Activation enthalpy of diffusion for well fractionated dextrans in aqueous solutions

Convection-driven generation of long-range material gradients

“…The diffusion coefficients for several MWs of FITC-dextran dissolved in PBS at 25°C have been measured[17] and give similar results to one study of FITC-dextran in water. [18] Averaging interpolated results from four studies[17-20] that measured the diffusion coefficient D of 10kDa FITC-dextran in water and PBS at 25°C yields D = 1.3×10 −6 cm 2 s −1 . The particular values interpolated from each study ranged from 0.9 to 2.0×10 −6 cm 2 s −1 due to differences in the degree of branching and polydispersity of the dextrans used in the studies.…”

Model for the influence of mass transport on enzymatic hydrolysis of polysaccharides

“…These values are very high in comparison to those valid for diffusion, for example, dissolution in aqueous solutions with activation energies in the range of 10 to 20 kJ/mol [5] (Moore [6] gives a value of 18 kJ/mol at 300 K), the activation energies for the diffusion of the polyglucan dextran in aqueous solutions were reported to be in the same range [7].…”

Relationship of Stokes Radius to the Rate of Diffusion across Bruch's Membrane

“…Similar trends have been observed in diffusion of proteins through the sclera. 28,29 When studied individually, small molecules (amino acids with mass similar to that of cytosine) were found to have an almost linear trend 11 of flux relative to mass, whereas dextran macromolecules of differing size followed a power law relationship 17,25,30 of flux relative to mass. Interestingly, the P of BM/Ch for ferritin was very similar to albumin despite the difference in their R S values (3.55 nm for albumin vs. 6.15 nm for ferritin).…”

“…This difference is likely due to the structure of dextrans. 25 Dextran flux values are expected to be higher since they are randomly coiled linear polymers, whereas the tracers we used are globular proteins (except for cytosine). 17 Dextrans and proteins of comparable mass react differently with water (dextrans are more hydrophilic) and studies on dextran diffusion have shown that they are less hindered than would be predicted on the basis of R S .…”

“…17 Dextrans and proteins of comparable mass react differently with water (dextrans are more hydrophilic) and studies on dextran diffusion have shown that they are less hindered than would be predicted on the basis of R S . 25 However, diffusional flux alone may not be the best value for comparison between molecules. Flux is influenced by many factors, including the structural properties of the tissue, the tracer, the concentration gradient, and the time course of the experiment.…”