scholarly journals The Formation and Properties of Thin Lipid Membranes from HK and LK Sheep Red Cell Lipids

1967 ◽  
Vol 50 (6) ◽  
pp. 1729-1749 ◽  
Author(s):  
Thomas E. Andreoli ◽  
J. Andrew Bangham ◽  
Daniel C. Tosteson
Keyword(s):  
Lipid Membranes ◽  
Transference Number ◽  
Cholesterol Content ◽  
Membrane Voltage ◽  
Transference Numbers ◽  
Molar Ratio ◽  
Membrane Thickness ◽  
High Potassium ◽  
Cation Selectivity ◽  
High Degree

Lipids were obtained from high potassium (HK) and low potassium (LK) sheep red cells by sequential extraction of the erythrocytes with isopropanol-chloroform, chloroform-methanol-0.1 M KCl, and chloroform. The extract contained cholesterol and phospholipid in a molar ratio of 0.8:1.0, and less than 1% protein contaminant. Stable thin lipid membranes separating two aqueous compartments were formed from an erythrocyte lipid-hydrocarbon solution, and had an electrical resistance of ∼108 ohm-cm2 and a capacitance of 0.38–0.4 µf/cm2. From the capacitance values, membrane thickness was estimated to be 46–132 A, depending on the assumed value for the dielectric constant (2.0–4.5). Membrane voltage was recorded in the presence of ionic (NaCl and/or KCl) concentration gradients in the solutions bathing the membrane. The permeability of the membrane to Na+, K+, and Cl- (expressed as the transference number, Tion) was computed from the steady-state membrane voltage and the activity ratio of the ions in the compartments bathing the membrane. TNa and TK were approximately equal (∼0.8) and considerably greater than TCl (∼0.2). The ionic transference numbers were independent of temperature, the hydrocarbon solvent, the osmolarity of the solutions bathing the membranes, and the cholesterol content of the membranes, over the range 21–38°C. The high degree of membrane cation selectivity was tentatively attributed to the negatively charged phospholipids (phosphatidylethanolamine and phosphatidylserine) present in the lipid extract.

scholarly journals The Interaction of Polyene Antibiotics with Thin Lipid Membranes

1968 ◽  
Vol 52 (2) ◽  
pp. 300-325 ◽  
Author(s):  
Thomas E. Andreoli ◽  
Marcia Monahan
Keyword(s):  
Amphotericin B ◽  
Lipid Membranes ◽  
Sheep Erythrocyte ◽  
Cholesterol Content ◽  
Transference Numbers ◽  
Ionic Selectivity ◽  
Antibiotic Concentration ◽  
Polyene Antibiotics ◽  
Cyclic Polyene ◽  
Membrane Bound

Optically black, thin lipid membranes prepared from sheep erythrocyte lipids have a high dc resistance (Rm ≅ 108 ohm-cm2) when the bathing solutions contain NaCl or KCl. The ionic transference numbers (Ti) indicate that these membranes are cation-selective (TNa ≅ 0.85; TCl ≅ 0.15). These electrical properties are independent of the cholesterol content of the lipid solutions from which the membranes are formed. Nystatin, and probably amphotericin B, are cyclic polyene antibiotics containing ≈36 ring atoms and a free amino and carboxyl group. When the lipid solutions used to form membranes contained equimolar amounts of cholesterol and phospholipid, these antibiotics reduced Rm to ≈102 ohm-cm2; concomitantly, TCl became ≅0.92. The slope of the line relating log Rm and log antibiotic concentration was ≅4.5. Neither nystatin (2 x 10-5 M) nor amphotericin B (2 x 10-7 M) had any effect on membrane stability. The antibiotics had no effect on Rm or membrane permselectivity when the lipids used to form membranes were cholesterol-depleted. Filipin (10-5 M), an uncharged polyene with 28 ring atoms, produced striking membrane instability, but did not affect Rm or membrane ionic selectivity. These data suggest that amphotericin B or nystatin may interact with membrane-bound sterols to produce multimolecular complexes which greatly enhance the permeability of such membranes for anions (Cl-, acetate), and, to a lesser degree, cations (Na+, K+, Li+).

scholarly journals The Effect of Valinomycin on the Ionic Permeability of Thin Lipid Membranes

