1,003 research outputs found
Protein dynamics in minimyoglobin: is the central core of myoglobin the conformational domain?
No full textThe kinetics of CO binding to the horse myoglobin fragment Mb-(32-139), the so-called "mini-Mb," were investigated by laser flash photolysis in 0.1 M phosphate buffer and in buffer with 75\% (vol/vol) glycerol. The reaction displays complex time courses that can be approximated satisfactorily only with a sum of five exponentials. The features of the kinetic components and a comparison of the deoxy-minus-carbonyl difference spectra of mini-Mb and horse Mb obtained under equilibrium conditions, with the kinetic difference spectra resulting from the global analysis of the traces recorded between 400 and 450 nm, show that CO binding to mini-Mb is accompanied by large structural changes. In view of the fact that mini-Mb is an approximation of the Mb-(31-105) fragment encoded by the central exon of the Mb gene, this finding is particularly relevant. On the basis of our data and previous reports [De Sanctis, G., Falcioni, G., Giardina, B., Ascoli, F. & Brunori, M. (1988) J. Mol. Biol. 200, 725-733; De Sanctis, G., Falcioni, G., Grelloni, F., Desideri, A., Polizo, F., Giardina, B., Ascoli, F. & Brunori, M. (1992) J. Mol. Biol. 222, 637-643], we propose that the protein fragment encoded by the central exon of the Mb gene is the domain responsible for ligand-linked conformational transitions, while the two terminal fragments dampen the amplitude of the structural changes that accompany ligand binding, thus rendering the protein stable and kinetically more efficient in its physiological function
Nitrosylation of c heme in cd(1)-nitrite reductase is enhanced during catalysis
No full textThe reduction of nitrite into nitric oxide (NO) in denitrifying bacteria is catalyzed by nitrite reductase. In several species, this enzyme is a heme-containing protein with one c heme and one d(1) heme per mono-mer (cd(1)NiR), encoded by the nirS gene.
For many years, the evidence of a link between NO and this hemeprotein represented a paradox, given that NO was known to tightly bind and, possibly, inhibit hemeproteins, including cd(1)NiRs.
It is now established that, during catalysis, cd(1)NiRs diverge from "canonical" hemeproteins, since the product NO rapidly dissociates from the ferrous d(1) heme, which, in turn, displays a peculiar "low" affinity for NO (K-D = 0.11 microM at pH 7.0).
It has been also previously shown that the c heme reacts with NO at acidic pH but c heme nitrosylation was not extensively investigated, given that in cd(1)NiR it was considered a side reaction, rather than a genuine process controlling catalysis.
The spectroscopic study of the reaction of cd(1)NiR and its semi-apo derivative (containing the sole c heme) with NO reported here shows that c heme nitrosylation is enhanced during catalysis; this evidence has been discussed in order to assess the potential of c heme nitrosylation as a regulatory process, as observed for cytochrome c nitrosylation in mammalian mitochondria
Assessment of radioactivity in commercially available honey in Italy
No full textActivity concentration of natural radionuclides and 137Cs were estimated in 28 honeys purchased from large supermarket chains in Italy. Uranium, polonium and thorium were measured by alpha spectrometry, 40 K and 137Cs by gamma spectrometry and 226Ra by liquid scintillation. The concentrations were 50.6 ± 46.3, 0.023 ± 0.010, 0.019 ± 0.017, 0.27 ± 0.40 Bqkg−1 for 40 K, 238U, 234U and 210Po respectively. 235U, 228Th, 232Th were consistently <0.007 Bqkg−1 and 226Ra <0.200 Bqkg−1. 137Cs was <2.1 Bqkg−1 in 93% of the samples. The activity of radiocesium was found to be above the minimum detectable level in only two samples and did not exceed the highest permitted level for food contributing to the overall radioactivity only slightly. The effective doses attributable to 210Po accounts for 0.0026–5.31% of global human exposure to natural radiation. The honeys that were tested were found to be of good quality with regard to the parameters under study, confirming the general image of honey as a genuine healthy product
Talk the Talk, Walk the Walk: Defining Critical Race Theory in Research
No full textThis paper focuses on what constitutes a Critical Race Theory (CRT) methodology. Over the last decade there has been a noticeable growth in published works citing CRT in the UK. This has led to an increase in practical research projects utilising CRT as their framework. It is clear that research on ‘race’ is an emerging topic of study recently encapsulated by the work of Seidman (2004), Bulmer and Solomos (2004), Gunaratnam (2003), Denzin and Giardina (2006; 2007), Tuhiwai Smith (2006), and Denzin, Lincoln and TuhiwaiSmith (2008). What is less visible is a debate on how CRT is positioned in relation to the ‘nexus of methodic practice, substantive theory and epistemological underpinnings that is a methodology (Harvey 1990:1). These philosophical, ethical, and practical questions are initially considered here by examining the notions of ontology, epistemology and methodology before practical considerations of recognising, framing and applying CRT research methodologies are explored
