A Photoswitchable Metallocycle Based on Azobenzene: Synthesis, Characterization, and Ultrafast Dynamics.

The novel photoswitchable ligand 3,3'-Azobenz(metPA)2 (1) is used to prepare a [Cu2(1)2](BF4)2 metallocycle (2), whose photoisomerization was characterized using static and time-resolved spectroscopic methods. Optical studies demonstrate the highly quantitative and reproducible photoinduced cyclic E/Z switching without decay of the complex. Accordingly and best to our knowledge, [Cu2(1)2](BF4)2 constitutes the first reversibly photoswitchable (3d)-metallocycle based on azobenzene. The photoinduced multiexponential dynamics in the sub-picosecond to few picosecond time domain of 1 and 2 have been assessed. These ultrafast dynamics as well as the yield of the respective photostationary state (PSSZ = 65 %) resemble the behavior of archetypical azobenzene. Also, the innovative pump-probe laser technique of gas phase transient photodissociation (τ-PD) in a mass spectrometric ion trap was used to determine the intrinsic relaxation dynamics for the isolated complex. These results are consistent with the results from femtosecond UV/Vis transient absorption (fs-TA) in solution, emphasizing the azobenzene-like dynamics of 2. This unique combination of fs-TA and τ-PD enables valuable insights into the prevailing interplay of dynamics and solvation. Both analyses (in solution and gas phase) and quantum chemical calculations reveal a negligible effect of the metal coordination on the switching mechanism and electronic pathway, which suggests a non-cooperative isomerization process.

Cooperativity-Driven Reactivity of a Dinuclear Copper Dimethylglyoxime Complex.

In this report, we present the dinuclear copper(II) dimethylglyoxime (H2 dmg) complex [Cu2 (H2 dmg)(Hdmg)(dmg)]+ (1), which, in contrast to its mononuclear analogue [Cu(Hdmg)2 ] (2), is subject to a cooperativity-driven hydrolysis. The combined Lewis acidity of both copper centers increases the electrophilicity of the carbon atom in the bridging µ2 -O-N=C-group of H2 dmg and thus, facilitates the nucleophilic attack of H2 O. This hydrolysis yields butane-2,3-dione monoxime (3) and NH2 OH that, depending on the solvent, is then either oxidized or reduced. In ethanol, NH2 OH is reduced to NH4 + , yielding acetaldehyde as the oxidation product. In contrast, in CH3 CN, NH2 OH is oxidized by CuII to form N2 O and [Cu(CH3 CN)4 ]+ . Herein are presented the combined synthetic, theoretical, spectroscopic and spectrometric methods that indicate and establish the reaction pathway of this solvent-dependent reaction.

Tight association of autophagy and cell cycle in leukemia cells.

BACKGROUND: Autophagy plays an essential role in maintaining cellular homeostasis and in the response to cellular stress. Autophagy is also involved in cell cycle progression, yet the relationship between these processes is not clearly defined. RESULTS: In exploring this relationship, we observed that the inhibition of autophagy impaired the G2/M phase-arresting activity of etoposide but enhanced the G1 phase-arresting activity of palbociclib. We further investigated the connection of basal autophagy and cell cycle by utilizing the autophagosome tracer dye Cyto-ID in two ways. First, we established a double-labeling flow-cytometric procedure with Cyto-ID and the DNA probe DRAQ5, permitting the cell cycle phase-specific determination of autophagy in live cells. This approach demonstrated that different cell cycle phases were associated with different autophagy levels: G1-phase cells had the lowest level, and G2/M-phase cells had the highest one. Second, we developed a flow-cytometric cell-sorting procedure based on Cyto-ID that separates cell populations into fractions with low, medium, and high autophagy. Cell cycle analysis of Cyto-ID-sorted cells confirmed that the high-autophagy fraction contained a much higher percentage of G2/M-phase cells than the low-autophagy fraction. In addition, Cyto-ID-based cell sorting also proved to be useful for assessing other autophagy-related processes: extracellular flux analysis revealed metabolic differences between the cell populations, with higher autophagy being associated with higher respiration, higher mitochondrial ATP production, and higher glycolysis. CONCLUSION: This work provides clear evidence of high autophagy in G2/M-phase cells by establishing a novel cell sorting technique based on Cyto-ID.

