Fig. 2
From: Tritium labeling of antisense oligonucleotides via different conjugation agents
Overview of different approaches applied in this study to introduce tritium labels to oligonucleotides by conjugation. Introducing propionyl using (1) N-succinimidyl propionate (NSP) to the 3′-end via an aminopropyl glycerol-based linker (Route A), and via Michael addition of (2) N-ethylmaleimide (NEM), (3) N-methylmaleimide (NMM), or (4) N-[3H]ethylmaleimide ([3H]NEM) to a C6-thiol-linker at the 3′-end (Route B)