Development of Trimethoprim Chemical Tags for Single Molecule Imaging in Live Cells

By tagging biomolecules with bright and photostable fluorophores, chemical tags enable single molecule (SM) detection and imaging for the study of biological mechanism. One of these tags. the trimethoprim chemical tag (TMP-tag), labels biomolecules using the high affinity interaction between E.coli dihydrofolate reductase and fluorescent derivatives of the antibiotic trimethoprim. The TMP-tag is one of the few chemical tags that has enabled live cell SM imaging. In this work, I present the development of the TMP-tag as a versatile tool for SM imaging. First, I establish that the TMP-tag is a robust tool for labeling proteins with organic fluorophores that enable SM detection and imaging. I then examine the properties of novel organic fluorophores that expand the palette of dyes that can be used with SM imaging. I also investigate fluorescent nanodiamonds for expanded imaging and sensing capabilities in live cells using the TMP-tag. Finally, I explore applications of the TMP-tag to label and image ion channels for the identification of pharmacological chaperones as therapeutics for protein mistrafficking diseases. Together, these studies highlight the versatility of the TMP-tag, furthering our ability to study biomolecules under challenging imaging and biological conditions.