A Cyclometalated NHC Iridium Complex Bearing a Cationic (η5 -Cyclopentadienyl)(η6 -phenyl)iron Backbone*.

Nucleophilic substitution of [(η5 -cyclopentadienyl)(η6 -chlorobenzene)iron(II)] hexafluorophosphate with sodium imidazolate resulted in the formation of [(η5 -cyclopentadienyl)(η6 -phenyl)iron(II)]imidazole hexafluorophosphate. The corresponding dicationic imidazolium salt, which was obtained by treating this imidazole precursor with methyl iodide, underwent cyclometallation with bis[dichlorido(η5 -1,2,3,4,5-pentamethylcyclopentadienyl]iridium(III) in the presence of triethyl amine. The resulting bimetallic iridium(III) complex is the first example of an NHC complex bearing a cationic and cyclometallated [(η5 -cyclopentadienyl)(η6 -phenyl)iron(II)]+ substituent. As its iron(II) precursors, the bimetallic iridium(III) complex was fully characterized by means of spectroscopy, elemental analysis and single crystal X-ray diffraction. In addition, it was investigated in a catalytic study, wherein it showed high activity in transfer hydrogenation compared to its neutral analogue having a simple phenyl instead of a cationic [(η5 -cyclopentadienyl)(η6 -phenyl)iron(II)]+ unit at the NHC ligand.

Duration of SARS-CoV-2 RNA detection in COVID-19 patients in home isolation, Rhineland-Palatinate, Germany, 2020 - an interval-censored survival analysis.

We analysed consecutive RT-qPCR results of 537 symptomatic coronavirus disease (COVID-19) patients in home quarantine. Respectively 2, 3, and 4 weeks after symptom onset, 50%, 25% and 10% of patients had detectable RNA from severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). In patients with mild COVID-19, RNA detection is likely to outlast currently known periods of infectiousness by far and fixed time periods seem more appropriate in determining the length of home isolation than laboratory-based approaches.

The sirtuin 1/2 inhibitor tenovin-1 induces a nonlinear apoptosis-inducing factor-dependent cell death in a p53 null Ewing's sarcoma cell line.

The sirtuin 1/2 inhibitor tenovin-1 activates p53 and may have potential in the management of cancer. Here, we investigated the responsiveness of Ewing's sarcoma cells to tenovin-1. We examined its effects in two Ewing's sarcoma cell lines with different p53 status, i.e. in p53 wild-type and p53 null cells. Effects were assessed by flow cytometric analyses of cell death, mitochondrial membrane depolarization and reactive oxygen species (ROS) generation, by caspase 3/7 activity measurement, by mRNA expression profiling and by immunoblotting. Tenovin-1 elicited caspase-mediated cell death in p53 wild-type cells, but caspase-independent cell death in p53 null cells. Remarkably, it induced a nonlinear concentration response in the latter: low concentrations of tenovin-1 were much more effective than were higher concentrations. Tenovin-1's effects in p53 null cells involved gene expression changes of Bcl-2 family members, mitochondrial membrane depolarization, nuclear translocation of apoptosis-inducing factor, ROS formation and DNA damage; all these effects followed a bell-shaped pattern. In conclusion, our results provide new insights into tenovin-1's mode of action by demonstrating that it can induce different pathways of cell death.

CF2H, a Hydrogen Bond Donor.

The CF2H group, a potential surrogate for the OH group, can act as an unusual hydrogen bond donor, as confirmed by crystallographic, spectroscopic, and computational methods. Here, we demonstrate the bioisosterism of the OH and CF2H groups and the important roles of CF2-H···O hydrogen bonds in influencing intermolecular interactions and conformational preferences. Experimental evidence, corroborated by theory, reveals the distinctive nature of CF2H hydrogen bonding interactions relative to their normal OH hydrogen bonding counterparts.

A Reinterpretation of the Crystal Structure Analysis of [K(crypt-222)]+ CF3- : No Proof for the Trifluoromethanide Ion.

