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1.
The interaction of four long-chain nicotinates, compounds that are of interest as potential chemopreventive agents, with dipalmitoylphosphatidylcholine (DPPC) was investigated in monolayers at the air-water interface and in fully hydrated bilayers. For the monolayer studies, the compression isotherms of mixtures of the respective nicotinate with DPPC were recorded at various compositions on a hydrochloric acid subphase (pH 1.9-2.1, 37 +/- 2 degrees C). The headgroup of the nicotinates (24-29 A2/molecule) is larger than that of the hydrophobic tail (20 A2/molecule). The pure nicotinates exhibit a temperature- and chain length-dependent transition from an expanded to a condensed phase. Analysis of the concentration dependence of the average molecular area at constant film pressure and the concentration dependence of the breakpoint of the phase transition from the expanded to the condensed state suggests that all four DPPC-nicotinate mixtures are partially miscible at the air-water interface. Although a complex phase behavior with several phase transitions was observed, differential scanning calorimetry studies of the four mixtures are also indicative of the partial miscibility of DPPC and the respective nicotinate. Overall, the complex phase behavior most likely results from the head-tail mismatch of the nicotinates and the geometric packing constraints in the two-component lipid bilayer. 相似文献
2.
Liposomes are an important tool and have gained much attention for their promise as an effective means of delivering small therapeutic compounds to targeted sites. In an effort to establish an effective method to produce liposomes from the lipid, dipalmitoyl-phosphatidylcholine or DPPC, we have found important aspects that must be taken into consideration. Here, we used probe-tip sonication to prepare liposomes on a batch scale. During this process we uncovered interesting steps in their preparation that altered the thermodynamic properties and phase transitions of the resulting liposome mixtures. Using differential scanning calorimetry to assess this we found that increasing the sonication time had the most dramatic effect on our sample, producing almost an entirely separate phase transition relative to the main phase transition. This result is consistent with reports from the current literature. We also highlight a smaller transition, which we attribute to traces of unincorporated lipid that seems to gradually disappear as the total lipid concentration decreases. Overall, sonication is an effective means of producing liposomes, but we cannot assert this method is optimal in producing them with precise physical properties. Here we highlight the physical effects at play during this process. 相似文献
3.
Athanas I. Boyanov Boris G. Tenchov Rumiana D. Koynova Kamen S. Koumanov 《生物化学与生物物理学报:生物膜》1983,732(3):711-713
dl-Dipalmitoylphosphatidylcholine multilamellar vesicle suspensions were examined by the method of differential scanning calorimetry. A lack of the subtransition at 18°C was established. Such a subtransition is characteristic for l-dipalmitoylphosphatidylcholine suspensions. This lack is supposed to be the result of the impossibility of the racemic phospholipid mixture to form the low-temperature crystal structure Lc. 相似文献
4.
Wenqing Wang Xiangrong Sheng Hongshun Yang Zhizhong Zhuang Fenming Lou Zhaojia Chen 《Journal of biological physics》1995,20(1-4):247-252
The low temperature specific heat ofD-Valine andL-Valine has been measured by differential scanning calorimetry in the temperature region between 77–300K. It was found that an obvious lambda transition at 272±1K. X-ray diffraction crystallographic data showed that no crystal lattice changed C,H,N element analysis proved the high purity of the sample ofD andL-Valine. We propose that the shape of the jump forD-Valine is contributed by the specific heat of electron coupling. 相似文献
5.
