Logic gates and antisense DNA devices operating on a translator nucleic Acid scaffold

Advances in the application of logic gates in nanozymes

Nanozymes are a class of nanomaterials with biocatalytic function and enzyme-like activity, whose advantages include high stability, low cost, and mass production. They can catalyze the substrates of natural enzymes based on specific nanostructures and serve as substitutes for natural enzymes. Their applied research involves a wide range of fields such as biomedicine, environmental governance, agriculture, and food. Molecular logic gates are a new cross-disciplinary discipline, which can simulate the function of silicon circuits on a molecular scale, perform single or multiple input logic operations, and generate logic outputs. A molecular logic gate is a binary operation that converts an input signal into an output signal according to the rules of Boolean logic, generating two signals, a high level, and a low level. The high and low levels represent the "true" and "false" values of the logic gates, and their outputs correspond to "l" and "0" of the molecular logic gates, respectively. The combination of nanozymes and logic gates is a novel and attractive research direction, and the cross-application of the two brings new opportunities and ideas for various fields, such as the construction of efficient biocomputers, intelligent drug delivery systems, and the precise diagnosis of diseases. This review describes the application of logic gates based on nanozymes, which is expected to provide a certain theoretical foundation for researchers' subsequent studies.

Construction and Application of DNAzyme-based Nanodevices

The development of stimuli-responsive nanodevices with high efficiency and specificity is very important in biosensing, drug delivery, and so on. DNAzymes are a class of DNA molecules with the specific catalytic activity. Owing to their unique catalytic activity and easy design and synthesis, the construction and application of DNAzymes-based nanodevices have attracted much attention in recent years. In this review, the classification and properties of DNAzyme are first introduced. The construction of several common kinds of DNAzyme-based nanodevices, such as DNA motors, signal amplifiers, and logic gates, is then systematically summarized. We also introduce the application of DNAzyme-based nanodevices in sensing and therapeutic fields. In addition, current limitations and future directions are discussed.

Catalyst-Based Biomolecular Logic Gates

Regulatory processes in biology can be re-conceptualized in terms of logic gates, analogous to those in computer science. Frequently, biological systems need to respond to multiple, sometimes conflicting, inputs to provide the correct output. The language of logic gates can then be used to model complex signal transduction and metabolic processes. Advances in synthetic biology in turn can be used to construct new logic gates, which find a variety of biotechnology applications including in the production of high value chemicals, biosensing, and drug delivery. In this review, we focus on advances in the construction of logic gates that take advantage of biological catalysts, including both protein-based and nucleic acid-based enzymes. These catalyst-based biomolecular logic gates can read a variety of molecular inputs and provide chemical, optical, and electrical outputs, allowing them to interface with other types of biomolecular logic gates or even extend to inorganic systems. Continued advances in molecular modeling and engineering will facilitate the construction of new logic gates, further expanding the utility of biomolecular computing.

Constructing DNA logic circuits based on the toehold preemption mechanism

Strand displacement technology and ribozyme digestion technology have enriched the intelligent toolbox of molecular computing and provided more methods for the construction of DNA logic circuits. In recent years, DNA logic circuits have developed rapidly, and their scalability and accuracy in molecular computing and information processing have been fully demonstrated. However, existing DNA logic circuits still have some problems such as high complexity of DNA strands (number of DNA strands) hindering the expansion of practical computing tasks. In view of the above problems, we presented a toehold preemption mechanism and applied it to construct DNA logic circuits using E6-type DNAzymes, such as half adder circuit, half subtractor circuit, and 4-bit square root logic circuit. Different from the dual-track logic expressions, all the signals in the circuits of this study were monorail which substantially reduced the number of DNA strands in the DNA logic circuits. The presented preemption mechanism provides a way to simplify the implementation of large and complex DNA integrated circuits.

