Barrett, The Honors College Thesis/Creative Project Collection
Barrett, The Honors College at Arizona State University proudly showcases the work of undergraduate honors students by sharing this collection exclusively with the ASU community.
Barrett accepts high performing, academically engaged undergraduate students and works with them in collaboration with all of the other academic units at Arizona State University. All Barrett students complete a thesis or creative project which is an opportunity to explore an intellectual interest and produce an original piece of scholarly research. The thesis or creative project is supervised and defended in front of a faculty committee. Students are able to engage with professors who are nationally recognized in their fields and committed to working with honors students. Completing a Barrett thesis or creative project is an opportunity for undergraduate honors students to contribute to the ASU academic community in a meaningful way.
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- Creators: Department of Chemistry and Biochemistry
The experiment was conducted to analyze the role of menaquinone (MQ) in heliobacteria’s reaction center (HbRC). Their photosynthetic apparatus is a homodimeric of type I reaction center (1). HbRC contains these cofactors: P800 (special pair cholorphyll), A0 (8-hydroxy-chlorophyll [Chl] a), and FX (iron-sulfur cluster). The MQ factor is bypassed during the electron transfer process in HbRC. Electrons from the excited state of P800 (P800*) are transported to A0 and then directly to Fx. The hypothesis is that when electrons are photoaccumulated at Fx, and without the presence of any electron acceptors to the cluster, they would be transferred to MQ, and reduce it to MQH2 (quinol). Experiments conducted in the past with HbRC within the cell membranes yielded data that supported this hypothesis (Figures 4 and 5). We conducted a new experiment based on that foundation with HbRC, isolated from cell membrane. Two protein assays were prepared with cyt c553 and ascorbate in order to observe this phenomenon. The two samples were left in the glove box for several days for equilibration and then exposed to light in different intensity and periods. Their absorption was monitored at 800 nm for P800 or 554 nm for cyt c553 to observe their oxidation and reduction processes. The measurements were performed with the JTS-10 spectrophotometer. The data obtained from these experiments support the theory that P800+ reduced by the charge recombination of P800+Fx-. However, it did not confirm the reduction of P800+ done by cyt c553¬ which eventually lead to a net accumulation of oxidized cyt c553; instead it revealed another factor that could reduce P800+ faster and more efficient than cyt c553 (0.5 seconds vs several seconds), which could be MQ. More experiments need to be done in order to confirm this result. Hence, the data collected from this experiment have yet to support the theory of MQ being reduced to MQH2 outside the bacterial membranes.