scholarly journals A sensitive and accurate gel osmometer

1973 ◽  
Vol 131 (4) ◽  
pp. 843-850 ◽  
Author(s):  
A. G. Ogston ◽  
B. N. Preston
Keyword(s):  
Human Serum Albumin ◽  
Osmotic Pressure ◽  
Polyethylene Glycols ◽  
Single Measurement ◽  
Circular Loop ◽  
Molecular Weights ◽  
Open Circular ◽  
Effective Sensitivity ◽  
Micrometer Eyepiece ◽  
Sephadex Bead

1. A bilayer strip, cut from a thin layer of cross-linked polyacrylamide gel cast on to cellulose tissue, forms an open circular loop whose ends are close together. Shrinkage of the gel, in response to the osmotic pressure of a non-penetrating solution, causes a proportional separation of the ends of the loop. This is measured with a microscope and micrometer eyepiece. 2. The resulting effective sensitivity is about 30 times that of the Sephadex-bead osmometer (Ogston & Wells, 1970), i.e. of the order of 5Pa, comparable with that of a membrane osmometer. Use of gel up to 70% (w/v) allows the measurement of molecular weights, as low as 1500 in favourable cases, with an accuracy of 1–2%. The useful range of osmotic pressure is up to 5kPa. A single measurement requires 0.5ml of solution. Equilibration is completed in 20–30min. 3. The method is illustrated by measurements on human serum albumin, ovalbumin, cytochrome c, samples of dextrans, polyvinyl alcohol, and polyethylene glycols 6000 and 1000.

scholarly journals OSMOTIC PRESSURE STUDY OF PROTEIN FRACTIONS IN NORMAL AND IN NEPHROTIC SUBJECTS

1939 ◽  
Vol 69 (6) ◽  
pp. 819-831 ◽  
Author(s):  
Jaques Bourdillon
Keyword(s):  
Osmotic Pressure ◽  
Normal Serum ◽  
The Other ◽  
Protein Fractions ◽  
Molecular Weights ◽  
Other Hand ◽  
Normal Albumin

In serum of patients with nephrosis both albumin and globulin showed by osmotic pressure nearly double the molecular weights of normal albumin and globulin. In the urines of such patients, on the other hand, both proteins showed molecular weights lower even than in normal serum. The colloidal osmotic pressures were measured by the author's method at such dilutions that the van't Hoff law relating pressures to molecular concentrations could be directly applied. For the albumin and globulin of normal serum the molecular weights found were 72,000 and 164,000 respectively, in agreement with the weights obtained by other methods.

THE INFLUENCE OF MEMBRANE PREPARATION ON THE OSMOTIC PRESSURE OF POLYVINYL ACETATE IN ACETONE

1946 ◽  
Vol 24b (4) ◽  
pp. 150-166 ◽  
Author(s):  
R. E. Robertson ◽  
R. McIntosh ◽  
W. E. Grummitt
Keyword(s):  
Sodium Hydroxide ◽  
Osmotic Pressure ◽  
Cell Volume ◽  
Polyvinyl Acetate ◽  
Membrane Surface ◽  
Membrane Preparation ◽  
Adequate Explanation ◽  
Full Account ◽  
Molecular Weights ◽  
Large Ratio

A full account of the experimental procedures used to determine the number average molecular weights of a series of polyvinyl acetates is given. Adsorption of polyvinyl acetate on a cellophane membrane is demonstrated. The importance of this phenomenon is increased when cells of large ratio of membrane surface to cell volume are used. The presence of small amounts of sodium hydroxide in the membrane eliminates detectable adsorption and alters the osmotic pressure values. This change does not appear to be due to imperfect semipermeability of the membranes, and no adequate explanation of the phenomenon has been as yet discovered.

Membranes for measuring Low Molecular Weights by Osmotic Pressure

Nature ◽  
1967 ◽  
Vol 213 (5077) ◽  
pp. 692-693 ◽  
Author(s):  
J. R. H. WAKE ◽  
A. M. POSNER
Keyword(s):  
Osmotic Pressure ◽  
Molecular Weights

Improvement of the dissolution rate of indomethacin by a cogrinding technique using polyethylene glycols of various molecular weights

2006 ◽  
Vol 16 (3) ◽  
pp. 203-209 ◽  
Author(s):  
J. Shokri ◽  
J. Hanaee ◽  
M. Barzegar-Jalali ◽  
R. Changizi ◽  
M. Rahbar ◽  
...  
Keyword(s):  
Dissolution Rate ◽  
Polyethylene Glycols ◽  
Molecular Weights

THE NUMBER OF SUBUNITS IN THE MOLECULE OF HORSE HEMOGLOBIN

1956 ◽  
Vol 34 (4) ◽  
pp. 411-425 ◽  
Author(s):  
M. E. Reichmann ◽  
J. Ross Colvin
Keyword(s):  
Light Scattering ◽  
Osmotic Pressure ◽  
Performic Acid ◽  
Approach To Equilibrium ◽  
Salt Solutions ◽  
Covalent Bonds ◽  
Molecular Weights ◽  
Equilibrium Sedimentation ◽  
Hemoglobin Molecule ◽  
Ph Range

The molecular weights of horse hemoglobin, horse globin, and performic acid oxidized horse globin were determined by osmotic pressure, by an approach to equilibrium sedimentation, and by light scattering (except hemoglobin) at pH 1.5 to 2.5 in 0.05 M NaCl. Sedimentation coefficients were determined for these materials over the same pH range and electrophoretic analyses were made from pH 1.5 to 4.0. The results show that in dilute salt solutions below pH 2.5 horse hemoglobin dissociates to four subunits all approximately equal in mass but at least two of which differ electrokinetically and therefore in composition. The subunits are probably held together in the native hemoglobin molecule only by non-covalent bonds.

Equation for osmotic pressure of serum protein (fractions)

2004 ◽  
Vol 96 (2) ◽  
pp. 762-764 ◽  
Author(s):  
Johan Ahlqvist
Keyword(s):  
Molecular Weight ◽  
Regression Analysis ◽  
Osmotic Pressure ◽  
Serum Protein ◽  
Protein Fractions ◽  
Fibrinogen Concentration ◽  
Nonlinear Regression Analysis ◽  
Molecular Weights ◽  
Wide Range ◽  
Better Than

The colloid or protein osmotic pressure (Π) is a function of protein molarity (linear) and of Donnan and other effects. Albumin is the major osmotic protein, but also globulins influence Π. Equations based on concentrations of albumin and nonalbumin (globulin concentration + fibrinogen concentration) protein approximate Π better than albumin alone. Globulins have a wide range of molecular weights, and a 1956 diagram indicated that Π of globulin fractions decreased in the order α1-, α2-, β-, and γ-globulin. The molecular weight of the serum protein fractions had been extrapolated, so van't Hoff's law and nonlinear regression analysis of the curves permitted expression of the diagram as an equation: [Formula: see text], where Πs,Ott,2°C,cmH2O is Π of serum at 2°C (in cmH2O) computed from the 1956 diagram, Ctot is the concentration (g/l) of total protein in serum, and xalb, xα1, xα2, xβ, and xγ are the fractions of albumin, α1-, α2-, β-, and γ-globulin, respectively. At one and the same concentration of fractions, Π“Ott” decreases in the order α1-globulin, albumin, α2-globulin, β-globulin, and γ-globulin.

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