Fluorescent SAM analogues for methyltransferase based DNA labeling.

In this work, the preparation of new S-adenosyl-l-methionine (SAM) analogues for sequence specific DNA labeling is evaluated. These non-natural analogues, comprising cysteine rather than the natural homolog, were obtained in near quantitative conversions from readily available starting materials without relying on using an excess amount of labor intensive molecules. The synthetic strategy was used to generate fluorescent cofactors, with colours spanning the whole visible spectrum, and their applicability in methyltransferase based optical mapping is shown.