C-13 CHEMICAL-SHIFTS OF 20 FREE AMINO-ACIDS AND THEIR USE IN DETECTION BY NMR OF FREE AMINO-ACIDS IN INTACT PLANTS OF ARABIDOPSIS

We required C-13 chemical shifts of the common amino acids to study am ino acid metabolism in intact Arabidopsis plants using C-13 nuclear ma gnetic resonance spectroscopy. However, a set of C-13 chemical shifts of amino acids obtained under uniform conditions was not available in the literature. In this paper we report chemical shifts for the 20 com mon amino acids at 25 degrees C in phosphate buffer at pH 7.3, using 2 ,2,dimethyl-2-silapentane-5-sulfonic acid, sodium salt (DSS) as an int ernal reference. The validity of using these data to examine metabolis m in intact tissues was confirmed by studies detailing the C-13 shifts , from natural abundance data, of 8 of these amino acids in intact pla nts of Arabidopsis thaliana. The resonances of individual carbons in p lanta are within 0.2 ppm of those in buffer. Therefore, amino acids ca n be detected in planta from the fewer resonances arising from positio nal enrichment, which we demonstrate for L-[beta-C-13] serine. These d ata should be useful to other studies of amino acid metabolism as well as studies of peptides and proteins.