Metal-Organic Framework Nanoparticles Power DNAzyme Logic Circuits for Aberrant MicroRNA Imaging

At the molecular level, a large number of studies exist on the use of dynamic DNA molecular circuits for disease diagnosis and biomedicine. However, how to design programmable molecular circuit devices to autonomously and accurately diagnose multiple low-abundance biomolecules in complex cellular environments remains a challenge. Here, we constructed DNAzyme logic circuits for the analysis and imaging of multiple microRNAs in living cells using Cu/ZIF-8 NPs as a nanocarrier of the logic gate modules and the Cu²⁺ cofactor of the Cu²⁺-dependent DNAzyme. The logic gate modules of the logic operation system were adsorbed on the surface of Cu/ZIF-8 NPs via electrostatic interaction. After internalization, pH-responsive Cu/ZIF-8 NPs could efficiently release the logic gate modules and Cu²⁺, which allowed us to realize multiple logic computations initiated by endogenous miRNA, including one YES logic gate and two binary logic gates (OR and AND) in different living cells. Cu²⁺-DNAzyme logic circuits could quickly respond to multiple endogenous miRNAs in the complex cell environment, which also provided a new research method for the application of DNA biocomputing circuits in living cells.

Development of Synthetic DNA Circuit and Networks for Molecular Information Processing

Deoxyribonucleic acid (DNA), a genetic material, encodes all living information and living characteristics, e.g., in cell, DNA signaling circuits control the transcription activities of specific genes. In recent years, various DNA circuits have been developed to implement a wide range of signaling and for regulating gene network functions. In particular, a synthetic DNA circuit, with a programmable design and easy construction, has become a crucial method through which to simulate and regulate DNA signaling networks. Importantly, the construction of a hierarchical DNA circuit provides a useful tool for regulating gene networks and for processing molecular information. Moreover, via their robust and modular properties, DNA circuits can amplify weak signals and establish programmable cascade systems, which are particularly suitable for the applications of biosensing and detecting. Furthermore, a biological enzyme can also be used to provide diverse circuit regulation elements. Currently, studies regarding the mechanisms and applications of synthetic DNA circuit are important for the establishment of more advanced artificial gene regulation systems and intelligent molecular sensing tools. We therefore summarize recent relevant research progress, contributing to the development of nanotechnology-based synthetic DNA circuits. By summarizing the current highlights and the development of synthetic DNA circuits, this paper provides additional insights for future DNA circuit development and provides a foundation for the construction of more advanced DNA circuits.

Logic Gates Based on DNA Aptamers

DNA bio-computing is an emerging trend in modern science that is based on interactions among biomolecules. Special types of DNAs are aptamers that are capable of selectively forming complexes with target compounds. This review is devoted to a discussion of logic gates based on aptamers for the purposes of medicine and analytical chemistry. The review considers different approaches to the creation of logic gates and identifies the general algorithms of their creation, as well as describes the methods of obtaining an output signal which can be divided into optical and electrochemical. Aptameric logic gates based on DNA origami and DNA nanorobots are also shown. The information presented in this article can be useful when creating new logic gates using existing aptamers and aptamers that will be selected in the future.

Rational design to control the trade-off between receptor affinity and cooperativity

Cooperativity enhances the responsiveness of biomolecular receptors to small changes in the concentration of their target ligand, albeit with a concomitant reduction in affinity. The binding midpoint of a two-site receptor with a Hill coefficient of 1.9, for example, must be at least 19 times higher than the dissociation constant of the higher affinity of its two binding sites. This trade-off can be overcome, however, by the extra binding energy provided by the addition of more binding sites, which can be used to achieve highly cooperative receptors that still retain high affinity. Exploring this experimentally, we have employed an "intrinsic disorder" mechanism to design two cooperative, three-binding-site receptors starting from a single-site-and thus noncooperative-doxorubicin-binding aptamer. The first receptor follows a binding energy landscape that partitions the energy provided by the additional binding event to favor affinity, achieving a Hill coefficient of 1.9 but affinity within a factor of 2 of the parent aptamer. The binding energy landscape of the second receptor, in contrast, partitions more of this energy toward cooperativity, achieving a Hill coefficient of 2.3, but at the cost of 4-fold poorer affinity than that of the parent aptamer. The switch between these two behaviors is driven primarily by the affinity of the receptors' second binding event, which serves as an allosteric "gatekeeper" defining the extent to which the system is weighted toward higher cooperativity or higher affinity.

