共查询到20条相似文献,搜索用时 31 毫秒
1.
Karli Lipinski Matthew J. McKay Fahmida Afrose Dr. Ashley N. Martfeld Prof. Roger E. Koeppe II Dr. Denise V. Greathouse 《Chembiochem : a European journal of chemical biology》2019,20(21):2784-2792
Membrane proteins are essential for many cell processes yet are more difficult to investigate than soluble proteins. Charged residues often contribute significantly to membrane protein function. Model peptides such as GWALP23 (acetyl-GGALW5LAL8LALALAL16ALW19LAGA-amide) can be used to characterize the influence of specific residues on transmembrane protein domains. We have substituted R8 and R16 in GWALP23 in place of L8 and L16, equidistant from the peptide center, and incorporated specific 2H-labeled alanine residues within the central sequence for detection by solid-state 2H NMR spectroscopy. The resulting pattern of [2H]Ala quadrupolar splitting (Δνq) magnitudes indicates the core helix for R8,16GWALP23 is significantly tilted to give a similar transmembrane orientation in thinner bilayers with either saturated C12:0 or C14:0 acyl chains (1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC) or 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)) or unsaturated C16:1 Δ9 cis acyl chains. In bilayers of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC; C18:1 Δ9 cis) multiple orientations are indicated, whereas in longer, unsaturated 1,2-dieicosenoyl-sn-glycero-3-phosphocholine (DEiPC; C20:1 Δ11 cis) bilayers, the R8,16GWALP23 helix adopts primarily a surface orientation. The inclusion of 10–20 mol % cholesterol in DOPC bilayers drives more of the R8,16GWALP23 helix population to the membrane surface, thereby allowing both charged arginines access to the interfacial lipid head groups. The results suggest that hydrophobic thickness and cholesterol content are more important than lipid saturation for the arginine peptide dynamics and helix orientation in lipid membranes. 相似文献
2.
Colantonio S Simpson JT Fisher RJ Yavlovich A Belanger JM Puri A Blumenthal R 《Lipids》2011,46(5):469-477
Since its introduction as an ionization technique in mass spectrometry, matrix-assisted laser desorption ionization (MALDI)
has been applied to a wide range of applications. Quantitative small molecule analysis by MALDI, however, is limited due to
the presence of intense signals from the matrix coupled with non-homogeneous surfaces. The surface used in nano-structured
laser desorption ionization (NALDI) eliminates the need for a matrix and the resulting interferences, and allows for quantitative
analysis of small molecules. This study was designed to analyze and quantitate phospholipid components of liposomes. Here
we have developed an assay to quantitate the DPPC and DC8,9PC in liposomes by NALDI following various treatments. To test our method we chose to analyze a liposome system composed of
DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) and DC8,9PC (1,2-bis(tricosa-10,12-diynoyl)-sn-glycero-3-phosphocholine), as DC8,9PC is known to undergo cross-linking upon treatment with UV (254 nm) and this reaction converts the monomer into a polymer.
First, calibration curves for pure lipids (DPPC and DC8,9PC) were created using DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine) as an internal standard. The calibration curve for both DPPC and DC8,9PC showed an R2 of 0.992, obtained using the intensity ratio of analyte and internal standard. Next, DPPC:DC8,9PC liposomes were treated with UV radiation (254 nm). Following this treatment, lipids were extracted from the liposomes and
analyzed. The analysis of the lipids before and after UV exposure confirmed a decrease in the signal of DC8,9PC of about 90%. In contrast, there was no reduction in DPPC signal. 相似文献
3.
Resolution of individual molecular species of human platelet 1,2-diradyl-sn-glycero-3-phosphocholines and 1,2-diradyl-sn-glycero-3-phosphoethanolamines by reverse phase high pressure liquid chromatography (HPLC) allowed a thorough analysis of
those phospholipids labeled with [3H]arachidonic acid. Approximately 54% and 16% of the total incorporated radiolabel was found in choline glycerophospholipids
and ethanolamine glycerophospholipids, respectively, with ca. 90% of this being found in the 1,2-diacyl molecular species.
