Amino acids DABS deriv

Stocchi, V., Palma, F., Piccoli, G., Biagiarelli, B., Magnani, M., Masat, L., and Cucchiarini, L., Analysis of amino acids as DABS-derivatives with a sensitivity to the femtomole using RP-HPLC narrow-bore columns, Amino Acids, 3, 303, 1992. 

Essential oils consist of volatile, lipophilic substances that are mainly hydrocarbons or monofunctional compounds derived from the metabolism of mono- and sesquiterpenes, phenylpropanoids, amino acids (lower mass aliphatic compounds), and fatty acids (long-chain aliphatic compounds). Unlike fatty oils, essential oils do not leave a grease stain when dabbed on filter paper. 

Enkephalin derivatives selective for ju- receptors have also been prepared by cyclization between a o-amino acid and the C-terminus. Tyr-c cZo[N -D-Dab-Gly-Phe-Leu] (216, Fig. 7.42 Dab = a,7-diaminobut5rric acid) (684)ex-hibits both high potency and preceptor selectivity (Table 7.14), whereas the corresponding linear peptide [D-Dab, Leu ]enkephalinamide... 

For urinary amino adds [22], 0.5 ml of urine was mixed with 0.5 ml of 0.5 M sodium bicarbonate and 2 ml of DABSCl (2 g P in acetone). The reaction mixture was maintained at pH 8.5-9.0 and 25-26 "C for 30 min. The filtrates were directly applied to a Cjg column for HPLC separation. Interfering amino compounds present in the urine also form derivatives with DABSQ, but may be removed by extraction with chloroform. Ammonia reacts readily with DABSCl, resulting in a derivative coeluted with DABS-methionine. Furthermore, ammonia may consume so much DABSCl that it seriously interferes with the derivatization of amino acids. Therefore the ammonia should be removed by lyophilizing the samples at pH 8.9 before derivatization. This method allowed the detection of urinary amino acid down to concentrations of about 16mgl ... 

Matysik, G. Separation of DABS derivatives of amino acids by multiple gradient development (MGD) in thin-layer chromatography. Chromatographia 1996, 43, 301-303. 

Figure 13 Results of thin-layer chromatography of DABS-amino acid derivatives. (Reprinted from Ref. 12, with permission.)...

Spontaneous hydrolysis of amphomycin in water solution over about two months was observed at room temperature, probably because of the acidity provided by the free carboxyl groups. A decapeptide (37) and N-acylaspartic acid were thus obtained. Treatment of the decapeptide with nitrous acid destroyed the methylaspartic acid residue and transformed DABc threonine. Dansylation showed that methylaspartic acid was the only N-terminal amino acid the fact that no derivative was obtained from pipecolic acid or DAB, supported the presence of a diketopiper-azine. The possibility that the diketopiperazine could have been formed under mild conditions of degradation was ruled out by experiments... 

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