Self-assembly, nematic phase formation and organocatalytic behaviour of a proline-functionalized lipopeptide

The self-assembly of the amphiphilic lipopeptide PAEPKI-C16 (P = proline, A = alanine, E = glutamic acid, K = lysine, I = isoleucine, C16 = hexadecyl) was investigated using a combination of spectroscopic, microscopic and scattering methods and compared to C16-IKPEAP with the same (reversed) peptide sequence and the alkyl chain positioned N-terminally and which lacks a free N-terminal proline residue. The catalytic activity of these peptides were then compared using a model aldol reaction system. For PAEPKI-C16, Cryo-TEM images showed the formation of micrometer length fibers, which by Small-angle X-ray scattering (SAXS) were found to have a radius of 2.5 - 2.6 nm. Spectroscopic analysis shows these fibers are built from -sheets. This behaviour is in complete contrast to that of C16-IKPEAP which forms spherical micelles with peptides in a disordered conformation [Hutchinson, J. A. et al. J. Phys. Chem. B 2019, 123, 613]. For PAEPKI-C16, the spontaneous alignment of fibers was observed upon increasing pH, which was accompanied by observed birefringence and anisotropy of SAXS patterns. This shows the formation of a nematic liquids and unprecedented nematic hydrogel formation was also observed these lipopeptides at sufficiently high concentrations. SAXS shows retention of an ultrafine (1.7 nm core radius) fibrillar network within the hydrogel. PAEPKI-C16 with free N-terminal proline shows enhanced anti:syn diastereoselectivity and better conversion compared to C16-IKPEAP. The cytotoxicity of PAEPKI-C16 was also lower than C16-IKPEAP for both fibroblast and cancer cell lines. These results highlight the sensitivity of lipopeptide properties to the presence of a free proline residue. The spontaneous nematic phase formation by PAEPKI-C16 points to the highly anisotropy of its ultrafine fibrillar structure and the formation of such a phase at low concentration in aqueous solution may be valuable for future applications

RELATIVE ABUNDANCE AND MICROHABITAT OF FOUR SYMPATRIC ANTPITTAS IN AN INTERANDEAN VALLEY OF SOUTHERN ECUADOR

Exploring mechanisms that determine species coexistence is a key step to understand community organization and patterns of distribution of biodiversity. Anpittas, genus Grallaria, offer a great opportunity to measure coexistence mechanisms among closely related species. Antpittas are terrestrial insectivores with a specialized foraging technique and limited dispersal abilities; these factors could produce high levels of niche overlap and consequently reduce the chances of stable coexistence. We explored niche partitioning in space among four antpitta species (Rufous Antpitta, Chesnut-crowned Antpitta, Undulated Antpitta, Tawny Antpitta) which coexist in a tropical Andean valley located in southern Ecuador. We determined the abundance of each antpitta species in mature native forest, shrub, pasture, and páramo habitats, and gathered data about the microhabitat of each species. Abundance was determined using point counts, territories were located by triangulating on individual calls, and microhabitat characteristics were measured within each territory. We found no differences in the abundance or probability of occurrence of species among habitats for Rufous Antpitta, Chesnut-crowned Antpitta, and Undulated Anpitta, but Tawny Antpitta was restricted to páramo. At the microhabitat level, Rufous and Chesnut-crowned Antpittas shared similar vegetation characteristics, with the important presence of shrubs. Undulated Antpitta occurred in a microhabitat characterized by the presence of trees and a ground cover of mosses, while Tawny Antpitta occupied microhabitats with an open vegetation. In general our results suggest that closely related birds could partition their niche at different spatial scales, which could promote the coexistence of species in the tropical Andes

Indução assimétrica 1,5-Anti na adição de enolatos de boro de metilcetonas beta-oxigenadas a aldeídos

High levels of substrate-based 1,5-stereoinduction are obtained in the boron-mediated aldol reactions of beta-oxygenated methyl ketones with achiral and chiral aldehydes. Remote induction from the boron enolates gives the 1,5-anti adducts, with the enolate pi-facial selectivity critically dependent upon the nature of the beta-alkoxy protecting group. This 1,5-anti aldol methodology has been strategically employed in the total synthesis of several natural products. At present, the origin of the high level of 1,5-anti induction obtained with the boron enolates is unclear, although a model based on a hydrogen bonding between the alkoxy oxygen and the formyl hydrogen has been recently proposed

