Synthesis and biological activity of novel small peptides with aminophosphonates moiety as NOP receptor ligands

The aim of the present study was the synthesis and the biological screening of new analogs of Ac-RYYRWK-NH₂, modified at the N-terminal with 1-[(methoxyphosphono)methylamino]cycloalkanecarboxylic acids. The four newly synthesized ligands for the nociceptin/orphanin FQ (N/OFQ) receptor (NOP) have been prepared by solid-phase peptide synthesis—Fmoc-strategy. These compounds were tested for agonistic activity in vitro on electrically stimulated smooth-muscle preparations isolated from vas deferens of Wistar rats. Our data showed that substitution of Arg at position 1 with aminophosphonates moiety decreased significantly the affinity of ligands to the NOP receptor. Furthermore, the enlargement of the cycle (with 5–8 carbon atoms) additionally diminished both the activity and the selectivity for NOP-receptor.     

PTCH1 gene polymorphisms in ovarian tumors: Potential protective role of c.3944T allele

In this study we investigated the types and role of different genetic changes of PTCH1 gene in three different types of ovarian tumors: carcinomas, fibromas and dermoids. LOH of the PTCH1 region was detected in 27.3% ovarian carcinoma samples, 18.18% ovarian fibroma samples and 55.56% ovarian dermoid samples. No point mutations were detected in any of the three types of ovarian tumors. SNP c.3944C>T showed significant differences between ovarian carcinoma and control samples with the minor T allele being significantly higher in controls compared to ovarian carcinomas. Interestingly, a new polymorphism c.−1184G>A was found only in tumor samples and further analyses should be performed in order to elucidate its potential role in ovarian tumors.     

Mining citizen science data to explore stopover sites and spatiotemporal variation in migration patterns of the red-footed falcon

Citizen science data have already been used to effectively address questions regarding migration, a fundamental stage in the life history of birds. In this study, we use data from eBird and from 3 additional regional citizen science databases to describe the migration routes and timing of the red-footed falcon Falco vespertinus in the Mediterranean region across 8 years (2010–2017). We further examine the seasonal and yearly variation in migration patterns and explore sites used during the species migration. Our results suggest that the autumn passage is spatially less variable and temporally more consistent among years than in spring and that birds migrate faster in spring than in autumn. The species seems to be more prevalent along the Central Mediterranean during spring migration, probably as a result of the clockwise loop migration that red-footed falcons perform. There was a high variation in annual median migration dates for both seasons as well as in migration routes across years and seasons. Higher variation was exhibited in the longitudinal component thus indicating flexibility in migration routes. In addition, our results showed the species’ preference for lowlands covered with cropland and mosaics of cropland and natural vegetation as stopover sites during migration. Stopover areas predicted from our distribution modeling highlight the importance of the Mediterranean islands as stopover sites for sea-crossing raptors, such as the red-footed falcon. This study is the first to provide a broad-scale spatiotemporal perspective on the species migration across seasons, years and flyways and demonstrates how citizen science data can inform future monitoring and conservation strategies.     

Synthesis and changes in affinity for NOP and opioid receptors of novel hexapeptides containing β2-tryptophan analogues

We report the synthesis and the biological activity of new analogues of Ac-RFMWMK-NH₂ and Ac-RYYRWK-NH₂, modified in position 4 and 5, respectively, with incorporation of newly synthesized β²-tryptophan analogues. Trp was substituted by the (S)-2-(1-methyl-1H-indol-3-yl)propionic residue or by (S)-2-(5-methoxy-1H-indol-3-yl)propionic residue. The biological activity (pEC₅₀ and E_max) of these compounds was tested on electrically stimulated preparations of rat vas deferens. The 5-methoxy β-tryptophan group reverses the affinity of the compounds.     