Diana Bach Chana Vinkler Israel R. Miller S. Roy Caplan 《The Journal of membrane biology》1988,101(1):103-111
Summary The interaction of furosemide with different phospholipids was investigated. Its influence on the lipid structure was inferred from its effect on the phase transition properties of lipids and on the conductance of planar bilayer membranes. The thermotropic properties of dipalmitoyl phosphatidylcholine, phosphatidylethanolamine (natural), dipalmitoyl phosphatidylethanolamine, brain sphingomyelin, brain cerebrosides and phosphatidylserine in the presence and absence of furosemide were investigated by differential scanning calorimetry,. The modifying effect of furosemide seems to be strongest on phosphatidylethanolamine (natural) and sphingomyelin bilayers. The propensity of furosemide to decrease the electrical resistance of planar lipid membranes was also studied and it is shown that the drug facilitates the transport of ions. Partition coefficients of furosemide between lipid bilayers and water were measured.Abbreviations DSC
differential scanning calorimetry
- PLM
planar lipid membranes
- DPPC
dipalmitoyl phosphatidylcholine
- DMPC
dimyristoyl phosphatidylcholine
- PE
phosphatidyl ethanol 相似文献
6.
In the present study the phase behavior of multilamellar dispersions of 1-O-(1′-alkenyl)-2-oleoyl-glycerophosphoethanolamine (ethanolamine plasmalogen), 1-O-alkyl-2-oleoyl-glycerophosphoethanolamine and 1-acyl-2-oleoyl-glycerophosphoethanolamine was compared using differential scanning calorimetry (DSC) and 31P-NMR. The three compounds differed only in the type of bonding (vinyl ether, alkyl ether or acyl ester) linking the aliphatic moiety to position 1 of sn-glycerol.The gel to liquid-crystalline phase transition temperature as determined by DSC was lowest for ethanolamine plasmalogen (26°C) and was similar for the alkylacyl and diacyl analogs (29.5° and 30°C, respectively). Enthalpies of the G → L phase transition were not significantly different for the three phospholipids tested.Ethanolamine plasmalogen undergoes the lamellar to hexagonal phase transition at 30°C, the analogous alkylacyl-glycerophosphoethanolamine(alkylacyl-GPE) and diacyl-GPE at 53°C and 69°C, respectively. Thus, an alkenyl ether bond in position 1 of sn-glycerol, the structural characteristic of plasmalogens, effectively stabilizes the hexagonal HII arrangement of ethanolamine glycerophospholipids, while it has relatively little effect on destabilization of the lamellar gel state. 相似文献
7.
Muskotál A Király R Sebestyén A Gugolya Z Végh BM Vonderviszt F 《FEBS letters》2006,580(16):3916-3920
Premature polymerization of flagellin (FliC), the main component of flagellar filaments, is prevented by the FliS chaperone in the cytosol. Interaction of FliS with flagellin was characterized by isothermal titration calorimetry producing an association constant of 1.9x10(7) M-1 and a binding stoichiometry of 1:1. Experiments with truncated FliC fragments demonstrated that the C-terminal disordered region of flagellin is essential for FliS binding. As revealed by thermal unfolding experiments, FliS does not function as an antifolding factor keeping flagellin in a secretion-competent conformation. Instead, FliS binding facilitates the formation of alpha-helical secondary structure in the chaperone binding region of flagellin. 相似文献
8.
A. Manjon J.C. Garcia-Borron J.A. Lozano J.L. Iborra 《Chemistry and physics of lipids》1984,34(3):237-244
Bovine thyroid peroxidase (TPO), an enzyme requiring lipids for demonstrating catalytic activity, was incorporated in liposomes made of pure phospholipids. The enzyme did not show high differences in activity when bilayer thickness was changed, but dipalmitoyl phosphatidyl choline (DPPC) seemed to be more appropiate for activity. The perturbation caused on lipid fluidity by enzyme incorporation was studied by differential scanning calorimetry (DSC) and fluorescence polarization of the apolar probe 1,6-diphenyl-1,3,5-hexatriene (DPH). The complexes of TPO with dimyristoyl phosphatidyl choline (DMPC), DPPC, and distearoyl phosphatidyl choline (DSPC) bilayers showed transition temperatures (Tc) which were lower than the characteristic ones shown by liposomes with the respective phospholipids alone. The microsomal fraction from which TPO was extracted was in the fluid state at 37°C, the temperature at which thyroid peroxidase works ‘in vivo’. Since the effect of the protein in lowering the transition temperature of the phospholipids was so low, the contribution of phospholipids containing unsaturated fatty acids has to be essential for obtaining a fluid bilayer at body temperature. 相似文献
9.
