Convergent Total Synthesis of Yaku'amide†A.

Total synthesis of the anticancer peptide natural product yaku'amide A is reported. Its ß-tert-hydroxy amino acids were prepared by regioselective aminohydroxylation involving a chiral mesyloxycarbamate reagent. Stereospecific construction of the E- and Z-ΔIle residues was accomplished through a one-pot reaction featuring anti dehydration, azide reduction, and O→N acyl transfer. Alkene isomerization was negligible during this process. These methods enabled a highly convergent and efficient synthetic route to the natural product.

Close association between paralogous multiple isomiRs and paralogous/orthologues miRNA sequences implicates dominant sequence selection across various animal species.

MicroRNAs (miRNAs) are crucial negative regulators of gene expression at the post-transcriptional level. Next-generation sequencing technologies have identified a series of miRNA variants (named isomiRs). In this study, paralogous isomiR assemblies (from the miRNA locus) were systematically analyzed based on data acquired from deep sequencing data sets. Evolutionary analysis of paralogous (members in miRNA gene family in a specific species) and orthologues (across different animal species) miRNAs was also performed. The sequence diversity of paralogous isomiRs was found to be similar to the diversity of paralogous and orthologues miRNAs. Additionally, both isomiRs and paralogous/orthologues miRNAs were implicated in 5' and 3' ends (especially 3' ends), nucleotide substitutions, and insertions and deletions. Generally, multiple isomiRs can be produced from a single miRNA locus, but most of them had lower enrichment levels, and only several dominant isomiR sequences were detected. These dominant isomiR groups were always stable, and one of them would be selected as the most abundant miRNA sequence in specific animal species. Some isomiRs might be consistent to miRNA sequences in some species but not the other. Homologous miRNAs were often detected in similar isomiR repertoires, and showed similar expression patterns, while dominant isomiRs showed complex evolutionary patterns from miRNA sequences across the animal kingdom. These results indicate that the phenomenon of multiple isomiRs is not a random event, but rather the result of evolutionary pressures. The existence of multiple isomiRs enables different species to express advantageous sequences in different environments. Thus, dominant sequences emerge in response to functional and evolutionary pressures, allowing an organism to adapt to complex intra- and extra-cellular events.

Clima y temperatura sub-superficial del mar en Bahía Culebra, Golfo de Papagayo, Costa Rica / Climate and subsurface sea temperature in Bahía Culebra, Costa Rica

Climate and subsurface sea temperature in Bahía Culebra, Costa Rica. Bahía Culebra, Golfo de Papagayo, Costa Rica is a seasonal upwelling area. To determine the relationship of climate and the subsurface temperature variability at Bahía Culebra, we analyzed nine records of sea subsurface temperature from the Bay, continuously recorded from 1998 to 2010. The analysis characterized the annual cycle and explored the influence of different climate variability sources on the subsurface sea temperature and air temperature recorded in Bahía Culebra. Data from an automatic meteorological station in the bay were studied, obtaining the annual and daily cycle for air surface temperature and wind speed. Sea surface temperature (SST) trend from 1854 to 2011 was calculated from reanalysis for the region that coverts 9-11°N, 85-87°W. Because of the positive SST trend identified in this region, results showed that annual and daily cycles in Bahía Culebra should be studied under a warming scenario since 1854, that is coherent with the global warming results and its climate variability is influenced by El Niño-Southern Oscillation (ENSO) in the Equatorial Pacific and by atmospheric forcing triggered by climate variability with Atlantic Ocean origin, because warm (cold) events in Bahía Culebra tend to occur in concordance with positive & negative (negative & positive) anomalies in Niño 3.4 (NAO) index.

Bahía Culebra, Golfo de Papagayo, Costa Rica es una región de afloramiento estacional. Para determinar la relación entre el clima y la variabilidad de la temperatura sub-superficial, se analizaron los registros de la temperatura sub-superficial del mar de nueve estaciones localizadas en la Bahía. El análisis permitió caracterizar su ciclo anual y explorar su relación con fuentes de variabilidad climática que influencian el clima regional para el periodo 1998-2010. Los resultados se contextualizaron usando además los datos de una estación meteorológica automática que funcionó en la bahía junto con el registro de la temperatura superficial del mar para una rejilla que cubre la región de 9-11°N, 85-87°W, para el periodo 1854-2011. Debido a la tendencia positiva encontrada en la región para la temperatura superficial del mar, se concluye que los resultados mostrados asociados a los ciclos anuales y diarios en Bahía Culebra deben ser interpretados bajo un escenario de cambio climático, asociado a un calentamiento ocurrido desde 1854, además coherente con lo observado globalmente, y que su variabilidad climática está influenciada no sólo por aquella ligada a la de El Niño-Oscilación del Sur, en el Pacífico Ecuatorial, sino también por influencias de tipo atmosférico relacionadas con la variabilidad en el Océano Atlántico, debido a que los eventos cálidos (fríos) en Bahía Culebra tienden a ocurrir en concordancia con anomalías positivas y negativas (negativas y positivas) de los índices Niño 3.4 y OAN, respectivamente.