scholarly journals The analysis of intermolecular interactions in concentrated hyaluronan solutions suggest no evidence for chain–chain association

2000 ◽  
Vol 350 (1) ◽  
pp. 329-335 ◽  
Author(s):  
Phillip GRIBBON ◽  
Boon Chin HENG ◽  
Timothy E. HARDINGHAM
Keyword(s):  
Fluorescence Recovery After Photobleaching ◽  
Hydrodynamic Radius ◽  
Hydrophobic Interactions ◽  
Lateral Diffusion ◽  
Tracer Diffusion ◽  
Dilute Solution ◽  
Concentrated Solutions ◽  
Chain Flexibility ◽  
Self Diffusion ◽  
Confocal Fluorescence

Confocal fluorescence recovery after photobleaching (confocal-FRAP) was used to examine the influence of electrolytes (NaCl, KCl, MgCl2, MnCl2 and CaCl2) on the network and hydrodynamic properties of fluoresceinamine-labelled hyaluronan (FA-HA) at concentrations up to 10mg/ml. Self and tracer lateral diffusion coefficients showed that in Ca2+ and Mn2+, FA-HA (830kDa) was more compact than in Mg2+, Na+ or K+. These results were correlated with changes in the hydrodynamic radius of HA, determined by multi-angle laser-light-scattering analysis in dilute solution, which was smaller in CaCl2 (36nm) than in NaCl (43nm). The permeability of more concentrated solutions of HA (< 10mg/ml) to FITC-dextran tracers (2000kDa) was higher in CaCl2. The properties of HA in urea (up to 6M) were investigated to test for hydrophobic interactions and also in ethanol/water (up to 62%, v/v). In both, there was reduced hydrodynamic size and increased permeability to FITC-dextran, suggesting increased chain flexibility, but it did not show the changes predicted if chain–chain association was disrupted by urea, or enhanced by ethanol. Oligosaccharides of HA (HA20–26) also had no effect on the self diffusion of high-molecular-mass FA-HA (830kDa) solutions, or on dextran tracer diffusion, showing that there were no chain–chain interactions open to competition by short-chain segments. The results suggest that the effects of electrolytes and solvent are determined primarily by their effect on HA chain flexibility, with no evidence for association between chain segments contributing significantly to the major properties.

Self-diffusion of Ag+ and Na+ in molten Ca(NO3)2-KNO3

1972 ◽  
Vol 25 (8) ◽  
pp. 1613 ◽  
Author(s):  
BJ Welch ◽  
CA Angell
Keyword(s):  
Electrical Conductance ◽  
Ionic Species ◽  
Tracer Diffusion ◽  
Dilute Solution ◽  
Self Diffusion ◽  
Capillary Method ◽  
Arrhenius Temperature Dependence ◽  
Radio Tracer ◽  
Tracer Diffusion Coefficients ◽  
Arrhenius Temperature

In order to explore the behaviour of diffusing ionic species in a molten salt in which non-Arrhenius behaviour of other transport properties is established, the diffusivities in dilute solution of Ag+ and Na+ in 38.1 mol% Ca(NO3)2+ 61.9 mol% KNO3 have been measured. For both ions limited radio-tracer diffusion coefficients, determined using a diffusion-out-of-capillary method, are reported. D(Ag+) has also been measured by chronopotentiometry, by which means the range and reliability of the measurements were considerably extended. Chronopotentiometric and tracer data agree within expected errors of measurement. Both ionic diffusivities show a non-Arrhenius temperature dependence which is indistinguishable in magnitude from that of the electrical conductance of the solvent melt.

