Protein specific volumes

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) ... 

The hydrodynamic properties of Ustilago cytochrome c were investigated by Thelander (86). He found the partial specific volume to be 0.721 ml/g and the molecular weight, by sedimentation equilibrium, to be 15,500. The latter value, although higher than that given by summation of the constituent amino acid residues (i.e., 11,877, see Table 3), indicates that the protein is monomeric. 

The value of the partial specific volume for proteins is approximately 0.7 while for nucleic acids the value varies around 0.5. 

What is obtained by performing such experiments across an appropriate temperature range is the precise measurement of the coefficient of thermal expansion for protein partial specific volumes that may be detected at concentrations... 

Foaming or whippability characteristics of whey protein as affected by treatment with three proteolytic enzymes were evaluated by Kuehler and Stine (43). The specific volume of foams increased initally as a result of treatment, then decreased with time at a more rapid rate compared to nontreated whey (Figure 8). 

Figure 8. Effect of enzymatic hydrolysis on specific volume of foam obtained by whipping a heated whey protein sol (4% w/w, 85°C, 6 min whipping) (43)...

EXAMPLE 3.3 Excluded Volume of Bovine Serum Albumin from Osmotic Pressure Measurements. A plot of 7r/c versus c for an aqueous solution of the bovine serum albumin molecule at 25°C and pH = 5.37 is shown in Figure 3.6. The molecule is known to be nearly spherical and uncharged at this pH. Evaluate the molecular weight and the excluded volume of this protein from the intercept and slope of this line, 0.268 torr (g kg-1)-1 and 1.37 10 3 torr kg2 g 2, respectively. From the particle mass and volume, estimate the partial specific volume of the solute in solution. The specific volume of the unsolvated protein is about 0.75 cm3 g 1 does the solute appear to be solvated ... 

Sedimentation. The sedimentation experiments are tabulated in Tables I and II. In Table I typical sedimentation coefficients determined in H20 and D20 are in close agreement here and with previously reported values determined for both protio and deuterio phycocyanin from F. calothricoides (15,16). Each of the tabulated coefficients is for a single experiment at an approximate protein concentration of 15 mg. per ml. Lyophilizing a phycocyanin preparation twice had little effect on the observed sedimentation coefficients. In calculating the S values the same partial specific volume of the protein was used for both D20 and H20. This practice is consistent with the recent results of Edelstein and Schach-man (7). Small increases in sedimentation coefficients from H20 to D20 are to be expected because of deuterium substitution on exchangeable positions. The slope of an S vs. concentration plot for phycocyanin in H20 and D20 would also probably differ. Consequently, small changes in S from H20 to D20 would be expected at a constant protein concentration. 

Here c(r) is the concentration c at the radial position r (measured from the centrifuge axis), a is the radial distance of the meniscus, M is the molecular mass in daltons, and v is the partial specific volume in ml/gram. For most proteins v varies from 0.69-0.75. It is the reciprocal of the density of the particle. Rho (p) is the density (g/ml) of the solvent. A plot of log c(r) against r2 is a straight line of slope M (1 -up) / 2RT. The computer can also accommodate mixtures of proteins of... 

Lactoglobulin A in 40% 2-Chloroethanol. Previous light scattering and differential refractometry measurements (8, 23) have shown that / -lactoglobulin exhibits strong preferential interactions with solvent components in the water-2-chloroethanol system. Since the preferential interaction between protein and 2-chloroethanol in this system was found to be maximal at 40% (v/v), the effect of this interaction on the partial specific volume of the protein was determined. 

The densities of the solvent and of / -lactoglobulin A ( -Lg) in 40% (v/v) 2-chloroethanol, in the presence of 0.01 M HC1 and 0.02M NaCl, were determined, with and without prior dialysis, in a 10-ml pycnometer at 20°C. Solutions were prepared as described previously (8, 24). The solutions were filtered through millipore filters in syringe adapters just before the density measurements. Protein concentrations were determined after filtration by ultraviolet absorption at 278 nm. The apparent partial specific volume, oapp, was calculated from the densities using the standard equation (21, 25) ... 

Knowledge of the partial specific volume of a protein in the denaturant, t>2,03, which is essential for determining its molecular weight by small-angle x-ray scattering, permits also the calculation of the volume change upon denaturation since... 

For the denaturation of / -Lg in 40% 2-chloroethanol, the presently reported partial specific volume measurements result in a AV value of —590 ml/mole. This value is very close to that previously reported for the denaturation of this protein by 6.4M urea, —610 ml/mole (27). Although this similarity of AV values is striking, it might be the result of a fortuitous compensation of various effects. The change in volume calculated from the difference in partial specific volumes is the sum of a number of contributions (28), such as differences in electrostriction in the two media, changes in the density of solvent components when they interact... 

With use of the. s 2°0w and D°o,w values cited below (Section II,D,1) an additional estimate of the molecular weight can be made by means of the Svedberg equation (18) the value obtained is 118,000. [Calculations employ as partial specific volume v = 0.745 cm3/g, obtained from the amino acid composition of the protein given in Table III (IP).]... 

With additional information, including the heat capacity of the buffer solvent, the partial specific volumes (volume per gram of the solute), and the specific volume of the solvent, one can extract the partial specific heat capacity (J K 1g I) of the solute. Privalov has summarized these calculations.8 Because the solutions are studied at very low concentrations, it is assumed that the contribution to the total heat capacity from the solvent cancels out when one calculates the excess heat capacity. With only minor exceptions, the procedures used to calculate parameters associated with the transformations in nucleic acids and in proteins are the same and yield quantities that are interpreted in similar ways, although researchers in these two fields may use a different notation for the same quantity. 

Total activity [U] Total protein [mg Volume [mL] Specific activity [U mg- ] Purification factor [fold] Yield m... 

The partial specific volume of the protein was 0.75 cm3 g 1 and the density of the solution (assumed constant) was 1.00 g cm"3. Calculate the relative molecular mass of the protein. 

A protease (i.e., a protein enzyme that degrades other proteins) specific to collagen which is the main protein matrix that holds liver cells together. Volume 1(14). 

Lovenberg, Buchanan, and Rabinowitz 65) showed that the molecular weight of C. pasteurianum ferredoxin is about 6000, based on sedimentation velocity and sedimentation equilibrium ultracentrifugation determinations and on amino acid analysis. The sedimentation coefficient, S2o,w was 1.4, and the partial specific volume, determined according to the method of Hvidt et al. 59) was 0.63, as compared to the value of 0.71 observed for most proteins. Similar investigations showed that ferredoxins from four other clostridia Lovenberg, Buchanan, and Rabinowitz 65)) and from a photosynthetic bacterium (Bachofen and Arnon 12)) also had a molecular weight of about 6000. 

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