University of New Hampshire Scholars' Repository Copyright (c) 2013 University of New Hampshire All rights reserved. http://scholars.unh.edu Recent documents in University of New Hampshire Scholars' Repository en-us Sun, 19 May 2013 01:38:09 PDT 3600 The redox behavior of heme in cystathionine β-synthase is pH dependent http://scholars.unh.edu/chemistry_facpub/22 http://scholars.unh.edu/chemistry_facpub/22 Thu, 16 May 2013 11:41:10 PDT Human cystathionine β-synthase (CBS) is a unique pyridoxal-5‘-phosphate-dependent enzyme in which heme is also present as a cofactor. Because the function of heme in this enzyme has yet to be elucidated, the study presented herein investigated possible relationships between the chemistry of the heme and the strong pH dependence of CBS activity. This study revealed, via study of a truncation variant, that the catalytic core of the enzyme governs the pH dependence of the activity. The heme moiety was found to play no discernible role in regulating CBS enzyme activity by sensing changes in pH, because the coordination sphere of the heme is not altered by changes in pH over a range of pH 6−9. Instead, pH was found to control the equilibrium amount of ferric and ferrous heme present after reaction of CBS with one-electron reducing agents. A variety of spectroscopic techniques, including resonance Raman, magnetic circular dichroism, and electron paramagnetic resonance, demonstrated that at pH 9 Fe(II) CBS is dominant while at pH 6 Fe(III) CBS is favored. At low pH, Fe(II) CBS forms transiently but reoxidizes by an apparent proton-gated electron-transfer mechanism. Regulation of CBS activity by the iron redox state has been proposed as the role of the heme moiety in this enzyme. Given that the redox behavior of the CBS heme appears to be controlled by pH, interplay of pH and oxidation state effects must occur if CBS activity is redox regulated.

]]> Samuel Pazicni et al. The heme of cystathionine b-synthase likely undergoes a temperature-induced redox-mediated ligand switch http://scholars.unh.edu/chemistry_facpub/21 http://scholars.unh.edu/chemistry_facpub/21 Thu, 16 May 2013 11:41:09 PDT Cystathionine β-synthase (CBS) is a pyridoxal-5‘-dependent enzyme that catalyzes the condensation of homocysteine and serine to form cystathionine. Human CBS is unique in that heme is also required for maximal activity, although the function of heme in this enzyme is presently unclear. The study presented herein reveals that the heme of human CBS undergoes a coordination change upon reduction at elevated temperatures. We have termed this new species “CBS424” and demonstrate that its formation is likely irreversible when pH 9 FeIII CBS is reduced at moderately elevated temperatures (40 °C and higher) or when pH 9 FeII CBS is heated to similar temperatures. Spectroscopic techniques, including resonance Raman, electronic absorption, and variable temperature/variable field magnetic circular dichroism spectroscopy, provide strong evidence that CBS424 is coordinated by two neutral donor ligands. It appears likely that the native cysteine(thiolate) heme ligand is displaced by an endogenous neutral donor upon conversion to CBS424. This behavior is consistent with other six-coordinate, cysteine(thiolate)-ligated heme centers, which seek to avoid this coordination structure in the FeII state. Functional assays show that CBS424 is inactive and suggest that the ligand switch is responsible for eliminating enzyme activity. When this investigation is taken together with other functional studies of CBS, it provides strong evidence that coordination of Cys52 to the heme iron is crucial for full activity in this enzyme. We hypothesize that cysteine displacement may serve as a mechanism for CBS inactivation and that second-sphere interactions of the Cys52 thiolate with surrounding residues are responsible for communicating the heme ligand displacement to the CBS active site.

