Thermodynamics of mixing of dipalmitoyl phosphatidylcholine and egg phosphatidylcholine in hydrated bilayers

1982 ◽  
Vol 60 (5) ◽  
pp. 538-548 ◽  
Author(s):  
David O. Tinker ◽  
Rosita Low
Keyword(s):  
Molar Volume ◽  
Liquid Crystalline ◽  
Binary Solution ◽  
Empirical Relationship ◽  
Mixing Enthalpy ◽  
Aqueous Mixtures ◽  
Scanning Calorimetry ◽  
Dipalmitoyl Phosphatidylcholine ◽  
Transition Enthalpy ◽  
Egg Pc

Dipalmitoyl phosphatidylcholine (DPPC) and egg phosphatidylcholine (egg PC) are not completely miscible at all temperatures. Their phase diagram was determined by differential scanning calorimetry (DSC) of aqueous mixtures of the two. From the integrated DSC curves we obtained the enthalpy of solution of DPPC in egg PC, Δhs, as a function of the mole fraction of DPPC, X, and using the empirical relationship between Δhs and X, the solubility Xsat as a function of temperature, T. The latter could be described by the semiempirical relationship:RlnXsat = a + blnT – c/T, where a = 6.57 × 10−2 kcal∙mol−1∙degree−1 and c = 20.5 kcal∙mol−1 (1 cal = 4.1868 J); the coefficient b was very small and could be ignored. The quantity Δhs can be given as XΔhDPPC + Δhmix, where ΔhDPPC is the gel – liquid crystalline transition enthalpy of DPPC (8.74 kcal∙mol−1) and Δhmix is the enthalpy of mixing the two liquid crystalline lipids. Δhmix depends on X in approximately a parabolic fashion, having a maximal value of 4.8 kcal∙mol−1 at X = 0.6.It was shown that both the solubility and mixing enthalpy data can be described by the theory of regular solutions (RST). In RST, the activity coefficient of the solute (component 2) of a binary solution is given by RTlnγ2 = (1 − θ2)2ΔU, while the mixing enthalpy is given by Δhmix = θ1θ2 ΔU/v2, where θ1 and θ2 are the volume fractions of solvent and solute (egg PC and DPPC, respectively), v2 is the partial molar volume of DPPC, and ΔU is the energy change per mole on interchanging a DPPC and an egg PC molecule between their respective liquid crystalline phases. The thermodynamic data are accurately described by RST, the molar volume of DPPC being found to be about half mat of egg PC solution and the interchange energy ΔU having a value of 10–11 kcal∙mol−1. There was some evidence that ΔU may be an increasing function of temperature. The large value of the ΔU accounts for the pronounced temperature dependence of the solubility Xsat, which decreases from 0.35 at 35 °C to 0.02 at 10 °C.The presence of cholesterol in the mixtures decreases both the transition enthalpy of DPPC and the mixing enthalpy in a linear fashion, so that Δhs is zero at Xcholesterol ≥ 0.2. The results are consistent with recent data indicating the formation of a PC–cholesterol complex of stoichiometry approximately 4:1.

Studies on the purified Na+,Mg2+-ATPase from Acholeplasma laidlawii B membranes: a differential scanning calorimetric study of the protein–phospholipid interactions

1990 ◽  
Vol 68 (1) ◽  
pp. 161-168 ◽  
Author(s):  
Rajan George ◽  
Ruthven N.A.H. Lewis ◽  
Ronald N. McElhaney
Keyword(s):  
Phase Transition ◽  
Liquid Crystalline ◽  
Lipid Phase ◽  
Scanning Calorimetry ◽  
Lipid Phase Transition ◽  
Acholeplasma Laidlawii ◽  
Lipid Ratios ◽  
Dimyristoyl Phosphatidylcholine ◽  
Transition Enthalpy ◽  
Crystalline Phase Transition