Entropy-driven DNA logic circuits regulated by DNAzyme

The catalytic DNA circuits play a critical role in engineered biological systems and molecular information processing. Actually, some of the natural or synthetic DNA circuits were triggered by covalent modifications, where conformational changes were induced to facilitate complex DNA engineering functions and signal transmissions. However, most of the reported artificial catalytic DNA circuits were regulated by the toehold-mediated reaction. Therefore, it is significant to propose a strategy to regulate the catalytic DNA circuit not only by the toehold-mediated mechanism, but also by involving the conformational changes induced by the covalent modification. In this study, we developed the catalytic DNA logic circuits regulated by DNAzyme. Here, a regulation strategy based on the covalent modification was proposed to control the DNA circuit, combing two reaction mechanisms: DNAzyme digestion and entropy-driven strand displacement. The DNAzyme and DNA catalyst can participate into the reactions alternatively, thus realizing the cascading catalytic circuits. Using the DNAzyme regulation, a series of logic gates (YES, OR and AND) were constructed. In addition, a two-layer cascading circuit and a feedback self-catalysis circuit were also established. The proposed DNAzyme-regulated strategy shows great potentials as a reliable and feasible method for constructing more complex catalytic DNA circuits.

Fluorogenic RNA Aptamers: A Nano-platform for Fabrication of Simple and Combinatorial Logic Gates

RNA aptamers that bind non-fluorescent dyes and activate their fluorescence are highly sensitive, nonperturbing, and convenient probes in the field of synthetic biology. These RNA molecules, referred to as light-up aptamers, operate as molecular nanoswitches that alter folding and fluorescence function in response to ligand binding, which is important in biosensing and molecular computing. Herein, we demonstrate a conceptually new generation of smart RNA nano-devices based on malachite green (MG)-binding RNA aptamer, which fluorescence output controlled by addition of short DNA oligonucleotides inputs. Four types of RNA switches possessing AND, OR, NAND, and NOR Boolean logic functions were created in modular form, allowing MG dye binding affinity to be changed by altering 3D conformation of the RNA aptamer. It is essential to develop higher-level logic circuits for the production of multi-task nanodevices for data processing, typically requiring combinatorial logic gates. Therefore, we further designed and synthetized higher-level half adder logic circuit by “in parallel” integration of two logic gates XOR and AND within a single RNA nanoparticle. The design utilizes fluorescence emissions from two different RNA aptamers: MG-binding RNA aptamer (AND gate) and Broccoli RNA aptamer that binds DFHBI dye (XOR gate). All computationally designed RNA devices were synthesized and experimentally tested in vitro. The ability to design smart nanodevices based on RNA binding aptamers offers a new route to engineer “label-free” ligand-sensing regulatory circuits, nucleic acid detection systems, and gene control elements.

Materials learning from life: concepts for active, adaptive and autonomous molecular systems

A broad overview of functional aspects in biological and synthetic out-of-equilibrium systems.

Controlling G-quadruplex formation via lipid modification of oligonucleotide sequences

G-quadruplexes (G4) represent attractive supramolecular scaffolds.

