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1.
Harold C. Jarrell R.Andrew Byrd Roxanne Deslauriers Irena Ekiel Ian C.P. Smith 《生物化学与生物物理学报:生物膜》1981,648(1):80-86
31P-NMR is used to characterize the phase behavior of phosphonolipids in both model and biological membranes. ( gives rise to static chemical shift tensor elements (?87, 5 and 63 ppm) which differ considerably from those reported for the analogous phospholipid, (?81, ?20 and 105 ppm). Phosphonolipid, as well as a mixture of phosphonolipid and , in aqueous dispersion gives rise to 31P spectra which may be interpreted in terms of lamellar structures. A mixture of phosphonolipid and egg phosphatidylethanolamine exhibits a bilayer-to-hexagonal phase transition with a concomitant decrease by one-half in the value of the 31P chemical shift anisotropies of both the phosphonate and phosphate resonances. The chemical shift anisotropy associated with phosphonolipid has been found to be consistently smaller than that observed for the analogous phospholipid. 31P-NMR spectra of total lipid extracts of Tetrahymena sp. indicate that both phospho- and phosphonolipids have a bilayer organization between ?20 and 20°C. 相似文献
2.
Hector L. Casal Ian C.P. Smith David G. Cameron Henry H. Mantsch 《生物化学与生物物理学报:生物膜》1979,550(1):145-149
The first application of infrared difference spectroscopy to the study of a natural biological membrane is described. Perdeuterated palmitic acid was incorporated biosynthetically into the lipids of the plasma membrane of Acholeplasma laidlawii and the temperature-induced structural rearrangement of the endogenous lipids monitored via their C2H vibrational modes. Changes in infrared parameters were studied between 0 and 50°C and contrasted with those occurring in the model membrane system of . The phase transition of the biomembrane occurs over a 20°C range with the temperature of the maximum rate of change of absorbance coinciding with that of the sharp phase transition of the model membrane. 相似文献
3.
Michael A. Singer Mahendra K. Jain Henry Z. Sable Henry J. Pownall William W. Mantulin Mark D. Lister Anthony J. Hancock 《生物化学与生物物理学报:生物膜》1983,731(2):373-377
We have examined the thermal characteristics and barrier properties of vesicles formed from six analogues of (DPPC). These analogues differ from DPPC in that the glycerol backbone has been replaced by each of the diastereoisomeric cyclopentane-1,2,3-triols. All of these compounds have main gel to liquid-crystal phase transition temperatures within 5 Kelvin of DPPC and four possess comparable enthalpies and entropies of transition. For two of the analogous, however, the values of the enthalpy and entropy of transition are more than double that of DPPC. The permeability characteristics and organization (as measured by diphenylhexatriene fluorescence depolarization) of vesicles formed from these two compounds suggest that their large transition enthalpy and entropy result from either a reorganization of the polar head group region during the transition or interdigitation of the acyl chains of opposing monolayers. 相似文献
4.
The dielectric dispersion in the MHz range of the zwitterionic dipolar phosphocholine head groups has been measured from 0–70°C for various mixtures of (DPPC) and cholesterol. The abrupt change in the derived relaxation frequency observed for pure DPPC at the gel-to-liquid crystalline phase transition at 42°C reduces to a more gradual increase of frequency with temperature as the cholesterol content is increased. In general the presence of cholesterol increases the DPPC head group mobility due to its spacing effect. Below 42°C no sudden changes in are found at 20 or 33 mol% cholesterol, where phase boundaries have been suggested from other methods. Above 42°C, however, a decrease in at cholesterol contents up to 20–30 mol% is found. This is thought to be partly due to an additional restricting effect of the cholesterol on the number of hydrocarbon chain conformations and consequently on the area occupied by the DPPC molecules. 相似文献
5.
