Date of Publication


Degree Type

Honors Thesis


Chemistry and Biochemistry

First Advisor

Dr. Joshua Blose, Associate Professor, Chemistry and Biochemistry


In the cell, chemically diverse solutes known as osmolytes accumulate in response to environmental stresses. To add to the understanding of how the environment inside a cell affects nucleic acid folding and function, we investigated the influence of cosolutes on the transition from B-DNA to Z-DNA in model DNA duplexes. Distinct from the familiar right-handed BDNA helical conformation, Z-DNA is a left-handed double helical structure with its phosphodiester backbone arranged in a zig-zag pattern that is unique to Z-DNA. Moreover, due to the correlation between Z-DNA formation potential and regions of active transcription, ZDNA is believed to serve a vital role in the transcription process. Previous literature has shown that divalent metal ions such as Ca2+ and Mg2+ can promote the formation of Z-DNA in vitro and previous studies from our lab have shown that the presence of osmolytes enhances the formation of Z-DNA, significantly decreasing the in vitro [Na+] required for the transition. In our latest experiments, we examined the combination of divalent ions and osmolytes and its influence on the B-Z transition. We utilized circular dichroism (CD) spectroscopy to monitor the B-Z transition in a divalent ion background in the presence and absence of a model osmolyte, PEG 200. Our results thus far suggest that PEG 200 greatly enhances the formation of Z-DNA in the presence of Mg2+ as compared with Na+ alone and significantly decreases the [Mg2+] required for folding in vitro. Our results with Ca2+ thus far suggest that its folding of Z-DNA is similarly enhanced by PEG 200 and that the effect of metal ions on Z-DNA formation can be observed in vivo.