]]> Samuel Pazicni et al. Ferrous human cystathionine b-synthase loses activity during enzyme assay due to a ligand switch process http://scholars.unh.edu/chemistry_facpub/20 http://scholars.unh.edu/chemistry_facpub/20 Thu, 16 May 2013 11:41:07 PDT Cystathionine β-synthase (CBS) is a pyridoxal-5‘-phosphate-dependent enzyme that catalyzes the condensation of serine and homocysteine to form cystathionine. Mammalian CBS also contains a heme cofactor that has been proposed to allosterically regulate enzyme activity via the heme redox state, with FeII CBS displaying approximately half the activity of FeIII CBS in vitro. The results of this study show that human FeII CBS spontaneously loses enzyme activity over the course of a 20 min enzyme assay. Both the full-length 63-kDa and truncated 45-kDa form of CBS slowly and irreversibly lose activity upon reduction to the FeII form. Additionally, electronic absorption spectroscopy reveals that FeII CBS undergoes a heme ligand exchange to FeII CBS424 when the enzyme is incubated at 37 °C and pH 8.6. The addition of enzyme substrates or imidazole has a moderate effect on the rate of the ligand switch, but does not prevent conversion to the inactive species. Time-dependent spectroscopic data describing the conversion of FeII CBS to FeII CBS424 were fitted to a three-state kinetic model. The resultant rate constants were used to fit assay data and to estimate the activity of FeII CBS prior to the ligand switch. Based on this fit it appears that FeII CBS initially has the same enzyme activity as FeIII CBS, but FeII CBS loses activity as the ligand switch proceeds. The slow and irreversible loss of FeII CBS enzyme activity in vitro resembles protein denaturation, and suggests that a simple regulatory mechanism based on the heme redox state is unlikely.

]]> Melisa M. Cherney et al. The interaction of mitochondrial iron with superoxide dismutase http://scholars.unh.edu/chemistry_facpub/19 http://scholars.unh.edu/chemistry_facpub/19 Thu, 16 May 2013 11:41:06 PDT Superoxide dismutase 2 (SOD2) is one of the rare mitochondrial enzymes evolved to use manganese as a cofactor over the more abundant element iron. Although mitochondrial iron does not normally bind SOD2, iron will misincorporate into Saccharomyces cerevisiae Sod2p when cells are starved for manganese or when mitochondrial iron homeostasis is disrupted by mutations in yeast grx5, ssq1, and mtm1. We report here that such changes in mitochondrial manganese and iron similarly affect cofactor selection in a heterologously expressed Escherichia coli Mn-SOD, but not a highly homologous Fe-SOD. By x-ray absorption near edge structure and extended x-ray absorption fine structure analyses of isolated mitochondria, we find that misincorporation of iron into yeast Sod2p does not correlate with significant changes in the average oxidation state or coordination chemistry of bulk mitochondrial iron. Instead, small changes in mitochondrial iron are likely to promote iron-SOD2 interactions. Iron binds Sod2p in yeast mutants blocking late stages of iron-sulfur cluster biogenesis (grx5, ssq1, and atm1), but not in mutants defective in the upstream Isu proteins that serve as scaffolds for iron-sulfur biosynthesis. In fact, we observed a requirement for the Isu proteins in iron inactivation of yeast Sod2p. Sod2p activity was restored in mtm1 and grx5 mutants by depleting cells of Isu proteins or using a dominant negative Isu1p predicted to stabilize iron binding to Isu1p. In all cases where disruptions in iron homeostasis inactivated Sod2p, we observed an increase in mitochondrial Isu proteins. These studies indicate that the Isu proteins and the iron-sulfur pathway can donate iron to Sod2p.

]]> Amornrat Naranuntarat et al. Coencapsulation of arsenic- and platinum-based drugs for targeted cancer treatment http://scholars.unh.edu/chemistry_facpub/18 http://scholars.unh.edu/chemistry_facpub/18 Thu, 16 May 2013 11:41:04 PDT Haimei Chen et al. NMR and XAS reveal an inner-sphere metal binding site in the P4 helix of the metallo-ribozyme ribonuclease P http://scholars.unh.edu/chemistry_facpub/17 http://scholars.unh.edu/chemistry_facpub/17 Thu, 16 May 2013 11:41:03 PDT Functionally critical metals interact with RNA through complex coordination schemes that are currently difficult to visualize at the atomic level under solution conditions. Here, we report a new approach that combines NMR and XAS to resolve and characterize metal binding in the most highly conserved P4 helix of ribonuclease P (RNase P), the ribonucleoprotein that catalyzes the divalent metal ion-dependent maturation of the 5′ end of precursor tRNA. Extended X-ray absorption fine structure (EXAFS) spectroscopy reveals that the Zn2+ bound to a P4 helix mimic is six-coordinate, with an average Zn-O/N bond distance of 2.08 Å. The EXAFS data also show intense outer-shell scattering indicating that the zinc ion has inner-shell interactions with one or more RNA ligands. NMR Mn2+ paramagnetic line broadening experiments reveal strong metal localization at residues corresponding to G378 and G379 in B. subtilis RNase P. A new “metal cocktail” chemical shift perturbation strategy involving titrations with Graphic, Zn2+, and Graphicconfirm an inner-sphere metal interaction with residues G378 and G379. These studies present a unique picture of how metals coordinate to the putative RNase P active site in solution, and shed light on the environment of an essential metal ion in RNase P. Our experimental approach presents a general method for identifying and characterizing inner-sphere metal ion binding sites in RNA in solution.