The purified Na+, Mg2+-ATPase from the Acholeplasma laidlawii B plasma membrane was reconstituted with dimyristoyl phosphatidylcholine and the lipid thermotropic phase behavior of the proteoliposomes formed was investigated by differential scanning calorimetry. The effect of this ATPase on the host lipid phase transition is markedly dependent on the amount of protein incorporated. At low protein/lipid ratios, the presence of increasing quantities of ATPase in the proteoliposomes increases the temperature and enthalpy while decreasing the cooperativity of the dimyristoyl phosphatidylcholine gel to liquid–crystalline phase transition. At higher protein/lipid ratios, the incorporation of increasing amounts of this enzyme does not further alter the temperature and cooperativity of the phospholipid chain-melting transition, but progressively and markedly decreases the transition enthalpy. Plots of lipid phase transition enthalpy versus protein concentration suggest that at the higher protein/lipid ratios each ATPase molecule removes approximately 1000 dimyristoyl phosphatidylcholine molecules from participation in the cooperative gel to liquid–crystalline phase transition of the bulk lipid phase. These results indicate that this integral transmembrane protein interacts in a complex, concentration-dependent manner with its host phospholipid and that such interactions involve both hydrophobic interactions with the lipid bilayer core and electrostatic interactions with the lipid polar head groups at the bilayer surface.Key words: Acholeplasma laidlawii B, Na+,Mg2+-ATPase, differential scanning calorimetry, lipid-protein interactions.

Reconstitution of the glycosylphosphatidylinositol-anchored protein Thy-1: interaction with membrane phospholipids and galactosylceramide

1999 ◽  
Vol 77 (3) ◽  
pp. 189-200 ◽  
Author(s):  
Kara L Reid-Taylor ◽  
Joseph WK Chu ◽  
Frances J Sharom
Keyword(s):  
Phase Transition ◽  
Differential Scanning Calorimetry ◽  
Lipid Bilayer ◽  
Liquid Crystalline ◽  
Membrane Surface ◽  
Membrane Phospholipids ◽  
Scanning Calorimetry ◽  
Transition Enthalpy ◽  
Striking Change ◽  
Lipid Bilayer Vesicles

Glycosylphosphatidylinositol (GPI)-anchored membrane proteins are proposed to interact preferentially with glycosphingolipids and cholesterol to form microdomains, which may play an important role in apical targeting and signal transduction. The objective of the present study was to investigate the interaction of the GPI-anchored protein Thy-1 with phospholipids and a glycosphingolipid. Purified Thy-1 was reconstituted into lipid bilayer vesicles of dimyristoyl-phosphatidylcholine (DMPC) alone or in combination with galactosylceramide (GC). The ability of Thy-1 to perturb the gel to a liquid-crystalline phase transition of DMPC was examined by differential scanning calorimetry. As the mole fraction of Thy-1 increased, the phase transition enthalpy, deltaH, declined. Analysis indicated that each molecule of Thy-1 perturbed over 50 phospholipids, suggesting that, in addition to the anchor insertion into the bilayer, the protein itself may interact with the membrane surface. Inclusion of 5% w/w GC in the bilayer resulted in a striking change in the interaction of Thy-1 with phospholipids. At low Thy-1 content, there was a reduction in the phase transition temperature and an increase in phospholipid cooperativity, suggesting the formation of Thy-1/GC-enriched domains. deltaH initially decreased with increasing Thy-1 content of the bilayer; however, at higher Thy-1 mole ratios, deltaH rose again. These results are interpreted in terms of a model whereby, at low protein:lipid mole ratios, Thy-1 preferentially sequesters GC to form enriched microdomains. At high protein:lipid mole ratios, Thy-1 may alter its conformation in response to steric crowding within these domains such that its interaction with the bilayer surface is reduced.Key words: glycosylphosphatidylinositol anchor, Thy-1 antigen, reconstitution, lipid bilayer, glycosphingolipid, differential scanning calorimetry, dynamic light scattering.

Mixtures of semisynthetic species of cerebroside sulfate with dipalmitoyl phosphatidylcholine. Thermotropic phase behavior and permeability

1990 ◽  
Vol 68 (1) ◽  
pp. 70-82 ◽  
Author(s):  
J. M. Boggs ◽  
D. Mulholland ◽  
K. M. Koshy
Keyword(s):  
Differential Scanning Calorimetry ◽  
Crystalline Phase ◽  
Spin Label ◽  
Liquid Crystalline ◽  
Water Soluble ◽  
Liquid Crystalline Phase ◽  
Low Permeability ◽  
Scanning Calorimetry ◽  
Dipalmitoyl Phosphatidylcholine ◽  
Gel Phase

