Slow dynamics of interfacial water

1995 ◽  
Vol 73 (11-12) ◽  
pp. 703-709 ◽  
Author(s):  
S.-H. Chen ◽  
P. Gallo ◽  
M.-C. Bellissent-Funel
Keyword(s):  
Translational Motion ◽  
Diffusion Constant ◽  
Alternative Interpretation ◽  
Slow Dynamics ◽  
Vycor Glass ◽  
Self Diffusion ◽  
Slowing Down ◽  
Incoherent Neutron Scattering ◽  
Deuterated Protein ◽  
Short Time

The highlights of our recent high-resolution quasi-elastic incoherent neutron: scattering studies of the translational dynamics of water molecules contained in the micropores of Vycor glass and on the surface of a deuterated protein are summarized. The incoherent quasi-elastic spectra from the confined H2O are first analyzed by a confined diffusion model to obtain the elastic incoherent structure factor (EISF), the short-time self-diffusion constant (D), and the probability per unit time for a jump (1/τ0) as functions of the surface coverage and temperature. The effect of the confinement on the slowing down of the translational motion is discussed. An alternative interpretation of the slow dynamics based on a molecular mechanism of a cage effect and an approach to the kinetic glass transition is put forth.

scholarly journals Salt-Induced Universal Slowing Down of the Short-Time Self-Diffusion of a Globular Protein in Aqueous Solution

2015 ◽  
Vol 6 (13) ◽  
pp. 2577-2582 ◽  
Author(s):  
Marco Grimaldo ◽  
Felix Roosen-Runge ◽  
Marcus Hennig ◽  
Fabio Zanini ◽  
Fajun Zhang ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Globular Protein ◽  
Self Diffusion ◽  
Slowing Down ◽  
Short Time

scholarly journals Water and Deuterium Oxide Permeability through Aquaporin 1: MD Predictions and Experimental Verification

2007 ◽  
Vol 130 (1) ◽  
pp. 111-116 ◽  
Author(s):  
Artem B. Mamonov ◽  
Rob D. Coalson ◽  
Mark L. Zeidel ◽  
John C. Mathai
Keyword(s):  
Deuterium Oxide ◽  
Diffusion Constant ◽  
Structural Data ◽  
Md Simulations ◽  
Water Model ◽  
Aquaporin 1 ◽  
Self Diffusion ◽  
Osmotic Permeability ◽  
Protein Channels ◽  
And Diffusion

Determining the mechanisms of flux through protein channels requires a combination of structural data, permeability measurement, and molecular dynamics (MD) simulations. To further clarify the mechanism of flux through aquaporin 1 (AQP1), osmotic pf (cm3/s/pore) and diffusion pd (cm3/s/pore) permeability coefficients per pore of H2O and D2O in AQP1 were calculated using MD simulations. We then compared the simulation results with experimental measurements of the osmotic AQP1 permeabilities of H2O and D2O. In this manner we evaluated the ability of MD simulations to predict actual flux results. For the MD simulations, the force field parameters of the D2O model were reparameterized from the TIP3P water model to reproduce the experimentally observed difference in the bulk self diffusion constants of H2O vs. D2O. Two MD systems (one for each solvent) were constructed, each containing explicit palmitoyl-oleoyl-phosphatidyl-ethanolamine (POPE) phospholipid molecules, solvent, and AQP1. It was found that the calculated value of pf for D2O is ∼15% smaller than for H2O. Bovine AQP1 was reconstituted into palmitoyl-oleoyl-phosphatidylcholine (POPC) liposomes, and it was found that the measured macroscopic osmotic permeability coefficient Pf (cm/s) of D2O is ∼21% lower than for H2O. The combined computational and experimental results suggest that deuterium oxide permeability through AQP1 is similar to that of water. The slightly lower observed osmotic permeability of D2O compared to H2O in AQP1 is most likely due to the lower self diffusion constant of D2O.

scholarly journals Diffusion in the aqueous compartment.

1984 ◽  
Vol 99 (1) ◽  
pp. 180s-187s ◽  
Author(s):  
A M Mastro ◽  
A D Keith
Keyword(s):  
Rotational Motion ◽  
Spin Label ◽  
Mammalian Cells ◽  
Translational Motion ◽  
Diffusion Constant ◽  
Rotational Correlation Time ◽  
Model Systems ◽  
Quiescent Cells ◽  
Spin Resonance ◽  
In Cells