]]> Kristin S. Koutmou et al. A geometric and electrostatic study of the [4Fe-4S] cluster of adenosine-5´-phosphosulfate reductase from broken symmetry density functional calculations and extended X-ray absorption fine structure spectroscopy http://scholars.unh.edu/chemistry_facpub/16 http://scholars.unh.edu/chemistry_facpub/16 Thu, 16 May 2013 11:41:01 PDT Adenosine-5′-phosphosulfate reductase (APSR) is an iron–sulfur protein that catalyzes the reduction of adenosine-5′-phosphosulfate (APS) to sulfite. APSR coordinates to a [4Fe-4S] cluster via a conserved CC-X80-CXXC motif, and the cluster is essential for catalysis. Despite extensive functional, structural, and spectroscopic studies, the exact role of the iron–sulfur cluster in APS reduction remains unknown. To gain an understanding into the role of the cluster, density functional theory (DFT) analysis and extended X-ray fine structure spectroscopy (EXAFS) have been performed to reveal insights into the coordination, geometry, and electrostatics of the [4Fe-4S] cluster. X-ray absorption near-edge structure (XANES) data confirms that the cluster is in the [4Fe-4S]2+ state in both native and substrate-bound APSR while EXAFS data recorded at 0.1 Å resolution indicates that there is no significant change in the structure of the [4Fe-4S] cluster between the native and substrate-bound forms of the protein. On the other hand, DFT calculations provide an insight into the subtle differences between the geometry of the cluster in the native and APS-bound forms of APSR. A comparison between models with and without the tandem cysteine pair coordination of the cluster suggests a role for the unique coordination in facilitating a compact geometric structure and “fine-tuning” the electronic structure to prevent reduction of the cluster. Further, calculations using models in which residue Lys144 is mutated to Ala confirm the finding that Lys144 serves as a crucial link in the interactions involving the [4Fe-4S] cluster and APS.

]]> Devayani P. Bhave et al. Reponses to Changing Needs in U.S. Doctoral Education http://scholars.unh.edu/chemistry_facpub/15 http://scholars.unh.edu/chemistry_facpub/15 Thu, 16 May 2013 11:40:57 PDT At the National Meeting of the American Chemical Society in Philadelphia on August 23–24, 2004, a Presidential Symposium Event was held titled "Responses to Changing Needs in U.S. Doctoral Education". This article provides a report of this two-day symposium, which featured an overview of the history and development of doctoral education in chemistry in the U.S., a description of social and cultural contexts that are influencing the field, an introduction to the reform projects being undertaken by departments of chemistry that are participating in the Carnegie Initiative on the Doctorate, and some perceptions of doctoral education from current graduate students in chemistry.

]]> Marjorie Caserio et al. Writing-to-teach: A new pedagogical approach to elicit explanative writing in undergraduate chemistry students http://scholars.unh.edu/chemistry_facpub/14 http://scholars.unh.edu/chemistry_facpub/14 Thu, 16 May 2013 11:40:55 PDT Contemporary strategies in STEM education focus on developing pedagogies that more actively engage students in their own learning. A method that has proven effective to this end has been peer instruction and discussion, particularly those in which participating students must organize information in such a way as to be able to verbally articulate it to others. The success of peer learning raises the question of what other communicative activities could lead to similar learning gains. Writing is a reasonable choice for such an activity, as there is strong historical evidence of the value of writing in facilitating student learning. Presented here is “writing-to-teach”; a fusion of writing and peer instruction that is rooted in the theories of meaningful learning and situated cognition as well as research on student-generated explanatory knowledge. Writing-to-teach activities were designed and implemented in an introductory physical chemistry course and evaluated using student surveys. In addition, a novel expert-ranking methodology was employed to evaluate the quality of explanatory writing produced by students engaging in writing-to-teach activities. Lastly, suggestions are given on how writing-to-teach can be implemented more broadly in other STEM classrooms.

