8 research outputs found
Blue Phosphorescent Zwitterionic Iridium(III) Complexes Featuring Weakly Coordinating <i>nido</i>-Carborane-Based Ligands
We report the development
of a new class of phosphorescent zwitterionic <i>bis</i>(heteroleptic) Ir(III) compounds containing pyridyl ligands
with weakly coordinating <i>nido</i>-carboranyl substituents.
Treatment of phenylpyridine-based Ir(III) precursors with <i>C</i>-substituted <i>ortho</i>-carboranylpyridines
in 2-ethoxyethanol results in a facile carborane deboronation and
the formation of robust and highly luminescent metal complexes. The
resulting <i>nido</i>-carboranyl fragments associate with
the cationic Ir(III) center through primarily electrostatic interactions.
These compounds phosphoresce at blue wavelengths (450–470 nm)
both in a poly(methyl methacrylate) (PMMA) matrix and in solution
at 77 K. These complexes display structural stability at temperatures
beyond 300 °C and quantum yields greater than 40%. Importantly,
the observed quantum yields correspond to a dramatic 10-fold enhancement
over the previously reported Ir(III) congeners featuring carboranyl-containing
ligands in which the boron cluster is covalently attached to the metal.
Ultimately, this work suggests that the use of a ligand framework
containing a weakly coordinating anionic component can provide a new
avenue for designing efficient Ir(III)-based phosphorescent emitters
Profiling the venom gland transcriptomes of Costa Rican snakes by 454 pyrosequencing
Background: A long term research goal of venomics, of applied importance for improving current antivenom
therapy, but also for drug discovery, is to understand the pharmacological potential of venoms. Individually or
combined, proteomic and transcriptomic studies have demonstrated their feasibility to explore in depth the
molecular diversity of venoms. In the absence of genome sequence, transcriptomes represent also valuable
searchable databases for proteomic projects.
Results: The venom gland transcriptomes of 8 Costa Rican taxa from 5 genera (Crotalus, Bothrops, Atropoides,
Cerrophidion, and Bothriechis) of pitvipers were investigated using high-throughput 454 pyrosequencing. 100,394
out of 330,010 masked reads produced significant hits in the available databases. 5.165,220 nucleotides (8.27%)
were masked by RepeatMasker, the vast majority of which corresponding to class I (retroelements) and class II
(DNA transposons) mobile elements. BLAST hits included 79,991 matches to entries of the taxonomic suborder
Serpentes, of which 62,433 displayed similarity to documented venom proteins. Strong discrepancies between the
transcriptome-computed and the proteome-gathered toxin compositions were obvious at first sight. Although the
reasons underlaying this discrepancy are elusive, since no clear trend within or between species is apparent, the
data indicate that individual mRNA species may be translationally controlled in a species-dependent manner. The
minimum number of genes from each toxin family transcribed into the venom gland transcriptome of each
species was calculated from multiple alignments of reads matched to a full-length reference sequence of each
toxin family. Reads encoding ORF regions of Kazal-type inhibitor-like proteins were uniquely found in Bothriechis
schlegelii and B. lateralis transcriptomes, suggesting a genus-specific recruitment event during the early-Middle
Miocene. A transcriptome-based cladogram supports the large divergence between A. mexicanus and A. picadoi,
and a closer kinship between A. mexicanus and C. godmani.
Conclusions: Our comparative next-generation sequencing (NGS) analysis reveals taxon-specific trends governing
the formulation of the venom arsenal. Knowledge of the venom proteome provides hints on the translation
efficiency of toxin-coding transcripts, contributing thereby to a more accurate interpretation of the transcriptome.
The application of NGS to the analysis of snake venom transcriptomes, may represent the tool for opening the
door to systems venomics.Universidad de Costa Rica, Instituto Clodomiro PicadoUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias de la Salud::Instituto Clodomiro Picado (ICP