Makoto Nishimoto Masaki Goto Shoji Kaneshina Issaku Ueda 《Chemistry and physics of lipids》2009,158(2):71-87
The effects of long-chain fatty acids (four saturated and two unsaturated fatty acids, one derivative) on phase transitions of dipalmitoylphosphatidylcholine (DPPC) bilayer membranes were examined in the low concentration region, and the results were compared with those for an inhalation anesthetic. The effects of all fatty acids on the pre- and main-transition temperatures of the DPPC bilayer membrane appeared in the concentration range of μM order while that of the anesthetic appeared in the mM order. The appearance modes of these ligand actions were significantly different from one another. The three differential partition coefficients of the ligands between two phases of the DPPC bilayer membrane were evaluated by applying the thermodynamic equation to the variation of the phase-transition temperatures. The DPPC bilayer membranes showed the different receptivity for the ligands; the saturated fatty acids had an affinity for gel phase whereas unsaturated fatty acids and an anesthetic had an affinity for liquid-crystalline phase to the contrary. In particular, the receptivity for the ligands in the gel phase markedly changed depending on kinds of ligands. The interaction modes between the DPPC and fatty acid molecules in the gel phase were considered from the hexagonal lattice model. The disappearance compositions of the pretransition by the fatty acids coincided with the compositions at which the membrane is all covered by the units in each of which two fatty acids molecules are regularly distributed in the hexagonal lattice in a different way, and the distribution depended on the chain length and existence of a double bond for the fatty acids. The interpretation did not hold for the case of the anesthetic at all, which proved that a number of anesthetic molecules act the surface region of the bilayer membrane nonspecifically. The present study clearly implies that DPPC bilayer membranes have high ability to recognize kinds of ligand molecules and can discriminate among them with specific interaction by the membrane states. 相似文献
10.
Summary Differential scanning calorimetry of multilamellar liposomes, interacting with the optical probe Merocyanine 540, yields quantitative information about perturbances of the bilayer structure induced by this dye. At low dye: lipid ratios, the dye perturbs primarily its own microenvironment, which is laterally separated from the unmodified lipid domain and exhibits modified thermotropic properties. A further increase in the dye concentration results in a perturbance of the whole lipid bilayer. The degree of perturbance is sensitive to structural modifications in the head-group region of the lipids. It is concluded that Merocyanine 540 reports in every case, even at infinite dilution, on localized events originating from a perturbed microenvironment.An abstract of this paper was presented at the XI Congress of Biochemistry, Toronto, in July 1979. 相似文献
11.
V Saroglou S Hatziantoniou M Smyrniotakis I Kyrikou T Mavromoustakos A Zompra V Magafa P Cordopatis C Demetzos 《Journal of peptide science》2006,12(1):43-50
A novel liposomal formulation was developed for the encapsulation of the oligopeptide leuprolide (GlpHisTrpSerTyr-D-LeuLeuArgProNHEt), a potent analogue of gonadotropin releasing hormone used in the treatment of advanced prostate cancer, endometriosis and precocious puberty. Leuprolide was synthesized using solid phase methodology on a {3-[(ethyl-Fmoc-amino)-methyl]-1-indol-1-yl}-acetyl AM resin and Fmoc/tBu chemistry. The new liposomal formulation, called 'liposomes in liposomes' is composed of egg phosphatidylcholine:dipalmitoylphosphatidylglycerol in a molar ratio of 98.91:1.09 (internal liposomes) and egg phosphatidylcholine:dipalmitoylphosphatidylglycerol:cholesterol in a molar ratio of 68.71:0.76:30.53 (external liposomes). It offers high encapsulation efficiency (73.8% for leuprolide); it can provide new delivery characteristics and it may have possible advantages in future applications regarding the encapsulation and delivery of bioactive peptides to target tissues. Furthermore, the physicochemical characteristics (size distribution and zeta-potential) of the liposomal formulations and the thermal effects on leuprolide in model lipidic bilayers composed of dipalmitoylphosphatidylcholine were studied using differential scanning calorimetry. Finally, the dynamic effects of leuprolide in an egg phosphatidylcholine/cholesterol system were examined using solid state 13C MAS NMR spectroscopy. 相似文献
12.
