Friction ratio

SEDFIT tries to do this by using a dependence of D on s, and it does so by making use of a link involving the translational frictional ratio///o ... 

Combination of the Perrin function, p often referred as the frictional ratio due to shape with the frictional ratio (f/fo) enables the degree of expansion of the molecule (vh/ w ) to be estimated, where Vh, (cw / g) is the volume of the swollen molecule (Polysaccharide or protein + associated solvent) per unit mass of polysaccharide and v is the partial specific volume (essentially the anhydrous molecule) ... 

When the rolls of a mixing mill or calender are travelling at the same surface speed they are said to be running at even speed. See Friction Ratio. Exothermic... 

A two-roll machine similar to an open mill but of more robust construction, having a higher friction ratio and capable of very close nip adjustment. Refining... 

The friction ratio or speed differential between the rolls is another critical parameter, shear stresses increasing as the friction ratio is increased. Increasing the speed of both rolls also increases the shear stresses. 

Studies of the properties of the isolated fragments emphasized the question, Can F2 and F2 acquire their native conformations independently A combination of sedimentation velocity and sedimentation equilibrium studies showed frictional ratios f/f0 of 1.3 and 1.4 for F, and F2, respectively, implying compact globular structures in... 

In the case of thermal crosslinking, the corresponding curatives were added to each of the EPDM and CR rubbers on a two-roll laboratory mill at room temperature. A constant friction ratio of 1.2 was maintained between the milling rolls. Approximately 2 mm sheets were drawn out from the mill and cured in a hot press at a pressure of 10 MPa and a temperature of 170°C and 160°C for EPDM and CR, respectively, for their corresponding optimum cure time (f90). 

In setting up the three-roll calender for topping one side of the fabric even surface speeds of rolls are used for the pair of rolls forming the fabric nip and a friction ratio of 3 2 between those forming the rubber nip. 

At pH 12, the disulfide and noncovalent bonds are both broken, and the monomer with a sedimentation constant of 1.45 Svedberg units is released. From frictional ratios, the monomer appears to exist as a coil with a diameter of 16 A and a length of 150 A. Analysis of the primary structure of K-casein (Loucheux-Lefebvre et al. 1978) suggests considerable secondary structure in the monomer. 23% a-helix, 31% /3-sheets, and 24% 0-turns. In contrast, other investigators, using several different approaches, obtained a-helix contents ranging from 0 to 20.8% (Bloomfield and Mead 1975). Circular dichroism spectra on the monomer indicated 14 and 31% for a-helix and / -sheet, respectively (Loucheux-Lefebvre et al 1978). An earlier study of the optical rotatory dispersion of the K-casein monomer yielded values for the a-helix content ranging from 2 to 16% (Herskovits 1966). 

Many soluble native proteins are compact, essentially spherical structures with frictional ratios (///min) around 1.25. (The term f/fmin represents the ratio of the measured frictional coefficient to the minimal value which could be obtained for the equivalent anhydrous sphere. This... 

Three types of mixer are recognized, plus a miniature mixer which would provide just enough compound for a curemeter test and one sheet. Mixers types A] and A2 and the miniature device have non-interlocking (tangential) rotors whilst type B has interlocking rotors. Dimensions of the larger mixers are specified fairly precisely, including new and worn rotor clearances, and they are required to have temperature control, a system to record power or torque and a timer. The miniature mixer is only specified in terms of capacity, rotor speed and friction ratio but is required to control of temperature, indication of power and a timer. 

In electron micrographs, alkaline phosphatase appears as a compact sphere with a diameter of about 60 A (4, 66). This is in agreement with the value of 57 A calculated for a spherical unhydrated protein based on the frictional ratio and a molecular weight of 80,000 (4) Electron micrographs of the acid-prepared monomer show no discernible structure (66). 

Table XI (73) shows the Stokes radii and frictional ratio obtained by the study of purified acid phosphatase. The preparations show molecular homogeneity during filtration on Sephadex G-100, in the analytical ultracentrifuge, and during immunolectrophoresis. These data obtained by chromatography on Sephadex G-200 indicate that human prostatic acid phosphatase has an effective Stokes radius of 47.1 A and a frictional ratio of 1.56, suggesting considerable molecular asymmetry.

Method used Stoke s radius (A) Frictional ratio (///o)... 

To the extent that the X-ray structure can be represented by an ellipsoid of revolution, it appears to be an oblate ellipsoid with an axial ratio no greater than 1 2. The approximate dimensions are 25 X 45 X 45 A. From molecular weight and free diffusion data the frictional ratio /// is 1.26. This corresponds to an unhydrated prolate ellipsoid with an axial ratio of 5.2 or an oblate ellipsoid with a ratio 0.18. If the hydration is assumed to be 0.34 g H20/g protein, the axial ratio values would be 3.0 and 0.33, respectively. The maximum hydration for a sphere would be 0.7 or 0.55 g/g for a prolate ellipsoid of axial ratio 2. 

A particle containing a given volume of dry material will have its smallest possible frictional coefficient, /0, in a particular liquid when it is in the form of an unsolvated sphere. The frictional ratio, flfQ (i.e. the ratio of the actual frictional coefficient to the frictional coefficient of the equivalent unsolvated sphere) is, therefore, a measure of a combination of asymmetry and solvation. 

With application to dissolved proteins in mind, Oncley26 has computed frictional ratios for ellipsoids of revolution of varying degrees of asymmetry and hydration. The resulting contour diagram (Figure 2.1) shows the combinations of axial ratio and hydration which are compatible with given frictional ratios. The separate contributions of asymmetry and hydration cannot be determined unless other relevant information is available. 

Figure 2.1 Values of axial ratio and hydration compatible with various frictional ratios (contour lines denote ///, values) (By courtesy of the authors26 and Reinhold Publishing Corporation)...

Knowledge of M and v enables D0 and, hence, the ratio DJD (the frictional ratio) to be calculated. 

Figure 1.5. Relationship between the frictional ratio (/// ,m) and the molecular weight for different humic acid fractions isolated from a sapric histosol. The line is the theoretically derived relationship between frictional ratio and molecular weight for a randomly coiled polymer. After Cameron et al. (1972).

Evaluate the frictional ratio by taking the partial specific volume to be 0.735 g cm- 3. Deduce the structural features of the dehydrogenase. 

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