The Chiral Separation Of Ofloxacin Enantiomers Using G-rich Double-Stranded Oligonucleotides

As a kind of natural chiral biomacromolecule, DNA has inherent chiral propertyand controllable self-assembly structure, which make it promising in the field of chiralrecognition. Furthermore，the capacity of chiral recognition can be enhanced bybinding small organic molecule ligands or metal ions to regulate adsorption site andchange the assembled structure, which lay the foundation for rational design of chiralselectors with high enantioselectivity. In this research, a novel chiral selector ofDNA-metal complex based on G-rich oligonucleotides has been constructed forseparation of ofloxacin enantiomers.Firstly, the G-rich double-stranded oligonucleotides involving the htelo, RET,c-kit2and VEGF are selected as DNA scaffolds. The interaction among differentmetal ions including Mg2+、Cu2+、Ni2+、Ag+and Pt2+, ofloxain enantiomers anddouble-stranded oligonucleotides is investigated by fluorescence and circulardichroism (CD) spectroscopy. Among five kinds of metal ions, Cu2+has the strongesteffect on the binding of ofloxacin and the structure of nucleic acids. Next, therecognition mechanism of DNA-Cu(II) complex is studied by CD spectroscopy,CDmelting and Isothermal Titration Calorimetry (ITC). It has been found that Cu2+ionsbinds preferentially with the duplex containing GpG motifs and the binding constantof DNA-Cu(II) complex towards S-ofloxacin is9.82×105M-1,which is higher thanRac-ofloxacin. Finally, a novel DNA-metal complex constructed via metalion-coordination is used as chiral selector to separate ofloxacin enantiomers. Theaddition of Cu2+can improve the chiral separation capacity of G-rich double-strandedoligonucleotides. Furthermore, the reversible recognition of G-rich double-strandedoligonucleotides for ofloxacin enantiomers is investigated. The desorption ofofloxacin enantiomers from DNA-Cu(II) complex can be realized through addingEDTA and changing the pH value at the same time. After three stages of separation,R-enantiomer with an e.e.pof85%and S-enantiomer with an e.e.Rof78%can beobtained adopting c-kit2-Cu(II) complex as the chiral selector.