Docking and molecular dynamics studies of peripheral site ligand–oximes as reactivators of sarin-inhibited human acetylcholinesterase

In the present work, we performed docking and molecular dynamics simulations studies on two groups of long-tailored oximes designed as peripheral site binders of acetylcholinesterase (AChE) and potential penetrators on the blood brain barrier. Our studies permitted to determine how the tails anchor in the peripheral site of sarin-inhibited human AChE, and which aminoacids are important to their stabilization. Also the energy values obtained in the docking studies corroborated quite well with the experimental results obtained before for these oximes.     

Influence of salinity on dimethyl sulfide and methanethiol formation in estuarine sediments and its side effect on nitrous oxide emissions

We investigated the regulatory effect of salinity on the production of dimethylsulfide (DMS) and methanethiol (MeSH) in estuarine sediments and the potential interactions with the nitrous oxide (N₂O) reductase step of the denitrification pathway. This was achieved by monitoring DMS, MeSH and N₂O accumulation in sediment slurries retrieved from a temperate estuary (Ave, NW Portugal). Treatments were performed with and without amendments of potential sulfur gas precursors, DMSP (0–50?μM) or methionine (0–500?μM) at different salinities (0, 15 and 30?ppt). Experimental increases of salinity inhibited DMS accumulation under both oxic and anoxic incubation conditions, and the pattern was observed whether DMSP or methionine was added or not, i.e. lower salinities stimulated DMS net production. In contrast, MeSH tended to accumulate to higher concentrations in higher salinity treatments (15 and 30?ppt). Our results also suggest that while salinity had a direct influence on N₂O accumulation, it also may modulated N₂O production through its regulatory effect on the formation of MeSH, a compound previously shown to inhibit N₂O reduction activity. Overall, our results suggest that changes in salinity may have an important regulatory role in net production of DMS, MeSH and N₂O and their potential emissions to the atmosphere.     

A DNA Damage Checkpoint Pathway Coordinates the Division of Dikaryotic Cells in the Ink Cap Mushroom Coprinopsis cinerea

The fungal fruiting body or mushroom is a multicellular structure essential for sexual reproduction. It is composed of dikaryotic cells that contain one haploid nucleus from each mating partner sharing the same cytoplasm without undergoing nuclear fusion. In the mushroom, the pileus bears the hymenium, a layer of cells that includes the specialized basidia in which nuclear fusion, meiosis, and sporulation occur. Coprinopsis cinerea is a well-known model fungus used to study developmental processes associated with the formation of the fruiting body. Here we describe that knocking down the expression of Atr1 and Chk1, two kinases shown to be involved in the response to DNA damage in a number of eukaryotic organisms, dramatically impairs the ability to develop fruiting bodies in C. cinerea, as well as other developmental decisions such as sclerotia formation. These developmental defects correlated with the impairment in silenced strains to sustain an appropriated dikaryotic cell cycle. Dikaryotic cells in which chk1 or atr1 genes were silenced displayed a higher level of asynchronous mitosis and as a consequence aberrant cells carrying an unbalanced dose of nuclei. Since fruiting body initiation is dependent on the balanced mating-type regulator doses present in the dikaryon, we believe that the observed developmental defects were a consequence of the impaired cell cycle in the dikaryon. Our results suggest a connection between the DNA damage response cascade, cell cycle regulation, and developmental processes in this fungus.     

Quantification of Inter-particle Spacing Caused by Thiol Self-Assembled Monolayers Using Transmission Electron Microscopy

Plasmonics - Nano-surface modification techniques have been increasingly reported in a multitude of applications. However, the metal-ligand interface can be difficult to characterize, mainly due to...     

Acoustic and Morphological Differentiation in the Frog Allobates femoralis: Relationships with the Upper Madeira River and Other Potential Geological Barriers

We studied patterns of call acoustics and external morphological differentiation in populations of the dart-poison frog Allobates femoralis occurring in forested areas along a 250-km stretch of the upper Madeira River, Brazil. Multivariate analyses of variance using principal components representing shared acoustic and morphological parameters distinguished three groups in relation to call structure and external morphology: (1) populations belonging to a two-note call morphotype; (2) populations with four-note calls inhabiting the left riverbank; and (3) populations with four-note calls inhabiting the right riverbank. Our results report a case of Amazonian anuran diversity hidden by current taxonomy and provide evidence for the upper Madeira River being a boundary between distinct populations of A. femoralis , and suggest a new taxonomic interpretation for these groups. Samples that did not fit into the general differentiation pattern and the existence of a well-defined contact zone between two morphotypes on the left riverbank indicate that mechanisms complementary to river-barrier hypotheses are necessary to explain the phenotypic differentiation between populations. Our study shows that at least one anuran species shows congruence between population differentiation and separation by a large Amazonian river, as documented for birds and mammals. Conservation efforts should not consider the taxon now known as A. femoralis as a homogeneous entity. There is much within-taxon variability, which can be probably explained partly by the existence of cryptic species, partly by geological barriers and part of which currently has no obvious explanation.