Desmosine and isodesmosine (collectively known as desmosines), two unnatural amino acids unique to mature elastin in humans, have been widely discussed as being potential biomarkers of disorders, which involve connective tissue and whose clinical manifestations result in elastin degradation. In particular, experimental data accumulated over the last 40 years have demonstrated that patients with chronic obstructive pulmonary disease (COPD) excrete higher amounts of urinary desmosines than healthy controls. Based on this evidence, it has been speculated by several authors that these cross-links may be potential biomarkers of COPD with clinical significance. Nevertheless, a strict correlation between the amount of these amino acids and the severity of the disease still has to be demonstrated. For this reason, the debate on the opportunity to consider desmosines as biomarkers of COPD is still open, and the development of sophisticated methods aimed at obtaining very precise measurement of their concentration is still considered technically challenging. The aim of this chapter is to trace the history of this debate through the presentation and discussion of a large number of articles dealing with the detection and quantification of desmosines in different biological fluids, from early years until the present.
Part of the book: Amino Acid
The current chapter was designed to keep the reader informed about the present status of pulmonary proteome. Taken together, the results documented here demonstrate that, after a decade of activity, proteomics of pulmonary diseases is catching up with its promise. The constantly growing number of reports in this area supports the view of this approach as one of the decisive methodological tools for the identification/characterization of disease-associated proteins. In terms of experimental procedures, the basic options available for proteomic investigations consist in the identification of proteins through the use of gel-based or gel-free techniques followed by MS. Obviously, the question arises of whether sophisticated technologies (such as the non-gel-based proteomic procedures) may currently be more fruitful, in terms of candidate protein marker identification, than “conventional” (read electrokinetic) approaches. In light of the versatility and high degree of reproducibility shown by these new potent strategies, a positive answer is perhaps not surprising. Nevertheless, as documented in this chapter, despite being less sophisticated than competing ones, gel-based techniques still represent a widely used procedure able to generate a reliable protein “fingerprint” and to produce qualitative and quantitative information on the protein patterns of a variety of human fluids.
Part of the book: Electrophoresis