Nucleic acid labeling and detection products are used to add tags or labels to nucleic acids to enable detection or purification. The tagged nucleic acids are referred to as 'probes.'

Nucleotide labeling may include radioactive phosphates, biotin, fluorophores, and various enzymes. Bioconjugation methods that produce nucleic acid probes can also be adapted to attach them to other molecules (for targeted delivery) and surfaces (to facilitate immobilization).

Although nucleic acid probes can be labeled during synthesis, custom oligonucleotide probes can be expensive so many researchers choose to label their own.

Quick and efficient benchtop oligonucleotide labeling can be performed for making smaller probe amounts or when multiple probes with the same label are needed. Enzymatic methods are affordable for small-scale probe generation; chemical methods are more suited to larger scale reactions.

Probes can be labeled at either end of the oligonucleotide or randomly incorporated throughout the sequence. The choice of method depends on the degree of labeling required and whether changes will prevent theexpected interactions. Nucleic acid hybridization reactions can benefit from random label incorporation; protein interactions may require end-labelling.

Summary of Methods

Enzymatic

• TdT: ssDNA
• T4 RNA Ligase: ssDNA, RNA
• T4 PNK: ssDNA, RNA
• DNA Polymerase: DNA, RNA
• RNA Polymerase: RNA

Chemical

• Periodate: RNA
• EDC: DNA, RNA
• Nonspecific crosslinkers: DNA, RNA

Detection methods are biotin-based, chemiluminescent, fluorescent, radioactive, or the combination of several techniques. Tests may include nucleic acid tests for pathogen detection and fluorescent in situ hybridization (FISH) for specific DNA sequences in chromosomes.