Tilt angle of acyl chains of dmpc bilayer in the gel phase was in great agreement. Before the afm experiments, the liquid cell is rinsed. The experimental dsc curve is the temperature rate of heat absorption, equivalent to the excess heat capacity function, cex, given by eqn cex. The phase transitions of binary lipid mixtures are studied by a combination of peltierelementbased adiabatic scanning calorimetry pasc and quartz crystal microbalance with dissipation monitoring qcmd. A phase of a thermodynamic system and the states of matter have uniform physical properties. The systematic study of the mesomorphic phase properties of synthetic and biologically derived lipids began some 30 years ago. Polar interactions play an important role in the energetics. The work reported herein deals with a new general method of t c determination based on the optical properties modifications of aqueous surfactant solutions when the phase transitions occur in the phospholipid membrane. The incorporation of 4 into fluidphase bilayers of this lipid is fast a few minutes. Data acquisition is set for 10 minutes per temperature per scan.
Dmpc 1,2dimyristoyld54snglycero3phosphocholine is a lipid with a transition temperature tm 23 c. Lipid thermotropic phase transition database lipidat nist standard reference database 34 avanti polar lipids, inc. The apex of the curve corresponds to transition temperature, tt, and to maximal value of. A theoretical model for lipid mixtures, phase transitions, and phase. When lipids are brought into contact with water, the lyotropic phase either forms spontaneously at room temperature or the suspension must be sonicated or. Studies by dsc have shown, that the temperatures of the pretransition and the main phase transition of suvs of dppc are 28. Incubation of rna 10 with dmpc liposomes at molar ratio 1. Determination of the main phase transition temperature of.
Systematic characterization of dmpcdhpc selfassemblies and. Pressure perturbation calorimetry ppc is a new method that measures the heat consumed or released by a sample after a sudden pressure jump. Emergent properties of vesicles around the transition temperature dmpc 1,2dimyristoyld54snglycero3phosphocholine is a lipid with a transition temperature tm 23 c. Temperatureinduced micellevesicle transitions in dmpc. The transition temperature of dspc determined by dsc was inside this range 57,60.
Weve already seen one example of a phase transition in our discussion of boseeinstein condensation. Usually liposomes have low permeability to the encapsulated molecules unless the molecule is membrane permeable. Determination of phase transition temperatures of lipids by. In an orderdisorder phase transition all high temperature symmetries are preserved in the low temperature phase. Thermotropic phase behavior and headgroup interactions of the. Nov 12, 2003 the first 4252c transition is attributed to the main l. Download table phase transition temperatures and enthalpies for dmpc mlvs, suvs and slbs from publication. Phase transition in saltfree catanionic surfactant mixtures induced by temperature. At variance to what is observed for k ab 1, the dmpc lipid phase transition significantly modifies the thermodynamics associated with k ab 2 fig. Structural calorimetry of main transition of supported dmpc core. Influence of lipid composition on the phase transition. The ftir spectra of both vesicles show drastic frequency shifts of. The term phase transition or phase change is most commonly used to describe transitions between solid, liquid, and gaseous states of matter, as well as plasma in rare cases.
In the following we present further evidence for the unusual solidsolid phase transition via melting. The effect of a phase transition on single molecule tracks of annexin v in cushioned dmpc assemblies k. Alternative methods of determining phase transition. Effect of the dmpc phase transition on the second electron transfer. The various transition temperatures are characteristic for the lipid of which the.
Specific rna binding to ordered phospholipid bilayers. For pure dmpc liposomes, esr signal due to the probe dissolved in the fluid hydrophobic environment provided by the interior of the phospholipid bilayer lipid site is observed around 24c which corresponds to the main gel to liquid crystalline phase transition of pure dmpc liposomes. In both phases the lipid molecules are constrained to the two dimensional plane of the membrane, but in liquid phase bilayers the molecules diffuse freely within this plane. The shape alteration of supramolecular systems induced by the. Analysis of these spectra has led to the construction of a farnesoldmpcd 54 temperaturecomposition plot. Solidsolid phase transitions via melting in metals nature. Solidi cation of a liquid, in which the rotational freedom of the liquid is lost but the chemical coordination maintained, is a very common instance of an orderdisorder transition 31. Herein, we report a systematic characterization of dmpcdhpc assemblies at 20 c. Hydration pressure and phase transitions of phospholipids ii. Phase transition temperatures and enthalpies for dmpc mlvs. Application of pressure perturbation calorimetry to lipid.
Using dsc to characterize thermotropic phase transitions in lipid. What is the effect of the phase transition temperature of the. Solidsolid phase transitions via melting in metals. C, respectively, whereas the corresponding temperatures for. Besides a determination of the main transition temperature t 0 and the vant hoff transition enthalpy dh vh, the structural analysis in the nmscale at t close to t 0 of the ripple phase allowed an experimental. Investigation of temperatureinduced phase transitions in. The effect of a phase transition on single molecule tracks of. Apparently, bound rna interferes with, and lessens overall lipid cooperativity during the gelfluid conversion. In physical chemistry, any physically or chemically distinct, homogeneous, and.
