Effect of 1-palmitoyl lysophosphatidylcholine on phase properties of 1,2-dipalmitoyl phosphatidylethanolamine: a thermodynamic and NMR study (original) (raw)
Related papers
Chemistry and Physics of Lipids, 1989
The orientational order and rotational dynamics of 1-palmitoyl-2-[[2-[4-(6-phenyl-trans-l,3,5-hexatrienyl)phenyl]ethyl] carbon yl]-3-sn-phosphatidylchofine (DPH-PC) in dilinoleoylphosphatidylethanolamine (DLPE) and 1-palmitoyl-2-oleoylphosphatidylcholine 0aOPC) binary lipid mixtures were investigated. A previous study (Biochim. Biophys. Acta 731 (1983) 177) indicated that the empirical phase diagram of POPC/DLPE can roughly be divided into three zones. They are the lamellar (15% PC and higher), intermediate (5-15% PC) and inverted hexagonal (0-50/0 PC) phases. As the lipids changed from the lamellar to intermediate phase, the order parameter increased at all temperatures (1-50°C). On the contrary, the rotational diffusion decreased at high temperatures (20-50°C) but increased at low temperatures (I-10°C). These results indicate that the intermediate phase is in a stressed state at high temperatures but in a highly mobile amorphous state at low temperatures. As the lipid progressed from the intermediate toward hexagonal phase, the order parameter decreased abruptly at all temperatures. The ratio of order parameter in the intermediate phase to that in the hexagonal phase was calculated. This ratio was found to increase linearly with temperature, indicating that a distinct change in the packing symmetry of lipids occurred as temperature increased. From the intermediate to hexagonal phase, the rotational diffusion increased slightly at high temperatures but declined abruptly at low temperatures. These results further agreed with the stressed and amorphous natures of the intermediate phases as described above.
Chemistry and Physics of Lipids, 1988
Several new features of the phase diagram of L-dipalmitoylphosphatidylcholine (DPPC)/palmitic acid mixtures in excess water were established by means of static and time-resolved X-ray diffraction, densitometry and differential scanning calorimetry (DSC). At low temperatures, palmitic acid has a biphasic effect on the lamellar subgel phases: at concentrations below 5--6 mol%, it prevents formation of the DPPC subgel phase (L), while at higher contents (between about 40 and 90 tool%) another subgel phase (Lc~°~) is formed as a result of lipid co-crystallization at 1 DPPC : 2 palmitic acid stoichiometry. A crystalline palmitic acid phase separates from Lc~ above 70--80 mol% of fatty acid. The L c ~phase transforms into a lamellar gel phase (L~) in an endothermic transition centered at 38°C. At high temperatures, the mixtures form hexagonal liquid-crystalline phase (Hit) in the region of 60--70 mol% and an isotropic phase (I) at 90--100 mol% of palmititc acid. No coexistence of H n phase with the fluid lamellar phase of DPPC was observed at intermediate compositions (20 and 50 mol% of palmitic acid) but rather formation of a complex phase with non-periodic geometry characterized by molten chains and a broad, continuous small-angle scattering band. No evidence for fluid phase coexistence was found also at compositions betwewen H n and I phases. The L#--Hjl transition at 60--70 tool% of palmitic acids is readily reversible and two-state in both heating and cooling modes. It is characterized by the coexistence of initial and final phases with no detectable intermediates by time-resolved and static X-ray diffraction. The crystalline-isotropic transition in palmitic acid is two-state only in heating direction. On cooling, it is characterized by strong undercooling and gradually relaxing lameUar crystalline structures. The slowly reversible LcC°m--L~ transition proceeds continuously through intermediate states. Although clearly discernible by both DSC and X-ray diffraction, it is not accompanied by specific volume changes.
