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Natural polynucleotides including Micrococcus lysodeikticus and calf thymus DNA exhibit enantioselective recognition to S-ofloxacin regulated by Cu(2+). This is the first report that ofloxacin and Cu(2+) have cooperative effects on the local distortions of polynucleotides. At the [Cu(2+)]/[base] ratio of 0.1, S-ofloxacin is more liable to induce the locally distorted structures of polynucleotides, of which the association constant of S-ofloxacin toward DNA-Cu(II) is three times higher than that of the R-enantiomer. The apparent increase of adsorption capability and cooperativity, as well as the change of adsorption mechanism were detected in the adsorption of ofloxacin enantiomers on polynucleotides upon Cu(II)-coordination. This study not only discloses the effect of the chiral drug on the structural transition of long double-stranded DNA, but provides fundamental data to develop a novel enantioseparation method based on natural polynucleotides., (© 2015 Wiley Periodicals, Inc.)

The specific interactions of Cu(2+) with self-complementary DNA sequences involving d[G4C4(GC)2G4C4], d[(GC)10], and d[(AT)10], as well as the chiral recognition mechanism of ofloxacin enantiomers via the Cu(II)-modulated DNAs, were investigated using characterizations of circular dichroism, gel electrophoresis, FT-IR spectroscopy, UV melting measurement, electron paramagnetic resonance, and HPLC. The Cu(II)-coordinated GC-rich DNAs exhibit amplified enantioselectivity toward the S-enantiomer of ofloxacin. Especially in the case of d[G4C4(GC)2G4C4], ofloxacin enantiomers intercalate into the two adjacent guanine bases through the minor groove mediated by Cu(2+), which leads to a more favorable binding between S-ofloxacin and DNA. The highest ee value of ofloxacin enantiomers in the permeate after being adsorbed by the Cu(II)-DNA complex is obtained as 49.2% in the R-enantiomer at the [Cu(2+)]/[base] molar ratio of 0.25, while at the [Cu(2+)]/[base] molar ratio of 0.05 the highest ee value of ofloxacin enantiomers in the retentate reaches 26.3% in the S-enantiomer. This work illustrates a novel promising route to construct DNA-based chiral selectors toward certain drug enantiomers through the programmable enantioselective recognition on the basis of DNA chirality and the specific binding of transition metal ions.

DNA-based chiral selectors are constructed to discriminate ofloxacin enantiomers through metal-ion anchoring on a special DNA double helix that contains successive GC pairs. The effects of metal ions involving Mg(2+), Ni(2+), Cu(2+), Ag(+), and Pt(2+) were studied on the regulation of DNA chiral discrimination towards ofloxacin enantiomers. It is shown that DNA-Cu(II) complexes exhibit the highest enantioselectivities at the [Cu(2+)]/base ratio of 0.1. The enantiomeric excess can reach 59% in R-enantiomer after being adsorbed by the RET-Cu(II) complex. Stereoselective recognition of ofloxacin enantiomers on the double helix is tunable via external stimulus, providing a programmable desorption process to regenerate DNA. This DNA-based chiral selector exhibits excellent reusability without apparent loss of enantioselectivity after three cycles of adsorption and desorption., (© 2014 Wiley Periodicals, Inc.)

Natural polynucleotides including Micrococcus lysodeikticus and calf thymus DNA exhibit recognition to S-ofloxacin regulated by Cu2+. This is the first report that ofloxacin and Cu2+ have cooperative effects on the local distortions of polynucleotides. At the [Cu2+]/[base] ratio of 0.1, S-ofloxacin is more liable to induce the locally distorted structures of polynucleotides, of which the association constant of S-ofloxacin toward DNA-Cu(II) is three times higher than that of the R-enantiomer. The apparent increase of adsorption capability and cooperativity, as well as the change of adsorption mechanism were detected in the adsorption of ofloxacin enantiomers on polynucleotides upon Cu(II)-coordination. This study not only discloses the effect of the chiral drug on the structural transition of long double-stranded DNA, but provides fundamental data to develop a novel enantioseparation method based on natural polynucleotides. Chirality 27:306-313, 2015. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]