Denaturation of Proteins
Abstract
This experiment aimed to study the effect of various denaturants on albumin and casein protein extracts through viscosity measurements. 5 mL samples of native and denatured protein solutions were prepared, using -mercaptoethanol, urea and SDS as denaturants for albumin, and NaOH, NaCL, HCL, -mercaptoethanol, urea and SDS for casein. 5 mL blank solutions for each denaturant used were also prepared. The viscosity of the solutions were determined using Ostwald viscometer.
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Discussion of Data and Results
Denaturation of proteins is a reversible—and sometimes irreversible—process that involves the disruption and possible destruction of both the secondary and tertiary structures. Since denaturation reactions are not strong enough to break the peptide bonds, the primary structure (sequence of amino acids) remains the same after a denaturation process. Denaturation disrupts the normal alpha-helix and beta sheets in a protein and uncoils it into a random shape.
Generally, protein denaturation is to be avoided, since proteins are best studied as close to their native state as possible. However, denaturation is sometimes done deliberately. For example, in determining the rates of enzyme reactions, proteins are quickly denatured to stop enzyme reactions. Also, to study the detailed nature of the unfolding and refolding of their polypeptide chains, proteins are deliberately denatured. Denaturation of proteins usually result to decreased solubility, altered water binding capacity, loss of biological activity, destruction of toxins, increased intrinsic viscosity, and inability to crystallize. That way, this process can be a useful way in separating proteins from other classes of biological molecules during purification.
In tertiary structures, four types of bonding interactions between "side chains" occur—hydrogen bonding, non-polar hydrophobic interactions, salt
This experiment aimed to study the effect of various denaturants on albumin and casein protein extracts through viscosity measurements. 5 mL samples of native and denatured protein solutions were prepared, using -mercaptoethanol, urea and SDS as denaturants for albumin, and NaOH, NaCL, HCL, -mercaptoethanol, urea and SDS for casein. 5 mL blank solutions for each denaturant used were also prepared. The viscosity of the solutions were determined using Ostwald viscometer.
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Discussion of Data and Results
Denaturation of proteins is a reversible—and sometimes irreversible—process that involves the disruption and possible destruction of both the secondary and tertiary structures. Since denaturation reactions are not strong enough to break the peptide bonds, the primary structure (sequence of amino acids) remains the same after a denaturation process. Denaturation disrupts the normal alpha-helix and beta sheets in a protein and uncoils it into a random shape.
Generally, protein denaturation is to be avoided, since proteins are best studied as close to their native state as possible. However, denaturation is sometimes done deliberately. For example, in determining the rates of enzyme reactions, proteins are quickly denatured to stop enzyme reactions. Also, to study the detailed nature of the unfolding and refolding of their polypeptide chains, proteins are deliberately denatured. Denaturation of proteins usually result to decreased solubility, altered water binding capacity, loss of biological activity, destruction of toxins, increased intrinsic viscosity, and inability to crystallize. That way, this process can be a useful way in separating proteins from other classes of biological molecules during purification.
In tertiary structures, four types of bonding interactions between "side chains" occur—hydrogen bonding, non-polar hydrophobic interactions, salt
References: Holum, J. Organic & Biological Chemistry. Von Hoffman Press, Inc. 1996 Reithel, F. Concepts in Biochemstry. McGraw-Hill, Inc. New York. 1967 Switzer, R. Experimental Biochemistry. NY: W.H. Freeman & Company. 1999 http://www.elmhurst.edu/~chm/vchembook/568denaturation.html. Denaturation of Proteins. Date accessed: July 4, 2008 http://class.fst.ohio-state.edu/fst605/605p/ProteinDenaturation.pdf. Protein Denaturation. Date accessed: July 4, 2008