[Column chromatographic separation of N-B,N-G-dimethyl arginine, N-G,N'G-dimethyl arginine, N-G-monomethyl arginine, N-epsilon-monomethyl lysine, N-epsilon-dimethyl lysine and N-epsilon-trimethyl lysine]

Determination of methylated basic, 5-hydroxylysine, elastin crosslinks, other amino acids, and the amino sugars in proteins and tissues

Analytical single-column chromatographic methods have been developed for determining all methylated basic amino acids, isodesmosine, desmosine, the amino sugars glucosamine and galactosamine, the diastereoisomers of 5-hydroxylysine, and related compounds at picomole levels in protein and tissue hydrolysates. Complete resolution of all these unique basic amino acids as discrete peaks was achieved in 5.4 on a 50 X 0.28-cm microcolumn of Dionex type DC-4A spherical resin (9.0 +/- 0.5 micron) using updated instrumentation commonly available for amino acid analysis. The column was operated at 5.65 ml/h with two 0.35 M sodium citrate buffers (pH 5.700 and 4.501), at two temperatures (31.5 and 73 degrees C). Excellent resolution of all omega-N-methylarginines and related compounds was also achieved in 3 h using a 17.5 X 0.28-cm microcolumn of Dionex DC-5A resin (sized to 6.0 +/- 0.5 microns), two citrate buffers (0.21 M Na+, pH 5.125; 0.35 M Na+, pH 5.700), a buffer flow rate of 5.75 ml/h, and a temperature of 52 degrees C. Complete separation of all other amino acids found in protein or tissue hydrolysates including S-carboxymethyl cysteine, 4-hydroxyproline, methionine S,S-dioxide, and the amino sugars was also carried out in 95 min using a 23.5 X 0.28-cm microcolumn of Dionex DC-5A resin. The use of purified microcolumn buffers gave smooth baselines without interference from artifacts or minor hydrolysate components. The major advantages of these methods are: first, their high resolving power; second, their high sensitivity which is comparable and in some aspects superior to the newer instruments; and third, their high reproducibility (100 +/- 2.5%) and low operating costs. These methods should be especially valuable for determining myosin, actin, and elastin in tissue hydrolysates from the amounts of N tau-methylhistidine, desmosine, or isodesmosine present, respectively, and for studying protein methylation, hydroxylation, cross-linking formation, and the turnover rates of contractile and connective tissue proteins in biological systems.

Improved high-performance liquid chromatographic method for the determination of 6-N,N,N-trimethyllysine in plasma and urine: biomedical application of chromatographic figures of merit and amine mobile phase modifiers

An internally standardized method for the determination of 6-N,N,N-trimethyllysine in human plasma, human urine, rat plasma, rat urine and hydrolyzed rat urine is described. This methylated amino acid and the procedural internal standard 6-N,N,N-trimethyllysine were isolated from the sample matrices using short ion-exchange columns and detected following high-performance liquid chromatography using a postcolumn reaction (o-phthalic-dicarboxaldehyde-2-mercaptoethanol) and fluorometric detection. The reliable detection limit for 6-N,N,N-trimethyllysine was 0.2 nmol/ml in 200 microliters of human plasma. The chromatographic separation exploits the unique properties of a novel tertiary amine mobile phase modifier, 3-(N,N-dimethylamino)-1,2-propanediol. The capacity factor and "Chromatographic Figures of Merit" (including peak asymmetry and relative system efficiency) were calculated for the chromatographic peak representing 6-N,N,N-trimethyllysine in over 2200 injections made while evaluating 900 biological specimens.