Characterization of Alkali Induced Formation of Lanthionine, Trisulfides, and Tetrasulfides from Peptide Disulfides using Negative Ion Mass Spectrometry

Peptide disulfides are unstable under alkaline conditions, resulting in the formation of products containing lanthionine and polysulfied linkages. Electrospray ionization mass spectrometry has been used to characterize major species obtained when cyclic and acyclic peptide disulfides are exposed to alkaline media. Studies on a model cyclic peptide disulfide (Boc - Cys - Pro - Leu - Cys - NHMe) and an acyclic peptide, oxidized glutathione, bis ((gamma)Glu Cys - Gly - COOH), are described. Disulfide cleavage reactions are initiated by the abstraction of (CH)-H-alpha or (CH)-H-beta protons of Cys residues, with Subsequent elimination of H2S or H2S2. The buildup of reactive thiol species which act on intermediates containing dehydroalanine residues, rationalizes the formation of lanthionine and polysulfide products. In the case of the cyclic peptide disulfide, the formation of cyclic products is facilitated by the intramolecular nature of the Michael addition reaction of thiols to the dehydroalanine residue. Mass spectral evidence for the intermediate species is presented by using alkylation of thiol groups as a trapping method. Mass spectral fragmentation in the negative ion mode of the peptides derived from trisulfides and tetrasulfides results in elimination of S-2. (J Am Soc Mass Spectrom 2009, 20, 783-791) (C) 2009 American Society for Mass Spectrometry.

Characterization of Alkali Induced Formation of Lanthionine, Trisulfides, and Tetrasulfides from Peptide Disulfides using Negative Ion Mass Spectrometry

Peptide disulfides are unstable under alkaline conditions, resulting in the formation of products containing lanthionine and polysulfied linkages. Electrospray ionization mass spectrometry has been used to characterize major species obtained when cyclic and acyclic peptide disulfides are exposed to alkaline media. Studies on a model cyclic peptide disulfide (Boc - Cys - Pro - Leu - Cys - NHMe) and an acyclic peptide, oxidized glutathione, bis ((gamma)Glu Cys - Gly - COOH), are described. Disulfide cleavage reactions are initiated by the abstraction of (CH)-H-alpha or (CH)-H-beta protons of Cys residues, with Subsequent elimination of H2S or H2S2. The buildup of reactive thiol species which act on intermediates containing dehydroalanine residues, rationalizes the formation of lanthionine and polysulfide products. In the case of the cyclic peptide disulfide, the formation of cyclic products is facilitated by the intramolecular nature of the Michael addition reaction of thiols to the dehydroalanine residue. Mass spectral evidence for the intermediate species is presented by using alkylation of thiol groups as a trapping method. Mass spectral fragmentation in the negative ion mode of the peptides derived from trisulfides and tetrasulfides results in elimination of S-2. (J Am Soc Mass Spectrom 2009, 20, 783-791) (C) 2009 American Society for Mass Spectrometry.

Global capitalism meets national spirit: Discourses in media texts on a cross-border acquisition

In this article, the authors explore media coverage of a recent acquisition across national borders. Their starting point is that the media represent a key arena of “discursive strategizing” for actors such as corporate managers. They illustrate and specify how global capitalism, as discourse relying on economic and financial rationale and exemplified here by the acquiring firm’s attempts to expand, meets national spirit, exemplified here by the complexity in selling the acquisition target to foreigners. The main contribution of this study lies in identifying how key actors draw on and mobilize rationalistic and nationalistic discourses in public discussion. The analysis illustrates that the same actors can draw on different—even contradictory—discourses at different points in time. Furthermore, different actors—even with opposing objectives—may draw on the same discourse in legitimizing their positions and pursuing specific ends.

Natural Convection on a Horizontal Cone in a Porous Medium with Non-Uniform Wall Temperature/Concentration or Heat/Mass Flux and Suction/Injection

The steady natural convection flow on a horizontal cone embedded in a saturated porous medium with non-uniform wall temperature/concentration or heat/mass flux and suction/injection has been investigated. Non-similar solutions have been obtained. The nonlinear couple differential equations under boundary layer approximations governing the flow have been numerically solved. The Nusselt and Sherwood numbers are found to depend on the buoyancy forces, suction/injection rates, variation of wall temperature/concentration or heat/mass flux, Lewis number and the non-Darcy parameter.

Non-darcy double-diffusive mixed convection from heated vertical and horizontal plates in saturated porous media

The non-darcy mixed convection flows from heated vertical and horizontal plates in saturated porous media have been considered using boundary layer approximations. The flows are considered to be driven by multiple buoyancy forces. The similarity solutions for both vertical and horizontal plates have been obtained. The governing equations have been solved numerically using a shooting method. The heat transfer, mass transfer and skin friction are reduced due to inertial forces. Also, they increase with the buoyancy parameter for aiding flow and decrease for the opposing flow. For aiding flow, the heat and mass transfer coefficients are found to approach asymptotically the forced or free convection values as the buoyancy parameter approaches zero or infinity.