Thus, the main phase transition temperature depending on hydrostatic pressure and hydration pressure is given by fig. Jan 01, 2006 various techniques have been proposed to specify the phase transition temperatures of surfactant molecules. Understanding why the ripple phase occurs has inspired much theory5 10 and some simulations. The transition temperature of dspc determined by dsc was inside this range. The phase transition temperature of the liposome can be controlled by adjusting the ratio of the compound phospholipid, which can enhance the stability of the liposome at 37 c and can reduce the. The 2nd experiment focuses on the changes of the hexagonal. The temperature is maintained at 30 c throughout the run. V, as a function of temperature and, in the case of phase transitions, the volume change. In the 1st experiment, the temperature is raised from room temperature to 210c and back to room temperature. Jialing li phase transition in lipid bilayers ethanols effect on miscibility transition temperature in ternary vesicles. Further, the transition temperature from gel to liquid crystal phase of dmpc has been determined and it is close to 297 k 30, what allows us to perform computer simulations able to be. The phasetransition temperature of dmpc from the gel to the fluid phase is. We show that increasing concentrations of farnesol induce a decrease in the fluidgel phase transition temperature and promote fluidgel coexistence.
Phase transitions a phase transition is an abrupt, discontinuous change in the properties of a system. Phase transition temperature an overview sciencedirect. A coupled protontransfer and twistingmotion fluorescence. In contrast to dmpc, however, dppc shows very little difference in the dsc behavior observed in buffers with and without nacl. All lipids have a characteristic temperature at which they undergo a transition from the gel to liquid phase. Pdf determination of the main phase transition temperature. At room temperature, heterogeneities arise on the membranes of dmpc vesicles from the coexistence of the lipid and gel phases 5. In each case one curve represents an expanded phase and one a condensed. The solid phase is commonly referred to as a gel phase. The dmpc lipid phase transition influences differently the. Phase transition temperatures determined by dsc measurements were 25. The first 4252c transition is attributed to the main l. Phase transition temperatures for glycerophospholipids references thermotropic phase transitions of pure lipids in model membranes and their modifications by membrane proteins, dr. Phase transition in lipid bilayers ethanols effect on miscibility.
Chapter 5 structural and phase transition classi cation. The heat change can be used to derive the thermal volume expansion coefficient. Phase transitions of lipid bilayers universiteit van amsterdam. Phase transition temperature definition of phase transition. The phase transition temperature is defined as the temperature required to induce a change in the lipid physical state from the ordered gel phase, where the hydrocarbon chains are fully extended and closely packed, to the disordered liquid crystalline phase, where the hydrocarbon chains are randomly oriented and fluid. These peaks cover all relevant functional groups in the investigated lipids. The gel to liquidcrystalline phase transition temperature tm was. Mar 10, 2009 the temperature scale is set by matching the temperatures of the phase transitions of the gel phase to the ripple phase t p and the ripple phase to the liquid phase t m with the corresponding experimental phase transition temperatures of pure dmpc. Also in contrast to dmpc, in dppc there is no observable difference in the phase transition temperature in the three different solutions, that is, the phase transition occurs at 41. Phase transition temperatures for glycerophospholipids. In that case, we had to look fairly closely to see the discontinuity. To investigate the phase behavior, optical density od 500, size by dynamic light scattering, membrane fluidity 1 p dph using 1,6diphenyl1,3,5hexatriene, and membrane polarity gp 340 using 6dodecanoyl n, n dimethyl2naphthylamine were measured as a.
Lipids, phase transitions of ta b l e 2 decrease of the gelliquidcrystalline l. The slope shows that the pressureinduced temperature increase a is the same for hydrostatic pressure and for hydration pressure. Mar, 2011 physicochemical properties of liposomes depend on many factors such as ionic strength, ph and temperature. Change in compressibility as a function of temperature due to the presence of drug in the dmpc monolayer a away from lelc phase transition and b near lelc phase transition. During a phase transition of a given medium, certain properties of the medium. An approximate cooperativity analysis by dsc of phase. Investigation of phase transitions of saturated phosphocholine lipid. Main phase transitions in supported lipid singlebilayer. Temperature dependent results were mathematically treated by plotting the fluorescence anisotropy versus temperature t and by fitting eq. To determine the distribution of the probe between the aqueous and the lipid phases, large unilamellar vesicles of dmpc were used. The muchcited vist and davis 1990 phase diagram proposes gel and lo phase coexistence for mole fraction of chol xchol from 0.1509 1289 1211 1197 411 96 1621 678 1651 495 421 1632 1186 550 47 63 766 159 917 271 960 1027 566 159 855 1382 1021 1515 171 461 458 682 1126 526 1352 215 1227 916 1060 311 226 1397