Quantifying Global Tolerance of Biochemical Systems: Design Implications for Moiety-Transfer Cycles

Robustness of organisms is widely observed although difficult to precisely characterize. Performance can remain nearly constant within some neighborhood of the normal operating regime, leading to homeostasis, but then abruptly break down with pathological consequences beyond this neighborhood. Currently, there is no generic approach to identifying boundaries where local performance deteriorates abruptly, and this has hampered understanding of the molecular basis of biological robustness. Here we introduce a generic approach for characterizing boundaries between operational regimes based on the piecewise power-law representation of the system's components. This conceptual framework allows us to define “global tolerance” as the ratio between the normal value of a parameter and the value at such a boundary. We illustrate the utility of this concept for a class of moiety-transfer cycles, which is a widespread module in biology. Our results show a region of “best” local performance surrounded by “poor” regions; also, selection for improved local performance often pushes the operating values away from regime boundaries, thus increasing global tolerance. These predictions agree with experimental data from the reduced nicotinamide adenine dinucleotide phosphate (NADPH) redox cycle of human erythrocytes

Rat muscle opacity decrease due to the osmosis of a simple mixture

It is known that the fibrous structure of muscle causes light scattering. This phenomenon occurs due to the refractive index discontinuities located between muscle fibers and interstitial fluid. To study the possibility of reducing light scattering inside muscle, we consider its spectral transmittance evolution during an immersion treatment with an optical clearing solution containing ethanol, glycerol, and distilled water. Our methodology consists of registering spectral transmittance of muscle samples while immersed in that solution. With the spectral data collected, we represent the transmittance evolution for some wavelengths during the treatment applied. Additionally, we study the variations that the treatment has caused on the samples regarding tissue refractive index and mass. By analyzing microscopic photographs of tissue cross section, we can also verify changes in the internal arrangement of muscle fibers caused by the immersion treatment. Due to a mathematical model that we develop, we can explain the variations observed in the studied parameters and estimate the amount of optical clearing agent that has diffused into the tissue samples during the immersion treatment. At the end of the study, we observe and explain the improvement in tissue spectral transmittance, which is approximately 65% after 20 min

Relating Mutant Genotype to Phenotype via Quantitative Behavior of the NADPH Redox Cycle in Human Erythrocytes

The NADPH redox cycle plays a key role in antioxidant protection of human erythrocytes. It consists of two enzymes: glucose-6-phosphate dehydrogenase (G6PD) and glutathione reductase. Over 160 G6PD variants have been characterized and associated with several distinct clinical manifestations. However, the mechanistic link between the genotype and the phenotype remains poorly understood.We address this issue through a novel framework (design space) that integrates information at the genetic, biochemical and clinical levels. Our analysis predicts three qualitatively-distinct phenotypic regions that can be ranked according to fitness. When G6PD variants are analyzed in design space, a correlation is revealed between the phenotypic region and the clinical manifestation: the best region with normal physiology, the second best region with a pathology, and the worst region with a potential lethality. We also show that Plasmodium falciparum, by induction of its own G6PD gene in G6PD-deficient erythrocytes, moves the operation of the cycle to a region of the design space that yields robust performance.In conclusion, the design space for the NADPH redox cycle, which includes relationships among genotype, phenotype and environment, illuminates the function, design and fitness of the cycle, and its phenotypic regions correlate with the organism's clinical status

Understanding social enterprises in the United Kingdom: the case of South Yorkshire

Purpose-- This study analyses the development of social enterprises in the UK, in the context of the increased need for creative solutions to ameliorate deprivation and deliver effective public services. Design/methodology/approach-- The investigation draws on a mixed method approach, using a postal survey of 102 social enterprises complemented by detailed analysis of two selected cases and key informant interviews. Findings-- The results of the study show that there is a paradigm shift in the practice and conceptualisation of social enterprises in South Yorkshire as they are increasingly taking a more corporate approach to achieve their outcomes. Research limitations/implications-- The study is limited to social enterprises in South Yorkshire, UK. Further comparative analysis in other regions and social contexts is required in order to explore if these results are widely applicable. Practical implications-- This study is of potential benefit to researchers and those involved in formulating policies for the development and support of social enterprise. Originality/value-- The study contributes to the extant literature by investigation of the development of social enterprise in competitive markets, which is an area that requires further academic scrutiny. The South Yorkshire region presents an interesting case that extends our understanding of the operations of social enterprises in the UK given the high levels of deprivation due to the steady decline of its industrial base ( Bache and Chapman, 2008)

