Amino zwitterion bridges

Prolonged boiling with HCI hydrolyses the peptide linkages (shown as thick bonds) and breaks the -.air down into the constituent amino acids. These crystallize as the zwitterions at about neutral pHs and the mixture of NaOAc and HCI provides a buffer solution. Hair is much cross-linked by disulfide bridges and these do not break down under the hydrolysis conditions so intact cystine emerges. 

Scheme 1 Low-energy structures for the complex of and Trp. Structures can be classified as salt-bridge (SB interaction between the positive metal ion and the negative carboxylate of the zwitterionic amino acid) or charge solvation (CS interaction of the metal ion with Lewis-basic sites of the canonical amino acid). Nomenclature of the various structures further includes the main binding sites of the amino acid...

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