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.

scholarly journals THE DENATURATION OF EGG ALBUMIN BY ULTRA-VIOLET RADIATION

1935 ◽  
Vol 19 (2) ◽  
pp. 199-210 ◽  
Author(s):  
Janet Howell Clark
Keyword(s):  
Ultraviolet Radiation ◽  
Ultra Violet ◽  
Heat Denaturation ◽  
Egg Albumin ◽  
Ultra Violet Radiation ◽  
Wide Ph Range ◽  
Lower Temperature ◽  
Ph Range ◽  
Albumin Molecule ◽  
Violet Radiation

The coagulation of isoelectric egg albumin solutions, on exposure to ultraviolet radiation, involves three distinct processes, (1) the light denaturation of the albumin molecule, (2) a reaction between the light denatured molecule and water which may be similar to heat denaturation but occurs at a lower temperature, and (3), the flocculation of the denatured molecules to form a coagulum. The light denaturation is unimolecular, independent of temperature, and occurs over a wide pH range. The reaction between the light denatured molecule and water has a temperature coefficient of 10+ and occurs rapidly at 40°C., a temperature at which heat denaturation is inappreciable.

SOME FACTORS INFLUENCING THE BINDING OF L-THYROXINE BY PROTEINS

1961 ◽  
Vol 36 (2) ◽  
pp. 230-236 ◽  
Author(s):  
L. Korsgaard Christensen
Keyword(s):  
Structural Changes ◽  
Considerable Increase ◽  
Serum Proteins ◽  
Binding Capacity ◽  
Protein Molecule ◽  
Binding Property ◽  
Moderate Increase ◽  
Urea Denaturation ◽  
Egg Albumin ◽  
Releasing Effect

ABSTRACT The pH-dependence of the binding of L-thyroxine to the serum proteins has been investigated by means of a dialysis procedure. A moderate increase in the binding of T4 was found when the pH varied from about 7 to 8.5. At more alkaline and more acid values a pronounced decrease in the ability to bind thyroxine was observed. The use of barbiturate buffer resulted in a very considerable increase in free non-protein-bound T4, whereas phosphate buffer did not interfere with the binding of the hormone. Tris buffer has also a thyroxine-releasing effect but this is far less pronounced than for barbiturate. Structural changes in the protein molecule were found to change its ability to bind T4. Urea denaturation of bovine serum albumin resulted in a decreased binding capacity, whereas denatured egg albumin and lactoglobulin exhibited an increase in binding property.

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 THE TEMPERATURE COEFFICIENT OF THE UREA DENATURATION OF EGG ALBUMIN

1945 ◽  
Vol 28 (6) ◽  
pp. 539-545 ◽  
Author(s):  
Janet Howell Clark
Keyword(s):  
Negative Temperature ◽  
The Other ◽  
Positive Temperature ◽  
Dilute Solution ◽  
Insoluble Protein ◽  
Urea Denaturation ◽  
Egg Albumin ◽  
Temperature Coefficients ◽  
Insoluble Material ◽  
Albumin Molecule

Evidence is brought forward to show that at concentrations of urea high enough to split the egg albumin molecule the solubility changes produced by urea are profoundly modified. The degree of precipitation after dialysis is the net result of two changes produced by the urea: the first, normally spoken of as denaturation, which makes the protein insoluble in dilute solution and the second, a splitting of the molecule which makes it soluble. These two reactions may proceed independently and simultaneously or the second reaction may follow the first, taking place in the denatured molecule only. In view of the decrease in the opalescence with time, the latter process is more probable. Both of these reactions have positive temperature coefficients, but as the concentration of urea increases the second reaction is more affected by increase in temperature than the first, and consequently the resulting opalescence decreases rather than increases with temperature. This accounts for and explains reports of negative temperature coefficients of denaturation, when denaturation is measured by the amount of insoluble material found on dilution. The occurrence of these two reactions, one leading to an increase and the other to a decrease in the amount of insoluble protein, should be taken into account when denaturation changes in egg albumin with urea are studied.

