Methotrexate Conjugates: A Molecular In Vivo Protein Tag


  • We are grateful for financial support for this work from Acidophil, LLC and intellectual support from Sydney Brenner. V.W.C. is a recipient of a Sloan Foundation Fellowship.


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The labeling of proteins in living cells with fluorescent substituents is critical to the study of cell biology. A ligand–receptor approach based on the interaction between dihydrofolate reductase (DHFR) and methotrexate (Mtx) serves as a general method for labeling proteins with fluorescent or otherwise functional small molecules in vivo (see figure).