Avaliação do stock de Abalones: uma pesca sustentável

Jornadas "Ciência nos Açores – que futuro? Tema Ciências Naturais e Ambiente", Ponta Delgada, 7-8 de Junho de 2013.A falta de informação anterior ao início de uma exploração de uma espécie alvo é ponto comum à maior parte das pescarias. A maioria dos estudos só é iniciada após indícios claros de efeitos de um excesso de pesca. No entanto, esta situação é indicadora de que a pesca já causou alterações drásticas na estrutura das populações alvo e que, consequentemente, já não existe um ponto de referência que informe a gestão e a recuperação dos mananciais. A exploração do abalone nos Açores é virtualmente inexistente, ao contrário de muitas outras regiões onde a sua captura tem levado à ruptura dos mananciais. A espécie existente nos Açores, Haliotis tuberculata, é um recurso com elevado interesse gastronómico e económico e existem indícios de que tem sido gradualmente introduzida na gastronomia regional. Nos Açores os mananciais de H. tuberculata podem, à partida, ser considerados virgens, mas não existe informação sobre a sua abundância, biologia e ecologia. Concomitantemente, não existe qualquer tipo de restrição ou legislação regional relativamente à exploração deste marisco. O presente projecto tem como objectivo avaliar o estado actual das populações de H. tuberculata providenciando um ponto de referência para estudos futuros e garantindo deste modo uma avaliação rigorosa dos impactos de uma potencial pescaria. Neste projecto examinam-se aspectos da biologia e da ecologia de H. tuberculata que providenciarão dados úteis para garantir uma exploração sustentável deste recurso. O presente estudo providenciará também recomendações para a gestão desta pescaria baseadas na revisão bibliográfica e na informação recolhida.ABSTRACT: A common drawback in predicting the consequences of harvest rates is that there is no a priori information regarding the status of exploited populations. Most studies are done only when there is a perceived impact upon the targeted populations. In most situations, this means that fishing has already caused dramatic reductions in populations sizes and changes in the population structure so that a reference state against which to compare and predict the resilience or recovery of target populations does not exist. In the Azores unlike there has been little impact on the stocks of the abalone Haliotis tuberculata. However, H. tuberculata is a valuable and highly regarded resource and there is now evidence that it is slowly being introduced into the regional gastronomy. Although Azorean abalone stocks may be considered relatively virgin, there is yet no information regarding the local abundance, biology or ecology of this species. Similarly, there is no regional legislation regarding the exploitation of this shellfish. The present project aims to provide a reference state to which future studies can be compared and thus accurately assess the impact of a potential fishery. This involves examining the biology and ecology of H. tuberculata, creating a dynamic population model that will inform the authorities and provide valuable information that fosters sustainable harvest rates. The present project will also provide recommendations for the future management of the fishery based on a literature review and the field information collected

Heterocyclic aromatic amines formation in grilled fatty fish

[resumo][abstract

Analysis of the equilibrium distribution of Ligands in Heterogeneous Media – Approaches and pitfalls