Eighty percent of [3H]-arachidonic acid incorporated into 1-acyl-2-arachidonoyl-sn-glycero-3-phosphocholine in resting platelets was equally distributed between 1-palmitoyl-2-arachidonoyl and 2-stearoyl-2-arachidonoyl-sn-glycero-3-phosphocholine, while 70% of the radiolabel in 1-acyl-2-arachidonoyl-sn-glycero-3-phosphoethanolamine was found in 1-stearoyl-2-arachidonoyl-sn-glycero-3-phosphoethanolamine. Thrombin stimulation (5 U/ml for 5 min) resulted in deacylation of all 1-acyl-2-[3H]arachidonoyl molecular species of 1-acyl-2-arachidonoyl-sn-glycero-3-phosphocholine and 1-acyl-2-arachidonoyl-sn-glycero-3-ethanolamine. There was also a slight increase in 1-O-alkyl-2-[3H]arachidonoyl-sn-glycero-3-phosphocholine and a significant increase in 1-O-alk-1′-enyl-2-[3H]arachidonoyl-sn-glycero-3-phosphoethanolamine molecular species of over 300%. Thus, HPLC methodology indicates that arachidonoyl-containing
molecular species of phosphatidylcholine and phosphatidylethanolamine are the major source of arachidonic acid in thrombin-stimulated
human platelets, while certain ether phospholipid molecular species become enriched in arachidonate. 相似文献
4.
Etsuo Hasegawa Yoh-ichi Matsushita Kiyoshi Eshima Hiroyuki Ohno Eishun Tsuchida 《Polymer Bulletin》1986,15(5):397-403
Summary Polymerizable glycerophosphocholines containing one or two 2,4-hexadienyloxy groups at the terminal of the acyl chains were prepared. Those were 1-[11-(2,4-hexadienyloxy)undecanoyl]-2-0-alkyl-rac-glycero-3-phosphocholines 1, 1-acyl-2-[11-(2,4-hexadienyloxy)undecanoyl]-sn-glycero-3-phosphocholines 2 and 1,2-bis[11-(2,4-hexadienyloxy)undecanoyl]-sn-glycero-3-phosphocholine 3. Those having one hexadienyloxy group formed small unilamellar vesicles. One having two groups formed lipid bilayers, but not unilamellar vesicles. 1 and 2 could form stable microcapsules (polymerized vesicles) with the diameters ranging from 20 to 40 nm. 相似文献
5.
Interactions between the binary combination of dimethyltetradecylammoniopropanesulfonate (TPS) and l-α-phosphatidylcholine (PC), 1,2-didecanoyl-sn-glycero-3-phosphocholine, and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine in the aqueous bulk phase were evaluated with the help of pyrene fluorescence (l
1/l
3) measurements by studying the aggregation processes of TPS in pure water and in the presence of 7–36 μM of fixed concentrations
of each lipid. The fluorescence measurements showed that TPS monomers undergo two kinds of aggregation process, which were
identified by the three breaks. The first break, C1, and the second, C2, indicated the onset and completion of bilayer solubilization, respectively, on the incorporation of TPS monomers into the
bilayer assemblies, which led to bilayer solubilization in the form of mixed micelles. This process was not clearly visible
in the presence of PC, whereas some kinds of structure transitions were observed upon the incorporation of surfactant monomers.
The partition coefficient (K), which defines the degree of partitioning of surfactant monomers into the bilayers with respect
to the aqueous medium, was evaluated. A high K value of TPS-lipid aggregates indicated stronger interactions between surfactant and bilayer assemblies of lipid. The K values determined for the three phospholipids are close to each other, which indicates that K values do not depend on the hydrocarbon chain length of the phospholipid but of the surfactant used. 相似文献
6.
The potential for the synthesis of phosphatidylcholine by the bile canalicular membrane of the liver cell was assessed by
measuring the activity of a number of phospholipid synthesizing enzymes in isolated bile canalicular membrane fractions from
rat liver. The activity of these various enzymes was compared to that present in noncanalicular liver cell plasma membranes
and in microsomes. The CDP-choline: 1,2-diacyl-sn-glycerol-cholinephosphotransferase was virtually absent from the bile canalicular membranes but the specific activities of
S-adenosyl-L-methionine:phosphatidylethanolamine N-methyltransferase and acyl-CoA:1-acyl-sn-glycero-3-phosphoryl-choline acyltransferase were 11–15% of those found in the microsomes. The bile canalicular membranes
also contained detectable acyl-CoA:sn-glycero-3-phosphate acyltransferase activity and the ability to potentiate the Ca++-stimulated exchange of bases between different phospholipids. These findings indicate that the bile canalicular membranes
have a very limited capacity for the formation of phosphatidylcholine under the assay conditions employed.
