Integrative phylogenetic, phylogeographic and morphological characterisation of the Unio crassus species complex reveals cryptic diversity with important conservation implications.

The global decline of freshwater mussels and their crucial ecological services highlight the need to understand their phylogeny, phylogeography and patterns of genetic diversity to guide conservation efforts. Such knowledge is urgently needed for Unio crassus, a highly imperilled species originally widespread throughout Europe and southwest Asia. Recent studies have resurrected several species from synonymy based on mitochondrial data, revealing U. crassus to be a complex of cryptic species. To address long-standing taxonomic uncertainties hindering effective conservation, we integrate morphometric, phylogenetic, and phylogeographic analyses to examine species diversity within the U. crassus complex across its entire range. Phylogenetic analyses were performed using cytochrome c oxidase subunit I (815 specimens from 182 populations) and, for selected specimens, whole mitogenome sequences and Anchored Hybrid Enrichment (AHE) data on âˆ¼ 600 nuclear loci. Mito-nuclear discordance was detected, consistent with mitochondrial DNA gene flow between some species during the Pliocene and Pleistocene. Fossil-calibrated phylogenies based on AHE data support a Mediterranean origin for the U. crassus complex in the Early Miocene. The results of our integrative approach support 12 species in the group: the previously recognised Unio bruguierianus, Unio carneus, Unio crassus, Unio damascensis, Unio ionicus, Unio sesirmensis, and Unio tumidiformis, and the reinstatement of five nominal taxa: Unio desectusstat. rev., Unio gontieriistat. rev., Unio mardinensisstat. rev., Unio nanusstat. rev., and Unio vicariusstat. rev. Morphometric analyses of shell contours reveal important morphospace overlaps among these species, highlighting cryptic, but geographically structured, diversity. The distribution, taxonomy, phylogeography, and conservation of each species are succinctly described.

A pH-Induced Switch in Human Glucagon-like Peptide-1 Aggregation Kinetics.

Aggregation and amyloid fibril formation of peptides and proteins is a widespread phenomenon. It has serious implications in a range of areas from biotechnological and pharmaceutical applications to medical disorders. The aim of this study was to develop a better understanding of the mechanism of aggregation and amyloid fibrillation of an important pharmaceutical, human glucagon-like peptide-1 (GLP-1). GLP-1 is a 31-residue hormone peptide that plays an important role regulating blood glucose levels, analogues of which are used for treatment of type 2 diabetes. Amyloid fibril formation of GLP-1 was monitored using thioflavin T fluorescence as a function of peptide concentration between pH 7.5 and 8.2. Results from these studies establish that there is a highly unusual pH-induced switch in GLP-1 aggregation kinetics. At pH 8.2, the kinetics are consistent with a nucleation-polymerization mechanism for fibril formation. However, at pH 7.5, highly unusual kinetics are observed, where the lag time increases with increasing peptide concentration. We attribute this result to the formation of off-pathway species together with an initial slow, unimolecular step where monomer converts to a different monomeric form that forms on-pathway oligomers and ultimately fibrils. Estimation of the pKa values of all the ionizable groups in GLP-1 suggest it is the protonation/deprotonation of the N-terminus that is responsible for the switch with pH. In addition, a range of biophysical techniques were used to characterize (1) the start point of the aggregation reaction and (2) the structure and stability of the fibrils formed. These results show that the off-pathway species form under conditions where GLP-1 is most prone to form oligomers.

Factors affecting the physical stability (aggregation) of peptide therapeutics.

The number of biological therapeutic agents in the clinic and development pipeline has increased dramatically over the last decade and the number will undoubtedly continue to increase in the coming years. Despite this fact, there are considerable challenges in the development, production and formulation of such biologics particularly with respect to their physical stabilities. There are many cases where self-association to form either amorphous aggregates or highly structured fibrillar species limits their use. Here, we review the numerous factors that influence the physical stability of peptides including both intrinsic and external factors, wherever possible illustrating these with examples that are of therapeutic interest. The effects of sequence, concentration, pH, net charge, excipients, chemical degradation and modification, surfaces and interfaces, and impurities are all discussed. In addition, the effects of physical parameters such as pressure, temperature, agitation and lyophilization are described. We provide an overview of the structures of aggregates formed, as well as our current knowledge of the mechanisms for their formation.

Intraocular delivery of oligonucleotides.

Anti-mRNA and particularly antisense oligonucleotides are molecules able to inhibit gene expression after intracellular penetration being potentially very interesting for the treatment of ocular diseases where growth factors are involved such as ocular scarring diseases or for the inhibition of viral multiplication. In most cases, the site of action of oligonucleotides has shown to be the posterior segment of the eye and these molecules are injected mainly by the intravitreal route. However, oligonucleotides are poorly stable in biological fluids, have a low intracellular penetration and are quickly eliminated form the vitreous. These issues request repeated administration of oligonucleotides which are able to induce severe damages to the retina. This is the reason why drug delivery systems were developed to improve the stability and intracellular penetration of oligonucleotides and, by sustained release, to increase their long term activity in the treatment of ocular diseases.