Superoxide dismutases, catalases, and peroxidases are ubiquitous among aerobic and aerotolerant organisms, suggesting that their substrates, superoxide and hydrogen peroxide, are inevitable toxic by-products of aerobic metabolism (1, 2). Considerable progress has been made in identifying the mechanisms by which these species damage cells (2-11). In aerobic environments, mutant organisms that cannot scavenge endogenous O 2. and H 2 O 2 typically grow poorly or die, indicating that these species are formed in potentially toxic doses inside living cells (12, 13). Similar toxicity occurs in wild-type organisms when they are exposed to higher-than-usual levels of oxygen, evidently because these species are formed at elevated rates. Despite this progress, the mechanisms of O 2 . and H 2 O 2 formation are less well understood. Molecular oxygen is a triplet species that can only accept electrons one at a time from potential donors (14). This restriction ensures that oxygen does not spontaneously oxidize most reduced biomolecules, such as NAD(P)H, which are obligate two-electron donors. Instead, enzymes that are competent univalent electron donors are the most likely effectors of inadvertent oxygen reduction. Such enzymes are prominent in electron transport chains. Accordingly, studies in Escherichia coli determined that NADH dehydrogenase II, succinate dehydrogenase, sulfite reductase, and fumarate reductase each formed O 2. and H 2 O 2 when the reduced enzymes were exposed to oxygen (15, 16). These autoxidizing enzymes contain flavins and either iron-sulfur clusters or quinones, all of which are competent at univalent redox reactions. However, in each case the flavin appeared to be the primary site of electron transfer to oxygen. This trend has been noted in other autoxidizing enzymes as well. This may be due to the solvent accessibility of the flavins, which are situated at the protein surface in order to interact with soluble substrates. In contrast, the iron-sulfur clusters are typically buried within polypeptide, and quinones may be sequestered in hydrophobic regions of the proteinmembrane interface where O 2 . formation is disfavored. Interestingly, the rates at which flavoenzymes leak electrons to oxygen vary over several orders of magnitude (15,(17)(18)(19), indicating that additional factors must govern turnover number. We are hopeful that some of these factors might be revealed by study of members of the succinate dehydrogenase/ fumarate reductase family (Fig. 1). These enzymes are structurally and functionally similar to one another (20 -22), and each autoxidizes, albeit at different rates. Succinate dehydrogenase (Sdh), 1 a primary respiratory dehydrogenase, catalyzes electron transfer from succinate to membrane-bound quinone. Fumarate reductase (Frd) catalyzes the opposite reaction in its service as a terminal oxidase during the anaerobic growth of some bacteria and eukarya. The physical structure of the E. coli fumarate reductase has been determined (23), and the pathways of electron movement through both ...