Critically discussing and, if necessary, questioning results presented by other researchers has always been a vitally important process in science. Only through fruitful discourse does science arrive at broadly accepted hypotheses that finally become what we accept as scientific truth. In the spirit of this time-honored tradition, we have examined the crystal structure as well as X-ray diffraction data of the proposed compound [K(crypt-222)]+ CF3- , which has recently been published. We arrived at the conclusion that the claim of the authors to have successfully and unambiguously characterized the ionic [K(crypt-222)]+ CF3- through single-crystal X-ray diffraction is not sustainable. Even though it is possible that the original authors have indeed encountered the proposed species, the purpose of this report is to point out that the original authors cannot use the presented crystallographic data and model as proof for the existence of [K(crypt-222)]+ CF3- . The reason for our conclusion is two-fold: firstly, the crystal structure was not refined to established standards of good crystallographic practice and secondly, even if best practices of structure determination are employed, the submitted diffraction data do not allow establishing conclusively the true nature of the compound at hand. Recognizing that this gives charge unbalance we have not resolved, we nevertheless suggest an alternative molecular model, [K(crypt-222)]⋅CHF3 , to demonstrate the ambiguity of the diffraction data submitted by the original authors. However, because of this ambiguity, it is important to point out that the purpose of this report is not (and cannot be) the determination of the true nature of the compound at hand; we would merely like to demonstrate that an alternative interpretation of the original diffraction data is possible and, hence, that the conclusion drawn by the original authors is not unambiguously supported by their own data.

Redox Behavior of a Dinuclear Ruthenium(II) Complex Bearing an Uncommon Bridging Ligand: Insights from High-Pressure Electrochemistry.

A dinuclear ruthenium complex bridged by 2,3,5,6-pyrazinetetracarboxylic acid (µ-LH22-) was synthesized and characterized by X-ray crystallography, cyclic voltammetry under ambient and elevated pressures, electron paramagnetic resonance (EPR) and UV/vis-NIR (NIR = near-infrared) spectroelectrochemistry, pulse radiolysis, and computational methods. We probed for the first time in the field of mixed-valency the use of high-pressure electrochemical methods. The investigations were directed toward the influence of the protonation state of the bridging ligand on the electronic communication between the ruthenium ions, since such behavior is interesting in terms of modulating redox chemistry by pH. Starting from the [RuII(µ-LH22-)RuII]0 configuration, which shows an intense metal-to-ligand charge transfer absorption band at 600 nm, cyclic voltammetry revealed a pH-independent, reversible one-electron reduction and a protonation-state-dependent (proton coupled electron transfer, PCET) reversible oxidation. Deeper insight into the electrode reactions was provided by pressure-dependent cyclic voltammetry up to 150 MPa, providing insight into the conformational changes, the protonation state, and the environment of the molecule during the redox processes. Spectroelectrochemical investigations (EPR, UV/vis-NIR) of the respective redox reactions suggest a ligand-centered radical anion [RuII(µ-LH2•3-)RuII]- upon reduction (EPR Δg = 0.042) and an ambiguous, EPR-silent one-electron oxidized state. In both cases, the absence of the otherwise typical broad intervalence charge transfer bands in the NIR region for mixed-valent complexes support the formulation as radical anionic bridged compound. However, on the basis of high-pressure electrochemical data and density functional theory calculations the one-electron oxidized form could be assigned as a charge-delocalized [RuII.5(µ-LH22-)RuII.5]+ valence tautomer rather than [RuIII(µ-LH2•3-)RuIII]+. Deprotonation of the bridging ligand causes a severe shift of the redox potential for the metal-based oxidation toward lower potentials, yielding the charge-localized [RuIII(µ-LH3-)RuII]0 complex. This PCET process is accompanied by large intrinsic volume changes. All findings are supported by computational methods (geometry optimization, spin population analysis). For all redox processes, valence alternatives are discussed.

Tuning the Diiron Core Geometry in Carboxylate-Bridged Macrocyclic Model Complexes Affects Their Redox Properties and Supports Oxidation Chemistry.

