The Polymerase Chain Reaction (PCR) is a powerful and sensitive technique for DNA amplification (1). Taq DNA Polymerase is an enzyme widely used in PCR (2). The following guidelines are provided to ensure successful PCR using New England Biolabs' OneTaq 2X Master Mix with GC Buffer. These guidelines cover routine PCR. Specialized applications may require further optimization.
We recommend assembling all reaction components on ice and quickly transferring the reactions to a thermocycler preheated to the denaturation temperature (94°C).
*For extremely difficult or high GC amplicons, the addition of 0–20% OneTaq High GC Enhancer may improve amplification.
||25 μl reaction
||50 μl reaction
|10 µM Forward Primer
|10 µM Reverse Primer
||< 1,000 ng
|OneTaq 2X Master
Mix with GCBuffer
|OneTaq High GC
||to 25 µl
||to 50 µl
||< 1,000 ng
Notes: Gently mix the reaction. Collect all liquid to the bottom of the tube by a quick spin if necessary. Overlay the sample with mineral oil if using a PCR machine without a heated lid.
Transfer PCR tubes to a PCR machine and begin thermocycling:
Thermocycling conditions for a routine PCR:
94°C 30 seconds
94°C 15-30 seconds
45–68°C 15-60 seconds
68°C 1 minute per kb
68°C 5 minutes
- General Guidelines:
Use of high quality, purified DNA templates greatly enhances the success of PCR. Recommended amounts of DNA template for a 50 µl reaction are as follows:
||1 ng–1 µg
|plasmid or viral
||1 pg–1 ng
Oligonucleotide primers are generally 20–40 nucleotides in length and ideally have a GC content of 40–60%. Computer programs such as Primer3 can be used to design or analyze primers. The final concentration of each primer in a PCR may be 0.05–1 µM, typically 0.2 µM.
- Mg++ and Additives:
Mg++ concentration of 1.5–2.0 mM is optimal for most PCR products generated with OneTaq DNA Polymerase. The final Mg++ concentration in 1X OneTaq Master Mix with GC Buffer is 2 mM. This supports satisfactory amplification of most amplicons. However, Mg++ can be further optimized in 0.2 mM increments using MgSO4 (NEB# B1003) . Amplification of extremely difficult targets may be improved by the addition of 10–20% OneTaq High GC Enhancer (included).
An initial denaturation of 30 seconds at 94°C is sufficient to amplify most targets from pure DNA templates. For difficult templates, a longer denaturation of 2–4 minutes at 94°C is recommended prior to PCR cycling to fully denature the template. With colony PCR, an initial 2–5 minute denaturation at 94°C is recommended to lyse cells.
During thermocycling a 15–30 second denaturation at 94°C is recommended.
The annealing step is typically 15–60 seconds. Annealing temperature is based on the Tm of the primer pair and is typically 45–68°C. Annealing temperatures can be optimized by doing a temperature gradient PCR starting 5°C below the calculated Tm. The NEB Tm Calculator is recommended for calculation of an appropriate annealing temperature.
The recommended extension temperature is 68°C. Extension times are generally 1 minute per kb. A final extension of 5 minutes at 68°C is recommended.
- Cycle Number:
Generally, 25–35 cycles yield sufficient product. Up to 45 cycles may be required to detect low copy number targets.
- 2-step PCR:
When primers with annealing temperatures of 68°C or above are used, a 2-step thermocycling protocol (combining annealing and extension into one step) is possible.
- PCR Product:
The majority of the PCR products generated using OneTaq DNA Polymerase contain dA overhangs at the 3´ end; therefore the PCR products can be ligated to dT/dU-overhang vectors.
1. Saiki R.K. et al. (1985). Science. 230, 1350-1354.
2. Powell, L.M. et al. (1987). Cell. 50, 831-840.