The phase behavior of mixtures of dipalmitoyl phosphatidylcholine (DPPC) with semisynthetic species of cerebroside sulfate (CBS) containing palmitic acid (C16:0-CBS) or lignoceric acid (C24:0-CBS) in 0.1 M KCl was studied using differential scanning calorimetry. DPPC and C16:0-CBS were miscible in all proportions in the gel phase above 10 mol% CBS and in the liquid-crystalline phase. However, C24:0-CBS was less miscible with DPPC over a wide concentration range in the gel phase. At high CBS concentrations it was probably also not entirely miscible with DPPC in the liquid-crystalline phase. Small amounts of both species of CBS lowered the transition temperature and enthalpy of DPPC, suggesting that they are more soluble in the liquid-crystalline phase of DPPC than the gel phase. The transition temperature at higher CBS concentrations was also less than expected, especially after cycling through the phase transition in the case of C24:0-CBS, suggesting that mixing with DPPC inhibited the intermolecular hydrogen bonding interactions and dehydration of CBS. In C24:0-CBS–DPPC mixtures several populations were present over a wide compositional range, including two solid-solid solutions of fixed composition. At high C24:0-CBS concentrations some C24:0-CBS also phase separated out of the mixture. Structural considerations suggested that the C24:0-CBS which is mixed with DPPC must be interdigitated into the DPPC bilayer. Other populations that are present may have a different structural organization. A fatty acid spin label in these mixtures was a little less ordered than in either lipid by itself. The permeability of these lipids, as well as the two asymmetric species 1-stearoyl-2-caproyl phosphatidylcholine and 1-stearoyl-2-myristoyl phosphatidylcholine (18:10PC and 18:14PC), to a water-soluble spin label tempocholine chloride was also measured. The studies with 18:10PC and 18:14PC indicated that both triple-chain mixed interdigitated bilayers and double-chain partially interdigitated bilayers can trap water-soluble substances and have low permeability. Both species of CBS could also entrap the spin label and had low permeability at 4 °C. However, they rapidly lost the entrapped compound when they transformed into their stable dehydrated phases or into the liquid-crystalline phase. Mixing with DPPC prevented both of these losses. These studies supported the conclusion that a significant amount of the CBS was mixed with the DPPC and that this mixing prevented the dehydration changes which CBS undergoes by itself. They also suggested that the C24:0-CBS can pack with the DPPC in the liquid-crystalline phase in a regular way which must involve inter-digitation of the long C24:0 chain into the DPPC bilayer.Key words: sulfatide, phosphatidylcholine, phase diagram, differential scanning calorimetry, interdigitated bilayer.

Electron microscopy of crystalline structure in thermotropic random copolymers

1991 ◽  
Vol 49 ◽  
pp. 1054-1055
Author(s):  
Afzana Anwer ◽  
S. Eilidh Bedford ◽  
Richard J. Spontak ◽  
Alan H. Windle
Keyword(s):  
Electron Microscopy ◽  
Crystalline Structure ◽  
Liquid Crystalline ◽  
Elevated Temperatures ◽  
Random Copolymers ◽  
Molecular Characteristics ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Identical Monomer ◽  
Periodic Layer

Random copolyesters composed of wholly aromatic monomers such as p-oxybenzoate (B) and 2,6-oxynaphthoate (N) are known to exhibit liquid crystalline characteristics at elevated temperatures and over a broad composition range. Previous studies employing techniques such as X-ray diffractometry (XRD) and differential scanning calorimetry (DSC) have conclusively proven that these thermotropic copolymers can possess a significant crystalline fraction, depending on molecular characteristics and processing history, despite the fact that the copolymer chains possess random intramolecular sequencing. Consequently, the nature of the crystalline structure that develops when these materials are processed in their mesophases and subsequently annealed has recently received considerable attention. A model that has been consistent with all experimental observations involves the Non-Periodic Layer (NPL) crystallite, which occurs when identical monomer sequences enter into register between adjacent chains. The objective of this work is to employ electron microscopy to identify and characterize these crystallites.

Electron microscopy and diffraction of crystalline dendrimers and macrocycles

1993 ◽  
Vol 51 ◽  
pp. 1218-1219
Author(s):  
C. J. Buchko ◽  
P. M. Wilson ◽  
Z. Xu ◽  
J. Zhang ◽  
S. Lee ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Liquid Crystalline ◽  
Structural Information ◽  
High Resolution Electron Microscopy ◽  
Scanning Calorimetry ◽  
Tertiary Butyl ◽  
Phenyl Acetylene ◽  
Selected Area Electron Diffraction ◽  
Liquid Crystalline Phases ◽  
Resolution Electron

