Fig. 1.

LAMP mechanism, BART detection and variation between replicates at low copy number. (A) The LAMP and displacement primers invade double stranded DNA to initiate amplification with a displacement polymerase. (B) Looped structures are formed which are elongated with further LAMP primers and the addition of Loop primers (C). The pyrophosphate by-product of DNA amplification is converted into ATP which is utilised by a thermostable luciferase to produce detectable bioluminescence in the BART reaction (D). For the positive sample in blue, the light increases until the inhibition of luciferase by high concentrations of pyrophosphate. The negative sample in red maintains a background level of bioluminescence. The time-to-peak is directly proportional to the original DNA concentration of the positive sample. (E) A ten-fold dilution series from 10⁶ to 1 copy per reaction (pink 10⁶ copies, purple 10⁵, dark blue 10⁴, green 10³, light blue 100, orange 10, grey 1, red for no template control) shows the linear relationship between average time-to-peak and log template concentration between 10⁶ and 10³ (F). Lower copy numbers show increased variation between replicates. Below 10 copies the amplification frequency reduces from 100 percent (G).