With the genomics age in full swing, researchers are demanding dependable ways of detecting and analyzing genes and mRNA found in microarrays, cells, and tissues. The industry is answering that call with a wide assortment of DNA labeling kits to suit the needs of practically every type of experiment.
DNA labeling kits first came into being when nick translation was developed, which allowed researchers to produce radioactive probes in vitro by generating free 3’-hydroxyl ends, also called “nicks,” within a double-stranded DNA template. DNA polymerase I then incorporates radioactively labeled nucleotides into the growing probe. But because polymerases prefer to incorporate non-labeled nucleotides, the resulting probe could only offer a specific activity correlating with about 40 percent incorporation of labeled nucleotides. These days, the few remaining companies offering labeling kits based on nick translation claim that they’ve increased the yield to 60 percent.
In an attempt to improve the incorporation of labeled nucleotides, Andrew Feinberg and Bert Vogelstein developed a method they called random priming in 1983. Their technique called for the use of random oligonucleotides to prime DNA synthesis along a strand that has been denatured. While this method generated probes that were more heavily labeled, it still left researchers in need of better probes to perform more sophisticated experiments—which meant finding labels that could not only provide more sensitive detection, but that were also more stable and convenient, cheaper, and would allow for faster processing.
The problem now is choosing from the myriad of labeling kits available. Gone are the days when radioactive isotopes were a staple in a lab’s supply cabinet. These days, researchers can save themselves the cost and risk of using radioactivity by turning to fluorescence, bioluminescence, enzymes (e.g. horseradish peroxidase), haptens, and inorganic nanoparticles.
The newer kits provide unique solutions to attaching labels to nuclei acids, which—unlike proteins—don’t have as many reactive groups that can be chemically modified. Many of these kits rely on secondary detection technology, by which a linker molecule, such as platinum or psoralen, intercalates into the DNA template. Haptens (e.g. dinitrophenol or digoxigenin) can then be attached to the linker molecule and used for detection. Using fluorescein as a label is very popular because it doesn’t require a linker molecule and has a faster labeling process. Newer fluorescent probes now have sensitivity levels comparable to those of radioisotopes, but with low background noise.
Looking for a DNA labeling kit? Take a look at the choices below. From 3’ to 5’, single-stranded to double-stranded, you won’t go away disappointed. The market offers a diverse selection of kits to fulfill a multitude of specifications.
The SuperScript™ Indirect cDNA Labeling System is an array labeling kit based on proven methods of indirect cDNA labeling. The optimized system provides SuperScript™ III RT for generation high cDNA yields, a proprietary nucleotide mixture to increase signal intensity, and a convenient kit format that saves you valuable time. You don't have to source and optimize your reagents and you won't have to adjust to any new methods.
CyScribe™ First-Strand cDNA Labelling Kit uses new CyScript™ reverse transcriptase to synthesize Cy3- and Cy5-labelled first-strand cDNAs for use in microarray applications. From 0.1 to 1 µg of mRNA can be labelled in a standard 20 µl reaction in less than 3 hours. The CyScribe™ kit has been designed to offer the flexibility of performing labelling reactions with either Cy3- and Cy5-labelled dCTP or Cy3- and Cy5-labelled dUTP. The labelling reactions can be primed with anchored oligo(dT), which provides a convenient means for directing the synthesis of cDNA from the 3’-end of the mRNA, and with random nonamers, which will prime cDNA synthesis along the length of transcripts.
