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61.
Yann Roche 《Thermochimica Acta》2006,447(1):81-88
Differential scanning calorimetry and Raman spectroscopy have been used to examine the effects of ubiquinones (UQn) on the thermotropic phase behavior of dipalmitoylphosphatidylcholine (DPPC) in multilamellar vesicles, for UQ/DPPC molar ratios ranging from 0.01 to 0.1. The influence of the side chain length has been investigated by comparing the effect of a series of UQ with 2 (UQ2), 4 (UQ4), 6 (UQ6) and 10 isoprene units (UQ10).In the presence of increasing amount of UQ2 or UQ4, concomitant shift of the gel to liquid crystalline phase transition towards lower temperatures and vanishing of the pretransition are observed. Short-chain ubiquinones are thus inserted parallel to phospholipid chains, their benzoquinone ring being close to the DPPC polar headgroups. In addition, broadening and skewing of the main transition peak support the fact that UQ2 and UQ4 are laterally self-organized in highly concentrated regions located at the boundary of lipid domains. The lipid thermotropic behavior is not affected by the presence of other analogues of the series, UQ6 and UQ10. They remain homogeneously dispersed within the midplane of the phospholipid bilayer. Such a chain length dependence on the location and the organization of ubiquinones analogues may be correlated with their biological activities in biomembranes. 相似文献
62.
Gautam Adhikary Sucheta Chandra Rita Sikdar Parimal C. Sen 《Colloids and surfaces. B, Biointerfaces》1995,4(6)
The phase behaviour ofl-α-phosphatidylcholine liposomes has been studied as a function of temperature, pH, ionic strength, etc., in the presence and absence of chlorpromazine by a polarization method using 1,6-diphenyl-1,3,5-hexatriene as a fluorescence probe. The gel crystalline to liquid crystalline (Tc), liquid crystalline to cubic (TII), and cubic to hexagonal (HII) transition temperatures in multilayer liposomes have been detected, and are found to be affected by chlorpromazine under different experimental conditions. 相似文献
63.
Taewon HwangTae-Joon Park Won-Gun KohIn Woo Cheong Sung-Wook Choi Jung Hyun Kim 《Colloids and surfaces. A, Physicochemical and engineering aspects》2011,392(1):250-255
Nano-scale liposomes were successfully produced using a Shirasu porous glass (SPG) membrane emulsification technique. Primary liposomes prepared by a film-hydration method were treated using SPG membranes with different pore sizes (2.0, 1.0, 0.7, 0.5, and 0.2 μm) for control over the liposome size. The liposome sizes were evaluated using a dynamic light scattering method and their morphologies were observed by optical microscopy and transmission electron microscopy. As the passage number of liposomes through SPG membrane increased, the size and its distribution of the liposomes gradually decreased. A smaller pore size of the SPG membrane and a higher applied pressure resulted in liposomes with a smaller size. After the preparation of nano-scale liposomes containing ammonium sulfate (AS), doxorubicin (DOX) was encapsulated in the liposomes by a remote loading method, where AS served as a precipitant for DOX. The encapsulation efficiency of the DOX was maximized up to 94% when the concentrations of AS and DOX were 250 and 0.045 mM, respectively. We have obtained the release profiles of the liposomes with different sizes. As shown below, liposomes with smaller size exhibited a faster release profile of drug due to the large surface area. These nano-scale liposomes encapsulating an anti-cancer drug can potentially be employed as drug delivery vehicles for intravenous injection. 相似文献
64.
Ioffe VM Gorbenko GP Tatarets AL Patsenker LD Terpechnig EA 《Journal of fluorescence》2006,16(4):547-554
The applicability of newly synthesized squarylium dye Sq to probing the changes in physical characteristics of lipid bilayer on the formation of protein-lipid complexes has been evaluated. Lipid vesicles composed of zwitterionic phospholipid phosphatidylcholine (PC) and its mixtures with positively charged detergent cetyltrimethylammonium bromide (CTAB), anionic phospholipid cardiolipin (CL), and cholesterol (Chol) were employed as lipid component of model membrane systems while protein constituent was represented by lysozyme (Lz). Fluorescence intensity of Sq was found to decrease on Lz association with lipid bilayer. This effect was observed in all kinds of model systems suggesting that Sq is sensitive to modification of lipid bilayer physical properties on hydrophobic protein-lipid interactions. It was found that Sq spectral response to variations in Chol content depends on relative contributions of electrostatic and hydrophobic components of Lz-membrane binding. 相似文献
65.