The synthesis of well-defined organic molecules with unique geometries opens new opportunities for understanding and controlling the organization of condensed matter. Here, we study dendrimers and macrocycles which are synthesized from rigid phenyl-acetylene spacer units, Both units are solubilized by the presence of tertiary butyl groups located at the periphery of the molecule. These hydrocarbon materials form crystalline and liquid crystalline phases which have been studied by differential scanning calorimetry, hot stage optical microscopy, and wide-angle x-ray scattering (WAXS).The precisely defined architecture of these molecules makes it possible to investigate systematic variations in chemical architecture on the nature of microstructural organization. Here we report on the transmission electron microscopy (TEM), selected area electron diffraction (SAED), and high resolution electron microscopy (HREM) studies of crystalline thin films formed by deposition of these materials onto carbon substrates from dilute solution. Electron microscopy is very attractive for gaining structural information on new molecules due to the scarcity of material to grow single crystals suitable for conventional crystallography.

scholarly journals Optical investigations and photoactive solar energy applications of new synthesized Schiff base liquid crystal derivatives

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Fowzia S. Alamro ◽  
Sobhi M. Gomha ◽  
Mohamed Shaban ◽  
Abeer S. Altowyan ◽  
Tariq Z. Abolibda ◽  
...  
Keyword(s):  
Solar Energy ◽  
Liquid Crystalline ◽  
Molecular Structures ◽  
Light Illumination ◽  
Electrical Measurements ◽  
Scanning Calorimetry ◽  
Energy Applications ◽  
Meta Position ◽  
Chain Group ◽  
Liquid Crystalline Materials

AbstractNew homologues series of liquid crystalline materials namely, (E)-3-methoxy-4-[(p-tolylimino)methyl]phenyl 4-alkloxybenzoates (I-n), were designed and evaluated for their mesomorphic and optical behavior. The prepared series constitutes three members that differ from each other by the terminally attached alkoxy chain group, these vary between 6 and 12 carbons. A laterally OCH3 group is incorporated into the central benzene ring in meta position with respect to the ester moiety. Mesomorphic characterizations of the prepared derivatives are conducted using differential scanning-calorimetry (DSC), polarized optical-microscopy (POM). Molecular structures were elucidated by elemental analyses and NMR spectroscopy. DSC and POM investigations revealed that all the synthesized derivatives are purely nematogenic exhibiting only nematic (N) mesophase, except for the longest chain derivative (I-12) that is dimorphic possesses smectic A and N phases. Moreover, all members of the group have a wide mesomorphic range with high thermal nematic stability. A comparative study was established between the present derivative (I-6) and their previously prepared isomer. The results indicated that the location exchange of the polar compact group (CH3) influences the N mesophase stability and range. The electrical measurements revealed that all synthesized series I-n show Ohmic behaviors with effective electric resistances in the GΩ range. Under white light illumination, the effective electric conductivity for the compound I-8 is five times that obtained in dark conditions. This derivative also showed two direct optical band gaps in the UV and visible light range. In addition, I-6 has band energy gaps of values 1.07 and 2.79 eV, which are suitable for solar energy applications.

Liquid crystalline polyureas with oligo(ethylene glycol) sequences

e-Polymers ◽  
2010 ◽  
Vol 10 (1) ◽  
Author(s):  
Shahram Mehdipour-Ataei ◽  
Leila Akbarian-Feizi
Keyword(s):  
Liquid Crystalline ◽  
Spectroscopic Method ◽  
Polymerization Reaction ◽  
X Ray Diffraction ◽  
Subsequent Reaction ◽  
Scanning Calorimetry ◽  
Polar Solvents ◽  
X Ray ◽  
H Nmr ◽  
Ft Ir

AbstractA diamine monomer containing ester, amide and ether functional groups was prepared and its polymerization reaction with different diisocyanates to give main chain poly(ester amide ether urea)s was investigated. The monomer was synthesized via reaction of terephthaloyl chloride with 4-hydroxybenzoic acid and subsequent reaction of the resulted diacid with 1,8-diamino-3,6-dioxaoctane. The polymers were characterized by FT-IR and 1H-NMR spectroscopic method and elemental analysis. The resulting polymers exhibited excellent solubility in polar solvents. Crystallinity of the resulted polymers was evaluated by wide-angle X-ray diffraction (WXRD) method, and they exhibited semi-crystalline patterns. The glass transition temperatures (Tg) of the polymers determined by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) were in the range of 88-112 °C. The temperatures for 10% weight loss (T10) from their thermogravimetric analysis (TGA) curves were found to be in the range of 297-312 °C in air. Also the prepared polyureas showed liquid crystalline character.

