scholarly journals A determination of the sub-units of arachin by osmometry. Arachins A, B and A1

1967 ◽  
Vol 105 (1) ◽  
pp. 181-187 ◽  
Author(s):  
M. P. Tombs ◽  
M. Lowe
Keyword(s):  
Molecular Weight ◽  
Osmotic Pressure ◽  
Gel Electrophoresis ◽  
Average Molecular Weight ◽  
Urea Concentration ◽  
Suitable Method ◽  
Number Average Molecular Weight ◽  
Disulphide Bonds ◽  
New Form

1. Osmotic pressure determinations of dissociated arachins are a particularly suitable method for determination of the number of sub-units in the protein, because they yield a number-average molecular weight. 2. Arachin, in 8m-urea–0·1m-sulphite, produces 12 sub-units from the form of molecular weight 345000. 3. When the urea concentration is varied the molecules became fully dissociated at 6m-urea–0·1m-sulphite. Although sulphite is necessary to break disulphide bridges, concentrations greater than 0·1m cause a re-aggregation of the sub-units. Similar results were obtained in guanidine solutions. 4. A new form of arachin has been discovered, A1, migrating more rapidly than arachin A. 5. The N-terminal residues of arachin have been re-investigated on more highly purified samples: they are glycine, valine and (iso)leucine in the proportions 4:1:1. 6. The three forms of arachin have the structure (B) β4γδ, (A) α2β2γδ and (A1) α4γδ, for the forms of molecular weight 170000. 7. Dissociation in 8m-urea produces some fragments, detected by gel electrophoresis, which appear to be dimers of the type α-S-S-β, β-S-S-β, held together by disulphide bonds.

scholarly journals Osmotic Pressure Measurements on Insulin: Anomalous Results Indicate that the Monomer is Preferentially Adsorbed

1986 ◽  
Vol 39 (4) ◽  
pp. 319 ◽  
Author(s):  
Peter D Jeffrey
Keyword(s):  
Molecular Weight ◽  
Ionic Strength ◽  
Osmotic Pressure ◽  
Hydrophobic Interactions ◽  
Average Molecular Weight ◽  
Adsorption Properties ◽  
Sedimentation Equilibrium ◽  
Pressure Measurements ◽  
Number Average Molecular Weight ◽  
Adsorption Analysis

The concentration dependence of the number average molecular weight of insulin at pH 2, ionic strength 0'05, and 20�C as determined by osmotic pressure measurements indicates that the .hormone is a homogeneous protein of molecular weight close to that of the dimer. Since sedimentation equilibrium experiments confirm what is well known, namely that insulin is a self-associating protein dissociating to monomer under these conditions, an explanation for the anomaly was sought in the possible loss of protein from solution by adsorption. Analysis of the results strongly supports this conclusion and consideration of the adsorption properties of insulin in terms of hydrophobic interactions shows them to be consistent with the behaviour of insulin as a self-associating protein. The monomer appears to be the primary molecular species responsible for insulin adsorption.

EBULLIOMETRY AND THE DETERMINATION OF THE MOLECULAR WEIGHTS OF POLYMERS: PART I. THE SMALL EBULLIOMETER

1959 ◽  
Vol 37 (9) ◽  
pp. 1508-1516 ◽  
Author(s):  
W. R. Blackmore
Keyword(s):  
Molecular Weight ◽  
Average Molecular Weight ◽  
Number Average Molecular Weight ◽  
Molecular Weights

An ebulliometer that has been in routine use for the determination of the number average molecular weight of polymers is described. The results obtained with two different series of polythenes (which were also measured elsewhere) are given. These results show this ebulliometer to be subject to experimental difficulties which limit it to number average molecular weights of perhaps 20,000 depending on the precision required.

Molecular weight of an extremely hydrophobic protein, zein, in dimethylformamide and in formamide

1976 ◽  
Vol 54 (2) ◽  
pp. 196-199 ◽  
Author(s):  
Laurence A. Danzer ◽  
E. Douglas Rees
Keyword(s):  
Molecular Weight ◽  
Osmotic Pressure ◽  
Protein Concentration ◽  
Average Molecular Weight ◽  
Water Soluble ◽  
Nonaqueous Solvents ◽  
Pressure Measurements ◽  
Number Average Molecular Weight ◽  
Commercial Preparation ◽  
Made In

Both alpha zein purified from a commercial preparation and beta zein prepared fresh from corn are soluble in the nonaqueous solvents formamide and dimethylformamide; in this regard zein resembles water soluble proteins such as insulin, ribonuclease, and lysozyme. On the basis of osmotic pressure measurements made in both formamide and dimethylformamide, alpha zein has a number average molecular weight of 21 000 – 24 000 daltons and shows no tendency to aggregate or dissociate. Beta zein exists in an aggregated state (dimer and higher forms) in dimethylformamide. Formamide dissociates the beta zein dimer into monomer units but aggregation to higher species occurs with increasing protein concentration.

scholarly journals Osmotic Pressure and Diffusion Constant of Protein Extracted From Wool With Urea-Bisulphite Solutions

1953 ◽  
Vol 6 (4) ◽  
pp. 630 ◽  
Author(s):  
JA Friend ◽  
IJ O'donnell
Keyword(s):  
Molecular Weight ◽  
Osmotic Pressure ◽  
Soluble Protein ◽  
Average Molecular Weight ◽  
Diffusion Constant ◽  
Pressure Measurements ◽  
Number Average Molecular Weight ◽  
And Diffusion

Wool treated with 8M urea, OAM NaHS03 at 60�C forms a polydisperse soluble protein of number-average molecular weight 12,000-16,000 as deduced from osmotic pressure measurements. The values lie within this range whether 20 or 70 per cent. of the wool is dissolved. The pH of measurement or of extraction has no effect on the molecular weight of the solute over the range 5.6-8.0. 'The diffusion constant, Dzo, W' of the soluble protein is 4.5 X 10-7 cm2sec-1 .

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