A preliminary report of this paper was given at the AOCS Spring Meeting, Dallas, April 1975. 相似文献
7.
Using chiral-phase HPLC, we determined the stereochemical configuration of the phosphatidylglycerols (PtdGro) synthesized
in vitro from 1,2-diacyl-sn-glycero-3-phosphocholine (PtdCho, R configuration) or 1,2-diacyl-sn-glycero-3-phosphoethanolamine (PtdEtn, R configuration) and glycerol by transphosphatidylation with bacterial phospholipase D (PLD). The results obtained with PLD
preparations from three Streptomyces strains (S. septatus TH-2, S. halstedii K5, and S. halstedii subsp. scabies K6) and one Actinomadura species were compared with those obtained using cabbage and peanut PLD. The reaction was carried out at 30°C in a biphasic
system consisting of diethyl ether and acetate buffer. The resulting PtdGro were then converted into bis(3,5-dinitrophenylurethane)
derivatives, which were separated on an (R)-1-(1-naphthyl)ethylamine polymer. In contrast to the cabbage and peanut PLD, which gave equimolar mixtures of the R,S and R,R diastereomers, as previously established, the bacterial PLD yielded diastereomixtures of 30–40% 1,2-diacyl-sn-glycero-3-phospho-1′-sn-glycerol (R,S configuration) and 60–70% 1,2-diacyl-sn-glycero-3-phospho-3′-sn-glycerol (R,R configuration). The highest disproportionation was found for the Streptomyces K6 species. The present study demonstrates that bacterial PLD-catalyzed transphosphatidylation proceeds to a considerable
extent stereoselectively to produce PtdGro from PtdCho or PtdEtn and prochiral glycerol, indicating a preference for the sn-3′
position of the glycerol molecule. 相似文献
8.
Kouichi Nakagawa 《Journal of the American Oil Chemists' Society》2009,86(1):1-17
Dynamics of various spin probes in aqueous dispersions of nonionic amphiphilic compound, [poly(oxyethylene) hydrogenated castor
oil, HCO], were investigated by EPR (electron paramagnetic resonance) and saturation recovery (SR) spectroscopies. Partitioning,
rotational correlation time (τR), rotational diffusion coefficient, and electron spin-lattice relaxation time (T
1e) in dispersions of the HCO membrane were obtained. The partitioning of water soluble spin probes, DTBN and TEMPO, in the
aqueous and vesicle phases was determined by an EPR linewidth simulation as a function of temperature. The results suggest
that DTBN and TEMPO have a similar partitioning in the vesicle phase throughout the temperatures studied. The longer τR and shorter T
1e (~0.33 μs) values of DTBN in the vesicle phase were obtained, and could be attributed to the probe environment in the membrane.
The simulation results for fast tumbling probes were quite different from those of conventional intensity analysis (spectral
parameter, f). Thus, the simulation and T
1e analyses have provided a quantitative understanding of the probe dynamics in both phases. Aliphatic spin probes, doxylstearic
acids (DSAs) and 3β-doxyl-5α-cholestane (CHL), were used for monitor of various membrane motions. The EPR spectra were quantitatively
analyzed by a slow tumbling simulation. The rotational diffusion coefficients and order parameter were obtained by the simulation.
In addition, the direct observations of the behavior of the probes were measured by SR method. The results were consistent
with T
1e obtained for spin probes. Thus, the quantitative results regarding EPR, SR method, various simulation analyses have provided
detailed information regarding physicochemical properties of the various moieties of the probe region in the amphiphilic compound. 相似文献
9.
