Resolution:
## Figure 1.
Sigmoidal modeling of PCR amplification reveals symmetry between amplicon accumulation
and loss in amplification efficiency. (A) Plots of the sigmoid functions describing amplicon accumulation (equation 1, solid
line) and cycle efficiency (equation 2, dashed line) illustrate a symmetrical relationship,
where C_{1/2 }defines the fractional cycle when both reach half of their respective maxima. F_{0 }is target quantity expressed in fluorescence units, E_{max }is the maximal amplification efficiency and F_{max }is the maximal reaction fluorescence. (B) Plotting cycle efficiency against reaction fluorescence produces a line, predicting
that the progressive loss in cycle efficiency is linearly coupled to amplicon accumulation.
This generates a linear representation of PCR amplification (referred to as the "LRE
plot"), where the Y intercept defines the maximal amplification efficiency (E_{max}) when F_{C }= 0 and the X intercept defines the end-point or plateau phase (F_{max}) when E_{C }= 0, with the slope defining the rate of loss in cycle efficiency (ΔE) in relation
to amplicon DNA quantity as reflected by reaction fluorescence.
Rutledge and Stewart |