scholarly journals THE REVERSIBLE HEAT DENATURATION OF CHYMOTRYPSINOGEN

1951 ◽  
Vol 34 (5) ◽  
pp. 583-606 ◽  
Author(s):  
Max A. Eisenberg ◽  
George W. Schwert
Keyword(s):  
Protein Concentration ◽  
Protein A ◽  
Heat Denaturation ◽  
Denatured Protein ◽  
Thermodynamic Constants ◽  
Irreversible Denaturation ◽  
Ion Activity ◽  
Ph Range ◽  
And Behavior ◽  
Reversal Reaction

Within a restricted range of pH and protein concentration crystalline chymotrypsinogen undergoes thermal denaturation which is wholly reversed upon cooling. At a given temperature an equilibrium exists between native and reversibly denatured protein. Within the pH range 2 to 3 the amount of denatured protein is a function of the third power of the hydrogen ion activity. The presence of small amounts of electrolyte causes aggregation of the reversibly denatured protein. A specific anion effect has been observed at pH 2 but not at pH 3. Both the reversible denaturation reaction and the reversal reaction have been found to be first order reactions with respect to protein and the kinetic and thermodynamic constants for both reactions have been approximated at pH 2 and at pH 3. Renatured chymotrypsinogen has been found to be identical with native chymotrypsinogen with respect to crystallizability, solubility, activation to δ-chymotrypsin, sedimentation rate, and behavior upon being heated. Irreversible denaturation of chymotrypsinogen has been found to depend on pH, temperature, protein concentration, and time of heating. Irreversible denaturation results in an aggregation of the denatured protein.

scholarly journals Pb Mineral Precipitation in Solutions of Sulfate, Carbonate and Phosphate: Measured and Modeled Pb Solubility and Pb2+ Activity

Minerals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 620
Author(s):  
Xinxin Li ◽  
Behrooz Azimzadeh ◽  
Carmen Enid Martinez ◽  
Murray B. McBride
Keyword(s):  
Contaminated Soils ◽  
Formation Constants ◽  
Ion Pair ◽  
Pair Formation ◽  
X Ray Diffraction ◽  
Ion Pair Formation ◽  
Thermodynamic Constants ◽  
Ion Activity ◽  
Ion Activities ◽  
Ph Range

Lead (Pb) solubility is commonly limited by dissolution–precipitation reactions of secondary mineral phases in contaminated soils and water. In the research described here, Pb solubility and free Pb2+ ion activities were measured following the precipitation of Pb minerals from aqueous solutions containing sulfate or carbonate in a 1:5 mole ratio in the absence and presence of phosphate over the pH range 4.0–9.0. Using X-ray diffraction and Fourier-transform infrared spectroscopic analysis, we identified anglesite formed in sulfate-containing solutions at low pH. At higher pH, Pb carbonate and carbonate-sulfate minerals, hydrocerussite and leadhillite, were formed in preference to anglesite. Precipitates formed in the Pb-carbonate systems over the pH range of 6 to 9 were composed of cerussite and hydrocerussite, with the latter favored only at the highest pH investigated. The addition of phosphate into the Pb-sulfate and Pb-carbonate systems resulted in the precipitation of Pb3(PO4)2 and structurally related pyromorphite minerals and prevented Pb sulfate and carbonate mineral formation. Phosphate increased the efficiency of Pb removal from solution and decreased free Pb2+ ion activity, causing over 99.9% of Pb to be precipitated. Free Pb2+ ion activities measured using the ion-selective electrode revealed lower values than predicted from thermodynamic constants, indicating that the precipitated minerals may have lower KSP values than generally reported in thermodynamic databases. Conversely, dissolved Pb was frequently greater than predicted based on a speciation model using accepted thermodynamic constants for Pb ion-pair formation in solution. The tendency of the thermodynamic models to underestimate Pb solubility while overestimating free Pb2+ activity in these systems, at least in the higher pH range, indicates that soluble Pb ion-pair formation constants and KSP values need correction in the models.

