The role of glycine and prolines in connective tissue fiber staining with hydrogen bonding dyes

Extensive hydrogen bonding of dyes to connective tissue fibers is made possible by the high content of the amino acids proline and glycine in elastin and collagens. Proline confers an extended polypeptide structure and glycine is the only amino acid whose specific side group, -H, is so small that it forms no obstacle to hydrogen bonding between the peptide group and external molecules. Thus, a high proportion of the peptide groups in fibrous proteins are directly accessible to hydrogen bonding groups dye molecules.