1 Introduction Serumalbuminproteinsareamongthemosthighlystudiedandappliedinbiochemistry[1~ 4].Albuministhemostabundantproteininbloodplasmaandoneofitsmainfunctionsisbasedonauniqueabilitytobindnumerousendogenousandexogenouscompounds.Duetoitsligandbindingpropertiesalbuminservesasacirculatingdepotofsomemetabolites.Thisdepoteffectisoftenmadeuseofindrugtherapy. Humanserumalbumin(HSA)isasinglepeptidechainconsistingof 5 85aminoacids( 6 6 5ku)asdeterminedbyaminoacidsequencestudies[5] andasde… 相似文献
13.
B. A. Logan T. J. Anchordoquy R. K. Monson R. S. Pan 《Plant biology (Stuttgart, Germany)》1999,1(6):602-606
Abstract: Isoprene is emitted from the leaves of some plants. It was recently reported that exogenous isoprene delays the onset of leaf damage during controlled increases in leaf temperature (Singsaas et al. Plant Physiology 115: 1413–1420 [1997[17 ). Thylakoid membranes are presumed to be the site of action based upon isoprene's hydrophobicity, production in chloroplasts, and effect upon chlorophyll fluorescence at high temperatures. In an attempt to discern the mechanistic basis for isoprene's thermoprotective role, we studied the effect of exogenous isoprene on the peroxidation, permeability, and stability of spinach thylakoids and phosphatidylcholine liposomes. Isoprene, supplied at either 18 or 21 μ1 L1 , had no effect upon the rate of liposome peroxidation in the presence of a hydroxyl radical-generating system. Isoprene also did not affect liposome peroxidation at high temperatures. Neither the proton permeability of thylakoids nor the leakage of a fluorescent probe from liposomes was influenced by exogenous isoprene, when measured at several temperatures. Isoprene did not affect the stability of thylakoid membrane proteins during a temperature increase, as shown by differential scanning calorimetry. Therefore, despite the use of a variety of techniques to investigate fundamental membrane parameters, we were unable to demonstrate an effect of isoprene. 相似文献
14.
In this work we have performed a comparative study on the effect of antineoplastic ether lipid-edelfosine (ED), its natural analogs — Platelet Activating Factor (PAF) and its precursor (lyso-PAF), both lacking anticancer properties, on cholesterol/phosphatidylcholine (Chol/PC) monolayers, serving as model membranes. Since all the above ether lipids are membrane active, it can be expected that their effect on membranes may differentiate their biological activity. Our investigations were aimed at studying potential relationship of the effect of ED, PAF and lyso-PAF on model membranes, differing in condensation. We have modified molecular packing of Chol/PC model systems either by increasing the level of sterol in the system or changing the structure of PC, while keeping the same sterol content. Additionally, we have performed a detailed comparison of the miscibility of ED, PAF and lyso-PAF with various membrane lipids. The collected data evidenced that all the investigated ether lipids influence Chol/PC films in the same way; however, in a different magnitude. Moreover, the interactions of ED, PAF and lyso-PAF with model membranes were the strongest at the highest level of sterol in the system. A thorough analysis of the obtained results has proved that the effect of the investigated ether lipids on membranes is not dependent on the condensation of the system, but it is strongly determined by the concentration of cholesterol. Since ED was found to interact with model membranes stronger than PAF and lyso-PAF, we have suggested that this fact may contribute to differences in cytotoxicity of these compounds. 相似文献
15.