Redox transients of P680 associated with the incremental chlorophyll‐a fluorescence yield rises elicited by a series of saturating flashes in diuron‐treated photosystem II core complex of Thermosynechococcus vulcanus

Recent chlorophyll‐a fluorescence yield measurements, using single‐turnover saturating flashes (STSFs), have revealed the involvement of a rate‐limiting step in the reactions following the charge separation induced by the first flash. As also shown here, in diuron‐inhibited PSII core complexes isolated from Thermosynechococcus vulcanus the fluorescence maximum could only be reached by a train of STSFs. In order to elucidate the origin of the fluorescence yield increments in STSF series, we performed transient absorption measurements at 819 nm, reflecting the photooxidation and re‐reduction kinetics of the primary electron donor P680. Upon single flash excitation of the dark‐adapted sample, the decay kinetics could be described with lifetimes of 17 ns (～50%) and 167 ns (～30%), and a longer‐lived component (～20%). This kinetics are attributed to re‐reduction of P680^?+ by the donor side of PSII. In contrast, upon second‐flash (with Δt between 5 μs and 100 ms) or repetitive excitation, the 819 nm absorption changes decayed with lifetimes of about 2 ns (～60%) and 10 ns (～30%), attributed to recombination of the primary radical pair P680^?+Pheo^?–, and a small longer‐lived component (～10%). These data confirm that only the first STSF is capable of generating stable charge separation – leading to the reduction of Q_A; and thus, the fluorescence yield increments elicited by the consecutive flashes must have a different physical origin. Our double‐flash experiments indicate that the rate‐limiting steps, detected by chlorophyll‐a fluorescence, are not correlated with the turnover of P680.     

3D immuno-confocal image reconstruction of fibroblast cytoskeleton and nucleus architecture

Computational models of cellular structures generally rely on simplifying approximations and assumptions that limit biological accuracy. This study presents a comprehensive image processing pipeline for creating unified three-dimensional (3D) reconstructions of the cell cytoskeletal networks and nuclei. Confocal image stacks of these cellular structures were reconstructed to 3D isosurfaces (Imaris), then tessellations were simplified to reduce the number of elements in initial meshes by applying quadric edge collapse decimation with preserved topology boundaries (MeshLab). Geometries were remeshed to ensure uniformity (Instant Meshes) and the resulting 3D meshes exported (ABAQUS) for downstream application. The protocol has been applied successfully to fibroblast cytoskeletal reorganisation in the scleral connective tissue of the eye, under mechanical load that mimics internal eye pressure. While the method herein is specifically employed to reconstruct immunofluorescent confocal imaging data, it is also more widely applicable to other biological imaging modalities where accurate 3D cell structures are required.     

Structural insights into the binding of small ligand molecules to a G-quadruplex DNA located in the HIV-1 promoter

Targeting guanine (G)-rich DNA sequences, folded into non-canonical G-quadruplex (G4) structures, by small ligand molecules is a promising strategy for gene therapy of various diseases. There is experimental proposal that, among eight studied ligands, nitidine chloride – NC and a benzo phenanthridine derivative – BPD have the highest binding affinity for such a sequence (5′-T¹G²G³C⁴C⁵T⁶G⁷G⁸G⁹C¹⁰G¹¹G¹²G¹³A¹⁴C¹⁵T¹⁶G¹⁷G¹⁸G¹⁹?3′) in the HIV-1 promoter, indicating that an anti-HIV-1 prodrug may regulate the expression of the promoter. Herein, this experimental indication is elaborated by using molecular docking simulations and by characterizing the modes of binding of the eight natural molecules to the particular G4. Moreover, the configurational entropy, as an upper bound of the true entropy contribution to the free energy in noncovalent binding, is employed to see into the structural changes experienced by the G4-DNA upon ligand binding. For various parts (complete structure, backbone, system of all bases, bases of G-tetrads) of the G4-DNA structure, a subtle molecular dynamics (MD) is exploited to determine the change of asymptotic (for infinitely long MD simulation) configurational entropy, being the thermodynamic consequence of DNA flexibility change upon complex formation. While NC increases rigidity of G4 (mainly through the system of all nucleobases), BPD increases flexibility of G4 (more than 50% stems from the sugar-phosphate backbone). These insights are further dissected and substantiated by considering the configurational entropy contributions at the level of individual base pairs making the two G-tetrads (G²G⁷G¹³G¹⁷ and G³G⁸G¹²G¹⁸) and by exploring the estimates of the total intra-base pair and inter-base pair entropies. This work makes the structural origin of enhanced stability of G4-DNA more certain – useful information when attempting to design optimal G4-DNA binders.