The trimethoprim-PEG3-amine (TMP-PEG3-amine) can be conjugated to various probes to make trimethoprim-based chemical tag (TMP-tag). The TMP-tag is based on the high affinity (KD ~ 1nM) binding of TMP to the E.coli dihydrofolate reductase (eDHFR). The target protein, fused to eDHFR via standard molecular cloning technology, is labeled by the TMP-probe in a non-covalent manner. The low affinity of TMP with mammalian DHFR (KD > 1µM) ensures minimal background. The TMP-tag has been demonstrated to enable protein visualization and manipulation both inside and on surface of mammalian cells.[1-4]
The TMP-PEG-amine can be used in combination with our Mix-n-Stain small ligand labeling kit to generate fluorescent chemical tags without purification for cell surface or intracellular staining.