Kacper Przykaza Klaudia Woźniak Małgorzata Jurak Agnieszka Ewa Wiącek 《Journal of surfactants and detergents》2019,22(5):1213-1228
Polyetheretherketone (PEEK) is a highly biocompatible polymer widely used in medicine as an implant production material. In this article, the PEEK surface was characterized in terms of its wettabillity properties after the physicochemical modifications by treatment with the low-temperature air plasma and covering with the Langmuir–Blodgett (LB) monolayers of polypeptide (cyclosporine A, CsA) and/or phospholipid (1,2-dipalmitoyl-sn-glycero-3-phosphocholine, DPPC). The LB deposition was preceded by the analysis of miscibility and morphology of monolayers at the air/water interface by means of the Langmuir technique and Brewster angle microscopy (BAM). Then, wettability of the polymer-supported films was evaluated by the contact angle measurements of three probe liquids of different characters (two polar—water and formamide, one apolar—diiodomethane). The measured contact angles allowed for determination of the surface free energy and its components based on the Lifshitz-van der Waals/acid–base (LWAB) approach. Some relations between the kind and magnitude of interactions within the model membranes on the water subphase and those of the PEEK-supported membranes with the liquids were found out. The results allowed obtaining the interesting models of biological coatings with potential applications. 相似文献
10.
A simple method for synthesizing diastereomerically pure phosphatidylglycerols (PtdGro), namely, 1,2-diacyl-sn-glycero-3-phospho-3′-sn-glycerol (R,R configuration) and 1,2-diacyl-sn-glycero-3-phospho-1′-sn-glycerol (R,S configuration) was established. For this purpose, diastereomeric 1,2-O-isopropylidene PtdGro were prepared from 1,2-diacyl-sn-glycero-3-phosphocholine (PtdCho) and enantiomeric 1,2-O-isopropylideneglycerols by transphosphatidylation with phospholipase D (PLD) from Actinomadura sp. This species was selected because of its higher transphosphatidylation activity and lower phosphatidic acid (PtdOH) formation
than PLD from some Streptomyces species tested. The reaction proceeded well, giving almost no hydrolysis of PtdCho to PtdOH in a biphasic system consisting
of diethyl ether and acetate buffer at 30°C. The isopropylidene protective group was removed by heating the diastereomeric
isopropylidene PtdGro at 100°C in trimethyl borate in the presence of boric acid to obtain the desired PtdGro diastereomers.
The purities of the products, which were determined by chiral-phase HPLC, were exclusively dependent on the optical purities
of the original isopropylideneglycerols used. The present method is simple and can be utilized for the synthesis of pure PtdGro
diastereomers having saturated and unsaturated acyl chains. 相似文献
11.
The differences in distribution of geometric isomers of unsaturated PC hydroperoxides generated by free radical oxidation
were compared, as corresponding hydroxy analogs, in heterogeneous liposomes and in a homogeneous methanol solution by using
HPLC with UV detection due to the presence of conjugated dienes. Identification of fractionated peak components was carried
out by GC-MS. When the oxidation of 1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphocholine, PC(16∶0/18∶2), was initiated in liposomes by a hydrophilic azo radical initiator, and in a methanol
solution by a hydrophobic azo radical initiator, there was no significant difference in the relative percentages of 1-palmitoyl-2-(9-hydroxy-trans-10,trans-12-octadecadienoyl)-sn-glycero-3-phosphocholine (9-t,t-OH PC) and 1-palmitoyl-2-(13-hydroxy-trans-9,trans-11-octadecadienoyl)-sn-glycero-3-phosphocholine (13-t,t-OH PC) between the PC oxidized in liposomes and in the methanol solution. For the oxidation of 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine, PC(16∶0/20∶4), the relative percentage of 1-palmitoyl-2-(5-hydroxy-trans-6,cis-8,11,14-eicosatetraenoyl)-sn-glycero-3-phosphocholine (5-OH PC) was significantly higher (P<0.01) than that of 1-palmitoyl-2-(15-hydroxy-cis-5,8,11,trans-13-eicosatetraenoyl)-sn-glycero-3-phosphocholine (15-OH PC) in liposomes. For the homogeneous methanol solution of PC(16∶0/20∶4), the relative percentage
of 5-OH PC was close to that of 15-OH PC. For the PC(16∶0/20∶4) oxidized in bulk with added pentamethylchromanol, the individual
amount of 15-OH PC, 1-palmitoyl-2-(11-hydroxy-cis-5,8trans-12,cis-14-eicosatetraenoyl)-sn-glycero-3-phosphocholine (11-OH PC), 1-palmitoyl-2-(12-hydroxy-cis-5,8,trans-10,cis-14-eicosatetraenoyl)-sn-glycero-3-phosphocholine (12-OH PC), 1-palmitoyl-2-(8-hydroxy-cis-5,trans-9,cis-11,14-eicosatetraenoyl)-sn-glycero-3-phosphocholine (8-OH PC), 1-palmitoyl-2-(9-hydroxy-cis-5,trans-7,cis-11,14-eicosatetraenoyl)-sn-glycero-3-phosphocholine (9-OH PC), and 5-OH PC were close to each other compared to the corresponding values in liposomes
and in methanol solution. The results obtained by gel permeation chromatography of the PC liposomes containing hydrophilic
2,2′-azobis-2-amidinopropane) dihydrochloride (AAPH) suggest that the AAPH added to the liposomes of PC(16∶0/20∶4) was partitioned
into the water phase and out of the hydrophobic region of the fatty acyl moieties of the PC. These results confirm that the
distance that exists in the bis-allylic carbons of the unsaturated fatty acyl moieties of PC from the interface between the
hydrophilic region of PC and the water phases played an important role in influencing hydrogen abstraction to form a symmetrical
distribution of hydroperoxide isomers in both the heterogeneous liposomes and the homogeneous methanol solution. 相似文献
12.