scholarly journals DENATURATION CHANGES IN EGG ALBUMIN WITH UREA, RADIATION, AND HEAT

1943 ◽  
Vol 27 (2) ◽  
pp. 101-111 ◽  
Author(s):  
Janet H. Clark
Keyword(s):  
Protein Complex ◽  
Structural Changes ◽  
Optical Rotation ◽  
Heat Denaturation ◽  
Urea Denaturation ◽  
Egg Albumin ◽  
Denatured Protein ◽  
Higher Temperature ◽  
Ph Range ◽  
Albumin Molecule

The extent of urea denaturation depends on the concentration of protein and urea and also on the temperature of the solution. Egg albumin solutions (0.9 per cent) are not denatured by 20 per cent urea, denature slowly with 25 per cent urea, and denature rapidly with 35 per cent urea at room temperature. At a higher temperature 30 per cent urea is rapidly effective. Denaturation of the egg albumin molecule by radiation or by heat is accompanied by structural changes as evidenced by optical rotation values, but is not accompanied by association or dissociation of the molecule in the pH range outside the zone in which aggregation follows denaturation. Denaturation of the egg albumin molecule by urea produces no change in optical rotation until the concentration of urea is high enough to dissociate the molecule. In the presence of urea a urea-protein complex is formed in which the protein is denatured but cannot flocculate because of the dispersive action of the urea. This prevents flocculation of proteins exposed to radiation and subsequent heating to 40° C. as the urea-protein complex is not broken down at a temperature of 40° C. The presence of urea therefore prevents the flocculation of proteins denatured by radiation. The urea-protein complex is broken down by heating to 55–58° C. so that the molecules aggregate at a temperature below the temperature of rapid heat denaturation. This appears to be an acceleration of heat denaturation or a lowering of the heat denaturation temperature, but in reality is an effect of heat on the urea-protein complex which frees the urea-denatured protein and permits its aggregation.

Buffers for the physiological pH range: Thermodynamic constants of substituted aminopropanesulfonic acids from 5 to 55°C

1997 ◽  
Vol 26 (3) ◽  
pp. 309-317 ◽  
Author(s):  
Rabindra N. Roy ◽  
Julie A. Carlsten ◽  
Jodi Niederschmidt ◽  
William S. Good ◽  
J. Michelle Rook ◽  
...  
Keyword(s):  
Thermodynamic Constants ◽  
Ph Range

A novel EP-involved pathway for iron release from soya bean seed ferritin

2010 ◽  
Vol 427 (2) ◽  
pp. 313-321 ◽  
Author(s):  
Xiaoping Fu ◽  
Jianjun Deng ◽  
Haixia Yang ◽  
Taro Masuda ◽  
Fumiyuki Goto ◽  
...  
Keyword(s):  
Serine Protease ◽  
Protein A ◽  
Soya Bean ◽  
Iron Release ◽  
Bean Seed ◽  
Specific Domain ◽  
Exterior Surface ◽  
Legume Seeds ◽  
Seedling Germination ◽  
Ph Range

Iron in phytoferritin from legume seeds is required for seedling germination and early growth. However, the mechanism by which phytoferritin regulates its iron complement to these physiological processes remains unknown. In the present study, protein degradation is found to occur in purified SSF (soya bean seed ferritin) (consisting of H-1 and H-2 subunits) during storage, consistent with previous results that such degradation also occurs during seedling germination. In contrast, no degradation is observed with animal ferritin under identical conditions, suggesting that SSF autodegradation might be due to the EP (extension peptide) on the exterior surface of the protein, a specific domain found only in phytoferritin. Indeed, EP-deleted SSF becomes stable, confirming the above hypothesis. Further support comes from a protease activity assay showing that EP-1 (corresponding to the EP of the H-1 subunit) exhibits significant serine protease-like activity, whereas the activity of EP-2 (corresponding to the EP of the H-2 subunit) is much weaker. Consistent with the observation above, rH-1 (recombinant H-1 ferritin) is prone to degradation, whereas its analogue, rH-2, becomes very stable under identical conditions. This demonstrates that SSF degradation mainly originates from the serine protease-like activity of EP-1. Associated with EP degradation is a considerable increase in the rate of iron release from SSF induced by ascorbate in the amyloplast (pH range, 5.8–6.1). Thus phytoferritin may have facilitated the evolution of the specific domain to control its iron complement in response to cell iron need in the seedling stage.