Aptamer-Binding Directed DNA Origami Pattern for Logic Gates

In this study, an aptamer-substrate strategy is introduced to control programmable DNA origami pattern. Combined with DNA aptamer-substrate binding and DNAzyme-cutting, small DNA tiles were specifically controlled to fill into the predesigned DNA origami frame. Here, a set of DNA logic gates (OR, YES, and AND) are performed in response to the stimuli of adenosine triphosphate (ATP) and cocaine. The experimental results are confirmed by AFM imaging and time-dependent fluorescence changes, demonstrating that the geometric patterns are regulated in a controllable and programmable manner. Our approach provides a new platform for engineering programmable origami nanopatterns and constructing complex DNA nanodevices.

Multifunctional Graphene/DNA-Based Platform for the Construction of Enzyme-Free Ternary Logic Gates

In this work, we have successfully realized multivalued logic circuits including ternary INHIBIT and ternary OR logic gates in an enzyme-free condition by integration of graphene oxide and DNA for the first time. Compared to the binary logic gate with two states of "0" and "1", the multivalued logic gate contains three different states of "0", "1", and "2", which can increase the information content in a system and further improve the ability of information processing. Such types of multivalued logic operations provide a wider field of vision toward DNA-based algebra logical operations to make applications more accurate with complexity reduction and accelerate the development of advanced logic gates.

Integration of DNA and graphene oxide for the construction of various advanced logic circuits

Multiple advanced logic circuits including the full-adder, full-subtract and majority logic gate have been successfully realized on a DNA/GO platform for the first time. All the logic gates were implemented in an enzyme-free condition. The investigation provides a wider field of vision towards prototypical DNA-based algebra logical operations and promotes the development of advanced logic circuits.

An enzyme-free and resettable platform for the construction of advanced molecular logic devices based on magnetic beads and DNA

A series of multiple logic circuits based on magnetic beads and DNA are constructed to perform resettable nonarithmetic functions, including a digital comparator, 4-to-2 encoder and 2-to-3 decoder, 2-to-1 encoder and 1-to-2 decoder. The signal reporter is composed of a G-quadruplex/NMM complex and a AuNP-surface immobilized molecular beacon. It is the first time that the designed DNA-based nonarithmetic nanodevices can share the same DNA platform with a reset function, which has great potential application in information processing at the molecular level. Another novel feature of the designed system is that the developed nanodevices are operated on a simple DNA/magnetic bead platform and share a constant threshold setpoint without the assistance of any negative logic conversion. The reset function is realized by heating the output system and the magnetic separation of the computing modules. Due to the biocompatibility and design flexibility of DNA, these investigations may provide a new route towards the development of resettable advanced logic circuits in biological and biomedical fields.

Innovative Bimolecular-Based Advanced Logic Operations: A Prime Discriminator and An Odd Parity Checker

Herein, a novel logic operation of prime discriminator is first performed for the function of identifying the prime numbers from natural numbers less than 10. The prime discriminator logic operation is developed by DNA hybridizations and the conjugation of graphene oxide and single-stranded DNA as a reacting platform. On the basis of the similar reaction principle, an odd parity checker is also developed. The odd parity checker logic operation can identify the even numbers and odd numbers from natural numbers less than 10. Such advanced logic operations with digital recognition ability can provide a new field of vision toward prototypical DNA-based logic operations and promote the development of advanced logic circuits.

An enzyme-free and DNA-based Feynman gate for logically reversible operation

A logically reversible Feynman gate was successfully realized under enzyme-free conditions by integrating graphene oxide and DNA for the first time. The gate has a one-to-one mapping function to identify inputs from the corresponding outputs. This type of reversible logic gate may have great potential applications in information processing and biosensing systems.

Reconfigurable and resettable arithmetic logic units based on magnetic beads and DNA

Based on the characteristics of magnetic beads and DNA, a simple and universal platform was developed for the integration of multiple logic gates to achieve resettable half adder and half subtractor functions. The signal reporter was composed of a split G-quadruplex DNAzyme and AuNP-surface immobilized molecular beacon molecule. The novel feature of the designed system is that the inputs (split G-quadruplexes) can interact with hairpin-modified Au NPs linked to magnetic particles. Another novel feature is that the logic operations can be reset by heating the output system and by using the magnetic separation of the computing modules. Moreover, the developed half adder and half subtractor are realized on a simple DNA/magnetic bead platform in an enzyme-free system and share a constant threshold setpoint. Due to the diversity and design flexibility of DNA, these investigations may provide a new method for the development of resettable DNA-based arithmetic operations.

