Chiral connections in urolites

Recent studies have shown increasing in the content of D-amino acids in the proteins of various tissues of the human body in the process of aging. It is known that significant changes in the balance of L- and D-amino acids are observed in various pathological processes. One of the most common pathologies in the human is urolithiasis, in the genesis of which there are still many questions. The purpose of this work is to identify D-forms of amino acids in uroliths and a comparative analysis of their contents depending on the mineral composition of urinary stones and human age. 19 samples of uroliths of mono- and polymineral composition were studied, in which whewellite, weddellite, struvite, newberiite, uric acid, carbonate-hydroxylapatite were identified. The chronological age of people who provided pathogenic biominerals was 22-75 years. Acid hydrolysis in 6 M HCl at 105 °C for 12 hours was used to isolate individual amino acids from uroliths. Identification and quantification of the enantiomers of amino acids was carried out by gas chromatography (chromatograph GC-17A, Shimadzu, column Chirasil-L-Val). In the studied uroliths, D-forms are established for three amino acids: alanine, aspartic acid, and glutamic acid. Research results have shown that there is a relationship between the ratio of D and L amino acids and the mineral component of uroliths. It is noted that the maximum content of D-aspartic acid is characteristic of oxalic stones. In the presence of impurities of calcium oxalate crystals (wevellite and or weddellite) in phosphate and urate uroliths, elevated values of D-Asp are observed. In this connection, an assumption was made about an increase in the degree of racemization of the aspartic acid in the presence of oxalic acid ions in pathogenic biomineral formations.