Ether lipid content and fatty acid distribution in rabbit polymorphonuclear neutrophil phospholipids
This study was undertaken to determine if rabbit neutrophils contain sufficient ether-linked precursor for the synthesis of
1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (platelet activatin factor) by a deacylation-reacylation pathway. The phospholipids from rabbit
peritoneal polymorphonuclear neutrophils were purified and quantitated, and the choline-containing and ethanolamine-containing
phosphoglycerides were analyzed for ether lipid content. Choline-containing phosphoglycerides (37%), ethanolamine-containing
phosphoglycerides (30%), and sphingomyelin (28%) were the predominant phospholipid classes, with smaller amounts of phosphatidylserine
(5%) and phosphatidylinositol (<1%). The choline-linked fraction contained high amounts of 1-O-alkyl-2-acyl-(46%) and 1,2-diacyl-sn-glycero-3-phosphocholine (54%), with a trace of the 1-O-alk-1′-enyl-2-acyl species. The ethanolamine-linked fraction contained high amounts of 1-O-alk-1′-enyl-2-acyl-(63%) and 1,2-diacyl-sn-glycero-3-phosphoethanolamine (34%), and a low quantity of the 1-O-alkyl-2-acyl species (3%). The predominant 1-O-alkyl ether chains found in thesn-1 position of the choline-linked fraction were 16∶0 (35%), 18∶0 (14%), 18∶1 (26%), 20∶0 (16%), and 22∶0 (9%). The major 1-O-alk-1′-enyl ether chains found in thesn-1 position of the ethanolamine-linked fraction were 14∶0 (13%), 16∶0 (44%), 18∶0 (27%), 18∶1 (12%) and 18∶2 (3%). The major
acyl groups in thesn-1 position of 1,2-diacyl-sn-glycero-3-phosphocholine and 1,2-diacyl-sn-glycero-3-phosphoethanolamine were 16∶0, 18∶0 and 18∶1. The most abundant acyl group in thesn-2 position of all classes of choline- and ethanolamine-linked phosphoglycerides was 18⩺2. Although this work does not define
the biosynthetic pathway for platelet activating factor, it does show that there is ample precursor present to support its
synthesis by a deacylation-reacylation pathway. 相似文献
13.
Poly(3‐dodecylthiophene) (P3DDT), with different amounts of head‐to‐head configuration defects, was characterized by ultraviolet–visible, 1H‐NMR, photoluminescence, and Raman spectra. The heat‐induced conformational sample changes were studied by electron paramagnetic resonance (EPR). For the study of these changes, a spin‐probe technique was used, in which 5‐doxyl‐stearic acid methyl ester was applied as a spin probe. From the EPR spin‐probe spectra, rotational correlation times and order parameters were calculated. The heat‐induced conformational changes of P3DDT were accompanied by a monotonic decrease in the rotational correlation time up to approximately ?33°C (240 K) and then by an increase in the range of the glass‐transition temperatures, with the maximum being near room temperature and depending on the effective conjugation length. Afterward, the rotational correlation times had a decreasing tendency up to 90°C (363 K). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2215–2223, 2003 相似文献
14.