On the Discursive Construction of Corruption: A Critical Analysis of Media Texts

While extant studies have greatly advanced our understanding of corruption, we still know little of the processes through which specific practices or events come to be labeled as corruption. In a time when public attention devoted to corruption and other forms of corporate misbehavior has exploded, this thesis raises – and seeks to answer – crucial questions related to how the phenomenon is socially and discursively constructed. What kinds of struggles are manifested in public disputes about corruption? How do constructions of corruption relate with broader conceptions of (il)legitimacy in and around organizations? What are the discursive dynamics involved in the emergence and evolution of corruption scandals? The thesis consists of four essays that each employ different research designs and tackle these questions in slightly different theoretical and methodological ways. The empirical focus is on the media coverage of a number of significant and widely discussed scandals in Norway in the period 2003-2008. By illuminating crucial processes through which conceptions of corruption were constructed, reproduced, and transformed in these scandals, the thesis seeks to paint a more nuanced picture of corruption than what is currently offered in the literature. In particular, the thesis challenges traditional conceptions of corruption as a dysfunctional feature of organizations in and of itself by emphasizing the ambiguous, temporal, context-specific, and at times even contradictory features of corruption in public discussions.

Flat rotation curves: A result of the helical inverse cascade in turbulent media

We have modeled the rotation curves of 21 galaxies observed by Amram et al. (1992), by combining the effects of rigid rotation, gravity, and turbulence. The main motivation behind such modeling is to study the formation of coherent structures in turbulent media and explore its role in the large-scale structures of the universe. The values of the parameters such as mass, turbulent velocity, and angular velocity derived from the rotation curve fits are in good agreement with those derived from the prevalent models.

Exploring sand and bentonite - enhanced sand as filter media for nitrate removal

Increasing nitrate concentrations in ground water is deleterious to human health as ingestion of such water can cause methemoglobinemia in infants and even cancer in adults (desirable limit for nitrate as NO3 - 45 mg/L, IS code 10500-1991). Excess nitrate concentrations in ground water is contributed by reason being disposal of sewage and excessive use of fertilizers. Though numerous technologies such as reverse osmosis, ion exchange, electro-dialysis, permeable reactive barriers using zerovalent iron etc exists, nitrate removal continues to be one of challenging issue as nitrate ion is highly mobile within the soil strata. The tapping the denitrification potential of soil denitrifiers which are inherently available in the soil matrix is the most sustainable approach to mitigate accumulation of nitrate in ground water. The insitu denitrification of sand and bentonite enhanced sand (bentonite content = 5%) in presence of easily assimilable organic carbon such as ethanol was studied. Batch studies showed that nitrate reduction by sand follows first order kinetics with a rate constant 5.3x10(-2) hr(-1) and rate constant 4.3 x 10(-2) hr(-1) was obtained for bentonite-enhanced sand (BS) at 25 degrees C. Filter columns (height = 5 cm and diameter = 8.2 cm) were constructed using sand and bentonite-enhanced sand as filter media. The filtration rate through both the filter columns was maintained at average value of 2.60 cm/h. The nitrate removal rates through both the filter media was assessed for solution containing 22.6 mg NO3-N/L concentrations while keeping C/N mass ratio as 3. For sand filter column, the nitrate removal efficiency reached the average value of 97.6% after passing 50 pore volumes of the nitrate solution. For bentonite-enhanced sand filter column, the average nitrate removal efficiency was 83.5%. The time required for effective operation for sand filter bed was 100 hours, while bentonite-enhanced sand filter bed did not require any maturation period as that of sand filter bed for effective performance because the presence of micropores in bentonite increases the hydraulic retention time of the solution inside the filter bed.

Calidad de la dieta, sobrepeso y obesidad en estudiantes universitarios

Este trabajo se encuentra bajo la licencia Creative Commons Attribution 3.0.

