In the continuation of previous studies on carbon‐rich meso‐tetraarylporphyrins featuring 2,7‐fluorene units at their periphery, the effect of changing the peripheral dendritic arms for linear arms ...on their oxygen‐photosensitizing ability, their fluorescence and their two‐photon absorption (2PA) properties is now analyzed. Thus, starburst porphyrins possessing up to twenty conjugated fluorenyl units were isolated and studied. More precisely, a series of five new free‐base porphyrins featuring fully conjugated arms incorporating an increasing number of fluorenyl groups connected via 1,2‐alkenyl spacers were synthesized, along with their Zn(II) complexes. Upon excitation in the arm‐centred π‐π* absorption band, an efficient energy transfer takes place from the peripheral fluorenyl units to the central porphyrin core, leading to intense red‐light emission and oxygen photosensitization by the latter. More interestingly, while the linear optical properties of these porphyrins were only slightly improved compared to those of their dendrimer analogues for photodynamic therapy (PDT) or fluorescence imaging, their 2PA cross‐sections were much more significantly boosted, evidencing the key role played by different structures on nonlinear optical properties. Finally, by comparison with other porphyrin‐based two‐photon photosensitizers reported in the literature, we show that these new “semi‐disconnected” starburst systems exhibit a remarkable trade‐off between intrinsic 2PA, fluorescence and oxygen photosensitization.
New Starburst porphyrins possessing up to twenty conjugated fluorenyl units have been synthesized. Their detailed oxygen‐photosensitizing ability, their fluorescence and their two‐photon absorption properties are discussed
A new family of conjugated meso‐tetraphenylporphyrin‐based dendrimers with four (TPP1, TPP2), eight (TPP3, TPP4, TPP5) and up to sixteen (TPP6) fluorenyl groups has been synthesized and fully ...characterized. These tetraphenylporphyrin‐cored dendrimers present peripheral alkynyl π‐conjugated dendrons with fluorenyl termini. The meso‐aryl rings of these porphyrins are functionalized either in para‐ (TPP1, TPP2, and TPP3) or meta‐positions (TPP4, TPP5, and TPP6). Their detailed luminescence properties are discussed in reference to two porphyrins lacking fluorenyl dendrons (TPP‐H1,2,3 and TPP‐H4,5,6). A strong dependence of their luminescence quantum yield and lifetime on their structures is stated, their nonlinear optical properties were also discussed.
Seeing porphyrins in a new light! A new family of conjugated meso‐tetraphenylporphyrin‐based dendrimers with fluorenyl arms has been synthesized (see figure). Their detailed luminescence properties and their nonlinear optical properties are discussed.
A series of three conjugated meso‐porphyrin dendrimers containing conjugated dendrons featuring 2,7‐fluorenyl groups, incorporating overall 8, 12, or 28 fluorenyl units have been synthesized and ...characterized. The photophysical properties of these new compounds were studied in the context of photodynamic therapy. The relevant linear and nonlinear optical properties were measured in organic media and useful structure–properties relationships were derived.
More than the sum of parts? Three conjugated meso‐porphyrin dendrimers containing conjugated dendrons featuring 2,7‐fluorenyl groups have been synthesized and characterized, and the photophysical properties of these new compounds were studied in the context of photodynamic therapy (see graphic).
Aim: To infer areas of endemism for the tribe Oryzomyini in South America by employing a database of species richness and geographical distribution, and to compare these results with areas of ...endemism and species richness proposed in the literature for other taxa. Location: We analysed specimens of the tribe Oryzomyini distributed throughout South and Central America, which are housed in European, North and South American museums and collections. Methods: We analysed 2768 occurrence records for 102 species of the tribe Oryzomyini using the NDM/VNDM algorithm and three different grid sizes to assess the possible effects of grid cell area on the results. Results: Using the overlap of consensus areas in South America, we identified three generalized areas of endemism for the Oryzomyini: north-western South America (NWSA), eastern South American (ESA), and northern South America (NSA); we also identified the Galapágos archipelago (GA) as an area of endemism. Main conclusions: Areas of endemism detected in the continental portion of South America include its three main mountain chains: the Andes Cordillera, the Guyanan Shields, and an area east of the Brazilian Shield named Serra do Mar. Each of these regions encompasses many different types of vegetation, and the species richness and composition of the areas of endemism of the tribe are directly related to this environmental diversity. Different grid sizes affected the distributional heterogeneity of the consensus areas. The smallest grid cell size identified mainly Andean areas, which contain a higher number of more exclusive species in a small area along a steep elevational gradient. In contrast, the largest grid size identified areas of endemism along an environmental gradient that co-varied with latitude and longitude. The identified areas of endemism are corroborated by previous studies on other taxa.
