, Sergio; Cruz, Carlos; Bonza, Maria Cristina; Bertipaglia, Ilenia; Ruzzene, Maria; De Michelis, Maria Ida; Damiano, Nunzio; Marin, Oriano; Zanni, Ginevra; Zanotti, Giuseppe; Brini, Marisa; Lopreiato, Raffaele; Carafoli, Ernesto

    2017-01-01

    The plasma membrane Ca(2+) ATPases (PMCA pumps) have a long, cytosolic C-terminal regulatory region where a calmodulin-binding domain (CaM-BD) is located. Under basal conditions (low Ca(2+)), the C-terminal tail of the pump interacts with autoinhibitory sites proximal to the active center of the enzyme. In activating conditions (i.e., high Ca(2+)), Ca(2+)-bound CaM displaces the C-terminal tail from the autoinhibitory sites, restoring activity. We have recently identified a G1107D replacement within the CaM-BD of isoform 3 of the PMCA pump in a family affected by X-linked congenital cerebellar ataxia. Here, we investigate the effects of the G1107D replacement on the interplay of the mutated CaM-BD with both CaM and the pump core, by combining computational, biochemical and functional approaches. We provide evidence that the affinity of the isolated mutated CaM-BD for CaM is significantly reduced with respect to the wild type (wt) counterpart, and that the ability of CaM to activate the pump in vitro is thus decreased. Multiscale simulations support the conclusions on the detrimental effect of the mutation, indicating reduced stability of the CaM binding. We further show that the G1107D replacement impairs the autoinhibition mechanism of the PMCA3 pump as well, as the introduction of a negative charge perturbs the contacts between the CaM-BD and the pump core. Thus, the mutation affects both the ability of the pump to optimally transport Ca(2+) in the activated state, and the autoinhibition mechanism in its resting state.

  12. Comparison of ceftiofur hydrochloride and estradiol cypionate for metritis prevention and reproductive performance in dairy cows affected with retained fetal membranes.

    PubMed

    Risco, C A; Hernandez, J

    2003-06-01

    The objective of this study was to compare the effect of ceftiofur hydrochloride and estradiol cypionate (ECP) administration for metritis prevention and reproductive performance in dairy cows affected with retained fetal membranes (RFMs). After parturition, 97 dairy cows affected with RFM from a single dairy herd were randomly allocated to 1 of 3 treatment groups. Cows in-group 1 (n=31) were treated daily for 5 days with ceftiofur hydrochloride (2.2mg/kg, i.m.); cows in group 2 (n=33) were treated once with ECP (4 mg, i.m.); and cows in group 3 (n=33) were not treated. The proportion of cows with metritis, uterine involution patterns and the calving-to-conception interval were compared between groups. The proportion of cows that developed metritis was significantly different (P<0.05) in cows treated with ceftiofur hydrochloride (13%), compared with cows treated with ECP (42%) or cows that received no treatment (42%). Uterine involution patterns (i.e. median time to complete retraction of the uterus and mean diameter measure of cervix and uterine horns) were not significantly different between groups. Cows treated with ECP were 0.40 times as likely to conceive as control cows (P=0.05); median time to conception in cows treated with ECP (192 days) was longer, compared to control cows (124 days). We conclude that systemic administration of ceftioufur hydrochloride is beneficial for prevention of metritis, but its effect on reproductive performance was not significantly different to that of ECP or no treatment. In addition, administration of ECP did not have beneficial effects on metritis prevention and reproductive performance.

  13. Palmitoylation of cysteine 415 of CB1 receptor affects ligand-stimulated internalization and selective interaction with membrane cholesterol and caveolin 1.

    PubMed

    Oddi, Sergio; Stepniewski, Tomasz Maciej; Totaro, Antonio; Selent, Jana; Scipioni, Lucia; Dufrusine, Beatrice; Fezza, Filomena; Dainese, Enrico; Maccarrone, Mauro

    2017-02-12

    We previously demonstrated that CB1 receptor is palmitoylated at cysteine 415, and that such a post-translational modification affects its biological activity. To assess the molecular mechanisms responsible for modulation of CB1 receptor function by S-palmitoylation, in this study biochemical and morphological approaches were paralleled with computational analyses. Molecular dynamics simulations suggested that this acyl chain stabilizes helix 8 as well as the interaction of CB1 receptor with membrane cholesterol. In keeping with these in silico data, experimental results showed that the non-palmitoylated CB1 receptor was unable to interact efficaciously with caveolin 1, independently of its activation state. Moreover, in contrast with the wild-type receptor, the lack of S-palmitoylation in the helix 8 made the mutant CB1 receptor completely irresponsive to agonist-induced effects in terms of both lipid raft partitioning and receptor internalization. Overall, our results support the notion that palmitoylation of cysteine 415 modulates the conformational state of helix 8 and influences the interactions of CB1 receptor with cholesterol and caveolin 1, suggesting that the palmitoyl chain may serve as a functional interface for CB1 receptor localization and function.

  14. Effects of cholesterol on plasma membrane lipid order in MCF-7 cells by two-photon microscopy

    NASA Astrophysics Data System (ADS)

    Zeng, Yixiu; Chen, Jianling; Yang, Hongqin; Wang, Yuhua; Li, Hui; Xie, Shusen

    2014-09-01

    Lipid rafts are cholesterol- and glycosphingolipids- enriched microdomains on plasma membrane surface of mammal cells, involved in a variety of cellular processes. Depleting cholesterol from the plasma membrane by drugs influences the trafficking of lipid raft markers. Optical imaging techniques are powerful tools to study lipid rafts in live cells due to its noninvasive feature. In this study, breast cancer cells MCF-7 were treated with different concentrations of MβCD to deplete cholesterol and an environmentally sensitive fluorescence probe, Laurdan was loaded to image lipid order by two-photon microscopy. The generalized polarization (GP) values were calculated to distinguish the lipid order and disorder phase. GP images and GP distributions of native and cholesterol-depleted MCF-7 cells were obtained. Our results suggest that even at low concentration (0.5 mM) of MβCD, the morphology of the MCF-7 cells changes. Small high GP areas (lipid order phase) decrease more rapidly than low GP areas (lipid disorder phase), indicating that lipid raft structure was altered more severely than nonraft domains. The data demonstrates that cholesterol dramatically affect raft coverage and plasma membrane fluidity in living cells.

  15. Knocking Down of Isoprene Emission Modifies the Lipid Matrix of Thylakoid Membranes and Influences the Chloroplast Ultrastructure in Poplar1

    PubMed Central

    Velikova, Violeta; Müller, Constanze; Ghirardo, Andrea; Rock, Theresa Maria; Aichler, Michaela; Walch, Axel; Schmitt-Kopplin, Philippe

    2015-01-01

    Isoprene is a small lipophilic molecule with important functions in plant protection against abiotic stresses. Here, we studied the lipid composition of thylakoid membranes and chloroplast ultrastructure in isoprene-emitting (IE) and nonisoprene-emitting (NE) poplar (Populus × canescens). We demonstrated that the total amount of monogalactosyldiacylglycerols, digalactosyldiacylglycerols, phospholipids, and fatty acids is reduced in chloroplasts when isoprene biosynthesis is blocked. A significantly lower amount of unsaturated fatty acids, particularly linolenic acid in NE chloroplasts, was associated with the reduced fluidity of thylakoid membranes, which in turn negatively affects photosystem II photochemical efficiency. The low photosystem II photochemical efficiency in NE plants was negatively correlated with nonphotochemical quenching and the energy-dependent component of nonphotochemical quenching. Transmission electron microscopy revealed alterations in the chloroplast ultrastructure in NE compared with IE plants. NE chloroplasts were more rounded and contained fewer grana stacks and longer stroma thylakoids, more plastoglobules, and larger associative zones between chloroplasts and mitochondria. These results strongly support the idea that in IE species, the function of this molecule is closely associated with the structural organization and functioning of plastidic membranes. PMID:25975835

  16. Integral membrane proteins Brr6 and Apq12 link assembly of the nuclear pore complex to lipid homeostasis in the endoplasmic reticulum

    PubMed Central

    Hodg, Christine A.; Choudhary, Vineet; Wolyniak, Michael J.; Scarcelli, John J.; Schneiter, Roger; Col, Charles N.

    2010-01-01

    Summary Cells of Saccharomyces cerevisiae lacking Apq12, a nuclear envelope (NE)-endoplasmic reticulum (ER) integral membrane protein, are defective in assembly of nuclear pore complexes (NPCs), possibly because of defects in regulating membrane fluidity. We identified BRR6, which encodes an essential integral membrane protein of the NE-ER, as a dosage suppressor of apq12 Δ. Cells carrying the temperature-sensitive brr6-1 allele have been shown to have defects in nucleoporin localization, mRNA metabolism and nuclear transport. Electron microscopy revealed that brr6-1 cells have gross NE abnormalities and proliferation of the ER. brr6-1 cells were hypersensitive to compounds that affect membrane biophysical properties and to inhibitors of lipid biosynthetic pathways, and displayed strong genetic interactions with genes encoding non-essential lipid biosynthetic enzymes. Strikingly, brr6-1 cells accumulated, in or near the NE, elevated levels of the two classes of neutral lipids, steryl esters and triacylglycerols, and over-accumulated sterols when they were provided exogenously. Although neutral lipid synthesis is dispensable in wild-type cells, viability of brr6-1 cells was fully dependent on neutral lipid production. These data indicate that Brr6 has an essential function in regulating lipid homeostasis in the NE-ER, thereby impacting NPC formation and nucleocytoplasmic transport. PMID:20016074

  17. [Structural-functional changes in lymphocyte ans erythrocyte membranes after exposure to alternating magnetic field].

    PubMed

    Bordiushkov, Iu N; Goroshinskaia, I A; Frantsiiants, E M; Tkacheva, G N; Gorlo, E I; Neskubina, I V

    2000-01-01

    The lymphocyte membrane fluidity, membrane potential, isoenzyme spectrum of superoxide dismutase (SOD) and catabolic product level of blood cell receptors in rats, healthy volunteers and patients with ovary and skin tumors were studied under the influence of low frequency electromagnetic field (EMF). The increase of fluidity of rat blood lymphocyte membranes was observed at 20 and 40 min exposure of the lymphocyte suspension to EMF. The increase of ANS fluorescence observed after 20 min exposure to EMF suggested a decrease of cell membrane potential. EMF exerted opposite changes of lymphocyte membrane fluidity of healthy volunteers and the effect depended on the initial level of this parameter. Study of SOD isoenzyme spectrum revealed that Cu,Zn-dependent SOD can account for the superoxide dismutase catalytic activity of supernatant and lymphocytes. The EMF exposure for 20 min caused 2-fold increase of SOD activity. The EMF exposure for 40 min caused the further increase of SOD activity but only in lymphocytes. At the same time the EMF exposure did not influence the actual SOD-activity in erythrocytes. However, there was clear anti-R-reagent-sensitive SOD-activity which was not abolished by DDC. The reasons and possible consequences of these changes of feuidity and SOD-activity under EMF effect are discussed.

  18. Effects of vegetable oils on biochemical and biophysical properties of membrane retinal pigment epithelium cells.

    PubMed

    Said, Toihiri; Tremblay-Mercier, Jennifer; Berrougui, Hicham; Rat, Patrice; Khalil, Abdelouahed

    2013-10-01

    The aim of this study was to investigate the effect of vegetable oil enrichment of retinal pigment epithelial (RPE) cells on their biochemical and biophysical properties. For this, RPE cells were incubated with 4 different vegetables oils (olive oil, corn oil, argan oil, and camelina oil). The cytotoxicity of these vegetable oils was assessed in vivo on 8-week-old mice and in vitro by using the neutral red and YO-PRO-1 tests. Membrane fluidity was evaluated by fluorescence anisotropy using the fluorescent probe diphenylhexatriene, and membrane fatty acid composition was assessed by gas chromatography. None of the oils tested displayed cytotoxic effects. In vitro, omega-3 rich oils improved membrane fluidity by 47% compared with the control cells. The omega-3 PUFA content within membranes decreased by 38% to 55% when cells were incubated separately with olive oil, corn oil, or argan oil, and increased when cells were incubated with a mixture of those oils, or with camelina oil alone (50% and 103% increase, respectively). Our results show that the fatty acids in vegetable oil incorporate into retinal cells and increase the plasma membrane fluidity.

  19. Progestin treatment does not affect expression of cytokines, steroid receptors, oxytocin receptor, and cyclooxygenase 2 in fetal membranes and endometrium from pony mares at parturition.

    PubMed

    Palm, F; Walter, I; Nowotny, N; Budik, S; Helmreich, M; Aurich, C

    2013-01-01

    In most mammalian species, progestins have a major function in maintaining pregnancy. In humans, the physiologic initiation of parturition bears similarities with inflammatory processes and anti-inflammatory effects of progestins have been suggested to postpone birth until term. To examine if comparable effects exist in the horse, mares were treated with the synthetic progestin altrenogest from day 280 of gestation until parturition (N = 5) or were left untreated as controls (N = 7). Tissue from the amnion (AMN), allantochorion (AC), and endometrium (EM) was collected at foaling and mRNA expression of interleukin (IL)-6 and -8, cyclooxygenase 2 (COX2), estrogen receptor (ER) α, progesterone receptor, and oxytocin receptor (OTR) was analyzed. Leukocytes, steroid receptors, COX2, and OTR were also investigated by histology and immunohistochemistry. Expression of mRNA for IL-6 was higher in AMN and EM versus AC (P < 0.01). Expression of IL-8 was higher in AMN than AC and EM (P < 0.001). Steroid receptors and OTR were highly expressed in EM but not in AMN and AC (P < 0.001). Expression of COX2 was most pronounced in AC whereas IL expression was not upregulated in AC. No differences in mRNA expression existed between altrenogest-treated and control animals. Endometrial polymorphonuclear leukocytes were increased in altrenogest-treated mares. Epithelial cells of all tissues, except AC chorionic villi stained progesterone receptor-positive. Staining for ER was more pronounced in the amnion facing epithelium of the AC in altrenogest-treated versus control animals (P < 0.01). In conclusion, COX2 is highly expressed in the AC. The fetal membranes thus might play a role in the onset of labor in the horse. Altrenogest did not affect gene expression in the AMN, AC, and EM but had localized effects on inflammatory cells and ER expression. No anti-inflammatory effects of altrenogest in healthy, late pregnant pony mares could be detected.

  20. The validity of an accelerometer-based method for estimating fluidity in the sit-to-walk task in a community setting

    PubMed Central

    Asakura, Tomoyuki; Miyazawa, Yoshiyuki; Usuda, Shigeru

    2017-01-01

    [Purpose] Fluidity in the sit-to-walk task has been quantitatively measured with three-dimensional motion analysis system. The purpose of this study was to determine the validity of an accelerometer-based method for estimating fluidity in community-dwelling elderly individuals. [Subjects and Methods] Seventeen community-dwelling elderly females performed a sit-to-walk task. The motion was recorded by an accelerometer, a three-dimensional motion analysis system and a foot pressure sensor simultaneously. The timings of events determined from the acceleration waveform were compared to the timings determined from the three-dimensional motion analysis data (task onset, maximum trunk inclination) or foot pressure sensor data (first heel strike). Regression analysis was used to estimate the fluidity index from the duration between events. [Results] The characteristics of the acceleration waveform were similar to those previously reported in younger adults. Comparisons of event timings from accelerometer and motion analysis system data indicated no systematic bias. Regression analysis showed that the duration from maximum trunk inclination to the first heel strike was the best predictor of fluidity index. [Conclusion] An accelerometer-based method using the duration between characteristic events may be used to precisely and conveniently assess fluidity in a sit-to-walk task in a community setting. PMID:28210059

  1. Single amino acid changes in domain II of Bacillus thuringiensis CryIAb delta-endotoxin affect irreversible binding to Manduca sexta midgut membrane vesicles.

    PubMed Central

    Rajamohan, F; Alcantara, E; Lee, M K; Chen, X J; Curtiss, A; Dean, D H

    1995-01-01

    Deletion of amino acid residues 370 to 375 (D2) and single alanine substitutions between residues 371 and 375 (FNIGI) of lepidopteran-active Bacillus thuringiensis CryIAb delta-endotoxin were constructed by site-directed mutagenesis techniques. All mutants, except that with the I-to-A change at position 373 (I373A), produced delta-endotoxin as CryIAb and were stable upon activation either by Manduca sexta gut enzymes or by trypsin. Mutants D2, F371A, and G374A lost most of the toxicity (400 times less) for M. sexta larvae, whereas N372A and I375A were only 2 times less toxic than CryIAb. The results of homologous and heterologous competition binding assays to M. sexta midgut brush border membrane vesicles (BBMV) revealed that the binding curves for all mutant toxins were similar to those for the wild-type toxin. However, a significant difference in irreversible binding was observed between the toxic (CryIAb, N372A, and I375A) and less-toxic (D2, F371A, and G374A) proteins. Only 20 to 25% of bound, radiolabeled CryIAb, N372A, and I375A toxins was dissociated from BBMV, whereas about 50 to 55% of the less-toxic mutants, D2, F371A, and G374A, was dissociated from their binding sites by the addition of excess nonlabeled ligand. Voltage clamping experiments provided further evidence that the insecticidal property (inhibition of short-circuit current across the M. sexta midgut) was directly correlated to irreversible interaction of the toxin with the BBMV. We have also shown that CryIAb and mutant toxins recognize 210- and 120-kDa peptides in ligand blotting. Our results imply that mutations in residues 370 to 375 of domain II of CrylAb do not affect overall binding but do affect the irreversible association of the toxin to the midgut columnar epithelial cells of M. sexta. PMID:7730254

  2. The correlation between photosensitizers' membrane localization, membrane-residing targets, and photosensitization efficiency

    NASA Astrophysics Data System (ADS)

    Ytzhak, Shany; Bernstein, Shoshana; Loew, Leslie M.; Ehrenberg, Benjamin

    2009-06-01

    Various tetrapyrroles act as photosensitizers by efficiently generating singlet oxygen. Hydrophobic or amphiphilic photosensitizers are taken up by cells and are usually located in various cellular lipid membranes. Passive uptake by a membrane depends on biophysical properties of the membrane, such as its composition, temperature, phase, fluidity, electric potential etc., as well as on the external solution's properties. Although the intrinsic lifetime of singlet oxygen in the membrane phase is 10-30 μs, depending on lipid composition, it escapes much faster out of the membrane into the external or internal aqueous medium, where its lifetime is <3 μs. Any damage that singlet oxygen might inflict to membrane constituents, i.e. proteins or lipids, must thus occur while it is diffusing in the membrane. As a result, photosensitization efficiency depends, among others, on the location of the sensitizer in the membrane. Singlet oxygen can cause oxidative damage to two classes of targets in the membrane: lipids and proteins. Depolarization of the Nernst electric potential on cells' membranes was observed, but it is not clear whether lipid oxidation is a relevant factor leading to abolishing the resting potential of cells' membranes and to their death. We present a study of the effect of membrane lipid composition and the dissipation of the electric potential that is generated across the membrane. We find a clear correlation between the structure and unsaturation of lipids and the leakage of the membrane, which can be caused by their photosensitized oxidization. We demonstrate here that when liposomes are composed of mixtures similar to natural membranes, and photosensitization is being carried out under usual PDT conditions, photodamage to the lipids is not likely to cause enhanced permeability of ions through the membrane, which could be a mechanism that leads to cell death.

  3. Aspirin Increases the Solubility of Cholesterol in Lipid Membranes

    NASA Astrophysics Data System (ADS)

    Alsop, Richard; Barrett, Matthew; Zheng, Sonbo; Dies, Hannah; Rheinstadter, Maikel

    2014-03-01

    Aspirin (ASA) is often prescribed for patients with high levels of cholesterol for the secondary prevention of myocardial events, a regimen known as the Low-Dose Aspirin Therapy. We have recently shown that Aspirin partitions in lipid bilayers. However, a direct interplay between ASA and cholesterol has not been investigated. Cholesterol is known to insert itself into the membrane in a dispersed state at moderate concentrations (under ~37.5%) and decrease fluidity of membranes. We prepared model lipid membranes containing varying amounts of both ASA and cholesterol molecules. The structure of the bilayers as a function of ASA and cholesterol concentration was determined using high-resolution X-ray diffraction. At cholesterol levels of more than 40mol%, immiscible cholesterol plaques formed. Adding ASA to the membranes was found to dissolve the cholesterol plaques, leading to a fluid lipid bilayer structure. We present first direct evidence for an interaction between ASA and cholesterol on the level of the cell membrane.

  4. Investigating cell membrane structure and dynamics with TCSPC-FLIM

    NASA Astrophysics Data System (ADS)

    Le Marois, Alix; Owen, Dylan M.; Suhling, Klaus

    2015-03-01

    We report the use of Time-Correlated Single Photon Counting (TCSPC) in a polarization-resolved Fluorescence Lifetime Imaging (FLIM) setup for the investigation of cell membrane structural and dynamic properties. This technique allows us to study the orientation and mobility of fluorescent membrane dyes, namely di-4-ANEPPDHQ and DiO, in model bilayers of different lipid compositions. Dipole alignment and extent of rotational motion can be linked to membrane order and fluidity. Comparison of the time-resolved anisotropy decays of the two fluorescent dyes suggests that rotational motion of membrane constituents is restricted in liquid-ordered phases, and appears to be limited to the region of aliphatic tails in liquid-disordered phases. In living cells, understanding the membrane structure provides crucial information on its functional properties, such as exo- and endocytosis, cell mobility and signal transduction.

  5. Ionizing radiation induces structural and functional damage on the molecules of rat brain homogenate membranes: a Fourier transform infrared (FT-IR) spectroscopic study.

    PubMed

    Demir, Pinar; Akkas, Sara B; Severcan, Mete; Zorlu, Faruk; Severcan, Feride

    2015-01-01

    Humans can be exposed to ionizing radiation, due to various reasons, whose structural effects on biological membranes are not well defined. The current study aims to understand the ionizing radiation-induced structural and functional alterations in biomolecules of brain membranes using Fourier transform infrared (FT-IR) spectroscopy using rat animal models. For this purpose, 1000 cGy of ionizing radiation was specifically directed to the head of Sprague Dawley rats. The rats were decapitated after 24 h. The results revealed that the lipid-to-protein ratio decreased and that irradiation caused lipid peroxidation and increases in the amounts of olefinic =CH, carbonyl, and methylene groups of lipids. In addition, ionizing radiation induced a decrease in membrane fluidity, disordering of membrane lipids, strengthening of the hydrogen bonding of the phosphate groups of lipid head-groups, and weakening in the hydrogen bonding of the interfacial carbonyl groups of lipids. Radiation further caused significant decrements in the α-helix and turns, and significant increments in the β-sheet and random coil contents in the protein structure. Hierarchical cluster analyses, performed in the whole region (3030-1000 cm(-1)), lipid (3030-2800 cm(-1)), and protein (1700-1600 cm(-1)) regions separately, successfully differentiated the control and irradiated groups of rat brain membranes and showed that proteins in the membranes are affected more than lipids from the damages induced with ionizing radiation. As a result, the current study showed that FT-IR spectroscopy can be used successfully as a novel method to monitor radiation-induced alterations on biological membranes.

