Dependence of the rotational viscosity of nematic mixtures on the rotational diffusion constants of their components

1993 ◽  
Vol 99 (4) ◽  
pp. 3075-3081 ◽  
Author(s):  
G. Christoph ◽  
W. Stille ◽  
G. Strobl
Keyword(s):  
Rotational Diffusion ◽  
Diffusion Constants ◽  
Rotational Viscosity

scholarly journals Interactions of Human Fibrinogen in Solution

1977 ◽  
Author(s):  
E. Serrallach ◽  
W. Känzig ◽  
V. Hofmann ◽  
P.W. Straub ◽  
M. Zulauf
Keyword(s):  
Diffusion Coefficient ◽  
Brownian Motion ◽  
Rotational Diffusion ◽  
Sedimentation Coefficient ◽  
Translational Diffusion ◽  
Initial Slope ◽  
Single Pair ◽  
Human Fibrinogen ◽  
Diffusion Constants ◽  
End To End

The intriguing diversity of published translational diffusion constants for the fibrinogen molecule can hardly be explained, unless interactions between the molecules are postulated. In the present study we have investigated the possible effect of molecular association and electrostatic intermolecular interactions on the Brownian motion. The translational diffusion coefficient DT, the rotational diffusion coefficient around the minor axis DR and the sedimentation coefficient have been measured. The methods used were dynamic light scattering and analytical ultracentrifugation. The samples were solutions of purified human fibrinogen. The correlation-function corresponding to DT deviates from a single exponential. The initial slope is found to depend on concentration, being DT = (1.7 ± 0.3) 10-7 cm2/s at 10mg/ml, pH 7.4 and 0.15 molar Tris-NaCl, and increases at fibrinogen concentrations below 2mg/ml. These results are compatible with a polydispers solution, in which single molecules are in equilibrium with pair and higher aggregates. The nature of the aggregates is end-to-end as indicated from the difference between the two rotational diffusion constants DR = 40000 ± 20% and DR = 10000 ±30% s-1. On the basis of the Hall-Slayter model and assumption of end-to-end association we calculated the ratio of the sedimentation coefficient of single, pair and triplet associates, being 1:1.14:1.20. Therefore, it is difficult to separate them in a sedimentation run. For ionic strength below 0.05 molar and low fibrinogen concentration (0.lmg/ml) a fast decay appears in the correlation, indicating that the Brownian motion is strongly influenced by electrostatic interactions.

Approximate methods for calculating rotational diffusion constants of rigid macromolecules

1987 ◽  
Vol 20 (3) ◽  
pp. 661-666 ◽  
Author(s):  
Jose Garcia de la Torre ◽  
M. Carmen Lopez Martinez ◽  
Jesus J. Garcia Molina
Keyword(s):  
Rotational Diffusion ◽  
Approximate Methods ◽  
Diffusion Constants

Untersuchungen über die Größe, Struktur und Dynamik von Gallensäure/Lecithin-Mischmicellen / Size, Structure, and Dynamics of Bile Salt/Lecithin Mixed Micelles

1977 ◽  
Vol 32 (9-10) ◽  
pp. 748-755 ◽  
Author(s):  
Ch. Gähwiller ◽  
C. von Planta ◽  
D. Schmidt ◽  
H. Steffen
Keyword(s):  
Order Parameter ◽  
Mixed Micelles ◽  
Laser Light ◽  
Size Structure ◽  
Rotational Diffusion ◽  
Laser Light Scattering ◽  
Sodium Glycocholate ◽  
Structure And Dynamics ◽  
Diffusion Constants ◽  
Transition Enthalpy

Abstract The structure and size of lecithin/sodium glycocholate mixed micelles was investigated by quasi­ elastic laser light scattering and spin label techniques.The investigations are in accordance with a bilayer model for these micelles. The order parameter and the phase transition enthalpy of the micellar bilayer were determined.The lateral and rotational diffusion constants of label molecules are compared with the cor­ responding diffusion constants in liposomes.

Notizen: Comment on the Osipov-Terentjev Calculation of the Viscosity of Liquid Crystals

1992 ◽  
Vol 47 (4) ◽  
pp. 625-626 ◽  
Author(s):  
V. I. Stepanov
Keyword(s):  
Distribution Function ◽  
Liquid Crystals ◽  
Asymptotic Formula ◽  
Diffusion Approximation ◽  
Rotational Diffusion ◽  
Azimuthal Angle ◽  
Planck Equation ◽  
Viscosity Coefficient ◽  
Second Derivative ◽  
Rotational Viscosity

AbstractThe calculation of the viscosity of liquid crystals based on the rotational diffusion approximation recently reported by Osipov and Terentjev [1 a] is critically examined. It is shown that the main result of their treatment - the evaluation of the activational exponent - arises from the neglect of the second derivative of the distribution function with respect to the azimuthal angle in the Fokker-Planck equation. The correct asymptotic formula for the rotational viscosity coefficient is derived.

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