Mahendra K. Jain Fausto Ramirez Terence M. McCaffrey Panayiotis V. Ioannou James F. Marecek J. Leunissen-Bijvelt 《生物化学与生物物理学报:生物膜》1980,600(3):678-688
Aqueous dispersions of monovalent and divalent cation salts of O-(1,2-dipalmitoyl-sn-glycero-3-phosphoryl) cholesterol form multilamellar vesicles as shown by freeze-fracture electron microscopy, by electron micrographs of the negatively stained liposomes, and by swelling curves of liposomes in hypoosmotic medium. Differential scanning calorimetry reveals that aqueous dispersions of divalent metal salts of O-(1,2-dipalmitoyl-sn-glycero-3-phosphoryl)-cholesterol undergo a characteristic thermotropic phase transition with a relatively large cooperative unit (n > 250 for the calcium salt). In contrast, monovalent cation salts of O-(1,2-dipalmitoyl-sn-glycerol-3-phosphoryl)cholesterol do not show a thermotropic phase transition under comparable conditions. The molecular area of O-(1,2-dipalmitoyl-sn-glycero-3-phosphoryl)cholesterol in a monolayer is the same in the presence and absence of Ca2+, and is virtually equal to the area of an equimolar mixture of dipalmitoyl phosphatidic acid and cholesterol. To account for the novel state induced by Ca2+ on aqueous dispersions of O-(1,2-dipalmitoyl-sn-glycero-3-phosphoryl)cholesterol (i.e., bilayer organization and highly cooperative phase transition), a linear array model is proposed in which Ca2+ bridges adjacent arrays of O-(1,2-dipalmitoyl-sn-glycero-3-phosphoryl)cholesterol molecules, thus freezing the acyl chains in their normal state. One of the main corollaries of the model is that the cooperative unit for a thermotropic phase transition is essentially one-dimensional, rather than a two-dimensional matrix. O-(1,2-Dipalmitoyl-sn-glycero-3-phosphoryl)cholesterol is proposed as an orientationally and conformationally restricted analog of glycerophospholipid plus cholesterol in bilayers. 相似文献
6.
is specifically deuterated at the C-2 position of the fatty acyl chains. Using deuterium magnetic resonance it is then possible to probe the chain conformation in the vicinity the polar head groups. Three separate quadrupole splittings are observed for bilayers of 1,2[2′-2H2] , indicating that the two chains behave differently. The synthesis of phosphatidylcholines each deuterated in only one chain allows the assignment of the three resonances. It is concluded that the beginnings of the two chains have orientations parallel and perpendicular to the bilayer normal. The data further suggest the possibility of two long-lived conformations of the glycerol constituent. 相似文献
7.
A complete titration of phosphatidic acid bilayer membranes was possible for the first time by the introduction of a new anaologue, acid, which has the advantage of a high chemical stability at extreme pH values. The synthesis of this phosphatidic acid is described and the phase transition behaviour in aqueous dispersions is compared with that of three ester phosphatidic acids; acid, 1,3-dimyristoylglycerol-2-phosphoric acid and acid.The phase transition temperatures () of aqueous phosphatidic acid dispersions at different degrees of dissociation were measured using fluorescence spectroscopy and 90° light scattering. The values are comparable to the melting points of the solid phosphatidic acids in the fully protonated states, but large differences exist for the charged states.The vs. pH diagrams of the four phosphatidic acids are quite similar and of a characteristic shape. Increasing ionisation results in a maximum value for the transition temperatures at pH 3.5 (). The regions between the first and the second of the phosphatidic acids are characterised by only small variations in the transition temperatures (extended plateau) in spite of the large changes occurring in the surface charge of the membranes. The slope of the plateau is very shallow with increasing ionisation. A further decrease in the H+ concentration results in an abrupt change of the transition temperature. The slope of the vs. pH diagram beyond becomes very steep. This is the 相似文献
8.
Some properties of monolayers of (POPG) alone or of POPG in mixtures with (DPPC) have been measured near 35°C during dynamic compression and expansion at 3.6 cm2·s?1. (2) The mean values of minimum surface tension (corresponding to maximum surface pressure) which could be obtained with pure POPG monolayers at high compression ranged from 15 to 18 mN·m?1 in the presence of Na+, Ca2+ or low pH (2.0) in the subphase. (3) The presence of Ca2+ or low pH in the subphase increased the collapse plateau ratios obtained on cyclic compression. This might represent enhanced respreading into the monolayer of pure POPG from a collapsed form during reexpansion of the surface. (4) Monolayers containing 10% or 30% POPG and 90% or 70% DPPC could be compressed to surface tensions approaching zero. (5) In such mixed monolayers, 10% or 30% POPG did not appear to enhance respreading, as measured by collapse plateau ratios, in the presence of Na+ or Ca2+ in the subphase. 相似文献
9.
Thomas D. Madden Carmen Vigo K.Richard Bruckdorfer Dennis Chapman 《生物化学与生物物理学报:生物膜》1980,599(2):528-537
Incubations of rat liver inner mitochondrial membranes with liposomes prepared from (DPPC) and cholesterol resulted in a considerable enrichment of the cholesterol composition of these membranes. This enrichment is not accompanied by an alteration in the membrane phospholipid content or fatty acid composition. The exogenous cholesterol appears to be integrated into the membrane structure because it has effects consistent with the known properties of this sterol in other natural and artificial membrane systems.Differential scanning calorimetry on both intact membranes and extracted lipids showed that as the ratio of cholesterol to phospholipid was increased, the endotherm corresponding to the lipid phase transition was reduced. Freeze-fracture electron microscopy of the native membranes showed that intramembranous particles are randomly distributed above the phase transition temperature. Below this temperature large smooth areas, believed to correspond to lipid in the gel state from which proteins have been excluded, can be observed. In the presence of high concentrations of cholesterol the fracture faces observed below the lipid transition temperature show no regions of phase segregation, an observation consistent with previous studies using pure lipids where cholesterol was observed to prevent the lipid undergoing a cooperative phase transition.The results are discussed in terms of the observed low concentrations of cholesteorl in normal liver inner mitochondrial membranes and the distribution of cholesterol within the liver cells. 相似文献
10.
