Studies On Ligand Aggregates For Recognizing Nuclear Acid Structures

DNA templated dye assemblies provide a way to design novel aggregates with promising properties,such as exciton circuits,artificial light collection systems,molecular-scale photonic devices and sensors.In the presence of DNA,some ligands exhibit different optical properties from their own monomers.These optical activities can be determined by absorption,fluorescence,and circular dichroism spectra.Since the folding of G-quadruplex can be affected by sequences,the kind and the concentration of cation ion in solution,the diversity of G-quadruplex structures provides various platforms for ligand to assemble.Therefore,this work explored the specific assembly of different ligands on DNA by using both of left-and right-handed G-quadruplexes and the existence of apurinic site,and it will provide a new idea for the chiral regulation of G-quadruplexes on ligand aggregates.The main contents are as follows:1.Concurrent formation of H-and J-aggregates of dyes with chiralities individually determined by G-quadruplex handednessDNA templated dye assemblies pave an easy way to regulate the optical properties of molecular aggregates.G-quadruplexes(G4s)provide versatile DNA platforms for the dye assemblies since their foldings can be easily tuned by cation ions and sequences.In this work,we found that the G4 handedness can be used to control the aggregate chirality of a dye of 3,3'-diethylthiacarbocyanine(DiSC₂(3)).The left-handed and right-handed G4s can template the concurrent formation of the J-and H-aggregates of DiSC₂(3)with emergence of the featured absorption spectra.However,the chiral J-aggregate of DiSC₂(3)can be formed only on the left-handed G4s,while the chiral H-aggregate is otherwise grown only on the right-handed G4s,as confirmed by the induced circular dichroism(ICD)spectra with the characteristic splitting bands.Additionally,these G4s even at tens of nmol/L level are efficient to produce these chiral aggregates,demonstrating the high sensitivity of G4s in creating these optically active dye assemblies.The possible growth sites of the aggregates are proposed by the sequence length-dependent assemblies.Our work will provide a new way to control the chiral assemblies of dye aggregates via the G4 handedness.2.G-quadruplex apurinic site programmed chirality of cyanine assemblies and applicationsDNA-tuned chromophore assemblies have received much attention due to variant functionalities.Owing to easy conformation implementation,G-quadruplexes(G4s)have been widely used as iniators to grow chromophore assemblies with controllable chirality.However,the programmed chirality regulation for a given G4 has not been realized using a primitive tunner.In this work,we replaced a middle guanine in G4 with an apurinic site(AP site)in different G-tract positions.Although all of this replacement changed the G4 conformation from hybrid to antiparallel,the chirality of pinacyanol(PIN)assemblies grown on these G4s can be programmably regulated.The G4 with the AP site at the 5'most G-tract grew right-handed assemblies,while that with the AP site at the 3'most G-tract grew left-handed assemblies.The chiralities of assemblies were almost totally mirrored within 450-700 nm.Furthermore,we found that the AP site provided a specific binding site for guanosine and guanine,and this binding event sensitively declined the chiral assemblies.Thus,selective chromophore assemblies-based sensors can be established based on chirality responses.Our work first demonstrate the AP site programmed chirality regulation of G4-grown chromophore assemblies and will find wide applications in chiral devices.