M. Szögyi T. Cserháti J. Szejtli 《Journal of inclusion phenomena and macrocyclic chemistry》1987,5(4):433-437
Nonylphenyl-ethyleneoxide polymers containing 5, 9 and 30 ethyleneoxide groups per molecule build into the hydrophobic fatty acid chains of the cell membrane phospholipid dipalmitoyl-phosphatidylcholine (DPPC) resulting in a decreased main transition temperature, a decreased enthalpy of the main transition and in enhanced potassium permeability of DPPC liposomes. The -, - and -cyclodextrins form inclusion complexes with the tenzides lowering their free concentration. The complex formation lessens or sometimes totally prevents the membrane damaging effect of tensides. The effectivity order of cyclodextrins is CD>CD>CD.Presented at the Fourth International Symposium on Inclusion Phenomena and the Third International Symposium on Cyclodextrins, Lancaster, U.K. 20–25 July 1986. 相似文献
66.
Ioffe VM Gorbenko GP Kinnunen PK Tatarets AL Kolosova OS Patsenker LD Terpetschnig EA 《Journal of fluorescence》2007,17(1):65-72
The applicability of the two newly commercial available squaraine labels Square-670-NHS and Seta-635-NHS to exploring protein-lipid
interactions has been evaluated. The labels were conjugated to lysozyme (Lz) (squaraine-lysozyme conjugates below referred
to as Square-670-Lz and Seta-635-Lz), a structurally well-characterized small globular protein displaying the ability to interact
both, electrostatically and hydrophobically with lipids. The lipid component of the model systems was represented by lipid
vesicles composed of zwitterionic lipids egg yolk phosphatidylcholine (PC) and 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine (SOPC), and their mixtures with anionic lipids either beef heart cardiolipin (CL) or 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol (POPG), respectively. Fluorescence intensity of Square-670-Lz was found to decrease upon association
with lipid bilayer, while the fluorescence intensity of Seta-635-Lz displayed more complex behavior depending on lipid-to-protein
molar ratio. Covalent coupling of squaraine labels to lysozyme exerts different influence on the properties of dye-protein
conjugate. It was suggested that Square-670-NHS covalent attachment to Lz molecule enhances protein propensity for self-association,
while squaraine label Seta-635-NHS is sensitive to different modes of lysozyme-lipid interactions—within the L:P range 6–11,
when hydrophobic protein-lipid interactions are predominant, an aggregation of membrane-bound protein molecules takes place,
thereby decreasing the fluorescence intensity of Seta-635-Lz. At higher L:P values (from 22 to 148) when electrostatic interactions
are enhanced fluorescence intensity of Seta-635-Lz increases with increasing lipid concentrations. 相似文献
67.
The interaction of dextran sulfate (DS) with dimyristoylphosphatidylcholine (DMPC) large unilamellar vesicles was investigated.
DS of different molecular weights (1, 8, 40 and 500 kDa) and divalent cations (Ca2+, Mg2+ and Mn2+) and the trivalent cation La3+ were used in the experiments. Binding of DS was studied by use of the microelectrophoresis and monolayer technique. Binding
depends strongly on cation and NaCl concentrations in the medium and does not occur in the absence of multivalent cations.
Binding is modulated by the molecular weight of the polymers; DS with lower molecular weights lead to less negative zeta potentials
at identical concentrations. A comparable monomer of DS, glucose-6-sulfate, does not change the zeta potential of DMPC vesicles.
