SEDIMENTATION EQUILIBRIUM IN A DENSITY GRADIENT: AN EVALUATION OF THE ERRORS CAUSED BY REFRACTION OF LIGHT IN THE PHOTOMETRIC DETERMINATION OF MOLECULAR WEIGHT AND BUOYANT DENSITY

1961 ◽  
Vol 65 (6) ◽  
pp. 1069-1071 ◽  
Author(s):  
John E. Hearst ◽  
Jerome Vinograd
Keyword(s):  
Molecular Weight ◽  
Density Gradient ◽  
Buoyant Density ◽  
Photometric Determination ◽  
Sedimentation Equilibrium

scholarly journals The use of equilibrium-density-gradient methods for the preparation and characterization of blood-group-specific glycoproteins

1970 ◽  
Vol 117 (5) ◽  
pp. 879-891 ◽  
Author(s):  
J. M. Creeth ◽  
M. A. Denborough
Keyword(s):  
Molecular Weight ◽  
Density Gradient ◽  
Blood Group ◽  
Buoyant Density ◽  
Gradient Methods ◽  
Apparent Molecular Weight ◽  
Sedimentation Equilibrium ◽  
Equilibrium Density ◽  
Caesium Chloride ◽  
Selective Solvation

1. The method of sedimentation equilibrium in a gradient of caesium chloride has been applied to the preparation of blood-group-specific glycoproteins from human ovarian-cyst fluids: it is shown that virtually complete separation from contaminating protein is easily accomplished in a single step. 2. The glycoproteins isolated in this way have been characterized by analytical density-gradient experiments in both caesium chloride and caesium sulphate and values of the buoyant density, selective solvation and apparent molecular weight have been obtained. 3. In some cases, materials prepared from the same cysts by solvent extraction methods have also been characterized in these terms. 4. The selective solvation values are about 0.1 and 0.5g of water/g of glycoprotein in caesium chloride and caesium sulphate respectively. 5. The apparent molecular-weight values are much lower than the weight-average molecular weights, and it is shown that the origin of the discrepancy is heterogeneity in density of the glycoproteins. 6. Some sources of error in the interpretation of density-gradient schlieren patterns are examined.

scholarly journals The macromolecular properties of blood-group-specific glycoproteins. Characterization of a series of fractions obtained by solvent fractionation

1974 ◽  
Vol 143 (1) ◽  
pp. 159-170 ◽  
Author(s):  
J. Michael Creeth ◽  
K. Ramakrishnan Bhaskar ◽  
Alastair S. R. Donald ◽  
Walter T. J. Morgan
Keyword(s):  
Molecular Weight ◽  
Density Gradient ◽  
Blood Group ◽  
Buoyant Density ◽  
Extraction Procedure ◽  
Sedimentation Velocity ◽  
Water Soluble ◽  
Solvent Fractionation ◽  
Cross Linkage ◽  
Serological Activity

1. The glycoprotein components of a human ovarian-cyst fluid were isolated by a solvent [95% (w/w) phenol]-extraction procedure; the phenol-insoluble water-soluble glycoprotein was further fractionated by (NH4)2SO4 and by ethanol to yield eight fractions. 2. The fractions were analysed in terms of amino acids, fucose, galactose, N-acetylglucosamine, N-acetylgalactosamine and sialic acid. Variations occurred, particularly in the proportion of peptide; these were partly correlated with varying extent of serological activity. 3. The fractions were characterized physicochemically in terms of buoyant density and degree of spreading in a density gradient, sedimentation velocity and molecular weight; their partial specific volumes and specific refraction increments were also determined. 4. The fractions showed wide variations in their sedimentation-velocity and density-gradient patterns, and gave evidence of pauci-dispersity in density. The fraction regarded as the most typical blood-group-specific glycoprotein sedimented as a single rapidly spreading peak and was of high molecular weight. 5. Significant correlations were observed between the physical properties of the glycoprotein fractions and the amount of their peptide component. The buoyant densities and sedimentation coefficients varied in a manner that suggested the existence of two families of glycoproteins. 6. It is suggested that variability in the extent of glycosylation, or in the degree of cross-linking, might account for the two families of glycoproteins, and that the extent of cross-linkage might also be a factor determining the solubility of these glycoproteins in hot saturated (NH4)2SO4.

scholarly journals Some Physicochemical Properties of Erysimum Latent Virus

1982 ◽  
Vol 35 (1) ◽  
pp. 5
Author(s):  
Keith H Gough ◽  
Glenn G Lilley ◽  
Dharma D Shukla ◽  
Frank Woods
Keyword(s):  
Molecular Weight ◽  
Buoyant Density ◽  
Latent Virus ◽  
Sedimentation Equilibrium ◽  
Protein Subunit ◽  
Molecular Weights ◽  
Caesium Chloride ◽  
Rna Content ◽  
Velocity Diffusion ◽  
Phosphorus Determination

Sedimentation velocity, diffusion coefficient and sedimentation equilibrium measurements gave a molecular weight of 5 �90 x 106 for the intact Erysimum latent virus. The molecular weight of the empty shell was estimated to be 3�92 X 106 and the protein subunit to be 21 600. The RNA content calculated from the molecular weights of the full and empty particles is 33 %, in agreement with that estimated from the buoyant density in caesium chloride. However, a direct phosphorus determination gave an RNA content of only 28 %.

Determination of Copolymer Molecular Weight

1968 ◽  
Vol 41 (1) ◽  
pp. 245-253 ◽  
Author(s):  
Paul Rempp ◽  
Henri Benoit
Keyword(s):  
Molecular Weight ◽  
Light Scattering ◽  
Density Gradient ◽  
Compositional Heterogeneity ◽  
Precise Information ◽  
Molecular Weights ◽  
Molecular Weight Distributions ◽  
Weight Distributions ◽  
Binary Copolymers

Abstract From this brief review it appears that determinations of molecular weight averages, of molecular weight distributions, and of compositional inhomogeneity of binary copolymers, require care in the choice of techniques and methods. Some of the most commonly used techniques for molecular weight determinations on homopolymers of various kinds are inadequate for the same determinations on copolymers. Others are more sensitive to fluctuations in composition than in molecular weights. Osmotic methods are the only one which are really insensitive to inhomogeneity, and which yield molecular weights. Ultracentrifugation in a density gradient yields precise information only on fluctuations in composition. Viscosity determinations require calibration, but even so, they may lead to erroneous values of the molecular weight in the case of copolymers. GPC is less sensitive to compositional heterogeneity, but cannot be applied for nonlinear copolymers. Finally, light scattering is a very powerful tool for studies on copolymers, since it leads to molecular weight averages and its helps characterize polydispersity and fluctuations in composition.

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