We introduce a novel platform to mimic the coordination environment of carboxylate-bridged diiron proteins by tethering a small, dangling internal carboxylate, (CH2)nCOOH, to phenol-imine macrocyclic ligands (H3PIMICn). In the presence of an external bulky carboxylic acid (RCO2H), the ligands react with [Fe2(Mes)4] (Mes = 2,4,6-trimethylphenyl) to afford dinuclear [Fe2(PIMICn)(RCO2)(MeCN)] (n = 4-6) complexes. X-ray diffraction studies revealed structural similarities between these complexes and the reduced diiron active sites of proteins such as Class I ribonucleotide reductase (RNR) R2 and soluble methane monooxygenase hydroxylase. The number of CH2 units of the internal carboxylate arm controls the diiron core geometry, affecting in turn the anodic peak potential of the complexes. As functional synthetic models, these complexes facilitate the oxidation of C-H bonds in the presence of peroxides and oxo transfer from O2 to an internal phosphine moiety.

Achieving Reversible Sensing of Nitroxyl by Tuning the Ligand Environment of Azamacrocyclic Copper(II) Complexes.

To elucidate the factors that impart selectivity for nitroxyl (HNO) over nitric oxide (NO), thiols, and H2S in metal-based fluorescent probes, we investigated five Cu(II)-cyclam (14-N4) derivatives. Upon exposure to NO gas at pH 7, no changes occur in the UV-vis spectra of any of the complexes. Addition of Angeli's salt to generate HNO promotes reduction of Cu(II) only in the case of [Cu(II)(14-N4-Ts)(OTf)2], which has the most positive reduction potential of the series. To gain insight into the observed reactivity, we prepared the Cu(II) complex of the mixed thia/aza 14-N2S2 ligand. [Cu(II)(14-N2S2)(OTf)2] reacts reversibly with HNO at pH 7, although nonselectively over thiols and H2S. The recurrent sensing of HNO uncovered with the study of Cu(II) azamacrocyclic complexes is a remarkable feature that opens the door for the design of a new generation of metal-based probes.

Copper Chloride Catalysis: Do µ4-Oxido Copper Clusters Play a Significant Role?

Copper chloride catalysis is a well-established field in organic and inorganic chemistry. However, in most cases a detailed mechanistic understanding of the individual reaction steps and identification of reactive intermediates are still missing. The present study reports the results of spectroscopic and spectrometric measurements that support formation of copper agglomerates during catalytic processes. The composition of CuCl2·2H2O in several coordinating solvents and the influence of basic coreagents such as NaO(t)Bu and K2CO3 on the structure in the solid state as well as in solution were investigated. Several experiments involving crystal structure determination, IR spectroscopy, and ultra-high-resolution cryospray-ionization mass spectrometry were performed. The crystal structures of [CuCl2(H2O)]·0.5(CH3)2CO (1), [Cu2(CH3CN)2Cl4] (2), [Cu3(CH3CN)3Cl6] (3), [Cu3Cl6(THF)4] (4), [Cu(DMSO)2Cl2] (5), (H2N(CH3)2)2[CuCl3] (6), and [Cu4OCl6(THF)(urea)3]·3THF·urea (8) are reported herein. It can be clearly demonstrated that µ4-oxido copper clusters of the formula [Cu4OCl6(solvent)4] are the main product from the reactions of CuCl2·2H2O and basic coreagents. As a final result of these experiments, it can be stated that µ4-oxido copper clusters most likely play an important role in the mechanism of copper chloride-catalyzed reactions.

Aromaticity as stabilizing element in the bidentate activation for the catalytic reduction of carbon dioxide.

A new transition-metal-free mode for the catalytic reduction of carbon dioxide via bidentate interaction has been developed. In the presence of Li2[1,2-C6H4(BH3)2], CO2 can be selectively transformed to either methane or methanol, depending on the reducing agent. The bidentate nature of binding is supported by X-ray analysis of an intermediate analogue, which experiences special stabilization due to aromatic character in the bidentate interaction. Kinetic studies revealed a first-order reaction rate. The transformation can be conducted without any solvent.

Understanding Cooperativity in Homo- and Heterometallic Complexes: From Basic Concepts to Design.

