I'm planning an experiment to conjugate two biomolecules. Molecule A contains DBCO and molecule B a reactive azide which will be conjugated via click-chemistry. Molecule B is present in excess, here I want to quench the free azides to prevent a subsequent reaction with the reactive azide.

I have already read that the azide can be quenched with nitrous acid, but there is a protein attached to molecule A that cannot withstand such pH values.

Is there a milder way to quench the reactive azide?

Thank you

Tobi