Osmotic pressure measurement weight

Osmotic pressure is one of the colligative properties of solutions containing both low-Molecular weight compounds and high polymers. The major difficulty faced in the study of the behaviour of low Molecular weight compounds in solution by the Osmotic pressure measurement method is the selection of a suitable semi-permeable membrane. 

Equation 3.27 forms the basis for determination of Molecular weight from light scattering data. Like Osmotic pressure measurements, it is essential to consider the non-ideality of solutions and the concentration dependence. Following Debye, eq. 3.27 gets modified to... 

To get from the amino acid analysis of the protein to its structure, its molecular weight had to be estimated. As early as 1885 Zinoffsky had reported a minimum molecular weight for hemoglobin of 16.73 kDa based on its elementary composition and assuming one atom of iron/ mole, a remarkably accurate figure. For most proteins because of their large size and ease of denaturation, classical cryoscopic or ebulliscopic methods were impracticable. Osmotic pressure measurements were... 

EXAMPLE 3.1 Molecular Weights from Osmotic Pressure Measurements. To what molecular weights do the limiting reduced osmotic pressures obtained from Figure 3.5 correspond The data in Figure 3.5 are presented in such a way that unit problems do not enter the picture. We are not usually so lucky Consider some possible combinations of units for tt, V, and R that are compatible with the units of the ordinate in Figure 3.5. 

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 ... 

How does one use osmotic pressure measurements to determine the molecular weight of a solute How does polydispersity in molecular weight affect such a measurment ... 

Rayleigh X Rs, particle size Applicable for (R/X) < 1/20 extension of the Rayleigh equation to solutions allows the measurement of osmotic pressure, molecular weight, and turbidity of colloidal or polymer solutions see Section 5.3... 

Molecular weight from osmotic pressure measurements Degree of polymerization and molecular weight distribution Excluded volume from osmotic pressure measurements Theta temperature from second virial coefficient data Evaluation of charges on macroions from osmotic pressures... 

SIDEBAR 7.13 MOLECULAR WEIGHT DETERMINATION BY OSMOTIC-PRESSURE MEASUREMENTS... 

From osmotic pressure measurements, the molecular weight of amylose has been determined as approximately 10,000-50,000. This value is well in line with the value estimated from the determination of the terminal functional groups. 

The molecular weights of glycogens from different sources have recently been compared, using sedimentation and osmotic pressure measurements. 4 A significant difference was found in the size of the products from different sources (Table II), but although all samples... 

A very different structure has been found for the mannan that is present in yeast. Methylation and hydrolysis67 showed this to be a highly branched molecule. The methylated material was inhomogeneous, the intrinsic viscosity of different fractions varying between 0.062 and 0.212, with corresponding molecular weights (determined by osmotic pressure measurements) between 18,000 and 76,000 (90-830 hexose units). 

The pectins studied by Glikman and Orlov38 would appear to have been degraded, as osmotic pressure measurements indicated values for the molecular weight of 4,000-33,000. These authors also found a nonlinear relationship between the intrinsic viscosity and the molecular weight, the most satisfactory equation being [jj] = 1.1(10)-B(M)1-22. 

The molecular weight of the methylated polysaccharide used in structural determinations of a complex specific somatic polysaccharide has been determined by osmotic pressure measurements in chloroform solution as being 12,000.111... 

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