THE DENATURATION OF EGG ALBUMIN BY ULTRA-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.

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

The Journal of General Physiology ◽

10.1085/jgp.27.2.101 ◽

1943 ◽

Vol 27 (2) ◽

pp. 101-111 ◽

Cited By ~ 9

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.

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Overall study on molecular pathways of skin cancer derived from Ultra- violet radiation as an environmental threat

Environment Conservation Journal ◽

10.36953/ecj.2015.se1665 ◽

2015 ◽

Vol 16 (SE) ◽

pp. 547-555

Author(s):

Hossein Yousefi ◽

Samira Mohammadzadeh ◽

Arsalan Irompour ◽

Neda Shenasifam ◽

Elham Roshandel ◽

...

Keyword(s):

Skin Cancer ◽

Ultraviolet Radiation ◽

Cell Carcinoma ◽

Uv Radiation ◽

Ultra Violet ◽

Ozone Layer ◽

Molecular Pathways ◽

Ultra Violet Radiation ◽

Environmental Threat ◽

Violet Radiation

An important part of solar radiation is considered to be Ultraviolet radiation. Though through passing ozone layer it is progressively filtered. Due to the depletion of the ozone layer, the filtering activity of the latter is reduced and as a result more UV radiation, UVB in particular, reaches the Earth’s surface. Ultraviolet radiation is composed of three different wavelengths: UVA, UVB and UVC. Although UVC isn't a cause of skin cancer, UVA and UVB play different roles as for tanning, burning, and photo aging. As a matter of fact, Ultraviolet light can damage DNA in the epidermis. However, through apoptosis the damaged DNA is repaired or deleted in order to prevent the generation of cancer. It is believed that a deficient apoptotic mechanism might make individuals liable to skin cancer. The main factor for generating skin cancer is considered to be the UV radiation which could cause basal cell carcinoma, squamous cell carcinoma and possibly melanoma. For the maintenance of hemostasis, apoptosis plays a key role. This is done via many molecular pathways such as the pathways of tumor suppressor genes like P53, P21 and also the expression of BAX proteins. These pathways are involved in apoptosis after UV radiation. It is clear that the malfunction of these genes and proteins can lower the tolerance of body and cause cancer. The goal of this article is to investigate the molecular pathways of skin cancer derived from Ultra violet radiation as an environmental threat.

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