A general approach to the design of allosteric, transcription factor-regulated DNAzymes

Here we explore a general strategy for the rational design of nucleic acid catalysts that can be allosterically activated by specific nucleic-acid binding proteins. To demonstrate this we have combined a catalytic DNAzyme sequence and the consensus sequence recognized by specific transcription factors to create a construct exhibiting two low-energy conformations: a more stable conformation lacking catalytic activity and lacking the transcription factor binding site, and a less stable conformation that is both catalytically active and competent to bind the transcription factor. The presence of the target transcription factor pushes the equilibrium between these states towards the latter conformation, concomitantly activating catalysis. To demonstrate this we have designed and characterized two peroxidase-like DNAzymes whose activities are triggered upon binding either TATA binding protein or the microphthalmia-associated transcription factor. Our approach augments the current tool kit for the allosteric control of DNAzymes and ribozymes and, because transcription factors control many key biological functions, could have important clinical and diagnostic applications.

DNA-based machines

The base sequence in nucleic acids encodes substantial structural and functional information into the biopolymer. This encoded information provides the basis for the tailoring and assembly of DNA machines. A DNA machine is defined as a molecular device that exhibits the following fundamental features. (1) It performs a fuel-driven mechanical process that mimics macroscopic machines. (2) The mechanical process requires an energy input, "fuel." (3) The mechanical operation is accompanied by an energy consumption process that leads to "waste products." (4) The cyclic operation of the DNA devices, involves the use of "fuel" and "anti-fuel" ingredients. A variety of DNA-based machines are described, including the construction of "tweezers," "walkers," "robots," "cranes," "transporters," "springs," "gears," and interlocked cyclic DNA structures acting as reconfigurable catenanes, rotaxanes, and rotors. Different "fuels", such as nucleic acid strands, pH (H⁺/OH⁻), metal ions, and light, are used to trigger the mechanical functions of the DNA devices. The operation of the devices in solution and on surfaces is described, and a variety of optical, electrical, and photoelectrochemical methods to follow the operations of the DNA machines are presented. We further address the possible applications of DNA machines and the future perspectives of molecular DNA devices. These include the application of DNA machines as functional structures for the construction of logic gates and computing, for the programmed organization of metallic nanoparticle structures and the control of plasmonic properties, and for controlling chemical transformations by DNA machines. We further discuss the future applications of DNA machines for intracellular sensing, controlling intracellular metabolic pathways, and the use of the functional nanostructures for drug delivery and medical applications.

DNA-based visual majority logic gate with one-vote veto function

A molecular logic gate is a basic element and plays a key role in molecular computing. Herein, we have developed a label-free and enzyme-free three-input visual majority logic gate which is realized for the first time according to DNA hybridization only, without DNA replacement and enzyme catalysis. Furthermore, a one-vote veto function was integrated into the DNA-based majority logic gate, in which one input has priority over other inputs. The developed system can also implement multiple basic and cascade logic gates.

Versatile G-quadruplex-mediated strategies in label-free biosensors and logic systems

This review addresses how G-quadruplex (G4)-mediated biosensors convert the events of target recognition into a measurable physical signal. The application of label-free G4-strategies in the construction of logic systems is also discussed.

A smart DNA–gold nanoparticle probe for detecting single-base changes on the platform of a quartz crystal microbalance

A design of DNA–gold nanoparticle probe-fueled DNA strand displacements for detecting single-base changes on the platform of a quartz crystal microbalance with random sequences was developed.

