The effect of pyridinecarboxaldehyde functionalisation on reactivity and N-terminal protein modification

The site-selective modification of protein N-termini represents a powerful strategy for producing homogeneous bioconjugates. 2-Pyridinecarboxaldehydes have emerged as a leading reagent class in this area, but conjugation suffers from relatively slow rates and a degree of reversibility. In this work, we therefore studied the effects of pyridinecarboxaldehyde functionalisation on N-terminal modification, providing insight into the factors governing relative contributions from competing reaction pathways and design criteria for second generation reagents for protein labelling. Importantly, this insight allowed us to identify several candidate reagents which provide both accelerated and more stable protein labelling, enabling further applications of this powerful technology.