The diether-phosphonate lecithin analog DL-2-hexadecoxy-3-octadecoxypropyl-phosphonylcholine was prepared in 55% overall yield
by reaction of 2-hexadecoxy-3-octadecoxypropylphosphonic acid with choline iodide andp-toluenesulfonyl chloride, and purified chromatographically.
The diester-phosphonate lecithin analog 1,2-dipalmitoyl-sn-glycero-3-[2′-trimethyl-ammonium) ethylphosphonate) was prepared fromsn-glycerol-1,2-dipalmitate and 2-(trimethylammonium) ethylphosphonyl dichloride, and the reaction mixture purified chromatographically.
The lecithin analog was obtained in an anhydrous form. 相似文献
15.
A method is described for the purification of a number of phospholipids by preparative high performance liquid chromatography
(HPLC). Purification of digalactosyl-diglyceride from spinach and egg phosphatidylcholine, 1,2-dioleoyl-sn-glycero-3-phosphocholine and 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine from its reaction mixture have been resolved. The lipid separation is performed on a polygosil
column and the individual compounds are monitored directly by refractive index detection. Chloroform/methanol mixtures are
used as eluent systems, providing a wide polarity range to separate the classes of lipids. The developed equipment can be
used for columns between 10 and 50 cm long and 4 and 50 mm inner diameter. The flow rate could be varied between 1 and 100
ml/min and applied pressures between 10 and 450 bars. 相似文献
16.
Electron paramagnetic resonance (EPR) in conjunction with a slow-tumbling simulation was utilized for defining stratum corneum
(SC) lipid structure. SC from the back of hairless mouse (HOS:HR-1) was stripped consecutively from one to three or four times
using a glass plate coated with a cyanoacrylate resin. Aliphatic spin probes, 5-doxylstearic acid (5-DSA) and 3β-doxyl-5α-cholestane
(CHL), were used to evaluate the SC ordering. EPR spectrum of 5-DSA incorporated in the SC demonstrated a characteristic peak
for the first strip. A slow-tumbling simulation for 5-DSA showed clear differences in EPR intensities as well as ordering
values (S
0) of the SC for control and terpenes treated SC. The α-terpineol enhanced the permeation of the single chain 5-DSA about three
times more than that of the control. However, EPR spectra of CHL in the SC did not show a clear difference for each strip,
except for the signal intensity. The results imply that CHL permeates into SC lipid differently from 5-DSA. The enhancement
of the 5-DSA is more significant than that of CHL. Therefore, the present results can be useful for various drug administrations
via the skin. 相似文献
17.
Luís M. S. Loura 《International journal of molecular sciences》2012,13(11):14545-14564
Förster resonance energy transfer (FRET) is a powerful tool used for many problems in membrane biophysics, including characterization of the lateral distribution of lipid components and other species of interest. However, quantitative analysis of FRET data with a topological model requires adequate choices for the values of several input parameters, some of which are difficult to obtain experimentally in an independent manner. For this purpose, atomistic molecular dynamics (MD) simulations can be potentially useful as they provide direct detailed information on transverse probe localization, relative probe orientation, and membrane surface area, all of which are required for analysis of FRET data. This is illustrated here for the FRET pairs involving 1,6-diphenylhexatriene (DPH) as donor and either 1-palmitoyl,2-(6-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino] hexanoyl)- sn-glycero-3-phosphocholine (C6-NBD-PC) or 1-palmitoyl,2-(12-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]dodecanoyl)-sn-glycero-3-phosphocholine (C12-NBD-PC) as acceptors, in fluid vesicles of 1,2-dipalmitoyl-sn-3-glycerophosphocholine (DPPC, 50 °C). Incorporation of results from MD simulations improves the statistical quality of model fitting to the experimental FRET data. Furthermore, the decay of DPH in the presence of moderate amounts of C12-NBD-PC (>0.4 mol%) is consistent with non-random lateral distribution of the latter, at variance with C6-NBD-PC, for which aggregation is ruled out up to 2.5 mol% concentration. These conclusions are supported by analysis of NBD-PC fluorescence self-quenching. Implications regarding the relative utility of these probes in membrane studies are discussed. 相似文献
18.