]]> Anne V. Vazquez et al. The Next Generation of Entrepreneurs http://scholars.unh.edu/honors/114 http://scholars.unh.edu/honors/114 Mon, 13 May 2013 08:12:13 PDT A.R. (Venky) Venkatachalam, Ph.D. (Associate Dean of Academic Programs & Professor of Information Systems) and I believe that the steps to insure future entrepreneurial success have not been taken; therefore my intention is to provide quality insight regarding the importance of embracing our next generation of entrepreneurs.

]]> Christopher Schwab Reactions of Generation Y to Luxury Hotel Twitter Promotions http://scholars.unh.edu/honors/113 http://scholars.unh.edu/honors/113 Mon, 13 May 2013 08:07:08 PDT Social media refers to the means of interactions among people in which they create, share, and exchange information and ideas in virtual communities and networks (Merriam-Webster, 2013). Social media marketing refers to the process of gaining website traffic or attention through social media sites (Evans, 2008). In today’s society, social media refers mainly to websites including (but not limited to) Facebook, Twitter, LinkedIn, and Google+. The most popular and fastest growing of these social media venues is Twitter. Twitter was founded in 2006 by Jack Dorsey, Evan Williams, and Biz Stone. Since 2006, almost 200 million users across the globe have joined the site; over 140 million tweets are “tweeted” daily (Picard, 2011). Twitter took advantage of a niche in the market, allowing 140 characters to express an idea or emotion. Twitter has changed the media world as a news source, tweeting real-time information from stories that arise (Picard, 2011). In the lodging industry, methods of social media to promote hotels are becoming more popular. Twitter, in particular, has emerged as a “moment of truth” for a hotel, demonstrating how instantly and tactfully hotels react to the thoughts and opinions of former, current, and potential guests. Studies have also suggested that “online social life mirrors offline relationships in many ways” (Moore, p. 440). Therefore, Twitter accounts should be viewed as an extension of the hospitality business, in particular lodging, echoing the relationship a customer would feel upon arrival to the hotel.

Hotel marketing teams have reached “great success by driving demand to hotels through increased online advertising and web optimization” (Chipkin, 2013). This has increased overall customer views of the hotel without affecting the rate strategy of the property or brand. Twitter presence could, potentially, help a patron decide between two hotels, “If a promotion, experience or package is unique, it definitely works to generate bookings and helps put you first in a consumer’s mind when they are choosing between two or three hotels,” says Rachel Harrison of Hyatt Andaz (Chipkin, 2013).

Hotel companies worldwide are investing in their social media networks. Certain hotels (i.e. W Barcelona) are even hiring social media and marketing managers whose responsibilities include instant Twitter feedback (Appendix 1). The purpose behind this investment is to maximize these social media accounts, creating feedback from all potential guests, allowing them to react to both positive and negative word of mouth. Social media managers have recently encountered an opportunity; Generation Y is becoming a target demographic. As Generation Y enters the workforce and begins a career, the exposure to hotel brands and types will increase. Luxury hotel stays are becoming more financially reachable to these Generation Y guests because of their career advancements (Fields, 2013). This study will serve to evaluate the added benefits from the adoption of social media channels, particularly Twitter.

]]> Katherine M. Woods What are the relations among stress perception, health perception and activity participation in school-aged children? http://scholars.unh.edu/honors/112 http://scholars.unh.edu/honors/112 Mon, 13 May 2013 08:07:06 PDT This correlational study examined possible relations among children’s activity patterns, perceived stress, and perceived health. A variety of self-report questionnaires were administered to a sample of 33 school age children. The Pediatric Activity Sort (PACS) was used to measure activity participation, a health questionnaire was used to assess health, and the Childhood Stress Questionnaire (CSQ) was used to measure perceived stress. Correlations showed no significant relationships between stress level and the amount of reported activity participation. The absence of significant relationships may be due to testing a sample of middle to upper class, Caucasian children, as there was a skewed CSQ dispersion with the majority of children reporting less stress than expected.