Biochimica Et Biophysica Acta-biomembranes, 1993
1-Octadecanoyl, 2-decanoylphosphatidylethanolamine (C(18:0)C(10:0)PE) has been reported to exhibit mixed interdigitated gel-phase packing of the phospholipid acyl chains (Mason, J.T. and Stephenson, F.A. (1990) Biochemistry 29, 590–598). In contrast, ditetradecanoylphosphatidylethanolamine (C(14:0)C(14:0)PE) packs without significant interdigitation of the phospholipid acyl chains across the bilayer center. In this report, the gel-fluid transition temperatures of C(18:0)C(10:0)PE and C(14:0)C(14:0)PE in multimellar dispersion were determined by fluorescence anisotropy of cis-parinaric acid and trans-parinaric acid with a descending temperature scan rate of 0.67°C/min. The transition mid-points detected for C(18:0)C(10:0)PE with cis-parinaric acid were 19°C in water, 18°C at pH 8.1, and 14°C at pH 10. The phase diagram for C(14:0)C(14:0)PE and C(18:0)C(10:0)PE at pH 10 suggests complete mixing in the fluid phase and considerable immiscibility in the gel phase. Cross-linking of equimolar mixtures of C(14:0)C(14:0)PE and C(18:0)C(10:0)PE with dimethylsuberimidate at pH 10 revealed a random arrangement of the two species in the fluid phase, confirming the notion that C(18:0)C(10:0)PE and C(14:0)C(14:0)PE are miscible in the fluid phase, as determined from the phase diagram. In contrast, cross-linking of the equimolar mixture of C(18:0)C(10:0)PE and C(14:0)C(14:0)PE in the gel phase at 0°C revealed a non-random arrangement, demonstrating and confirming immiscibility in the gel phase.
Chemistry and Physics of Lipids, 1990
Fourier transform infrared (FTIR) and time-resolved fluorescence spectroscopy have been employed to examine the structural dynamics of lipid fatty acyl chains and lipid/water interfaciai region of a binary lipid mixture containing unsaturated phosphatidylethanolamine (PE) and diacylgiycerol (DG). Infrared vibrational frequencies of the CH 2 symmetric stretching and the C = O stretching bands of the lipids were measured at different lipid compositions and temperatures. For 0% DG, the lamellar gel to lamellar liquid crystalline (L0-L) and the L, to inverted hexagonal (L-Hu) phase transitions were observed at 'x,15° and 55°C, respectively. As the DG content increased gradually from 0% to 15%, the Lo-HI~ phase transition temperature decreased drasticaily while the LFL ° phase transition temperature decreased only slightly. At 10% DG, a merge of these two phase transitions was noticed at ~I0°C. For the composition study at 23°C, the La-H u transition occurred at ~6-10% DG as indicated by abrupt increases in both the CH 2 and C = O stretching frequencies at those DG contents. Using time-resolved fluorescence spectroscopy, abrupt decreases in both the normalized long time residual and the initial slope of the anisotropy decay function of lipid probes, ~-paimit~y~-2-[[2-[4-(6-pheny~-trans-~'3~5-hexatrieny~)pheny~]ethy~]carb~ny~]~3-sn-ph~sphatidy~ch~ine~ in these PE/ DG mixtures were observed at the Lo-H H phase transition. These changes in the anisotropy decay parameters suggested that the rotational dynamics and orientationai packing of the lipids were altered at the composition-induced L-H~j transition, and agreed with a previous temperature-induced L-H u transition study on pure unsaturated PE (Cheng (1989) Biophys. J. 55, 1025-1031). The fluorescence lifetime of water soluble probes, 8,1-anilinonapthalenes sulfonate acid, in PE/DG mixtures increased abruptly at the L,-H, phase transition, suggesting that the conformation and hydration of the lipid/water interfacial region also undergo significant changes at the Lo-H~ transition.
Chemistry and Physics of Lipids, 1998
Despite the fact that fully hydrated multilayers of phosphatidylcholines have been extensively studied in the past, phase transitions such as the pretransition and the subtransition are still the object of different interpretations and contradictory observations. In order to obtain more information on the structural changes associated to these transitions for dipalmitoyl phosphatidylcholine (DPPC), a study has been done using both transmission and polarized attenuated total reflection infrared spectroscopy. At the pretransition, we observe that the extended hydrocarbon chains become less tilted with respect to the bilayer normal. The pretransition is also characterized by an increase in the hydration of the DPPC bilayer and the appeareance of the ripple structure. As opposed to previous findings, we do not observe a major variation of the acyl chain packing mode at the pretransition. These observations are supported by the investigation of DPPC with 5 mol% cholesterol, since this sterol is known to be a strong inhibitor of the pretransition. On the other hand, a drastic change in chain packing, characterized by infrared bands due to the methylene scissoring mode, is observed at the subtransition. Also, below the subtransition, we observe an increase of the hydrocarbon chain rotational disorder. Some correlations have also been made between the spectral parameters normally used to characterize the degree of order of the acyl chains. These correlations have allowed us to evaluate more precisely at the molecular level the subtle structural changes that occur during phase transitions of DPPC.
