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.

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 .

On the dissociation of the sheep haemoglobin molecule at neutral pH II. Sedimentation equilibrium measurements

1971 ◽  
Vol 176 (1045) ◽  
pp. 461-480 ◽  
Keyword(s):  
Ionic Strength ◽  
Osmotic Pressure ◽  
High Speed ◽  
Dissociation Constants ◽  
Average Molecular Weight ◽  
Sedimentation Equilibrium ◽  
Neutral Ph ◽  
Haemoglobin Type ◽  
Solvent Control ◽  
Preferential Uptake

The Yphantis method of high-speed sedimentation equilibrium has been used to investigate the dissociation of sheep haemoglobin (type B) at low protein concentration (0.01 to 0.1 g/dl) in both NaCl (buffered and unbuffered) and phosphate buffer solutions at approximately neutral pH, over a range of ionic strength, temperatures of 5 and 25°C being employed. The importance of reliable ‘blank’ solvent control experiments was clearly demonstrated experimentally and weight average molecular weight data were shown to be more reliable than number averages. Apart from work at 25°C and high ionic strengths, the results are compatible with a reversible tetramer-dimer ( α 2 β 2 ⇌ 2 αβ ) dissociation. The dissociation constants obtained showed considerable agreement with those determined by osmotic pressure (reported in the previous paper) for the lower ionic strengths ( I < 1.0), but at 2 mol/l NaCl and 5°C, the sedimentation equilibrium value was 40 % higher. This probably arises through the preferential uptake of water from the high ionic strength solvent, though some dimer-monomer ( αβ ⇌ α + β ) dissociation cannot be completely excluded. On the other hand, in 2 mol/l NaCl at 25°C, the presence of monomeric units was strongly indicated, in conformity with osmotic pressure and other indications. At low NaCl concentrations, the dissociation was not significantly affected by a temperature increase from 5 to 25°C, but in phosphate solutions of comparable ionic strength, significantly less dissociation occurred and an enthalpy increase on dissociation of 55 to 63 kJ/mol was observed.

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.

Chemistry and Properties of Imide Oligomers from Phenylethynyl-Containing Diamines

2000 ◽  
Vol 12 (1) ◽  
pp. 213-223 ◽  
Author(s):  
J G Smith ◽  
J W Connell
Keyword(s):  
Thin Films ◽  
Molecular Weight ◽  
Research Effort ◽  
Average Molecular Weight ◽  
Number Average Molecular Weight ◽  
Similar Composition ◽  
Imide Oligomers ◽  
Calculated Number

As an extension of work on pendent phenylethynyl-containing imide oligomers, three new diamines containing pendent phenylethynyl groups were prepared and characterized. These diamines were used to prepare pendent and pendent and terminal phenylethynyl imide oligomers via the amide acid route in N-methyl-2-pyrrolidinone at a calculated number average molecular weight of 5000 g mol−1. The pendent phenylethynyl groups were randomly distributed along the oligomer backbone and provided a means of controlling the distance between reactive sites. The imide oligomers were characterized and thermally cured, and the cured polymers evaluated as thin films and compared with materials of similar composition prepared from 3,5-diamino-4′-phenylethynylbenzophenone. This work was performed as part of a continuing research effort to develop structural resins for potential aeronautical applications.

scholarly journals Valonea Tannin: Tyrosinase Inhibition Activity, Structural Elucidation and Insights into the Inhibition Mechanism

Molecules ◽  
2021 ◽  
Vol 26 (9) ◽  
pp. 2747
Author(s):  
Jiaman Liu ◽  
Yuqing Liu ◽  
Xiaofeng He ◽  
Bo Teng ◽  
Jacqui M. McRae
Keyword(s):  
Molecular Weight ◽  
Structure Function ◽  
Hydrophobic Interactions ◽  
Average Molecular Weight ◽  
Commercial Application ◽  
Inhibition Mechanism ◽  
Resonance Spectroscopy ◽  
Inhibition Activity ◽  
Tyrosinase Inhibition ◽  
Function Activity