  6. In vivo influence of extract from Aronia melanocarpa on the erythrocyte membranes in patients with hypercholesterolemia

    PubMed Central

    Duchnowicz, Piotr; Nowicka, Agnieszka; Koter-Michalak, Maria; Broncel, Marlena

    2012-01-01

    Summary Background Hypercholesterolemia increases cholesterol concentration in erythrocyte membranes, which results in decrease of membrane fluidity and decreases the deformability of red blood cells. The fruits of Arona melanocarpa contains many of polyphenols and other compounds that have beneficial health effects. Material/Methods The aim of the study was to estimate the influence of 2-month supplementation of extract from Aronia melanocarpa (100 mg Aronox, three times per day) on cholesterol concentration, lipid peroxidation, membrane fluidity, level of thiol groups and activity of ATPase in erythrocytes from patients with hypercholesterolemia. The study involved 25 patients with hypercholesterolemia without pharmacological treatment and 20 healthy individuals as a control group. Blood samples were collected before, and after 1 and 2 months of Aronia administration. Results The 2-month Aronia supplementation resulted in a decrease of cholesterol concentration (by 22%) and a decrease of lipid peroxidation (by 40%), and an increase of membrane fluidity. No statistically significant increase of the concentration of thiol groups and of ATPase activity were observed. Conclusions Our study shows that supplementation of extract from Aronia melanocarpa has a beneficial effect on rheological properties of erythrocytes. PMID:22936193

  7. Caenorhabditis elegans PAQR-2 and IGLR-2 Protect against Glucose Toxicity by Modulating Membrane Lipid Composition

    PubMed Central

    Svensk, Emma; Devkota, Ranjan; Ståhlman, Marcus; Ranji, Parmida; Rauthan, Manish; Magnusson, Fredrik; Hammarsten, Sofia; Johansson, Maja; Borén, Jan; Pilon, Marc

    2016-01-01

    In spite of the worldwide impact of diabetes on human health, the mechanisms behind glucose toxicity remain elusive. Here we show that C. elegans mutants lacking paqr-2, the worm homolog of the adiponectin receptors AdipoR1/2, or its newly identified functional partner iglr-2, are glucose intolerant and die in the presence of as little as 20 mM glucose. Using FRAP (Fluorescence Recovery After Photobleaching) on living worms, we found that cultivation in the presence of glucose causes a decrease in membrane fluidity in paqr-2 and iglr-2 mutants and that genetic suppressors of this sensitivity act to restore membrane fluidity by promoting fatty acid desaturation. The essential roles of paqr-2 and iglr-2 in the presence of glucose are completely independent from daf-2 and daf-16, the C. elegans homologs of the insulin receptor and its downstream target FoxO, respectively. Using bimolecular fluorescence complementation, we also show that PAQR-2 and IGLR-2 interact on plasma membranes and thus may act together as a fluidity sensor that controls membrane lipid composition. PMID:27082444

  8. Deoxycholic acid modulates cell death signaling through changes in mitochondrial membrane properties[S

    PubMed Central

    Sousa, Tânia; Castro, Rui E.; Pinto, Sandra N.; Coutinho, Ana; Lucas, Susana D.; Moreira, Rui; Rodrigues, Cecília M. P.; Prieto, Manuel; Fernandes, Fábio

    2015-01-01

    Cytotoxic bile acids, such as deoxycholic acid (DCA), are responsible for hepatocyte cell death during intrahepatic cholestasis. The mechanisms responsible for this effect are unclear, and recent studies conflict, pointing to either a modulation of plasma membrane structure or mitochondrial-mediated toxicity through perturbation of mitochondrial outer membrane (MOM) properties. We conducted a comprehensive comparative study of the impact of cytotoxic and cytoprotective bile acids on the membrane structure of different cellular compartments. We show that DCA increases the plasma membrane fluidity of hepatocytes to a minor extent, and that this effect is not correlated with the incidence of apoptosis. Additionally, plasma membrane fluidity recovers to normal values over time suggesting the presence of cellular compensatory mechanisms for this perturbation. Colocalization experiments in living cells confirmed the presence of bile acids within mitochondrial membranes. Experiments with active isolated mitochondria revealed that physiologically active concentrations of DCA change MOM order in a concentration- and time-dependent manner, and that these changes preceded the mitochondrial permeability transition. Importantly, these effects are not observed on liposomes mimicking MOM lipid composition, suggesting that DCA apoptotic activity depends on features of mitochondrial membranes that are absent in protein-free mimetic liposomes, such as the double-membrane structure, lipid asymmetry, or mitochondrial protein environment. In contrast, the mechanism of action of cytoprotective bile acids is likely not associated with changes in cellular membrane structure. PMID:26351365

  9. Deoxycholic acid modulates cell death signaling through changes in mitochondrial membrane properties.

    PubMed

    Sousa, Tânia; Castro, Rui E; Pinto, Sandra N; Coutinho, Ana; Lucas, Susana D; Moreira, Rui; Rodrigues, Cecília M P; Prieto, Manuel; Fernandes, Fábio

    2015-11-01

    Cytotoxic bile acids, such as deoxycholic acid (DCA), are responsible for hepatocyte cell death during intrahepatic cholestasis. The mechanisms responsible for this effect are unclear, and recent studies conflict, pointing to either a modulation of plasma membrane structure or mitochondrial-mediated toxicity through perturbation of mitochondrial outer membrane (MOM) properties. We conducted a comprehensive comparative study of the impact of cytotoxic and cytoprotective bile acids on the membrane structure of different cellular compartments. We show that DCA increases the plasma membrane fluidity of hepatocytes to a minor extent, and that this effect is not correlated with the incidence of apoptosis. Additionally, plasma membrane fluidity recovers to normal values over time suggesting the presence of cellular compensatory mechanisms for this perturbation. Colocalization experiments in living cells confirmed the presence of bile acids within mitochondrial membranes. Experiments with active isolated mitochondria revealed that physiologically active concentrations of DCA change MOM order in a concentration- and time-dependent manner, and that these changes preceded the mitochondrial permeability transition. Importantly, these effects are not observed on liposomes mimicking MOM lipid composition, suggesting that DCA apoptotic activity depends on features of mitochondrial membranes that are absent in protein-free mimetic liposomes, such as the double-membrane structure, lipid asymmetry, or mitochondrial protein environment. In contrast, the mechanism of action of cytoprotective bile acids is likely not associated with changes in cellular membrane structure.

  10. Role of membrane biophysics in Alzheimer's–related cell pathways

    PubMed Central

    Zhu, Donghui; Bungart, Brittani L.; Yang, Xiaoguang; Zhumadilov, Zhaxybay; Lee, James C-M.; Askarova, Sholpan

    2015-01-01

    Cellular membrane alterations are commonly observed in many diseases, including Alzheimer's disease (AD). Membrane biophysical properties, such as membrane molecular order, membrane fluidity, organization of lipid rafts, and adhesion between membrane and cytoskeleton, play an important role in various cellular activities and functions. While membrane biophysics impacts a broad range of cellular pathways, this review addresses the role of membrane biophysics in amyloid-β peptide aggregation, Aβ-induced oxidative pathways, amyloid precursor protein processing, and cerebral endothelial functions in AD. Understanding the mechanism(s) underlying the effects of cell membrane properties on cellular processes should shed light on the development of new preventive and therapeutic strategies for this devastating disease. PMID:26074758

  11. Progress in the development of ATHAM-Fluidity: A new high-resolution atmospheric model for simulating localised extreme weather events

    NASA Astrophysics Data System (ADS)

    Savre, Julien; Herzog, Michael; Percival, James; Pain, Chris

    2016-04-01

    Within the framework of the EU FP7-PEARL (Preparing for Extreme And Rare events in coastaL regions) project, a new high-resolution non hydrostatic atmospheric model is currently developed: ATHAM-Fluidity. Unlike many existing atmospheric models, ATHAM-Fluidity's dynamical core is based on a mixed finite-element discretisation designed to operate on unstructured and adaptive meshes, for an optimized use of computational power. The model is designed to simulate extreme weather conditions at local scales (on the order of 50x50 km2) and will ultimately help better understand and assess the impacts of heavy precipitation events in coastal areas. As such, ATHAM-Fluidity will constitute an important component of a suite of multi-physics models, including for example storm surge and flood modelling systems, whose role will particularly consist in producing high-resolution precipitation maps in areas of interest. A series of case studies identified within PEARL (for example Greve, Denmark, an area particularly vulnerable to floods and storm surges) will be further investigated using ATHAM-Fluidity and this integrated modelling framework. In order to successfully achieve its tasks, ATHAM-Fluidity must be equipped with a series of physical parameterisations to capture the formation and evolution of clouds and heavy precipitation. After a careful evaluation of ATHAM-Fluidity under dry atmospheric conditions [Savre et al., submitted to MWR 2015] for which the performances of the dynamical core and mesh adaptivity algorithm have been assessed, the model has recently been extended to handle moist atmospheric conditions and clouds. These new developments include the implementation of ATHAM's active tracer concept to account for atmospheric moisture and hydrometeors, as well as a warm two-moment bulk microphysics scheme to parameterise the formation and evolution of liquid clouds and precipitation. In addition, a turbulence diffusion closure, specifically designed for Large Eddy

  12. Effects of cold water swimming on blood rheological properties and composition of fatty acids in erythrocyte membranes of untrained older rats.

    PubMed

    Teległów, Aneta; Dabrowski, Zbigniew; Marchewka, Anna; Tabarowski, Zbigniew; Bilski, Jan; Jaśkiewicz, Jerzy; Gdula-Argasińska, Joanna; Głodzik, Jacek; Lizak, Dorota; Kepińska, Magdalena

    2011-01-01

    This is the first report on the effects of a single bout of swimming to exhaustion in cold water on rat erythrocyte deformability, aggregation and fatty acid composition in erythrocyte membranes. The results indicate that there was a significant decrease in body temperature of experimental rats swimming in water at 4 degrees C and 25 degrees C when compared to the control. Erythrocyte aggregation indices did not change after swimming in water at 4 degrees C whereas erythrocyte deformability increased at shear stress 1,13 [Pa] and 15,96 [Pa]. Physical effort performed in water at 4 degrees C when compared to the control group resulted in an increase in monounsaturated and polyunsaturated n-3 fatty acid content in erythrocyte membranes that influenced the increase in their fluidity and permeability even though that of polyunsaturated n-6 fatty acids decreased. Physical effort performed in 25 degrees C water resulted in an increase in saturated fatty acid content and a decrease in all polyunsaturated fatty acids and polyunsaturated n-6 fatty acids when compared to the control group. Swimming of untrained old rats in cold water affected rheological properties oferythrocytes in a negligible way while changes in the fatty acid composition of erythrocyte membranes were more pronounced.

  13. Effects of the in vitro administered ethanol and lipopolysaccharide toxin on membrane properties, intracellular free calcium and phagocytic function of isolated rat kupffer cells

    SciTech Connect

    Victorov, A.; Smith, T.; Abril, E.; Hamlin, E.; Earnest, D. )

    1991-03-11

    Low concentrations of ethanol slightly stimulated phagocytosis of cultured Kupffer cells (KC), producing practically no effect on membrane microviscosity and cytosolic free (Ca{sup 2+}){sub i}. On the contrary, high concentrations of ethanol significantly suppressed phagocytic function, increased fluidity of membrane lipids and caused a sustained rise in (Ca{sup 2}){sub i}; above the resting level of 41-85 nM. Treatment of KC with colchicine and cytochalasin B dramatically destructurized the plasma membrane lipids. Short term preincubation of KC with high doses of alcohol stimulated the disordering effects of both drugs, suggesting direct interaction of ethanol with microtubule and microfilament structures. The authors hypothesize that ethanol impairs phagocytosis of KC by concerted actions on membrane lipid fluidity, cytosolic free Ca{sup 2+} and functioning of cytoskeleton. On the other hand, incubation of KC with low concentrations of lipopolysaccharide (LPS) produced no changes in (Ca{sup 2+}){sub i}; or plasma membrane fluidity but reduced by several fold the fluidizing effect of subsequently added ethanol. They suggested that low doses of LPS, by activating second messengers other than Ca{sup 2+}, alter the functioning of the cytoskeleton and cause reorganization of the plasma membrane thus making KC membranes more resistent to the fluidizing action of ethanol and partially restoring the phagocytic function.

  14. Effects of diclofenac on EPC liposome membrane properties.

    PubMed

    Ferreira, Helena; Lúcio, Marlene; Lima, José L F C; Matos, Carla; Reis, Salette

    2005-07-01

    In this work the interaction of a non-steroidal anti-inflammatory drug (NSAID), diclofenac, with egg yolk phosphatidylcoline (EPC) liposomes, used as cell-membrane models, was quantified by determination of the partition coefficient. The liposome/aqueous phase partition coefficient was determined by derivative spectrophotometry, fluorescence quenching, and measurement of zeta-potential. Theoretical models based on simple partition of the diclofenac between two different media, were used to fit the experimental data, enabling the determination of K(p). The three techniques used yielded similar results. The effects of the interaction on the membrane's characteristics were further evaluated, either by studying membrane potential changes or by effects on membrane fluidity. The liposome membrane potential and the size and size-homogeneity of liposomes were measured by light scattering. The effects of diclofenac on the internal viscosity or fluidity of the membrane were determined by use of spectroscopic probes-a series of n-(9-anthroyloxy) fatty acids in which the carboxyl terminal group is located at the interfacial region of the membrane and the fluorescent anthracene group is attached at different positions along the fatty acid chain. The location of the diclofenac on the membrane was also evaluated, by fluorescence quenching using the same series of fluorescent probes. Because the fluorescent anthracene group is attached at different positions along the fatty acid chain, it is possible to label at a graded series of depths in the bilayer. The interactions between the drug and the probe are a means of predicting the location of the drug on the membrane.

  15. Temperature-induced plasticity in membrane and storage lipid composition: thermal reaction norms across five different temperatures.

    PubMed

    Van Dooremalen, Coby; Koekkoek, Jacco; Ellers, Jacintha

    2011-02-01

    Temperature is a key environmental factor inducing phenotypic plasticity in a wide range of behavioral, morphological, and life history traits in ectotherms. The strength of temperature-induced responses in fitness-related traits may be determined by plasticity of the underlying physiological or biochemical traits. Lipid composition may be an important trait underlying fitness response to temperature, because it affects membrane fluidity as well as availability of stored energy reserves. Here, we investigate the effect of temperature on lipid composition of the springtail Orchesella cincta by measuring thermal reaction norms across five different temperatures after four weeks of cold or warm acclimation. Fatty acid composition in storage and membrane lipids showed a highly plastic response to temperature, but the responses of single fatty acids revealed deviations from the expectations based on HVA theory. We found an accumulation of C(18:2n6) and C(18:3n3) at higher temperatures and the preservation of C(20:4n6) across temperatures, which is contrary to the expectation of decreased unsaturation at higher temperatures. The thermal response of these fatty acids in O. cincta differed from the findings in other species, and therefore shows there is interspecific variation in how single fatty acids contribute to HVA. Future research should determine the consequences of such variation in terms of costs and benefits for the thermal performance of species.

  16. Vitamin E supplementation protects erythrocyte membranes from oxidative stress in healthy Chinese middle-aged and elderly people.

    PubMed

    Sun, Yongye; Ma, Aiguo; Li, Yong; Han, Xiuxia; Wang, Qiuzhen; Liang, Hui

    2012-05-01

    Elderly people are subject to higher levels of oxidative stress than are young people. Vitamin E, as a powerful antioxidant residing mainly in biomembranes, may provide effective protection against oxidative membrane damage and resultant age-related deterioration, especially in the elderly. We hypothesized that appropriate levels of vitamin E supplementation would protect erythrocyte membranes from oxidative stress and thus improve membrane fluidity in healthy middle-aged and elderly people. To test this, we conducted a 4-month double-blind, randomized trial in which 180 healthy subjects (55-70 years old) were randomly divided into 4 groups: group C (control), and 3 treatment groups in which daily doses of 100 mg (VE1), 200 mg (VE2), and 300 mg (VE3) dl-α-tocopheryl acetate were administered. We measured plasma α-tocopherol concentration, malondialdehyde, and superoxide dismutase levels, erythrocyte hemolysis, and erythrocyte membrane fluidity at the beginning and end of the trial. After 4 months supplementation, plasma α-tocopherol concentrations in the 3 treatment groups had increased by 71%, 78%, and 95%, respectively (all P < .01), and significant decreases in plasma malondialdehyde concentrations were observed in these groups (all P < .05). Erythrocyte hemolysis was decreased by 20% to 38% after vitamin E supplementation (all P < .05), and in addition, groups VE2 and VE3 showed dramatic improvements in erythrocyte membrane fluidity (P < .01). Surprisingly, superoxide dismutase activity also decreased significantly in the treatment groups (all P < .05). In summary, vitamin E supplementation apparently alleviates oxidative stress in healthy middle-aged to elderly people, at least in part by improving erythrocyte membrane fluidity and reducing erythrocyte hemolysis.

  17. High heterogeneity of plasma membrane microfluidity in multidrug-resistant cancer cells

    NASA Astrophysics Data System (ADS)

    Boutin, Céline; Roche, Yann; Millot, Christine; Deturche, Régis; Royer, Pascal; Manfait, Michel; Plain, Jérôme; Jeannesson, Pierre; Millot, Jean-Marc; Jaffiol, Rodolphe

    2009-05-01

    Diffusion-time distribution analysis (DDA) has been used to explore the plasma membrane fluidity of multidrug-resistant cancer cells (LR73 carcinoma cells) and also to characterize the influence of various membrane agents present in the extracellular medium. DDA is a recent single-molecule technique, based on fluorescence correlation spectroscopy (FCS), well suited to retrieve local organization of cell membrane. The method was conducted on a large number of living cells, which enabled us to get a detailed overview of plasma membrane microviscosity, and plasma membrane micro-organization, between the cells of the same line. Thus, we clearly reveal the higher heterogeneity of plasma membrane in multidrug-resistant cancer cells in comparison with the nonresistant ones (denoted sensitive cells). We also display distinct modifications related to a membrane fluidity modulator, benzyl alcohol, and two revertants of multidrug resistance, verapamil and cyclosporin-A. A relation between the distribution of the diffusion-time values and the modification of membrane lateral heterogeneities is proposed.

  18. Studies on the interactions of bisphenols with anionic phospholipids of decomposer membranes in model systems.

    PubMed

    Broniatowski, Marcin; Sobolewska, Katarzyna; Flasiński, Michał; Wydro, Paweł

    2016-04-01

    Bisphenol A (BPA) and other bisphenols constitute a class of organic pollutants, which because of their estrogenic properties, low dose activity and bioaccumulation pose considerable risk for public health as well as for the environment. Accumulated in the sediment bisphenols can endanger the decomposers' populations being incorporated into their cellular membranes; however, the mechanism of their membrane activity is unknown. Therefore, to study these phenomena we applied anionic phospholipid Langmuir monolayers as simple but versatile models of decomposers biomembranes. Phosphatidylglycerols and cardiolipins are not only the main components of bacterial membranes but also of crucial importance in mitochondrial and thylakoid membranes in eukaryotic cells. In our investigations we applied five compounds of the bisphenol class most commonly detected in the environment. To characterize the bisphenols-model membrane interactions we applied multiple mutually independent methods of physical chemistry; namely: the Langmuir monolayer technique, surface potential measurements, Brewster angle microscopy for the visualization of the monolayers' texture and grazing incidence X-ray diffraction for the discussion of the phospholipids packing within the monolayers. Our studies indicated that all the investigated bisphenols interact with the model membrane, but the strength of the interactions is dependent on the bisphenol structure and hydrophobicity and the fluidity of the model membranes. We proved that bisphenol S often treated as the least toxic BPA analog can also be incorporated to the model membranes changing their structure and fluidity.

  19. How does plasmid DNA penetrate cell membranes in artificial transformation process of Escherichia coli?

    PubMed

    Panja, Subrata; Aich, Pulakesh; Jana, Bimal; Basu, Tarakdas

    2008-08-01

    Artificial transformation of Escherichia coli with plasmid DNA in presence of CaCl2 is a widely used technique in recombinant DNA technology. However, exact mechanism of DNA transfer across cell membranes is largely obscure. In this study, measurements of both steady state and time-resolved anisotropies of fluorescent dye trimethyl ammonium diphenyl hexatriene (TMA-DPH), bound to cellular outer membrane, indicated heat-pulse (0 degrees C42 degrees C) step of the standard transformation procedure had lowered considerably outer membrane fluidity of cells. The decrease in fluidity was caused by release of lipids from cell surface to extra-cellular medium. A subsequent cold-shock (42 degrees C0 degrees C) to the cells raised the fluidity further to its original value and this was caused by release of membrane proteins to extra-cellular medium. When the cycle of heat-pulse and cold-shock steps was repeated, more release of lipids and proteins respectively had taken place, which ultimately enhanced transformation efficiency gradually up to third cycle. Study of competent cell surface by atomic force microscope showed release of lipids had formed pores on cell surface. Moreover, the heat-pulse step almost depolarized cellular inner membrane. In this communication, we propose heat-pulse step had two important roles on DNA entry: (a) Release of lipids and consequent formation of pores on cell surface, which helped DNA to cross outer membrane barrier, and (b) lowering of membrane potential, which facilitated DNA to cross inner membrane of E. coli.

  20. A vacuolar membrane protein affects drastically the biosynthesis of the ACV tripeptide and the beta-lactam pathway of Penicillium chrysogenum.

    PubMed

    Fernández-Aguado, Marta; Teijeira, Fernando; Martín, Juan F; Ullán, Ricardo V

    2013-01-01

    The knowledge about enzymes' compartmentalization and transport processes involved in the penicillin biosynthesis in Penicillium chrysogenum is very limited. The genome of this fungus contains multiple genes encoding transporter proteins, but very little is known about them. A bioinformatic search was made to find major facilitator supefamily (MFS) membrane proteins related to CefP transporter protein involved in the entry of isopenicillin N to the peroxisome in Acremonium chrysogenum. No strict homologue of CefP was observed in P. chrysogenum, but the penV gene was found to encode a membrane protein that contained 10 clear transmembrane spanners and two other motifs COG5594 and DUF221, typical of membrane proteins. RNAi-mediated silencing of penV gene provoked a drastic reduction of the production of the δ-(L-α-aminoadipyl-L-cysteinyl-D-valine) (ACV) and isopenicillin N intermediates and the final product of the pathway. RT-PCR and northern blot analyses confirmed a reduction in the expression levels of the pcbC and penDE biosynthetic genes, whereas that of the pcbAB gene increased. Localization studies by fluorescent laser scanning microscopy using Dsred and GFP fluorescent fusion proteins and the FM 4-64 fluorescent dye showed clearly that the protein was located in the vacuolar membrane. These results indicate that PenV participates in the first stage of the beta-lactam biosynthesis (i.e., the formation of the ACV tripeptide), probably taking part in the supply of amino acids from the vacuolar lumen to the vacuole-anchored ACV synthetase. This is in agreement with several reports on the localization of the ACV synthetase and provides increased evidence for a compartmentalized storage of precursor amino acids for non-ribosomal peptides. PenV is the first MFS transporter of P. chrysogenum linked to the beta-lactam biosynthesis that has been located in the vacuolar membrane.

  1. Coal lithotypes before and after saturation with CO2; insights from micro- and mesoporosity, fluidity, and functional group distribution

    USGS Publications Warehouse

    Mastalerz, Maria; Drobniak, A.; Walker, R.; Morse, D.

    2010-01-01

    Four lithotypes, vitrain, bright clarain, clarain, and fusain, were hand-picked from the core of the Pennsylvanian Springfield Coal Member (Petersburg Formation) in Illinois. These lithotypes were analyzed petrographically and for meso- and micropore characteristics, functional group distribution using FTIR techniques, and fluidity. High-pressure CO2 adsorption isotherm analyses of these lithotypes were performed and, subsequently, all samples were reanalyzed in order to investigate the effects of CO2. After the high-pressure adsorption isotherm analysis was conducted and the samples were reanalyzed, there was a decrease in BET surface area for vitrain from 31.5m2/g in the original sample to 28.5m2/g, as determined by low-pressure nitrogen adsorption. Bright clarain and clarain recorded a minimal decrease in BET surface area, whereas for fusain there was an increase from 6.6m2/g to 7.9m2/g. Using low-pressure CO2 adsorption techniques, a small decrease in the quantity of the adsorbed CO2 is recorded for vitrain and bright clarain, no difference is observed for clarain, and there is an increase in the quantity of the adsorbed CO2 for fusain. Comparison of the FTIR spectra before and after CO2 injection for all lithotypes showed no differences with respect to functional group distribution, testifying against chemical nature of CO2 adsorption. Gieseler plastometry shows that: 1) softening temperature is higher for the post-CO2 sample (389.5??C vs. 386??C); 2) solidification temperature is lower for the post-CO2 sample (443.5??C vs. 451??C); and 3) the maximum fluidity is significantly lower for the post-CO2 sample (4 ddpm vs. 14 ddpm). ?? 2010 Elsevier B.V.

  2. Mapping structural landmarks, ligand binding sites, and missense mutations to the collagen IV heterotrimers predicts major functional domains, novel interactions, and variation in phenotypes in inherited diseases affecting basement membranes.

    PubMed

    Parkin, J Des; San Antonio, James D; Pedchenko, Vadim; Hudson, Billy; Jensen, Shane T; Savige, Judy

    2011-02-01

    Collagen IV is the major protein found in basement membranes. It comprises three heterotrimers (α1α1α2, α3α4α5, and α5α5α6) that form distinct networks, and are responsible for membrane strength and integrity.We constructed linear maps of the collagen IV heterotrimers ("interactomes") that indicated major structural landmarks, known and predicted ligand-binding sites, and missense mutations, in order to identify functional and disease-associated domains, potential interactions between ligands, and genotype–phenotype relationships. The maps documented more than 30 known ligand-binding sites as well as motifs for integrins, heparin, von Willebrand factor (VWF), decorin, and bone morphogenetic protein (BMP). They predicted functional domains for angiogenesis and haemostasis, and disease domains for autoimmunity, tumor growth and inhibition, infection, and glycation. Cooperative ligand interactions were indicated by binding site proximity, for example, between integrins, matrix metalloproteinases, and heparin. The maps indicated that mutations affecting major ligand-binding sites, for example, for Von Hippel Lindau (VHL) protein in the α1 chain or integrins in the α5 chain, resulted in distinctive phenotypes (Hereditary Angiopathy, Nephropathy, Aneurysms, and muscle Cramps [HANAC] syndrome, and early-onset Alport syndrome, respectively). These maps further our understanding of basement membrane biology and disease, and suggest novel membrane interactions, functions, and therapeutic targets.

  3. Membrane interactivity of charged local anesthetic derivative and stereoselectivity in membrane interaction of local anesthetic enantiomers

    PubMed Central

    Tsuchiya, Hironori; Mizogami, Maki

    2008-01-01

    With respect to the membrane lipid theory as a molecular mechanism for local anesthetics, two critical subjects, the negligible effects of charged drugs when applied extracellularly and the stereoselective effects of enantiomers, were verified by paying particular attention to membrane components, phospholipids with the anionic property, and cholesterol with several chiral carbons. The membrane interactivities of structurally-different anesthetics were determined by their induced fluidity changes of liposomal membranes. Lidocaine (3.0 μmol/mL) fluidized phosphatidylcholine membranes, but not its quaternary derivative QX-314 (3.0 μmol/mL). Similarly to the mother molecule lidocaine, however, QX-314 fluidized phosphatidylserine-containing nerve cell model membranes and acidic phospholipids-constituting membranes depending on the acidity of membrane lipids. Positively charged local anesthetics are able to act on lipid bilayers by ion-pairing with anionic (acidic) phospholipids. Bupivacaine (0.75 mol/mL) and ropivacaine (0.75 and 1.0 μmol/mL) fluidized nerve cell model membranes with the potency being S(−)-enantiomer < racemate < R(+)-enantiomer (P < 0.01, vs antipode and racemate) and cardiac cell model membranes with the potency being S(−)-ropivacaine < S(−)-bupivacaine < R(+)-bupivacaine (P < 0.01). However, their membrane effects were not different when removing cholesterol from the model membranes. Stereoselectivity is producible by cholesterol which increases the chirality of lipid bilayers and enables to discriminate anesthetic enantiomers. The membrane lipid interaction should be reevaluated as the mode of action of local anesthetics. PMID:22915858

  4. Membrane interactivity of charged local anesthetic derivative and stereoselectivity in membrane interaction of local anesthetic enantiomers.

    PubMed

    Tsuchiya, Hironori; Mizogami, Maki

    2008-01-01

    With respect to the membrane lipid theory as a molecular mechanism for local anesthetics, two critical subjects, the negligible effects of charged drugs when applied extracellularly and the stereoselective effects of enantiomers, were verified by paying particular attention to membrane components, phospholipids with the anionic property, and cholesterol with several chiral carbons. The membrane interactivities of structurally-different anesthetics were determined by their induced fluidity changes of liposomal membranes. Lidocaine (3.0 μmol/mL) fluidized phosphatidylcholine membranes, but not its quaternary derivative QX-314 (3.0 μmol/mL). Similarly to the mother molecule lidocaine, however, QX-314 fluidized phosphatidylserine-containing nerve cell model membranes and acidic phospholipids-constituting membranes depending on the acidity of membrane lipids. Positively charged local anesthetics are able to act on lipid bilayers by ion-pairing with anionic (acidic) phospholipids. Bupivacaine (0.75 mol/mL) and ropivacaine (0.75 and 1.0 μmol/mL) fluidized nerve cell model membranes with the potency being S(-)-enantiomer < racemate < R(+)-enantiomer (P < 0.01, vs antipode and racemate) and cardiac cell model membranes with the potency being S(-)-ropivacaine < S(-)-bupivacaine < R(+)-bupivacaine (P < 0.01). However, their membrane effects were not different when removing cholesterol from the model membranes. Stereoselectivity is producible by cholesterol which increases the chirality of lipid bilayers and enables to discriminate anesthetic enantiomers. The membrane lipid interaction should be reevaluated as the mode of action of local anesthetics.