A series of free base and Zn(II) phthalocyanines featuring fluorenyl antennae linked by methoxy or oxo bridges to the phthalocyanine core (Pc) were synthesized and characterized. Selected linear and ...nonlinear (two-photon absorption) optical properties of these new compounds were subsequently studied. As previously observed for related porphyrin dendrimers bearing 2-fluorenyl peripheral dendrons, an efficient energy transfer occurs from the peripheral antennae to the central phthalocyanine core following excitation in the fluorenyl-based π-π* absorption band of these chromophores. Once excited, these compounds relax to the ground state, mostly by emitting intense red light or by undergoing intersystem crossing. As a result, the tetrafunctionalized Zn(II) phthalocyanines are fluorescent, but can also efficiently photosensitize molecular oxygen in tetrahydrofurane (THF), forming singlet oxygen with nearly comparable yields to bare Zn(II) phthalocyanine (
). In comparison with the latter complex, the positive role of the fluorenyl-containing antennae on one- and two-photon brightness (2PA) is presently demonstrated when appended in peripheral (β) position to the phthalocyanine core. Furthermore, when compared to known porphyrin analogues, the interest in replacing the porphyrin by a phthalocyanine as the central core to obtain more fluorescent two-photon oxygen photosensitizers is clearly established. As such, this contribution paves the way for the future development of innovative biphotonic photosensitizers usable in theranostics.
Star-shaped hydrophobic porphyrins, acting as powerful fluorescent two-photon photosensitizers for oxygen in organic solvents, can easily be loaded into PMLABe polymeric nanoparticles at various ...concentrations. In this contribution, the performance of these porphyrin-containing nanoparticles in terms of photodynamic therapy (PDT) is compared to those of the corresponding water-soluble porphyrin analogues when irradiated in MCF-7 cancer cells. While quite promising results are obtained for performing PDT with these nanoparticles, validating this approach as a mean for using more easily accessible and less expensive photosensitizers, from a synthetic perspective, we also show that their luminescence can still be used for bioimaging purposes in spite of their confinement in the nanoparticles, validating also the use of these nano-objects for theranostic purposes.
Mate choice for compatible genes is often based on genes of the major histocompatibility complex (MHC). Although MHC‐based mate choice is commonly observed in female choice, male mate choice remains ...elusive. In particular, if males have intense paternal care and are thus the choosing sex, male choice for females with dissimilar MHC can be expected. Here, we investigated whether male mate choice relies on MHC class I genes in the sex‐role reversed pipefish Syngnathus typhle. In a mate choice experiment, we determined the relative importance of visual and olfactory cues by manipulating visibility and olfaction. We found that pipefish males chose females that maximize sequence‐based amino acid distance between MHC class I genotypes in the offspring when olfactory cues were present. Under visual cues, large females were chosen, but in the absence of visual cues, the choice pattern was reversed. The use of sex‐role reversed species thus revealed that sexual selection can lead to the evolution of male mate choice for MHC class I genes.
The release of radionuclides from spent nuclear fuel upon contact with water is a central issue for the assessment of the safety of geological disposal concepts. Several studies have been conducted ...aiming at understanding matrix dissolution as well as the rapid/instant release of radionuclides separated from the UO2 matrix; there are however questions remaining regarding how higher burn-up affects the amount of fission products segregated to the fuel-cladding gap and grain boundaries.
In this study we have performed aerated fuel corrosion and leaching experiments using spent nuclear fuels with a range of burnups, from ∼52 to ∼70 MWd/KgU. The samples have been prepared in different manners in order to investigate the release of the segregated fission products from the gap and the grain boundaries. Thus, the fuel samples are prepared either as segments with the cladding attached, as fragments without cladding, or as milled powder. The fuel samples are leached in aqueous solution in aerated conditions and the radionuclide release is monitored during several contact periods for up to five years total leaching time.
The results from the leaching of fuel segments reveal congruent release of e.g. europium and neodymium whereas the release of those elements was lower than the U-238 release for the fragment samples. Potential explanations for this are discussed in the paper.
The results show that the release rates of elements segregated from the fuel matrix were in general found to be lower from segments samples as compared to fragment samples, which can be attributed to the closed fuel-cladding gap inhibiting the exposure of the gap inventory to water for the high burnup fuels used in this study.
Leaching of fuel powder (78 MWd/kgU local BU) by simultaneous grinding and leaching showed a fractional release of Cs-137 and I-129 of 1.5% and 1.8% respectively.
In this issue of Molecular Cell, Tsuchida et al. (2022) present a successful structure-guided effort in improving genome-editing efficiencies of CRISPR-CasX from Deltaproteobacteria (DpbCasX) and ...Planctomycetes (PlmCasX). Engineered variants that stabilize the active conformational state improved the catalytic efficiency by ∼10–20 fold in vitro and mean-editing efficiency by ∼2–3 fold in human cells.
In this issue of Molecular Cell, Tsuchida et al. (2022) present a successful structure-guided effort in improving genome-editing efficiencies of CRISPR-CasX from Deltaproteobacteria (DpbCasX) and Planctomycetes (PlmCasX). Engineered variants that stabilize the active conformational state improved the catalytic efficiency by ∼10–20 fold in vitro and mean-editing efficiency by ∼2–3 fold in human cells.
The red flour beetle, Tribolium castaneum, secretes quinones that control the microbial flora in the surrounding environment. These secretions act as an external immune defence that provides ...protection against pathogens. At high concentrations, however, these secretions are harmful to the host itself, and selection may thus have optimized the level of expression under natural conditions. Here, we show that the expression of external immunity responded to selection during experimental evolution within a few generations. At the same time, one component of internal immune defence (phenoloxidase activity) was compromised in beetles selected for either high or low external defences. Intriguingly, offspring protection against a natural pathogen was reduced in flour obtained from beetle lines selected for low amounts of secretions. Altogether, this suggests that external and internal immune defences work together efficiently under natural conditions, whereas every manipulation on the side of external immune defence comes with costs to the internal immune defence.
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