Theoretical models of phospholipid systems have indicated that both intramolecular and intermolecular forces are important in governing their acyl chain order. Knowledge of the nature and magnitude of these interactions is central to understanding the balance of forces present in lipid lamellar phases, which in turn is related to their microscopic and macroscopic behavior. It is possible to explore the contribution of intermolecular interactions using lipid systems with the same headgroup and acyl chain identity by variation of the ratio of the headgroups to acyl chains. In this paper, deuterium (2H) NMR spectroscopy has been used to gain information on the orientational order of an acyl chain perdeuterated lipid, l-perdeuteriopalmitoyl-sn-Bly~3-phosphocholine (PaLpc-d31), in various molecular environments. The orientational order of PaLpGd31 was studied in four different lamellar phases, including pure PaLPC-d31 (containing 10 wt % H20), diplmitoyl-phosphatidyl~holine/PaLPC-d3~ (3:1), palmitic a~id/PaLPC-d~~ (l:l), and ch~lesterol/PaLPC-d~~ (1:l) (each containing 50 wt % HzO). ' H NMR spectra were obtained for the low-temperature and liquid-crystalline (L,) states of each of these mixtures. In the low-temperature state, the f i t three systems yielded ZH NMR spectra characteristic of all-trans chains undergoing axial diffusion, with the methyl groups rotating about their C3 axes. The molecular order, as judged by the presenoe of spectral discontinuities and moment analysis, was found to be almost identical in the low-tempratwe phases. A different behavior was observed for the ch~lesterol/PaLPC-d~~ (1:l) sample in that the maximum splitting was close to the all-trans rotating value, with a profile of quadrupolar splittings due to inmased disorder near the chain ends. The f i t three systems underwent orderdisorder phase transitions near the same midpoint temperature (range of T, values 40-48 "C), whereas the ch~lesterol/PaLPC-d~~ (1:l) sample did not display a transition over the temperature range studied. In the L, phase, where order profdm were determined as a function of acyl chain segmglt position, the segmental ordering d i f f e r e d significantly among the samples. The differences were interpreted using a simple diamond lattice model for the acyl chain configurational statistics, as a means of comparing the effective lengths, (L), projected along the bilayer normal and estimated chain cross-sectional areas, (A), of PaLPC-d31 in the various mixtures. The derived values of (L) and (A) can be understood qualitatively in terms of average packing parameters related to the balance of forces in the headgroup and acyl chain regions, or alternatively the curvature free energy of the membrane lipid-water interface. In lamellar phases of pure P~L P C-C~~~ the curvature stnap is potentially large, and interdigitation of the acyl chains of the appoaed monolayers may occur. However, in mixtures of PaLPC-d31 with 1 , 2-d i p a l m i t o y l-s n-B l y~~3-p h o s p~~~e (DPPC), the curvature elaatic stress is apparently relieved by an increase in the cross-sectional acyl chain area, (A), Le. corresponding to an increase in configurational f d o m. The data were also compared to the results of statistical theories to yield additional knowledge of the intermolecular forces. These studies indicate how the segmental ordering reflects intermolecular interactions within a given lamellar phase. Avmge properties of the entire system such as average cross-sectional arm accessible to each acyl chain relative to the headgroup area can be modulated by these interactions. Such intermolecular interactions may be related to the prcaence of lipid diversity in biological membranes.
Biochimica et Biophysica Acta (BBA) - Biomembranes, 1987
The phase behaviour of 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC) has been investigated by high sensitivity differential scanning calorimetry, 2H nuclear magnetic resonance and X-ray diffraction. Depending on the thermal history of the sample, as many as three specific heat maxima are observed by DSC. Only two of these occur after prolonged incubation at temperatures below-6 °C or after repeated temperature cycling. The total enthalpy of these two peaks, 6.75 kcal/mol DLPC, and the changes in orientational order observed by 2H-NMIL suggest that both of these peaks involve hydrocarbon chain melting and the structural reorganization that occurs in the sub-transition of longer chain diacylPC.