Assay of cerebrospinal fluid protein: a rate biuret method evaluated.

1983 ◽  
Vol 29 (1) ◽  
pp. 126-129 ◽  
Author(s):  
P R Finley ◽  
R J Williams
Keyword(s):  
Cerebrospinal Fluid ◽  
Total Protein ◽  
Protein Concentration ◽  
Protein A ◽  
Colorimetric Method ◽  
Total Protein Concentration ◽  
Reaction Cell ◽  
Biuret Method ◽  
Automated Instrument ◽  
Cerebrospinal Fluid Protein

Abstract We evaluated a rate colorimetric method (Beckman) for measuring total protein in cerebrospinal fluid. The automated instrument we used was Beckman's ASTRA TM. A 100-microL sample of spinal fluid is introduced into the biuret reagent in the reaction cell and the increase in absorbance at 545 nm is monitored for 20.5 s. Solid-state circuits determine the rate of alkaline biuret-protein chelate formation, which is directly proportional to the total protein concentration in the sample. The linear range of measurement is 120 to 7500 mg/L. Day-to-day precision (CV) over the range of 150 to 1200 mg/L ranged from 15.2 to 2.3%. The method was unaffected by radical alteration of the albumin/globulin ratio, but there is a positive interference in the presence of hemoglobin, a suppression in the presence of bilirubin, and no effect by xanthochromia. The method is precise, accurate, rapid, and convenient. The method was compared with the trichloroacetic acid method as performed on the Du Pont aca III, giving a correlation coefficient (r2) of 0.9693. The method is precise, accurate, rapid, and convenient.

Complexation, Stability and Behavior of L-Cysteine and L-Lysine with Different Iron Sources

1984 ◽  
Vol 47 (1) ◽  
pp. 36-40 ◽  
Author(s):  
S. M. FLYNN ◽  
F. M. CLYDESDALE ◽  
O. T. ZAJICEK
Keyword(s):  
Ferric Chloride ◽  
Ferrous Sulfate ◽  
Mixed Valence ◽  
Qualitative Evaluation ◽  
Low Ph ◽  
Iron Hydroxides ◽  
The Stability ◽  
Ph Range ◽  
Effective Stability ◽  
And Behavior

Effective stability constants for cysteine and lysine with five different iron sources were evaluated along with their behavior in solution. The values obtained for ferric chloride-cysteine, ferrous sulfate-cysteine, ferric chloride-lysine, ferrous sulfate-lysine, hydrogen-reduced lysine, and electrolytic-reduced lysine were 6.81 × 102 to 2.78 × 103, 1.33 × 105 to 1.36 × 105, 6.00 × 10−4 to 7.64 × 10−3, 6.37 ×10−4 to 4.82× 10−3, 9.34 × 10−2 to 1.38 × 10−1, and 4.18 × 10−4 to 7.27 × 10−4, respectively. No measurable complexation occurred with hydrogen- and electrolytic-reduced iron with cysteine nor with ferric orthophosphate and cysteine or lysine. The stability of soluble ferric cysteine over the pH range 2.0 to 7.4 indicates that this complex has the potential to be used as an iron additive in food. Approximately half of the hydrogen and electrolytic reduced iron and only 0.11% of ferric orthophosphate were soluble in acid, whereas ferric chloride and ferrous sulfate were completely soluble. Qualitative evaluation of the iron-amino acid systems over a range of pH from 2.0 to 12.0 indicated that there was a mixed valence state of free iron in most cases with low pH favoring reduction and high pH oxidation, until precipitation of iron hydroxides occurred.

