Stokes’ radius

FIGURE 2.8 Determination of relative clearance of dextran as a function of solute size. Please note that Stokes radius (left curve) will yield too low a value for the renal clearance barrier. [Reproduced from Hagel et al. (1993), with permission.]... 

A prerequisite condition for the increase in conductivity being caused by added ligands is a high association constant of the salt in the absence of added ligand. If the association constant is low, as it is for AN-based solutions, a decrease of conductivity may occur, because the Stokes radius of the solvated Li+ ion is increased by ligands with molecular diameters larger than that of AN, entailing lower cation mobility [214],... 

Dynamic light scattering (DLS) Translational diffusion coefficient, hydrodynamic or Stokes radius branching information (when Rh used with Rg) Fixed 90° angle instruments not suitable for polysaccharides. Multi-angle instrument necessary. [3]... 

Rothe, GM, Determination of Molecular Mass, Stoke radius. Frictional Coefficient and Isomer-Type of Non-denatured Proteins by Time-Dependent Pore Gradient Gel Electrophoresis, Electrophoresis 9, 307, 1988. 

In Table 3 are also shown the hydrated radii (r ) which are evaluated with n and r by Eq. (25). A good correlation of with the Stokes radius [60] (r ) has been observed for hydrated cations (alkali and alkaline earth metal ions) [46] ... 

Table 4.1 Relationship Between Molecular Weight (M) and Stokes Radius (r)...

Organic solvents (e.g., acetonitrile, methanol, etc.) help solubilize some hydrophobic proteins, and they can affect the Stokes radius, interaction with counterions, and the ionization state of the polypeptide. For more hydrophobic samples, the use of detergents and/or other organic solvents may prove beneficial. 

According to gel-filtration experiments conducted by P. Wills and J. Dijk (personal communication), proteins L17, L25, L28, L29, and L30 are compact LI, L4, L5, L6, L13, L16, L19, and L24 are moderately elongated and L2, L3, L9, Lll, L15, L23, L27, L32, and L33 are quite extended. A discrepancy between these results and those mentioned earlier is protein L9 which appears to be globular from hydrodynamic measurements (Giri et al., 1979), but the Stokes radius calculated from gel-filtration experiments was found to be quite large, suggesting an elongated particle. 

Photon correlation spectroscopy was used to study the effects of a series of nonionic surfactants on the Stokes radius (R) of low density lipoprotein (LDL2) particles (Jl, 32). LDL2 interacted with surfactants in a manner similar to membranes. 

That is, nonionic surfactants caused an increase in the Stokes radius (R) of the particles due to penetration of the phospholipid surface layer and unfolding of apoprotein B molecules leading to particle assymetry at molar ratios of surfactant LDL2 of ca. 1000/1. At higher molar ratios, corresponding to 1-2 moles surfactant per mole of phospholipid, ionic surfactants and nonionics with HLB values < 14.6 caused rapid decreases in the Stokes radius due to breakdown of LDL2 into the lipid surfactant and protein surfactant micelles. 

Minerals were ground such that a size distribution ranging from sub-micron to millimetre particles were obtained. For the experiments described here, it is desirable to use monodisperse minerals. To this end, a sedimentation technique was used to obtain minerals in the particle size range (effective Stokes radius) (i) 10-20 jam and (ii) above 20 um. 

For imaging XPS, this process was carried out on a kaolinite and coarse quartz (above 20 nm stokes radius) 1 1 mix. 

The application of high-performance capillary zone electrophoresis (HP-CZE) in its various selectivity modes has become a very valuable adjunct to HPLC for the analysis of peptides. For synthetic peptides, in particular, both HPLC and HP-CZE now form essential components of the analytical characterization of these molecules. Increasingly, zonal, micellar, or (biospecific) affinity-based HP-CZE procedures with open tubular capillary systems are adapted to allow resolution with extremely high separation efficiencies (e.g., >105 plates per meter) of synthetic or naturally occurring peptides as part of the determination of their structural, biophysical, or functional properties. Illustrative of these capabilities are the results shown in Figure 19 for the separation of several peptides with different charge and Stokes radius characteristics by HP-CZE. 

Finally, we should mention the paper by Oyamatsu et al. [514] who have studied UPD of Tl, Pb, Ag, Cd, Cu, and Bi on an Au(l 1 l)/mica electrode coated with a SAM of alkanethiols, applying CV and STM. UPD proceeded for the alkyl chain length shorter than C8. It has also been suggested that the blocking effects of the SAM depend on the Stokes radius of metal ions. For a particular case of Ag deposition, the formation of islands of atomic monolayers on which octanethiol molecules were adsorbed hexagonally has been noticed. 

If, however, the Stokes radius of the solute bears some simple relationship to its molecular weight, the latter may be determined directly from gel chromatography by means of the Laurent-Killander equation.54 Sims and Folkes59 have pointed out that equation 4 may be more simply expressed in the form... 

Squire63 used a model of the gel phase in which the volume elements available to solvent within the gel were regarded as a combination of cones, cylinders, and crevices, and derived expressions for the volumes available to a solute of Stokes radius a in these three types of pore. Certain arbitrary assumptions regarding the distribution of solute among the different types of pore gave the following equation ... 

Ackers64 has interpreted gel chromatography in terms of steric and frictional resistance to the diffusion of the solute in the gel pores, and, on this basis, he has used an equation originally proposed by Renkin65 for deriving the following relationship between Kd and the Stokes radius, a, of the solute ... 

The Kq has been measured directly for Na+ + [222] as counterion in THF, and calculated from the interionlc distance a according to the Fuoss equation for other cryptatee, using the Stokes radius values R8+ obtained from conductimetric studies of the corresponding tetraphenylborides (24). The value of Kq for Na+ + [222] in THP was deduced from that found in THF assuming that the interionlc distance remains constant in both solvents. 

---