Analog versus digital detection of molecules

<p><img alt="images/Pasted image 20221230113844.png" class="wikiimage" src="/images/pasted image 20221230113844.png" /></p> <p>When detecting concentration, for example, an analog measurement will yield an intensity proportional to the amount of analytes labelled. For this type of measurements to work, one needs to <em>integrate</em> over time. This is how a <a class="wikilink" href="/elisa_test/">Elisa test</a> work, or how <a class="wikilink" href="/plate_readers/">plate readers</a> operate. </p> <p>On the other hand, <a class="wikilink" href="/single-molecule/">single-molecule</a> experiments are digital in nature[<a class="litnote tooltip" href="/literature/@walt2013">@walt2013<span class="tooltiptext">Optical Methods for Single Molecule Detection and Analysis</span></a>], there either is, or there isn't a molecule to be detected. <a class="wikilink" href="/digital_pcr/">Digital pcr</a>, and <a class="wikilink" href="/simoa/">Simoa</a> are two types of measurement that exploit a form of <em>amplification</em> (either replication of a nucleotide strand, or using the non-linearity of the fluorescence signal) to determine the number of times a molecule is present versus the number of times it is not, hence generating a concentration measurement out of a digital system.</p>