Pfam family DUF1023 consists entirely of uncharacterized proteins generated by sequencing the genomes of Actinobacteria (Bateman A., et al., Nucleic Acids Res. 2004;32 Database issue:D138-141.) Utilizing sequence similarity detection methods, we infer homology between DUF1023 and alpha/beta hydrolases. DUF1023 proteins conserve the core secondary structures in alpha/beta hydrolase fold, and share similar catalytic machinery as that of alpha/beta hydrolases. We predict DUF1023 spatial structure and deduce that they function as hydrolases utilizing catalytic Ser-His-Asp triad with the serine as a nucleophile. 相似文献
16.
In the presence of either egg or bovine brain sphingomyelin, the spectral properties of glucagon undergo changes which are similar to those which occur in the presence of synthetic phosphatidylcholines. The fluorescence emission spectra are blue shifted about 10 nm in the presence of lipid and the peptide acquires an increased helical content, determined by circular dichroism. As with phosphatidylcholines, the changes in spectral properties do not occur above the phase transition temperature of the glucagon-lipid mixture. Freeze-fracture electron microscopy indicates that glucagon forms an ellipsoidal complex with bovine brain sphingomyelin, similar to the glucagon-dimyristoylphosphatidylcholine complex. However, the sphingomyelin complexes break down to vesicular structures both above and below the region of the phase transition. These results indicate that the dissociation of glucagon from the lipid at higher temperatures results from changes in the phase of the lipid rather than from a thermal denaturation of glucagon. The effect of glucagon on the phase transition behaviour of palmitoyl sphingosine phosphorylcholine was measured by differential scanning calorimetry. The major effect of glucagon on both this lipid and on dimyristoylphosphatidylcholine is to broaden the phase transition and to shift it to higher temperatures. Similar results are obtained for the effects of glucagon on an equimolar mixture of dimyristoylphosphatidylcholine and palmitoyl sphingosine phosphorylcholine. Glucagon is able to solubilize mixtures of bovine brain sphingomyelin with either dimyristoylphosphatidylcholine or egg lecithin. The lipid composition of the solubilized material is similar to that of the starting lipid film. These results together with those from the differential scanning calorimetry on the synthetic mixtures indicate that glucagon can bind to sphingomyelin-phosphatidylcholine mixtures and that it does not induce extensive lateral phase separation between the components. The maximal stability of the glucagon-lipid complex at the phase transition of the lipids indicates that the glucagon-lipid interaction is highly dependent on the structural organization of the lipid. 相似文献
17.
The purpose of this research was to study whether the bioavailability of lovastatin could be improved by administering lovastatin
solid lipid nanoparticles (SLN) duodenally to rats. Lovastatin SLN were developed using triglycerides by hot homogenization
followed by ultrasonication. Particle size and zeta potential were measured by photon correlation spectroscopy. The solid
state of the drug in the SLN and lipid modification were characterized. Bioavailability studies were conducted in male Wistar
rats after intraduodenal administration of lovastatin suspension and SLN. Stable lovastatin SLN having a mean size range of
60 to 119 nm and a zeta potential range of −16 to −21 mV were developed. More than 99% of the lovastatin was entrapped in
the SLN. Lovastatin was dispersed in an amorphous state, and triglycerides were in {ieE162-1} form in the SLN. In vitro stability
studies showed the slow release and stability of lovastatin SLN. The relative bioavailabilities of lovastatin and lovastatin
hydroxy acid of SLN were increased by ∼173% and 324%, respectively, compared with the reference lovastatin suspension.
Published: March 23, 2007 相似文献
18.
