Biomimetic modeling of the nitrogen-centered radical postulated to occur during the inhibition of ribonucleotide reductases by 2'-azido-2'-deoxynucleotides

Ribonucleotide reductases (RNR) are essential enzymes that catalyze the reduction of ribonucleotides to 2'-deoxyribonucleotides, which is a critical step that produces precursors for DNA replication and repair. The inactivation of RNR, logically, would discontinue producing the precursors of the DNA of viral or cancer cells, which then would consequently end the cycle of DNA replication. Among different compounds that were found to be inhibitors of RNR, 2'-azido-2'-deoxynucleotide diphosphates (N3NDPs) have been investigated in depth as potent inhibitors of RNR. Decades of investigation has suggested that the inactivation of RNR by N3NDPs is a result of the formation of a nitrogen-centered radical (N·) that is covalently attached to the nucleotide at C3' and cysteine molecule C225 [3'-C(R-S-N·-C-OH)]. Biomimetic simulation reactions for the generation of the nitrogen-centered radicals similar to the one observed during the inactivation of the RNR by azionuclotides was investigated. The study included several modes: (i) theoretical calculation that showed the feasibility of the ring closure reaction between thiyl radicals and azido group; (ii) synthesis of the model azido nucleosides with a linker attached to C3' or C5' having a thiol or vicinal dithiol functionality; (iii) generation of the thiyl radical under both physiological and radiolysis conditions whose role is important in the initiation on RNR cascades; and (iv) analysis of the nitrogen-centered radical species formed during interaction between the thiyl radical and azido group by electron paramagnetic resonance spectroscopy (EPR). Characterization of the aminyl radical species formed during one electron attachment to the azido group of 2'-azido-2'-deoxyuridine and its stereospecifically labelled 1'-, 2'-, 3'-, 4'- or 5,6-[2H 2]-analogues was also examined. This dissertation gave insight toward understanding the mechanism of the formation of the nitrogen-centered radical during the inactivation of RNRs by azidonucleotides as well as the mechanism of action of RNRs that might provide key information necessary for the development of the next generation of antiviral and anticancer drugs.

The role of neighborhood organizations in the production of gentrifiable urban space: The case of Wynwood, Miami's Puerto Rican barrio

Partnerships between government and community-based actors and organizations are considered the hallmark of contemporary governance arrangements for the revitalization and gentrification of economically distressed, inner city areas. This dissertation uses historical, narrative analysis and ethnographic methods to examine the formation, evolution and operation of community-based governance partnerships in the production of gentrifiable urban space in the Wynwood neighborhood of Miami, FL between 1970 and 2010. This research is based on more than four years of participant observation, 60 in-depth interviews with respondents recruited through a purposive snowball sample, review of secondary and archival sources, and descriptive, statistical and GIS analysis. This study examines how different organizations formed in the neighborhood since the 1970s have facilitated the recent gentrification of Wynwood. It reveals specifically how partnerships between neighborhood-based government agencies, nonprofit organizations and real estate developers were constructed to be exclusionary and lead to inequitable economic development outcomes for Wynwood residents. The key factors conditioning these inequalities include both the rationalities of action of the organizations involved and the historical contexts in which their leaders’ thinking and actions were shaped. The historical contexts included the ethnic politics of organizational funding in the 1970s and the “entrepreneurial” turn of community-based economic development and Miami urban politics since the 1980s. Over time neighborhood organizations adopted highly pragmatic rationalities and repertoires of action. By the 2000s when Wynwood experienced unprecedented investment and redevelopment, the pragmatism of community-based organizations led them to become junior partners in governance arrangements and neighborhood activists were unable to directly challenge the inequitable processes and outcomes of gentrification.