]]> Allison Caplin Sensitivity Analysis of a Proposed Model for Removal Efficiency of Trihalomethanes (THMs) Using Spray Aeration http://scholars.unh.edu/honors/111 http://scholars.unh.edu/honors/111 Mon, 13 May 2013 08:07:05 PDT Trihalomethanes (THMs) form in drinking water treatment systems as a byproduct of chlorination and are problematic from a public health perspective due to their carcinogenic potential and their potential for additional formation throughout distribution systems. Recently, regulations have tightened on THMs in an attempt to reduce the risk of exposure for consumers at the far ends of distribution systems. Due to widespread use of chlorine and the reluctance of drinking water providers to overhaul current treatment systems, research has been undertaken to investigate post-treatment removal of THMs. One such method is spray aeration, whereby water is recycled in water storage tanks by spraying it through showerheads. Using a spray aeration model and a simple sensitivity analysis, the following study evaluates the influence of various parameters on the model’s output. It was determined that the configuration and magnitude of the recycle flow were the most influential parameters, while spray angle and the distribution of THM species (speciation) were the least influential. These results are important for practitioners as they can help them to determine the most important design parameters for spray aeration systems. Additionally, the following study elucidates the advantages of spray aeration in the removal of brominated THM species.

]]> Aidan Cecchetti The Quest for Alternatives to U.S. Education Reform http://scholars.unh.edu/honors/110 http://scholars.unh.edu/honors/110 Mon, 13 May 2013 08:07:04 PDT William B. Dyke Investing In Sustainability: Making Portsmouth, New Hampshire a Sustainable City http://scholars.unh.edu/honors/109 http://scholars.unh.edu/honors/109 Mon, 13 May 2013 08:07:02 PDT David Freeman Married Coal Gasification and Biomass Pyrolysis http://scholars.unh.edu/honors/108 http://scholars.unh.edu/honors/108 Mon, 13 May 2013 08:07:01 PDT This project is a proposal to marry a coal gasification process to a biomass pyrolysis. Coal is pyrolized to produce syngas and a large amount of heat. The syngas is treated and fed to a Fischer-Tropsch process. The excess heat produces steam that is used to pyrolize biomass. The biomass produces char, gas, and vapor. The char and gas are recovered, and the vapor is condensed to produce bio-oil.

The proposed plant has a capacity of 1100 tons of biomass (550 dry tons) per day. I assumed an operating factor of 0.9 The plant could be operational within five years, with approximately three years of construction and a year operating at lowered capacity. However, significant research is needed to confirm and optimize certain aspects of the process.

The process has some sections at high temperatures and moderately high pressures. Certain units will be constructed of special materials to withstand the temperatures. Safety features will also be installed which will prevent temperatures from elevating beyond normal operating levels. A strong basic solution is also used to strip CO2 from process gases. These units will be constructed of stainless steel for structural integrity. Finally, highly combustible products are used in the process. Safe storage of these materials and strict fire safety provisions will be established to minimize the risks of fire or explosion. Safety considerations affected the capital cost of the plant because of the special materials required for safe construction.

The process does not have many environmental concerns. The gases produced by gasification and pyrolysis are collected as a byproduct to be used in a Fischer-Tropsch process. The disposal of liquid and solid waste is more of a concern. Solid slag can be disposed of in a landfill. Some liquid waste contains slag and ash and can be filtered. Other liquid waste has bio-oil contamination which is more expensive to remove. I made the assumption that this waste stream would need secondary treatment, which is fairly expensive and is a large contribution to the overall costs.

The total capital cost of the plant is around $30 million. For a chemical plant, this is not very large. The capital cost has a very minor effect on the production costs. To run the equipment, the plant will employ 45 process engineers, with 5 shifts of 9 operators.

Bio-oil can be produced for $1.77 per kilogram. Estimates for bio-oil produced from an unmarried process are hard to find, and have not been scaled to a current value. They range from $0.09 to $0.50 per kilogram. The large disparity between my price and the literature values is mostly due to the high cost of disposing water contaminated with bio-oil.

I recommend proceeding with research on ways to lower the operating costs. Specifically, if water contaminated with bio-oil can be disposed of with primary treatment rather than secondary treatment, the cost of production is lowered by $1.47 per kilogram, to $0.30 per kilogram. Lowering waste treatment costs will make the plant highly competitive with unmarried designs. Further research should also be conducted into other process parameters, such as the effectiveness of NaOH stripping, a novel technique I used to lower treatment costs.

