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Chemphyschem : a European Journal of... Mar 2024Osmium carbonyls are well known to form stable 18-electron complexes like Os(CO) , Os (CO) and Os (CO) having both bridging and terminal carbonyls. For osmium...
Osmium carbonyls are well known to form stable 18-electron complexes like Os(CO) , Os (CO) and Os (CO) having both bridging and terminal carbonyls. For osmium tetra-carbonyl, Os(CO) solid-state packing significantly alters the ground-state structure. The gas-phase stable see-saw geometry converts to a square-planar structure in solid state. Highly efficient intermolecular stacking between Os(CO) units assists this transformation. Each Os(CO) molecule is stacked in a staggered orientation with respect to each other. Pressure induces a [Xe]4f 5d 6s (S=2)→[Xe]4f 5d (S=0) electronic transition in osmium stabilize a square planar osmium tetra-carbonyl. Under the influence of isotropic pressure, the molecules not only come closer to each other but their relative orientations also get significantly altered. Calculations show that at P=1 GPa and above, the eclipsed orientation for the intermolecular stacking gets preferred over the staggered form. The staggered→eclipsed intermolecular stacking orientation under pressure is shown to be controlled by London dispersion interactions.
PubMed: 38087878
DOI: 10.1002/cphc.202300720 -
Inorganic Chemistry Jul 2024The article highlights the cooperative impact of azoheteroarenes [abbt: 2,2'-azobis(benzothiazole), L1-L3; bmpd: ()-1,2-bis(1-methyl-1-pyrazole-3-yl) diazene, L4] and...
The article highlights the cooperative impact of azoheteroarenes [abbt: 2,2'-azobis(benzothiazole), L1-L3; bmpd: ()-1,2-bis(1-methyl-1-pyrazole-3-yl) diazene, L4] and coligands [bpy: 2,2'-bipyridine; pap: 2-phenylazopyridine] in tuning radical (N-N) versus nonradical (N═N) states of L on selective Os-platforms in structurally/spectroscopically characterized monomeric []ClO-[]ClO and [](ClO)-[](ClO)/[](ClO)-[](ClO), respectively. The preferred -configuration of L in the complexes prevented obtaining ligand bridged dimeric species. It revealed that {Os(bpy)} facilitated the stabilization of both nonradical ([](ClO)-[](ClO)) and radical ([]ClO-[]ClO) states of L1/L2, while it delivered exclusively the radical form for L3 in []ClO. In contrast, {Os(pap)} generated radical states of L1-L3 in []ClO-[]ClO, respectively, without any alteration of the redox state of Os and azo (N═N) function of the pap coligand. The neutral state of L4 was, however, ascertained in [](ClO) or [](ClO) irrespective of the nature of the metal fragment {Os(bpy)} or {Os(pap)}, respectively. Switching between radical and nonradical forms of L in the complexes as a function L and coligand could be addressed based on their relative FMO (frontier molecular orbital) energies. Multiple close redox steps of the complexes extended a competitive electron transfer scenario between the redox active components including metal/L/bpy/pap, leading to delicate electronic forms in each case.
PubMed: 38870544
DOI: 10.1021/acs.inorgchem.4c01384 -
Heliyon Apr 2024Correlative light and electron microscopy (CLEM) combines light microscopy (LM) of fluorescent samples to ultrastructural analyses by electron microscopy (EM)....
Correlative light and electron microscopy (CLEM) combines light microscopy (LM) of fluorescent samples to ultrastructural analyses by electron microscopy (EM). Pre-embedding CLEM often suffers from inaccurate correlation between LM and EM modalities. Post-embedding CLEM enables precise registration of structures directly on EM sections, but requires fluorescent markers withstanding EM sample preparation, especially osmium tetroxide fixation, dehydration and EPON embedding. Most fluorescent proteins (FPs) lose their fluorescence during such conventional embedding (CE), but synthetic dyes represent promising alternatives as their stability exceeds those of FP. We analyzed various Janelia Fluor dyes and TMR conjugated to ligands for self-labeling enzymes, such as HaloTag, for fluorescence preservation after CE. We show that TMR, JF525, JF549, JFX549 and JFX554 retain fluorescence, with JFX549 and JFX554 yielding best results overall, also allowing integration of high-pressure freezing and freeze substitution. Furthermore, we found the recently published FP StayGold to resist CE, facilitating dual-fluorescence in-resin CLEM.
PubMed: 38560224
DOI: 10.1016/j.heliyon.2024.e28055 -
ACS Omega Apr 2024Kinesin spindle protein (KSP) inhibitors are one of the most promising anticancer agents developed in recent years. Herein, we report the synthesis of ispinesib-core...
Development of Half-Sandwich Ru, Os, Rh, and Ir Complexes Bearing the Pyridine-2-ylmethanimine Bidentate Ligand Derived from 7-Chloroquinazolin-4(3H)-one with Enhanced Antiproliferative Activity.
