PROTIEN DENATURATION (1) (1).pptx by Medha Mishra

From the University department of biotechnology hazaribagh Jharkhand Vinoba Bhave University Hazaribagh Jharkhand. Student of semester 1.

1. PROTEIN DENATURATION MEDHA MISHRA Roll No. 29 University Department of Biotechnology Vinoba Bhave University

2. CONTENTS : Introduction Definition Types Characteristics Causes Temperature Denaturation Ph Denaturation Denaturation By Organic Solvent Techniques To Study Protein Denaturation Conclusion References

3. INTRODUCTION A loss of 3-D structure of a protein is called Protein Denaturation. Proteins can be denatured not only by extremes of PH, by certain miscible solvents such as alcohol, acetone or by certain solvent or guanidine hydrochloride or by detergent such as SDS. If proteins in a living cell denatured it results in disruption of cell activity and cell death. Each of these denaturing agents reprints a relatively mild treatment and no covalent bonds in the polypeptide chain are broken. Organic solvents urea and detergents act by disrupting the hydrophobic interacting that make up the stable core of globular protein extremes of PH alter the net change of the protein, causing electrostatic repulsion and disruption of hydrogen bonding. The denatured state of this various treatments are not equal.

4. DEFINITION: Denaturation is the process of the modification of the molecular structure of a protein. This involves the breakdown of bonds such as hydrogen bonds and covalent bonds (disulfide bonds (S-S). Proteins generally have a compact globular shape or are “folded” instead of having random structures. Additionally, denaturation can be reversible or irreversible. For example, a fried egg’s proteins can’t return to their original state. Cooling warmed milk consequently causes the proteins in the milk to revert to their original form.

5. TYPES There are basically two types of protein denaturation: Cooperative protein denaturation Non-cooperative protein denaturation

6. Cooperative Protein Denaturation This are very common type of denaturation in which interaction is broken and the protein is denatured. This is called as cooperative protein denaturation. Non Cooperative Protein Denaturation This is very rare type of protein denaturation where temperature increases and where interaction broken one by one.

7. CHARACTERISTICS LOSS OF SOLUBILITY : Decrease in solubility is one of the characteristics of denatured protein. LOSS OF BIOLOGICAL FUNCTIONS : Most of the biological function when they are denatured . Example - Enzymes lose their activity because the substrate can no longer bind and because the amino acid residues involved in stabilising the substrate transition straight are in no longer position to do. INCREASE IN PROTEOLYTIC ENZYMES : As most native protein are more resistant to the action of proteolytic enzymes , but as they gets denatured, there is an increase in proteolysis.

8. CAUSES Proteins are denatured when bonds holding the secondary and tertiary structures together are disrupted by an external stress.  External stresses  consist of conditions and solvents that cause denaturation , such as temperature, pH, heavy metals, exposure to UV light and radiation.

9. TEMPRATURE DENATURATION When proteins are exposed to increasing temperature, a number o f bonds in a protein molecule are broken. As heating continuous some of the cooperative H-bonds in the protein molecule that stabilize the helical structure will began to break. It can be described as a- 1 st order reaction in which the rate constant obeys in normal thermodynamic principle. Thus, the rate constant , Kden can be related to temperature by d.In.Kden / Dt = Eact /Rt2 where , Eact = Activation energy. Denaturation is a thermodynamically favourable process.

10. PH DENATURATION The ionisable groups in amino acids are able to become ionized when changes in pH occur. A pH change to more acidic or more basic conditions can induce unfolding. Acid-induced unfolding often occurs between pH 2 and 5, base-induced unfolding usually requires pH 10 or higher.

11. DENATURATION BY ORGANIC SOLVENT The rate of denaturation of haemoglobin and other proteins by mechanical shaking is strongly affected by organic solvents. A group of solvents, including alcohols and ketones, was found to stabilize proteins at low concentrations, although these same organic solvents denatured proteins at high concentrations.

12. TECHNIQUES TO STUDY PROTIEN DENATURATION SPECTROSCOPIC TECHNIQUES : UV- vis , florescence, and circular dichroism . ANALYTICAL TECHNIQUES : SDS-PAGE, size exclusion, chromatography and x-ray crystallography.

13. CONCLUSION Protein denaturation mainly occurs because the bonding attraction may disrupted. In selectively denaturation is to create a condition where the enzyme will not get denatured or its activity is host. Many other components is preferably precipitate The physical agents with denature the protein are – the mechanical action like cooling and freezing operations. The chemical agents that cause denaturation are many ionizing radiation like x-rays, radioactive rays, ultrasonic radiation ,organic solvent such as alcohol, acetone and anionic detergent such as CDS etc.

14. REFERENCES NARAYAN M.(2015).PROTEINS DENATURATION AND FOLDING: MECHANISM AND APPLICATION.SPRINGER. Grant R.P. Protein denaturation and structural stabilization: John Willey and sons.