Coexistence patterns of benthic gastropods on the Uruguayan shelf

Community assembly rules theory attempt to understand the processes that determine the composition of local communities from a regional species pool. Nestedness and negative co‐occurrence are two of the most commonly reported meta‐community patterns, but almost exclusively from terrestrial and freshwater ecosystems. Here we analyzed the structure of species coexistence in six datasets containing presence/absence data for 120 marine benthic gastropod species in 249 sampling units on the Uruguayan continental shelf and Río de la Plata estuary. The ecological features of this system, such as the idiosyncratic nature of the biogeographic and oceanographic realms, are clearly different from those observed in other systems previously targeted by studies on coexistence structure. Community patterns were evaluated using null models and four structure indices. The existence of patterns in community assembly, and in particular segregated co‐occurrence, was verified only when analyzing the number of checkerboard units (CH index). This indicates more mutually exclusive species pairs than expected by chance. Nestedness, on the other hand, was not detected in any dataset. Storage and rescue effects related to overall high immigration and low local extinction rates are plausible mechanisms to account for the general pattern of random species coexistence, while the segregated co‐occurrence pattern depicted by the CH index may be related to differential habitat requirements within species pairs. Our study highlights the importance of analyzing metacommunity structures in alternative biological, environmental, and historical contexts in order to advance on the construction of a general ecological theory, relating patterns with the processes dominating in particular ecosystems.     

Suppression of aortic elastic tissue autofluorescence for the detection of viral antigen

Summary Suppression of aortic elastic tissue autofluorescence was achieved by employing a modification of Verhoeff's elastic tissue staining procedure. Consequently, coxsackievirus B antigen present in the aortic media was detected by conventional fluorescent antibody staining.     

An artificial self‐sufficient cytochrome P450 directly nitrates fluorinated tryptophan analogs with a different regio‐selectivity

Aromatic nitration is an immensely important industrial process to produce chemicals for a variety of applications, but it often suffers from multiple unsolved challenges. Enzymes as biocatalysts have been increasingly used for organic chemistry synthesis due to their high selectivity and environmental friendliness, but nitration has benefited minimally from the development of biocatalysis. In this work, we aimed to develop TxtE as practical biocatalysts for aromatic nitration. TxtE is a unique class I cytochrome P450 enzyme that nitrates the indole of l ‐tryptophan. To develop cost‐efficient nitration processes, we fused TxtE with the reductase domains of CYP102A1 (P450BM3) and of P450RhF to create class III self‐sufficient biocatalysts. The best engineered fusion protein was comparable with wild type TxtE in terms of nitration performance and other key biochemical properties. To demonstrate the application potential of the fusion enzyme, we nitrated 4‐F‐dl ‐tryptophan and 5‐F‐l ‐tryptophan in large scale enzymatic reactions. Tandem MS/MS and NMR analyses of isolated products revealed altered nitration sites. To our knowledge, these studies represent the first practice in developing biological nitration approaches and lay a solid basis to the use of TxtE‐based biocatalysts for the production of valuable nitroaromatics.     

Protein dynamics from solution NMR

Solution nuclear magnetic resonance (NMR) spectroscopy is unique in its ability to elucidate the details of atomic-level structural and dynamical properties of biological macromolecules under native-like conditions. Recent advances in NMR techniques and protein sample preparation now allow comprehensive investigation of protein dynamics over timescales ranging 14 orders of magnitude at nearly every atomic site. Thus, solution NMR is poised to reveal aspects of the physico-chemical properties that govern the ensemble distribution of protein conformers and the dynamics of their interconversion. We review these advances as well as their recent application to the study of proteins.     

Some Possible Dynamical Constraints for Life’s Origin

Oscillating biochemical reactions are common in cell dynamics and could be closely related to the emergence of the life phenomenon itself. In this work, we study the dynamical features of some classical chemical or biochemical oscillators where the effect of cell volume changes is explicitly considered. Such analysis enables us to find some general conditions about the cell membrane to preserve such oscillatory patterns, of possible relevance to hypothetical primitive cells in which these structures first appeared.     

Suppression of aortic elastic tissue autofluorescence for the detection of viral antigen.

Suppression of aortic elastic tissue autofluorescence was achieved by employing a modification of Verhoeff's elastic tissue staining procedure. Consquently, coxsackievirus B antigen present in the aortic media was detected by conventional fluorescent antibody staining.