We report a very selective and sensitive spectroscopic detection of Z-DNA embedded in B-DNA in condensed as well as non-condensed DNA using anionic Ni(II) meso-tetrakis(4-sulphonatophenyl)porphyrin, NiTPPS. A combination of micromolar concentrations of Ni(II) and spermine 4 + allowed us to prepare left-handed Z-DNA in short oligonucleotides without DNA condensation. A strong induced circular dichroism (ICD) signal was observed in the visible absorption region when NiTPPS was added to BZ DNA (Z-DNA fragment located at the end of a B-DNA tract with one B/Z DNA junction) and BZB DNA (Z-DNA sequence embedded in B-DNA having two B/Z DNA junctions). Almost no ICD signal was detected when NiTPPS was added to B-DNA. NiTPPS showed different binding modes with condensed and non-condensed Z-DNAs and allowed the distinction between condensed Z-DNA (positive bisignate CD couplet) and non-condensed Z-DNA (negative bisignate CD couplet).
Bibliographical noteFunding Information:
MB thanks the University of Wyoming Start-Up Fund. AEH thanks the National Center for Research Resources ( 5P20RR016469 ) and the National Institute for General Medical Science ( 8P20GM103427 ), a component of the National Institutes of Health (NIH) , and the NSF-EPSCoR-EPS-1004094 and the NSF CHE-0747949 .
All Science Journal Classification (ASJC) codes
- Inorganic Chemistry