Relative efficiencies of tritium atoms and ionic species in peptide labeling

Abstract

University of C a l i f o r n i a , San Francisco , CA 94143 SUMMARY Glycylglycyl-L-leucine and glycyl-L-leucine d i s p e r s e d on silica-alumina and supported N i c a t a l y s t , were l a b e l e d with t r i t i u m by microwave d i s c h a r g e a c t i v a t i o n of t r i t i u m g a s , as a model t o study t h e optimum c o n d i t i o n f o r l a b e l i n g p e p t i d e s and p r o t e i n s .I n t h e r e a c t i o n , decreasing t h e t r i t i u m p r e s s u r e and i n c r e a s i n g t h e microwave power promote the formation of t r i t i u m i o n s and r e s u l t i n an i n c r e a s e i n s p e c i f i c a c t i v i t y of t h e l a b e l e d product. The h i g h e s t s p e c i f i c a c t i v i t y was achieved with t h e adsorbate molecules as a monolayer on support. s i m i l a r c o n d i t i o n s , amino a c i d s g l y c i n e and L-leucine were less e f f i c i e n t l y l a b e l e d than t h e peptides. Tritium atoms generated by mercury p h o t o s e n s i t i z a t i o n with a uv l i g h t were less

Synthesis of isotopically labelled compounds at Schering‐Plough, an historical perspective

“…Our first attempt at preparing isotopically labelled interferon á 2b , in 1987, also brought us to the National Tritium Labelling Facility for the first time. We attempted thermal atom excitation labelling 28,29 and were not successful. We also tried an iodination/ tritium gas reduction sequence, also without success.…”

“…Conjugation reagents, which react with amino groups in proteins, give more stable labels in vivo. We labelled IFN using the commercially available Bolton-Hunter (29) and PIB reagents (30) and found the PIB reagent gave iodinated IFN with good label stability in vivo. 30 In 2004, we developed two 35 S conjugation reagents (31) and have successfully labelled over ten monoclonal antibodies and other proteins 31 (Figure 2).…”

Microwave‐Enhanced Radiochemistry

“…Wolf et al [28±30] improved the technique by circulating the tritium gas within the labeling system and successfully tritiated a number of tripeptides, amongst other compounds. Essentially the same system was used by Peng et al [31,32] to tritiate a number of steroids. The apparatus was relatively simple to construct and the MDA method was seen to be superior to the other radiation-induced methods of labeling, requiring a short reaction time and using a small amount of tritium gas.…”