Structural changes from polyimide films to graphite: Part IV. Novax and PPT

1995 ◽  
Vol 10 (4) ◽  
pp. 1024-1027 ◽  
Author(s):  
C. Bourgerette ◽  
A. Oberlin ◽  
M. Inagaki
Keyword(s):  
Long Range ◽  
Structural Changes ◽  
Film Plane ◽  
High Rank ◽  
Polyimide Films ◽  
Electron Microscopies ◽  
Higher Temperature ◽  
Cross Linker ◽  
Graphite Part

Various polyimide films (Kapton, Upilex, Novax, and PPT) were carbonized and graphitized up to 3000 °C. They were studied by optical and electron microscopies. All films retaining oxygen as a cross linker over 1000 °C, i.e., Kapton, Upilex, and Novax, graphitize as anthracites (high rank coals) do. They get a long range statistical orientation parallel to the film plane with a nanotexture of flattened pores. Graphitization is both sudden and perfect above 2100 °C when the pore walls break. Since oxygen is released at 1000 °C, the film PPT behaves as a compact nonporous graphitizing carbon (orientation parallel to the film plane). Thermal graphitization is progressive and begins at a higher temperature.

scholarly journals Color Alteration of Encapsulated Beetroot (Beta vulgaris L.) Extract Upon Dissolving in Various pH Treatment

2020 ◽  
Vol 2 (02) ◽  
pp. 48
Author(s):  
Diah Mustika Lukitasari ◽  
Renny Indrawati ◽  
Rosita Dwi Chandra ◽  
Heriyanto Heriyanto ◽  
Leenawaty Limantara
Keyword(s):  
Beta Vulgaris ◽  
Structural Changes ◽  
Color Difference ◽  
Prolonged Storage ◽  
B Values ◽  
Ph Adjustment ◽  
Natural Pigments ◽  
Hue Angle ◽  
Color Alteration ◽  
Ph Range

It has been known that most natural pigments are unstable upon exposure against several environmental factors, such as thermal treatment, light, oxidizing or reducing agents, as well as acid or alkaline compounds. Encapsulation procedures is often adopted to adjust the solubility and provide protection to the natural pigments. Here, we prepared an encapsulated beetroot extract as the candidate of red bio-colorant. The primary aim of the present study is to investigate color alteration of encapsulated beetroot (Beta vulgaris L.) extract upon dissolving in various pH adjustment and prolonged storage. The McIllvainne buffer was prepared in various pH range, i.e. from 2 to 11. The encapsulated extract (0.1% w/v) was dissolved and the color of the solutions were measured regularly until 3 days storage under darkness at 200C. Any degradation or structural changes will cause color alteration, which were monitored through L*, a*, b* values, the hue angle (H°), chroma values (C), as well as color difference (DE). The results showed that pH 4 was the most favorable condition that brings least impact to the color alteration, even when the colored solution was kept in prolonged storage until 9 days.

Structural changes of flavylium salts. IV. Polarographic and spectrometric examination of pelargonidin chloride

1968 ◽  
Vol 21 (1) ◽  
pp. 221 ◽  
Author(s):  
KA Harper
Keyword(s):  
Ring Opening ◽  
Structural Changes ◽  
Equilibrium Mixture ◽  
Ring Cleavage ◽  
Alkaline Solutions ◽  
Similar Reaction ◽  
Anodic Wave ◽  
Wide Ph Range ◽  
Phenolic Group ◽  
Ph Range

Pelargonidin chloride has been examined polarographically and spectrometrically in aqueous methanol over a wide pH range and the molecular changes determined. In strongly acid solutions the flavylium ion is stable, but between pH3 and pH8 ring opening to the α-diketone occurs, the process involving the pseudo-base and its 3-keto tautomer. The pseudo-base is present in the equilibrium mixture from pH3 to pH12 in amount varying with the pH. The anhydrobase, detected in the equilibrium mixture at pH6, is stable above pH7, becoming ionized as the pH is raised. Unlike the anhydrobase of the simpler flavylium salts, the anhydrobase of pelargonidin chloride does not undergo ring cleavage in strong alkali under the conditions of these experiments. Ionization of the phenolic group at C5 was indicated by a, small anodic wave in the polarograms above pH9.5, due to mercuration at C6. A similar reaction, analogous to the known catalytic mercuration of ketones, was observed for phloroglucinol and resorcinol in alkaline solutions.

scholarly journals Effect of pH on the interaction of botulinum neurotoxins A, B and E with liposomes