؊1 by autoxidation of its reduced FAD cofactor. Sulfite reductase is a second autoxidizable electron transport chain of E. coli, containing FAD, FMN, [4Fe-4S], and siroheme moieties. Purified flavoprotein that contained only the FAD and FMN cofactors had about the same oxidation turnover number as did the holoenzyme, 7 min ؊1 FAD ؊1 . Oxidase activity was largely lost upon FMN removal. Thus the autoxidation of sulfite reductase, like that of the respiratory chain, occurs primarily by autoxidation of an exposed flavin cofactor. Great variability in the oxidation turnover numbers of these and other flavoproteins suggests that endogenous oxidants will be predominantly formed by only a few oxidizable enzymes. Thus the degree of oxidative stress in a cell may depend upon the titer of such enzymes and accordingly may vary with growth conditions and among different cell types. Furthermore, the chemical nature of these reactions was manifested by their acceleration at high temperatures and oxygen concentrations. Thus these environmental parameters may also directly affect the O 2 . and H 2 O 2 loads that organisms must bear.The discovery of superoxide dismutase (SOD) 1 in 1969 (1) was the first indication that aerobic organisms are threatened by superoxide (O 2 . ). SOD catalyzes the dismutation of superoxide (Reaction 1) and, in combination with catalase (Reaction 2), helps clear the cell of reactive oxygen species.SOD was found to be virtually ubiquitous among aerobic organisms, suggesting that O 2 . might be an unavoidable by-product of metabolism in air. This idea was extended to develop the hypothesis that oxygen toxicity might be generally mediated by intracellular O 2 . (2). The molecular details that underpin this idea (the intracellular sources and targets of O 2 . ) were unresolved.Within the past 10 years many details of oxygen toxicity have been revealed. In 1986 Carlioz and Touati (3) reported the properties of a mutant strain of Escherichia coli that lacked both of its cytosolic isozymes of SOD. The mutant grew normally in the absence of oxygen; however, in aerobic medium it exhibited requirements for branched chain, aromatic, and sulfurous amino acids, an inability to grow on non-fermentable carbon sources, and a high rate of spontaneous mutagenesis (4). These same traits were elicited when SOD-proficient wildtype strains were exposed to hyperbaric oxygen (5), suggesting that in these conditions O 2 . formation must be accelerated enough to overwhelm the cellular defenses. Therefore these observations supported the original model of oxygen toxicity. The root cause of the branched chain auxotrophy was tracked to the ability of O 2 . to inactivate dihydroxy-acid dehydratase, an enzyme midway in this pathway (6). O 2 . does so by oxidizing and destabilizing the [4Fe-4S] cluster that acts as a Lewis acid during catalysis (7,8). Iron dissociates from the oxidized cluster, causing a complete loss of activity. The requirement for fermentable carbon sources apparently stems from similar damage to aconitase and ...

Q methodology was used to determine attitudes and opinions about ebooks among a group of faculty, graduate students, and undergraduates at Miami University of Ohio. Oral interviews formed the basis for a collection of opinion statements concerning e-books versus print. These statements were then ranked by a second group of research participants. Factor analysis of these rankings found four distinct factors that reveal clusters of opinions on e-books: Book Lovers, Technophiles, Pragmatists, and Printers. Two of the four factors take a more ideological approach in their understanding of e-books: Book Lovers have an emotional attachment to the printed book as an object, while Technophiles feel just as strongly about technology. In contrast, the other two factors are more utilitarian: Printers might find e-books more palatable if usability were improved, while Pragmatists are comfortable with both print and e-book formats.cademic libraries of all types and sizes have increasingly adopted electronic books (ebooks). This shift in collection development has not been without controversy, however. Research shows that many library patrons resist e-books. The present study will examine user attitudes about e-books to better understand the source of this resistance. To accomplish this task, we employed Q methodology, a research technique that combines qualitative and quantitative methods to analyze subjects' attitudes about a given topic. Using this method, we isolated four distinct opinions about e-books: Book Lovers, Technophiles, Pragmatists, and Printers. We believe that a better understanding about library patrons' beliefs can inform decisions relating to e-books, which are becoming a major part of our collection. Additionally, the components of constituents' reluctance related to ebook usage can guide the transition to electronic texts; everything from types of texts most suited to e-books to selecting specific technologies and interfaces can be shaped by this additional knowledge. Library instruction and outreach related to this potentially large change in our colcrl-108rl

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Q-methodology was used to identify clusters of opinions about e-books at Miami University. The research identified four distinct opinion types among those investigated: Book Lovers, Technophiles, Pragmatists, and Printers. The initial Q-methodology study results were then used as a basis for a large-n survey of undergraduates, graduate students, and faculty so that we could have a more complete picture of the demographic and social makeup of the campus population. Results from that survey indicate that academic discipline is strongly associated with the respondents' opinion types. Gender and educational status are also associated with respondents' opinion types. s academic libraries ramp up their investments in e-book collections and experiment with a growing range of purchasing models, they need to know more about how their users view e-books and what expectations users bring to library collections. In 2007-2008, our research team conducted a study using Q-methodology to identify opinions about e-books among the population of library users at Miami University in Oxford, Ohio. 1 Q-methodology is a well-established research method used to study people's subjectivity (or, put differently: how people think about a topic).2 Typically, a Q-study involves a few basic steps. After opinion statements are collected about a topic of interest, subjects are asked to rank them on a positive-to-negative scale, a process