  5. Cholesterol Asymmetry in Synaptic Plasma Membranes

    PubMed Central

    Wood, W. Gibson; Igbavboa, Urule; Müller, Walter E.; Eckert, Gunter P.

    2010-01-01

    Lipids are essential for the structural and functional integrity of membranes. Membrane lipids are not randomly distributed but are localized in different domains. A common characteristic of these membrane domains is their association with cholesterol. Lipid rafts and caveolae are examples of cholesterol enriched domains, which have attracted keen interest. However, two other important cholesterol domains are the exofacial and cytofacial leaflets of the plasma membrane. The two leaflets that make up the bilayer differ in their fluidity, electrical charge, lipid distribution, and active sites of certain proteins. The synaptic plasma membrane (SPM) cytofacial leaflet contains over 85% of the total SPM cholesterol as compared with the exofacial leaflet. This asymmetric distribution of cholesterol is not fixed or immobile but can be modified by different conditions in vivo: 1) chronic ethanol consumption; 2) statins; 3) aging; and 4) apoE isoform. Several potential candidates have been proposed as mechanisms involved in regulation of SPM cholesterol asymmetry: apoE, low-density-lipoprotein receptor, sterol carrier protein-2, fatty acid binding proteins, polyunsaturated fatty acids, p-glycoprotein and caveolin-1. This review examines cholesterol asymmetry in SPM, potential mechanisms of regulation and impact on membrane structure and function. PMID:21214553

  6. Polyarylether composition and membrane

    DOEpatents

    Hung, Joyce; Brunelle, Daniel Joseph; Harmon, Marianne Elisabeth; Moore, David Roger; Stone, Joshua James; Zhou, Hongyi; Suriano, Joseph Anthony

    2010-11-09

    A composition including a polyarylether copolymer is provided. The copolymer includes a polyarylether backbone; and a sulfonated oligomeric group bonded to the polyarylether suitable for use as a cation conducting membrane. Method of bonding a sulfonated oligomeric group to the polyarylether backbone to form a polyarylether copolymer. The membrane may be formed from the polyarylether copolymer composition. The chain length of the sulfonated oligomeric group may be controlled to affect or control the ion conductivity of the membrane.

  7. The effect of membrane fluidization on protein kinase C: Inhibition by ethanol and higher alcohols and stimulation by increased lipid unsaturation or addition non-esterified fatty acids

    SciTech Connect

    Cox, K.J.A.; Rubin, E.; Stubbs, C.D. )

    1992-01-01

    Protein kinase C (PKC) is a membrane bound enzyme that is dependent on calcium, anionic phospholipids, and sn-1,2-diacylglycerol (DAG) to be fully active. The relationship between membrane fluidity and PKC activity was investigated using model vesicle systems composed of phosphatidylserine alone or in combination with phosphatidylcholine. Effects on membrane fluidity were assessed using the fluorescence anisotropy of diphenylhexatriene. When membrane fluidity was increased by the addition of short chain n-alkanols, PKC activity was inhibited. There was a linear relationship for a given level of inhibition and the membrane-buffer partition coefficient. By contrast, when the degree of unsaturation in the phosphatidylcholine was increased, although the bilayer was again fluidized, PKC activity was enhanced. The addition of non-esterified fatty acid also activated PKC, either when directly added to the vesicles or when generated by the addition of exogenous phospholipase A[sub 2], and again the bilayer was fluidized. It is proposed that a more fluid membrane lipid bilayer, induced by increased unsaturation or non-esterified fatty acids, facilitated optimal interaction at the DAG site since the effect could be demonstrated in a lipid free system using protamine sulfate.

  8. Water Deficit Affects Primary Metabolism Differently in Two Lolium multiflorum/Festuca arundinacea Introgression Forms with a Distinct Capacity for Photosynthesis and Membrane Regeneration

    PubMed Central

    Perlikowski, Dawid; Czyżniejewski, Mariusz; Marczak, Łukasz; Augustyniak, Adam; Kosmala, Arkadiusz

    2016-01-01

    Understanding how plants respond to drought at different levels of cell metabolism is an important aspect of research on the mechanisms involved in stress tolerance. Furthermore, a dissection of drought tolerance into its crucial components by the use of plant introgression forms facilitates to analyze this trait more deeply. The important components of plant drought tolerance are the capacity for photosynthesis under drought conditions, and the ability of cellular membrane regeneration after stress cessation. Two closely related introgression forms of Lolium multiflorum/Festuca arundinacea, differing in the level of photosynthetic capacity during stress, and in the ability to regenerate their cellular membranes after stress cessation, were used as forage grass models in a primary metabolome profiling and in an evaluation of chloroplast 1,6-bisphosphate aldolase accumulation level and activity, during 11 days of water deficit, followed by 10 days of rehydration. It was revealed here that the introgression form, characterized by the ability to regenerate membranes after rehydration, contained higher amounts of proline, melibiose, galactaric acid, myo-inositol and myo-inositol-1-phosphate involved in osmoprotection and stress signaling under drought. Moreover, during the rehydration period, this form also maintained elevated accumulation levels of most the primary metabolites, analyzed here. The other introgression form, characterized by the higher capacity for photosynthesis, revealed a higher accumulation level and activity of chloroplast aldolase under drought conditions, and higher accumulation levels of most photosynthetic products during control and drought periods. The potential impact of the observed metabolic alterations on cellular membrane recovery after stress cessation, and on a photosynthetic capacity under drought conditions in grasses, are discussed. PMID:27504113

  9. Water Deficit Affects Primary Metabolism Differently in Two Lolium multiflorum/Festuca arundinacea Introgression Forms with a Distinct Capacity for Photosynthesis and Membrane Regeneration.

    PubMed

    Perlikowski, Dawid; Czyżniejewski, Mariusz; Marczak, Łukasz; Augustyniak, Adam; Kosmala, Arkadiusz

    2016-01-01

    Understanding how plants respond to drought at different levels of cell metabolism is an important aspect of research on the mechanisms involved in stress tolerance. Furthermore, a dissection of drought tolerance into its crucial components by the use of plant introgression forms facilitates to analyze this trait more deeply. The important components of plant drought tolerance are the capacity for photosynthesis under drought conditions, and the ability of cellular membrane regeneration after stress cessation. Two closely related introgression forms of Lolium multiflorum/Festuca arundinacea, differing in the level of photosynthetic capacity during stress, and in the ability to regenerate their cellular membranes after stress cessation, were used as forage grass models in a primary metabolome profiling and in an evaluation of chloroplast 1,6-bisphosphate aldolase accumulation level and activity, during 11 days of water deficit, followed by 10 days of rehydration. It was revealed here that the introgression form, characterized by the ability to regenerate membranes after rehydration, contained higher amounts of proline, melibiose, galactaric acid, myo-inositol and myo-inositol-1-phosphate involved in osmoprotection and stress signaling under drought. Moreover, during the rehydration period, this form also maintained elevated accumulation levels of most the primary metabolites, analyzed here. The other introgression form, characterized by the higher capacity for photosynthesis, revealed a higher accumulation level and activity of chloroplast aldolase under drought conditions, and higher accumulation levels of most photosynthetic products during control and drought periods. The potential impact of the observed metabolic alterations on cellular membrane recovery after stress cessation, and on a photosynthetic capacity under drought conditions in grasses, are discussed.

  10. Mutagenesis of a novel gene in the prcA-prtP protease locus affects expression of Treponema denticola membrane complexes.

    PubMed

    Bian, Xue-Lin; Wang, Hong-Tao; Ning, Yu; Lee, Si Young; Fenno, J Christopher

    2005-02-01

    A novel gene was identified in the Treponema denticola prcA-prtP protease operon. Strains with mutations in either the prcA-prtP or the msp region showed altered expression of a product(s) of the other locus. Together, these results provide information on the assembly of outer membrane complexes involved in T. denticola interaction with host cells and tissue.

  11. Mutagenesis of a Novel Gene in the prcA-prtP Protease Locus Affects Expression of Treponema denticola Membrane Complexes

    PubMed Central

    Bian, Xue-lin; Wang, Hong-tao; Ning, Yu; Lee, Si Young; Fenno, J. Christopher

    2005-01-01

    A novel gene was identified in the Treponema denticola prcA-prtP protease operon. Strains with mutations in either the prcA-prtP or the msp region showed altered expression of a product(s) of the other locus. Together, these results provide information on the assembly of outer membrane complexes involved in T. denticola interaction with host cells and tissue. PMID:15664975

  12. Fluorescence generalized polarization of cell membranes: a two-photon scanning microscopy approach.

    PubMed Central

    Yu, W; So, P T; French, T; Gratton, E

    1996-01-01

    We use the lipophilic fluorescence probe Laurdan to study cell membranes. The generalized polarization (GP) of Laurdan-labeled cells contains useful information about membrane fluidity and polarity. A high GP is usually associated with low fluidity, low polarity, or high cholesterol content of the membranes, and a low GP is the opposite. We have combined the GP method and two-photon fluorescence microscopy to provide an alternative approach to study cell membranes. Using two-photon excitation in a conventional microscope offers great advantages for studying biological samples. These advantages include efficient background rejection, low photodamage, and improved depth discrimination. We performed GP measurements on mouse fibroblast cells and observed that both intensity and GP images are not spatially uniform. We tested for possible GP artifacts arising from cellular autofluorescence and lifetime quenching, using a procedure for background fluorescence subtraction and by direct lifetime measurements in the microscope. GP measured in a single cell displays a broad distribution, and the GP of 40 different cells grown on the same cover glass is also statistically distributed. The correlations between intensity and GP images were analyzed, and no monotonic dependence between the two was found. By digitally separating high and low GP values, we found that high GP values often associate with the regions of the plasma membrane and low GP values link with the nuclear membranes. Our results also show local GP variations within the plasma and nuclear membranes. Images FIGURE 1 FIGURE 3 FIGURE 5 FIGURE 6 FIGURE 7 PMID:8789081

  13. Redistribution of Cholesterol in Model Lipid Membranes in Response to the Membrane-Active Peptide Alamethicin

    NASA Astrophysics Data System (ADS)

    Heller, William; Qian, Shuo

    2013-03-01

    The cellular membrane is a heterogeneous, dynamic mixture of molecules and macromolecules that self-assemble into a tightly-regulated functional unit that provides a semipermeable barrier between the cell and its environment. Among the many compositional differences between mammalian and bacterial cell membranes that impact its physical properties, one key difference is cholesterol content, which is more prevalent in mammals. Cholesterol is an amphiphile that associates with membranes and serves to maintain its fluidity and permeability. Membrane-active peptides, such as the alpha-helical peptide alamethicin, interact with membranes in a concentration- and composition-dependent manner to form transmembrane pores that are responsible for the lytic action of the peptide. Through the use of small-angle neutron scattering and deuterium labeling, it was possible to observe a redistribution of the lipid and cholesterol in unilamellar vesicles in response to the presence of alamethicin at a peptide-to-lipid ratio of 1/200. The results demonstrate that the membrane remodeling powers of alamethicin reach beyond the membrane thinning effect to altering the localization of specific components in the bilayer, complementing the accepted two-state mechanism of pore formation. Research was supported by U. S. DOE-OBER (CSMB; FWP ERKP291) and the U. S. DOE-BES Scientific User Facilities Division (ORNL's SNS and HFIR).

  14. Biosynthesis of archaeal membrane ether lipids

    PubMed Central

    Jain, Samta; Caforio, Antonella; Driessen, Arnold J. M.

    2014-01-01

    A vital function of the cell membrane in all living organism is to maintain the membrane permeability barrier and fluidity. The composition of the phospholipid bilayer is distinct in archaea when compared to bacteria and eukarya. In archaea, isoprenoid hydrocarbon side chains are linked via an ether bond to the sn-glycerol-1-phosphate backbone. In bacteria and eukarya on the other hand, fatty acid side chains are linked via an ester bond to the sn-glycerol-3-phosphate backbone. The polar head groups are globally shared in the three domains of life. The unique membrane lipids of archaea have been implicated not only in the survival and adaptation of the organisms to extreme environments but also to form the basis of the membrane composition of the last universal common ancestor (LUCA). In nature, a diverse range of archaeal lipids is found, the most common are the diether (or archaeol) and the tetraether (or caldarchaeol) lipids that form a monolayer. Variations in chain length, cyclization and other modifications lead to diversification of these lipids. The biosynthesis of these lipids is not yet well understood however progress in the last decade has led to a comprehensive understanding of the biosynthesis of archaeol. This review describes the current knowledge of the biosynthetic pathway of archaeal ether lipids; insights on the stability and robustness of archaeal lipid membranes; and evolutionary aspects of the lipid divide and the LUCA. It examines recent advances made in the field of pathway reconstruction in bacteria. PMID:25505460

  15. Stereostructure-based differences in the interactions of cardiotoxic local anesthetics with cholesterol-containing biomimetic membranes.

    PubMed

    Tsuchiya, Hironori; Ueno, Takahiro; Mizogami, Maki

    2011-06-01

    Amide-type pipecoloxylidide local anesthetics, bupivacaine, and ropivacaine, show cardiotoxic effects with the potency depending on stereostructures. Cardiotoxic drugs not only bind to cardiomyocyte membrane channels to block them but also modify the physicochemical property of membrane lipid bilayers in which channels are embedded. The opposite configurations allow enantiomers to be discriminated by their enantiospecific interactions with another chiral molecule in membranes. We compared the interactions of local anesthetic stereoisomers with biomimetic membranes consisting of chiral lipid components, the differences of which might be indicative of the drug design for reducing cardiotoxicity. Fluorescent probe-labeled biomimetic membranes were prepared with cardiolipin and cholesterol of varying compositions and different phospholipids. Local anesthetics were reacted with the membrane preparations at a cardiotoxically relevant concentration of 200 μM. The potencies to interact with biomimetic membranes and change their fluidity were compared by measuring fluorescence polarization. All local anesthetics acted on lipid bilayers to increase membrane fluidity. Chiral cardiolipin was ineffective in discriminating S(-)-enantiomers from their antipodes. On the other hand, cholesterol produced the enantiospecific membrane interactions of bupivacaine and ropivacaine with increasing its composition in membranes. In 40 mol% and more cholesterol-containing membranes, the membrane-interacting potency was S(-)-bupivacainemembranes in increasing order of intensity. The rank order of membrane interactivity agreed with that of known cardiotoxicity. The stereoselective membrane interactions determined by cholesterol with higher chirality appears to be associated with the

  16. Membrane stabilizer

    DOEpatents

    Mingenbach, William A.

    1988-01-01

    A device is provided for stabilizing a flexible membrane secured within a frame, wherein a plurality of elongated arms are disposed radially from a central hub which penetrates the membrane, said arms imposing alternately against opposite sides of the membrane, thus warping and tensioning the membrane into a condition of improved stability. The membrane may be an opaque or translucent sheet or other material.

  17. Leucine transport is affected by Bacillus thuringiensis Cry1 toxins in brush border membrane vesicles from Ostrinia nubilalis Hb (Lepidoptera: Pyralidae) and Sesamia nonagrioides Lefebvre (Lepidoptera: Noctuidae) midgut.

    PubMed

    Leonardi, M Giovanna; Caccia, Silvia; González-Cabrera, Joel; Ferré, Juan; Giordana, Barbara

    2006-01-01

    The pore-forming activity of Cry1Ab, Cry1Fa and Cry1Ca toxins and their interaction with leucine transport mediated by the K(+)/leucine cotransporter were studied in brush border membrane vesicles (BBMVs) isolated from the midgut of Ostrinia nubilalis and Sesamia nonagrioides. In both species, as in other Lepidoptera, leucine uptake by BBMVs can take place in the absence of cations, but it can also be driven by a K(+) gradient. Experiments with the voltage-sensitive fluorescent dye 3,3'-diethylthiacarbocyanine iodide proved that Cry1Ab, a Bacillus thuringiensis toxin active in vivo, enhanced the membrane permeability to potassium in O. nubilalis BBMVs. This result is in agreement with similar effects observed in S. nonagrioides BBMV incubated with various Cry1 toxins active in vivo. The effect of the above toxins was tested on the initial rate of 0.1 mM: leucine influx. Instead of an increase in leucine influx, a reduction was observed with the Cry1 toxins active in vivo. Cry1Ab and Cry1Fa, but not the inactive toxin Cry1Da, inhibited in a dose-dependent manner leucine uptake both in the absence and in the presence of a K(+) gradient, a clear indication that their effect is independent of the channel formed by the toxins and that this effect is exerted directly on the amino acid transport system.

  18. Arabidopsis acyl-CoA-binding proteins ACBP4 and ACBP5 are subcellularly localized to the cytosol and ACBP4 depletion affects membrane lipid composition.

    PubMed

    Xiao, Shi; Li, Hong-Ye; Zhang, Jiao-Ping; Chan, Suk-Wah; Chye, Mee-Len

    2008-12-01

    In Arabidopsis thaliana, acyl-CoA-binding proteins (ACBPs) are encoded by six genes, and they display varying affinities for acyl-CoA esters. Recombinant ACBP4 and ACBP5 have been shown to bind oleoyl-CoA esters in vitro. In this study, the subcellular localizations of ACBP4 and ACBP5 were determined by biochemical fractionation followed by western blot analyses using anti-ACBP4 and anti-ACBP5 antibodies and immuno-electron microscopy. Confocal microscopy of autofluorescence-tagged ACBP4 and ACBP5, expressed transiently in onion epidermal cells and in transgenic Arabidopsis, confirmed their expression in the cytosol. Taken together, ACBP4 and ACBP5 are available in the cytosol to bind and transfer cytosolic oleoyl-CoA esters. Lipid profile analysis further revealed that an acbp4 knockout mutant showed decreases in membrane lipids (digalactosyldiacylglycerol, monogalactosyldiacylglycerol, phosphatidylcholine, phosphatidylethanolamine and phosphatidylinositol) while acbp4-complemented lines attained levels similar to wild type, suggesting that ACBP4 plays a role in the biosynthesis of membrane lipids including galactolipids and phospholipids.

  19. Oral administration of fumonisin B1 and T-2 individually and in combination affects hepatic total and mitochondrial membrane lipid profile of rabbits.

    PubMed

    Szabó, A; Szabó-Fodor, J; Fébel, H; Mézes, M; Bajzik, G; Kovács, M

    2016-09-01

    Weaned rabbits were fed diets contaminated with 2 mg/kg diet T-2 toxin alone, or 10 mg/kg diet fumonisin B1 (FB1) alone, and both toxins in combination (2 + 10 mg/kg, respectively) compared to a toxin-free control diet. Samplings were performed after 4 weeks (blood and liver). Bodyweight of T-2-fed group was lower after 4 weeks; the liver weight was increased dramatically (threefold of control). Liver total phospholipids (PLs) provided slight alterations in the fatty acid (FA) composition; all three toxin-treated groups showed a decrease in palmitoleic acid (C16:1 n7) proportion. In the liver mitochondrial PL FA composition, margaric acid (C17:0) proportion decreased in the separated toxin treatments compared to the combined setting. Oleic acid (C18:1 n9) proportion was increased and arachidonic acid (C20:4 n6) was decreased in the FB1-treated group, while docosapentaenoic acid (C22:5 n3) was decreased in the separated treatments. The total monounsaturation was significantly higher in the FB1 group's mitochondrial PL FA profile. After 4 weeks, all toxin treatments decreased the blood plasma reduced glutathione and glutathione peroxidase activity, and FB1 increased the plasma sphinganine/sphingosine ratio. Both mycotoxins seem to cross the hepatocellular and the hepatic mitochondrial membrane, without drastic membrane disruption, as assessed from the PL FA composition, but inducing detectable lipid peroxidation.

  20. Linking membrane physical properties and low temperature tolerance in arthropods.

    PubMed

    Waagner, Dorthe; Bouvrais, Hélène; Ipsen, John H; Holmstrup, Martin

    2013-12-01

    Maintenance of membrane fluidity is of crucial importance in ectotherms experiencing thermal changes. This maintenance has in ectotherms most often been indicated using indirect measures of biochemical changes of phospholipid membranes, which is then assumed to modulate the physico-chemical properties of the membrane. Here, we measure bending rigidity characterizing the membrane flexibility of re-constituted membrane vesicles to provide a more direct link between membrane physical characteristics and low temperature tolerance. Bending rigidity of lipid bilayers was measured in vitro using Giant Unilamellar Vesicles formed from phospholipid extracts of the springtail, Folsomia candida. The bending rigidity of these membranes decreased when exposed to 0.4 vol% ethanol (0.23 mM/L). Springtails exposed to ethanol for 24h significantly increased their cold shock tolerance. Thus, by chemically inducing decreased membrane rigidity, we have shown a direct link between the physico-chemical properties of the membranes and the capacity to tolerate low temperature in a chill-susceptible arthropod.

  1. Interaction of gentamicin polycation with model and cell membranes.

    PubMed

    Kovács, Eugenia; Savopol, Tudor; Iordache, Maria-Minodora; Săplăcan, Lavinia; Sobaru, Iuliana; Istrate, Claudia; Mingeot-Leclercq, Marie-Paule; Moisescu, Mihaela-Georgeta

    2012-10-01

    The interaction of positively-charged antibiotic gentamicin with cell membranes was studied to determine if any changes in membrane organization were induced by the drug. Opossum kidney epithelia (OK) cells were used as models of eukaryotic cells. Two methods were used: laurdan fluorescence spectroscopy and fluorescence anisotropy recordings on 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene p-toluenesulfonate (TMA-DPH) labeled cell suspensions. Both methods showed an altered membrane hydration and fluidity of gentamicin treated cells. Liposomes prepared from dimyristoyl-phosphatidylcholine (DMPC) mixed with cardiolipin, which mimics the heterogeneous charge composition of the natural cell membrane, were used to determine the effect of gentamicin on artificial bilayers. The membrane lipid packing as revealed by generalized polarization (GP) and fluorescence anizotropy variation with increasing temperature was studied. It was found that the generalized polarization of liposomal membranes containing a negatively charged lipid (cardiolipin) is higher in the presence of gentamicin; in the membrane of living cell (OK), gentamicin induces, on the contrary, a decrease of general polarization. Considering the role of membrane organization in the function of transmembrane channels and receptors, our findings suggest hypotheses that may explain the permeation of gentamicin through the living cell membrane by using these channels.

  2. Ethanol tolerance and membrane fatty acid adaptation in adh multiple and null mutants of Kluyveromyces lactis.

    PubMed

    Heipieper, H J; Isken, S; Saliola, M

    2000-11-01

    The effects of ethanol and 1-octanol on growth and fatty acid composition of different strains of Kluyveromyces lactis containing a mutation in the four different alcohol dehydrogenase (KlADH) genes were investigated. In the presence of ethanol and 1-octanol K. lactis reduced the fluidity of its lipids by decreasing the unsaturation index (UI) of its membrane fatty acids. In this way, a direct correlation between nonlethal ethanol concentrations and the decrease in the UI could be observed. At concentrations which totally inhibited cell growth no reaction occurred. These adaptive modifications of the fatty acid pattern of K. lactis to ethanol contrasted with those reported for Saccharomyces cerevisiae and Schizosaccharomyces pombe. Whereas these two yeasts increased the fluidity of their membrane lipids in the presence of ethanol, K. lactis reduced the fluidity (UI) of its lipids. Among the different isogenic adh negative strains tested, the strain containing no ADH (adh0) and that containing only KlADH1 were the most alcohol-sensitive. The strain with only KlADH2 showed nearly the same tolerance as reference strain CBS 2359/152 containing all four ADH genes. This suggests that the KlADH2 product could play an important role in the adaptation/detoxification reactions of K. lactis to high ethanol concentrations.

  3. A Fluid Membrane-Based Soluble Ligand Display System for Live CellAssays

    SciTech Connect

    Nam, Jwa-Min; Nair, Pradeep N.; Neve, Richard M.; Gray, Joe W.; Groves, Jay T.

    2005-10-14

    Cell communication modulates numerous biological processes including proliferation, apoptosis, motility, invasion and differentiation. Correspondingly, there has been significant interest in the development of surface display strategies for the presentation of signaling molecules to living cells. This effort has primarily focused on naturally surface-bound ligands, such as extracellular matrix components and cell membranes. Soluble ligands (e.g. growth factors and cytokines) play an important role in intercellular communications, and their display in a surface-bound format would be of great utility in the design of array-based live cell assays. Recently, several cell microarray systems that display cDNA, RNAi, or small molecules in a surface array format were proven to be useful in accelerating high-throughput functional genetic studies and screening therapeutic agents. These surface display methods provide a flexible platform for the systematic, combinatorial investigation of genes and small molecules affecting cellular processes and phenotypes of interest. In an analogous sense, it would be an important advance if one could display soluble signaling ligands in a surface assay format that allows for systematic, patterned presentation of soluble ligands to live cells. Such a technique would make it possible to examine cellular phenotypes of interest in a parallel format with soluble signaling ligands as one of the display parameters. Herein we report a ligand-modified fluid supported lipid bilayer (SLB) assay system that can be used to functionally display soluble ligands to cells in situ (Figure 1A). By displaying soluble ligands on a SLB surface, both solution behavior (the ability to become locally enriched by reaction-diffusion processes) and solid behavior (the ability to control the spatial location of the ligands in an open system) could be combined. The method reported herein benefits from the naturally fluid state of the supported membrane, which allows

  4. The effects of oxygen on the evolution of microbial membranes

    NASA Technical Reports Server (NTRS)

    Jahnke, L. L.

