scholarly journals Concentration dependent different action of progesterone on the order, dynamics and hydration states of the head group of dipalmitoyl-phosphatidylcholine membrane

2005 ◽  
Vol 19 (4) ◽  
pp. 213-219 ◽  
Author(s):  
Filiz Korkmaz ◽  
Halil Kirbiyik ◽  
Feride Severcan
Keyword(s):  
Liquid Crystalline ◽  
Membrane Dynamics ◽  
Head Group ◽  
Interfacial Region ◽  
Progesterone Concentration ◽  
Dramatic Decrease ◽  
Physiological Level ◽  
Dipalmitoyl Phosphatidylcholine ◽  
Multilamellar Liposomes ◽  
Linear Plot

Interactions of progesterone with zwitterionic dipalmitoyl phosphatidylcholine (DPPC) multilamellar liposomes (MLVs) were investigated as a function of progesterone concentration at selected temperatures monitoring both the gel and liquid crystalline phase, by using Fourier Transform Infrared spectroscopy (FTIR). It has been show that the effect of progesterone on membrane dynamics is dependent on progesterone concentration. At 1 mol%, which is close to physiological level, progesterone behaves differently. At this concentration the decrease in dynamics is more noticeable. Additionally a dramatic decrease in the strength of hydrogen bonding in the interfacial region of the bilayer is also observed. When concentration increases up to 12 mol% opposite behaviour is observed at all interactions. Above 12 mol%, progesterone–DPPC interactions shows almost linear plot.

scholarly journals Infrared Spectroscopic Studies on the Dipalmitoyl Phosphatidylcholine Bilayer Interactions with Calcium Phosphate: Effect of Vitamin D2

2002 ◽  
Vol 16 (3-4) ◽  
pp. 399-408 ◽  
Author(s):  
Neslihan Toyran ◽  
Feride Severcan
Keyword(s):  
Vitamin D ◽  
Calcium Phosphate ◽  
Liquid Crystalline ◽  
Spectroscopic Studies ◽  
The Body ◽  
Head Group ◽  
Dipalmitoyl Phosphatidylcholine ◽  
Major Structural Component ◽  
Ftir Spectral Analysis ◽  
Acyl Chains

In the present work, the interaction of calcium-phosphate with DPPC (dipalmitoyl phosphatidylcholine) model membranes has been studied in the presence and absence of vitamin D2by using Fourier Transform Infrared (FTIR) spectroscopy. Calcium and phosphorus are the most abundant elements in the body. They combine in the form of calcium phosphate salt, called hydroxyapatite. Hydroxyapatite is the major structural component of the bone. Calcium phosphate assists with the digestion and absorption of food and is vitally important for the building of sturdy bone and body structures and a robust constitution. Phosphorus is extracted from foods and its use is controlled by vitamin D and calcium. FTIR spectral analysis results suggested that, calcium–phosphate complex, which is the major component of the bones, decreases the phase transition temperature to lower values, causes a loss in cooperativity of the acyl chains, decreases the order of the membrane in both phases and decreases the dynamics of the membrane in the liquid crystalline phase, increases the flexibility of the chains in the center of the bilayer in both phases, and increases the mobility of the head group of DPPC in the gel phase. The effect of calcium-phosphate on DPPC liposomes diminishes with the addition of vitamin D2into the liposomes. Our results suggest how calcium-phosphate and/or vitamin D2, which have indispensable role for the functioning of the bone tissue, affect the thermal behaviour of DPPC liposomes at molecular level.

scholarly journals Vitamin D2at high and low concentrations exert opposing effects on molecular order and dynamics of dipalmitoyl phosphatidylcholine membranes

2001 ◽  
Vol 15 (2) ◽  
pp. 47-55 ◽  
Author(s):  
Nadide Kazanci ◽  
Neslihan Toyran ◽  
Parvez I. Haris ◽  
Feride Severcan
Keyword(s):  
Phase Transition ◽  
Vitamin D ◽  
Spectroscopic Studies ◽  
Membrane Dynamics ◽  
Transition Curve ◽  
Interfacial Region ◽  
High Concentration ◽  
Dipalmitoyl Phosphatidylcholine ◽  
Low Concentrations ◽  
High Concentrations

