Spring 2011 Biomedical Seminar Series
April 1, 2011
Electron Transfer Rates Determine Product Distribution in P450 Catalyzed Dioxygen Reduction
MBRS-RISE MS to PhD Scholar
Developing electrode-driven biocatalytic systems utilizing the P450 cytochromes for selective oxidations depends not only on achieving electron transfer (ET) but doing so at rates that favor native-like turnover. Herein we report studies that correlate rates of heme reduction with ET pathways and resulting product distributions. We utilized single-surface cysteine mutants of the heme domain of P450 from Bacillus megaterium and modified the thiols with N-(1-pyrene)-iodoacetamide, affording proteins that could bond to basal-plane graphite. Of the proteins examined, Cys mutants at position 62, 383, and 387 were able to form electroactive monlayers with similar E1/2 values (-335 to -340 mV vs AgCl/Ag). Respective ET rates (kso) and heme-cysteine distances for 62, 383, and 387 are 50 s-1 and 16 ?, 0.8 s-1 and 25 ?, and 650 s-1 and 19 ?. Experiments utilizing rotated-disk electrodes were conducted to determine the products of P450-catalyzed dioxygen reduction. We found good agreement between ET rates and product distributions for the various mutants, with larger kso values correlating with more electrons transferred per dioxygen during catalysis.
Elucidation of the critical cis-regulatory region of the LTP4 promoter in Arabidopsis thaliana
Bridges to the PhD Scholar
Arabidopsis thaliana is a plant model we use to study the mechanism of senescence, the process of plant aging. Emerging evidence suggests that lipid transfer proteins (LTPs) play a critical role in meristem senescence. These LTPs are highly expressed in the plant’s bolt, the flower primordia, as the plant transitions to the flowering stage. The floral transition (FT) was connected earlier to a rise in oxylipin levels in leaves (Banuelos et al., 2008). These oxylipins maybe carried by LTPs from leaves to inflorescence structures. The promoter of the LTP4 gene was found to contain several potential cis- regulatory domain sequences (DS), termed the module, predicted to form protein-DNA interactions. It is proposed that mutations within this highly conserved region in the LTP4 promoter may suppress the transcription of the LTP4 gene thus limiting the amount of oxylipins being transported throughout the plant.
Influence of Magnetite in Amyloid Beta Aggregation
MBRS-RISE MS to PhD Scholar
Magnetite has gathered considerable attention in an array of different research fields due to its low toxic effects, paramagnetic properties, and controllable size distribution; and may play a role in the formation of amyloid beta fibrils, the central landmark of AlzheimerÂs diesease. Magnetite has been found to be present in the plaques of people with AlzhemierÂs disease [1, 2], leading some to believe it is aiding in the formation of amyloid beta fibrils. Research has been done to see if it aids in the formation of the fibrils [3, 4]; none of the results indicating that it catalyzes the formation of amyloid fibrils. The research however involved surfactant based magnetite, which would not be present in-vivo and involved amyloid systems that were not amyloid beta. It is because of this that we wish to study uncoated magnetite and coated magnetiteÂs effect, if any, on the formation of amyloid beta fibrils.