Figure 1.

General schematic of the direct restriction assay (DRA). (A) A molecular marker/label is conjugated to an oligonucleotide probe that is specific for a target gene of interest and immobilized on a solid surface through biotin-SA binding. (B) Target DNA (an oligonucleotide or denatured dsDNA) is hybridized to the immobilized probe. (C) A restriction enzyme recognizes and cleaves the target–probe dsDNA hybrid, resulting in the release of the molecular marker into the reaction solution. (D) The reaction solution is transferred into a new well to quantify the molecular marker. For each target DNA molecule, one molecular marker is released, resulting in linear dependence between the assay signal and the target DNA concentration.