A full-adder based on reconfigurable DNA-hairpin inputs and DNAzyme computing modules

In nature, post-transcriptional alternative splicing processes expand the proteome biodiversity providing means to synthesize various protein isoforms. We describe the input-guided assembly of a DNAzyme-based full-adder computing system, which mimics functions of the natural processes by increasing the diversity of logic elements by the reconfiguration of the inputs. The full-adder comprises the simultaneous operation of three inputs that yield two different output signals, acting as sum and carry bits. The DNAzyme-based full-adder system consists of a library of Mg2+-dependent DNAzyme subunits and their substrates that are modified by two different fluorophore/quencher pairs that encode the sum and carry outputs. The input-guided assembly of DNAzyme subunits, formed by three inputs composed of nucleic acid hairpin structures, leads to computing modules that yield the sum and carry outputs of the full-adder. In the presence of a single input the DNAzyme computing module yields the sum fluorescence output. In the presence of two of the inputs, the reconfiguration of the input structures proceeds, leading to an input-guided computing module that yields the carry fluorescence output. By introducing all the three inputs the sequential inter-input hybridization leads to the reconfiguration of the inputs into polymer wires. These include binding sites for two types of DNAzyme and their substrates leading to the carry and sum fluorescence outputs. The advantages of the simultaneous three-input operation of the full-adder and the possibilities to implement DNAzyme-based computing modules for cascading full-adders are discussed.