Youth Culture and Sport: Identity, Power, and Politics
No full textYouth Culture and Sport: Identity, Power, and Politics Michael D. Giardina & Michele K. Donnelly (red) Abingdon, Oxon: Routledge, 2008 http://www.idrottsforum.org/reviews/items08/frakri_giardina-donnelly.html</p
Youth Culture and Sport: Identity, Power, and Politics
No full textYouth Culture and Sport: Identity, Power, and Politics Michael D. Giardina & Michele K. Donnelly (red) Abingdon, Oxon: Routledge, 2008 http://www.idrottsforum.org/reviews/items08/frakri_giardina-donnelly.htm
Recombinant expression of Pleurotus ostreatus laccases in Kluyveromyces lactis and Saccharomyces cerevisiae
No full textHeterologous expression of Pleurotus ostreatus POXC and POXA1b laccases in two yeasts, Kluyveromyces lactis and Saccharomyces cerevisiae, was performed. Both transformed hosts secreted recombinant active laccases, although K. lactis was much more effective than S. cerevisiae. rPOXA1b transformants always had higher secreted activity than rPOXC transformants did. The lower tendency of K. lactis with respect to S. cerevisiae to hyperglycosylate recombinant proteins was confirmed. Recombinant laccases from K. lactis were purified and characterised. Specific activities of native and recombinant POXA1b are similar. On the other hand, rPOXC specific activity is much lower than that of the native protein, perhaps due to incomplete or incorrect folding. Both recombinant laccase signal peptides were correctly cleaved, with rPOXA1b protein having two C-terminal amino acids removed. The availability of the established recombinant expression system provides better understanding of laccase structure-function relationships and allows the development of new oxidative catalysts through molecular evolution techniques
Efficiency, products and mechanisms of ethyl acetate oxidative degradation in air non-thermal plasma
No full textEthyl acetate (EA) is a popular solvent and diluent in many products and one of the most ubiquitous organic pollutants of indoor air. Although EA's ascertained toxicity is classified as low, exposure to its vapors at concentrations 400 ppm causes serious problems in humans. EA is thus a frequent target in testing novel technologies for air purification. We report here an investigation of EA oxidative degradation in air at room temperature and atmospheric pressure induced by corona discharges. Three corona regimes, dc-, dc+ and pulsed +, were tested in the same reactor under various experimental conditions with regard to EA initial concentration (C 0) and the presence of humidity in the system. The EA degradation process was monitored by gas chromatography (GC)-flame ionization detection, GC-mass spectrometry and Fourier transform infrared spectroscopy analysis of the treated gas. These analyses yielded the concentration of residual EA (C) and those of its major products of oxidation (CO2, CO) and revealed a few organic reaction intermediates formed along the oxidation chain. The process energy efficiency was determined as energy constant, k E (kJ-1 l) and as energy yield, EY (g kW-1 h-1). The efficiency depends on the type of corona (pulsed + >dc- >dc+), on the presence of humidity in the air (improvement in the case of dc-, little or no effect for dc+) and on C 0 (k E increases linearly with 1/C 0). CO2 and CO were the major carbon containing products, confirming the strong oxidizing power of air non-thermal plasma. Acetic acid and acetaldehyde were detected in very small amounts as reaction intermediates. The experimental results obtained in this work support the conclusion that different reactive species are involved in the initial step of EA oxidation in the case of dc- and dc+ corona air non-thermal plasma
Interviewing and the production of the conversational self
No full textThe author argues that conventional humanist qualitative inquiry took up both paths Foucault identified logical positivism and structuralism as well as theories and practices that emerged from the interpretive and critical turns in the social sciences. Students who may have read deeply in those theories may well experience a disconnect between a theory's assumptions and those that structure conventional humanist qualitative inquiry. But that truth and that real are chimeras, fictions, and neither can ever be outside human being but can only ever be human being the contingent, chaotic, impoverished limit of our imaginations and practices. Subjectivity implies the ongoing construction of human being, human being in flux, in processat every moment being disciplined, regulated, normalized, produced and at the same time, resisting, shifting, changing, and producing. Qualitative researchers use the two face-to-face methods to go deep, to interview repeatedly in order to get closer and closer to the center, the core of participants' being.</p
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