1967 ◽  
Vol 50 (11) ◽  
pp. 2527-2545 ◽  
Author(s):  
Thomas E. Andreoli ◽  
M. Tieffenberg ◽  
Daniel C. Tosteson
Keyword(s):  
Lipid Membranes ◽  
Membrane Resistance ◽  
Monovalent Cation ◽  
Solvation Shell ◽  
Ionic Concentration ◽  
Transference Numbers ◽  
Red Cell ◽  
Concentration Gradients ◽  
Cation Selectivity ◽  
Cyclic Depsipeptide

Optically black membranes prepared from sheep red cell lipids have a high electrical resistance (1–3 x 108 ohm-cm2). The ionic transference numbers (Ti) for cations (Na+ or K+) are equal to each other but at least four to five times greater than for Cl-. The cyclic depsipeptide valinomycin produces a striking decrease in the membrane resistance when K+, but not when Na+ is in the solutions bathing the membrane. The ratio TNa/TK, estimated from membrane voltages in the presence of ionic concentration gradients, approaches zero. The order of membrane monovalent cation selectivity, in the presence of valinomycin, is H+ > Rb+ > K+ > Cs+ > Na+. Addition of the antibiotic to one side of a membrane which separates identical solutions of NaCl produces a substantial (up to 80 mV) membrane voltage (side opposite valinomycin negative). These data are consistent with the hypothesis that valinomycin can interact with appropriately sized cations (hydrated diameter ??? 6 A) to increase their membrane permeability, perhaps by forming hydrogen bonds between the solvation shell of the cations and carbonyl oxygens in the valinomycin molecule which are directed toward the aperture of the ring.

On the Properties of an Ion Conductive System Incorporated in Hybrid Films

2000 ◽  
Vol 628 ◽  
Author(s):  
G. González ◽  
P. J. Retuert ◽  
S. Fuentes
Keyword(s):  
Electrochemical Impedance ◽  
Ternary Phase Diagram ◽  
Lithium Perchlorate ◽  
Molar Ratio ◽  
Ionic Conductors ◽  
X Ray Diffraction ◽  
Poly Ethylene Oxide ◽  
Ion Conducting ◽  
Poly Ethylene ◽  
High Degree

ABSTRACTBlending the biopolymer chitosan (CHI) with poly (aminopropilsiloxane) oligomers (pAPS), and poly (ethylene oxide) (PEO) in the presence of lithium perchlorate lead to ion conducting products whose conductivity depends on the composition of the mixture. A ternary phase diagram for mixtures containing 0.2 M LiClO4 shows a zone in which the physical properties of the products - transparent, flexible, mechanically robust films - indicate a high degree of molecular compatibilization of the components. Comparison of these films with binary CHI-pAPS nanocomposites as well as the microscopic aspect, thermal behavior, and X-ray diffraction pattern of the product with the composition PEO/CHI/pAPS/LiClO4 1:0.5:0.6:0.2 molar ratio indicates that these films may be described as a layered nanocomposite. In this composite, lithium species coordinated by PEO and pAPS should be inserted into chitosan layers. Electrochemical impedance spectroscopy measurements indicate the films are pure ionic conductors with a maximal bulk conductivity of 1.7*10-5 Scm-1 at 40 °C and a sample-electrode interface capacitance of about 1.2*10-9 F.

scholarly journals Effect of the cholesterol content of small unilamellar liposomes on their stability in vivo and in vitro

1980 ◽  
Vol 186 (2) ◽  
pp. 591-598 ◽  
Author(s):  
Christopher Kirby ◽  
Jacqui Clarke ◽  
Gregory Gregoriadis
Keyword(s):  
Blood Plasma ◽  
Intravenous Injection ◽  
Whole Blood ◽  
Cholesterol Content ◽  
Molar Ratio ◽  
Phosphatidylcholine Liposomes ◽  
Effective Use ◽  
Positively Charged

Small unilamellar neutral, negatively and positively charged liposomes composed of egg phosphatidylcholine, various amounts of cholesterol and, when appropriate, phosphatidic acid or stearylamine and containing 6-carboxyfluorescein were injected into mice, incubated with mouse whole blood, plasma or serum or stored at 4°C. Liposomal stability, i.e. the extent to which 6-carboxyfluorescein is retained by liposomes, was dependent on their cholesterol content. (1) Cholesterol-rich (egg phosphatidylcholine/cholesterol, 7:7 molar ratio) liposomes, regardless of surface charge, remained stable in the blood of intravenously injected animals for up to at least 400min. In addition, stability of cholesterol-rich liposomes was largely maintained in vitro in the presence of whole blood, plasma or serum for at least 90min. (2) Cholesterol-poor (egg phosphatidylcholine/cholesterol, 7:2 molar ratio) or cholesterol-free (egg phosphatidylcholine) liposomes lost very rapidly (at most within 2min) much of their stability after intravenous injection or upon contact with whole blood, plasma or serum. Whole blood and to some extent plasma were less detrimental to stability than was serum. (3) After intraperitoneal injection, neutral cholesterol-rich liposomes survived in the peritoneal cavity to enter the blood circulation in their intact form. Liposomes injected intramuscularly also entered the circulation, although with somewhat diminished stability. (4) Stability of neutral and negatively charged cholesterol-rich liposomes stored at 4°C was maintained for several days, and by 53 days it had declined only moderately. Stored liposomes retained their unilamellar structure and their ability to remain stable in the blood after intravenous injection. (5) Control of liposomal stability by adjusting their cholesterol content may help in the design of liposomes for effective use in biological systems in vivo and in vitro.