Fourier Transform Infrared spectroscopic studies show that low concentrations of vitamin D2(1 and 3 mol %) does not induce significant change in the overall shape of the thermotropic profile of dipalmitoyl phosphatidylcholine (DPPC) membrane. In contrast, at higher concentrations of vitamin D2(9 and 12 mol %), the phase transition shifts to lower temperatures and a significant broadening in the phase transition curve is also observed. Low concentration of vitamin D2decreases the frequency of the CH2stretching mode, implying an ordering effect, whilst high concentration of vitamin D2disorders the system. Furthermore, at low and high concentrations, vitamin D2causes opposing effect on membrane dynamics. It decreases the bandwidth of the CH2stretching modes at low concentrations while increasing it at high concentrations. We have also observed different actions of vitamin D2at low and high concentrations in the deep interior and interfacial region of the membrane, by monitoring the frequency of the CH3stretching band and C=O stretching bands, respectively.

Effect of Inhalation Anesthetics on Spin-Labeled Cholesterol Containing DPPC Vesicles

1988 ◽  
Vol 43 (3-4) ◽  
pp. 264-268 ◽  
Author(s):  
N. Gulfo ◽  
R. Bartucci ◽  
L. Sportelli
Keyword(s):  
Phase Transition ◽  
Diethyl Ether ◽  
Liquid Crystalline ◽  
Main Phase ◽  
Molar Ratio ◽  
Lipid Phase ◽  
Interfacial Region ◽  
Hydrophobic Core ◽  
Hydrophobic Region ◽  
Inhalation Anesthetics

We have investigated by means of electron spin resonance (ESR) spectroscopy the influence of three inhalation anesthetics, i.e. halothane, chloroform and diethyl ether, on the interfacial and hydrophobic region as well of 38 mol% cholesterol containing DPPC unilamellar vesicles. The study has been carried out in the temperature range 25-45 °C. The variation of the order parameter, S, vs temperature of the lipid phase indicates that with this content of cholesterol the characteristic gel → liquid crystalline main phase transition of DPPC, normally occurring at Tt ~ 41 °C, disappears. When halothane and chloroform are added to the vesicles suspension up to [DPPC]/[anesthetic] molar ratio of 1:1 the main phase transition, as detected with the stearic acid spin label I(12,3), reappears again and it results down shifted at Tt ~ 35 and 39 °C, respectively. In presence of diethyl ether, instead, the main phase transition is not observable also at the highest concentration of anesthetic used. Moreover, halothane and chloroform affect similarly the hydrophobic core of cholesterol-!- DPPC vesicles which, in turn, results to be different from the action exerted by diethyl ether in the same region. The ESR findings are discussed in terms of competitive effects shown by cholesterol and inhalation anesthetics. Moreover, the interfacial region of CHOL + DPPC vesicles results to be the target of anesthetics.

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.

scholarly journals Tamoxifen Increases Membrane Fluidity at High Concentrations

2000 ◽  
Vol 20 (3) ◽  
pp. 177-184 ◽  
Author(s):  
Feride Severcan ◽  
Nadide Kazanci ◽  
Faruk Zorlu
Keyword(s):  
Fourier Transform ◽  
Membrane Fluidity ◽  
Crystalline Phase ◽  
Liquid Crystalline ◽  
Fourier Transform Infrared ◽  
Membrane Dynamics ◽  
Liquid Crystalline Phase ◽  
Lipid Fluidity ◽  
Lipid Order ◽  
High Concentrations