    1991-01-01

    One prokaryote, Methylococcus capsulatus, synthesizes both hopanoids and sterols and, thus, provides a unique opportunity to study the evolution of membrane function. When M. capsulatus was grown at different temperatures, lipid analysis of the whole cells showed that both sterol and unsaturated fatty acid levels decreased at higher growth temperatures; sterol concentrations were 0.116 micro mole/micro mole phospholipid at 30 C and 0.025 micro mole/mirco mole phospholipid at 45 C, while the saturated to unsaturated fatty acid ratio increased from 0.397 to 1.475. Hopane polyol levels were constant over this range; however, methylation of the A-ring decreased markedly in cells grown at 30 C. These results imply that sterol and hopane molecules are required for enhancement of some specific membrane function, potentially by modulating membrane fluidity.

  5. Selenium as a modulator of membrane stability parameters and surface changes during the initiation phase of 1,2-dimethylhydrazine induced colorectal carcinogenesis.

    PubMed

    Ghadi, Fereshteh Ezzati; Malhotra, Anshoo; Ghara, Abdollah Ramzani; Dhawan, D K

    2012-10-01

    The present study evaluated the modulatory potential of selenium on colonic surface abnormalities and membrane fluidity changes following 1,2-dimethylhydrazine (DMH) induced colon carcinogenesis. Rats were segregated into four groups viz., normal control, DMH treated, selenium treated, and DMH + selenium treated. Initiation of molecular events leading to colon carcinogenesis was started following weekly subcutaneous injections of DMH (30 mg/Kg body weight) for 10 weeks. Selenium in the form of sodium selenite was supplemented to rats at a dose level of 1 PPM in drinking water, ad libitum for the entire duration of the study. Brush border membranes were isolated from the colon of rats and the viscosity as well as fluidity parameters were assessed using the membrane extrinsic fluorophore pyrene. DMH treatment resulted in a significant increase in lipid peroxidation. Reduced glutathione levels (GSH) and the activities of glutathione reductase (GR), glutathione transferase (GST), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) were found to be significantly decreased following DMH treatment. On the other hand, supplementation with selenium to DMH treated rats resulted in a significant decrease in the levels of lipid peroxidation but caused a significant increase in the levels of GSH as well in the activities of GR, GST, SOD, CAT, and GPx. The results further, demonstrated a marked decrease in membrane microviscosity following DMH treatment. On the other hand, a significant increase was observed in the excimer/monomer ratio and fluidity parameter of DMH treated rats when compared to normal control rats. However, the alterations in membrane microviscosity and the fluidity parameters were significantly restored following selenium treatment. Further, histological as well as colon surface alterations were also observed following DMH treatment, which however were greatly prevented upon selenium co-administration. The study, therefore, concludes

  6. Exogenous γ-aminobutyric acid (GABA) affects pollen tube growth via modulating putative Ca2+-permeable membrane channels and is coupled to negative regulation on glutamate decarboxylase

    PubMed Central

    Yu, Guang-Hui; Zou, Jie; Feng, Jing; Peng, Xiong-Bo; Wu, Ju-You; Wu, Ying-Liang; Palanivelu, Ravishankar; Sun, Meng-Xiang

    2014-01-01

    γ-Aminobutyric acid (GABA) is implicated in pollen tube growth, but the molecular and cellular mechanisms that it mediates are largely unknown. Here, it is shown that exogenous GABA modulates putative Ca2+-permeable channels on the plasma membranes of tobacco pollen grains and pollen tubes. Whole-cell voltage-clamp experiments and non-invasive micromeasurement technology (NMT) revealed that the influx of Ca2+ increases in pollen tubes in response to exogenous GABA. It is also demonstrated that glutamate decarboxylase (GAD), the rate-limiting enzyme of GABA biosynthesis, is involved in feedback controls of Ca2+-permeable channels to fluctuate intracellular GABA levels and thus modulate pollen tube growth. The findings suggest that GAD activity linked with Ca2+-permeable channels relays an extracellular GABA signal and integrates multiple signal pathways to modulate tobacco pollen tube growth. Thus, the data explain how GABA mediates the communication between the style and the growing pollen tubes. PMID:24799560

  7. Exercise affects memory acquisition, anxiety-like symptoms and activity of membrane-bound enzyme in brain of rats fed with different dietary fats: impairments of trans fat.

    PubMed

    Teixeira, A M; Pase, C S; Boufleur, N; Roversi, K; Barcelos, R C S; Benvegnú, D M; Segat, H J; Dias, V T; Reckziegel, P; Trevizol, F; Dolci, G S; Carvalho, N R; Soares, F A A; Rocha, J B T; Emanuelli, T; Bürger, M E

    2011-11-10

    Here we evaluated the influence of physical exercise on behavior parameters and enzymatic status of rats supplemented with different dietary fatty acids (FA). Male Wistar rats fed diets enriched with soybean oil (SO), lard (L), or hydrogenated vegetable fat (HVF) for 48 weeks were submitted to swimming (30 min/d, five times per week) for 90 days. Dietary FA per se did not cause anxiety-like symptoms in the animals, but after physical exercise, SO group showed a better behavioral performance than L and the HVF groups in elevated plus maze (EPM). In Barnes maze, HVF group showed impaired memory acquisition as compared to L group, and exercise reversed this effect. SO-fed rats showed an improvement in memory acquisition after 1 day of training, whereas lard caused an improvement of memory only from day 4. HVF-fed rats showed no improvement of memory acquisition, but this effect was reversed by exercise in all training days. A lower activity of the Na(+)K(+)-ATPase in brain cortex of rats fed lard and HVF was observed, and this effect was maintained after exercise. Similarly, the HVF diet was related to lower activity of hippocampal Na(+)K(+)-ATPase, and exercise reduced activity of this enzyme in the SO and L groups. Our findings show influences of dietary FA on memory acquisition, whereas regular exercise improved this function and was beneficial on anxiety-like symptoms. As FA are present in neuronal membrane phospholipids and play a critical role in brain function, our results suggest that low incorporation of trans FA in neuronal membranes may act on cortical and hippocampal Na(+)K(+)-ATPase activity, but this change appears to be unrelated to the behavioral parameters primarily harmed by consumption of trans and less so by saturated FA, which were reversed by exercise.

  8. Lipid, detergent, and Coomassie Blue G-250 affect the migration of small membrane proteins in blue native gels: mitochondrial carriers migrate as monomers not dimers.

    PubMed

    Crichton, Paul G; Harding, Marilyn; Ruprecht, Jonathan J; Lee, Yang; Kunji, Edmund R S

    2013-07-26

    Blue native gel electrophoresis is a popular method for the determination of the oligomeric state of membrane proteins. Studies using this technique have reported that mitochondrial carriers are dimeric (composed of two ∼32-kDa monomers) and, in some cases, can form physiologically relevant associations with other proteins. Here, we have scrutinized the behavior of the yeast mitochondrial ADP/ATP carrier AAC3 in blue native gels. We find that the apparent mass of AAC3 varies in a detergent- and lipid-dependent manner (from ∼60 to ∼130 kDa) that is not related to changes in the oligomeric state of the protein, but reflects differences in the associated detergent-lipid micelle and Coomassie Blue G-250 used in this technique. Higher oligomeric state species are only observed under less favorable solubilization conditions, consistent with aggregation of the protein. Calibration with an artificial covalent AAC3 dimer indicates that the mass observed for solubilized AAC3 and other mitochondrial carriers corresponds to a monomer. Size exclusion chromatography of purified AAC3 in dodecyl maltoside under blue native gel-like conditions shows that the mass of the monomer is ∼120 kDa, but appears smaller on gels (∼60 kDa) due to the unusually high amount of bound negatively charged dye, which increases the electrophoretic mobility of the protein-detergent-dye micelle complex. Our results show that bound lipid, detergent, and Coomassie stain alter the behavior of mitochondrial carriers on gels, which is likely to be true for other small membrane proteins where the associated lipid-detergent micelle is large when compared with the mass of the protein.

  9. Inhibition of glutamate receptors reduces the homocysteine-induced whole blood platelet aggregation but does not affect superoxide anion generation or platelet membrane fluidization.

    PubMed

    Karolczak, Kamil; Pieniazek, Anna; Watala, Cezary

    2017-01-01

    Homocysteine (Hcy) is an excitotoxic amino acid. It is potentially possible to prevent Hcy-induced toxicity, including haemostatic impairments, by antagonizing glutaminergic receptors. Using impedance aggregometry with arachidonate and collagen as platelet agonists, we tested whether the blockade of platelet NMDA (N-methyl-D-aspartate), AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) and kainate receptors with their inhibitors: MK-801 (dizocilpine hydrogen maleate, [5R,10S]-[+]-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine), CNQX (7-nitro-2,3-dioxo-1,4-dihydroquinoxaline-6-carbonitrile) and UBP-302 (2-{[3-[(2S)-2-amino-2-carboxyethyl]-2,6-dioxo-3,6-dihydropyrimidin 1(2H)-yl]methyl}benzoic acid) may hamper Hcy-dependent platelet aggregation. All the tested compounds significantly inhibited Hcy-augmented aggregation of blood platelets stimulated either with arachidonate or collagen. Hcy stimulated the generation of superoxide anion in whole blood samples in a concentration-dependent manner; however, this process appeared as independent on ionotropic glutamate receptors, as well as on NADPH oxidase and protein kinase C, and was not apparently associated with the extent of either arachidonate- or collagen-dependent platelet aggregation. Moreover, Hcy acted as a significant fluidizer of surface (more hydrophilic) and inner (more hydrophobic) regions of platelet membrane lipid bilayer, when used at the concentration range from 10 to 50 µmol/l. However, this effect was independent on the Hcy action through glutamate ionotropic receptors, since there was no effects of MK-801, CNQX or UBP-302 on Hcy-mediated membrane fluidization. In conclusion, Hcy-induced changes in whole blood platelet aggregation are mediated through the ionotopic excitotoxic receptors, although the detailed mechanisms underlying such interactions remain to be elucidated.

  10. Perfect fluidity of a dissipative system: Analytical solution for the Boltzmann equation in AdS2 Ⓧ S2

    DOE PAGES

    Noronha, Jorge; Denicol, Gabriel S.

    2015-12-30

    In this paper we obtain an analytical solution of the relativistic Boltzmann equation under the relaxation time approximation that describes the out-of-equilibrium dynamics of a radially expanding massless gas. This solution is found by mapping this expanding system in flat spacetime to a static flow in the curved spacetime AdS2 Ⓧ S2. We further derive explicit analytic expressions for the momentum dependence of the single-particle distribution function as well as for the spatial dependence of its moments. We find that this dissipative system has the ability to flow as a perfect fluid even though its entropy density does not matchmore » the equilibrium form. The nonequilibrium contribution to the entropy density is shown to be due to higher-order scalar moments (which possess no hydrodynamical interpretation) of the Boltzmann equation that can remain out of equilibrium but do not couple to the energy-momentum tensor of the system. Furthermore, in this system the slowly moving hydrodynamic degrees of freedom can exhibit true perfect fluidity while being totally decoupled from the fast moving, nonhydrodynamical microscopic degrees of freedom that lead to entropy production.« less

  11. The Extent and Nature of Fluidity in Typologies of Female Sex Work in Southern India: Implications for HIV Prevention Programs.

    PubMed

    Jain, Anrudh K; Saggurti, Niranjan

    2012-04-01

    These authors examine the nature and extent of fluidity in defining the typology of female sex work based on the place of solicitation or place of sex or both places together, and whether sex workers belonging to a particular typology are at increased risk of HIV in southern India. Data are drawn from a cross-sectional survey conducted during 2007-2008 among mobile female sex workers (N = 5301) in four Indian states. Findings from this study address an important policy issue: Should programmatic prevention interventions be spread to cover all places of sex work or be focused on a few places that cover a large majority of sex workers? Results indicate that most female sex workers, including those who are usually hard to reach such as those who are mobile or who use homes for soliciting clients or sex, can be reached programmatically multiple times by concentrating on a smaller number of categories, such as street-, lodge-, and brothel-based sex workers.

  12. Flow and fouling in membrane filters: Effects of membrane morphology

    NASA Astrophysics Data System (ADS)

    Sanaei, Pejman; Cummings, Linda J.

    2015-11-01

    Membrane filters are widely-used in microfiltration applications. Many types of filter membranes are produced commercially, for different filtration applications, but broadly speaking the requirements are to achieve fine control of separation, with low power consumption. The answer to this problem might seem obvious: select the membrane with the largest pore size and void fraction consistent with the separation requirements. However, membrane fouling (an inevitable consequence of successful filtration) is a complicated process, which depends on many parameters other than membrane pore size and void fraction; and which itself greatly affects the filtration process and membrane functionality. In this work we formulate mathematical models that can (i) account for the membrane internal morphology (internal structure, pore size & shape, etc.); (ii) fouling of membranes with specific morphology; and (iii) make some predictions as to what type of membrane morphology might offer optimum filtration performance.

  13. Sublingual delivery of insulin: effects of enhancers on the mucosal lipid fluidity and protein conformation, transport, and in vivo hypoglycemic activity.

    PubMed

    Cui, Chun-Ying; Lu, Wan-Liang; Xiao, Lan; Zhang, Shuang-Qing; Huang, Yan-Bei; Li, Sheng-Lin; Zhang, Rui-Juan; Wang, Gui-Ling; Zhang, Xuan; Zhang, Qiang

    2005-12-01

    The purposes of this study were to evaluate effects of enhancers for sublingual delivering insulin on the mucosal lipid fluidity and protein conformation, transport, and in vivo hypoglycemic activity in normal rats. The effects on sublingual mucosa, and aggregation states of insulin were estimated using fluorescence polarization, and circular dichroism method, respectively. The human immortalized oral epithelial cell monolayer was used for evaluating transport of insulin. Hydroxylpropyl-beta-cyclodextrin (HP-beta-CD), chitosan, polyethylene-polypropylene glycol, polyoxyethylene lauryl ether, polysorbate 80, egg lecithin, or oleic acid, was used as a penetration enhancer, respectively. The fluidity of sublingual mucosal lipid was markedly reduced by these enhancers excluding polysorbate 80, and the secondary structure of the mucosal proteins was also influenced by these enhancers. The hexamers of insulin were dissociated to monomers only by chitosan, polyoxyethylene lauryl ether, and egg lecithin. Nonetheless, plasma glucose levels in normal rats were significantly lowered after sublingual administration of insulin with an enhancer compared with those without an enhancer at the same time-point. The enhancing effects may be due to one or multiple factors: increasing the mucosal lipid fluidity, directly loosing the tight junction of epithelia, and dissociating the hexamers of insulin to monomers. Among these, the opened tight junction may correlate most with the enhancing effect in the mucosal permeability. Because the aggregates of insulin exist, the dissociation of the aggregates by an enhancer would benefit the permeability.

  14. Pathological levels of glucosylceramide change the biophysical properties of artificial and cell membranes.

    PubMed

    Varela, Ana R P; Ventura, Ana E; Carreira, Ana C; Fedorov, Aleksander; Futerman, Anthony H; Prieto, Manuel; Silva, Liana C

    2016-12-21

    Glucosylceramide (GlcCer) plays an active role in the regulation of various cellular events. Moreover, GlcCer is also a key modulator of membrane biophysical properties, which might be linked to the mechanism of its biological action. In order to understand the biophysical implications of GlcCer on membranes of living cells, we first studied the effect of GlcCer on artificial membranes containing 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), sphingomyelin (SM) and cholesterol (Chol). Using an array of biophysical methods, we demonstrate that at lower GlcCer/Chol ratios, GlcCer stabilizes SM/Chol-enriched liquid-ordered domains. However, upon decreasing the Chol content, GlcCer significantly increased membrane order through the formation of gel domains. Changes in pH disturbed the packing properties of GlcCer-containing membranes, leading to an increase in membrane fluidity and reduced membrane electronegativity. To address the biophysical impact of GlcCer in biological membranes, studies were performed in wild type and in fibroblasts treated with conduritol-B-epoxide (CBE), which causes intracellular GlcCer accumulation, and in fibroblasts from patients with type I Gaucher disease (GD). Decreased membrane fluidity was observed in cells containing higher levels of GlcCer, such as in CBE-treated and GD cells. Together, we demonstrate that elevated GlcCer levels change the biophysical properties of cellular membranes, which might compromise membrane-associated cellular events and be of relevance for understanding the pathology of diseases, such as GD, in which GlcCer accumulates at high levels.

  15. Incubation temperature, osmolarity, and salicylate affect the expression of resistance-nodulation-division efflux pumps and outer membrane porins in Acinetobacter baumannii ATCC19606T.

    PubMed

    Bazyleu, Andrei; Kumar, Ayush

    2014-08-01

    In this study, we examined the impact of various environmental conditions on the expression of resistance-nodulation-division (RND) efflux pumps and outer membrane (OM) porins, two key determinants of Acinetobacter baumannii's intrinsic resistance, an organism known to cause various multidrug resistant infections in immunocompromised individuals. Quantitative RT-PCR was used to analyze the expression of adeB, adeG, and adeJ (genes encoding RND pumps) and 33 kDa, carO, and oprD (genes encoding OM porins) of A. baumannii ATCC19606(T) under different incubation temperatures (30, 37, and 42 °C) and in the presence of high osmolarity and salicylate. Downregulation of all three RND pumps was observed at 30 °C, while downregulation of all three porins tested was observed at increased osmolarity. Downregulation of RND efflux pumps, particularly AdeABC, was consistent with increased susceptibility to antibiotics that are substrates of this pump. Expression of the adeR response regulator gene of the AdeRS system, the activator of the AdeABC pump, was also analyzed. Our work shows that various environmental stress conditions can influence the expression of RND pumps and porins in A. baumannii ATCC19606(T) and thus may play a role in the modulation of its antibiotic resistance.

  16. Fluorescence imaging of cholesterol and temperature dependent cell membrane dynamics

    NASA Astrophysics Data System (ADS)

    Weber, Petra; Wagner, Michael; Strauss, Wolfgang S. L.; Schneckenburger, Herbert

    2007-07-01

    Cholesterol content is an important factor for membrane dynamics of living cells. With well defined protocols of depletion and enrichment the impact of cholesterol on membrane dynamics was examined by fluorescence microscopy. In addition, the intracellular cholesterol content was determined with biochemical methods. Changes of cholesterol amounts in cell membranes have previously been related to specific disease and may have some influence on the uptake of pharmaceutical agents. A combination of conventional and total internal reflection fluorescence microscopy was applied to the fluorescence marker laurdan, a polarity-sensitive probe, whose electronic excitation energy is different in polar and non-polar environment. Once incorporated into cell membranes, the fluorescence of laurdan shows a spectral shift towards longer wavelength when its molecules get into contact with adjacent water molecules, e.g. when a phase transition from the tightly packed gel phase to the liquid crystalline phase of membrane lipids occurs. The generalized polarization (GP, characterizing this spectral shift) as well as the fluorescence lifetime (τ) of laurdan revealed to be appropriate measures for membrane stiffness and fluidity. GP generally decreased with increasing temperature and was always higher for the plasma membrane than for intracellular membranes. Enrichment of cholesterol caused a pronounced increase, whereas depletion of cholesterol caused a decrease of GP. In addition, pronounced changes of the fluorescence lifetime pattern occurred in the subnanosecond range. GP, and τ were determined as integral values of single cells or small cell collectives and were also displayed as microscopic images.

  17. Membrane burdens of chlorinated benzenes lower the main phase transition temperature in dipalmitoyl-phosphatidylcholine vesicles: Implications for toxicity by narcotic chemicals

    SciTech Connect

    Wezel, A.P. van; Cornelissen, G.; Miltenburg, J.K. van; Opperhuizen, A.

    1996-02-01

    In the membrane of an organism that dies due to exposure to narcotic chemicals, the main phase transition temperature (T{sub tr}) of the phospholipids is decreased and the fluidity is increased. The decrease in T{sub tr} depends on the molar concentration of narcotics in the membrane (membrane burden) and is irrespective of the physicochemical properties of the chemicals. If membrane-water partition coefficients, exposure concentrations, and the amount of lipid in the system are known, membrane burdens of narcotic chemicals can be calculated and compared to membrane burdens that yield toxicity. The partition coefficients of a series of chlorobenzenes between phospholipid vesicles and water (K{sub mw}) were measured at different temperatures in a new experimental set-up. K{sub mw}`s were higher in the liquid-crystalline phase than in the gel phase. Partitioning into the el phase was entropy driven, partitioning into the liquid-crystalline phase was driven by entropy and enthalpy. The fluidity change in phospholipid vesicles, after accumulation of chlorobenzenes, was measured from the change in T{sub tr}. The membrane burdens of various chlorobenzenes needed for a lowering of T{sub tr} were comparable (e.g., 20--60 mmol/kg for a decrease of 1.0 C). The membrane burden needed in vivo for lethality by narcotic chemicals such as chlorobenzenes was calculated to be 40--160 mmol/kg membrane. By combining the in vivo and in vitro data, it can be concluded that in organisms that die due to exposure to narcotic chemicals, the fluidity of the membrane is increased.

  18. Cooperative binding of Annexin A5 to phosphatidylserine on apoptotic cell membranes

    NASA Astrophysics Data System (ADS)

    Janko, Christina; Jeremic, Ivica; Biermann, Mona; Chaurio, Ricardo; Schorn, Christine; Muñoz, Luis E.; Herrmann, Martin

    2013-12-01

    Healthy cells exhibit an asymmetric plasma membrane with phosphatidylserine (PS) located on the cytoplasmic leaflet of the plasma membrane bilayer. Annexin A5-FITC, a PS binding protein, is commonly used to evaluate apoptosis in flow cytometry. PS exposed by apoptotic cells serves as a major ‘eat-me’ signal for phagocytes. Although exposition of PS has been observed after alternative stimuli, no clearance of viable, PS exposing cells has been detected. Thus, besides PS exposure, membranes of viable and apoptotic cells might exhibit specific characteristics. Here, we show that Annexin A5 binds in a cooperative manner to different types of dead cells. Shrunken apoptotic cells thereby showed the highest Hill coefficient values. Contrarily, parafomaldehyde fixation of apoptotic cells completely abrogates the cooperativity effect seen with dead and dying cells. We tend to speculate that the cooperative binding of Annexin A5 to the membranes of apoptotic cells reflects higher fluidity of the exposed membranes facilitating PS clustering.

  19. Influence of Low-Shear Modeled Microgravity on Heat Resistance, Membrane Fatty Acid Composition, and Heat Stress-Related Gene Expression in Escherichia coli O157:H7 ATCC 35150, ATCC 43889, ATCC 43890, and ATCC 43895

    PubMed Central

    Kim, H. W.

    2016-01-01

    ABSTRACT We previously showed that modeled microgravity conditions alter the physiological characteristics of Escherichia coli O157:H7. To examine how microgravity conditions affect bacterial heat stress responses, D values, membrane fatty acid composition, and heat stress-related gene expression (clpB, dnaK, grpE, groES, htpG, htpX, ibpB, and rpoH), E. coli O157:H7 ATCC 35150, ATCC 43889, ATCC 43890, and ATCC 43895 were cultured under two different conditions: low-shear modeled microgravity (LSMMG, an analog of spaceflight conditions) and normal gravity (NG, Earth-like conditions). When 24-h cultures were heated to 55°C, cells cultured under LSMMG conditions showed reduced survival compared with cells cultured under NG conditions at all time points (P < 0.05). D values of all tested strains were lower after LSMMG culture than after NG culture. Fourteen of 37 fatty acids examined were present in the bacterial membrane: nine saturated fatty acids (SFA) and five unsaturated fatty acids (USFA). The USFA/SFA ratio, a measure of membrane fluidity, was higher under LSMMG conditions than under NG conditions. Compared with control cells grown under NG conditions, cells cultured under LSMMG conditions showed downregulation of eight heat stress-related genes (average, −1.9- to −3.7-fold). The results of this study indicate that in a simulated space environment, heat resistance of E. coli O157:H7 decreased, and this might be due to the synergistic effects of the increases in membrane fluidity and downregulated relevant heat stress genes. IMPORTANCE Microgravity is a major factor that represents the environmental conditions in space. Since infectious diseases are difficult to deal with in a space environment, comprehensive studies on the behavior of pathogenic bacteria under microgravity conditions are warranted. This study reports the changes in heat stress resistance of E. coli O157:H7, the severe foodborne pathogen, under conditions that mimic microgravity. The results

  20. A comparative study of the plasma membrane permeabilization and fluidization induced by antipsychotic drugs in the rat brain.

    PubMed

    Murata, Tetsuhito; Maruoka, Nobuyuki; Omata, Naoto; Takashima, Yasuhiro; Fujibayashi, Yasuhisa; Yonekura, Yoshiharu; Wada, Yuji

    2007-10-01

    We compared the potency of the interaction of three antipsychotic drugs, i.e. chlorpromazine (CPZ), haloperidol (Hal) and sulpiride (Sul), with the plasma membrane in the rat brain. CPZ loading (> or = 100 microM) dose-dependently increased both membrane permeability (assessed as [18F]2-fluoro-2-deoxy-D-glucose-6-phosphate release from brain slices) and membrane fluidity (assessed as the reduction in the plasma membrane anisotropy of 1,6-diphenyl-1,3,5-hexatriene). On the other hand, a higher concentration of Hal (1 mM) was required to observe these effects. However, Sul failed to change membrane permeability and fluidity even at a high concentration (1 mM). These results indicated the following ranking of the potency to interact with the membrane: CPZ>Hal>Sul. The difference among antipsychotic drugs in the potency to interact with the plasma membrane as revealed in the present study may be partly responsible for the difference among the drugs in the probability of inducing extrapyramidal side-effects such as parkinsonism and tardive dyskinesia.

  1. 5-Aminosalicylic acid protection against oxidative damage to synaptosomal membranes by alkoxyl radicals in vitro.