Measurements of diffusion of molecules in cells can provide information about cytoplasmic viscosity and structure. In a series of studies electron-spin resonance was used to measure the diffusion of a small spin label in the aqueous cytoplasm of mammalian cells. Translational and rotational motion were determined from the same spectra. Based on measurements made in model systems, it was hypothesized that calculations of the apparent viscosity of the cytoplasm from both rotational and translational motion would distinguish between the effects of viscosity and structure on diffusion. The diffusion constant measured in several cell lines averaged 3.3 X 10(-6) cm2/s. It was greater in growing cells and in cells treated with cytochalasin B than in quiescent cells. The viscosity of the cytoplasm calculated from the translational diffusion constant or the rotational correlation time was 2.0-3.0 centipoise, about two to three times that of the spin label in water. Therefore, over the dimensions measured by the technique, 50-100 A, solvent viscosity appears to be the major determinant of particle movement in cells under physiologic conditions. However, when cells were subjected to hypertonic conditions, the translational motion of the spin label decreased threefold, whereas the rotational motion changed by less than 20%. These data suggest that the decrease in cell volume under hypertonic conditions is accompanied by an increase in cytoplasmic barriers and a decrease in the space between existing cytoplasmic components without a significant increase in viscosity in the aqueous phase. In addition, a comparison of reported diffusion values of a variety of molecules in water and in cells indicates that cytoplasmic structure plays an important role in the diffusion of proteins such as bovine serum albumin.

scholarly journals Experimental Implications of Negative Quantum Conditional Entropy—H2 Mobility in Nanoporous Materials

2020 ◽  
Vol 10 (22) ◽  
pp. 8266
Author(s):  
C. Aris Chatzidimitriou-Dreismann
Keyword(s):  
Information Theory ◽  
Translational Motion ◽  
Conditional Entropy ◽  
Classical Case ◽  
Quantum Thermodynamics ◽  
Incoherent Neutron Scattering ◽  
Quantum Conditional Entropy ◽  
Del Rio ◽  
Incoherent Neutron ◽  
Fictitious Particle

During the last few decades, considerable advances in quantum information theory have shown deep existing connections between quantum correlation effects (like entanglement and quantum discord) and thermodynamics. Here the concept of conditional entropy plays a considerable role. In contrast to the classical case, quantum conditional entropy can take negative values. This counter-intuitive feature, already well understood in the context of information theory, was recently shown theoretically to also have a physical meaning in quantum thermodynamics [del Rio et al. Nature 2011, 474, 61]. Extending this existing work, here we provide evidence of the significance of negative conditional entropy in a concrete experimental context: Incoherent Neutron Scattering (INS) from protons of H2 in nano-scale environments; e.g., in INS from H2 in C-nanotubes, the data of the H2 translational motion along the nanotube axis seems to show that the neutron apparently scatters from a fictitious particle with mass of 0.64 atomic mass units (a.m.u.)—instead of the value of 2 a.m.u. as conventionally expected. An independent second experiment confirms this finding. However, taking into account the possible negativity of conditional entropy, we explain that this effect has a natural interpretation in terms of quantum thermodynamics. Moreover, it is intrinsically related to the number of qubits capturing the interaction of the two quantum systems H2 and C-nanotube. The considered effect may have technological applications (e.g., in H-storage materials and fuel cells).

Self-diffusion of a molecule in porous Vycor glass

1986 ◽  
Vol 56 (2) ◽  
pp. 197-200 ◽  
Author(s):  
W. D. Dozier ◽  
J. M. Drake ◽  
J. Klafter
Keyword(s):  
Vycor Glass ◽  
Self Diffusion ◽  
Porous Vycor Glass

Non-Standard Fickian Self-Diffusion of Isotopically Pure Boron Observed by Neutron Reflectometry and Depth Profiling

1994 ◽  
Vol 376 ◽  
Author(s):  
Shenda M. Baker ◽  
K. Wu ◽  
G. S. Smith ◽  
K. M. Hubbard ◽  
M. Nastasi ◽  
...  
Keyword(s):  
Standard Form ◽  
Diffusion Constant ◽  
Depth Profiling ◽  
Step Function ◽  
Neutron Reflectometry ◽  
Fickian Diffusion ◽  
Neutron Depth Profiling ◽  
Self Diffusion ◽  
Fixed Composition ◽  
Comparison Of The Results

ABSTRACTNeutron reflectometry (NR) studies1 of thin films of amorphous 11B/l0B on silicon indicate that a non-standard form of Fickian diffusion occurs across the boron interface upon annealing. In order to verify this observation, the samples were examined by neutron depth profiling (NDP). Comparison of the results from models of a step function, standard Fickian diffusion and Fickian diffusion with a fixed composition at the interface were made and compared to the previous NR results. The diffusion constant resulting from the non-standard Fickian model for the NDP data differs slightly from that obtained from the commonly used Fickian diffusion model and is not inconsistent with the NR results. This finding suggests that more information regarding diffusion at interfaces can be gained from these higher resolution neutron scattering techniques.

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