PCR additives Betaine, DMSO and formamide reduces the Tm and the complex secondary structure thus the duplex stability. Tetramethyl ammonium chloride
(TMAC) actually increases the specificity of hybridization and increases the Tm. The use of TMAC is recommended in PCR conditions using degenerate primers.
These PCR additives and enhancing agents have been used to increase the yield, specificity and
consistency of PCR reactions. These additives may have beneficial effects on some amplification and
it is impossible to predict which agents will be useful in a particular context and therefore they must be empirically tested for each combination of template and primers.
DMSO (dimethyl sulfoxide) reduce secondary
structure and is particularly useful for GC
rich templates. DMSO at 2-10% may be necessary for
amplification of some templates, however
10% DMSO can reduce Taq polymerase
activity by up to 50% so it should not be used