Recommended method for the analysis of amino acids in biological materials

Myofibrillar protein catabolism in rat steroid myopathy measured by 3-methylhistidine excretion in the urine

The fractional rate of breakdown of myofibrillar protein in rat skeletal muscle was measured during subcutaneous cortisone acetate treatment (10 mg/100 g body weight per day). The daily urinary excretion of 3-methylhistidine divided by the 3-methylhistidine pool of the skeletal muscle was used to determine the fractional breakdown rate of myofibrillar protein. The mean fractional breakdown rate remained within the normal range throughout the first 5 days, but decreased significantly from the 16th day of treatment. When the daily 3-methylhistidine excretion was divided by the creatinine excretion, the rate showed the same trend of change. These results strongly suggest that the loss of myofibrillar protein induced by cortisone administration is not caused by increased breakdown but by decreased synthesis.

Profiles of strongly polar and less polar acids obtained from human blood, plasma and serum by two-step ultrafiltration

A two-step ultrafiltration method combined with anion-exchange chromatography is described for the separation of lipophilic and strongly lipophobic acids occurring in human blood, serum and plasma. After treatment with diazomethane, the acid fractions are separated further by gas chromatography. The acids were identified by their mass spectra. Profiles obtained from the strongly acidic fraction of blood samples of healthy individuals are characterized by main peaks corresponding to organic phosphoric acid esters. The peaks are absent in plasma and serum.

Automated analysis of hexosamines by high-performance liquid chromatography with photometric and fluorimetric postcolumn labeling using 2-cyanoacetamide

Glucosamine and galactosamine were well separated in ca. 60 min on a Hitachi 2617 column (polystyrene sulfonate type, 4 mm X 25 cm) with a borate buffer (pH 7.5) containing sodium chloride. The hexosamines in the eluate were monitored fluorimetrically and photometrically at 331 (excitation)/383 (emission) and 276 nm, respectively, by postcolumn labeling with 2-cyanoacetamide. This simple method allowed the simultaneous, automated determination of 10-500 nmol of glucosamine and galactosamine with high reproducibility. This method was applied successfully to the analysis of hexosamines in some glycoconjugates.

Quantitation of the epsilon-(gamma-glutamyl)lysine cross-link using a high-speed amino acid analyzer without purification of the dipeptide. Application to enzymatic digested mixtures of keratin and the membranous fraction of human stratum corneum

epsilon-(gamma-Glutamyl)lysine in an enzymically digested mixture of keratin and the membranous fraction of human stratum corneum was directly quantitated using a high-speed amino acid analyzer without purification of the dipeptide. The analytical conditions were improved so that epsilon-(gamma-glutamyl)lysine clearly separated from other amino acids and eluted directly after tyrosine. The enzymatically digested mixtures were filtered through an Ultra Free membrane and deammoniated before analysis. By our present method, keratin and the membranous fraction of human stratum corneum were analyzed and 5.8 and 43.5 nmol/mg of epsilon-(gamma-glutamyl)lysine, respectively, were detected.

Screening of organic acids in urine by chemical ionization mass spectrometry

A method has been developed for qualitative screening of carboxylic acids in human urine. The method uses direct chemical inoization mass spectrometry with isobutane as reagent gas. The carboxylic acids are separated from the urine samples by ion exchange. Normal carboxylic acid profiles have been determined and are compared with the profiles of patients suffering from certain metabolic disorders.