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Unformatted text preview: -An amino acid can never exist as an uncharged compound, regardless of the pH of the solution-It would have to lose a proton from + NH 3 before it could lose one from COOH, which would be like a weak acid being more acidic than a strong acid, which is clearly not possible 17.6 Peptide Bonds and Disulfide Bonds -Peptide and disulfide bonds are the only covalent bonds that hold amino acids together -Peptide Bonds o The amide bonds that link amino acid residues are called peptide bonds o A peptide bond has partial double-bond character because of electron delocalization which prevents free rotation -Disulfide Bonds o When thiols are oxidized under mild conditions, they form disulfides, which are compounds with SS bonds o Disulfides can be reduced to thiols...
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- Spring '07