scholarly journals Deoxyribonuclease from Salmon Testes

1962 ◽  
Vol 45 (4) ◽  
pp. 77-92 ◽  
Author(s):  
Margaret R. McDonald
Keyword(s):  
Ionic Strength ◽  
Maximal Activity ◽  
Optimum Concentration ◽  
Heat Denaturation ◽  
Acid Extraction ◽  
Fractional Precipitation ◽  
Temperature Optimum ◽  
Monovalent Ions ◽  
Ph Range ◽  
Deoxyribonuclease Activity

A procedure is described for the purification of salmon testis deoxyribonuclease II by means of acid extraction, fractional precipitation with ammonium sulfate, heat denaturation of extraneous proteins, and ethanol fractionation. This process separates the deoxyribonuclease activity from that of ribonuclease, phosphatase, phosphodiesterase, and protease. Over 50 per cent of the activity is retained with an over-all enrichment of 20,000-fold. The enzyme degrades both native and heat-denatured DNA, but the rate of degradation of the latter is only one-tenth that of the former. It does not hydrolyze apurinic acid. The enzyme is most stable in the pH range 4 to 5. Electrolytes are essential for the expression of its activity: monovalent ions satisfy the requirement, but divalent ones are much more effective. Above a certain optimum concentration, each electrolyte is inhibitory. The pH of maximal activity, under conditions of optimal ionic strength, is 4.8; the temperature optimum is near to 55°C.

Interaction of lipids with intestinal brush border membrane preparations

1982 ◽  
Vol 60 (9) ◽  
pp. 904-909 ◽  
Author(s):  
P. Proulx ◽  
J. McNeil ◽  
I. Brglez ◽  
D. G. Williamson
Keyword(s):  
Brush Border ◽  
Protein Concentration ◽  
Brush Border Membrane ◽  
Divalent Cations ◽  
Monovalent Cations ◽  
Intestinal Brush Border Membrane ◽  
Intestinal Brush Border ◽  
Ph Range ◽  
Assay Conditions ◽  
Lipid Structures

Conditions for uptake of lipids by rabbit intestinal brush border membrane preparations were investigated. A variety of lipids were found to be incorporated, including choline and ethanolamine phosphatides as well as cholesterol, diglyceride, and fatty acid. The incorporation of those lipids tested was enhanced by Ca2+ and other divalent cations but not by monovalent cations. The optimal Ca2+ concentration was approximately 10 mM. The uptake varied with lipid and membrane protein concentration and proceeded at rates which were too rapid to measure under several assay conditions tried. Incorporations were decreased substantially outside the pH range of 6.5–8.0. The effect of one lipid, phosphatidylcholine, on the structural appearance of the membrane fraction was examined by electron microscopy. No free or surface-bound lipid structures could be detected and the membrane fractions appeared to be unchanged after uptake.

THE SULPHYDRYL CONTENT OF β-LACTOGLOBULIN

1960 ◽  
Vol 38 (3) ◽  
pp. 269-274 ◽  
Author(s):  
A. F. S. A. Habeeb
Keyword(s):  
Sodium Dodecyl Sulphate ◽  
Protein A ◽  
Sodium Dodecyl ◽  
Iodoacetic Acid ◽  
Urea Denaturation ◽  
Denatured Protein ◽  
A Value ◽  
Sulphydryl Groups ◽  
Β Lactoglobulin

The reaction of sulphydryl groups of β-lactoglobulin with N-ethylmaleimide, p-chloromercuribenzoate, and iodoacetic acid has been studied. Using N-ethylmaleimide with native and sodium dodecyl sulphate denatured protein, a value of 2.3 groups of sulphydryl per mole of protein was obtained. A value of 2.15 moles of sulphydryl per mole of protein was obtained from reaction with p-chloromercuribenzoate but lower values were obtained after urea denaturation. The reaction of iodoacetic acid was followed by the determination of residual sulphydryl by the p-chloromercuribenzoate method.

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