PROBING PHOTODYNAMIC DAMAGE IN NUCLEIC ACIDS WITH A DAMAGE-SPECIFIC DNA BINDING PROTEIN: A COMPARISON OF THE B and Z DNA CONFORMATIONS |
| |
Authors: | Ross S. Feldberg Caroline Brown Josephine A. Carew Judith L. Lucas |
| |
Affiliation: | Department of Biology, Tufts University, Medford, MA 02155, USA |
| |
Abstract: | —We have employed a damage-specific DNA binding protein from human cells as a probe for base damage in polymers irradiated with white light in the presence of methylene blue. Protein-recognizable damage is introduced only into guanine-containing polymers and quenching of damage introduction by H2O and sodium azide suggest the involvement of a singlet oxygen mechanism. Using poly d(G-m5C), we have demonstrated that the left-handed double helical Z conformation is much less susceptible to guanine photooxidation than is the usual B conformation. We speculate that this difference in reactivity may reflect steric hindrance at the purine C-4 position and could provide some insight into the initial steps of the reaction between singlet oxygen and guanine in nucleic acid polymers. |
| |
Keywords: | |
|
|