CHMI-2227EL Lecture Notes - Lecture 12: Royal Aircraft Factory F.E.2, Fetal Hemoglobin, Phenylalanine

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Biochemistry - Day 12 2018.02.28
Denaturing
-Most proteins unfold (denature) under several condition
-Denaturing of proteins involves disruption of secondary and
tertiary structure, depending on the degree of denaturation
-The primary structure of proteins remains unchanged (amide
bonds remain intact, the peptide bonds)
-Denaturation of a protein results in the loss of biological function, therefore they are
no longer biologically active
Denaturation
-Denaturation: the loss of the structural order (secondary, tertiary, quaternary, or a
combination of these) that gives a protein its biological activity, that is, the loss of
biological activity
-Denaturation of proteins can be done by several methods:
-1) Temperature changes
-weak hydrogen bonds are disrupted and proteins unfold, most proteins have a
melting point well below 100 oC
-2) High pressure
-3) UV
-4) Strong acids and bases
-Raising or lowering the pH, alters charges of amino acid side chains (ex. CO2- to
CO2H, or NH3+ to NH2)
-Thereby destroying ionic bonds that hold the polypeptide chains in their 3-D form
-5) Urea (8M ) or guandinium chloride (5M) which disrupt hydrogen bonding and
hydrophobic interactions
-6) Detergents such as sodium dodecyl sulphate which disrupt hydrophobic
interactions (Ex. SDS -> sodium dodecyl sulfate)
-7) Mercaptoethanol (HS-CH2-CH2-OH) which reduces disulphide bonds to
sulfhydryl groups
Denaturation Results
-1) Physical properties: By increasing concentration of urea, this will increase the
viscosity of the protein
-2) Biological properties: By increasing the concentration of urea, the activity will be
reduced and destroyed
-Renaturation: When the denaturing agents are removed, certain denatured proteins
will regain their native structure and their biological activity
-This process is called renaturation
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Document Summary

Most proteins unfold (denature) under several condition. Denaturing of proteins involves disruption of secondary and tertiary structure, depending on the degree of denaturation. The primary structure of proteins remains unchanged (amide bonds remain intact, the peptide bonds) Denaturation of a protein results in the loss of biological function, therefore they are no longer biologically active. Denaturation: the loss of the structural order (secondary, tertiary, quaternary, or a combination of these) that gives a protein its biological activity, that is, the loss of biological activity. Denaturation of proteins can be done by several methods: Weak hydrogen bonds are disrupted and proteins unfold, most proteins have a melting point well below 100 oc. Raising or lowering the ph, alters charges of amino acid side chains (ex. Thereby destroying ionic bonds that hold the polypeptide chains in their 3-d form. 5) urea (8m ) or guandinium chloride (5m) which disrupt hydrogen bonding and hydrophobic interactions.

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