Low-temperature route to nanoscale P3N5 hollow spheres

2003 ◽  
Vol 18 (10) ◽  
pp. 2359-2363 ◽  
Author(s):  
Hongzhou Gu ◽  
Yunle Gu ◽  
Zhefeng Li ◽  
Yongcheng Ying ◽  
Yitai Qian
Keyword(s):  
Photoelectron Spectroscopy ◽  
Hollow Spheres ◽  
Molar Ratio ◽  
Visible Absorption ◽  
X Ray ◽  
Transmission Electron ◽  
Influence Of Temperature On ◽  
Wide Gap ◽  
20 Nm ◽  
High Degree

Nanoscale hollow spheres of amorphous phosphorus nitride (P3N5) were synthesized by reacting PCl3 with NaN3 at 150–250 °C. Transmission electron microscope images show that the hollow spheres have a diameter of 150–350 nm, and the thickness of the shell is 20 nm. A very small amount of curly films were also found in the sample prepared at 150 °C. The infrared spectrum indicates a high degree of purity. X-ray photoelectron spectroscopy indicates the presence of P and N, with a molar ratio of 1:1.62 for P:N. Ultraviolet-visible absorption spectroscopy shows an absorption band at 265–315 nm. Under photoluminescent excitation at 230 nm, the P3N5 emits ultraviolet light at 305 nm. With a band gap of 4.28 eV, the products may be a wide gap semiconductor. A possible mechanism and the influence of temperature on the formation of the hollow spheres are also discussed.

Electronic/Ionic Conductivity and Oxygen Diffusion Coefficient af the Sr-Fe-Co-O System

1995 ◽  
Vol 393 ◽  
Author(s):  
B. Ma ◽  
J.-H. Park ◽  
C. U. Segre ◽  
U. Balachandran
Keyword(s):  
Diffusion Coefficient ◽  
Ionic Conductivity ◽  
Oxygen Diffusion ◽  
Ionic Conductivities ◽  
Transference Number ◽  
Transference Numbers ◽  
Oxygen Diffusion Coefficient ◽  
Ionic Transference Number ◽  
Local Fitting ◽  
Oxide Ion

ABSTRACTOxides in the Sr-Fe-Co-O system exhibit both electronic and ionic conductivities. Recently, the Sr-Fe-Co-O system attracted great attention because of its potential to be used for oxygen-permeable membranes that can operate without electrodes or external electrical circuitry. Electronic and ionic conductivities of two compositions of the Sr-Fe-Co-O system, named SFC-1 and SFC-2, have been measured at various temperatures. The electronic transference number is much greater than the ionic transference number in SFC-1, whereas the electronic and ionic transference numbers are very similar in SFC-2. At 800°C, the electronic and ionic conductivities are ≈76 and ≈4 S•cm−1, respectively, for SFC-1; whereas, for SFC-2, the electronic and ionic conductivities are ≈10 and ∼1 S•cm−1, respectively. By performing a local fitting to the equation σ • T = Aexp(-Ea / kT), we found that the oxide ion activation energies are 0.92 and 0.37 eV, respectively, for SFC-1 and SFC-2. The oxygen diffusion coefficient of SFC-2 is ≈ 9 x 10−7cm2/sec at 900°C.