Marie-Aude Rouet-Mayer Olga Valentova Elizabeth Simond-Côte Jean Daussant Claudine Thévenot 《Lipids》1995,30(8):739-746
Using the spectrofluorimetric method described by Wittenaueret al. [Wittenauer, L.A., Shirai, K., Jackson, R.L., and Johnson, J.D. (1984)Biochem. Biophys. Res. Commun. 118, 894–901] for phospholipase A2 (PLA2) measurement, we have detected a phospholipase activity in Ailsa Craig and in mutantrin tomatoes at their normal harvest time (mature green stage). This activity in Ailsa Craig tomatoes increased at the beginning
of fruit ripening (green-orange stage) and then decreased slowly. The decrease in activity, however, was greater when ripening
occurred after tomato picking at normal harvest time than when ripening occurred on tomato plants. This phospholipase activity
was always higher inrin tomatoes than in normal ones. Thin-layer chromatography of compounds obtained after incubation of tomato extract demonstrated
a decrease in the substrate 1-acyl-2-{6[(7-nitro-2,1,3, benzoxadiazol-4-yl)amino]-caproyl}-sn-glycero-3-phosphocholine (C6-NBD-PC), and an increase in one product (NBD-aminohexanoic acid), but failed to detect the second product (1-acyl-sn-glycero-3-phosphocholine). We, therefore, developed a new one-step method for separation and quantification of a mixture
of phospholipids and other lipids, using straight-phase-high-performance liquid chromatography with light-scattering detection.
This method detected another fatty acid-releasing activity in enzyme extract from green-orange tomatoes. This lipolytic enzyme
(or family of enzymes) slowly produced free fatty acids when 1-oleoyl-sn-glycero-3-phosphocholine was added as substrate. The production of fatty acids was stoichiometric and more rapid when 1-oleoyl-sn-glycero-3-phosphate and 1-oleoyl-sn-glycerol were used as substrates. On the other hand, the same tomato extract was unable to hydrolyze 1,2-dioleoyl-sn-glycero-3-phosphate and 1,2-dioleoyl-sn-glycerol. Crude tomato extract exhibited lipid acyl hydrolase activity according to the definition of Galliard [Galliard,
T. (1979), inAdvances in the Biochemistry and Physiology of Plant Lipids (Appelqvist, L.A., and Liljenberg, C. eds.), pp. 121–132, Elsevier, Amsterdam]. But in order to demonstrate whether tomato
extract contains PLA2 activity and/or lysophospholipase activity, further work on purified tomato extract will be necessary. 相似文献
19.
Formation of novel thermo-responsive hybrid vesicles: influence of molar ratio of lipids and heating
Thermo-responsive triblock copolymer, [poly(2-isopropyl-2-oxazoline)-b-poly(dimethylsiloxane)-b-poly(2-isopropyl-2-oxazoline] (IDI) was synthesized, for the first time, by ring opening polymerization and it can self-assemble in to polymersome in aqueous solution. We demonstrate a simple route to develop the novel hybrid vesicles, from the IDI and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), by systematically regulating the molar ratio of DMPC. Effect of heating on the hybrid vesicular solution has also been examined. Differential scanning calorimetry (DSC), dynamic light scattering and fluorescence spectroscopy were used to investigate the role of molar ratio of DMPC and heating time of the mixture on the formation of hybrid vesicles. From DSC measurements, we interestingly found that heating the mixture of IDI and DMPC enhanced the insertion of IDI into the membrane of liposomes. The present findings confirm the potential utility of hybrid vesicular systems for the design of functional hybrid materials and could be used for controlled drug delivery applications. 相似文献
20.
A comparative approach has been used to investigate the molecular species composition of phosphatidylcholine (PC) and its
age variation throughout several developmental stages of chick and duck embryo brains. The brain PC consist of 15 major molecular
species which do not undergo appreciable variation in their relative abundance either during embryonic development or between
equivalent stages of maturation in the 2 avian species. In fact, a highly invariable molecular architecture of PC is shown
in the developing organ. Molecular species containing saturated or monounsaturated fatty acids were dominant in all stages
of development of the avian embryo brain. Among these molecular species, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine accounted for 75–80% of the total PC. 相似文献