Biologically Inspired Applications of TAML Activators

Chapter 1. Catalysis plays a huge role in the emerging field of Green chemistry. The contribution of TAML activators to that field is described here. A brief background in the chemistry and application of TAML activators is provided along with a brief introduction to the following chapters.;Chapter 2. The development of chemical sporicides that are more environmentally friendly and rapid acting is important for public health protection. For example, resilient spores often cause hospital-acquired infections and the spore forming bacterium Clostridium difficile has emerged as the leading cause of hospital-acquired (nosocomial) diarrhea, which can be fatal especially for the elderly. Herein we describe an advance in the chemistry of TAML activator/peroxide (TAML activators are oxidation catalysts based on tetra-amido macrocyclic ligands) that enables the rapid deactivation of spores of C. difficile and the common food borne pathogen, C. perfringens. The system becomes potently effective on addition of small amounts of nitrite (low mM). Conditions for spore deactivation were optimized for C. perfringens to reduce viable spores by 7log 10 in 10 min with TAML activator (10 microM), tBuOOH (50 mM) and NaNO2 (5 mM) at pH 10. A 6.2log10 reduction in viable C. difficile spores was achieved in 10 min with a 5.6log10 reduction in just 5 min. With regard to possible mechanisms of the disinfection process, L-tyrosine is cleanly and regioselectively nitrated by TAML activator/ROOH/NaNO2 (R = H, tBu) suggesting that an active nitrogen oxide species is involved. The results characterize a simple, new, highly effective sporicidal and synthetic system.;Chapter 3. Post-translational nitration of tyrosine residues plays a crucial role in protein regulation. There are many mechanisms that may lead to protein nitration, one of which being the peroxidase catalyzed oxidation of nitrite and tyrosine to NO2• and a tyrosyl radical, respectively, followed by radical coupling. TAML activators are a known peroxidase mimic and their ability to catalyze the nitration of free tyrosine and peptide bound tyrosine residues was explored. Angiotensin I, a decapeptide containing a single tyrosine residue, was used as a model compound to study the TAML activator catalyzed nitration. TAML activator, in the presence of nitrite and H2O2, was successfully able to catalyze the conversion of tyrosine to 3-nitrotyrosine. Angiotensin I was also successfully nitrated with the TAML/H2O2/NO 2- system. Confirmation of the nitro group residing on the single tyrosine residue was provided by ESI-MS3 analysis.;Chapter 4. The coupling of TAML activators, effective peroxidase mimics with potential for use in a number of real world applications, with glucose oxidase, an H2O2 producing enzyme, was successfully achieved. Astonishingly, this system does not appear to lead to any sizeable deactivation of the enzyme and is shown to be effective over the pH range of 6.5 -- 9.5 for the catalytic oxidation of Orange II. The robustness of the system has allowed for the utilization of unpurified sugars from such sources as crude aqueous extracts of fruits such as bananas. Incorporating invertase for sucrose hydrolysis has allowed for sucrose to also act as a sacrificial electron donor, increasing efficiency.