Biochimica et Biophysica Acta (BBA) - Biomembranes, 1996
A long-living metastable rippled phase p~,t has been earlier reported to foma in aqueous dispersions of dipulmitoylphosphatidylcholine (DPPC) upon cooling from the lamellar liquid crystalline phase L,, Bi,~phys. J. 56. 757-768). Here we demonstrate that similar metastable phases form also in distearoylphosphatidytcholine (DSPC) and dihexadecylphosphatidylcholine (DHPC) but not in dimyristoylphosphatidylcholine (DMPC), The thermodynamic parameters of p~t in DPPC, DSPC and DHPC bare been characterized in detail by means of differential scanning calorimetry and scanning densitometry. It is shown that the P~' .~; phase in these three lipids has higher specific heat capacity by 0.1-0.4 kcal K -~ reel -t and higher specific volume by I-2 p.I/g than the equilibrium Ptr phase fonned upon heating from the L0, phase. The P~"--+ L, transition in these three lipids takes place at 0.06-0.14°C lower temperature than the P/r--' L,, transition. Its enthalpy is lower by 5-11C/c and the apparent maximum specific heat C~ ''' is lower by I 1-14c/c. The P~; phase is a long-living phase -it does not relax into the equilibrium Pt~ for at least severt, hours. The replacement of the ester glycerol-hydrocarbon chain linkages in DPPC with ether bonds in DHPC does not influence the tbrmation of P~?".
An ordered metastable phase in hydrated phosphatidylethanolamine: the Y-transition
Biochimica et Biophysica Acta (BBA) - Biomembranes, 1999
By using time-resolved X-ray diffraction, differential scanning calorimetry and scanning densitometry, we observed rapid formation at low temperature of a metastable ordered phase, termed L R1 phase, in fully hydrated dihexadecylphosphatidylethanolamine (DHPE). The L R1 phase has the same lamellar repeat period as the gel L L phase but differs from the latter in its more ordered, orthorhombic hydrocarbon chain arrangement. It forms at about 12³C upon cooling and manifests itself as splitting of the sharp, symmetric wide-angle X-ray peak of the DHPE gel phase into two reflections. This transition, designated the`Y-transition', is readily reversible and proceeds with almost no hysteresis between cooling and heating scans. Calorimetrically, the L R1 CL L transition is recorded as a low-enthalpy (0.2 kcal/mol) endothermic event. The formation of the L R1 phase from the gel phase is associated with a small, about 2 Wl/g, decrease of the lipid partial specific volume recorded by scanning densitometry, in agreement with a volume calculation based on the X-ray data. The formation of the equilibrium L c phase was found to take place from within the L R1 phase. This appears to be the only observable pathway for crystallisation of DHPE upon low-temperature incubation. Once formed, the L c phase of this lipid converts directly into L L phase at 50³C, skipping the L R1 phase. Thus, the L R1 phase of DHPE can only be entered by cooling of the gel L L phase. The data disclose certain similarities between the low-temperature polymorphism of DHPE and that of long-chain normal alkanes. ß -ray di¡raction 0005-2736 / 99 / $^see front matter ß 1999 Elsevier Science B.V. All rights reserved. PII: S 0 0 0 5 -2 7 3 6 ( 9 8 ) 0 0 2 5 9 -
The miscibility and phase behavior of hydrated binary mixtures of two N-acylethanolamines (NAEs), N-myristoylethanolamine (NMEA), and N-palmitoylethanolamine (NPEA), with the corresponding diacyl phosphatidylethanolamines (PEs), dimyristoylphosphatidylethanolamine (DMPE), and dipalmitoylphosphatidylethanolamine (DPPE), respectively, have been investigated by differential scanning calorimetry (DSC), spin-label electron spin resonance (ESR), and 31P-NMR spectroscopy. Temperature-composition phase diagrams for both NMEA/DMPE and NPEA/DPPE binary systems were established from high sensitivity DSC. The structures of the phases involved were determined by 31P-NMR spectroscopy. For both systems, complete miscibility in the fluid and gel phases is indicated by DSC and ESR, up to 35 mol % of NMEA in DMPE and 40 mol % of NPEA in DPPE. At higher contents of the NAEs, extensive solid-fluid phase separation and solid-solid immiscibility occur depending on the temperature. Characterization of the structures of the mixtures formed with 31P-NMR spectroscopy shows that up to 75 mol % of NAE, both DMPE and DPPE form lamellar structures in the gel phase as well as up to at least 65°C in the fluid phase. ESR spectra of phosphatidylcholine spin labeled at the C-5 position in the sn-2 acyl chain present at a probe concentration of 1 mol % exhibit strong spin-spin broadening in the low-temperature region for both systems, suggesting that the acyl chains pack very tightly and exclude the spin label. However, spectra recorded in the fluid phase do not exhibit any spin-spin broadening and indicate complete miscibility of the two components. The miscibility of NAE and diacyl PE of matched chainlengths is significantly less than that found earlier for NPEA and dipalmitoylphosphatidylcholine, an observation that is consistent with the notion that the NAEs are most likely stored as their precursor lipids (N-acyl PEs) and are generated only when the system is subjected to membrane stress.