Cooperative effects have attracted considerable attention in recent years. These effects are ubiquitous in chemistry and biology and can govern interactions of proteins with other biomolecules, mechanisms of supramolecular recognition and polymerization, catalysis, assembly of compounds on surfaces, and physical properties such as magnetic, electronic or optical properties, e. g. Consequently, the understanding of cooperative effects can lead to a structure-property relation that can pave the way to future applications in various research areas; however, with regard to cooperative effects in homo- and heterometallic complexes, we still are at the beginning of understanding. Nevertheless, concepts to describe cooperativity of metal centers as well as methodologies to investigate and model these effects have emerged over the last years. This concept article gives an overview of these existing concepts, approaches, and strategies to understand cooperative effects in homo- and heterometallic complexes. Special emphasis is put on concepts to define cooperative effects, their quantification, as well as methods to investigate cooperative effects.

Rifaximin Treatment of Collagenous Colitis: A Randomised, Double-Blind, Placebo-Controlled Trial.

Introduction: Collagenous colitis (CC) is a disabling disease primarily affecting elderly women. Sparse, well-documented treatment modalities exist, except for budesonide. Long-term and repetitive treatment with budesonide is often necessary. Rifaximin is a poorly absorbed antibiotic with a positive modulatory effect on gut microbiota. In this randomised, double-blind, placebo-controlled single-centre trial, we test the effect of adding rifaximin in continuation to budesonide on relapse rates in CC. Methods: Eligible patients with active, biopsy-verified CC received oral budesonide during a 6-week open-label induction phase. Patients in clinical remission after 4 weeks of treatment were randomised to receive either rifaximin or placebo for 4 weeks. Results: Fifteen patients were randomised to receive either rifaximin (n = 7) or placebo (n = 8). At 12-week follow-up, 2 patients in the rifaximin group were still in remission and none in the placebo group (p = 0.2). The median number of days in remission in the rifaximin group was 42 (interquartile range [IQR] 33-126) compared to 18.5 (IQR 10.5-51.5) in the placebo group (p = 0.189). At 12-week follow-up, the relapse rate per 100 person-days in the placebo group was higher (3.25 [1.40-6.41]) than in the rifaximin group (1.33 [0.43-3.10]). Conclusion: Although not statistically significant (p = 0.0996), the study suggests a potential improvement in relapse rates within the rifaximin group compared to the placebo group. A major limitation in the study is the small sample size.

Eating problems in young children -- a population-based study.

AIM: To analyse the prevalence of atypical eating problems and their associations with anxious or oppositional behaviours in young children. METHODS: One thousand and ninety children examined in the school enrolment test in a defined geographical region were included (544 boys). The parents completed a 25-item questionnaire regarding their child's eating behaviour and anxious or oppositional behaviours. RESULTS: Half of the parents reported that their child avoids certain foods (53%). Twenty-three percent showed selective eating, 26% showed an aversion against new foods. Children with underweight avoided more types of food and ate smaller amounts than children with normal or overweight. Three groups could be differentiated. Sixty-one percent of the children were 'normal eaters' with avoidance of certain foods, normal weight status and low anxious or oppositional behaviour. Thirty-four percent showed selective and/or restrictive eating, and 5% worried about their weight. Children with selective eating and with weight concerns were more often affected by anxious and oppositional behaviours. CONCLUSION: Atypical eating problems are common in young children. Without accompanying weight loss, behavioural or emotional problems, selective eating should be seen as a normal feature in young eating behaviour. Parents of young children with selective, restrictive eating or with weight worrying and psychological problems should be offered advice/treatment.

Synergistic anticancer activity of combined ATR and ribonucleotide reductase inhibition in Ewing's sarcoma cells.

