Judith A. Walmsley

• Ph.D., Inorganic Chemistry: University of North Carolina at Chapel Hill
• B.A., Chemistry: Florida State University

Research Interests

• Inorganic and Bioinorganic Chemistry: Synthesis and characterization of transition and main-group metal complexes in which the ligands are: (a) biomolecules such as nucleotides and amino acids; (b) multidentate ligands capable of cyclic or complex bridged structures. Metals include Pd(II), Pt(II), Au(III), and Ru(II)/ (III).

• Biomolecular Structure: A study of the complex and macromolecular structures formed in solution by guanine and adenine nucleic acid fragments; the structures are formed via hydrogen bonding, base stacking, and interaction with monovalent cations.

• Inorganic Chemistry: Our research in inorganic chemistry can be separated into several different projects involving different metal ions. We have been investigating cyclic species formed between Pd(II) and the purine nucleotides guaniosine 5'-monophosphate and inosine 5'-monophosphate. The Pd(bidentate diamine)(5'-GMP) system forms a cyclic tetramer (Figure shown) in which the nucleotide serves as a bridging ligand between the Pd(II) ions.
  
  
  Pd(en)(5'-GMP) tetramer
  
  
  Although 5'-IMP also formsa cyclic tetramer with Pd(II) in aqueous solution, it appears to have a different conformation. In conjunction with colleagues at the University of Texas Health Science Center in San Antonio, we are investigating possible anti-tumor activity of some of the complexes.
  
  We are currently working on the synthesis of cyclic species where the metal is Au(III) or Ru(II) or (III). In these cases, the ligands are other bridging diamine molecules, as well as the purine mononucleotides. Our plans are to also synthesize more complex architectures by employing metals having octahedral geometry and/or multidentate bridging ligands. The electrochemical behavior will be investigated for the redox active species.
  
  
• Nucleotide Structures: Research on biomolecular structure of guanine nucleotides and adenine nucleotides in aqueous solution began a number of years ago with  work on guanosine 5'-monophosphate. Although the system Na₂(5'-GMP) might be expected to  be quite simple, ¹H NMR has shown that, in the presence of Na⁺ or K⁺, concentrated solutions of 5'-GMP self-assembles into a cyclic tetrameric species held together by hydrogen bonds. These tetrads are able to stack upon each other through hydrophobic and electrostatic interactions to form complex structures. The Na⁺ ion resides in the central cavity of the tetramer. However, we believe that the larger K⁺ ion induces a hydrogen-bonded helical structure with the cations in the center of the helix. In both cases, the cation coordinates to the carbonyl oxygen atoms of the guanine base as well as neutralizing the negative charges on the phosphates. Not only do guanine mononucleotides form such structures, but oligonucleotides do so as well and the self-association is even stronger. Molecular weights as high as 200,000-400,000 have been obtained, depending on the concentration of K⁺. Recent work done on a dodecamer suggests an octamer containing a Z-DNA to B-DNA junction and cylindrical pore, probably the site of the alkali cations. A manuscript on the octamer is in preparation.

 Positions Available

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Opportunities for financial support are available on a competitive basis.