Kinesin spindle protein (KSP) inhibitors are one of the most promising anticancer agents developed in recent years. Herein, we report the synthesis of ispinesib-core pyridine derivative conjugates, which are potent KSP inhibitors, with half-sandwich complexes of ruthenium, osmium, rhodium, and iridium. Conjugation of 7-chloroquinazolin-4(3H)-one with the pyridine-2-ylmethylimine group and the organometallic moiety resulted in up to a 36-fold increased cytotoxicity with IC values in the micromolar and nanomolar range also toward drug-resistant cells. All studied conjugates increased the percentage of cells in the G/M phase, simultaneously decreasing the number of cells in the G/G phase, suggesting mitotic arrest. Additionally, ruthenium derivatives were able to generate reactive oxygen species (ROS); however, no significant influence of the organometallic moiety on KSP inhibition was observed, which suggests that conjugation of a KSP inhibitor with the organometallic moiety modulates its mechanism of action.
PubMed: 38680348
DOI: 10.1021/acsomega.3c10482 -
Journal of the American Chemical Society Jan 2024State-of-the-art methods in photoproximity labeling center on the targeted generation and capture of short-lived reactive intermediates to provide a snapshot of local...
State-of-the-art methods in photoproximity labeling center on the targeted generation and capture of short-lived reactive intermediates to provide a snapshot of local protein environments. Diazirines are the current gold standard for high-resolution proximity labeling, generating short-lived aryl(trifluoromethyl) carbenes. Here, we present a method to access aryl(trifluoromethyl) carbenes from a stable diazo source tissue-penetrable, deep red to near-infrared light (600-800 nm). The operative mechanism of this activation involves Dexter energy transfer from photoexcited osmium(II) photocatalysts to the diazo, thus revealing an aryl(trifluoromethyl) carbene. The labeling preferences of the diazo probe with amino acids are studied, showing high reactivity toward heteroatom-H bonds. Upon the synthesis of a biotinylated diazo probe, labeling studies are conducted on native proteins as well as proteins conjugated to the Os photocatalyst. Finally, we demonstrate that the conjugation of a protein inhibitor to the photocatalyst also enables selective protein labeling in the presence of spectator proteins and achieves specific labeling of a membrane protein on the surface of mammalian cells via a two-antibody photocatalytic system.
Topics: Animals; Red Light; Proteins; Methane; Diazomethane; Mammals
PubMed: 38165744
DOI: 10.1021/jacs.3c09545 -
Inorganic Chemistry Apr 2024The metal borides, HfMOsB (M = Mn, Fe, Co), which are the first Os-rich quaternary variants of the prolific TiCoB structure type, were investigated computationally and...
The metal borides, HfMOsB (M = Mn, Fe, Co), which are the first Os-rich quaternary variants of the prolific TiCoB structure type, were investigated computationally and experimentally. In their crystal structures, osmium builds a network of prisms, in which the other elements are located. The magnetic M elements are found in face-connected Os square prisms leading to M-chains with intra- and interchain distances of about 3.0 and 6.5 Å, respectively. Density functional theory (DFT) showed that magnetic ordering is hugely favored for M = Mn and Fe but only slightly favored for M = Co. Experimental investigations then confirmed and extended the DFT predictions as a metamagnetic behavior was found for the M = Mn and Fe phases, whereby the antiferromagnetic interactions ( = 19 and 90 K) found at low magnetic fields change to ferromagnetic at higher fields. A very broad transition ( = 45 K) is found for M = Co, suggesting spin-glass behavior for this phase. For M = Fe, a hard-magnet hysteresis at 5 K is found with a 40 kA/m coercivity, and even at room temperature, a significant hysteresis is found. This study paves the way for the discovery of Os-based magnets in this structure type and other intermetallics.
PubMed: 38625099
DOI: 10.1021/acs.inorgchem.4c00533 -
Scientific Reports Feb 2024Testing the hemocompatibility of medical devices after their interaction with blood entails the need to evaluate the activation of blood elements and the degree of their...
Testing the hemocompatibility of medical devices after their interaction with blood entails the need to evaluate the activation of blood elements and the degree of their coagulation and adhesion to the device surface. One possible way to achieve this is to use scanning electron microscopy (SEM). The aim was to develop a novel SEM-based method to assess the thrombogenic potential of medical devices and their adhesiveness to blood cells. As a part of this task, also find a convenient procedure of efficient and non-destructive sample fixation for SEM while reducing the use of highly toxic substances and shortening the fixation time. A polymeric surgical mesh was exposed to blood so that blood elements adhered to its surface. Such prepared samples were then chemically fixed for a subsequent SEM measurement; a number of fixation procedures were tested to find the optimal one. The fixation results were evaluated from SEM images, and the degree of blood elements' adhesion was determined from the images using ImageJ software. The best fixation was achieved with the May-Grünwald solution, which is less toxic than chemicals traditionally used. Moreover, manipulation with highly toxic osmium tetroxide can be avoided in the proposed procedure. A convenient methodology for SEM image analysis has been developed too, enabling to quantitatively evaluate the interaction of blood with the surfaces of various medical devices. Our method replaces the subjective assessment of surface coverage with a better-defined procedure, thus offering more precise and reliable results.
