The TOPO™ XL PCR Cloning Kit combines TOPO™ cloning, Zero Background™ technology, and a unique gel purification step to enhance cloning of PCR products from 3 to 10 kb. Convenient features of the pCR™-XL-TOPO™ vector include:
- ccdB gene eliminates background of non-recombinant clones
- Kanamycin and Zeocin™ resistance genes for your choice of selection in E. coli
- T7 sequence for in vitro RNA transcription and sequencing
- Selection of competent cells for high speed, electroporation, or routine cloning
|Unique gel purification step improves results
Long PCR often yields multiple products, making gel purification necessary prior to cloning. However, gel purification requires exposure to ethidium bromide and UV light, which can nick and damage DNA. To protect against nicking, the TOPO XL PCR Cloning Kit uses crystal violet to enable visualization of DNA bands in an agarose gel under ambient light. This eliminates the need for ethidium bromide and UV light exposure, ensuring safe gel purification. Crystal violet staining results in significantly more colonies and a greater percentage of recombinants than using ethidium bromide and UV light (Table 1).
The pCR-XL-TOPO vector
Table 1. Crystal violet enhances TOPO cloning of large fragments.
A 7 kb ampicilin resistance gene sequence was PCR-amplified, and PCR products were loaded onto one gel with crystal violet and another gel stained with ethidium bromide. PCR products were gel purified and cloned into the pCR-XL-TOPO vector. The number of recombinants was determined by plating 125 of each transformation on LB plates containing either kanamycin or kanamycin and ampicillin.
|Total colonies (Kan2)
|Colonies w/Insert (Kan2-Amp2)