Octávio M. De Oliveira Filgueiras Anton M.H.P. Van Den Besselaar Henk Van Den Bosch 《生物化学与生物物理学报:生物膜》1979,558(1):73-84
One of the unique features of the chromaffin granule membrane is the presence of about 17 mol% lysophosphatidylcholine. Lysophosphatidylcholine isolated from the granules could be degraded by approx. 94% by lysophospholipase. This result is consistent with chemical analyses data showing that about 9% of this lysophospholipid is 1′-alkenyl glycerophosphocholine.The localization of the acylglycerophosphocholine in the chromaffin granule membrane was studied by using pure bovine liver lysophospholipases. In intact granules only about 10% of the total lysophosphatidylcholine was directly available for enzymic hydrolysis. In contrast, when granule membranes (ghosts) were treated with lysophospholipases approx. 60% of the lysophosphatidylcholine was deacylated. These values did not increase after pre-treatment of intact granules or ghosts with trypsin. Added did not mix with the endogenous lysophosphatidylcholine pool(s) and remained completely accessible to added lysophospholipases. 相似文献
11.
C. Mombers P.W.M. Van Dijck L.L.M. Van Deenen J. De Gier A.J. Verkleij 《生物化学与生物物理学报:生物膜》1977,470(2):152-160
Using differential scanning calorimetry and freeze fracture electron microscopy interactions were studied between lipids and a spectrin · action complex isolated from human erythrocyte membranes. With dispersions of , and mixtures of these two compounds, which for experimental reasons were chosen as the lipid counterpart, such an interaction could clearly be deduced from changes in the temperature and the enthalpy of the phase transition. Furthermore it was demonstrated that the interaction with this membrane protein protects the bilayer against the action of Ca2+ and Mg2+ and prevents fusion of lipid vesicles which easily occurs in some of the systems when divalent ions were added to the pure lipid vesicles. 相似文献
12.
The hydration properties of Escherichia coli lipids (phosphatidylglycerol, phosphatidylethanolamine) and synthetic in H2O/2H2O mixtures (9:1, v/v) were investigated with 2H-NMR. Comparison of the 2H2O spin lattice relaxation time () as a function of the water content revealed a remarkable quantitative similarity of all three lipid-H2O systems. Two distinct hydration regions could be discerned in the relaxation time profile. (1) A minimum of 11–16 water molecules was needed to form a primary hydration shell, characterized by an average relaxation time of . (2) Additional water was found to be in exchange with the primary hydration shell. The exchange process could be described in terms of a two-site exchange model, assuming rapid exchange between bulk water with and hydration water with . Analysis of the linewidth and the residual quadrupole splitting (at low water content) confirmed the size of the primary hydration layer. However, each lipid-water system exhibited a somewhat different linewidth behavior, and a detailed molecular interpretation appeared to be preposterous. 相似文献
13.
A proton magnetic resonance procedure with tri(3-heptafluorobutyryl-d-camphorato)praseodymium (III) as a chiral shift eagent has been developed to determine the enantimeric purity of monoglycerides 1,2-diglycerides and triglycerides with one mono-unsaturated fatty acid at position or and two saturated fatty acids at the two other glycerol positions. A model compound, 1-oleoyl-2,3-dipalmitoyl-sn-glycerol, was converted ito the trimethylsilyl either of 2,3-dipalmitoyl-an-glycerol by epoxidation of the double bond, followed by pancreatic hydrolysis and separation and trimethylsilylation of the resulting , and . This separation becomes feasible by the contribution of the epoxy group to the polarity of the diglyceride. The protons of the trimethysilyl ether group were used for determining the enantiomeric ratio. The addition of a chira shift reagent induces a useful enantiomeric splitting which allows the accurate determination of the ratio of both enantiomers. The trimethylsilyl emers of 1,2-diglycerides are better suited for this purpose than the acetyl compounds. For monoglycetides, the earlier published method with the diaceltates gives a better line separation in 1H-NMR spectra. 相似文献
14.
