Sedimentation velocity of polymer solutions—II. Pressure dependence of the sedimentation coefficient

1968 ◽  
Vol 4 (6) ◽  
pp. 651-659 ◽  
Author(s):  
W.J. Closs ◽  
B.R. Jennings ◽  
H.G. Jerrard
Keyword(s):  
Pressure Dependence ◽  
Polymer Solutions ◽  
Sedimentation Coefficient ◽  
Sedimentation Velocity

scholarly journals Nitrogenase of Klebsiella pneumoniae. Interaction of the component proteins studied by ultracentrifugation

1973 ◽  
Vol 135 (3) ◽  
pp. 531-535 ◽  
Author(s):  
Robert R. Eady
Keyword(s):  
Klebsiella Pneumoniae ◽  
Sedimentation Coefficient ◽  
Sedimentation Velocity ◽  
Single Peak ◽  
Molar Ratio ◽  
Titration Curves ◽  
Additional Peak

Sedimentation-velocity analyses of mixtures of the component proteins of nitrogenase of Klebsiella pneumoniae at a 1:1 molar ratio, showed a single peak of sedimentation coefficient (12.4S) considerably greater than that obtained for the larger (Fe+Mo-containing) protein centrifuged alone (10.4S). When the ratio exceeded 1:1 (the smaller Fe-containing protein in excess) an additional peak corresponding in sedimentation coefficient (about 4.5S) to free Fe-containing protein appeared. When proteins, which had been inactivated by exposure to air were used, no interaction occurred. Na2S2O4 at 2mm both reversed and prevented interaction between the two proteins; sedimentation coefficients corresponded to those of the proteins when centrifuged alone. These results demonstrate the formation of a complex between the nitrogenase proteins, and, together with data of activity titration curves, are consistent with the formulation of the nitrogenase complex of K. pneumoniae as (Fe-containing protein)–(Fe+Mo-containing protein).

scholarly journals Effective hard-sphere model of diffusion in aqueous polymer solutions

2021 ◽  
Author(s):  
Stephen Peppin
Keyword(s):  
Polyethylene Glycol ◽  
Einstein Equation ◽  
Hard Sphere ◽  
Polymer Solutions ◽  
Polymer Concentration ◽  
Sedimentation Coefficient ◽  
Hard Sphere Model ◽  
Sphere Model ◽  
Molecular Weights ◽  
Cross Diffusion

An effective hard-sphere model of the diffusion and cross-diffusion of salt in unentangled polymer solutions is developed. Given the viscosity, sedimentation coefficient and osmotic pressure of the polymer, the model predicts the diffusion and cross-diffusion coefficients as functions of the polymer concentration and molecular weight. The results are compared with experimental data on NaCl diffusion in aqueous polyethylene glycol solutions, showing good agreement at polymer molecular weights up to 400\,g/L. At higher molecular weights the model becomes less accurate, likely because of the effects of entanglement. The tracer Fickian diffusivity can be written in the form of a Stokes-Einstein equation containing the solution viscosity. For NaCl diffusion in polyethylene glycol solutions, the Stokes-Einstein equation breaks down as the polymer size increases. Using Batchelor's viscous correction factor to determine an effective viscosity experienced by the salt ions within the polymer matrix leads to much closer agreement with experiment.

The pressure dependence of the rapid sedimentation of polymer solutions

1978 ◽  
Vol 20 (9) ◽  
pp. 2240-2246 ◽  
Author(s):  
I.K. Nekrasov ◽  
N.P. Nikitina ◽  
K.G. Khabarova ◽  
S.V. Kuz'minskaya
Keyword(s):  
Pressure Dependence ◽  
Polymer Solutions
Sign in / Sign up

Export Citation Format

Share Document