    PubMed

    Kanski, J; Lauderback, C; Butterfield, D A

    2001-01-01

    The antioxidant properties of 5-aminosalicylic acid in vitro were evaluated in a synaptosomal membrane system prepared from gerbil cortical synaptosomes using EPR spin labeling and spectroscopic techniques. MAL-6 (2,2,6,6-tetramethyl-4-maleimidopiperidin-1-oxyl) and 5-NS (5-nitroxide stearate) spin labels were used to assess changes in protein oxidation and membrane lipid fluidity, respectively. Synaptosomal membranes were subjected to oxidative stress by incubation with 1 mM azo-bis(isobutyronitrile) (AIBN) or 1 mM 2,2'-azobis(amidino propane) dihydrochloride (AAPH) at 37 degrees C for 30 minutes. The EPR analyses of the samples showed significant oxidation of synaptosomal proteins and a decrease in membrane fluidity. 5-Aminosalicylic acid also was evaluated by means of FRAP (the ferric reducing ability of plasma) test as a potential antioxidant. 5-Aminosalicylic acid also showed protection against the oxidation in gerbil cortical synaptosomes system caused by AIBN and AAPH. These results are consistent with the notion of antioxidant protection against free radical induced oxidative stress in synaptosomal membrane system by this agent.

  2. Crenarchaeol: the characteristic core glycerol dibiphytanyl glycerol tetraether membrane lipid of cosmopolitan pelagic crenarchaeota.

    PubMed

    Damsté, Jaap S Sinninghe; Schouten, Stefan; Hopmans, Ellen C; van Duin, Adri C T; Geenevasen, Jan A J

    2002-10-01

    The basic structure and stereochemistry of the characteristic glycerol dibiphytanyl glycerol tetraether (GDGT) membrane lipid of cosmopolitan pelagic crenarchaeota has been identified by high field two-dimensional (2D)-NMR techniques. It contains one cyclohexane and four cyclopentane rings formed by internal cyclisation of the biphytanyl chains. Its structure is similar to that of GDGTs biosynthesized by (hyper)thermophilic crenarchaeota apart from the cyclohexane ring. These findings are consistent with the close phylogenetic relationship of (hyper)thermophilic and pelagic crenarchaeota based 16S rRNA. The latter group inherited the biosynthetic capabilities for a membrane composed of cyclopentane ring-containing GDGTs from the (hyper)thermophilic crenarchaeota. However, to cope with the much lower temperature of the ocean, a small but key step in their evolution was the adjustment of the membrane fluidity by making a kink in one of the bicyclic biphytanyl chains by the formation of a cyclohexane ring. This prevents the dense packing characteristic for the cyclopentane ring-containing GDGTs membrane lipids used by hyperthermophilic crenarchaeota to adjust their membrane fluidity to high temperatures.

  3. The membrane interaction of amphiphilic model peptides affects phosphatidylserine headgroup and acyl chain order and dynamics. Application of the phospholipid headgroup electrometer concept to phosphatidylserine

    SciTech Connect

    de Kroon, A.I.P.M.; Killian, J.A.; de Gier, J.; de Kruijff, B. )

    1991-01-29

    Deuterium nuclear magnetic resonance ({sup 2}H NMR) was used to study the interaction of amphiphilic model peptides with model membranes consisting of 1,2-dioleoyl-sn-glycero-3-phospho-L-serine deuterated either at the {beta}-position of the serine moiety ((2-{sup 2}H)DOPS) or at the 11-position of the acyl chains ((11,11-{sup 2}H{sub 2})DOPS). The peptides are derived from the sequences H-Ala-Met-Leu-Trp-Ala-OH and H-Arg-Met-Leu-Trp-Ala-OH and contain a positive charge of +1 or +2 at the amino terminus or one positive charge at each end of the molecule. Upon titration of dispersions of DOPS with the peptides, the divalent peptides show a similar extent of binding to the DOPS bilyers, which is larger than that of the single charged peptide. Under these conditions the values of the quadrupolar splitting of both (2-{sup 2}H)DOPS and (11,11-{sup 2}H{sub 2})DOPS are decreased, indicating that the peptides reduce the order of both the DOPS headgroup and the acyl chains. The extent of the decrease depends on the amount of peptide bound and on the position of the charged moieties in the peptide molecule. Titrations of DOPS with poly(L-lysine){sub 100}, which were included for reasons of comparison, reveal increased {Delta}v{sub q} values. When the peptide-lipid titrations are carried out without applying a freeze-thaw procedure to achieve full equilibration, two-component {sup 2}H NMR spectra occur. The apparently limited accessibility of the lipid to the peptides under these circumstances is discussed in relation to the ability of the peptides to exhibit transbilayer movement. {sup 2}H spin-lattice relaxation time T1 measurements demonstrate a decrease of the rates of motion of both headgroup and acyl chains of DOPS in the presence of the peptides.

  4. Membrane stabilizer

    DOEpatents

    Mingenbach, W.A.

    1988-02-09

    A device is provided for stabilizing a flexible membrane secured within a frame, wherein a plurality of elongated arms are disposed radially from a central hub which penetrates the membrane, said arms imposing alternately against opposite sides of the membrane, thus warping and tensioning the membrane into a condition of improved stability. The membrane may be an opaque or translucent sheet or other material. 10 figs.

  5. Dynamics of sperm subpopulations based on motility and plasma membrane status in thawed ram spermatozoa incubated under conditions that support in vitro capacitation and fertilisation.

    PubMed

    García-Álvarez, Olga; Maroto-Morales, Alejandro; Ramón, Manuel; del Olmo, Enrique; Jiménez-Rabadán, Pilar; Fernández-Santos, M Rocio; Anel-López, Luis; Garde, J Julián; Soler, Ana J

    2014-06-01

    The present study evaluated modifications occurring in thawed ram spermatozoa during incubation in different media that supported in vitro capacitation and fertilisation, and examines how these changes relate to IVF. Thawed sperm samples were incubated under capacitating (Cap) and non-capacitating (non-Cap) conditions for 0, 1 and 2h and used in an IVF test. During incubation, changes related to membrane status and the motility pattern of spermatozoa were assessed, the latter being used to characterise sperm subpopulations. A significantly greater increase (P≤0.05) in the percentage of spermatozoa with higher membrane fluidity was observed in samples incubated with Cap medium from the beginning of incubation. In addition, changes over time in the distribution of the motile subpopulation were particularly evident when spermatozoa were incubated with Cap medium, with a noted increase in spermatozoa classified as 'hyperactivated like', with major changes occurring after 1h incubation. Both characteristics (i.e. membrane fluidity and the percentage of the hyperactivated-like subpopulation) were significantly related with in vitro fertility, and only sperm samples incubated with the Cap medium were capable of fertilising oocytes. These results support the idea that changes in sperm membrane fluidity and motility pattern (i.e. an increase in hyperactivated spermatozoa) are needed for fertilisation to take place.

  6. Effect of membrane tension on the physical properties of DOPC lipid bilayer membrane

    PubMed Central

    Reddy, A. Srinivas; Warshaviak, Dora Toledo; Chachisvilis, Mirianas

    2013-01-01

    Molecular dynamics simulations of a dioleoylphosphocholine (DOPC) lipid bilayer were performed to explore its mechanosensitivity. Variations in the bilayer properties, such as area per lipid, volume, thickness, hydration depth (HD), hydration thickness (HT), lateral diffusion coefficient, and changes in lipid structural order were computed in the membrane tension range 0 to 15 dyn/cm. We determined that an increase in membrane tension results in a decrease in the bilayer thickness and HD of ∼5% and ∼5.7% respectively, whereas area per lipid, volume, and HT/HD increased by 6.8%, 2.4%, and 5% respectively. The changes in lipid conformation and orientation were characterized using orientational (S2) and deuterium (SCD) order parameters. Upon increase of membrane tension both order parameters indicated an increase in lipid disorder by 10– 20%, mostly in the tail end region of the hydrophobic chains. The effect of membrane tension on lipid lateral diffusion in the DOPC bilayer was analyzed on three different time scales corresponding to inertial motion, anomalous diffusion and normal diffusion. The results showed that lateral diffusion of lipid molecules is anomalous in nature due to the non-exponential distribution of waiting times. The anomalous and normal diffusion coefficients increased by 20% and 52% when the membrane tension changed from 0 to 15 dyn/cm, respectively. In conclusion, our studies showed that membrane tension causes relatively significant changes in the area per lipid, volume, polarity, membrane thickness, and fluidity of the membrane suggesting multiple mechanisms by which mechanical perturbation of the membrane could trigger mechanosensitive response in cells. PMID:22588133

  7. Theoretical and simulation study of lipid membranes

    NASA Astrophysics Data System (ADS)

    Khelashvili, George

    It has been established that a proper functioning of biological lipid membranes is in large part due to cholesterol's ability to regulate fluidity of a lipid bilayer. In particular, a growing body of evidence suggested that cholesterol participates in the formation of cholesterol- and sphingolipid-enriched phase-separated domains known as "rafts" in the plasma and other membranes of animal cells. Rafts have been identified as important membrane structural components in signal transduction, protein transport and sorting of membrane components. At a molecular level, the detailed, localized behavior of lipid-cholesterol bilayers is unclear. In order to better understand how cholesterols function in lipid membranes it is desirable to built theoretical models. The goal of the present research is to model lipid-cholesterol bilayers on the different length and timescales. In the first part of the work, mixtures of sphingomyelin (SM) lipid and cholesterol at different temperatures and cholesterol concentrations were investigated using Molecular Dynamics and Monte-Carlo simulation techniques. The objective was to study the properties of cholesterol- and SM-enriched raft-like domains at the atomic level. The simulations revealed that, addition of 31% cholesterol induced intermediate degree of organization in the model SM-cholesterol bilayers at temperatures below and above the main phase transition temperature of pure SM bilayer. This intermediate state of fluidity may be necessary for the binding of proteins and other molecules that associate with raft domains. In the second part of the work, dynamical self-consistent mean-field model based on atomistic simulations was developed to investigate phase properties of lipid-cholesterol bilayers on the length and timescales currently unreachable with traditional atomistic level simulation methods. This new technique allows studying systems consisting of 104 or more number of molecules, on microsecond timescales. The model was

  8. Fluorescent Probe Study of AOT Vesicle Membranes and Their Alteration upon Addition of Aniline or the Aniline Dimer p-Aminodiphenylamine (PADPA).

    PubMed

    Iwasaki, Fumihiko; Luginbühl, Sandra; Suga, Keishi; Walde, Peter; Umakoshi, Hiroshi

    2017-02-28

    Artificial vesicles formed from sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in aqueous solution are used successfully as additives for enzymatic oligomerizations or polymerizations of aniline or the aniline dimer p-aminodiphenylamine (PADPA) under slightly acidic conditions (e.g., pH 4.3 with horseradish peroxidase and hydrogen peroxide as oxidants). In these systems, the reactions occur membrane surface-confined. Therefore, (i) the physicochemical properties of the vesicle membrane and (ii) the interaction of aniline or PADPA with the AOT membrane play crucial roles in the progress and final outcome of the reactions. For this reason, the properties of AOT vesicles with and without added aniline or PADPA were investigated by using two fluorescent membrane probes: 1,6-diphenyl-1,3,5-hexatriene (DPH) and 6-lauroyl-2-dimethylaminonaphthalene (Laurdan). DPH and Laurdan were used as "sensors" of the membrane fluidity, surface polarity, and membrane phase state. Moreover, the effect of hexanol, alone or in combination with aniline or PADPA, as a possible modifier of the AOT membrane, was also studied with the aim of evaluating whether the membrane fluidity and surface polarity is altered significantly by hexanol, which, in turn, may have an influence on the mentioned types of reactions. The data obtained indicate that the AOT vesicle membrane at room temperature and pH 4.3 (0.1 M NaH2PO4) is more fluid and has a more polar surface than in the case of fluid phospholipid vesicle membranes formed from 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). Furthermore, the fluorescence measurements indicate that mixed AOT-hexanol membranes are less fluid than pure AOT membranes and that they have a lower surface polarity than pure AOT membranes. PADPA strongly binds to AOT and to mixed AOT/hexanol membranes and leads to drastic changes in the membrane properties (decrease in fluidity and surface polarity), resulting in Laurdan fluorescence spectra, which are characteristic for

  9. Biological Fuel Cells and Membranes.

    PubMed

    Ghassemi, Zahra; Slaughter, Gymama

    2017-01-17

    Biofuel cells have been widely used to generate bioelectricity. Early biofuel cells employ a semi-permeable membrane to separate the anodic and cathodic compartments. The impact of different membrane materials and compositions has also been explored. Some membrane materials are employed strictly as membrane separators, while some have gained significant attention in the immobilization of enzymes or microorganisms within or behind the membrane at the electrode surface. The membrane material affects the transfer rate of the chemical species (e.g., fuel, oxygen molecules, and products) involved in the chemical reaction, which in turn has an impact on the performance of the biofuel cell. For enzymatic biofuel cells, Nafion, modified Nafion, and chitosan membranes have been used widely and continue to hold great promise in the long-term stability of enzymes and microorganisms encapsulated within them. This article provides a review of the most widely used membrane materials in the development of enzymatic and microbial biofuel cells.

  10. Biological Fuel Cells and Membranes

    PubMed Central

    Ghassemi, Zahra; Slaughter, Gymama

    2017-01-01

    Biofuel cells have been widely used to generate bioelectricity. Early biofuel cells employ a semi-permeable membrane to separate the anodic and cathodic compartments. The impact of different membrane materials and compositions has also been explored. Some membrane materials are employed strictly as membrane separators, while some have gained significant attention in the immobilization of enzymes or microorganisms within or behind the membrane at the electrode surface. The membrane material affects the transfer rate of the chemical species (e.g., fuel, oxygen molecules, and products) involved in the chemical reaction, which in turn has an impact on the performance of the biofuel cell. For enzymatic biofuel cells, Nafion, modified Nafion, and chitosan membranes have been used widely and continue to hold great promise in the long-term stability of enzymes and microorganisms encapsulated within them. This article provides a review of the most widely used membrane materials in the development of enzymatic and microbial biofuel cells. PMID:28106711

  11. Membrane topology of transmembrane proteins: determinants and experimental tools.

    PubMed

    Lee, Hunsang; Kim, Hyun

    2014-10-17

    Membrane topology refers to the two-dimensional structural information of a membrane protein that indicates the number of transmembrane (TM) segments and the orientation of soluble domains relative to the plane of the membrane. Since membrane proteins are co-translationally translocated across and inserted into the membrane, the TM segments orient themselves properly in an early stage of membrane protein biogenesis. Each membrane protein must contain some topogenic signals, but the translocation components and the membrane environment also influence the membrane topology of proteins. We discuss the factors that affect membrane protein orientation and have listed available experimental tools that can be used in determining membrane protein topology.

  12. Seminal plasma affects sperm sex sorting in boars.

    PubMed

    Alkmin, Diego V; Parrilla, Inmaculada; Tarantini, Tatiana; Del Olmo, David; Vazquez, Juan M; Martinez, Emilio A; Roca, Jordi

    2016-04-01

    Two experiments were conducted in boar semen samples to evaluate how both holding time (24h) and the presence of seminal plasma (SP) before sorting affect sperm sortability and the ability of sex-sorted spermatozoa to tolerate liquid storage. Whole ejaculate samples were divided into three aliquots immediately after collection: one was diluted (1:1, v/v) in Beltsville thawing solution (BTS; 50% SP); the SP of the other two aliquots was removed and the sperm pellets were diluted with BTS + 10% of their own SP (10% SP) or BTS alone (0% SP). The three aliquots of each ejaculate were divided into two portions, one that was processed immediately for sorting and a second that was sorted after 24h storage at 15-17°C. In the first experiment, the ability to exhibit well-defined X- and Y-chromosome-bearing sperm peaks (split) in the cytometry histogram and the subsequent sorting efficiency were assessed (20 ejaculates). In contrast with holding time, the SP proportion influenced the parameters examined, as evidenced by the higher number of ejaculates exhibiting split and better sorting efficiency (P<0.05) in semen samples with 0-10% SP compared with those with 50% SP. In a second experiment, the quality (viability, total and progressive motility) and functionality (plasma membrane fluidity and intracellular generation of reactive oxygen species) of sex-sorted spermatozoa were evaluated after 0, 72 and 120h storage at 15-17°C (10 ejaculates). Holding time and SP proportion did not influence the quality or functionality of stored sex-sorted spermatozoa. In conclusion, a holding time as long as 24h before sorting did not negatively affect sex sorting efficiency or the ability of sorted boar spermatozoa to tolerate long-term liquid storage. A high proportion of SP (50%) in the semen samples before sorting reduced the number of ejaculates to be sorted and negatively influenced the sorting efficiency, but did not affect the ability of sex-sorted spermatozoa to tolerate liquid

  13. ATP-induced lipid membrane reordering in the myelinated nerve fiber identified using Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Kutuzov, N. P.; Brazhe, A. R.; Yusipovich, A. I.; Maksimov, G. V.; Dracheva, O. E.; Lyaskovskiy, V. L.; Bulygin, F. V.; Rubin, A. B.

    2013-07-01

    We demonstrate a successful application of Raman spectroscopy to the problem of lipid ordering with microscopic resolution in different regions of the myelinated nerve fiber. Simultaneous collection of Raman spectra of lipids and carotenoids has enabled us to characterize membrane fluidity and the degree of lipid ordering based on intensity ratios for the 1527/1160 and 2940/2885 cm-1 bands. We show that the intensity profiles of the major Raman bands vary significantly between the three major regions of myelinated nerve fiber: internode, paranode and the node of Ranvier. Mapping Raman peak intensities over these areas suggested that the carotenoid molecules are localized in the myelin membranes of nerve cells. Paranodal membranes were sensitive to extracellular ATP. ATP solutions (7 mM) influenced the 1527/1160 and 2940/2885 cm-1 intensity ratios. Changes in both carotenoid and lipid Raman spectra were in accord and indicated an increase in lipid ordering degree and decrease in membrane fluidity under ATP administration. The collected data provide evidence for the existence of a regulatory purinergic signaling pathway in the peripheral nervous system.

  14. MODEL AND CELL MEMBRANE PARTITIONING OF PERFLUOROOCTANESULFONATE IS INDEPENDENT OF THE LIPID CHAIN LENGTH

    PubMed Central

    Xie, Wei; Ludewig, Gabriele; Wang, Kai; Lehmler, Hans-Joachim

    2009-01-01

    Perfluorooctanesulfonic acid (PFOS) is a persistent environmental pollutant that may cause adverse health effects in humans and animals by interacting with and disturbing of the normal properties of biological lipid assemblies. To gain further insights into these interactions, we investigated the effect of PFOS potassium salt on dimyristoyl- (DMPC), dipalmitoyl- (DPPC) and distearoylphosphatidylcholine (DSPC) model membranes using fluorescence anisotropy measurements and differential scanning calorimetry (DSC) and on the cell membrane of HL-60 human leukemia cells and freshly isolated rat alveolar macrophages using fluorescence anisotropy measurements. PFOS caused a concentration-dependent decrease of the main phase transition temperature (Tm) and an increased peak width (ΔTw) in both the fluorescence anisotropy and the DSC experiments, with a rank order DMPC > DPPC > DSPC. PFOS caused a fluidization of the gel phase of all phosphatidylcholines investigated, but had the opposite effect on the liquid crystalline phase. The apparent partition coefficients of PFOS between the phosphatidylcholine bilayer and the bulk aqueous phase were largely independent of the phosphatidylcholine chain length and ranged from 4.4 × 104 to 8.8 × 104. PFOS also significantly increased the fluidity of membranes of cells. These findings suggest that PFOS readily partitions into lipid assemblies, independent of their composition, and may cause adverse biological effects by altering their fluidity in a manner that depends on the membrane cooperativity and state (e.g., gel versus liquid crystalline phase) of the lipid assembly. PMID:19932010

  15. Resolving single membrane fusion events on planar pore-spanning membranes

    PubMed Central

    Schwenen, Lando L. G.; Hubrich, Raphael; Milovanovic, Dragomir; Geil, Burkhard; Yang, Jian; Kros, Alexander; Jahn, Reinhard; Steinem, Claudia

    2015-01-01

    Even though a number of different in vitro fusion assays have been developed to analyze protein mediated fusion, they still only partially capture the essential features of the in vivo situation. Here we established an in vitro fusion assay that mimics the fluidity and planar geometry of the cellular plasma membrane to be able to monitor fusion of single protein-containing vesicles. As a proof of concept, planar pore-spanning membranes harboring SNARE-proteins were generated on highly ordered functionalized 1.2 μm-sized pore arrays in Si3N4. Full mobility of the membrane components was demonstrated by fluorescence correlation spectroscopy. Fusion was analyzed by two color confocal laser scanning fluorescence microscopy in a time resolved manner allowing to readily distinguish between vesicle docking, intermediate states such as hemifusion and full fusion. The importance of the membrane geometry on the fusion process was highlighted by comparing SNARE-mediated fusion with that of a minimal SNARE fusion mimetic. PMID:26165860

  16. Cellular Lipid Composition Affects Sensitivity of Plant Pathogens to Fengycin, an Antifungal Compound Produced by Bacillus subtilis Strain CU12.

    PubMed

    Wise, Cody; Falardeau, Justin; Hagberg, Ingrid; Avis, Tyler J

    2014-10-01

    Fengycin is an antimicrobial cyclic lipopeptide produced by various Bacillus subtilis strains, including strain CU12. Direct effects of fengycin include membrane pore formation and efflux of cellular contents leading to cell death in sensitive microorganisms. In this study, four plant pathogens were studied in order to elucidate the role of membrane lipids in their relative sensitivity to fengycin. Inhibition of mycelial growth in these pathogens varied considerably. Analysis of membrane lipids in these microorganisms indicated that sensitivity correlated with low ergosterol content and shorter phospholipid fatty acyl chains. Sensitivity to fengycin also correlated with a lower anionic/zwitterionic phospholipid ratio. Our data suggest that decreased fluidity buffering capacity, as a result of low ergosterol content, and higher intrinsic fluidity afforded by short fatty acyl chain length may increase the sensitivity of microbial membranes to fengycin. Our results also suggest that lower content in anionic phospholipids may increase fengycin insertion into the membrane through reduced electrostatic repulsion with the negatively charged fengycin. The intrinsic membrane lipid composition may contribute, in part, to the observed level of antimicrobial activity of fengycin in various plant pathogens.

  17. Cytotoxicity of sulfurous acid on cell membrane and bioactivity of Nitrosomonas europaea.

    PubMed

    Jiang, Ruiyu; Wang, Mingqing; Xue, Jianliang; Xu, Ning; Hou, Guihua; Zhang, Wubing

    2015-01-01

    Nitrosomonas europaea, an ammonia oxidizing bacterium, was chosen as a research model to study the alteration of cell membrane in the presence of sulfurous acid and biodegradation of acetochlor. Significant changes of the outer cell membrane were observed in the presence of sulfurous acid using scanning electron microscopy (SEM) and Atomic Force Microscopy (AFM). The fluorescence polarization has shown a significant decrease in membrane fluidity and the increase of permeability of cell membrane. Lysozyme experiment show the cell becomes easily influenced by substance in medium. Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) measurements show considerable amount of Ca(2+) and Mg(2+) in the supernatant from the sulfurous acid exposed cells. Sulfurous acid treatment enhanced the ability of N. europaea to degrade acetochlor. On this basis, it can be concluded that the increased cell permeability is favor for the absorbability of nutrition. As a result, N. europaea grows faster and the biodegradation efficiency was improved.

  18. The effect of phosphatidylcholine to sphingomyelin mole ratio on the dynamic properties of sheep erythrocyte membrane.

    PubMed

    Borochov, H; Zahler, P; Wilbrandt, W; Shinitzky, M

    1977-11-01

    Sheep red blood cells are shown to incorporate phosphatidylchline when incubated in human plasma in the presence of EGTA. This treatment results in up to a 5-fold increase in mol ratio of phosphatidylcholine to sphingomyelin. By replacing EGTA with Ca+ the increase of phsphatidylcholine content is completely inhibited, due to the activation of the membrane bound lecithinase which rapidly degrades the incorporated phosphatidylcholine. Analogous treatments of the isolate membranes resulted in similar phosphatidylcholine incorporation but in the presence of Ca+ a residual phosphatidylcholine uptake was still oberved. These results suggest that in the isolated membranes small amounts of phosphatidylcholine can be incorporated into an additional region which is unavailable for the membrane lecithinase. The increase in the phosphatidylcholine to sphingomyelin mol ratio in sheep red blood cells is concomitant with an increase in lipid fluidity, as well as increase in osmotic fragility9

  19. Studying lipid organization in biological membranes using liposomes and EPR spin labeling

    PubMed Central

    Subczynski, Witold K.; Raguz, Marija; Widomska, Justyna

    2015-01-01

    Summary Electron paramagnetic resonance (EPR) spin-labeling methods provide a unique opportunity to determine the lateral organization of lipid bilayer membranes by discrimination of coexisting membrane domains or coexisting membrane phases. In some cases, the coexisting membrane domains can be characterized by profiles of alkyl chain order, fluidity, hydrophobicity, and oxygen diffusion-concentration product in situ, without the need for their physical separation. This chapter briefly explains how the EPR spin-labeling methods can be used to obtain the above mentioned profiles across the lipid bilayer membranes (liposomes) derived from the lipid extract of certain biological membranes. These procedures will be illustrated by EPR measurements performed for multilamellar liposomes made of the lipid extracts from cortical and nuclear fractions of the fiber cell plasma membranes of a cow eye lens. To elucidate better the major factors that determine membrane properties, the results for eye lens lipid membranes will be compared with those obtained for simple model membranes resembling basic lipid composition of biological membranes. PMID:20013402

  20. A dual antibacterial mechanism involved in membrane disruption and DNA binding of 2R,3R-dihydromyricetin from pine needles of Cedrus deodara against Staphylococcus aureus.

    PubMed

    Wu, Yanping; Bai, Jinrong; Zhong, Kai; Huang, Yina; Gao, Hong

    2017-03-01

    The antibacterial activity and mechanism of 2R,3R-dihydromyricetin (DMY) against Staphylococcus aureus were investigated. The minimum inhibitory concentration of DMY against S. aureus was 0.125mg/ml, and the growth inhibitory assay also revealed that DMY showed a potent antibacterial activity against S. aureus. Massive nucleotide leakage and flow cytometric analysis demonstrated that DMY disrupted the membrane integrity of S. aureus. Morphological changes and membrane hyperpolarization of S. aureus cells treated with DMY further suggested that DMY destroyed cell membrane. Meanwhile, DMY probably interacted with membrane lipids and proteins, causing a significant reduction in membrane fluidity and changes in conformation of membrane protein. Moreover, DMY could interact with S. aureus DNA through the groove binding mode. Overall, the results suggested that DMY could be applied as a candidate for the development of new food preservatives as it achieved bactericidal activity by damaging cell membrane and binding to intracellular DNA.

