Automatic synthesis of L-[beta-C-11]amino acids using an immobilized enzyme column

We have developed a system for the automatic synthesis of L-[beta-C-11]amin o acids for i.v. injection by means of enzyme-mediated reactions from (CO2) -C-11 via (CH3I)-C-11 and D,L-[beta-C-11]alanine as labeled intermediates. This system, which incorporates an ultrafilter cartridge sterilized by elec tron beam irradiation and a column packed with immobilized enzymes, was eff ective for eliminating enzymes and endotoxins that may contaminate the prod uct. Using this system, 1.3 +/- 0.5 GBq of 5-hydroxy-L-[beta-C-11]tryptopha n with a radiochemical purity of 97.1 +/- 0.6% and a specific activity of 3 9.6 +/- 8 GBq/mu mol a pH value of 4 could be obtained in about 32 min (n = 3, at EOS). No endotoxin, enzyme, or bacteria was detected in the product. L-[beta-C-11]dihydroxyphenylalanine (L-[beta-C-11]DOPA) was also synthesiz ed using this system. (C) 2000 Elsevier Science Ltd. All rights reserved.