Monitoring compensation of patients with cystinuria by spectrophotometric method

The presented bachelor's thesis deals with the issue of cystinuria, hereditary metabolic disorder of transport of dibasic amino acids. The objective of the thesis was to select a spectrophotometric method of determining cystine in urine, to find the most suitable conditions for determining cystine in a clinical laboratory and to apply the method on samples of urine of patients with cystinuria. For determining cystine in urine, the method using coloured red and violet product of cystine reaction was selected after reduction to cystine with ninhydrin agent in acid environment. Absorption spectra of standard of cystine and urine in a patient with cystinuria were measured with the maximum at 560 nm. Interference of ornithine and other amino acids was excluded. Kinetics of reduction of cystine to cysteine was measured. The most suitable time of reduction is 5 minutes, in longer time cysteine is oxidized to cystine. Kinetics of creation of a coloured product was measured. The maximum absorption in heating the reaction mix with ninhydrin to 100řC was reached after 10 minutes, later only degradation processes and absorbance reduction takes place. Stability of a coloured product of reaction in light was tested. The product is stable for ten minutes, then absorbance drops by 8% after 45 minutes. Linearity of..