Structural analysis of oligomeric and protofibrillar Aß amyloid pair structures considering F20L mutation effects using molecular dynamics simulations.

Aß amyloid proteins are involved in neuro-degenerative diseases such as Alzheimer's, Parkinson's, and so forth. Because of its structurally stable feature under physiological conditions, Aß amyloid protein disrupts the normal cell function. Because of these concerns, understanding the structural feature of Aß amyloid protein in detail is crucial. There have been some efforts on lowering the structural stabilities of Aß amyloid fibrils by decreasing the aromatic residues characteristic and hydrophobic effect. Yet, there is a lack of understanding of Aß amyloid pair structures considering those effects. In this study, we provide the structural characteristics of wildtype (WT) and phenylalanine residue mutation to leucine (F20L) Aß amyloid pair structures using molecular dynamics simulation in detail. We also considered the polymorphic feature of F20L and WT Aß pair amyloids based on the facing ß-strand directions between the amyloid pairs. As a result, we were able to observe the varying effects of mutation, polymorphism, and protofibril lengths on the structural stability of pair amyloids. Furthermore, we have also found that opposite structural stability exists on a certain polymorphic Aß pair amyloids depending on its oligomeric or protofibrillar state, which can be helpful for understanding the amyloid growth mechanism via repetitive fragmentation and elongation mechanism. Proteins 2017; 85:580-592. © 2016 Wiley Periodicals, Inc.

Critical perspectives on mercury toxicity reference values for protection of fish.

Environmental management decisions at mercury-contaminated sediment sites are predicated on the understanding of risks to various receptors, including fish. Toxicity reference values (TRVs) for interpreting risks to fish have been developed to assess mercury concentrations in fish or fish prey. These TRVs were systematically evaluated based on several lines of evidence. First, their conceptual basis and specific derivation were evaluated, including a close review of underlying toxicity studies. Second, case studies were reviewed to investigate whether TRVs are predictive of effects on fish populations in the field. Third, TRVs were compared with available information regarding preindustrial and present-day background concentrations of mercury in fish. The findings show that existing TRVs are highly uncertain, because they were developed using limited data from studies not designed for TRV derivation. Although field studies also entail uncertainty, several case studies indicate no evidence of adverse effects despite mercury exposures that exceed the available TRVs. Some TRVs also fall within the range of background mercury concentrations in predatory or prey fish. Lack of information on the selenium status of mercury-exposed fish is a critical confounding factor, and the form of methylmercury used in toxicity testing may also contribute to differences between TRV-based predictions and field observations of mercury effects on fish. On balance, the available information indicates that several of the TRVs reviewed are lower than necessary to protect fish populations. The 20% effect concentration from a previously published dose-response analysis appears closer to an effect threshold, based on available laboratory data. Additional research is needed to provide a stronger basis to establish dose-response relationships for mercury effects on fish.

Neighboring residue effects in terminally blocked dipeptides: implications for residual secondary structures in intrinsically unfolded/disordered proteins.

For nuclear magnetic resonance (NMR)-based protein structure determinations, the random coil chemical shifts are very important because the secondary and tertiary protein structure predictions become possible by examining deviations of measured chemical shifts from those reference chemical shift values. In addition, neighboring residue effects on chemical shifts and J-coupling constants are crucial in understanding the nature of conformational propensities exhibited by unfolded or intrinsically disordered proteins. We recently reported the 1D NMR results for a complete set of terminally blocked dipeptides (Oh KI, Jung YS, Hwang GS, Cho M. J Biomol NMR 2012;53:25-41), but the NMR resonance assignments were not possible so that the average chemical shifts and J-coupling constants were only considered. In the present work, to thoroughly investigate the neighboring residue effects and random coil chemical shifts we extend the previous studies with 2D NMR, and measured all the (3) J(HNHα) values and H(α) and H(N) chemical shifts of the same set of terminally blocked dipeptides that are free from structural effects like secondary structure, hydrogen-bond, long-range backbone, and side-chain interactions. In particular, the preceding and following residue effects on amino-acid backbone conformational propensities are revealed and directly compared with previous works on either short peptides or empirical chemical shift database.

Persistência de agrotóxicos utilizados na produção integrada de maçã a Trichogramma pretiosum / Persistence of pesticides used in integrated production of apple to Trichogramma pretiosum

No sistema de Produção Integrada de Maçã (PIM) o controle biológico de pragas é uma importante tática de controle, no entanto, a sua utilização pode ser limitada pela utilização de agrotóxicos. Nesse contexto, objetivou-se, com este trabalho, avaliar a persistência (duração da atividade nociva) de dez agrotóxicos recomendados na PIM sobre o parasitóide de ovos Trichogramma pretiosum. Insetos adultos foram expostos ao contato com resíduos de agrotóxicos pulverizados sobre folhas de videira cv. Isabel, sendo avaliado o efeito residual dos agrotóxicos sobre o parasitismo de T. pretiosum, aos 3, 10, 17, 24 e 31 dias após a pulverização, de acordo com a metodologia sugerida pela IOBC. O parâmetro utilizado para classificar os agrotóxicos foi a redução no parasitismo. Os resultados demonstraram que os produtos comerciais/ingredientes ativos (g ou mL da formulação comercial.100 L-1): o inseticida Malathion® 1000 CE/malationa (100) e os fungicidas Domark® 100 CE/tetraconazole (50), Manzate® 800/mancozebe (200), Mancozebe Sipcam®/mancozebe (200) e Metiltiofan®/tiofanato metilico (90) foram classificados como de vida curta (< 5 dias de ação nociva); o inseticida/acaricida Vertimec® 18 CE/abamectina (100) como levemente persistente (5-15 dias de ação nociva), o inseticida Lorsban® 480 BR/clorpirifós (150) como moderadamente persistente (16-30 dias de ação nociva) e os inseticidas Imidan® 500 PM/fosmete (200) e Sevin® 480 SC/carbaril (360) e o fungicida/acaricida Kumulus® DF/enxofre (600) como persistentes (> 31 dias de ação nociva) a T. pretiosum.

In the Integrated Production of Apple (IPA) the biological control is an important control tactics, however, it may be limited by the use of pesticides. Thus, the objective of this work was to evaluate the persistence (duration of harmful activity) of ten pesticides indicated in the IPA on the egg parasitoid Trichogramma pretiosum. Insect adults were exposed to pesticide residues on the leaves of vine cv. Isabel. The residue effect was evaluated on parasitism of T. pretiosum, at 3, 10, 17, 24 and 31 days after the treatment, using the IOBC standard methodology. The reduction in capacity of parasitism of T. pretiosum was used to measure the effect of the pesticides. The results showed that the products, commercial name/active ingredient (g or mL commercial formulation.100 L-1), insecticide Malathion® 1000 CE/malathion (100) and the fungicides Domark® 100 CE/tetraconazol (50), Manzate® 800 /mancozeb (200), Mancozeb Sipcam® /mancozeb (200) and Metiltiofan® /thiophanate-methyl (90) were classified as short lived (< 5 days); the insecticide/acaricid Vertimec® 18 CE/abamectin (100) as slightly persistent (5-15 days of harmful action), the insecticide Lorsban® 480 BR/chlorpyrifos (150) as moderately persistent (16-30 days of harmful action), the insecticides Imidan® 500 PM/phosmet (200) and Sevin® 480 SC/carbaryl (360) and the fungicide/acaricid Kumulus® DF/sulphur (600) were persistent (> 31 days of harmful action) to T. pretiosum.