  1. Interactions of some local anesthetics and alcohols with membranes.

    PubMed

    Frangopol, P T.; Mihăilescu, D

    2001-09-01

    A review of the results obtained by our group in the last decade regarding the interactions of procaine, lidocaine, dibucaine and tetracaine with membranes is presented in the context of the literature data. The action upon membranes, in first approximation monomolecular film of stearic acid spread at the air/water interface used as a membrane model, the modification of biomembrane structure and function using diffraction methods, lipid phase transition, fluidity of lipids and proteins, membrane expansion and platelet aggregation were studied. The thermodynamic knowledge of membrane-alcohol interactions improved by using highly sensitive calorimetric techniques are briefly reported. One of the main conclusions is that the physical state of a monolayer model membrane was the result of competitive interactions between film-film and film-substrate interactions. It was taken into account that local anesthetics, such as lidocaine, carbisocaine, mesocaine, showed changes in the bilayer structure, reflected in macroscopic mechanical properties. This restructuring of the lipid bilayer has a significant influence on the operation of functional subunits, e.g. ionic channels formed by gramicidin. The results support the concept of non-specific interactions of local anesthetics with lipid bilayers. The theoretical modeling of the interactions of local anesthetics is closely compared with experimental data. Our new theory of relaxation for these interactions is using a non-archimedean formalism based on a process resulting from superpositions of different component processes which take place at different scales of time.

  2. Influence of acetic, citric, and lactic acids on Escherichia coli O157:H7 membrane lipid composition, verotoxin secretion, and acid resistance in simulated gastric fluid.

    PubMed

    Yuk, Hyun-Gyun; Marshall, Douglas L

    2005-04-01

    The effect of organic acid (acetic, citric, and lactic acids) adaptation at equivalent initial pH values (6.4 and 5.4) on changes in membrane lipid composition, verotoxin concentration, and acid resistance in simulated gastric fluid (pH 1.5, 37 degrees C) was determined for Escherichia coli O157:H7 ATCC 43895 (HEC) and an rpoS mutant of E. coli O157:H7 ATCC 43895 (RM, FRIK 816-3). For HEC, lactic acid-adapted (pH 5.4) cells had the greatest D-value (32.2 min) and acetic acid-adapted (pH 5.4) cells had the smallest D-value (16.6 min) in simulated gastric fluid. For RM, D-values of citric and acetic acid-adapted cells were similar to those for nonadapted cells grown at pH 7.3, but D-values increased from 13.1 to 27.9 min in lactic acid-adapted cells (from pH 7.3 to pH 5.4). For both strains, the ratio of cis-vaccenic to palmitic acids decreased for citric and lactic acid-adapted cells, but the ratio increased for acetic acid-adapted cells at pH 5.4. Organic acid-adapted cells produced less total verotoxin than did nonadapted cells at approximately 10(8) CFU/ml. Extracellular verotoxin concentration proportionally decreased with decreasing pH for both HEC and RM. Changes in membrane lipid composition, verotoxin concentration, and acid resistance in HEC and RM were dependent on both pH and organic acid. Deletion of the rpoS gene did not affect these changes but did decrease acid resistance in citric acid-adapted cells. Results indicate that decreased membrane fluidity may have caused increased acid resistance and decreased verotoxin secretion.

  3. Nanopore-spanning lipid bilayers on silicon nitride membranes that seal and selectively transport ions.

    PubMed

    Korman, Christopher E; Megens, Mischa; Ajo-Franklin, Caroline M; Horsley, David A

    2013-04-09

    We report the formation of POPC lipid bilayers that span 130 nm pores in a freestanding silicon nitride film supported on a silicon substrate. These solvent-free lipid membranes self-assemble on organosilane-treated Si3N4 via the fusion of 200 nm unilamellar vesicles. Membrane fluidity is verified by fluorescence recovery after photobleaching (FRAP), and membrane resistance in excess of 1 GΩ is demonstrated using electrical impedance spectroscopy (EIS). An array of 40,000 membranes maintained high impedance over 72 h, followed by rupture of most of the membranes by 82 h. Membrane incorporation of gramicidin, a model ion channel, resulted in increased membrane conductance. This membrane conductance was diminished when the gramicidin channels were blocked with CaCl2, indicating that the change in membrane conductance results from gramicidin-mediated ion transport. These very stable, biologically functional pore-spanning membranes open many possibilities for silicon-based ion-channel devices for applications such as biosensors and high-throughput drug screening.

  4. Molecular rheology of neuronal membranes explored using a molecular rotor: Implications for receptor function.

    PubMed

    Pal, Sreetama; Chakraborty, Hirak; Bandari, Suman; Yahioglu, Gokhan; Suhling, Klaus; Chattopadhyay, Amitabha

    2016-03-01

    The role of membrane cholesterol as a crucial regulator in the structure and function of membrane proteins and receptors is well documented. However, there is a lack of consensus on the mechanism for such regulation. We have previously shown that the function of an important neuronal receptor, the serotonin1A receptor, is modulated by cholesterol in hippocampal membranes. With an overall objective of addressing the role of membrane physical properties in receptor function, we measured the viscosity of hippocampal membranes of varying cholesterol content using a meso-substituted fluorophore (BODIPY-C12) based on the BODIPY probe. BODIPY-C12 acts as a fluorescent molecular rotor and allows measurement of hippocampal membrane viscosity through its characteristic viscosity-sensitive fluorescence depolarization. A striking feature of our results is that specific agonist binding by the serotonin1A receptor exhibits close correlation with hippocampal membrane viscosity, implying the importance of global membrane properties in receptor function. We envision that our results are important in understanding GPCR regulation by the membrane environment, and is relevant in the context of diseases in which GPCR signaling plays a major role and are characterized by altered membrane fluidity.

  5. Thermodynamics and dynamics of phosphatidylcholine-cholesterol mixed model membranes in the liquid crystalline state: effects of water.

    PubMed Central

    Shin, Y K; Budil, D E; Freed, J H

    1993-01-01

    of S(chol) on the composition. In particular, the amount of water affects the membrane fluidity, monitored by R perpendicular for CSL, solely by the structural changes it induces in the membrane for the compositions studied. Rotational diffusion for the labeled PC is found to be more complex, most likely due to the combined action of the internal modes of motion of the flexible chain and of the overall molecular reorientation. PMID:8241408

  6. Multicomponent membranes

    DOEpatents

    Kulprathipanja, Santi; Kulkarni, Sudhir S.; Funk, Edward W.

    1988-01-01

    A multicomponent membrane which may be used for separating various components which are present in a fluid feed mixture comprises a mixture of a plasticizer such as a glycol and an organic polymer cast upon a porous organic polymer support. The membrane may be prepared by casting an emulsion or a solution of the plasticizer and polymer on the porous support, evaporating the solvent and recovering the membrane after curing.

  7. Adenosine deaminase in cell transformation. Biophysical manifestation of membrane dynamics.

    PubMed

    Porat, N; Gill, D; Parola, A H

    1988-10-15

    Cell transformation is associated with a dramatic collapse of a graphic fingerprint characteristic of normal cells, as measured by phase fluorimetry. This is demonstrated on adenosine deaminase (ADA, EC 3.5.4.4), an established malignancy marker. ADA activity is known to decrease markedly in chick embryo fibroblasts (CEF) transformed by Rous sarcoma virus. The high affinity between the catalytic small subunit ADA (SS-ADA) and its membranal complexing protein (ADCP) (which abounds on the plasma membrane of CEF) allowed the hybridization of fluorescent labeled SS-ADA with native ADCP on CEF. Multifrequency differential phase fluorimetry responded remarkably to the state of this hybrid membrane protein. The transformation process is shown to have led to increased membrane fluidity and rotational mobility of ADCP as well as to its reduced availability to SS-ADA binding. The hypothesis of protein vertical sinking into the lipid core of the membrane is now given support by our spectroscopic data. Additional models are considered. A regulatory role is thus suggested for the complexing protein, which may also account for (a) reduced ADA activity in transformed cells and (b) detachment, exclusive to normal cells, upon addition of SS-ADA in excess.

  8. Integrated oxidation membrane filtration process - NOM rejection and membrane fouling.

    PubMed

    Winter, J; Uhl, W; Bérubé, P R

    2016-11-01

    The extent and mechanisms by which organic matter in a solution can be retained and foul a membrane largely depends on the molecular weight of the material being filtered and the molecular weight cut-off (MWCO) of the membrane. The present study investigated the effect of the MWCO of a membrane and the molecular weight distribution of natural organic matter (NOM) in a source water on the increase in resistance to the permeate flux over time. Of particular interest was the effect of oxidation, applied prior to membrane filtration, on the predominant fouling mechanism. Oxidation can change the molecular weight distribution of organic matter in raw water, and therefore the ability of a membrane to retain this organic matter. Oxidation, using both ozonation and UV/H2O2, could effectively reduce the extent of fouling for higher MWCO membranes. However, neither oxidation approaches could effectively reduce the extent of fouling for lower MWCO membranes, likely because oxidation could not effectively oxidize lower molecular weight organic matter. Althoug the data indicated that the extent of fouling is increasing with the amount of DOC retained by the membrane, no statistically significant correlation was observed between these parameters. The results suggest that oxidation did not affect the predominant fouling mechanism. However, it did affect the molecular weight distribution of the organic matter retained by the membranes, and as a result, the resistance offered by the foulant cake layer.

  9. Mechanosensing using drag force for imaging soft biological membranes.

    PubMed

    Zarnitsyn, Vladimir G; Fedorov, Andrei G

    2007-05-22

    We investigate physical processes taking place during nanoscale mechanosensing of soft biological membranes in liquid environments. Examples include tapping mode imaging by atomic force microscope (AFM) and microscopy based on the Brownian motion of a nanoparticle in an optical-tweezers-controlled trap. The softness and fluidity of the cellular membrane make it difficult to accurately detect (i.e., image) the shape of the cell using traditional mechanosensing methods. The aim of the reported work is to theoretically evaluate whether the drag force acting on the nanoscale mechanical probe due to a combined effect of intra- and extracellular environments can be exploited to develop a new imaging mode suitable for soft cellular interfaces. We approach this problem by rigorous modeling of the fluid mechanics of a complex viscoelastic biosystem in which the probe sensing process is intimately coupled to the membrane biomechanics. The effects of the probe dimensions and elastic properties of the membrane as well as intra- and extracellular viscosities are investigated in detail to establish the structure and evolution of the fluid field as well as the dynamics of membrane deformation. The results of numerical simulations, supported by predictions of the scaling analysis of forces acting on the probe, suggest that viscous drag is the dominant force dictating the probe dynamics as it approaches a biological interface. The increase in the drag force is shown to be measurable, to scale linearly with an increase in the viscosity ratio of the fluids on either side of the membrane, and to be inversely proportional to the probe-to-membrane distance. This leads to the postulation of a new strategy for lipid membrane imaging by AFM or other mechanosensing methods using a variation in the maximum drag force as an indicator of the membrane position.

  10. Lateral organization of membranes and cell shapes.

    PubMed Central

    Markin, V S

    1981-01-01

    The relations among membrane structure, mechanical properties, and cell shape have been investigated. The fluid mosaic membrane models used contains several components that move freely in the membrane plane. These components interact with each other and determine properties of the membrane such as curvature and elasticity. A free energy equation is postulated for such a multicomponent membrane and the condition of free energy minimum is used to obtain differential equations relating the distribution of membrane components and the local membrane curvature. The force that moves membrane components along the membrane in a variable curvature field is calculated. A change in the intramembrane interactions can bring about phase separation or particle clustering. This, in turn, may strongly affect the local curvature. The numerical solution of the set of equations for the two dimensional case allows determination of the cell shape and the component distribution along the membrane. The model has been applied to describe certain erythrocytes shape transformations. PMID:7284547

  11. Combined effects of magnetic fields and temperature changes on 1-aminonaphthalene-8-sulfonic acid fluorescence in red blood cell ghost cell membrane

    NASA Astrophysics Data System (ADS)

    Iwasaka, M.; Yaoita, M.; Iwasawa, T.; Ueno, S.

    2006-04-01

    In the present study, we performed an experiment to clarify the possible effects of magnetic fields of up to 8 T on cell membrane fluidity by using red blood cell ghosts and a fluorescence dye, 1-aminonaphthalene-8-sulfonic acid (ANS). The time course of ANS emission at 480 nm under the influence of a magnetic field at 5 T was observed. The effects of multiple rapid temperature changes and magnetic fields were investigated. The emission intensity at 480 nm increased when the temperature of the cell holder was increased from 20 to 38-46 °C for 15 min. A change in temperature exhibited an increase in the fluidity of the lipid molecules in the cell membrane and increased the population of ANS molecules emitting light at 480 nm in the cell membrane, which is hydrophobic. A discontinuous change in fluorescence at 38-40 °C was exhibited under exposure to a magnetic field at 5 T, while the temperature dependency was continuous without exposure to the magnetic field. In addition, under exposure to the magnetic field, the fluorescence during a decrease in temperature from 38 to 20 °C remained at a level close to the fluorescence during an increase in temperature. The results indicated that the fluidity of the molecules in the cell membrane was decelerated by exposure to magnetic fields at 5 T. We speculated that the magnetic orientation in a part of the lipid membrane disturbed the release of ANS molecules from a hydrophobic region of the membrane.

  12. Lipid, membrane, and mitochondrial characteristics of Ustilago maydis following exposure to ergosterol biosynthesis inhibitors

    SciTech Connect

    Waterfield, W.F. III

    1986-01-01

    Pencoazole at 0.5 ..mu..g/ml inhibited ergosterol biosynthesis in U. maydis. Polar lipids of sporidia grown with 0.5 ..mu..g/ml penconazole for 7.5 or 22 hr or 1.0 ..mu..g/ml fenarimol for 7.5 hr contained more 18:2 than 18:1 fatty acids. There was usually more 18:1 than 18:2 fatty acids in polar lipids of untreated sporidia but this ratio was influenced by culture cell density. The high 18:2 to 18:1 ratio in the polar lipids from penconazole grown cells was unaffected by cell density. There was an increase in free fatty acids and these were enriched with 18:2 members in cells grown with 0.5 ..mu..g/ml penconazole for 22 hr. Unsaturation of triglycerides fatty acids did not differ appreciably from that of untreated sporidia. Untreated WT U. maydis protoplasts lysed more slowly in 0.3 M sorbitol than those prepared from WT sporidia grown for 16 hr with 1.0 ..mu..g/ml penconazole or 2.0 ..mu..g/ml fenarimol or from untreated erg-40 sporidia. Protoplasts were more permeable to crystal violet than were those from untreated WT sporidia. Mitochondria from untreated WT sporidia oxidizing pyruvate plus malate or succinate yielded higher ADP/O rations than mitochondria from erg-40 or penconazole grown WT sporidia. The mitochondrial ATPase of control cells had a Km of 0.8 mM ATP whereas the mitochondrial ATPase of penconazole grown WT and erg-40 had a Km value of 3.7 and 3.2 mM ATP, respectively. When the mitochondrial catalytic subunit of the ATPase from these mitochondria were solubilized, the Km did not differ. These studies suggest that changes in sterols and membrane fatty acids resulting from treatments with EBI fungicides cause increased membrane fluidity which affects membrane stability, permeability and activity of the mitochondrial ATPase.

  13. MPP1 as a Factor Regulating Phase Separation in Giant Plasma Membrane-Derived Vesicles

    PubMed Central

    Podkalicka, Joanna; Biernatowska, Agnieszka; Majkowski, Michał; Grzybek, Michał; Sikorski, Aleksander F.

    2015-01-01

    The existence of membrane-rafts helps to conceptually understand the spatiotemporal organization of membrane-associated events (signaling, fusion, fission, etc.). However, as rafts themselves are nanoscopic, dynamic, and transient assemblies, they cannot be directly observed in a metabolizing cell by traditional microscopy. The observation of phase separation in giant plasma membrane-derived vesicles from live cells is a powerful tool for studying lateral heterogeneity in eukaryotic cell membranes, specifically in the context of membrane rafts. Microscopic phase separation is detectable by fluorescent labeling, followed by cooling of the membranes below their miscibility phase transition temperature. It remains unclear, however, if this lipid-driven process is tuneable in any way by interactions with proteins. Here, we demonstrate that MPP1, a member of the MAGUK family, can modulate membrane properties such as the fluidity and phase separation capability of giant plasma membrane-derived vesicles. Our data suggest that physicochemical domain properties of the membrane can be modulated, without major changes in lipid composition, through proteins such as MPP1. PMID:25954878

  14. Bilayer membrane permeability of ionic liquid-filled block copolymer vesicles in aqueous solution.

    PubMed

    Bai, Zhifeng; Zhao, Bin; Lodge, Timothy P

    2012-07-19

    The bilayer membrane permeability of block copolymer vesicles ("polymersomes") with ionic liquid interiors dispersed in water is quantified using fluorescence quenching. Poly((1,2-butadiene)-b-ethylene oxide) (PB-PEO) block copolymer vesicles in water with their interiors filled with a common hydrophobic ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide, were prepared containing a hydrophobic dye, Nile Red, by intact migration of dye-encapsulated vesicles from the ionic liquid to water at room temperature. A small quencher molecule, dichloroacetamide, was added to the aqueous solution of the dye-loaded vesicles, and the permeation of the quencher passing through the membrane into the interior was determined from the fluorescence quenching kinetics. Rapid permeation of the quencher across the nanoscale membrane was observed, consistent with the high fluidity of the liquid polybutadiene membrane. Two different PB-PEO copolymers were employed, in order to vary the thickness of the solvophobic membrane. A significant increase in membrane permeability was also observed with decreasing membrane thickness, which is tentatively attributable to differences in quencher solubility in the membranes. Quantitative migration of the vesicles from the aqueous phase back to an ionic liquid phase was achieved upon heating. These microscopically heterogeneous and thermoresponsive vesicles with permeable and robust membranes have potential as recyclable nanoreactors, in which the high viscosity and capital expense of an ionic liquid reaction medium can be mitigated, while retaining the desirable features of ionic liquids as reaction media, and facile catalyst recovery.

  15. Mechanisms of Membrane Binding of Small GTPase K-Ras4B Farnesylated Hypervariable Region*

    PubMed Central

    Jang, Hyunbum; Abraham, Sherwin J.; Chavan, Tanmay S.; Hitchinson, Ben; Khavrutskii, Lyuba; Tarasova, Nadya I.; Nussinov, Ruth; Gaponenko, Vadim

    2015-01-01

    K-Ras4B belongs to a family of small GTPases that regulates cell growth, differentiation and survival. K-ras is frequently mutated in cancer. K-Ras4B association with the plasma membrane through its farnesylated and positively charged C-terminal hypervariable region (HVR) is critical to its oncogenic function. However, the structural mechanisms of membrane association are not fully understood. Here, using confocal microscopy, surface plasmon resonance, and molecular dynamics simulations, we observed that K-Ras4B can be distributed in rigid and loosely packed membrane domains. Its membrane binding domain interaction with phospholipids is driven by membrane fluidity. The farnesyl group spontaneously inserts into the disordered lipid microdomains, whereas the rigid microdomains restrict the farnesyl group penetration. We speculate that the resulting farnesyl protrusion toward the cell interior allows oligomerization of the K-Ras4B membrane binding domain in rigid microdomains. Unlike other Ras isoforms, K-Ras4B HVR contains a single farnesyl modification and positively charged polylysine sequence. The high positive charge not only modulates specific HVR binding to anionic phospholipids but farnesyl membrane orientation. Phosphorylation of Ser-181 prohibits spontaneous farnesyl membrane insertion. The mechanism illuminates the roles of HVR modifications in K-Ras4B targeting microdomains of the plasma membrane and suggests an additional function for HVR in regulation of Ras signaling. PMID:25713064

  16. Effects of DHA-phospholipids, melatonin and tryptophan supplementation on erythrocyte membrane physico-chemical properties in elderly patients suffering from mild cognitive impairment.

    PubMed

    Cazzola, Roberta; Rondanelli, Mariangela; Faliva, Milena; Cestaro, Benvenuto

    2012-12-01

    A randomized, double-blind placebo-controlled clinical trial was carried out to assess the efficacy of a docosahexenoic acid (DHA)-phospholipids, melatonin and tryptophan supplemented diet in improving the erythrocyte oxidative stress, membrane fluidity and membrane-bound enzyme activities of elderly subjects suffering from mild cognitive impairment (MCI). These subjects were randomly assigned to the supplement group (11 subjects, 9F and 2M; age 85.3±5.3y) or placebo group (14-matched subjects, 11F and 3M; 86.1±6.5). The duration of the treatment was 12weeks. The placebo group showed no significant changes in erythrocyte membrane composition and function. The erythrocyte membranes of the supplement group showed a significant increase in eicosapentenoic acid, docosapentenoic acid and DHA concentrations and a significant decrease in arachidonic acid, malondialdehyde and lipofuscin levels. These changes in membrane composition resulted in an increase in the unsaturation index, membrane fluidity and acetylcholine esterase activity. Moreover, a significant increase in the ratio between reduced and oxidized glutathione was observed in the erythrocyte of the supplement group. Although this study is a preliminary investigation, we believe these findings to be of great speculative and interpretative interest to better understand the complex and multi-factorial mechanisms behind the possible links between diets, their functional components and possible molecular processes that contribute to increasing the risk of developing MCI and Alzheimer's.

  17. Bivariate and multivariate analyses of the correlations between stability of the erythrocyte membrane, serum lipids and hematological variables.

    PubMed

    Bernardino Neto, M; de Avelar, E B; Arantes, T S; Jordão, I A; da Costa Huss, J C; de Souza, T M T; de Souza Penha, V A; da Silva, S C; de Souza, P C A; Tavares, M; Penha-Silva, N

    2013-01-01

    The observation that the fluidity must remain within a critical interval, outside which the stability and functionality of the cell tends to decrease, shows that stability, fluidity and function are related and that the measure of erythrocyte stability allows inferences about the fluidity or functionality of these cells. This study determined the biochemical and hematological variables that are directly or indirectly related to erythrocyte stability in a population of 71 volunteers. Data were evaluated by bivariate and multivariate analysis. The erythrocyte stability showed a greater association with hematological variables than the biochemical variables. The RDW stands out for its strong correlation with the stability of erythrocyte membrane, without being heavily influenced by other factors. Regarding the biochemical variables, the erythrocyte stability was more sensitive to LDL-C. Erythrocyte stability was significantly associated with RDW and LDL-C. Thus, the level of LDL-C is a consistent link between stability and functionality, suggesting that a measure of stability could be more one indirect parameter for assessing the risk of degenerative processes associated with high levels of LDL-C.

  18. Solid Character of Membrane Ceramides: A Surface Rheology Study of Their Mixtures with Sphingomyelin

    PubMed Central

    Catapano, Elisa R.; Arriaga, Laura R.; Espinosa, Gabriel; Monroy, Francisco; Langevin, Dominique; López-Montero, Iván

    2011-01-01

    The compression and shear viscoelasticities of egg-ceramide and its mixtures with sphingomyelin were investigated using oscillatory surface rheology performed on Langmuir monolayers. We found high values for the compression and shear moduli for ceramide, compatible with a solid-state membrane, and extremely high surface viscosities when compared to typical fluid lipids. A fluidlike rheological behavior was found for sphingomyelin. Lateral mobilities, measured from particle tracking experiments, were correlated with the monolayer viscosities through the usual hydrodynamic relationships. In conclusion, ceramide increases the solid character of sphingomyelin-based membranes and decreases their fluidity, thus drastically decreasing the lateral mobilities of embedded objects. This mechanical behavior may involve important physiological consequences in biological membranes containing ceramides. PMID:22261061

  19. Effects of static magnetic fields on growth and membrane lipid composition of Salmonella typhimurium wild-type and dam mutant strains.

    PubMed

    Mihoub, Mouadh; El May, Alya; Aloui, Amine; Chatti, Abdelwaheb; Landoulsi, Ahmed

    2012-07-02

    This study was carried out to explore the adaptive mechanisms of S. typhimurium particularly, the implication of the Dam methyltransferase in the remodelling of membrane lipid composition to overcome magnetic field stress. With this aim, we focused our analyses on the increase in viable numbers and membrane lipid modifications of S. typhimurium wild-type and dam mutant cells exposed for 10h to static magnetic fields (SMF; 200 mT). For the wild-type strain, exposure to SMF induced a significant decrease (p<0.05) of CFU at 6h, followed by an increase between 8 and 10h. Growth of the dam mutant was significantly affected (p<0.05) after 6h and no recovery was observed until 10h, highlighting a different behavior of SMF stressed wild-type and dam mutant strains. SMF significantly affected the phospholipid proportions in the two strains. The most affected were those of the acidic phospholipids, cardiolipins (CL). In the dam strain the phospholipid response to SMF followed a globally similar trend as in the wild-type with however lower effects, leading mainly to an unusual accumulation of CL. This would in part explain the different behavior of the wild-type and the dam strain. Results showed a significant increase of membrane cyclic fatty acids Cyc17 and Cyc19 in the wild-type strain but only the Cyc17 in the dam strain and a meaningful increase of the total unsaturated fatty acids (UFAs) to total saturated fatty acids (SFAs) ratios of the exposed cells compared to controls from 3 to 9h (p<0.05) for both strains. The net increase of the total UFAs to total SFAs ratios seemed to result mainly from the increase of (C18:1) proportion (p<0.05) and to a lower extent from that of (C16:1) (p<0.05). These modifications of cyclic and unsaturated fatty acid proportions constitute an adaptive response to SMF stress in S. typhimurium wild-type and dam mutants to maintain an optimum level of membrane fluidity under SMF.

  20. Crystalline Membranes

    NASA Technical Reports Server (NTRS)

    Tsapatsis, Michael (Inventor); Lai, Zhiping (Inventor)

    2008-01-01

    In certain aspects, the invention features methods for forming crystalline membranes (e.g., a membrane of a framework material, such as a zeolite) by inducing secondary growth in a layer of oriented seed crystals. The rate of growth of the seed crystals in the plane of the substrate is controlled to be comparable to the rate of growth out of the plane. As a result, a crystalline membrane can form a substantially continuous layer including grains of uniform crystallographic orientation that extend through the depth of the layer.

  1. Involvement of endometrial membrane sulphydryl groups in blastocyst implantation: sulphydryl groups as a potential target for contraceptive research.

