Synthesis of neodesmosine-d₄ and quantitative LC-MS/MS analysis of neodesmosine in biological samples

Elastin is an important protein responsible for elasticity of cells and tissues in animal bodies. Although its detailed structure has not yet been elucidated, its crosslinking structure is considered to play an important role in expressing elasticity. Neodesmosine, which was also isolated from eggshell membrane, is one of the crosslinking amino acids of elastin. In this study, the synthesis of an isotopically labeled form of neodesmosine, neodesmosine-d4 (1-d4), was completed in four steps in 20 % overall yield. Quantitative LC-MS/MS analysis of neodesmosine in elastin and eggshell membranes of chicken and quail using 1-d4 as an internal standard was then conducted, revealing that these eggshell membranes contained 0.195 and 0.287 mu g of neodesmosine, respectively, while the amount was almost double (0.539 mu g) in elastin of bovine ligamentum. This result will aid in the elucidation of the structures and the correlation between elastin and eggshell membranes.