Monolayer experiments revealed a decrease in surface pressure after addition of multivalent cations and DS, indicating a stronger
interaction of the cation–polymer complex with the phosphatidylcholine headgroups than its penetration into the phospholipid
(PL) bilayer. The cation-mediated binding of DS to the vesicles leads to aggregation of the vesicles. The tendency to promote
aggregation of DMPC vesicles is La3+>Ca2+>Mn2+≥ Mg2+. The aggregated vesicles show a stacklike arrangement of the bilayers as shown by freeze-fracture electron microscopy. The
strong aggregation is accompanied by lipid mixing measured by the 1,4-nitrobenzo-2-oxa-1,3-diazole–phosphatidylethanolamine
(PE)/lissamine rhodamine B sulfonyl-PE assay. At low ionic strength substantial lipid mixing can be observed in the previously
mentioned order of the cations. This lipid mixing is accompanied by an increase in the permeability of the vesicles as revealed
by the 1-aminonaphthalene-3,6,8-trisulfonic acid/p-xylenebis (pyridiium bromide) assay. The extent of leakage is determined by the cation used and the DS molecular weight.
These interaction processes between the opposing bilayers are connected with a decrease in the water content in the gap between
the opposing PL bilayers. As a measure for the change of the polar properties of the vesicle surface the shift of the emission
wavelength of the fluorescent probe dansylphosphatidylethanolamine was measured. The effectiveness of divalent/trivalent cations
to decrease the surface dielectric constant of DMPC vesicles also followed the sequence of ions as found for binding, PL mixing
and leakage. The results are discussed in terms of the changed hydration at the bilayer surface induced by DS in the presence
of multivalent ions.
Received: 16 December 1998/Accepted: 17 December 1999 相似文献
68.
Kaname Hashizaki Chika Itoh Hideki Sakai Shoko Yokoyama Hiroyuki Taguchi Yoshihiro Saito Naotake Ogawa Masahiko Abe 《Colloids and surfaces. B, Biointerfaces》2000,17(4):305-282
The differential scanning calorimetry (DSC) and the freeze-fracture electron microscopy of dipalmitoyl phosphatidylcholine (DPPC) liposomes containing distearoyl-N-monomethoxy poly(ethylene glycol)-succinyl-phosphatidylethanolamines (PEG-DSPE) were carried out. The DSC peak of DPPC liposomes containing PEG-DSPE had a shoulder. The main phase transition temperature of DPPC bilayer membranes containing PEG-DSPE whose molecular weight of PEG is less than 3000 was slightly shifted to a higher temperature, while that containing PEG-DSPE whose molecular weight of PEG is more than 5000 was slightly shifted to a lower temperature. The electron micrographs of freeze-fracture replicas of DPPC liposomes containing PEG-DSPE quenched from 37±2°C exhibited banded and planar textures, suggesting the lateral phase separation in the bilayer membranes. 相似文献
69.
《Tetrahedron》2019,75(33):4444-4450
Novel 3,7-bis(dialkylaminoacetyl)-1,5-dimethyl-3,7-diazabicyclo[3.3.1]nonanes were synthesized, which can undergo conformational reorganization under the change of solvent polarity, protonation (the change of pH) or complexation with LaCl3. These compounds are capable of being embedded into the liposomal membranes and can serve as molecular switches for the development of stimulus-sensitive liposomal containers. 相似文献
70.
Liposomes composed of dipalmitoylphosphatidylcholine and dipalmitoylphosphatidylglycerol were analyzed by asymmetrical flow field-flow fractionation coupled with multi-angle laser light scattering. In addition to evaluation of fractionation conditions (flow conditions, sample mass, carrier liquid), radiolabeled drug-loaded liposomes were used to determine the liposome recovery and a potential loss of incorporated drug during fractionation. Neither sample concentration nor the cross-flow gradient distinctly affected the size results but at very low sample concentration (injected mass 5 μg) the fraction of larger vesicles was underestimated. Imbalance in the osmolality between the inner and outer aqueous phase resulted in liposome swelling after dilution in hypoosmotic carrier liquids. In contrast, liposome shrinking under hyperosmotic conditions was barely visible. The liposomes themselves eluted completely (lipid recoveries were close to 100%) but there was a loss of incorporated drugs during separation with a strong dependence on the octanol-water partition coefficient of the drug. Whereas corticosterone (partition coefficient ~2) was washed out more or less completely (recovery about 2%), loss of temoporfin (partition coefficient ~9) was only minor (recovery about 80%). All fractionations were well repeatable under the experimental conditions applied in the present study. 相似文献