D. V. Shubenok Y. I. Tsybovsky O. A. Stremovskiy S. M. Deyev S. P. Martsev 《Biochemistry. Biokhimii?a》2009,74(6):672-680
A chimeric protein, VH-barnase, was obtained by fusing the VH domain of anti-human ferritin monoclonal antibody F11 to barnase, a bacterial RNase from Bacillus amyloliquefaciens. After refolding from inclusion bodies, the fusion protein formed insoluble aggregates. Off-pathway aggregation was significantly reduced by adding either purified GroEL/GroES chaperones or arginine, with 10–12-fold increase in the yield of the soluble protein. The final protein conformation was identical by calorimetric criteria and CD and fluorescence spectroscopy to that obtained without additives, thus suggesting that VH-barnase structure does not depend on folding conditions. Folding of VH-barnase resulted in a single calorimetrically revealed folding unit, the so-called “calorimetric domain”, with conformation consistent with a molten globule that possessed well-defined secondary structure and compact tertiary conformation with partial exposure of hydrophobic patches and low thermodynamic stability. The unique feature of VH-barnase is that, despite the partially unfolded conformation and coupling into a single “calorimetric domain”, this immunofusion retained both the antigen-binding and RNase activities that belong to the two heterologous domains. 相似文献
19.
Natassa Pippa Maria Chountoulesi Aimilia Kyrili Anastasia Meristoudi Stergios Pispas 《Journal of liposome research》2016,26(3):211-220
This study is focused on chimeric advanced drug delivery nanosystems and specifically on pH-sensitive liposomes, combining lipids and pH-responsive amphiphilic block copolymers. Chimeric liposomes composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and two different forms of block copolymers, i.e. poly(n-butylacrylate)-b-poly(acrylic acid) (PnBA-b-PAA) at 70 and 85% content of PAA at six different molar ratios, each form respectively. PAA block exhibits pH-responsiveness, because of the regulative group of –COOH. –COOH is protonated under acidic pH (pKa ca. 4.2), while remains ionized under basic or neutral pH, leading to liposomes repulse and eventually stability. Lipid bilayers were prepared composed of DPPC and PnBA-b-PAA. Experiments were carried out using differential scanning calorimetry (DSC) in order to investigate their thermotropic properties. DSC indicated disappearance of pre-transition at all chimeric lipid bilayers and slight thermotropic changes of the main transition temperature. Chimeric liposomes have been prepared and their physicochemical characteristics have been explored by measuring the size, size distribution and ζ-potential, owned to the presence of pH-responsive polymer. At percentages containing medium to high amounts of the polymer, chimeric liposomes were found to retain their size during the stability studies. These results were well correlated with those indicated in the DSC measurements of lipid bilayers incorporating polymers in order to explain their physicochemical behavior. The incorporation of the appropriate amount of these novel pH-responsive block copolymers affects thus the cooperativity, the liposomal stabilization and imparts pH-responsiveness. 相似文献
20.
Lee Tzong-Hsien Rivett Don Werkmeister Jerome Hewish Dean Aguilar Marie-Isabel 《International journal of peptide research and therapeutics》1999,6(5-6):371-380
Summary The interaction of melittin and a truncated analogue of melittin with an immobilised phosphatidylcholine monolayer has been
studied using dynamic elution techniques. The melittin analogue (21Q analogue) had five amino acids omitted from the C-terminal
region of melittin. The influence of temperature and methanol concentration on the binding affinity of the two peptides was
determined and compared to the binding behaviour of two control moleculesN-acetyltryptophanamide and diphenylalanine. Both peptides exhibited non-linear dependence of affinity on % methanol at different
temperatures, whileN-acetyltryptophanamide and diphenylalanine exhibited linear behaviour. In addition, both melittin and the 21Q analogue exhibited
significant band broadening under a range of experimental conditions, which was not evident forN-acetyltryptophanamide and diphenylalanine. As melittin is known to adopt a significant degree of α-helical conformation in
the presence of lipids, the results suggest that melittin and the 21Q analogue adopt different conformations and orientations
upon binding to the immobilised phosphatidylcholine surface. Overall, the results of this study demonstrate that the immobilised
lipid monolayer provides a powerful system to rapidly assess the affinity of peptides for different lipid surfaces. 相似文献