There are contradictory results in the literature relating to the effect oftamoxifen on membrane fluidity. The present work investigates the effect oftamoxifen on membrane dynamics to find out whether the concentration oftamoxifen can be one of the factors in this discrepancy. Turbidity(absorbance at 440 nm) and Fourier transform infrared spectroscopicstudies reveal that tamoxifen causes opposite effects on membranefluidity at low (1 mol.%) and high (30 mol.%) tamoxifen concentrations. Lowtamoxifen concentrations increase the absorbance in the gel and liquidcrystalline phase, whereas high tamoxifen concentrations decrease theabsorbance in gel and liquid crystalline phase, whereas tamoxifenconcentrations decrease the absorbance. Observations on both phasesshow that the bandwidth of the CH2 stretching bands decreases with1 mol.% tamoxifen and increases with 30 mol.% tamoxifen present, indicatinga decrease in membrane fluidity at low tamoxifen concentrations and anincrease in fluidity at high tamoxifen concentrations. It is seen that theapparent discrepancy in the literature on the effect of tamoxifen onmembrane fluidity mainly arises from the tamoxifen concentration used andthe confusion on the concept of lipid fluidity and lipid order.

scholarly journals Lipid conformation in model membranes and biological membranes

1980 ◽  
Vol 13 (1) ◽  
pp. 19-61 ◽  
Author(s):  
Joachim Seelig ◽  
Anna Seelig
Keyword(s):  
Liquid Crystalline ◽  
Double Helix ◽  
Liquid Paraffin ◽  
Biological Membranes ◽  
Fatty Acyl ◽  
Head Group ◽  
Exact Nature ◽  
Polar Head Group ◽  
Acyl Chains ◽  
Lipid Conformation

Protein molecules in solution or in protein crystals are characterized by rather well-defined structures in which α-helical regions, β-pleated sheets, etc., are the key features. Likewise, the double helix of nucleic acids has almost become the trademark of molecular biology as such. By contrast, the structural analysis of lipids has progressed at a relatively slow pace. The early X-ray diffraction studies by V. Luzzati and others firmly established the fact that the lipids in biological membranes are predominantly organized in bilayer structures (Luzzati, 1968). V. Luzzati was also the first to emphasize the liquid-like conformation of the hydrocarbon chains, similar to that of a liquid paraffin, yet with the average orientation of the chains perpendicular to the lipid–water interface. This liquid–crystalline bilayer is generally observed in lipid–water systems at sufficiently high temperature and water content, as well as in intact biological membranes under physiological conditions (Luzzati & Husson, 1962; Luzzati, 1968; Tardieu, Luzzati & Reman, 1973; Engelman, 1971; Shipley, 1973). In combination with thermodynamic and other spectroscopic observations these investigations culminated in the formulation of the fluid mosaic model of biological membranes (cf. Singer, 1971). However, within the limits of this model the exact nature of lipid conformation and dynamics was immaterial, the lipids were simply pictured as circles with two squiggly lines representing the polar head group and the fatty acyl chains, respectively. No attempt was made to incorporate the well-established chemical structure into this picture. Similarly, membrane proteins were visualized as smooth rotational ellipsoids disregarding the possibility that protruding amino acid side-chains and irregularities of the backbone folding may create a rather rugged protein surface.

Kinetics of hydrolysis of dispersions of saturated phosphatidylcholines by Crotalus atrox phospholipase A2

1978 ◽  
Vol 56 (6) ◽  
pp. 552-558 ◽  
Author(s):  
David O. Tinker ◽  
A. David Purdon ◽  
Jane Wei ◽  
Eileen Mason
Keyword(s):  
Liquid Crystalline ◽  
Phase Reaction ◽  
Reaction Products ◽  
Crotalus Atrox ◽  
Dipalmitoyl Phosphatidylcholine ◽  
Desorption Rate Constant ◽  
Rate Of Hydrolysis ◽  
Lag Period ◽  
Lipid Surface ◽  
Hydrolysis Of