Topics: Microscopy, Electron, Scanning; Histological Techniques; Osmium Tetroxide
PubMed: 38409219
DOI: 10.1038/s41598-024-55136-z -
Angewandte Chemie (International Ed. in... May 2024The photocatalytic reduction of carbon dioxide (CO) represents an attractive approach for solar-energy storage and leads to the production of renewable fuels and...
The photocatalytic reduction of carbon dioxide (CO) represents an attractive approach for solar-energy storage and leads to the production of renewable fuels and valuable chemicals. Although some osmium (Os) photosensitizers absorb long wavelengths in the visible-light region, a self-photosensitized, mononuclear Os catalyst for red-light-driven CO reduction has not yet been exploited. Here, we discovered that the introduction of an Os metal to a PNNP-type tetradentate ligand resulted in the absorption of light with longer-wavelength (350-700 nm) and that can be applied to a panchromatic self-photosensitized catalyst for CO reduction to give mainly carbon monoxide (CO) with a total turnover number (TON) of 625 under photoirradiation (λ≥400 nm). CO photoreduction also proceeded under irradiation with blue (λ=405 nm), green (λ=525 nm), or red (λ=630 nm) light to give CO with >90 % selectivity. The quantum efficiency using red light was determined to be 12 % for the generation of CO. A catalytic mechanism is proposed based on the detection of intermediates using various spectroscopic techniques, including transient absorption, electron paramagnetic resonance, and UV/Vis spectroscopy.
PubMed: 38545689
DOI: 10.1002/anie.202403886 -
Frontiers in Endocrinology 2024Unlike white adipose tissue depots, bone marrow adipose tissue (BMAT) expands during caloric restriction (CR). Although mechanisms for BMAT expansion remain unclear,...
Deficiency of glucocorticoid receptor in bone marrow adipocytes has mild effects on bone and hematopoiesis but does not influence expansion of marrow adiposity with caloric restriction.
INTRODUCTION
Unlike white adipose tissue depots, bone marrow adipose tissue (BMAT) expands during caloric restriction (CR). Although mechanisms for BMAT expansion remain unclear, prior research suggested an intermediary role for increased circulating glucocorticoids.
METHODS
In this study, we utilized a recently described mouse model () to exclusively target bone marrow adipocytes (BMAds) for elimination of the glucocorticoid receptor (GR) (i.e. ) whilst maintaining GR expression in other adipose depots.
RESULTS
Mice lacking GR in BMAds ( ) and control mice ( ) were fed or placed on a 30% CR diet for six weeks. On a normal chow diet, tibiae of female mice had slightly elevated proximal trabecular metaphyseal bone volume fraction and thickness. Both control and mice had increased circulating glucocorticoids and elevated numbers of BMAds in the proximal tibia following CR. However, no significant differences in trabecular and cortical bone were observed, and quantification with osmium tetroxide and μCT revealed no difference in BMAT accumulation between control or mice. Differences in BMAd size were not observed between and control mice. Interestingly, mice had decreased circulating white blood cell counts 4 h into the light cycle.
DISCUSSION
In conclusion, our data suggest that eliminating GR from BMAd has minor effects on bone and hematopoiesis, and does not impair BMAT accumulation during CR.
Topics: Animals; Receptors, Glucocorticoid; Caloric Restriction; Mice; Adipocytes; Adiposity; Female; Hematopoiesis; Bone Marrow; Mice, Knockout; Bone and Bones; Mice, Inbred C57BL; Adipose Tissue; Male; Metabolism, Inborn Errors
PubMed: 38887268
DOI: 10.3389/fendo.2024.1397081 -
Science Progress 2024Termites cause a serious menace to wooden structures all over the world. They rely mostly on entozoic fauna residing in their hindgut for the digestion of cellulosic and...
Termites cause a serious menace to wooden structures all over the world. They rely mostly on entozoic fauna residing in their hindgut for the digestion of cellulosic and hemicellulosic materials. One of the ways to control termites is through their gut symbionts. The present study was designed to characterize the hindgut bacteria isolated from and . Furthermore, the growth inhibitory effect of eight tropical plant extracts was investigated to find out potential control agents for these bacterial isolates. The characterization of bacteria was carried out based on their morphology, Gram staining, biochemical and amplification of 16SrRNA gene. Amplified products were sequenced to confirm their relationship with bacterial isolates from termites of other regions. The growth inhibitory effect of ethanolic leaf extracts of eight plants was evaluated in an invitro agar well diffusion method. Qualitative and quantitative phytochemical analysis of the most effective plant was carried out to learn about bioactive agents. The results confirmed the presence of five bacteria from each termite species. The , and were common to both termites whereas and were found in only and harbor and in addition to common three ones. Among the plant extracts of , , , and , the > were found to have growth inhibitory effects with increasing concentrations from 100 to 2000 µg/mL. The biodiversity of the bacterial fauna is important for the biological control of termites. Leaf extracts of these medicinal plants can be used to control termite infestation in an environment-friendly manner to save huge economic loss.
Topics: Animals; Isoptera; Bacteria; Plant Extracts; Biodiversity
PubMed: 38490163
DOI: 10.1177/00368504241236026