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Dissertation Information for Mitchell P. Maddox III

NAME:
- Mitchell P. Maddox III

DEGREE:
- Ph.D.

DISCIPLINE:
- Chemistry

SCHOOL:
- Emory University (USA) (2005)

ADVISORS:
- Debra L. Mohler

COMMITTEE MEMBERS:
- Fred M. Menger
- David G. Lynn

MPACT Status: Fully Complete

Title: I. Photoinduced DNA cleavage by cyclopentadienyl metal complexes conjugated to DNA recognition elements. II. Dissociation of DNA-histone assemblies resulting from protein side-chain functionalization. III. Development of the CpW(CO)3CH3 radical precursor as a footprinting agent for chromatin sub-structures

Abstract: The question of how carbon-based radicals interact with different biomolecules has become an area of great research interest over the last several years. Here we describe the production and DNA cleavage ability of two new netropsin carbon radical precursor conjugates. The first conjugate utilized in these studies uses a CPW(CO) 3 CH 3 metal complex as a methyl radical source. This conjugate exhibited improved DNA cleaving ability compared to that of the metal complex without the DNA recognition element. However, this DNA cleaving conjugate showed no sequence specificity, despite the fact that the netropsin was binding to AT rich sequences within the target DNA. To develop a sequence specific DNA-cleaving agent, a second conjugate was developed in which the radical precursor was a CPW(CO) 3 Ph moiety attached to the netropsin molecule via the para position of the phenyl ring. This compound gave site specific cleavage. In the further expansion of the idea of site specific DNA cleavage, the development and synthesis of a highly specific DNA binding hairpin is described. Additionally, the effect of DNA-associated proteins on the DNA cleaving ability of carbon radicals is also discussed. For these studies, a DNA/histone protein H1 assembly was subjected to the photolytic generation of the methyl radical from CPW(CO) 3 CH 3 . Interestingly, DNA/histone complex dissociation was observed instead of DNA crosslinking or protein cleavage, which had been observed for hydroxyl radical reactions with DNA and proteins. This dissociation was due in part to the radical-induced conversion of the lysine side chain amines to aldehydes, a transformation that is important to the function of the histone H1 because these side chain amines carry the positive charge responsible for the electrostatic interaction between the protein and the negatively charged DNA backbone. Finally, the discovery that the CPW(CO) 3 CH 3 methyl radical precursor showed no sequence specificity suggested the use of this complex as a DNA footprinting agent. As such, attempts were made to footprint several different sub-structures of the chromatin fiber, as well as to answer some fundamental questions about these structures. The first sub-structure of interest was that of the nucleosome, the most fundamental component of the chromatin fiber. The nucleosome is the most clearly understood structure of chromatin and provides a standard for testing this new footprinting agent. The chromatosome was our second target and is one step up in complexity from the nucleosome. This also allowed us probe the fundamental question of where the histone H1 protein is located within the chromatosome structure.

MPACT Scores for Mitchell P. Maddox III

A = 0
C = 0
A+C = 0
T = 0
G = 0
W = 0
TD = 0
TA = 0
calculated 2008-03-22 15:53:58

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