A. James Clark School of Engineering
Permanent URI for this communityhttp://hdl.handle.net/1903/1654
The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item Membrane models of E. coli containing cyclic moieties in the aliphatic lipid chain(2012) Pandit, Kunal; Klauda, Jeffery B; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Most molecular dynamics (MD) simulations of bacterial membranes simplify the membrane by composing it of only 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) or in some cases with1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol (POPG) as well. However, an important constituent of bacterial membranes are lipids with a cyclopropane ring in the acyl chain. We developed a complex membrane that reflects the diverse population of lipids within E. coli cytoplasmic membranes, including cyclic lipids. Differences between the deuterium order profile of cyclic and monounsaturated lipids are observed. Furthermore, inclusion of the ring decreases the surface density of the bilayer and produces a more rigid membrane as compared to POPE/POPG membranes. Additionally, the diverse acyl chain length creates a thinner bilayer which better matches the hydrophobic thickness of E. coli transmembrane proteins. We believe the complex membrane is more accurate and suggest the use of it in MD simulations rather than simple membranes.Item Rewiring Quorum Sensing Circuitry for Recombinant Protein Production in E. coi(2007-08-08) Tsao, Chen-Yu; Bentley, William E.; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The global objective of this research is to rewire the circuitry of bacterial quorum sensing to facilitate recombinant protein production in bacteria. Previous research has shown that the activity of AI-2, the putative "universal" bacterial autoinducer, decreased in culture fluids when several proteins were overexpressed in E. coli W3110, suggesting bacteria communicate or possibly potentiate the "metabolic burden" associated with protein overexpression. Additionally, conditioned medium obtained from LuxS+ and LuxS- strains was added to these cultures, resulting in a 2-4 fold increase in specific yield for both chloramphenicol acetyltransferase (CAT) and organophosphorus hydrolase (OPH). These simple observations set the stage for examining the role of quorum sensing in recombinant protein expression systems and also suggested that "rewiring" the quorum sensing circuitry would lead to significant improvement of yield. In this dissertation, we have inserted luxS into expression vectors (IPTG inducible) which can co-synthesize target recombinant proteins (arabinose inducible) to accomplish the modulation of the metabolic landscape for protein synthesis via altered AI-2 signaling. Our results show significant enhancement in both protein yield and activity, and reveal a strong linkage between bacterial cell communication and cellular processes involved in synthesis and folding of recombinant proteins in E. coli. Second, we have attempted to rewire the native quorum sensing signaling circuitry and couple it to the widely-used T7 expression system for constructing an autoinducible recombinant protein expression platform. We demonstrate, for the first time, true autoinduction of recombinant proteins in E. coli or, in fact, any expression system. That is, our results showed that GFPuv, CAT, and LacZ were all expressed using this innovative system without cell growth monitoring or inducer addition.Item Design And Construction Of Low Power, Portable Photocatalytic Water Treatment Unit Using Light Emitting Diode(2006-05-03) chokshi, mihir k; Davis, Allen P; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Limited availability of mobile technology to disinfect drinking water at low cost led to the current research of using titanium dioxide (TiO2) photocatalysis for drinking water disinfection. New UV light emitting diodes (LEDs) have potential for application in this technology. The research was divided into three parts: immobilization of TiO2, optimization of coating and reactor using methyl orange and investigating disinfection efficiency for Escheriachia coli (ATCC 25922). Thin TiO2 films supplemented with Degussa P25, coated on glass beads and calcinated at 500 oC had 9.9 mm maximum and 2 mm average thickness, 0.28 m2/g BET surface area and was dominated by the anatase TiO2 phase. A reactor with LEDs degraded methyl orange with a first order rate constant of 0.39 hr-1 and 3 log10 E. coli removal was noted in 240 mins. With anticipated drops in LED cost, use of LEDs for TiO2 photocatalysis remains a promising disinfection technology.