    PubMed

    Nivsarkar, M; Sethi, A; Bapu, C; Patel, M; Padh, H

    2001-10-01

    The role of membrane sulphydryl groups in blastocyst implantation was studied by masking the membrane sulphydryl groups in the endometrium of Swiss albino mice, Mus musculus, using 10(-5) M cobalt chloride and 0.05 mM as well as 0.005 mM n-ethylmaleimide. Here we show that the blocking of sulphydryl groups with cobalt resulted in a decrease in superoxide radical surge and an increase in superoxide dismutase levels at the time of implantation. We hypothesize that it may be due to either a decrease in membrane fluidity or the unavailability of sulphydryl groups of endometrial membrane, thus preventing blastocyst implantation. These sulphydryl groups can be targeted for future contraceptive research.

  2. Antibacterial Activity of Shikimic Acid from Pine Needles of Cedrus deodara against Staphylococcus aureus through Damage to Cell Membrane

    PubMed Central

    Bai, Jinrong; Wu, Yanping; Liu, Xiaoyan; Zhong, Kai; Huang, Yina; Gao, Hong

    2015-01-01

    Shikimic acid (SA) has been reported to possess antibacterial activity against Staphylococcus aureus, whereas the mode of action of SA is still elusive. In this study, the antibacterial activity and mechanism of SA toward S. aureus by cell membrane damage was investigated. After SA treatment, massive K+ and nucleotide leakage from S. aureus, and a significant change in the membrane potential was observed, suggesting SA may act on the membrane by destroying the cell membrane permeability. Through transmission electron microscopic observations we further confirmed that SA can disrupt the cell membrane and membrane integrity. Meanwhile, SA was found to be capable of reducing the membrane fluidity of the S. aureus cell. Moreover, the fluorescence experiments indicated that SA could quench fluorescence of Phe residues of the membrane proteins, thus demonstrating that SA can bind to S. aureus membrane proteins. Therefore, these results showed the antibacterial activity of SA against S. aureus could be caused by the interactions of SA with S. aureus membrane proteins and lipids, resulting in causing cell membrane dysfunction and bacterial damage or even death. This study reveals the potential use of SA as an antibacterial agent. PMID:26580596

  3. Plasma membrane ordering agent pluronic F-68 (PF-68) reduces neurotransmitter uptake and release and produces learning and memory deficits in rats

    NASA Technical Reports Server (NTRS)

    Clarke, M. S.; Prendergast, M. A.; Terry, A. V. Jr

    1999-01-01

    A substantial body of evidence indicates that aged-related changes in the fluidity and lipid composition of the plasma membrane contribute to cellular dysfunction in humans and other mammalian species. In the CNS, reductions in neuronal plasma membrane order (PMO) (i.e., increased plasma membrane fluidity) have been attributed to age as well as the presence of the beta-amyloid peptide-25-35, known to play an important role in the neuropathology of Alzheimer's disease (AD). These PMO increases may influence neurotransmitter synthesis, receptor binding, and second messenger systems as well as signal transduction pathways. The effects of neuronal PMO on learning and memory processes have not been adequately investigated, however. Based on the hypothesis that an increase in PMO may alter a number of aspects of synaptic transmission, we investigated several neurochemical and behavioral effects of the membrane ordering agent, PF-68. In cell culture, PF-68 (nmoles/mg SDS extractable protein) reduced [3H]norepinephrine (NE) uptake into differentiated PC-12 cells as well as reduced nicotine stimulated [3H]NE release. The compound (800-2400 microg/kg, i.p., resulting in nmoles/mg SDS extractable protein in the brain) decreased step-through latencies and increased the frequencies of crossing into the unsafe side of the chamber in inhibitory avoidance training. In the Morris water maze, PF-68 increased the latencies and swim distances required to locate a hidden platform and reduced the time spent and distance swam in the previous target quadrant during transfer (probe) trials. PF-68 did not impair performance of a well-learned working memory task, the rat delayed stimulus discrimination task (DSDT), however. Studies with 14C-labeled PF-68 indicated that significant (pmoles/mg wet tissue) levels of the compound entered the brain from peripheral (i.p.) injection. No PF-68 related changes were observed in swim speeds or in visual acuity tests in water maze experiments, rotorod

  4. Biological membranes

    PubMed Central

    Watson, Helen

    2015-01-01

    Biological membranes allow life as we know it to exist. They form cells and enable separation between the inside and outside of an organism, controlling by means of their selective permeability which substances enter and leave. By allowing gradients of ions to be created across them, membranes also enable living organisms to generate energy. In addition, they control the flow of messages between cells by sending, receiving and processing information in the form of chemical and electrical signals. This essay summarizes the structure and function of membranes and the proteins within them, and describes their role in trafficking and transport, and their involvement in health and disease. Techniques for studying membranes are also discussed. PMID:26504250

  5. Drug-Membrane Interactions Studied by Vibrational Sum-Frequency Spectroscopy

    NASA Astrophysics Data System (ADS)

    Wolf, Lauren; Briggman, Kimberly

    2008-03-01

    The activity of a number of drugs depends directly on their interaction with cell membranes and, thus, an understanding of drug-membrane interactions is necessary for improving their pharmacological performance. Drug molecules can interact with membranes by directly binding to membrane-bound proteins or by intercalating into the lipid matrix itself, altering membrane properties such as fluidity, thickness, internal pressure, and phase transition temperature. Here, we focus on the effects of local anesthetics incorporated into the lipid matrix, studying the structural changes induced in supported lipid bilayers by vibrational sum-frequency spectroscopy (VSFS). We find that in addition to depressing the phase transition temperature of the lipid bilayers, most anesthetics also sharpen the gel to liquid- crystalline transition, suggesting an increase in membrane constituent cooperativity. This behavior contrasts the effects of cholesterol on lipid bilayers, which increases membrane rigidity and broadens the phase transition. The structure of the membrane-intercalated anesthetics themselves will also be discussed. This work demonstrates the potential of using supported lipid bilayers and surface-sensitive techniques for future pharmacological studies.

  6. Biomimetic interfaces based on S-layer proteins, lipid membranes and functional biomolecules

    PubMed Central

    Schuster, Bernhard; Sleytr, Uwe B.

    2014-01-01

    Designing and utilization of biomimetic membrane systems generated by bottom-up processes is a rapidly growing scientific and engineering field. Elucidation of the supramolecular construction principle of archaeal cell envelopes composed of S-layer stabilized lipid membranes led to new strategies for generating highly stable functional lipid membranes at meso- and macroscopic scale. In this review, we provide a state-of-the-art survey of how S-layer proteins, lipids and polymers may be used as basic building blocks for the assembly of S-layer-supported lipid membranes. These biomimetic membrane systems are distinguished by a nanopatterned fluidity, enhanced stability and longevity and, thus, provide a dedicated reconstitution matrix for membrane-active peptides and transmembrane proteins. Exciting areas in the (lab-on-a-) biochip technology are combining composite S-layer membrane systems involving specific membrane functions with the silicon world. Thus, it might become possible to create artificial noses or tongues, where many receptor proteins have to be exposed and read out simultaneously. Moreover, S-layer-coated liposomes and emulsomes copying virus envelopes constitute promising nanoformulations for the production of novel targeting, delivery, encapsulation and imaging systems. PMID:24812051

  7. Relationship between erythrocyte membrane phase properties and susceptibility to secretory phospholipase A2.

    PubMed

    Best, Katrina B; Ohran, Allison J; Hawes, Andrea C; Hazlett, Theodore L; Gratton, Enrico; Judd, Allan M; Bell, John D

    2002-11-26

    Normally, cell membranes resist hydrolysis by secretory phospholipase A(2). However, upon elevation of intracellular calcium, the cells become susceptible. Previous investigations demonstrated a possible relationship between changes in lipid order caused by increased calcium and susceptibility to phospholipase A(2). To further explore this relationship, we used temperature as an experimental means of manipulating membrane physical properties. We then compared the response of human erythrocytes to calcium ionophore at various temperatures in the range of 20-50 degrees C using fluorescence spectroscopy and two-photon fluorescence microscopy. The steady state fluorescence emission of the environment-sensitive probe, laurdan, revealed that erythrocyte membrane order decreases systematically with temperature throughout this range, especially between 28 and 45 degrees C. Furthermore, the ability of calcium ionophore to induce increased membrane order and susceptibility to phospholipase A(2) depended similarly on temperature. Both responses to calcium influx were enhanced as membrane fluidity increased. Analysis of the spatial distribution of laurdan fluorescence at several temperatures indicated that the ordering effect of intracellular calcium on fluid membranes generates an increase in the number of fluid-solid boundaries. Hydrolysis of the membrane appeared to progress outward from these boundaries. We conclude that phospholipase A(2) prefers to hydrolyze lipids in fluid regions of human erythrocyte membranes, but primarily when those regions coexist with domains of ordered lipids.

  8. Influence of the glycocalyx and plasma membrane composition on amphiphilic gold nanoparticle association with erythrocytes.

    PubMed

    Atukorale, Prabhani U; Yang, Yu-Sang; Bekdemir, Ahmet; Carney, Randy P; Silva, Paulo J; Watson, Nicki; Stellacci, Francesco; Irvine, Darrell J

    2015-07-14

    Erythrocytes are attractive as potential cell-based drug carriers because of their abundance and long lifespan in vivo. Existing methods for loading drug cargos into erythrocytes include hypotonic treatments, electroporation, and covalent attachment onto the membrane, all of which require ex vivo manipulation. Here, we characterized the properties of amphiphilic gold nanoparticles (amph-AuNPs), comprised of a ∼2.3 nm gold core and an amphiphilic ligand shell, which are able to embed spontaneously within erythrocyte membranes and might provide a means to load drugs into red blood cells (RBCs) directly in vivo. Particle interaction with RBC membranes occurred rapidly at physiological temperature. We further show that amph-AuNP uptake by RBCs was limited by the glycocalyx and was particularly influenced by sialic acids on cell surface proteoglycans. Using a reductionist model membrane system with synthetic lipid vesicles, we confirmed the importance of membrane fluidity and the glycocalyx in regulating amph-AuNP/membrane interactions. These results thus provide evidence for the interaction of amph-AuNPs with erythrocyte membranes and identify key membrane components that govern this interaction, providing a framework for the development of amph-AuNP-carrying erythrocyte 'pharmacytes' in vivo.

  9. Biomimetic interfaces based on S-layer proteins, lipid membranes and functional biomolecules.

    PubMed

    Schuster, Bernhard; Sleytr, Uwe B

    2014-07-06

    Designing and utilization of biomimetic membrane systems generated by bottom-up processes is a rapidly growing scientific and engineering field. Elucidation of the supramolecular construction principle of archaeal cell envelopes composed of S-layer stabilized lipid membranes led to new strategies for generating highly stable functional lipid membranes at meso- and macroscopic scale. In this review, we provide a state-of-the-art survey of how S-layer proteins, lipids and polymers may be used as basic building blocks for the assembly of S-layer-supported lipid membranes. These biomimetic membrane systems are distinguished by a nanopatterned fluidity, enhanced stability and longevity and, thus, provide a dedicated reconstitution matrix for membrane-active peptides and transmembrane proteins. Exciting areas in the (lab-on-a-) biochip technology are combining composite S-layer membrane systems involving specific membrane functions with the silicon world. Thus, it might become possible to create artificial noses or tongues, where many receptor proteins have to be exposed and read out simultaneously. Moreover, S-layer-coated liposomes and emulsomes copying virus envelopes constitute promising nanoformulations for the production of novel targeting, delivery, encapsulation and imaging systems.

  10. The location of organotins within the erythrocyte membrane in relation to their toxicity.

    PubMed

    Bonarska-Kujawa, Dorota; Kleszczyńska, Halina; Przestalski, Stanisław

    2012-04-01

    The aim of the present study on organotin compounds, which are toxic to biological systems, was to determine the relationship between the compounds' toxicity and their location in the lipid bilayer of the biological membrane. It was assumed that the degree of disturbance caused within the lipid bilayer of the membrane, which in turn depends on the depth of incorporation, was an appropriate measure of toxicity. Previous results from our studies on the effect of organotin chlorides on membranes, made by using infrared radiation and hemolysis of erythrocytes, indicated that tributyltin (TBT) is the most active in terms of its interaction with the erythrocyte membrane. This compound causes the most severe hemolysis of erythrocytes and dehydration of membrane constituents. In order to connect the changes induced within the membrane structure with the compounds' location, we have investigated erythrocyte shape changes using both microscopic and fluorimetric methods. The microscopic results show that organotin compounds accumulate in the outer monolayer of the membrane. The fluorimetric studies indicate that all the compounds are present in the hydrophilic part of the outer lipid monolayer, and change the order parameter of the layer. However, only tributyltin, by being incorporated into the hydrophobic region of the monolayer, changes the fluidity in the alkyl chain region of the erythrocyte membrane. Furthermore, only TBT is present in both the hydrophilic and hydrophobic regions, as evidenced by the changed order parameter of the polar groups and fluorescence anisotropy of DPH probe in the hydrophobic region, these being connected with its high toxicity.

  11. Methoxypolyethylene glycol-block-polycaprolactone diblock copolymers reduce P-glycoprotein efflux in the absence of a membrane fluidization effect while stimulating P-glycoprotein ATPase activity.

    PubMed

    Zastre, Jason; Jackson, John K; Wong, Wesley; Burt, Helen M

    2007-04-01

    We have previously shown that amphiphilic diblock copolymers composed of methoxypolyethylene glycol-b-polycaprolactone (MePEG-b-PCL) increased the cellular accumulation and reduced the basolateral to apical flux of the P-glycoprotein substrate, rhodamine 123 (R-123) in caco-2 cells. The purpose of this study was to investigate membrane perturbation effects of MePEG-b-PCL diblock copolymers with erythrocyte membranes and caco-2 cells and the effect on P-gp ATPase activity. The diblock copolymer MePEG(17)-b-PCL(5) induced increasing erythrocyte hemolysis at concentrations which correlated with increasing accumulation of R-123 into caco-2 cells. However, no increase in cellular accumulation of R-123 by non-P-gp expressing cells was observed, suggesting that diblock did not enhance the transmembrane passive diffusion of R-123, but that the accumulation enhancement effect of the diblock in caco-2 cells was likely mediated primarily via P-gp inhibition. Fluorescence anisotropy measurements of membrane fluidity and P-gp ATPase activity demonstrated that MePEG(17)-b-PCL(5) decreased caco-2 membrane fluidity while stimulating ATPase activity approximately threefold at concentrations that maximally enhanced R-123 caco-2 accumulation. These results suggest that inhibition of P-gp efflux by MePEG(17)-b-PCL(5) does not appear to be related to increases in membrane fluidity or through inhibition in P-gp ATPase activities, which are two commonly reported cellular effects for P-gp inhibition mediated by surfactants.

  12. Membrane organization and regulation of cellular Cholesterol homeostasis

    PubMed Central

    Jaureguiberry, María S.; Tricerri, M. Alejandra; Sanchez, Susana A; Garda, Horacio A; Finarelli, Gabriela S.; Gonzalez, Marina C.; Rimoldi, Omar J.

    2010-01-01

    An excess of intracellular free Cholesterol (Chol) is cytotoxic, and its homeostasis is crucial for cell viability. Apolipoprotein A–I (apoA-I) is a highly efficient Chol acceptor as it activates complex cellular pathways that tend to mobilize and export Chol from cellular depots. Here we hypothesize that membrane composition and/or organization is strongly involved in Chol homeostasis. To test this hypothesis, we constructed a cell line over expressing Stearoyl CoA desaturase (SCD-cells), which modifies plasma membrane (PM) composition by the enrichment of monounsaturated fatty,acids and determined this effect on membrane properties, cell viability and cholesterol homeostasis. PM in SCD-cells has a higher phospholipids/sphingomyelin ratio and is slightly enriched in Chol. These cells showed an increase in the cholesteryl esters/free Chol ratio, they were more resistant to Chol toxicity and in addition, they exported more caveolin than Control cells. The data suggest that cell functionality is preserved by regulating membrane fluidity and Chol exportation and storage. PMID:20336284

  13. Membrane organization and regulation of cellular cholesterol homeostasis.

    PubMed

    Jaureguiberry, María S; Tricerri, M Alejandra; Sanchez, Susana A; Garda, Horacio A; Finarelli, Gabriela S; Gonzalez, Marina C; Rimoldi, Omar J

    2010-04-01

    An excess of intracellular free cholesterol (Chol) is cytotoxic, and its homeostasis is crucial for cell viability. Apolipoprotein A-I (apoA-I) is a highly efficient Chol acceptor because it activates complex cellular pathways that tend to mobilize and export Chol from cellular depots. We hypothesize that membrane composition and/or organization is strongly involved in Chol homeostasis. To test this hypothesis, we constructed a cell line overexpressing stearoyl coenzyme A (CoA) desaturase (SCD cells), which modifies plasma membrane (PM) composition by the enrichment of monounsaturated fatty acids, and determined this effect on membrane properties, cell viability, and Chol homeostasis. PM in SCD cells has a higher ratio of phospholipids to sphingomyelin and is slightly enriched in Chol. These cells showed an increase in the ratio of cholesteryl esters to free Chol; they were more resistant to Chol toxicity, and they exported more caveolin than control cells. The data suggest that cell functionality is preserved by regulating membrane fluidity and Chol exportation and storage.

  14. Oxygen Transport Ceramic Membranes

    SciTech Connect

    S. Bandopadhyay; T. Nithyanantham; X.-D Zhou; Y-W. Sin; H.U. Anderson; Alan Jacobson; C.A. Mims

    2005-11-01

    The present quarterly report describes some of the investigations on the structural properties of dense OTM bars provided by Praxair and studies on newer composition of Ti doped LSF. In the current research, the electrical conductivity and Seebeck coefficient were measured as a function of temperature in air. Based on these measurements, the charge carrier concentration, net acceptor dopant concentration, activation energy of conduction and mobility were estimated. The studies on the fracture toughness of the LSFT and dual phase membranes at room temperature have been completed and reported previously. The membranes that are exposed to high temperatures at an inert and a reactive atmosphere undergo many structural and chemical changes which affects the mechanical properties. To study the effect of temperature on the membranes when exposed to an inert environment, the membranes (LAFT and Dual phase) were heat treated at 1000 C in air and N{sub 2} atmosphere and hardness and fracture toughness of the membranes were studied after the treatment. The indentation method was used to find the fracture toughness and the effect of the heat treatment on the mechanical properties of the membranes. Further results on the investigation of the origin of the slow kinetics on reduction of ferrites have been obtained. The slow kinetics appears to be related to a non-equilibrium reduction pathway that initially results in the formation of iron particles. At long times, equilibrium can be reestablished with recovery of the perovskite phase. 2-D modeling of oxygen movement has been undertaken in order to fit isotope data. The model will serve to study ''frozen'' profiles in patterned or composite membranes.

  15. Can Cholesterol Metabolism Modulation Affect Brain Function and Behavior?

    PubMed

    Cartocci, Veronica; Servadio, Michela; Trezza, Viviana; Pallottini, Valentina

    2017-02-01

    Cholesterol is an important component for cell physiology. It regulates the fluidity of cell membranes and determines the physical and biochemical properties of proteins. In the central nervous system, cholesterol controls synapse formation and function and supports the saltatory conduction of action potential. In recent years, the role of cholesterol in the brain has caught the attention of several research groups since a breakdown of cholesterol metabolism has been associated with different neurodevelopmental and neurodegenerative diseases, and interestingly also with psychiatric conditions. The aim of this review is to summarize the current knowledge about the connection between cholesterol dysregulation and various neurologic and psychiatric disorders based on clinical and preclinical studies. J. Cell. Physiol. 232: 281-286, 2017. © 2016 Wiley Periodicals, Inc.

  16. Alkyl Galactofuranosides Strongly Interact with Leishmania donovani Membrane and Provide Antileishmanial Activity

    PubMed Central

    Suleman, Muhammad; Gangneux, Jean-Pierre; Legentil, Laurent; Belaz, Sorya; Cabezas, Yari; Manuel, Christelle; Dureau, Rémy; Sergent, Odile; Burel, Agnès; Daligault, Franck; Ferrières, Vincent

    2014-01-01

    We investigated the in vitro effects of four alkyl-galactofuranoside derivatives, i.e., octyl-β-d-galactofuranoside (compound 1), 6-amino-β-d-galactofuranoside (compound 2), 6-N-acetamido-β-d-galactofuranoside (compound 3), and 6-azido-β-d-galactofuranoside (compound 4), on Leishmania donovani. Their mechanism of action was explored using electron paramagnetic resonance spectroscopy (EPR) and nuclear magnetic resonance (NMR), and ultrastructural alterations were analyzed by transmission electron microscopy (TEM). Compound 1 showed the most promising effects by inhibiting promastigote growth at a 50% inhibitory concentration (IC50) of 8.96 ± 2.5 μM. All compounds exhibit low toxicity toward human macrophages. Compound 1 had a higher selectivity index than the molecule used for comparison, i.e., miltefosine (159.7 versus 37.9, respectively). EPR showed that compound 1 significantly reduced membrane fluidity compared to control promastigotes and to compound 3. The furanose ring was shown to support this effect, since the isomer galactopyranose had no effect on parasite membrane fluidity or growth. NMR showed a direct interaction of all compounds (greatest with compound 1, followed by compounds 2, 3, and 4, in descending order) with the promastigote membrane and with octyl-galactopyranose and octanol, providing evidence that the n-octyl chain was primarily involved in anchoring with the parasite membrane, followed by the putative crucial role of the furanose ring in the antileishmanial activity. A morphological analysis of compound 1-treated promastigotes by TEM revealed profound alterations in the parasite membrane and organelles, but this was not the case with compound 3. Quantification of annexin V binding by flow cytometry confirmed that compound 1 induced apoptosis in >90% of promastigotes. The effect of compound 1 was also assessed on intramacrophagic amastigotes and showed a reduction in amastigote growth associated with an increase of reactive oxygen

  17. Alkyl galactofuranosides strongly interact with Leishmania donovani membrane and provide antileishmanial activity.

    PubMed

    Suleman, Muhammad; Gangneux, Jean-Pierre; Legentil, Laurent; Belaz, Sorya; Cabezas, Yari; Manuel, Christelle; Dureau, Rémy; Sergent, Odile; Burel, Agnès; Daligault, Franck; Ferrières, Vincent; Robert-Gangneux, Florence

    2014-01-01

    We investigated the in vitro effects of four alkyl-galactofuranoside derivatives, i.e., octyl-β-D-galactofuranoside (compound 1), 6-amino-β-D-galactofuranoside (compound 2), 6-N-acetamido-β-D-galactofuranoside (compound 3), and 6-azido-β-D-galactofuranoside (compound 4), on Leishmania donovani. Their mechanism of action was explored using electron paramagnetic resonance spectroscopy (EPR) and nuclear magnetic resonance (NMR), and ultrastructural alterations were analyzed by transmission electron microscopy (TEM). Compound 1 showed the most promising effects by inhibiting promastigote growth at a 50% inhibitory concentration (IC50) of 8.96±2.5 μM. All compounds exhibit low toxicity toward human macrophages. Compound 1 had a higher selectivity index than the molecule used for comparison, i.e., miltefosine (159.7 versus 37.9, respectively). EPR showed that compound 1 significantly reduced membrane fluidity compared to control promastigotes and to compound 3. The furanose ring was shown to support this effect, since the isomer galactopyranose had no effect on parasite membrane fluidity or growth. NMR showed a direct interaction of all compounds (greatest with compound 1, followed by compounds 2, 3, and 4, in descending order) with the promastigote membrane and with octyl-galactopyranose and octanol, providing evidence that the n-octyl chain was primarily involved in anchoring with the parasite membrane, followed by the putative crucial role of the furanose ring in the antileishmanial activity. A morphological analysis of compound 1-treated promastigotes by TEM revealed profound alterations in the parasite membrane and organelles, but this was not the case with compound 3. Quantification of annexin V binding by flow cytometry confirmed that compound 1 induced apoptosis in >90% of promastigotes. The effect of compound 1 was also assessed on intramacrophagic amastigotes and showed a reduction in amastigote growth associated with an increase of reactive oxygen

  18. Interaction study between maltose-modified PPI dendrimers and lipidic model membranes.

    PubMed

    Wrobel, Dominika; Appelhans, Dietmar; Signorelli, Marco; Wiesner, Brigitte; Fessas, Dimitrios; Scheler, Ulrich; Voit, Brigitte; Maly, Jan

    2015-07-01

    The influence of maltose-modified poly(propylene imine) (PPI) dendrimers on dimyristoylphosphatidylcholine (DMPC) or dimyristoylphosphatidylcholine/dimyristoylphosphatidylglycerol (DMPC/DMPG) (3%) liposomes was studied. Fourth generation (G4) PPI dendrimers with primary amino surface groups were partially (open shell glycodendrimers - OS) or completely (dense shell glycodendrimers - DS) modified with maltose residues. As a model membrane, two types of 100nm diameter liposomes were used to observe differences in the interactions between neutral DMPC and negatively charged DMPC/DMPG bilayers. Interactions were studied using fluorescence spectroscopy to evaluate the membrane fluidity of both the hydrophobic and hydrophilic parts of the lipid bilayer and using differential scanning calorimetry to investigate thermodynamic parameter changes. Pulsed-filed gradient NMR experiments were carried out to evaluate common diffusion coefficient of DMPG and DS PPI in D2O when using below critical micelle concentration of DMPG. Both OS and DS PPI G4 dendrimers show interactions with liposomes. Neutral DS dendrimers exhibit stronger changes in membrane fluidity compared to OS dendrimers. The bilayer structure seems more rigid in the case of anionic DMPC/DMPG liposomes in comparison to pure and neutral DMPC liposomes. Generally, interactions of dendrimers with anionic DMPC/DMPG and neutral DMPC liposomes were at the same level. Higher concentrations of positively charged OS dendrimers induced the aggregation process with negatively charged liposomes. For all types of experiments, the presence of NaCl decreased the strength of the interactions between glycodendrimers and liposomes. Based on NMR diffusion experiments we suggest that apart from electrostatic interactions for OS PPI hydrogen bonds play a major role in maltose-modified PPI dendrimer interactions with anionic and neutral model membranes where a contact surface is needed for undergoing multiple H-bond interactions between

  19. The Effect of Acute Microgravity on Mechanically-Induced Membrane Damage and Membrane-Membrane Fusion Events

    NASA Technical Reports Server (NTRS)

    Clarke, Mark, S. F.; Vanderburg, Charles R.; Feedback, Daniel L.

