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FORCES WHICH STABILIZE TERTIARY STRUCTURE: -In many proteins, one of the important features responsible for establishing the tertiary structure is the formation of disulfide bonds S-S bonds (between cysteines). See Figure in Text (p.51) A major force underlying the acquisition of 3D conformation in all proteins is the formation of noncovalent bonds. The formation of noncovalent bonds is strongly influenced by the aqueous environment. A major factor that influences these reactions is the structure of water itself, which forms a transient network of connections between individual molecules. The major force in this network is the hydrogen bond. -The polarization of the (C=O ) and (N-H or O-H )bonds allows the formation of a hydrogen bond between the two groups. Hydrogen bonds commonly form between the NH and CO groups of the peptide backbone. -Hydrogen bonds also form between amino acids with polar side groups. -Ionic interactions occur between amino acids with oppositely charged groups (i.e.
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Unformatted text preview: between acidic and basic amino acids). The strength of the ionic bond is enormously affected by circumstances. In a solid crystal, the interaction between Na and Cl has a strength comparable to a covalent bond. In solution, water molecules interact with the charged groups - the water molecules shield the charge - and the strength is weakened substantially. The basic amino acids, Lysine, arginine, and histidine , may interact with the acidic amino acids, aspartic acid and glutamic acid . Therefore, a typical ionic interaction in a protein or between two proteins might involve attraction between acidic and basic amino acids.-Hydrophobic interactions occur between amino acids with nonpolar side chains. Tend to aggregate and form the interior of a polypeptide where they are inaccessible to water. Protein structures do exist largely in water where hydrogen and ionic bonds are somewhat shielded. Dynamic- reemphasize...
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This document was uploaded on 11/03/2011 for the course BIOLOGY MCB2010 at Broward College.

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