The Construction Of Colorimetric DNA Logic Gates Based On G-quadreplex

The combination of chemical and molecular technologies to emulate silicon-based processing has arisen as a fascinating area of research in the scientific community. This has stimulated the development of molecular-scale logic gates that can parallel the Boolean functions representing the fundamental basis of modern computing. In this regard, the specially diversity of nucleic acid structures and functions can be potentially harnessed to construct logic operations for molecular computers. From the perspective, we engaged in the research and exploration of the establishing of DNA logic gates well as the application. As reflected in the following two aspects:1. A G-rich DNA is firstly blocked by the triplex-based molecular beacon(tMB). Upon hybridization with single-stranded DNA inputs, triplex-helix molecular switch occurs, and the released product strand self-assembles into the hemin/G-quadruplex-HRP-mimicking DNAzyme in the presence of hemin. Hemin/G-quadruplex biocatalyzes biocatalyzes the oxidation of TMB by H2O2, resulting in a colorimetric signal for the different logic gates. Based on this principle, a series of logic gates(OR, XOR, INHIBIT, AND) have been developed by using single-stranted DNA as inputs and colored product as output. Moreover, a multilevel circuit(MC) that enforces an overall OR Boolean behavior is developed by connecting the AND and XOR logic gates. The logic output signals can be recognized by naked eyes, thus providing a flexible, secure, economic, and simple method for designing a complex DNA-based logic device.2. We developed a colorimetric method to construct DNA logic gates based on the ion-modulated exonuclease III(Exo III) activity. Their simplicity and cost-effective design is the most apparent feature for the logic gates developed in this effort. Double-stranded(ds) DNA template with mismatched base pairs(T-T or C-C) can not be digested by the Exo III. Subsequently, it forms a double stranded template with a blunt end at the 3′ termini with the help of T-Hg2+-T or C-Ag+-T base pairs in the presence of Hg2+ and Ag+ ions. Therefore, the Exo III will digest dsDNA resulting that single-stranded(ss) DNA can be released. The released ssDNA can hybridize to signal reproter DNA(two G-rich DNA strands), self-assembling into the hemin/G-quadruplex that biocatalyzes the oxidation of TMB by H2O2, resulting in a colorimetric signal. Based on this principle, we constructed a series of logic gates(OR, AND, INHIBIT, XOR) by using Hg2+ and Ag+ ions as inputs and the colorimetric signal as output. In the other case, the released ssDNA can hybridize to the other signal reproter DNA(self-assembled split G-quadruplex structure), leading to the disassembly of the split G-quadruplex, resulting that hemin/G-quadruplex can not be formed and the colorimetric signal can not be produced. Based on this mechnism, we employed Hg2+ and Ag+ ions as inputs and colorimetric signal as output to construct NOR, NAND, IMPLICATION and XNOR logic gates. Besides, this method also implements the logic detection for heavy metal ions(Hg2+ and Ag+) in the OR logic gate, demonstrating that it has a good application prospect.