'Click' bioconjugation of a well-defined synthetic polymer and a protein transduction domain

The copper-catalyzed 1,3-dipolar 'click' cycloaddition of azides and alkynes was studied to link a model synthetic polymer to a sequence-defined protein transduction domain (PTD). The bromine chain-ends of a well-defined polystyrene ( PS) sample synthesized by atom transfer radical polymerization (M-n 2200 g mol(-1), M-w/M-n 1.21) were first transformed into azide functions by substitution with sodium azide, and subsequently reacted with an alkyne-functionalized PTD (i.e., the oligopeptide sequence GGYGRKKRRQRRRG, also known as the TAT peptide). The click bioconjugation proceeded successfully at room temperature, thus affording the targeted PS-b-GGYGRKKRRQRRRG bioconjugate in high yields. However, a slight molar excess of polystyrene was required for optimal coupling.