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dc.contributor.advisorDaniel G. Nocera.en_US
dc.contributor.authorReece, Steven Y., 1980-en_US
dc.contributor.otherMassachusetts Institute of Technology. Dept. of Chemistry.en_US
dc.date.accessioned2008-03-26T21:10:13Z
dc.date.available2008-03-26T21:10:13Z
dc.date.copyright2007en_US
dc.date.issued2007en_US
dc.identifier.urihttp://hdl.handle.net/1721.1/40867
dc.descriptionThesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2007.en_US
dc.descriptionThis electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.en_US
dc.descriptionIncludes bibliographical references.en_US
dc.description.abstractCharge transport and catalysis in enzymes often rely on amino acid radicals as intermediates. The generation and transport of these radicals are synonymous with proton-coupled electron transfer (PCET), which intrinsically is a quantum mechanical effect as both the electron and proton tunnel. The caveat to PCET is that proton transfer (PT) is fundamentally limited to short distances relative to electron transfer (ET). This predicament is resolved in biology by the evolution of enzymes to control PT and ET coordinates on very different length scales. In doing so, the enzyme imparts exquisite thermodynamic and kinetic control over radical transport and radical-based catalysis at cofactor active sites. New tools are needed to study PCET reactions of amino acid radical in biology. This thesis describes methods for photogeneration of amino acid radicals, with particular emphasis on tyrosine. Unnatural fluorotyrosine amino acids are developed to vary the driving force for proton and electron transfer in PCET reactions of tyrosyl radical (Ye), and to provide unique spectroscopic handles to study enzymes utilizing multiple Yes. These tools allow for an in-depth study of the PCET mechanism of tyrosyl radical generation, both in solution and within the ribonucleotide reductase enzyme. Enzymatic acitivity of class I E. coli ribonucleotide reductase requires the transport of charge from an assembled diiron-tyrosyl radical cofactor to the enzyme active site over 35 A away via an amino acid radical hopping pathway spanning two protein subunits.en_US
dc.description.abstract(cont.) To study the mechanism of this radical transport, we have developed photochemical RNRs wherein radical generation, transport, and enzymatic turnover can be initiated by UV-vis excitation of a peptide bound to the subunit containing the enzyme active site. This method allows us to observe Y*s competent for initiating turnover on the peptide bound to the protein subunit. Turnover assays with the wild-type and mutant proteins show that both the electron and proton move along a unidirectional pathway to affect radical transport in this subunit.en_US
dc.description.statementofresponsibilityby Steven Y. Reece.en_US
dc.format.extent232 p.en_US
dc.language.isoengen_US
dc.publisherMassachusetts Institute of Technologyen_US
dc.rightsM.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.en_US
dc.rights.urihttp://dspace.mit.edu/handle/1721.1/7582en_US
dc.subjectChemistry.en_US
dc.titlePhotochemical ribonucleotide reductase for the study of proton-coupled electron transferen_US
dc.typeThesisen_US
dc.description.degreePh.D.en_US
dc.contributor.departmentMassachusetts Institute of Technology. Dept. of Chemistry.en_US
dc.identifier.oclc213296718en_US


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