The equilibrium distribution of small molecules (ligands) between binding agents in heterogeneous media is an important property that determines their activity. Heterogeneous systems containing proteins and lipid membranes are particularly relevant due to their prevalence in biological systems, and their importance to ligand distribution, which, in turn, is crucial to ligand’s availability and biological activity. In this work, we review several approaches and formalisms for the analysis of the equilibrium distribution of ligands in the presence of proteins, lipid membranes, or both. Special attention is given to common pitfalls in the analysis, with the establishment of the validity limits for the distinct approaches. Due to its widespread use, special attention is given to the characterization of ligand binding through the analysis of Stern–Volmer plots of protein fluorescence quenching. Systems of increasing complexity are considered, from proteins with single to multiple binding sites, from ligands interacting with proteins only to biomembranes containing lipid bilayers and membrane proteins. A new formalism is proposed, in which ligand binding is treated as a partition process, while considering the saturation of protein binding sites. This formalism is particularly useful for the characterization of interaction with membrane proteins.info:eu-repo/semantics/publishedVersio

Analysis of the Equilibrium Distribution of Ligands in Heterogeneous Media–Approaches and Pitfalls

The equilibrium distribution of small molecules (ligands) between binding agents in heterogeneous media is an important property that determines their activity. Heterogeneous systems containing proteins and lipid membranes are particularly relevant due to their prevalence in biological systems, and their importance to ligand distribution, which, in turn, is crucial to ligand’s availability and biological activity. In this work, we review several approaches and formalisms for the analysis of the equilibrium distribution of ligands in the presence of proteins, lipid membranes, or both. Special attention is given to common pitfalls in the analysis, with the establishment of the validity limits for the distinct approaches. Due to its widespread use, special attention is given to the characterization of ligand binding through the analysis of Stern–Volmer plots of protein fluorescence quenching. Systems of increasing complexity are considered, from proteins with single to multiple binding sites, from ligands interacting with proteins only to biomembranes containing lipid bilayers and membrane proteins. A new formalism is proposed, in which ligand binding is treated as a partition process, while considering the saturation of protein binding sites. This formalism is particularly useful for the characterization of interaction with membrane proteins

Caracóis endémicos dos Açores : estivação como mecanismo de resposta aos fatores ambientais

A secção Biologia é coordenada pelo Professor Universitário Armindo Rodrigues.[…] Estudos realizados sobre caracóis terrestres endémicos dos Açores têm revelado que estes, ao contrário do observado noutras espécies de moluscos da América do Sul e do Norte, tem a capacidade de se reproduzir durante todo o ano, o que tem sido atribuído a características climáticas propicias verificadas no arquipélago, em termos de temperatura, precipitação ou humidade do solo. A montanha do Pico (Ilha do Pico) é o melhor “laboratório” dos Açores para avaliar como fatores abióticos, que variam ao longo de um gradiente altitudinal, podem desencadear respostas fisiológicas e comportamentais numa espécie, com significado na sua reprodução e sobrevivência. […]info:eu-repo/semantics/publishedVersio

Moluscos terrestres da ilha de São Jorge. Lista preliminar.

VII Expedição Científica do Departamento de Biologia - São Jorge e Topo - 1992.A fauna malacológica terrestre da ilha de São Jorge não tem despertado a atenção dos especialistas por, aparentemente, não se destacar da malacofauna terrestre das ilhas circundantes. Morelet não teve oportunidade de fazer recolhas em São Jorge durante a sua estada de 6 meses nos Açores, em 1857; a fauna malacológica jorgense ficou, assim, ausente da primeira e mais importante obra sobre a malacologia terrestre Açórica (Morelet, 1860). Nobre (1924) assinalou para São Jorge cinco endemismos açóricos: Helix [=Actinella] vespertina, profusamente distribuída no Grupo Central, Lauria fasciolata, comum em todo o Arquipélago; das restantes espécies endémicas assinaladas por Nobre para esta ilha, duas (Hyalinia [=Oxychilus) atlantica; Bulimus (="Napaeus") vulgaris) são provavelmente identificações erróneas, pois são endemismos de São Miguel, e a terceira (Bulimus (="Napaeus"] forbesianus), embora endémico do Grupo Central, não foi por nós recolhida. Backhuys (1975) estudou a malacofauna de São Jorge, tendo assinalado doze endemismos açóricos; se bem que Backhuys haja reconhecido a existência de algumas espécies novas, sobre as quais não se debruçou, a presença de Plutonia atlantica foi o registo mais importante