Discipline: Chemistry and Chemical Sciences
Subcategory: Biochemistry (not Cell and Molecular Biology and Genetics)
Room: Exhibit Hall A
Vennesa Valentine - Alcorn State University
Co-Author(s): Sharon Neal, University of Delaware, Newark, DE; Micaih Murray, University of Delaware, Newark, DE
Polycyclic aromatic hydrocarbons (PAH) are environmental pollutants that are directly emitted into the atmosphere by incomplete combustion of organic matter such as wood, oil and natural gas. PAHs have been widely examined because some have harmful effects on human health and the environment. The tissues of marine organisms can be damaged by the singlet oxygen (1O2) produced when UV radiation is absorbed by PAH molecules. The detection of singlet oxygen is difficult because of its short lifetime and low intensity, remote spectrum. Consequently, the colorimetric method proposed by Kraljic and El Mohsni was designed to measure the production of singlet oxygen in the visible range. In this method, the imidazole (Imd) functions as an acceptor, binding with the 1O2 to form a trans-annular peroxide intermediate that bleaches the sensor p-nitrosodimethylaniline (RNO). The bleaching of the RNO is expected to be proportional to the 1O2 being produced by PAH photosensitization. This study aims to investigate the tendency of singlet oxygen to bind some photosensitizers rather than the acceptor, undermining the assay performance. The Kraljic & El Mohsni assay was implemented kinetically by collecting time-resolved UV-VIS absorption measurements of 9,10-dimethylanthracene (9,10-DMA) and 9,10-dicyanoanthracene (9,10-DCA) irradiated by simulated solar radiation in the presence of the assay reagents, Imd and RNO, in octanol, a biorelevant solvent. Several control assays (selected components omitted), were also measured. Molar absorptivity determinations were used to determine assay component concentrations and the rates of photodegradation and 1O2 sensor bleaching. Electronic structure calculations (Gaussian 09) were used to calculate the binding of 1O2 to the photosensitizers and other assay components. The photodegradation rates of the PAH photosensitizers and their apparent singlet oxygen production rates in the assays and controls will be compared to each other and the 1O2 binding constant calculations.
Funder Acknowledgement(s): The University of Delaware Graduate College and the Unidel Foundation.
Faculty Advisor: Sharon Neal, firstname.lastname@example.org
Role: I was responsible for collecting PAH photodecomposition and singlet oxygen production using time-resolved UV- VIS absorption measurements of 9,10-dimethylanthracene (9,10-DMA) or 9,10-dicyanoanthracene (9,10-DCA). I then used a computer software to analyze the data collected to formulate a spectrum. My project also included the use of the Gaussian software to compare the binding energy of the singlet oxygen to different compounds.