Peptide bonds are formed by a biochemical reaction ... while others have polar but uncharged side chains. The chemistry of amino acid side chains is critical to protein structure because these ...

This longevity is particularly surprising considering the relatively short half-life (just 500 years) of peptide bonds — the chemical links that hold proteins together. So, how can collagen last ...

For a summary of recent work, see Fromageot, C., and Jutisz, M., “The Chemical Structure of Proteins”, 82 (J. and A. Churchill, Ltd., London, 1953).