Lateral Mobility of Integrin αIIbβ3 (Glycoprotein IIb/IIIa) in the Plasma Membrane of a Human Megakaryocyte

1997 ◽  
Vol 77 (01) ◽  
pp. 143-149 ◽  
Author(s):  
Annelies Schootemeijer ◽  
Gijsbert van Willigen ◽  
Hans van der Vuurst ◽  
Leon G J Tertoolen ◽  
Siegfried W De Laat ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Fluorescence Recovery After Photobleaching ◽  
Cell Activation ◽  
Lateral Diffusion ◽  
Cytochalasin D ◽  
Lag Phase ◽  
Integrin Αiibβ3 ◽  
Cell Matrix ◽  
Cytoplasmic Actin ◽  
Mobile Fraction

SummaryThe migration of integrins to sites of cell-cell and cell-matrix contact is thought to be important for adhesion strengthening. We studied the lateral diffusion of integrin αIIbβ3 (glycoprotein Ilb/IIIa) in the plasma membrane of a cultured human megakaryocyte by fluorescence recovery after photobleaching of FITC-labelled monovalent Fab fragments directed against the P3 subunit. The diffusion of P3 on the unstimulated megakaryocyte showed a lateral diffusion coefficient (D) of 0.37 X10'9 cm2/s and a mobile fraction of about 50%. Stimulation with ADP (20 μM) or α-thrombin (10 U/ml) at 22° C induced transient decreases in both parameters reducing D to 0.21 X 10‘9 cm2/s and the mobile fraction to about 25%. The fall in D was observed within 1 min after stimulation but the fall in mobile fraction showed a lag phase of 5 min. The lag phase was absent in the presence of Calpain I inhibitor, whereas cytochalasin D completely abolished the decrease in mobile fraction. The data are compatible with the concept that cell activation induces anchorage of 50% of the mobile αIIbβ3 (25% of the whole population of receptor) to the cytoplasmic actin filaments, although, as discussed, other rationals are not ruled out.

Some Considerations on Confined Water: The Thermal Behavior of Transport Properties in Water-Glycerol and Water-Methanol Mixtures

MRS Advances ◽  
2016 ◽  
Vol 1 (26) ◽  
pp. 1891-1902 ◽  
Author(s):  
Francesco Mallamace ◽  
Carmelo Corsaro ◽  
Domenico Mallamace ◽  
Cirino Vasi ◽  
Sebastiano Vasi ◽  
...  
Keyword(s):  
Hydrophobic Interactions ◽  
Molar Fraction ◽  
Relaxation Times ◽  
Confined Water ◽  
Self Diffusion ◽  
Excess Value ◽  
Water Glycerol ◽  
System Properties ◽  
Dynamical Crossover

ABSTRACTWe discuss recent literature data on the relaxation times (the primary tα), viscosity, and self-diffusion in water-glycerol and water-methanol mixtures across a wide temperature range from the stable water phase to the deep supercooled regime (373–147K). In particular, to clarify the role of hydrophilicity interactions (the hydrogen bonds) and hydrophobic interactions we study the mixture in terms of the water molar fraction (XW) with fixed temperatures at 5K steps across the entire composition range, and we find a marked deviation from the ideal thermodynamic behavior of the transport functions. This deviation is strongly T and XW dependent and spans values that range from two orders of magnitude at the highest temperature to more than five in the deeply supercooled regime (more precisely, at ≃200K). We analyze these deviations in terms of how the measured values differ from ideal values and find that the hydrogen-bonding water network dominates system properties up to XW = 0.3. We also examine an Arrhenius plot of the maximum excess value (Δtα(T) vs. 1/T) and find two significant changes due to water: one at the dynamical crossover temperature (TL ≃ 225K, i.e., the locus of the Widom line), and one at T ≃ 315K (the water isothermal compressibility χT minimum).

scholarly journals The lateral diffusion of lipid probes in the surface membrane of Schistosoma mansoni.

1986 ◽  
Vol 103 (3) ◽  
pp. 807-818 ◽  
Author(s):  
M Foley ◽  
A N MacGregor ◽  
J R Kusel ◽  
P B Garland ◽  
T Downie ◽  
...  
Keyword(s):  
Schistosoma Mansoni ◽  
Fluorescence Recovery After Photobleaching ◽  
Surface Membrane ◽  
Biological Significance ◽  
Lateral Diffusion ◽  
Asymmetric Distribution ◽  
Normal Surface ◽  
Membrane Blebs ◽  
Fluorescent Lipids ◽  
Fluorescent Lipid Analogues

