Copper transfer from laccase and photophysical and spectroscopic studies of copper phenanthroline complexes with DNA and RNA

Kelley Ann Meadows, Purdue University


Presented here are investigations of copper donation from the blue copper protein laccase and photophysical and spectroscopic studies of copper(I) phenanthroline complexes with DNA and RNA. In Chapter 1, tree laccase, a multi-copper oxidase, is studied as a copper donor in conjunction with the demetalated form of the blue copper protein stellacyanin. Copper transfer could be observed under reducing conditions in the absence of air. Only about 10% of the total copper in laccase could be transferred regardless of the amount of acceptor present in solution. EPR results in conjunction with thiol titrations indicate that there is no net loss of type 1 copper from laccase but that there is loss of type 2 copper as well as a small amount of type 3 copper. Chapter 2 describes the noncovalent binding interactions of a copper(I) phenanthroline complex with RNA. UV-Visible, circular dichroism and luminescence results indicate that Cu(bcp)$\sb2\sp+$ (where bcp denotes 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) binds to various types of RNA. Viscometry data indicate that the binding interaction is not intercalative. Binding is probably electrostatic in a groove and may involve a conformational change of the RNA polymer. On the other hand, Cu(dmp)$\sb2\sp+$ (where dmp denotes 2,9-dimethyl-1,10-phenanthroline) was found not to bind to RNA at all, based on spectroscopic studies. Chapter 3 describes the synthesis of an unsymmetrical copper(I) phenanthroline complex, Cu(dmpp)$\sb2\sp+$, where dmpp denotes 2,9-dimethyl-4-phenyl-1,10-phenanthroline, and its noncovalent binding interactions with DNA and RNA. UV-Visible, luminescence, and circular dichroism results point to a binding interaction between the copper complex and DNA and RNA. Again, as above, viscometric data indicates that intercalation is not occurring. CD studies indicate that a conformational change of the nucleic acid may be occurring to accommodate the drug. Finally, this work along with that in Chapter 2 points to a relationship between the nature of binding of copper(I) phenanthroline complexes with nucleic acids and the presence of phenyl substituents in the 4 and 7 positions of the phenanthroline ligand.




McMillin, Purdue University.

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