Effect of Buffer Conditions and Organic Cosolvents on the Rate of Strain-Promoted Azide–Alkyne Cycloaddition

We investigate the effect of buffer identity, ionic strength, pH, and organic cosolvents on the rate of strain-promoted azide–alkyne cycloaddition with the widely used DIBAC cyclooctyne. The rate of reaction between DIBAC and a hydrophilic azide is highly tolerant to changes in buffer conditions but is impacted by organic cosolvents. Thus, bioconjugation reactions using DIBAC can be carried out in the buffer that is most compatible with the biomolecules being labeled, but the use of organic cosolvents should be carefully considered.