J.T. OFlaherty Robert L. Wykle C.E. McCall T.B. Shewmake C.J. Lees M. Thomas 《Biochemical and biophysical research communications》1981,101(4):1290-1296
The human polymorphonuclear neutrophil degranulation response to 5,12-dihydroxy-6,8,10,14-eicosatetraenoic acid was completely desensitized by preincubating the cells with small amounts of this same fatty acid. Desensitization developed within 1 min, persisted in thoroughly washed cells, and was not due to inactivation of the stimulus. These desensitized cells, however, degranulated partially in response to the ionophore A23187 and normally in response to C5a, N-formyl-methionyl-leucyl-phenylalanine, 1-, and phorbol myristate acetate. Thus, the dihydroxy fatty acid is a unique stimulus which degranulates and desensitizes neutrophils by pathways at least partially distinct from those utilized by the other stimuli. The fatty acid, although rapidly formed in degranulating neutrophils, is unlikely to be an essential or universal mediator of the degranulation response. 相似文献
15.
We measured the 31P[1H] Nuclear Overhauser Effect (NOE) as a function of temperature and of 1H irradiation frequency, the linewidth as a function of temperature and the relaxation time T1 above and below the thermal transition temperature, of the 31P-NMR signal in sonicated liposomes of 1,2-dimiristoyl-3-sn-phosphatidylcholine (DMPC), 1,2-dipalmitoyl-3-sn-phosphatidylcholine (DPPC) and 1,2-dimiristoyl-3-sn-phosphatidylcholine (DSPC). The same measurements were repeated in the presence of high molecular weight dextrans. They strongly reduce the NOE and produce longer relaxation times T1. According to the current models, we were able to evaluate, in the different situations, the correlation time of the internal motion τG and the distance r between interacting groups in the region of the polar head groups. While the first parameter changes abruptly through the phase transition and under the effect of dextrans, the latter does not appear modified in any case. These results are discussed in terms of a conformational change of the phosphocholine head groups. 相似文献
16.
Martyn W. Hill 《生物化学与生物物理学报:生物膜》1974,356(1):117-124
The effect of the normal alcohols (up to ) and three clinically used anaesthetics, on the crystalline-liquid crystalline phase transition in have been studied. A one-degree depression was produced by a 4.4% concentration in the membrane of and agreeing well with the value calculated from the temperature and enthalpy of the transition. It is also shown that the relationship between the partition coefficient and the water solubility , holds for the solutes investigated here. The experimental method described offers a simple way of assessing the anaesthetic potency of a wide range of compounds. 相似文献
17.
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19.
[2-2H2]Oleic, [2-2H2]palmitic, [2-2H2]dihydrosterculic and [3-2H2]oleic acids were biosynthetically incorporated into the membrane lipids of Acholeplasma laidlawii B. 2H-NMR spectroscopy and spectral ‘de-Parking” (M. Bloom, J.H. Davis and M.I. Valic, Can. J. Phys., 58 (1980) 1510) were used to study the effect of lipid headgroup class on the conformational order in the vicinity of the C-2 position of the acyl chains of lipids in the liquid crystalline phase. The results indicate that although the orientation and conformations of the membrane lipids in the region of the C-2 position of the chains are qualitatively very similar among the various lipid classes, quantitatively there are some differences, particularly between the glycolipids and the phospholipids. These differences do not exted to the C-3 position. Unlike the headgroup class, the membrane proteins appear to have little if any effect on the molecular ordering of the lipids. 相似文献
20.
An aqueous dispersion of fully hydrated bovine sphingomyelin was studied using 14N-NMR spectroscopy. Spectra were obtained as a function of temperature over the range 15–80°C, in both the liquid crystal and gel phases. In the liquid crystal phase, powder pattern lineshapes were obtained, whose quadrupolar splitting slowly decreases with increasing temperature. The spectra are increasingly broadened as the temperature is lowered through the phase transition into the gel phase. The linewidths and the second moments of these spectra indicate that the onset of a broad phase transition occurs at approx. 35°C, in agreement with previous calorimetric and 31P-NMR measurements. There is no evidence from the lineshapes for an hexagonal phase in this system, and this conclusion is supported by X-ray diffraction measurements carried out on aqueous dispersions of sphingomyelin in both phases. Assuming that the static nitrogen quadrupole coupling constant is the same for both sphingomyelin and dipalmitoyl-l-α-phosphatidylcholine (DPPC), the decrease observed in the quadrupolar splitting of sphingomyelin compared to that of DPPC indicates that the orientational order of the choline headgroup in liquid crystalline sphingomyelin is not the same as that of its counterpart in DPPC. Preliminary relaxation time measurements of and are presented which suggest that there are also dynamic differences between sphingomyelin and DPPC in the choline headgroup. 相似文献