Valonea tannin is a natural product readily extracted from acorn shells that has been suggested to have potential skin whitening properties. This study investigated the tyrosinase inhibition activity of extracted valonea tannin and the associated structure–function activity. Nuclear magnetic resonance spectroscopy and molecular weight analysis with gel permeation chromatography revealed that valonea tannin could be characterized as a hydrolysable tannin with galloyl, hexahydroxydiphenoyl and open formed-glucose moieties and an average molecular weight of 3042 ± 15 Da. Tyrosinase inhibition assays demonstrated that valonea tannin was 334 times more effective than gallic acid and 3.4 times more effective than tannic acid, which may relate to the larger molecular size. Kinetic studies of the inhibition reactions indicated that valonea tannin provided tyrosinase inhibition through mixed competitive–uncompetitive way. Stern–Volmer fitted fluorescence quenching analysis, isothermal titration calorimetry analysis and in silico molecule docking showed valonea tannin non-selectively bound to the surface of tyrosinase via hydrogen bonds and hydrophobic interactions. Inductively coupled plasma-optical emission spectroscopy and free radical scavenging assays indicated the valonea tannin had copper ion chelating and antioxidant ability, which may also contribute to inhibition activity. These results demonstrated the structure–function activity of valonea tannin as a highly effective natural tyrosinase inhibitor that may have commercial application in dermatological medicines or cosmetic products.

Alternating poly(ester amide)s from glutaric anhydride and α,ω-aminoalcohols: synthesis and thermal properties

e-Polymers ◽  
2003 ◽  
Vol 3 (1) ◽  
Author(s):  
Thomas Fey ◽  
Helmut Keul ◽  
Hartwig Höcker
Keyword(s):  
Molecular Weight ◽  
Thermal Properties ◽  
Homologous Series ◽  
Average Molecular Weight ◽  
Number Average Molecular Weight ◽  
Melting Points ◽  
Glutaric Anhydride ◽  
H Nmr ◽  
Activating Agent ◽  
Dimethylformamide Solution

Abstract Alternating poly(ester amide)s 6a - e were prepared by polycondensation of α-carboxyl-ω-hydroxyamides 3a - e which were obtained by aminolysis of glutaric anhydride (1) and α,ω-aminoalcohols, H2N-(CH2)x-OH (x = 2 - 6) 2a - e. The polycondensation was performed in dimethylformamide solution using a carbodiimide as activating agent, or in bulk with Bu2Sn(OMe)2, Ti(OBu)4 and Sn(octoate)2 as a catalyst. For the polycondensation in bulk, the influence of catalyst and of temperature on the number-average molecular weight was studied. 1H NMR analyses of the poly(ester amide)s clearly show the alternating microstructure. The poly(ester amide)s from glutaric anhydride and the homologous series of α,ω-aminoalcohols are semicrystalline materials; their melting points show the odd/even effect observed for other poly(ester amide)s.

Study on the Reaction of TDI and PPG with Organo-Tin Mixed Catalyst

2011 ◽  
Vol 418-420 ◽  
pp. 13-17
Author(s):  
Su Ran Liao ◽  
Yuan Wei ◽  
Yu Qi Zhang ◽  
Meng Zhang ◽  
Gao Fei Feng
Keyword(s):  
Molecular Weight ◽  
Hydrogen Bonding ◽  
Average Molecular Weight ◽  
Polypropylene Glycol ◽  
Number Average Molecular Weight ◽  
Mixed Catalyst ◽  
Back Titration ◽  
Step Growth ◽  
Step Growth Polymerization ◽  
Polymerization Conditions

The study of polyurethanes are of continuing interest due to their excellent physical properties. In this study, the reaction kinetics and polymerization conditions in two-step process of toluene diisocyante (TDI) and polypropylene glycol (PPG) with organo-tin mixed catalyst were investigated by di-n-butylamine back-titration. It was showed that the reaction obeyed the second-order equation of step-growth polymerization, the rate constants of TDI and PPG reaction at 50, 60 and 70°C were 0.0922, 0.3373 and 0.5828 kg•mol-1•min-1，respectively. The activation energy obtained from the result was 71.63 kJ•mol-1. The number average molecular weight (Mn) and molecular-weight distribution (Mw/Mn) of the polyurethane were 45175 and 1.53, respectively, and the content of hydrogen bonding in the N-H group from Fourier transform infrared spectrum (FTIR) was 80.75%, which manifested that the large amount of N-H were present in hydrogen bonding.

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