Desmosine is a component of elastin and cross links with its isomer, isodesmosine, giving elasticity to the tissue.

Detection of desmosine in urine, plasma or sputum samples can be a marker for elastin breakdown due to high elastase activity related to certain diseases.

[1][2] Desmosine and its isomer isodesmosine are both composed of four lysine residues, allowing for bonding to multiple peptide chains.

The four lysine groups combine to form a pyridinium nucleus, which can be reduced to neutralize positive charge associated, and increase the hydrophobicity.

Currently, mass spectrometry is used and aids in the release of characteristic fragments which would help with differentiation, especially in larger peptides.

The tropoelastin initially lacks any of these complex binding molecules, and has a similar make up to that of the final stage elastin, however it contains a greater amount of lysine side chains, which directly corresponds with desmosines later found.

These precursor molecules are processed through Dehydrogenation, along with dihydroD, and ultimately form elastin bound with desmosine.

It has been suggested that the secondary cross-linking occurs with either desmosine or lysinonorleucine, which maintains an alpha helix conformation in alanine rich sections on peptides.

[3] Both isodesmosine and desmosine can have similar bonding sites in elastin, though it rarely shown this way in nature.

Demosine can not only be found in elastin, but also in urine, plasma, sputum, and there are different ways to identify and measure these quantities.

Currently, mass spectrometry is used and aids in the release of characteristic fragments which would help with differentiation, especially in larger peptides.

Desmosine is one of the oldest biomarkers and was developed in the 1960s, but the first time it was correlated to lung elastin content was in the 80s through urinary excretion.