1989 ◽  
Vol 259 (1) ◽  
pp. 47-53 ◽  
Author(s):  
C Montecucco ◽  
G Schiavo ◽  
B R Dasgupta
Keyword(s):  
Fatty Acid ◽  
Botulinum Neurotoxin ◽  
Structural Changes ◽  
Polar Region ◽  
Low Ph ◽  
Hydrophobic Core ◽  
Head Groups ◽  
Botulinum Neurotoxins ◽  
Ph Range ◽  
Lipid Interaction

The interaction of botulinum neurotoxin serotypes A, B and E with membranes of different lipid compositions was examined by photolabelling with two photoreactive phosphatidylcholine analogues that monitor the polar region and the hydrophobic core of the lipid bilayer. At neutral pH the neurotoxins interacted both with the polar head groups and with fatty acid chains of phospholipids. At acidic pHs the neurotoxins underwent structural changes characterized by a more extensive interaction with lipids. Both the heavy and light chain subunits of the neurotoxins were involved in the process. The change in the nature and extent of toxin-lipid interaction occurred in the pH range 4-6 and was not influenced by the presence of polysialogangliosides. The present data are in agreement with the idea that botulinum neurotoxins enter into nerve cells from a low pH intracellular compartment.

scholarly journals Influence of Erbium Doping on Dielectric Properties of Zinc Borotellurite Glass System

2016 ◽  
Vol 846 ◽  
pp. 161-171 ◽  
Author(s):  
Siti Shafinas Zulkefly ◽  
Halimah Mohamed Kamari ◽  
Muhammad Nor Azlan Abdul Azis ◽  
Wan Mohd Daud Wan Yusoff
Keyword(s):  
Dielectric Properties ◽  
Molar Volume ◽  
Structural Changes ◽  
Low Frequency ◽  
Interfacial Polarization ◽  
Xrd Analysis ◽  
Glass System ◽  
Response Measurement ◽  
Xrd Pattern ◽  
Higher Temperature

Glasses of the system {[ (TeO2)70 (B2O3)30]70 (ZnO)30}100-y (Er2O3)y containing different concentration of Er2O3 (ranging from 0 to 5 mol %) was prepared from melt-quenching technique. The structural changes were studied by XRD analysis and FTIR analysis. The XRD pattern shows the glasses are amorphous. The higher concentration of Er2O3, the more unit of TeO3 would transform to TeO4 and formation of B-O vibrational groups. The density and molar volume was obtained attribute to non-bridging oxygen (NBO) and are found the density and molar volume of the glass system are increasing. The densities range from 3630 kg/m3 to 3960 kg/m3. The dielectric constant ε’ and dielectric loss factor ε’’ which were characterized in the frequency range 10-2 – 106 Hz over temperature range 50°C – 200 °C, show a larger value at lower frequency and higher temperature (above 110°C ). The results of dielectric response measurement show that interfacial polarization at low frequency, and orientation polarization at intermediate and high frequency.Keywords: Dielectric properties; Activation Energy; Rare Earth; Polarization; Non-Bridging Oxygen;

Structural Changes in Confined Lysozyme

2009 ◽  
Vol 131 (7) ◽  
Author(s):  
Eduardo Reátegui ◽  
Alptekin Aksan
Keyword(s):  
Fourier Transform ◽  
Infrared Spectroscopy ◽  
Structural Changes ◽  
Heat Denaturation ◽  
Cryogenic Temperatures ◽  
Key Factors ◽  
Denaturation Temperature ◽  
Novel Technologies ◽  
Factors Influencing ◽  
The Matrix

Proteins and enzymes can be encapsulated in nanoporous gels to develop novel technologies for biosensing, biocatalysis, and biosynthesis. When encapsulated, certain macromolecules retain high levels of activity and functionality and are more resistant to denaturation when exposed to extremes of pH and temperature. We have utilized intrinsic fluorescence and Fourier transform infrared spectroscopy to determine the structural transitions of encapsulated lysozyme in the range of −120°C<T<100°C. At cryogenic temperatures encapsulated lysozyme did not show cold denaturation, instead became more structured. However, at high temperatures, the onset of heat denaturation of confined lysozyme was reduced by 15°C when compared with lysozyme in solution. Altered dynamics of the solvent and pore size distribution of the nanopores in the matrix appear to be key factors influencing the decrease in the denaturation temperature.

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