PURPOSE: Ewing's sarcoma is a highly malignant childhood tumour whose outcome has hardly changed over the past two decades despite numerous attempts at chemotherapy intensification. It is therefore essential to identify new treatment options. The present study was conducted to explore the effectiveness of combined inhibition of two promising targets, ATR and ribonucleotide reductase (RNR), in Ewing's sarcoma cells. METHODS: Effects of the ATR inhibitor VE821 in combination with the RNR inhibitors triapine and didox were assessed in three Ewing's sarcoma cell lines with different TP53 status (WE-68, SK-ES-1, A673) by flow cytometric analysis of cell death, mitochondrial depolarisation and cell cycle distribution as well as by caspase 3/7 activity determination, by immunoblotting and by real-time RT-PCR. Interactions between inhibitors were evaluated by combination index analysis. RESULTS: Single ATR or RNR inhibitor treatment produced small to moderate effects, while their combined treatment produced strong synergistic ones. ATR and RNR inhibitors elicited synergistic cell death and cooperated in inducing mitochondrial depolarisation, caspase 3/7 activity and DNA fragmentation, evidencing an apoptotic form of cell death. All effects were independent of functional p53. In addition, VE821 in combination with triapine increased p53 level and induced p53 target gene expression (CDKN1A, BBC3) in p53 wild-type Ewing's sarcoma cells. CONCLUSION: Our study reveals that combined targeting of ATR and RNR was effective against Ewing's sarcoma in vitro and thus rationalises an in vivo exploration into the potential of combining ATR and RNR inhibitors as a new strategy for the treatment of this challenging disease.

The association between soluble CD163, disease severity, and ursodiol treatment in patients with primary biliary cholangitis.

INTRODUCTION: The macrophage activation marker soluble (s)CD163 is associated with disease severity and prognosis in patients with primary biliary cholangitis (PBC). Ursodeoxycholic acid (UDCA) treatment attenuates fibrosis progression in PBC patients, but its effect on macrophage activation is unclear. We examined the effect of UDCA on macrophage activation, as determined by sCD163 levels. METHODS: We included 2 cohorts of PBC patients; 1 cohort with prevalent PBC patients, and 1 cohort of incident PBC patients before start of UDCA treatment and with follow-up after 4 weeks and 6 months. We measured sCD163 and liver stiffness in both cohorts. Further, we measured sCD163 and TNF-α shedding in vitro in monocyte-derived macrophages after UDCA and lipopolysaccharide incubation. RESULTS: We included 100 patients with prevalent PBC [93% women, median age 63 y (interquartile range: 51-70)] and 47 patients with incident PBC [77% women, median age 60 y (49-67)]. Prevalent PBC patients had a lower median sCD163 of 3.54 mg/L (2.77-4.72) than incident PBC patients with a median sCD163 of 4.33 mg/L (2.83-5.99) at inclusion. Patients with an incomplete response to UDCA and patients with cirrhosis had higher sCD163 than responders to UDCA and noncirrhosis patients. After 4 weeks and 6 months of UDCA treatment median sCD163 decreased by 4.6% and 9.0%, respectively. In in vitro experiments, UDCA attenuated shedding of TNF-α, but not sCD163, from monocyte-derived macrophages. CONCLUSION: In PBC patients, sCD163 levels correlated with liver disease severity and treatment response to UDCA. Further, after 6 months of UDCA treatment, we observed a decrease in sCD163, which may be related to the treatment.

Closed-Loop Control of Arterial CO2 in Mechanical Ventilation of Neonates.

During mechanical ventilation of the neonate the main goal is to stabilize respiratory function of the often premature lungs. Ventilating the patient without inflicting harm is then the subordinated next goal. Ideally the arterial partial pressure of CO2 lays within a normocapnic range and fluctuations are kept minimal. By closely monitoring CO2 and controlling ventilation parameters accordingly, CO2 levels in the blood can be managed. We present an approach consisting of a cascaded controller for arterial CO2 by approximating arterial partial pressure PaCO2 from end-tidal PetCO2. As a proof of concept, feasibility of the controller was first evaluated on a mathematical patient model and subsequently in-vivo in lamb experiments. The controller is able to regulate CO2 into a normocapnic range in both setups with satisfactory stationarity within the target range. Estimation of the arterial partial pressure of CO2 remains a critical aspect that needs to be further investigated. Clinical relevance-Closed-loop control of CO2 in mechanical ventilation aims to avoid PaC O2 extremes and to reduce fluctuations. Both are a relevant risk factors especially for neurological complications among preterm newborns.