Fig. 1. Two step labelling scheme. In the first step, the DNA is transalkylated using a DNA MTase and an AdoMet analogue which results in the DNA molecules carrying functional groups at known loci. Amine (R1) functionalized DNA can be coupled to a fluorophore using NHS ester chemistry, whereas for azide (R2) functionalized DNA this can be done using CuAAC and strain-promoted azide–alkyne cycloaddition (SPAAC) reactions.
