In DNA mutagenesis, a fixed sequence is altered to produce a new sequence or library of sequences, allowing researchers to expand the sequence space they are surveying. Several commercial kits exist, particularly to conduct site directed mutagenesis, which can be achieved using polymerase chain reaction (PCR) primers containing the desired change. In addition, oligos containing randomized bases or specific mixtures of bases can be used to generate a library of sequences. TriLink specializes in randomizing oligonucleotides so that they contain specific ratios of each base. Systematic evolution of ligands by exponential enrichment (SELEX) starts with a randomized library (usually 20-60 nucleotides) flanked by fixed sequences. The RNA library is then mixed with a target ligand, and a partitioning step separates and retains bound RNAs. The narrowed library that binds the ligand is then reverse transcribed, PCR amplified, and transcribed. Further rounds of selection yield a library that binds progressively tighter to the ligand, and when sufficient affinity has been achieved, individual library members are cloned. TriLink can produce custom randomized libraries for your SELEX experiments.
A longer sequence can also be randomized using mutagenic PCR. In mutagenic PCR, nucleoside triphosphates (NTPs), which during amplification can be read as several different bases, are used in the PCR reaction. The resulting PCR product contains randomized bases in proportion to the concentration of the mutagenic NTPs. TriLink offers several mutagenic NTPs individually, as well as a mutagenesis dNTP set.