Morris Laboratory
Research
Analysis
of Nucleosides and their Derivatives using Microfluidic Devices
Nucleoside derivatives, especially those that are guanosine-based, are
important markers for diagnosing and/or monitoring serious diseases and
clinical conditions. These markers include several methylated
guanosine derivatives associated with thyroid cancer and the ubiquitous
oxidative DNA damage marker 8-hydroxy-2’-deoxyguanosine
(8-OH-dG). With the exclusion of ionizing radiation, oxidative
DNA damage is associated with the metal-dependent decomposition of H2O2 and subsequent generation of reactive
oxygen species (ROS). However, the specific role of metal ions in
oxidative DNA damage is not well characterized.
Oxidative damage to DNA appears to be very selective with the
guanosine-based derivative 8-OH-dG increasing substantially over
background levels. Owing to the high reactivity and short
lifetimes of ROS, they must react close to the site of formation.
Evidence suggests that DNA has the capability of binding metal ions,
and reaction of H2O2 at or close to the site of metal binding
would account for the selective nature of oxidative damage. In
the specific case of Fe (II)-DNA interactions, recent work indicates
that Fe (II) interacts with guanine at the N7 position. However,
the guanine base is not the only possible site for metal binding.
Given the variety of sites in DNA to which metal ions can bind
(phosphate groups vs. different positions on individual bases),
questions arise regarding the relationship between DNA binding sites
and production of modified nucleosides.
Our research group has studied the interactions of Fe (II), Cu (II) and
Cr (III) with the nucleoside 2’-deoxyguanosine (dG) and nucleotide
2’-deoxyguanosine-5’-monophosphate and the ability of the metal ion/H2O2 system to produce 8-OH-dG using reversed
phase HPLC with UV absorption detection. The results suggest
differing degrees of interaction of the metal ions with both the
guanine base and phosphate group on the nucleoside and
nucleotide. However, studies employing the mononucleoside and
mononucleotide cannot account for the effects of adjacent bases or base
pairing on metal ion interactions and ROS production. Our current
work involves probing oxidative damage to double-stranded DNA from ROS
produced by metal ions and H2O2 and comparing the relative amounts of
damage to specific bases along with production of the oxidative damage
marker 8-OH-dG to discern the degree of site specific damage due to
metal ion binding. The results from such a study better reflect
the interactions between metal ions, bases and phosphate groups and are
more physiologically relevant.
Email Daniel Morris
Office: FL 102
Phone: x8314