G-quadruplex-based logic gates for HgII and AgI ions employing a luminescent iridium(iii) complex and extension of metal-mediated base pairs by polymerase

We report herein the synthesis of a series of cyclometallated iridium(iii) complexes as luminescent G-quadruplex-selective probes to construct AND, OR and INHIBIT logic gates for the detection of Hg^II and Ag^I ions.

Applications of synchrotron-based spectroscopic techniques in studying nucleic acids and nucleic acid-functionalized nanomaterials

In this review, we summarize recent progress in the application of synchrotron-based spectroscopic techniques for nucleic acid research that takes advantage of high-flux and high-brilliance electromagnetic radiation from synchrotron sources. The first section of the review focuses on the characterization of the structure and folding processes of nucleic acids using different types of synchrotron-based spectroscopies, such as X-ray absorption spectroscopy, X-ray emission spectroscopy, X-ray photoelectron spectroscopy, synchrotron radiation circular dichroism, X-ray footprinting and small-angle X-ray scattering. In the second section, the characterization of nucleic acid-based nanostructures, nucleic acid-functionalized nanomaterials and nucleic acid-lipid interactions using these spectroscopic techniques is summarized. Insights gained from these studies are described and future directions of this field are also discussed.

Construction of DNA logic gates utilizing a H+/Ag+ induced i-motif structure

A simple technology to construct diverse DNA logic gates (OR and INHIBIT) has been designed utilizing a H(+) and/or Ag(+) induced i-motif structure. The logic gates are easily controlled and also show a real time response towards inputs. The research provides a new insight for designing DNA logic gates using an i-motif DNA structure.

Label-free colorimetric protein assay and logic gates design based on the self-assembly of hemin-graphene hybrid nanosheet

Here we report a label-free colorimetric method for protein assay based on the intrinsic peroxidase-like catalytic activity of DNA-hemin-graphene (DNA-GH) composite. By using aptamers as protein recognition elements, protein-mediated aggregation of the DNA-GH composite leads to the decrease or increase of the colorimetric signal depending on the sandwich or competitive design strategy. Thrombin and PDGF-BB were chosen as model analytes and the detection limits (LOD) by this method were estimated to be 0.5 nM and 5 nM, respectively. Compared to traditional ELISA method for protein detection, this method possesses the advantages of high sensitivity, simplicity, and low cost. In addition, by designing different DNA-modified hemin-graphene (GH) constructs, using proteins as inputs, the "OR" and "INHIBIT" logic gates were built. This procedure does not require chemical modification on the aptamer probes or analytes and circumvents the limitation associated with the number of target binding sites. Given the attractive analytical characteristics and distinct advantages of DNA-GH composite, the universal approach can be widely applied for the detection of diverse proteins and for the design of versatile logic gates.

Toehold-mediated DNA logic gates based on host–guest DNA-GNPs

A simple, toehold-mediated two-way input DNA machine has been developed. Utilizing symmetric and asymmetric protector sequences, INH, XOR logic gates and a half-subtractor are designed based on this two-way structure.

Integration of graphene oxide and DNA as a universal platform for multiple arithmetic logic units

Multiple logic gates were integrated on a universal GO–DNA platform to implement both half adder and half subtractor functions.

G-quadruplexes as tools for synthetic biology

With the potential to engineer biological systems, synthetic biology is an emerging field that combines various disciplines of sciences. It encompasses combinations of DNA, RNA and protein modules for constructing desired systems and the "rewiring" of existing signalling networks. Despite recent advances, this field still lags behind in the artificial reconstruction of cellular processes, and thus demands new modules and switches to create "genetic circuits". The widely characterised noncanonical nucleic acid secondary structures, G-quadruplexes are promising candidates to be used as biological modules in synthetic biology. Structural plasticity and functional versatility are significant G-quadruplex traits for its integration into a biological system and for diverse applications in synthetic circuits.

