Date of Award

12-10-2018

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

First Advisor

Zhen Huang

Second Advisor

Jun Yin

Third Advisor

Markus W. Germann

Abstract

Nucleic Acids are the most important macromolecules in living systems. They directly participate in storing, transferring and expressing the genetic information, thereby controlling and regulating the function of living systems. Therefore, nucleic acid research will give us molecular insights into lives. Meanwhile, many novel research methods based on nucleic acids have been developed. Moreover, nucleic acid-based therapeutics have been developed rapidly over the past several years, leading to a revolution on drug discovery and disease study at the molecular level and the genetic level. Consequently, the structure and function studies on nucleic acids and protein-nucleic acid complexes have attracted tremendous research attention, especially in medical science and biological chemistry.

Since oxygen and selenium are in the same main group in the periodic table, we anticipate oxygen atoms on nucleic acids can be replaced by selenium atoms without significant perturbations on structure and function. Previously, we successfully completed the chemical and enzymatic synthesis of Se-modified nucleic acids (SeNA) with selenium substitutions at various positions. Indeed, we have demonstrated that the Se-modifications would not lead to significant changes in the structure. In addition, SeNA can largely facilitate nucleic acid-protein X-ray crystallography, and its unique properties may lead to many other potential applications, such as gene silencing, therapeutics and cellular imaging. This dissertation has explored potential applications of SeNA, including therapeutic and biochemical research, via structural and functional studies. We demonstrated that SeNA has great potential for antisense drug discovery because of its stronger nuclease resistance, better compatibility with RNase H and more efficient gene silencing in cells. SeNA could also be applied in cellular imaging via micro-X-ray fluorescence (microXRF), which allowed us to establish a novel approach to image mRNA transportation in cells. With this approach, we have successfully monitored the GFP mRNA in HeLa cell. Furthermore, we found that SeNA doesn’t perturb the structure of DNA/DNA polymerase complex, which allows an accurate structural determination of protein-nucleic acid complexes and provides a bright future on X-ray crystallography of nucleic acids and their protein complexes.

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