Genes of the RAV family control heading date and carpel development in rice

In plants, correct formation of reproductive organs is critical for successful seedset and perpetuation of the species. Plants have evolved different molecular mechanisms to coordinate flower and seed development at the proper time of the year. Among the plant-specific RELATED TO ABI3 AND VP1 (RAV) family of transcription factors, only TEMPRANILLO1 (TEM1) and TEM2 have been shown to affect reproductive development in Arabidopsis (Arabidopsis thaliana). They negatively regulate the floral transition through direct repression of FLOWERING LOCUS T and GIBBERELLIN 3-OXIDASE1/2, encoding major components of the florigen. Here we identify RAV genes from rice (Oryza sativa), and unravel their regulatory roles in key steps of reproductive development. Our data strongly suggest that, like TEMs, OsRAV9/OsTEM1 has a conserved function as a repressor of photoperiodic flowering upstream of the floral activators OsMADS14 and Hd3a, through a mechanism reminiscent of that one underlying floral transition in temperate cereals. Furthermore, OsRAV11 and OsRAV12 may have acquired a new function in the differentiation of the carpel and the control of seed size, acting downstream of floral homeotic factors. Alternatively, this function may have been lost in Arabidopsis. Our data reveal conservation of RAV gene function in the regulation of flowering time in monocotyledonous and dicotyledonous plants, but also unveil roles in the development of rice gynoecium

Ruling out Stellar Companions and Resolving the Innermost Regions of Transitional Disks with the Keck Interferometer

With the Keck Interferometer, we have studied at 2 um the innermost regions of several nearby, young, dust depleted "transitional" disks. Our observations target five of the six clearest cases of transitional disks in the Taurus/Auriga star-forming region (DM Tau, GM Aur, LkCa 15, UX Tau A, and RY Tau) to explore the possibility that the depletion of optically thick dust from the inner disks is caused by stellar companions rather than the more typical planet-formation hypothesis. At the 99.7% confidence level, the observed visibilities exclude binaries with flux ratios of at least 0.05 and separations ranging from 2.5 to 30 mas (0.35 - 4 AU) over >= 94% of the area covered by our measurements. All targets but DM Tau show near-infrared excess in their SED higher than our companion flux ratio detection limits. While a companion has previously been detected in the candidate transitional disk system CoKu Tau/4, we can exclude similar mass companions as the typical origin for the clearing of inner dust in transitional disks and of the near-infrared excess emission. Unlike CoKu Tau/4, all our targets show some evidence of accretion. We find that all but one of the targets are clearly spatially resolved, and UX Tau A is marginally resolved. Our data is consistent with hot material on small scales (0.1 AU) inside of and separated from the cooler outer disk, consistent with the recent SED modeling. These observations support the notion that some transitional disks have radial gaps in their optically thick material, which could be an indication for planet formation in the habitable zone (~ a few AU) of a protoplanetary disk.Comment: 36 pages, 7 figures. Accepted for publication in Ap

Polymorphism of asymmetric catalysts based on amphiphilic lipopeptides in solution

The self-assembly of model [P]RWG lipopeptides (P: L-proline, R: L-arginine, W: L-tryptophan, G: L-glycine), containing one or two aliphatic octadecyl (C18) chains in water and cyclohexanone/water solutions was examined. The self-assembly of mixtures of these RWG and PRWG lipopeptides was also investigated. These materials presented a similar critical aggregation concentration of ∼4.0 × 10−4 wt% and were characterized by unordered secondary structures with some β-sheet content. TEM and cryo-TEM revealed the presence of mainly nanotape structures with micelles observed for systems rich in PRWG(C18H37). Analysis of detailed SAXS form factor measurements revealed the presence of bilayers 3–4 nm thick while the PRWG(C18H37) micelles have a core radius of approximately 3 nm, and a shell thickness of 2 nm. For the cyclohexanone/water systems polymorphs containing cluster aggregates (with radius of 0.25 nm to 0.50 nm) and some elongated structures (with radius of 5.7 nm to 26.1 nm) were seen. Longer structures were formed with the increase of the proline-containing lipopeptide content. The catalytic activity of these peptides was assessed using a model nitro-aldol reaction. The concentration of water in the reaction system influenced the conversion, higher content promoted better efficiency for the water systems, but the opposite was observed for the cyclohexanone/water samples

Agricultura y contaminación del agua

El libro trata un tema cuya importancia contrasta con su escaso estudio. Los efectos negativos de las actividades agrícolas en la calidad del agua han recibido mucha atención en otros países y muy poca en el nuestro. En México, 76% del agua se emplea en la agricultura y el conocimiento de su huella contaminante es escaso. Este libro es resultado de una investigación multidisciplinaria que muestra a la agricultura poco amigable con el agua; que los agricultores tienen una percepción sesgada de su actividad y no reconocen sus efectos en el ambiente; que el gobierno interviene con políticas erróneas estimulando el uso de insumos contaminantes, y que un grupo importante de agricultores realiza prácticas agrícolas poco sustentables. Ante tal panorama, el libro aporta información sobre este problema en una importante región agrícola; propone algunas medidas e instrumentos para minimizarlo; cubre un vacío en la investigación y la información y espera que motive estudios similares en otras regiones del país

