The REU program is open to all undergraduate students with disabilities (mobility, sensory, learning, psychological, medical, or other) who are majors in chemistry, biochemistry, or chemistry related fields.

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Poster title: The effect of analyte binding on the detection of PAH photosynthesized oxygen in a biorelevant solvent

Vennesa Valentine 1 , Micaih Murray 2 , Sharon Neal 2

1.Chemistry and Biochemistry Department, Alcorn State University 
2.Chemistry and Biochemistry Department, University of Delaware

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Abstract:

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 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 singlet oxygen 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 singlet oxygen 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 singlet oxygen sensor bleaching. Electronic
structure calculations (Gaussian 09) were used to calculate the binding of singlet oxygen 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
singlet oxygen  binding constant calculations.