Dispersions of lamellar phase dipalmitoyl phosphatidylcholine (DDPC) and dimyristoyl phosphatidylcholine (DMPC) in 0.01 M CaCl2 were subjected to hydrolysis by phospholipase A2 (EC 3.1.1.4) from Crotalus atrox venom. The reaction was followed continuously by titrating the released fatty acids. For hydrolysis of gel phase phosphatides, the steady-state initial velocities were hyperbolic functions of bulk lipid concentrations. At the 'pre-transition' temperature (34 °C for DPPC, 15 °C for DMPC), there was a large increase in the Michaelis parameter Vmax but no change in the parameter Km. A model was devised to account for these observations, in which the enzyme desorbs from the lipid surface after hydrolysis. The desorption rate constant is postulated to increase above the pretransition temperature.For hydrolysis of liquid crystalline phosphatides, the reaction consisted of a short initial burst of hydrolysis, a long 'lag' period of very slow reaction, followed by a dramatic increase in the reaction rate. Addition of 10 mol% lysolecithin or fatty acid abolished the 'lag' period. It was postulated that the enzyme adsorbs irreversibly to the surface of the liquid crystalline phase. Reaction products are postulated to stimulate desorption of enzyme from the surface. Thus, temperature-dependent changes in the rate of hydrolysis of dispersed phosphatidylcholines are attributed to changes in the rate of desorption of the enzyme from the lipid surface.

Liposome fixation by UV polymerization

1984 ◽  
Vol 42 ◽  
pp. 36-37
Author(s):  
Joseph A. Zasadzinski
Keyword(s):  
Lipid Bilayers ◽  
Electron Scattering ◽  
Liquid Crystalline ◽  
Osmium Tetroxide ◽  
Water Soluble ◽  
Head Group ◽  
Ammonium Iodide ◽  
Conjugated Diene ◽  
Structure And Morphology ◽  
New Type

In standard dehydration and epoxy embedding of biological material, substantial portions of lipid are extracted. In addition, the mechanisms of lipid fixation by osmium tetroxide are either unknown or poorly understood. Liposomes, particles of lamellar liquid crystalline lipid in water, react immediately with osmium, but are not preserved and the bulk of the lipid is removed in subsequent processing. Several authors heve attempted to improve lipid retention by using water-soluble embedding media, various dehydration techniques, etc., with varying degrees of success. The structure and morphology of the lipid bilayers in tissue or in liposomes remains open to question. To deal with these problems, a new type of lipid which can be polymerized was developed. The synthetic lipid, N,N dimethyl, di(ethoxycarbonyl-2,4-hexadecadienyl)ammonium iodide, DDEAI, incorporates a polymerizable conjugated diene moeity in each tail of the molecule. The counterion in the head group is iodide, which provides a strong, yet localized electron scattering site which precludes the need for other stains (Fig. 1.).

scholarly journals Elastic scattering studies of aligned DMPC multilayers on different hydrations1

2010 ◽  
Vol 24 (5) ◽  
pp. 461-466 ◽  
Author(s):  
Marcus Trapp ◽  
Fanni Juranyi ◽  
Moeava Tehei ◽  
Lambert van Eijck ◽  
Bruno Demé ◽  
...  
Keyword(s):  
Group Dynamics ◽  
Alkyl Chain ◽  
Structural Phase ◽  
Dynamical Behaviour ◽  
Membrane Dynamics ◽  
Phase Behaviour ◽  
Head Group ◽  
Chain Defects ◽  
Bilayered Structure ◽  
Influence Of Hydration

Biological membranes, consisting mainly of phospholipids and proteins, are organized in a bilayered structure which exhibits dynamical behaviour within time regimes ranging from 10–12s with the motion of alkyl chain defects and 1 s corresponding to collective excitations of the bilayer [Europhysics Letters8(1989), 201–206]. With the prominent role hydration plays on the structural phase behaviour of phospholipids membranes, it is essential for a better description of membranes to understand also the influence of hydration on the dynamics of membrane systems. In the present study we have performed neutron scattering investigations on highly oriented DMPC-d54 multilayers at two different relative humidity (rh) levels. Our results reveal the strong influence of hydration on the local membrane dynamics, i.e., head group dynamics.

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