Logical regulation of the enzyme-like activity of gold nanoparticles by using heavy metal ions

In this study we employed self-deposition and competitive or synergistic interactions between metal ions and gold nanoparticles (Au NPs) to develop OR, AND, INHIBIT, and XOR logic gates through regulation of the enzyme-like activity of Au NPs. In the presence of various metal ions (Ag(+), Bi(3+), Pb(2+), Pt(4+), and Hg(2+)), we found that Au NPs (13 nm) exhibited peroxidase-, oxidase-, or catalase-like activity. After Ag(+), Bi(3+), or Pb(2+) ions had been deposited on the Au NPs, the particles displayed strong peroxidase-like activity; on the other hand, they exhibited strong oxidase- and catalase-like activities after reactions with Ag(+)/Hg(2+) and Hg(2+)/Bi(3+) ions, respectively. The catalytic activities of these Au NPs arose mainly from the various oxidation states of the surface metal atoms/ions. Taking advantage of this behavior, we constructed multiplex logic operations-OR, AND, INHIBIT, and XOR logic gates-through regulation of the enzyme-like activity after the introduction of metal ions into the Au NP solution. When we deposited Hg(2+) and/or Bi(3+) ions onto the Au NPs, the catalase-like activities of the Au NPs were strongly enhanced (>100-fold). Therefore, we could construct an OR logic gate by using Hg(2+)/Bi(3+) as inputs and the catalase-like activity of the Au NPs as the output. Likewise, we constructed an AND logic gate by using Pt(4+) and Hg(2+) as inputs and the oxidase-like activity of the Au NPs as the output; the co-deposition of Pt and Hg atoms/ions on the Au NPs was responsible for this oxidase-like activity. Competition between Pb(2+) and Hg(2+) ions for the Au NPs allowed us to develop an INHIBIT logic gate-using Pb(2+) and Hg(2+) as inputs and the peroxidase-like activity of the Au NPs as the output. Finally, regulation of the peroxidase-like activity of the Au NPs through the two inputs Ag(+) and Bi(3+) enabled us to construct an XOR logic gate.

A new ditopic ratiometric receptor for detecting zinc and fluoride ions in living cells

The synthesis, characterization and ion binding properties of a new ditopic ratiometric receptor (1), based on 2-(4,5-dihydro-1H-imidazol-2-yl)phenol and crown ether moieties, have been described. The ditopic ratiometric receptor has been studied in sensing both F(-) and Zn(2+) ions, exhibiting different fluorescent colour changes from cyan green to blue/black observable by the naked eye under UV-light. The addition of Zn(2+) to the solution of 1 induced the formation of a 2 : 2 ligand-metal complex 1-Zn(2+), which displays a remarkable blue shift of the emission maxima of 1 from 455 nm to 400 nm due to the inhibition of excited-state intramolecular proton transfer (ESIPT) mechanism. The sensing processes were monitored by fluorescence/absorption titrations, and further confirmed by Job's plot and (1)H NMR titrations. The crystal structure of 1-Zn(2+) reveals that 1 binds Zn(2+) in four-coordinated modes. Furthermore, 1 is cell permeable and may be applied to detect trace Zn(2+) and F(-) during the development of a living organism.

Toehold-mediated nonenzymatic DNA strand displacement as a platform for DNA genotyping

Toehold-mediated DNA strand displacement provides unique advantages in the construction and manipulation of multidimensional DNA nanostructures as well as nucleic acid sequence analysis. We demonstrate a step change in the use of toehold-mediated DNA strand displacement reactions, where a double-stranded DNA duplex, containing a single-stranded toehold domain, enzymatically generated and then treated as a molecular target for analysis. The approach was successfully implemented for human DNA genotyping, such as gender identification where the amelogenin gene was used as a model target system, and detecting single nucleotide polymorphisms of human mitochondrial DNA. Kinetics of the strand displacement was monitored by the quenched Förster resonance energy transfer effect.