Psoralen TMP Azide is an excellent building block for developing site-specific nucleic acid probes via the well-known click chemistry, i.e., Copper-Catalyzed Alkyne–Azide Cycloaddition (CuAAC). It can be readily conjugated to azido-containing biomolecules (such as alkynyl-modified antibodies, peptide alkynes and alkynyl-modified oligos). Psoralens and their derivatives (such as 8-TMP and 4,5’,8-TMP) are well known to have unique crosslinking features to DNA. Psoralen TMP Azide is an alkynyl-reactive TMP derivative. It is an excellent building block for preparing TMP-labeled oligos from an alkynyl-modified oligo. The TMP-conjugated oligonucleotides can be used for sequence-specific crosslinking with a target DNA, thus enabling the application of psoralen-conjugated molecules in gene transcription inhibition, gene knockout, and other genomic applications.