    2001-01-01

    Although it is unclear how a living cell senses gravitational forces there is no doubt that perturbation of the gravitational environment results in profound alterations in cellular function. In the present study, we have focused our attention on how acute microgravity exposure during parabolic flight affects the skeletal muscle cell plasma membrane (i.e. sarcolemma), with specific reference to a mechanically-reactive signaling mechanism known as mechanically-induced membrane disruption or "wounding". This response is characterized by both membrane rupture and membrane resealing events mediated by membrane-membrane fusion. We here present experimental evidence that acute microgravity exposure can inhibit membrane-membrane fusion events essential for the resealing of sarcolemmal wounds in individual human myoblasts. Additional evidence to support this contention comes from experimental studies that demonstrate acute microgravity exposure also inhibits secretagogue-stimulated intracellular vesicle fusion with the plasma membrane in HL-60 cells. Based on our own observations and those of other investigators in a variety of ground-based models of membrane wounding and membrane-membrane fusion, we suggest that the disruption in the membrane resealing process observed during acute microgravity is consistent with a microgravity-induced decrease in membrane order.

  20. The effect of acute microgravity on mechanically-induced membrane damage and membrane-membrane fusion events

    NASA Technical Reports Server (NTRS)

    Clarke, M. S.; Vanderburg, C. R.; Feeback, D. L.; McIntire, L. V. (Principal Investigator)

    2001-01-01

    Although it is unclear how a living cell senses gravitational forces there is no doubt that perturbation of the gravitational environment results in profound alterations in cellular function. In the present study, we have focused our attention on how acute microgravity exposure during parabolic flight affects the skeletal muscle cell plasma membrane (i.e. sarcolemma), with specific reference to a mechanically-reactive signaling mechanism known as mechanically-induced membrane disruption or "wounding". Both membrane rupture and membrane resealing events mediated by membrane-membrane fusion characterize this response. We here present experimental evidence that acute microgravity exposure can inhibit membrane-membrane fusion events essential for the resealing of sarcolemmal wounds in individual human myoblasts. Additional evidence to support this contention comes from experimental studies that demonstrate acute microgravity exposure also inhibits secretagogue-stimulated intracellular vesicle fusion with the plasma membrane in HL-60 cells. Based on our own observations and those of other investigators in a variety of ground-based models of membrane wounding and membrane-membrane fusion, we suggest that the disruption in the membrane resealing process observed during acute microgravity is consistent with a microgravity-induced decrease in membrane order.

  1. Modifications in membrane fatty acid composition of Salmonella typhimurium in response to growth conditions and their effect on heat resistance.

    PubMed

    Alvarez-Ordóñez, Avelino; Fernández, Ana; López, Mercedes; Arenas, Ricardo; Bernardo, Ana

    2008-04-30

    The effects of growth temperature (in the range 10-45 degrees C) and acidification up to pH 4.5 of the culture medium (Brain Heart Infusion, BHI) with different organic acids (acetic, citric and lactic) and hydrochloric acid on membrane fatty acid composition and heat resistance of Salmonella typhimurium CECT 443 were studied. The heat resistance was maximal in cells grown at 45 degrees C (cells grown in non-acidified BHI showed a D58-value of 0.90 min) and decreased with decreasing growth temperature up to 10 degrees C (D58-value of 0.09 min). The growth of cells in acidified media caused an increase in their heat resistance. In general, acid adapted cells showed D-values of between 1.5 and 2 times higher than the corresponding for non-acid adapted control cells. This cross-protection response, which has important implications in food processing, was not dependent on the pH value and the acid used to acidify the growth medium. A membrane adaptation corresponding to an increase in the unsaturated to saturated fatty acids ratio (UFA/SFA) and membrane fluidity was observed at low growth temperature. Moreover, the acidification of the growth medium caused a decrease in UFA/SFA ratio and in the C18:1 relative concentration, and an increase in cyclopropane fatty acids (CFA) content mainly due to the increase in cyc19 relative concentration. Thus, acid adapted cells showed CFA levels 1.5 times higher than non-acid adapted control cells. A significant proportion of unsaturated fatty acids were converted to their cyclopropane derivatives during acid adaptation. These changes in membrane fatty acid composition result in cells with decreased membrane fluidity. A clear relation between membrane fatty acid composition and heat resistance was observed. In general, D-values were maximum for cells with low UFA/SFA ratio, and, consequently, with low membrane fluidity. Moreover, CFA formation played a major role in protecting acid adapted cells from heat inactivation. However

  2. Metamaterial membranes

    NASA Astrophysics Data System (ADS)

    Restrepo-Flórez, Juan Manuel; Maldovan, Martin

    2017-01-01

    We introduce a new class of metamaterial device to achieve separation of compounds by using coordinate transformations and metamaterial theory. By rationally designing the spatial anisotropy for mass diffusion, we simultaneously concentrate different compounds in different spatial locations, leading to separation of mixtures across a metamaterial membrane. The separation of mixtures into their constituent compounds is critically important in biophysics, biomedical, and chemical applications. We present a practical case where a mixture of oxygen and nitrogen diffusing through a polymeric planar matrix is separated. This work opens doors to new paradigms in membrane separations via coordinate transformations and metamaterials by introducing novel properties and unconventional mass diffusion phenomena.

  3. Dietary n-6:n-3 ratio and Vitamin E improve motility characteristics in association with membrane properties of boar spermatozoa

    PubMed Central

    Liu, Qing; Zhou, Yuan-Fei; Duan, Run-Jia; Wei, Hong-Kui; Peng, Jian; Jiang, Si-Wen

    2017-01-01

    This study was aimed to evaluate the effects of dietary n-6:n-3 ratio and Vitamin E on the membrane properties and motility characteristics of spermatozoa in boars. Forty Duroc boars were randomly distributed in a 2 × 2 factorial design with two n-6:n-3 ratios (14.4 and 6.6) and two Vitamin E levels (200 and 400 mg kg−1). During 16 weeks of treatment, fresh semen was collected at weeks 0, 8, 12, and 16 for measurements of motility characteristics, contents of fatty acids, membrane properties (membrane fluidity and membrane integrity), and lipid peroxidation of the spermatozoa. The semen was diluted in Beltsville Thawing Solution (BTS) extender and stored at 17°C, and the sperm motility was assessed at 12, 36, 72, and 120 h of storage. The 6.6 n-6:n-3 dietary ratio increased the contents of n-3 polyunsaturated fatty acids (PUFAs) and docosahexaenoic acid (DHA) and improved the membrane integrity and membrane fluidity of the spermatozoa, resulting in notably increased total motility, sperm progressive motility, and velocity parameters of fresh semen. Feeding diet with Vitamin E (400 mg kg−1) prevented sperm lipid peroxidation, and resulted in higher total motility and sperm progressive motility in fresh and liquid stored semen. In conclusion, the adjustment of n-6:n-3 ratio (6.6) and supply of Vitamin E (400 mg kg−1) successfully improved sperm motility characteristics and thus may be beneficial to the fertility of boars, which might be due to the modification of the physical and functional properties of spermatozoa membrane in response to dietary supplementation. PMID:26763547

  4. Dietary n-6:n-3 ratio and Vitamin E improve motility characteristics in association with membrane properties of boar spermatozoa.

    PubMed

    Liu, Qing; Zhou, Yuan-Fei; Duan, Run-Jia; Wei, Hong-Kui; Peng, Jian; Jiang, Si-Wen

    2017-01-01

    This study was aimed to evaluate the effects of dietary n-6:n-3 ratio and Vitamin E on the membrane properties and motility characteristics of spermatozoa in boars. Forty Duroc boars were randomly distributed in a 2 × 2 factorial design with two n-6:n-3 ratios (14.4 and 6.6) and two Vitamin E levels (200 and 400 mg kg-1 ). During 16 weeks of treatment, fresh semen was collected at weeks 0, 8, 12, and 16 for measurements of motility characteristics, contents of fatty acids, membrane properties (membrane fluidity and membrane integrity), and lipid peroxidation of the spermatozoa. The semen was diluted in Beltsville Thawing Solution (BTS) extender and stored at 17°C, and the sperm motility was assessed at 12, 36, 72, and 120 h of storage. The 6.6 n-6:n-3 dietary ratio increased the contents of n-3 polyunsaturated fatty acids (PUFAs) and docosahexaenoic acid (DHA) and improved the membrane integrity and membrane fluidity of the spermatozoa, resulting in notably increased total motility, sperm progressive motility, and velocity parameters of fresh semen. Feeding diet with Vitamin E (400 mg kg-1 ) prevented sperm lipid peroxidation, and resulted in higher total motility and sperm progressive motility in fresh and liquid stored semen. In conclusion, the adjustment of n-6:n-3 ratio (6.6) and supply of Vitamin E (400 mg kg-1 ) successfully improved sperm motility characteristics and thus may be beneficial to the fertility of boars, which might be due to the modification of the physical and functional properties of spermatozoa membrane in response to dietary supplementation.

  5. Seminal plasma applied post-thawing affects boar sperm physiology: a flow cytometry study.

    PubMed

    Fernández-Gago, Rocío; Domínguez, Juan Carlos; Martínez-Pastor, Felipe

    2013-09-01

    Cryopreservation induces extensive biophysical and biochemical changes in the sperm. In the present study, we used flow cytometry to assess the capacitation-like status of frozen-thawed boar spermatozoa and its relationship with intracellular calcium, assessment of membrane fluidity, modification of thiol groups in plasma membrane proteins, reactive oxygen species (ROS) levels, viability, acrosomal status, and mitochondrial activity. This experiment was performed to verify the effect of adding seminal plasma on post-thaw sperm functions. To determine these effects after cryopreservation, frozen-thawed semen from seven boars was examined after supplementation with different concentrations of pooled seminal plasma (0%, 10%, and 50%) at various times of incubation from 0 to 4 hours. Incubation caused a decrease in membrane integrity and an increase in acrosomal damage, with small changes in other parameters (P > 0.05). Although 10% seminal plasma showed few differences with 0% (ROS increase at 4 hours, P < 0.05), 50% seminal plasma caused important changes. Membrane fluidity increased considerably from the beginning of the experiment, and ROS and free thiols in the cell surface increased by 2 hours of incubation. By the end of the experiment, viability decreased and acrosomal damage increased in the 50% seminal plasma samples. The addition of 50% of seminal plasma seems to modify the physiology of thawed boar spermatozoa, possibly through membrane changes and ROS increase. Although some effects were detrimental, the stimulatory effect of 50% seminal plasma could favor the performance of post-thawed boar semen, as showed in the field (García JC, Domínguez JC, Peña FJ, Alegre B, Gonzalez R, Castro MJ, Habing GG, Kirkwood RN. Thawing boar semen in the presence of seminal plasma: effects on sperm quality and fertility. Anim Reprod Sci 2010;119:160-5).

  6. Crz1p regulates pH homeostasis in Candida glabrata by altering membrane lipid composition.

    PubMed

    Yan, Dongni; Lin, Xiaobao; Qi, Yanli; Liu, Hui; Chen, Xiulai; Liu, Liming; Chen, Jian

    2016-09-23

    The asexual facultative aerobic haploid yeast Candida glabrata is widely used in the industrial production of various organic acids. To elucidate the physiological function of the transcription factor CgCrz1p and its role in tolerance to acid stress we deleted or overexpressed the corresponding gene CgCRZ1 Deletion of CgCRZ1 resulted in a 60% decrease in dry cell weight (DCW) and a 50% drop in cell viability compared to the wild type at pH 2.0. Expression of lipid metabolism-associated genes was also significantly down-regulated. Consequently, the proportion of C18:1 fatty acids, ratio of unsaturated to saturated fatty acids, and ergosterol content decreased by 30%, 46%, and 30%, respectively. Additionally, membrane integrity, fluidity, and H(+)-ATPase activity were reduced by 45%, 9%, and 50%, respectively. In contrast, overexpression of CgCrz1p increased C18:1 and ergosterol content by 16% and 40%, respectively. Overexpression also enhanced membrane integrity, fluidity, and H(+)-ATPase activity by 31%, 6%, and 20%, respectively. Moreover, in the absence of pH buffering, DCW and pyruvate titer increased by 48% and 60%, respectively, compared to the wild type. Together, these results suggest that CgCrz1p regulates tolerance to acidic conditions by altering membrane lipid composition in C. glabrata IMPORTANCE: The present study provides an insight into the metabolism of Candida glabrata under acidic conditions, such as those encountered during industrial production of organic acids. We found that overexpression of the transcription factor CgCrz1p improved viability, biomass, and pyruvate yields at low pH. Analysis of plasma membrane lipid composition indicated that CgCrz1p might play an important role in its integrity and fluidity, and enhanced the pumping of protons in acidic environments. We propose that altering the structure of the cell membrane may provide a successful strategy for increasing C glabrata productivity at low pH.

  7. Lipid and fatty acid composition of Gluconobacter oxydans before and after intracytoplasmic membrane formation.

    PubMed Central

    Heefner, D L; Claus, G W

    1978-01-01

    Gluconobacter oxydans differentiates by forming quantities of intracytoplasmic membranes at the end of exponential growth, and this formation occurs concurrently with a 60% increase in cellular lipid. The present study was initiated to determine whether this newly synthesized lipid differed from that extracted before intracytoplasmic membrane synthesis. Undifferentiated exponential-phase cells were found to contain 30% phosphatidylcholine, 27.1% caridolipin, 25% phosphatidylethanolamine, 12.5% phosphatidylglycerol, 0.4% phosphatidic acid, 0.2% phosphatidylserine, and four additional unidentified lipids totaling less than 5%. The only change detected after formation of intracytoplasmic membranes was a slight decrease in phosphatidylethanolamine and a corresponding increase in phosphatidylcholine. An examination of lipid hydrolysates revealed 11 different fatty acids in the lipids from each cell type. Hexadecanoic acid and monounsaturated octadecenoic accounted for more than 75% of the total fatty acids for both cell types. Proportional changes were noted in all fatty acids except octadecenoate. Anteiso-pentadecanoate comprised less than 1% of the fatty acids from undifferentiated cells but more than 13% of the total fatty acids from cells containing intracytoplasmic membranes. These results suggest that anteiso-pentadecanoate formation closely parallels the formation of intracytoplasmic membranes. Increased concentrations of this fatty acid may contribute to the fluidity necessary for plasma membrane convolution during intracytoplasmic membrane development. PMID:649571

  8. Autonomous transmembrane segment S4 of the voltage sensor domain partitions into the lipid membrane.

    PubMed

    Tiriveedhi, Venkataswarup; Miller, Melissa; Butko, Peter; Li, Min

    2012-07-01

    The S4 transmembrane segment in voltage-gated ion channels, a highly basic alpha helix, responds to changes in membrane potential and induces channel opening. Earlier work by others indicates that the S4 segment interacts with lipids in plasma membrane, but its mechanism is unclear. Working with synthetic tryptophan-labeled S4 peptides, we characterized binding of autonomous S4 to lipid membranes. The binding free energy (5.2 +/- 0.2 kcal/mol) of the peptide-lipid interaction was estimated from the apparent dissociation constants, determined from the changes in anisotropy of tryptophan fluorescence induced by addition of lipid vesicles with 30 mol% phosphatidylglycerol. The results are in good agreement with the prediction based on the Wimley-White hydrophobicity scale for interfacial (IF) binding of an alpha-helical peptide to the lipid bilayer (6.98 kcal/mol). High salt inhibited the interaction, thus indicating that the peptide/membrane interaction has both electrostatic and non-electrostatic components. Furthermore, the synthetic S4 corresponding to the Shaker potassium channel was found to spontaneously penetrate into the negatively charged lipid membrane to a depth of about 9 A. Our results revealed important biophysical parameters that influence the interaction of S4 with the membrane: they include fluidity, surface charge, and surface pressure of the membrane, and the at helicity and regular spacing of basic amino-acid residues in the S4 sequence.

  9. Structure-dependent interactions of polyphenols with a biomimetic membrane system.

    PubMed

    Phan, Huong T T; Yoda, Tsuyoshi; Chahal, Bindu; Morita, Masamune; Takagi, Masahiro; Vestergaard, Mun'delanji C

    2014-10-01

    Polyphenols are naturally-occurring compounds, reported to be biologically active, and through their interactions with cell membranes. Although association of the polyphenols with the bilayer has been reported, the detailed mechanism of interaction is not yet well elucidated. We report on spatio-temporal real-time membrane dynamics observed in the presence of polyphenols. Two distinct membrane dynamics, corresponding to the two classes of polyphenols used, were observed. Flavonoids (epi-gallocatechin-3-gallate, gallocatechin, theaflavin and theaflavin-3-gallate) caused lipid membrane aggregation and rigidification. As simple structural modification through opening of the aromatic C-ring into an olefin bond, present in trans-stilbenes (resveratrol and picead), completely changed the membrane properties, increasing fluidity and inducing fluctuation. There were differences in the membrane transformations within the same class of polyphenols. Structure-dependent classification of membrane dynamics may contribute to a better understanding of the physicochemical mechanism involved in the bioactivity of polyphenols. In general, an increase in the number of hydrophilic side chains (galloyl, hydroxyl, glucoside, gallate) increased the reactivity of the polyphenols. Most notable was the difference observed through a simple addition of the gallate group. Unraveling the importance of these polyphenols, at a functional group level further opens the key to tailored design of bioactive compounds as potential drug candidates.

  10. Modification of plasma membrane organization in tobacco cells elicited by cryptogein.

    PubMed

    Gerbeau-Pissot, Patricia; Der, Christophe; Thomas, Dominique; Anca, Iulia-Andra; Grosjean, Kevin; Roche, Yann; Perrier-Cornet, Jean-Marie; Mongrand, Sébastien; Simon-Plas, Françoise

    2014-01-01

    Lipid mixtures within artificial membranes undergo a separation into liquid-disordered and liquid-ordered phases. However, the existence of this segregation into microscopic liquid-ordered phases has been difficult to prove in living cells, and the precise organization of the plasma membrane into such phases has not been elucidated in plant cells. We developed a multispectral confocal microscopy approach to generate ratiometric images of the plasma membrane surface of Bright Yellow 2 tobacco (Nicotiana tabacum) suspension cells labeled with an environment sensitive fluorescent probe. This allowed the in vivo characterization of the global level of order of this membrane, by which we could demonstrate that an increase in its proportion of ordered phases transiently occurred in the early steps of the signaling triggered by cryptogein and flagellin, two elicitors of plant defense reactions. The use of fluorescence recovery after photobleaching revealed an increase in plasma membrane fluidity induced by cryptogein, but not by flagellin. Moreover, we characterized the spatial distribution of liquid-ordered phases on the membrane of living plant cells and monitored their variations induced by cryptogein elicitation. We analyze these results in the context of plant defense signaling, discuss their meaning within the framework of the "membrane raft" hypothesis, and propose a new mechanism of signaling platform formation in response to elicitor treatment.

  11. Molecular dynamics study of lipid bilayers modeling the plasma membranes of mouse hepatocytes and hepatomas

    NASA Astrophysics Data System (ADS)

    Andoh, Yoshimichi; Aoki, Noriyuki; Okazaki, Susumu

    2016-02-01

    Molecular dynamics (MD) calculations of lipid bilayers modeling the plasma membranes of normal mouse hepatocytes and hepatomas in water have been performed under physiological isothermal-isobaric conditions (310.15 K and 1 atm). The changes in the membrane properties induced by hepatic canceration were investigated and were compared with previous MD calculations included in our previous study of the changes in membrane properties induced by murine thymic canceration. The calculated model membranes for normal hepatocytes and hepatomas comprised 23 and 24 kinds of lipids, respectively. These included phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, sphingomyelin, lysophospholipids, and cholesterol. We referred to previously published experimental values for the mole fraction of the lipids adopted in the present calculations. The calculated structural and dynamic properties of the membranes such as lateral structure, order parameters, lateral self-diffusion constants, and rotational correlation times all showed that hepatic canceration causes plasma membranes to become more ordered laterally and less fluid. Interestingly, this finding contrasts with the less ordered structure and increased fluidity of plasma membranes induced by thymic canceration observed in our previous MD study.

  12. Alcohols produce reversible and irreversible acceleration of phospholipid flip-flop in the human erythrocyte membrane.

    PubMed

    Schwichtenhövel, C; Deuticke, B; Haest, C W

    1992-10-19

    The slow, non-mediated transmembrane movement of the lipid probes lysophosphatidylcholine, NBD-phosphatidylcholine and NBD-phosphatidylserine in human erythrocytes becomes highly enhanced in the presence of 1-alkanols (C2-C8) and 1,2-alkane diols (C4-C8). Above a threshold concentration characteristic for each alcohol, flip rates increase exponentially with the alcohol concentration. The equieffective concentrations of the alcohols decrease about 3-fold per methylene added. All 1-alkanols studied are equieffective at comparable calculated membrane concentrations. This is also observed or the 1,2-alkane diols, albeit at a 5-fold lower membrane concentration. At low alcohol concentrations, flip enhancement is reversible to a major extent upon removal of the alcohol. In contrast, a residual irreversible flip acceleration is observed following removal of the alcohol after a treatment at higher concentrations. The threshold concentrations to produce irreversible flip acceleration by 1-alkanols and 1,2-alkane diols are 1.5- and 3-fold higher than those for flip acceleration in the presence of the corresponding alcohols. A causal role in reversible flip-acceleration of a global increase of membrane fluidity or membrane polarity seems to be unlikely. Alcohols may act by increasing the probability of formation of transient structural defects in the hydrophobic barrier that already occur in the native membrane. Membrane defects responsible for irreversible flip-acceleration may result from alterations of membrane skeletal proteins by alcohols.

  13. Autonomous Transmembrane Segment S4 of the Voltage Sensor Domain Partitions into the Lipid Membrane

    PubMed Central

    Tiriveedhi, Venkataswarup; Miller, Melissa; Butko, Peter; Li, Min

    2012-01-01

    The S4 transmembrane segment in voltage-gated ion channels, a highly basic α helix, responds to changes in membrane potential and induces channel opening. Earlier work by others indicates that the S4 segment interacts with lipids in plasma membrane, but its mechanism is unclear. Working with synthetic tryptophan-labeled S4 peptides, we characterized binding of autonomous S4 to lipid membranes. The binding free energy (5.2 ± 0.2 kcal/mol) of the peptide-lipid interaction was estimated from the apparent dissociation constants, determined from the changes in anisotropy of tryptophan fluorescence induced by addition of lipid vesicles with 30 mol% phosphatidylglycerol. The results are in good agreement with the prediction based on the Wimley-White hydrophobicity scale for interfacial (IF) binding of an alpha-helical peptide to the lipid bilayer (6.98 kcal/mol). High salt inhibited the interaction, thus indicating that the peptide/membrane interaction has both electrostatic and non-electrostatic components. Furthermore, the synthetic S4 corresponding to the Shaker potassium channel was found to spontaneously penetrate into the negatively charged lipid membrane to a depth of about 9 Å. Our results revealed important biophysical parameters that influence the interaction of S4 with the membrane: they include fluidity, surface charge, and surface pressure of the membrane, and the α helicity and regular spacing of basic amino-acid residues in the S4 sequence. PMID:22465069

  14. Assessment of the convergence of molecular dynamics simulations of lipopolysaccharide membranes

    SciTech Connect

    Soares, Thereza A.; Straatsma, TP

    2008-03-01

    The outer membrane of Gram-negative bacteria is composed of a phospholipid inner leaflet and a lipopolysaccharide outer leaflet. The chemical structure of lipopolysaccharide confers an asymmetric character to outer membranes that has been shown to play an important role in the in the electrical properties of porins, low permeability and intrinsic antibiotic resistance of Gram-negative bacteria. In the present work, atomistic molecular dynamics simulations of two different configurations of the outer membrane of Pseudomonas aeruginosa under periodic boundary conditions were carried out in order to i) validate model-derived properties against the available experimental data, ii) identify the properties whose dynamics can be sampled on nanosecond timescales, and iii) evaluate the dependence of the convergence of structural and dynamical properties on the initial configuration of the system, within the chosen force field and simulation conditions. Because the relaxation times associated with the motions of individual LPS monomers in outer membranes is very slow, the two initial configurations do not converge to a common ensemble of configuration on the nanosecond time scale. However, a number of properties of the outer membrane that will significantly impact the structural and internal dynamics of transmembrane proteins, most notably the electrostatic potential and molecular density, do converge within the simulated time scale. For these properties, a good agreement with the available experimental data was found. Such molecular model, capable of accounting for the high asymmetry and low fluidity characteristics of outer membranes, will certainly benefit future atomistic simulations of outer membrane proteins.

  15. Membrane magic

    SciTech Connect

    Buecker, B.

    2005-09-01

    The Kansas Power and Light Co.'s La Cyne generating station has found success with membrane filtration water pretreatment technology. The article recounts the process followed in late 2004 to install a Pall Aria 4 microfilter in Unit 1 makeup water system at the plant to produce cleaner water for reverse osmosis feed. 2 figs., 2 photos.

  16. Rapid intracellular motility and dynamic membrane events in an Antarctic foraminifer.

    PubMed

    Bowser, S S; DeLaca, T E

    1985-10-01

    Some properties of cytoplasmic transport in a cold-adapted (Antarctic) organism are reported for the first time. Phase-contrast light microscopy of Astrammina rara, an arenaceous foraminiferan protozoan, reveals that the saltatory transport of cytoplasmic granules in reticulopods occurs bidirectionally and at rates up to 7.5-micron/s. Extracellularly attached latex microspheres are rapidly translocated on the reticulopodial surface, thus demonstrating membrane fluidity at low (-1.8 degrees C) ambient temperatures. Rapid extension/withdrawal and branching/fusing of pseudopodia further illustrate dynamic plasma membrane activity at subzero temperatures. Immunofluorescence microscopy with an antibody monospecific for tubulin shows that these pseudopods contain microtubules. The motility of this cold-adapted foraminifer therefore appears fully comparable to the motility of allogromiid foraminifers from temperate waters.

  17. Membrane permeability transition and dysfunction of rice mitochondria effected by Er(III).