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8/4/2019 Tertiary Protein Structure
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Tertiary Protein Structure
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Tertiary Protein Structure
Refers to three-dimensionalstructure of a single protein
molecule. Result from the interactions
between amino acid sidechain that are widelyseparated from each other
with a peptide chain.
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Interaction Responsible forTertiary Structure
Disulfide bonds
Hydrophobicinteractions
Hydrogen bonds Ionic Bond
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Covalent Disulfide bonds
usually formed fromthe oxidation of sulfhydryl (-SH)groups
2 RSH RS-SR + 2 H+ + 2 e-
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Covalent Disulfide bonds
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Hydrogen bond
Attractive interaction ofa hydrogen atom withan electronegative atom, such as
nitrogen, oxygen or fluorine, thatcomes from another moleculeor chemical group
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Hydrogen bond
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Ionic Bond
a type of chemical bond formedthrough an electrostatic attractionbetween two oppositely
charged ions. Also called salt bridge, always
involve the interaction between
acidic side chain and a basic sidechain.
COOH = COO- and NH2 = NH3+
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Ionic Bond
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Hydrophobic interactions
Result when two non polar sidechains are close to each other. Inaqueous solution, many proteins
have their polar R groups outward,toward the aqueous solvent andtheir non polar R groups inward.
The non polar R groups theninteract with each other.
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Protein Hydrolysis
the breakdown of protein into smallerpeptides and free amino acid.
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Protein Denaturation
Involves the disruption and possibledestruction of both the secondaryand tertiary structures. Since
denaturation reactions are notstrong enough to break the peptidebonds, the primary structure
(sequence of amino acids) remainsthe same after a denaturationprocess. Denaturation disrupts thenormal alpha-helix and beta sheetsin a protein and uncoils it into a
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Protein Denaturation
Denaturation occurs because thebonding interactions responsible forthe secondary structure (hydrogen
bonds to amides) and tertiarystructure are disrupted. In tertiarystructure there are four types ofbonding interactions between "side
chains" including: hydrogen bonding,salt bridges, disulfide bonds, and non-polar hydrophobic interactions. whichmay be disrupted. Therefore, a
variety of reagents and conditions cancause denaturation.
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Protein Denaturation Factors
Heat
Alcohol Disrupts Hydrogen
Bonding Acids and Bases Disrupt
Salt Bridges
Reducing Agents DisruptDisulfide Bonds
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Heat
Heat can be used to disrupt hydrogenbonds and non-polar hydrophobicinteractions. This occurs because heatincreases the kinetic energy and
causes the molecules to vibrate sorapidly and violently that the bondsare disrupted. The proteins in eggsdenature and coagulate during
cooking. Other foods are cooked todenature the proteins to make iteasier for enzymes to digest them.Medical supplies and instruments aresterilized by heating to denature
proteins in bacteria and thus destroy
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Alcohol Disrupts HydrogenBonding
Hydrogen bonding occurs betweenamide groups in thesecondary protein structure.
Hydrogen bonding between "sidechains" occurs in tertiary protein structure in a variety
of amino acid combinations. All ofthese are disrupted by the additionof another alcohol.
http://www.elmhurst.edu/~chm/vchembook/566secprotein.htmlhttp://www.elmhurst.edu/~chm/vchembook/567tertprotein.htmlhttp://www.elmhurst.edu/~chm/vchembook/567tertprotein.htmlhttp://www.elmhurst.edu/~chm/vchembook/566secprotein.html8/4/2019 Tertiary Protein Structure
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Alcohol Disrupts HydrogenBonding
A 70% alcohol solution is used as adisinfectant on the skin. Thisconcentration of alcohol is able topenetrate the bacterial cell wall and
denature the proteins and enzymesinside of the cell. A 95% alcoholsolution merely coagulates theprotein on the outside of the cell wall
and prevents any alcohol fromentering the cell. Alcohol denaturesproteins by disrupting the side chainintramolecular hydrogen bonding.New hydrogen bonds are formed
instead between the new alcohol
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What is the difference between thealpha-helix and the beta-sheet protein
conformations?
Alpha-helix and beta-sheetconformations are the two main types ofsecondary structure of a protein molecule.According to the primary protein structure
its secondary structure can be of one typeor the other.
In the alpha-helix structure the polypeptidecurls longitudinally by the action of
hydrogen bonds forming a spiral, or helix.In the beta-sheet conformation the proteinis more distended and the hydrogenbonds form a zig-zag-shaped proteinstructure called B-strand. Many assembledbeta-strands make a beta-sheet.
a s pro e n ena ura on s
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a s pro e n ena ura on sthere any change in the primary
structure when a protein is
denatured? Secondary, tertiary and quaternarystructures of proteins are spatialstructures. Denaturation is
modification in any of these spatialstructures that makes the proteindeficient or biologically inactive.
After denaturation the primaryprotein structure is not affected.
What Is the Difference
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What Is the DifferenceBetween an Ionic and Covalent
Chemical Bond? In an ionic bond, the atoms are boundtogether by the attraction betweenoppositely-charged ions. For example,sodium and chloride form an ionic
bond, to make NaCl, or table salt. In acovalent bond, the atoms are boundby shared electrons. If the electron isshared equally between the atoms
forming a covalent bond, then thebond is said to be nonpolar. Usually,an electron is more attracted to oneatom than to another, forming a polarcovalent bond. For example, the
atoms in water H2O are held