A Mídia e o MST: heróis e vilões na trama do discurso jornalístico

A presente pesquisa visa refletir, sob a ótica do discurso, a cultura noticiosa a respeito do Movimento dos Trabalhadores Rurais Sem Terra (MST), no que se refere à cobertura jornalística dos jornais Zero Hora e Folha de S.Paulo das linhas políticas sobre as questões conjunturais apresentadas pelo Movimento em seus três últimos Congressos Nacionais (1995, 2000 e 2007), para comprovar o tratamento dado pela mídia ao MST e o modo como as formações discursivas em textualizações jornalísticas são indiciárias de permanente tensão em torno da luta pela terra, o que dificulta o diálogo do Movimento com a sociedade. Este trabalho pretende ainda debater qual a intervenção do MST na construção das agendas política e pública e por que o Movimento não consegue provocar mudanças em seu enquadramento noticioso e, assim, constatar o que o processo de saturação do discurso midiático, neste caso o do jornalismo impresso, é capaz de produzir sobre a sociedade, partindo da hipótese de que a mídia, em geral, funciona como aparelho político-ideológico, que elabora e divulga concepções de mundo, cumprindo a função de contribuir com orientações para exercer influência na compreensão dos fatos sociais. A mediação dos meios de comunicação de massa, em geral, produz um deslocamento na experiência pública e, ao mesmo tempo, dá forma aos saberes possíveis que essa experiência desenvolve sobre si mesma. Sabemos que as ideologias presentes nos discursos jornalísticos podem não produzir novos saberes sobre o mundo, mas produzem um reconhecimento do mundo tal como já aprendemos a apropriá-lo. Demonstrar-se-á que, na fase atual do capitalismo sistema que demanda maior valorização da informação , a reprodução ideológica se dá diretamente pelos meios de comunicação, por intermédio de pautas e agendas. Considerando o contexto apresentado pela pesquisa, o trabalho destaca também dois fios condutores para alcançar seus objetivos: a submissão da mídia à hegemonia neoliberal e a luta do MST pela reforma agrária diante da valorização do agronegócio latifundiário.

Monoculture of marine planktonic diatoms and the effects of different media on their growth and survival

Diatoms are the preferred live food of the protozoea stages of prawns. Due to seasonal variations, it is difficult to obtain continuous supply of diatoms and other algae throughout the year. Therefore mass culture of diatoms is necessary. At attempt was made to culture planktonic diatoms and to study the effect of Allen and Nelson media, Simon media, Vitamin B12 and treated sewage water media on their growth and survival. Navicula sp showed better growth in Allen and Nelson media, Coscinodiscus and Chaetoceros grew better in Simon media while Navicula sp and Coscinodiscus sp showed better growth in the combination of Allen and Nelson + Vitamin B12.

Mass culture of marine diatom Skeletonema costatum (Greville) Cleve collected from the Bay of Bengal

The growth of Skeletonema costatum in two artificial nutrient media was studied using various culture vessels. Skeletonema costatum was collected from the Cox's Bazar coast around the Bay of Bengal. Different growths stages i.e. lag phase, exponential phase, prestationary phase, stationary and death phase were observed during the culture period. The number of cells increased during the active division period and decreased after the beginning of the prestationary phase. The average densities of S. costatum in primary and secondary cultures were 0.55 x 10 super(6) cells mlˉ¹ and 0.93x10 super(6) cells mlˉ¹, respectively. In mass culture of S. costatum two, types of media were used. Highest cells densities of S. costatum cement tank culture were recorded 1.23x10 super(6) cell mlˉ¹ and 0.78x10 super(6) cells mlˉ¹ in their respective f/4 medium and commercial fertilizer medium. In the cement tanks culture fertilizer medium was found to be the best medium for mass culture of S. costatum in respect of production efficiency and culture stability.

Effect of immersion in various media on the sorption, solubility, elution of unreacted monomers, and flexural properties of two model dental composite compositions

Immersion in various media has different effect on the properties of dental composites, such as sorption, solubility, elution of unreacted monomers, flexural strength, and flexural elastic modulus. In the present work, the effect of immersion in various media and the relationship between the variation of these properties and the components of dental composite were investigated.

Extraction kinetics of thorium(IV) with primary amine N1923 in sulfate media using a constant interfacial cell with laminar flow

Extraction kinetics of thorium(IV) with primary amine N1923 in sulfate media has been investigated by a constant interfacial cell with laminar flow. Studies of interfacial tension and effects of the stirring rate, temperature, and specific interfacial area on mass transfer rate show that the most probable reaction zone takes place at the liquid-liquid interface. According to the experimental data correlated as a function of the concentration of the relevant species involved in the extraction reaction, the rate equation of extracting thorium has been obtained as follows: -d[Th(IV)]((o))/dt = 10(-3.10)center dot[Th(IV)](0.89)center dot[(RNH3)(2)SO4](0.74).

Detection of specific noncovalent protein-fullerenols complexes by matrix-assisted laser desorption ionization mass spectrometry

Matrix-assisted laser desorption ionization (MALDI) mass spectrometry is difficult for the characterization of noncovalent complexes hitherto because of the limitations in acidic matrix, sample preparation, laser-induced polymerization and adduct formation with matrix. Under our experimental conditions, sinapinic acid is used as a matrix, the specific noncovalent interactions of protein with fullerenols were observed by MALDI mass spectrometry. Some mass spectrometric features, such as mass shifts, broad adduct peaks and stoichiometries, showed that the specific non-covalent complexes between protein and fullerenols have been formed at a ratio of 1 : 4 for hemoglobin-fullerenols or 1 : 1 for myoglobin-fullerenols. The results implied that fullereneols could be used to protect partly hemoglobin from decomposition in acidic media, and therefore, it is possible to realize the molecular weight determination of a quaternary protein by MALDI mass spectrometry via the addition of specific organic compound in the matrix.