Hydrodynamic radius/diameter

The source of this 43% difference between the dry radius and the hydrodynamic radius is unlikely to be the increase in diameter due to bound water. It is more likely that the shape asymmetry of the enzyme (i.e., the approximation that the enzyme is effectively spherical) is the source of the above difference. ... 

Ksec = 0 when the molecule hydrodynamic radius is higher than the mean pore diameter. KSEC is 1 with small molecules, which can easily penetrate into the pores. The most important parameters influencing resolution are the pore volume, pore size distribution, and particle size. The separation domain is between the exclusion volume Va and the inclusion volume ( V0 + Vp). 

To have an idea about the values of the molecular diameters, one may note that reaction of dialdehyde 50 where R = CH3 with the diamine 52 produces at 5 mM a [2 + 2] macrocycle (not shown) that has, according to DOSY [60, 61] studies (that provide the hydrodynamic radius of the species) in CDC13, a diameter of 16.4 A, while at 50 mM higher diameter species with a diameter of 80 A are observed. After several weeks even species having a diameter of 200 A have been observed [59]. 

Alternatively, the cell size may be characterized by the hydrodynamic radius which is equal to the ratio of the cross-sectional area of the cell to the perimeter of crossection or by a nominal cell diameter equal to that of the largest sphere circumscribing the cell The cell size is characterized in an indirect manner in terms of specific surface, thermal conductivity coefficients, air and moisture permeability, etc. 

Hydrodynamic radius of a colloidal particle (radius u = 7 h assumed) Colloid diameter (d = 2a = 2/ assumed throughout)... 

The retention process for this HP method is quite simple and well understood, (5(f). For proteins (or other macromolec es) as solutes, retention is a function of solute conformation. Thus denatur proteins have a larger hydrodynamic radius or Stokes diameter 4 [cf. Ref. (5(f)], and are... 

Antonietti and Nestl [88] reported a study using a new class of metallosurfactants that allowed them to reduce both particle size and surfactant concentration. Figure 11 shows the variation of the hydrodynamic radius of polystyrene particles as a function of the weight ratio of surfactant to monomer SIM) for microemulsions based on a classical surfactant, cetyltrimethylammonium chloride (CTAB) and the metallosurfactant tetradecyl-diethanolamine copper (TDEA-Cu). With this class of surfactants, the authors succeeded in getting a particle diameter as low as 14 nm (width of the distribution = 0.38), with an SIM value of 3. This results in a considerable surface area ( 500 m /g), which renders these systems of interest for subsequent functionalization. 

Fig. 1. Determination of the size of extruded liposomes by dynamic hght scattering. (A) Size distribution of Golgi-mix liposomes obtained by sequential extrusion through polycarbonate filters of 0.2, 0.05, and 0.03 (im pore size diameter. (B) Mean hydrodynamic radius and polydispersity (error bars) of extruded hposomes as a function of the pore size of the polycarbonate filters. Three experiments of sequential extrusions are shown.

Problem 3.29 Use the general formula, Eq. 3.55, to calculate the hydrodynamic radius of a rodlike molecule with length L and diameter b. The average between two beads at x and y on the rod measured from one of the ends is calculated only for jc - y > 6. 

Figure 1. 0(eq. 5) against probe diameter for various polymer concentrations. Ri, and Rg are the polymer radius of gyration and hydrodynamic radius. is the estimated correlation length at 0.5, 3, and 7 g/L. 

When particles are small enough to undergo Brownian motion, there is a continuous variation in the distance between the particles. As a consequence of this motion, constructive and destructive interference of the light scattered by neighboring particles yields intensity fluctuations. Following the intensity fluctuations as a function of time, the diffusion coefficient of the particles can be measured, and consequently, via the Stokes-Einstein equation, if the viscosity of the medium is known, the hydrodynamic radius or diameter of the particles can be calculated. Dynamic light scattering is therefore a very efficient method to determine the... 

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