The technique of fluorescence recovery after photobleaching was used to measure the lateral diffusion of fluorescent lipid analogues in the surface membrane of Schistosoma mansoni. Our data reveal that although some lipids could diffuse freely others exhibited restricted lateral diffusion. Quenching of lipid fluorescence by a non-permeant quencher, trypan blue, showed that there was an asymmetric distribution of lipids across the double bilayer of mature parasites. Those lipids that diffused freely were found to reside mainly in the external monolayer of the outer membrane whereas lipids with restricted lateral diffusion were located mainly in one or more of the monolayers beneath the external monolayer. Formation of surface membrane blebs allowed us to measure the lateral diffusion of lipids in the membrane without the influence of underlying cytoskeletal structures. The restricted diffusion found on the normal surface membrane of mature parasites was found to be released in membrane blebs. Quenching of fluorescent lipids on blebs indicated that all probes were present almost entirely in the external monolayer. Juvenile worms exhibited lower lateral diffusion coefficients than mature parasites: in addition, the lipids partitioned into the external monolayer. The results are discussed in terms of membrane organization, cytoskeletal contacts, and biological significance.

Lithium tracer diffusion in near stoichiometric LiNi0.5Mn1.5O4 cathode material for lithium-ion batteries

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Daniel Uxa ◽  
Harald Schmidt
Keyword(s):  
Cathode Material ◽  
Secondary Ion Mass Spectrometry ◽  
Lithium Ion ◽  
Tracer Diffusion ◽  
Side Reactions ◽  
Battery Materials ◽  
Self Diffusion ◽  
Thermally Activated ◽  
Average Grain Size ◽  
And Migration

Abstract The compound LiNi0.5Mn1.5O4 is used as novel cathode material for Li-ion batteries and represents a variant to replace conventional LiMn2O4. For a further improvement of battery materials it is necessary to understand kinetic processes at and in electrodes and the underlying diffusion of lithium that directly influences charging/discharging times, maximum capacities, and possible side reactions. In the present study Li tracer self-diffusion is investigated in polycrystalline sintered bulk samples of near stoichiometric LiNi0.5Mn1.5O4 with an average grain size of about 50–70 nm in the temperature range between 250 and 600 °C. For analysis, stable 6Li tracers are used in combination with secondary ion mass spectrometry (SIMS). The tracer diffusivities can be described by the Arrhenius law with an activation enthalpy of (0.97 ± 0.05) eV, which is interpreted as the sum of the formation and migration energy of a thermally activated Li vacancy.

scholarly journals Diffusion in phospholipid bilayer membranes: dual-leaflet dynamics and the roles of tracer–leaflet and inter-leaflet coupling

2014 ◽  
Vol 470 (2167) ◽  
pp. 20130843 ◽  
Author(s):  
Reghan J. Hill ◽  
Chih-Ying Wang
Keyword(s):  
Lateral Diffusion ◽  
Bilayer Membrane ◽  
Tracer Diffusion ◽  
Phospholipid Bilayer ◽  
Supported Membranes ◽  
Bilayer Membranes ◽  
Lubrication Film ◽  
Lipid Assemblies ◽  
Slip Coefficients ◽  
Made In

A variety of observations—sometimes controversial—have been made in recent decades when attempting to elucidate the roles of interfacial slip on tracer diffusion in phospholipid membranes. Evans–Sackmann theory (1988) has furnished membrane viscosities and lubrication-film thicknesses for supported membranes from experimentally measured lateral diffusion coefficients. Similar to the Saffman and Delbrück model, which is the well-known counterpart for freely supported membranes, the bilayer is modelled as a single two-dimensional fluid. However, the Evans–Sackman model cannot interpret the mobilities of monotopic tracers, such as individual lipids or rigidly bound lipid assemblies; neither does it account for tracer–leaflet and inter-leaflet slip. To address these limitations, we solve the model of Wang and Hill, in which two leaflets of a bilayer membrane, a circular tracer and supports are coupled by interfacial friction, using phenomenological friction/slip coefficients. This furnishes an exact solution that can be readily adopted to interpret the mobilities of a variety of mosaic elements—including lipids, integral monotopic and polytopic proteins, and lipid rafts—in supported bilayer membranes.

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