]]> Michael Balch Justice across the Hemispheres: The effect of the Pinochet arrest on domestic courts in Chile and Spain http://scholars.unh.edu/honors/107 http://scholars.unh.edu/honors/107 Mon, 13 May 2013 08:07:00 PDT This study examines whether the 1998 arrest, by order of a Spanish judge, of former Chilean President Augusto Pinochet in London for crimes of genocide and terrorism impacted the attitude of Chilean and Spanish courts toward prosecuting their own country’s human rights violations. It argues that after 1998 Chile’s judiciary increased prosecutions against former regime officials, while the Spanish judiciary upheld Spain’s 1977 Amnesty Law and declined to participate in the national discourse on the country’s past human rights violations. This research includes a comparative case study of Chile and Spain, their recent histories, their judiciaries’ attitudes towards prosecution of human rights violations before and after the Pinochet arrest, as well as an overview of the Pinochet arrest itself.

]]> Audrey A. Hansen Comparison of Biomass to Bio-oils Reactor Systems: Direct Conversion vs. Companion Coal Gasification http://scholars.unh.edu/honors/106 http://scholars.unh.edu/honors/106 Mon, 13 May 2013 08:06:58 PDT It is well known that the United States’ dependence on crude-oil negatively affects its economy, safety, and environment. To alleviate these negative consequences, a more economical and environmentally-friendly source of fuel, such as biomass, should be explored. The conversion of biomass to bio-oils involves the pyrolysis of biomass at about 500°C, thus requiring a great deal of heat. This heat source could be the excess waste heat from a coal gasifier.

As such, this report specifies the design of an industrial plant that produces bio-oils from biomass by using the waste heat from a coal gasifier. It is designed to produce 2.24×108 kg/yr of bio-oil that can be sold at $0.79/kg. This plant involves coal and biomass solids handling, a coal gasification reactor, a biomass pyrolysis reactor, and a series of separation units to remove waste products from the syngas and isolate the bio-oil. The syngas contains methane, hydrogen, and carbon monoxide and is sold as a by-product credit. The plant is expected to run on feeds of 1.5x1011 kg/yr of coal and 5.4 x108 kg/yr of raw biomass.

The coal gasification reactor was sized based on the heating duty of steam at 273000 kJ/s and the biomass pyrolysis reactor was sized based on a heating duty of 7026 kJ/s. The plant’s operating factor (POF) is 0.9 at 7884 hrs/yr running 24 hrs/day and 328.5 days/yr. The total bare module equipment cost, including all pumps, heat exchangers, grinders, separators, absorber, and reactors is $93 million. The total capital investment of the plant is $173 million. The DCFRR and NRR are 12.59% and 20% respectively.

Given that selling price of bio-oil ($0.79/kg) associated with this plant is about six times more expensive that the average cost of bio-oil ($0.13/kg), it is not recommended that a Class – 1 Estimate be conducted. Before a Class – 1 Estimate can be conducted, the unnecessary costs associated with this proposed plant must be addressed and reduced. Specific attention must be paid to the following two heat exchangers, E-127 and E-129. Additionally, attention should be given to discover a cheaper source of industrial, liquid oxygen.

]]> Alexandra Eicher The Use of Twitter by Luxury and Midscale Hotels http://scholars.unh.edu/honors/105 http://scholars.unh.edu/honors/105 Mon, 13 May 2013 07:42:24 PDT Twitter has demanded a presence in company brands since its start up in 2008, including the hotel industry. As an up and coming marketing tool, the social media website is still new to both hotels and their guests. Observing the different strategies incorporated by luxury and midscale hotels, the paper provides explanations on how these two segments differ in utilizing Twitter. Through direct interviews with US luxury and midscale hotels and analyzing individual Twitter feeds, it was found that luxury hotels and their target market are much more active on Twitter than the midscale hotel segment. Implications suggest that although there is no current expectation from midscale hotel travelers to follow a Twitter feed, the rising presence of Twitter will demand midscale hotels to actively participate on the social media site in the near future.

]]> Yolanda M. Tselepidakis A Morphological Study of Drug Brand Names http://scholars.unh.edu/honors/104 http://scholars.unh.edu/honors/104 Mon, 13 May 2013 07:42:23 PDT Celina M. Williamson