NLR family pyrin domain containing 3 (NLRP3) and caspase 1 (CASP1) modulation by intracellular Cl– concentration

The impairment of the cystic fibrosis transmembrane conductance regulator (CFTR) activity induces intracellular chloride (Cl–) accumulation. The anion Cl–, acting as a second messenger, stimulates the secretion of interleukin-1β (IL-1β), which starts an autocrine positive feedback loop. Here, we show that NLR family pyrin domain containing 3 (NLRP3) and caspase 1 (CASP1) are indirectly modulated by the intracellular Cl– concentration, showing maximal expression and activity at 75 mM Cl–, in the presence of the ionophores nigericin and tributyltin. The expression of PYD and CARD domain containing (PYCARD/ASC) remained constant from 0 to 125 mM Cl–. The CASP1 inhibitor VX-765 and the NLRP3 inflammasome inhibitor MCC950 completely blocked the Cl–-stimulated IL-1β mRNA expression and partially the IL-1β secretion. DCF fluorescence (cellular reactive oxygen species, cROS) and MitoSOX fluorescence (mitochondrial ROS, mtROS) also showed maximal ROS levels at 75 mM Cl–, a response strongly inhibited by the ROS scavenger N-acetyl-L-cysteine (NAC) or the NADPH oxidase (NOX) inhibitor GKT137831. These inhibitors also affected CASP1 and NLRP3 mRNA and protein expression. More importantly, the serum/glucocorticoid regulated kinase 1 (SGK1) inhibitor GSK650394, or its shRNAs, completely abrogated the IL-1β mRNA response to Cl– and the IL-1β secretion, interrupting the autocrine IL-1β loop. The results suggest that Cl– effects are mediated by SGK1, in which under Cl– modulation stimulates the secretion of mature IL-1β, in turn, responsible for the upregulation of ROS, CASP1, NLRP3 and IL-1β itself, through autocrine signalling.Fil: Clauzure, Mariangeles. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Ciencias Biológicas y Biomédicas del Sur. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Instituto de Ciencias Biológicas y Biomédicas del Sur; Argentina. Universidad Nacional de La Pampa; ArgentinaFil: Valdivieso, Ángel Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Ciencias Biológicas y Biomédicas del Sur. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Instituto de Ciencias Biológicas y Biomédicas del Sur; ArgentinaFil: Dugour, Andrea Vanesa. Fundación Pablo Cassará; ArgentinaFil: Mori, Consuelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Ciencias Biológicas y Biomédicas del Sur. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Instituto de Ciencias Biológicas y Biomédicas del Sur; ArgentinaFil: Massip Copiz, María Macarena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Ciencias Biológicas y Biomédicas del Sur. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Instituto de Ciencias Biológicas y Biomédicas del Sur; ArgentinaFil: Aguilar, María Á.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Ciencias Biológicas y Biomédicas del Sur. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Instituto de Ciencias Biológicas y Biomédicas del Sur; ArgentinaFil: Sotomayor, Veronica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Ciencias Biológicas y Biomédicas del Sur. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Instituto de Ciencias Biológicas y Biomédicas del Sur; ArgentinaFil: Asensio, Cristian Jorge Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Ciencias Biológicas y Biomédicas del Sur. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Instituto de Ciencias Biológicas y Biomédicas del Sur; ArgentinaFil: Figueroa, Juan M.. Fundación Pablo Cassará; ArgentinaFil: Santa Coloma, Tomás Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Ciencias Biológicas y Biomédicas del Sur. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Instituto de Ciencias Biológicas y Biomédicas del Sur; Argentin

Knowing the past to improve the future: Estimating historical fishing catches to improve fisheries management in the Western Mediterranean Sea

We developed for the first time the commercial fishing catches reconstruction of the Balearic Islands (Western Mediterranean) between 1950 and 2010, by adding non-reported components, including unreported landings and discards, to the official reported landing data. To back‑estimate historical unreported landings and discards, collaboration and information acquired from fishermen were essential, as gathered through interviews and observer programs of the Spanish Oceanographic Institute (IEO) on board commercial bottom trawling fleet. We estimated a total catch of 511,500 t over the period 1950‑2010, of which official landings represented 49% (around 248,000 t), followed by unreported catches (32%) and discards (20%). A decrease in unreported catches was observed during the period 1950-2010 (from 58% to 38%) due to a reduction of unreported landings, but substantial efforts are still required to improve the recordings of actual fishing catches. This work contributes to the global assessment of fisheries removals led by the Sea Around Us and aims to provide the basis for an improved management of the Balearic Islands and Mediterranean Sea fisheries