Sweet enhancers of polymerase chain reaction.

Although faster and powerful, polymerase chain reaction (PCR) often failed to amplify targets efficiently. Numerous PCR enhancers have been used to increase the amplification efficiency of difficult DNA targets. However, there is no systematic comparison of their effects in normal and difficult PCR conditions. In this paper, we have selected nine different PCR enhancers that can promote the PCR amplification efficiency. We have compared their effect in Taq DNA polymerase thermostability, inhibitor resistance, and amplification of various DNA targets. Although the PCR enhancers more or less reduced the amplification efficiency of DNA fragments with moderate GC-content, they were able to improve the amplification efficiency and specificity of GC-rich fragments. Betaine outperformed the other enhancers in amplification of GC-rich DNA fragments, thermostabilizing Taq DNA polymerase, and inhibitor tolerance. Sucrose and trehalose showed similar effect in thermostabilizing Taq DNA polymerase and inhibitor tolerance, while they showed mildest inhibitory effect on normal PCR. For GC-rich region-containing long DNA fragment amplification, 1 M betaine, 0.5 M betaine + 0.2 M sucrose, or 1 M betaine + 0.1 M sucrose can be used to effectively promote the amplification, while keep their negative effect in amplification of normal fragment to a minimal level.