CHEMICAL METHOD FOR THE DETERMINATION OF URINARY ALDOSTERONE

1957 ◽  
Vol 35 (1) ◽  
pp. 425-443 ◽  
Author(s):  
Wojciech Nowaczynski ◽  
Erich Koiw ◽  
Jacques Genest
Keyword(s):  
Normal Subjects ◽  
Ultraviolet Absorption ◽  
Anxiety State ◽  
High Potassium ◽  
High Sodium ◽  
Pregnancy Anxiety ◽  
Potassium Intake ◽  
High Degree ◽  
Sodium And Potassium

A new method of purification of crude neutral extracts of urine for the isolation and determination of aldosterone is presented. The specificity and accuracy of the method depend upon the high degree of purity of the aldosterone isolated. The assertion that the substance isolated is aldosterone is based on the mobilities in the three chromatographic systems used, on the typical ultraviolet absorption curve, on the satisfactory agreement between the values obtained by ultraviolet absorption and by blue tetrazolium reaction, and by the typical chromogen spectra in concentrated sulphuric acid and in 100% phosphoric acid. Values obtained in nine normal subjects on ordinary diets vary from 2.2 to 10 μg. per day with a mean of 5.1. Illustrations of results obtained during pregnancy, anxiety state, and periods of high potassium and combined high sodium and potassium intake are presented.

scholarly journals Measuring Children’s Sodium and Potassium Intakes in NZ: A Pilot Study

Nutrients ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 1198 ◽  
Author(s):  
Helen Eyles ◽  
Neela Bhana ◽  
Sang Lee ◽  
Carley Grimes ◽  
Rachael McLean ◽  
...  
Keyword(s):  
Sodium Intake ◽  
Urine Samples ◽  
Alcoholic Beverages ◽  
Food Sources ◽  
Molar Ratio ◽  
High Potassium ◽  
Frequent Use ◽  
Recall Data ◽  
Diet Recall ◽  
Sodium And Potassium

Low sodium and high potassium intakes in childhood protect against rises in blood pressure (BP) and risk of cardiovascular disease (CVD) later in life. Our aim was to pilot methods for collection of 24-h urine samples (gold standard) and diet recalls to assess sodium and potassium intakes and their food sources in 30 children aged 8–11 years at one New Zealand primary school. A diverse sample (n = 27) was recruited over a two-week period. All children provided a urine sample (71% complete) and interviewer-assisted 24-h diet recall (Intake24 software). Median (range) sodium intake was 2191 (1087 to 4786) mg/day (salt equivalent 5.5 g), potassium intake was 1776 (800–2981) mg/day, BP was 105 (84–129)/62 (53–89) mmHg, and sodium to potassium molar ratio was 2.0 (1.1–4.8). Frequent use of discretionary salt was uncommon. Major food sources of sodium were bread, pies and pastries, and bread and pasta-based dishes, and potassium were sauces and condiments, dairy products, and non-alcoholic beverages. Most participants provided adequate data and enjoyed taking part. A larger survey is warranted to confirm findings and inform a potential intervention(s). Small improvements to study procedures and resources should improve completeness of urine samples and quality of 24-h diet recall data.

Partitioning of caffeine in lipid bilayers reduces membrane fluidity and increases membrane thickness

2017 ◽  
Vol 19 (10) ◽  
pp. 7101-7111 ◽  
Author(s):  
Adree Khondker ◽  
Alexander Dhaliwal ◽  
Richard J. Alsop ◽  
Jennifer Tang ◽  
Matilda Backholm ◽  
...  
Keyword(s):  
Membrane Fluidity ◽  
Lipid Bilayers ◽  
Lipid Membranes ◽  
Membrane Thickness

Caffeine partitions in lipid membranes in the head to tail interface and leads to a thickening and defluidification.

Electro-osmosis and hydrogen-ion transport in cation-exchange membranes

1967 ◽  
Vol 20 (12) ◽  
pp. 2575 ◽  
Author(s):  
R Arnold ◽  
DA Swift
Keyword(s):  
Ion Transport ◽  
Cation Exchange ◽  
Acid Concentration ◽  
Water Flux ◽  
Transference Number ◽  
Hydrogen Ion ◽  
Transference Numbers ◽  
Transport Numbers ◽  
Electro Osmosis ◽  
Hydrogen Ion Transport

Hydrogen-ion transport numbers, water transference numbers, and acid absorption are reported for some cation-exchange membranes in presence of 0.1N, 1.0N, and 5.0N sulphuric acid. The transport numbers of hydrogen ion remain fairly close to unity even at the highest acid concentration; this is largely due to the retardation of the anions by the electro-osmotic water flux. With increasing acid concentration the water transference number falls to a lower limit of 1.0 mole per faraday; with the driest membrane used this value is obtained at all acid concentrations used. This behaviour suggests that when there are less than about 11 moles of water available per hydrogen ion in the membrane, association occurs between sulphonate groups and hydrogen ions, with consequent immobilization of the latter.

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