Thermal, Mechanical and Magneto-Mechanical Characterization of Liquid Crystalline Elastomers Loaded with Iron Oxide Nanoparticles

2015 ◽  
Vol 1718 ◽  
pp. 3-7
Author(s):  
Stephany Herrera-Posada ◽  
Barbara O. Calcagno ◽  
Aldo Acevedo
Keyword(s):  
Iron Oxide ◽  
Iron Oxide Nanoparticles ◽  
Liquid Crystalline ◽  
Molar Mass ◽  
Oxide Nanoparticles ◽  
Magnetic Actuation ◽  
Scanning Calorimetry ◽  
Elastomeric Matrix ◽  
Alternating Magnetic Fields

ABSTRACTLiquid crystalline elastomers (LCEs) are materials that reveal unusual mechanical, optical and thermal properties due to their molecular orientability characteristic of low molar mass liquid crystals while maintaining the mechanical elasticity distinctive of rubbers. As such, they are considered smart shape-changing responsive systems. In this work, we report on the preparation of magnetic sensitized nematic LCEs using iron oxide nanoparticles with loadings of up to 0.7 wt%. The resultant thermal and mechanical properties were characterized by differential scanning calorimetry, expansion/contraction experiments and extensional tests. The magnetic actuation ability was also evaluated for the neat elastomer and the composite with 0.5 wt% magnetic content, finding reversible contractions of up to 23% with the application of alternating magnetic fields (AMFs) of up to 48 kA/m at 300 kHz. Thus, we were able to demonstrate that the inclusion of magnetic nanoparticles yields LCEs with adjustable properties that can be tailored by changing the amount of particles embedded in the elastomeric matrix, which can be suitable for applications in actuation, sensing, or as smart substrates.

Synthesis and Properties of Thermotropic Liquid Crystalline Polyesters with Flexible Polymethylene Spacer

2010 ◽  
Vol 428-429 ◽  
pp. 126-131
Author(s):  
Wei Zhong Lu ◽  
Chun Wei ◽  
Qui Shan Gao
Keyword(s):  
Optical Microscopy ◽  
Liquid Crystalline ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Structure Morphology ◽  
Temperature Ranges ◽  
Ft Ir ◽  
Diffraction Peaks ◽  
Ubbelohde Viscometer

Polymethylene bis(p-hydroxybenzoates) were prepared from methyl p-hydroxybenzoate and different diols by melted transesterification reaction. Three liquid crystalline polyesters were synthesized from terephthaloyl dichloride and polymethylene bis(p-hydroxybenzoates). Its structure, morphology and properties were characterized by Ubbelohde viscometer, Fourier transform infrared spectroscopy (FT-IR), Differential scanning calorimetry (DSC), polarized optical microscopy (POM) with a hot stage, and wide-angle X-ray diffraction (WAXD). Results indicated that the intrinsic viscosities were between 0.088 and 0.210 dL/g. Optical microscopy showed that the TLCP has a highly threaded liquid crystalline texture and a high birefringent schlieren texture character of nematic phase and has wider mesophase temperature ranges for all polyesters. DSC analysis were found that the melting point (Tm), isotropic temperature (Ti) of TLCPs decreased and the temperature range of the liquid crystalline phase became wider with increased number of methylene spacers in the polyester. The WAXD results showed that TLCPs owned two strong diffraction peaks at 2θ near 19° and 23°.

scholarly journals Synthesis and mesomorphic properties of calamitic malonates and cyanoacetates tethered to 4-cyanobiphenyls

2012 ◽  
Vol 8 ◽  
pp. 371-378 ◽  
Author(s):  
Katharina C Kress ◽  
Martin Kaller ◽  
Kirill V Axenov ◽  
Stefan Tussetschläger ◽  
Sabine Laschat
Keyword(s):  
Differential Scanning Calorimetry ◽  
Ambient Temperature ◽  
Liquid Crystalline ◽  
X Ray Diffraction ◽  
Cyanoacetic Acid ◽  
Scanning Calorimetry ◽  
Isotropic Liquid ◽  
X Ray ◽  
Nematic Phases ◽  
Mesomorphic Properties

4-Cyano-1,1'-biphenyl derivatives bearing ω-hydroxyalkyl substituents were reacted with methyl 3-chloro-3-oxopropionate or cyanoacetic acid, giving liquid-crystalline linear malonates and cyanoacetates. These compounds formed monotropic nematic phases at 62 °C down to ambient temperature upon cooling from the isotropic liquid. The mesomorphic properties were investigated by differential scanning calorimetry, polarizing optical microscopy and X-ray diffraction (WAXS).

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