Synthesis of a miniaturized [FeFe] hydrogenase model system

The reaction occurring during artificial maturation of [FeFe] hydrogenase has been recreated using molecular systems. The formation of a miniaturized [FeFe] hydrogenase model system, generated through the combination of a [4Fe4S] cluster binding oligopeptide and an organometallic Fe complex, has been monitored by a range of spectroscopic techniques. A structure of the final assembly is suggested based on EPR and FTIR spectroscopy in combination with DFT calculations. The capacity of this novel H-cluster model to catalyze H2 production in aqueous media at mild potentials is verified in chemical assays.

Association between prophylactic low-molecular-weight heparin use in pregnancy and macrosomia: analysis of the Ottawa and Kingston birth cohort

Essentials Low-molecular-weight heparin (LMWH) is used to prevent venous thromboembolism (VTE) in pregnancy. We evaluated the association between LMWH and large for gestational age (LGA) infants. We found no significant associations between LMWH use and LGA. LMWH does not appear to increase the risk for the delivery of an LGA infant. SUMMARY: Background Low-molecular-weight heparin (LMWH), an anticoagulant, is the recommended drug for thromboprophylaxis and treatment of venous thromboembolism (VTE) in pregnancy. During pregnancy, LMWH is routinely prescribed to mothers with an increased risk of VTE or with a history of thrombosis. Although clinical reports of larger offspring born to women administered LMWH have been noted, no studies to date have evaluated or associated the use of LMWH and large for gestational age (LGA) infants. Objectives To determine whether there is an association between LMWH usage in mothers and the prevalence of LGA. Patients/Methods We performed an analysis of the Ottawa and Kingston (OaK) Birth Cohort and report characteristics of LMWH and association LGA (> 10%ile). We used coarsened exact matching (CEM) methods to account for bias and confounding. Results A total of 7519 women from the OaK Birth Cohort were included; 59 were administered LMWH during pregnancy (0.78%). Mothers prescribed LMWH had significantly greater BMI (P = 0.0001), age (P = 0.0001) and parity (P = 0.02). Gestational length was shorter among women administered LMWH compared to those without treatment (37.7 ± 2.0 vs. 39.2 ± 2.0, P < 0.0001), an iatrogenic finding. The odds ratio of an LGA delivery among women administered LMWH was 1.02 (95% confidence interval [CI], 0.48-2.16; P = 0.96) in unadjusted analyses and was 1.15 (95% CI, 0.49-2.71) in the matched sample adjusted for maternal age, BMI and gestational age. Conclusions These results, although exploratory, provide indirect evidence of no increased risk of LGA infants among women prescribed LMWH.

Probing the oxidation state of transition metal complexes: a case study on how charge and spin densities determine Mn L-edge X-ray absorption energies

Transition metals in inorganic systems and metalloproteins can occur in different oxidation states, which makes them ideal redox-active catalysts. To gain a mechanistic understanding of the catalytic reactions, knowledge of the oxidation state of the active metals, ideally in operando, is therefore critical. L-edge X-ray absorption spectroscopy (XAS) is a powerful technique that is frequently used to infer the oxidation state via a distinct blue shift of L-edge absorption energies with increasing oxidation state. A unified description accounting for quantum-chemical notions whereupon oxidation does not occur locally on the metal but on the whole molecule and the basic understanding that L-edge XAS probes the electronic structure locally at the metal has been missing to date. Here we quantify how charge and spin densities change at the metal and throughout the molecule for both redox and core-excitation processes. We explain the origin of the L-edge XAS shift between the high-spin complexes MnII(acac)2 and MnIII(acac)3 as representative model systems and use ab initio theory to uncouple effects of oxidation-state changes from geometric effects. The shift reflects an increased electron affinity of MnIII in the core-excited states compared to the ground state due to a contraction of the Mn 3d shell upon core-excitation with accompanied changes in the classical Coulomb interactions. This new picture quantifies how the metal-centered core hole probes changes in formal oxidation state and encloses and substantiates earlier explanations. The approach is broadly applicable to mechanistic studies of redox-catalytic reactions in molecular systems where charge and spin localization/delocalization determine reaction pathways.

Detection and analysis of fine particulate matter and microbial aerosol in chicken houses in Shandong Province, China

Bacteria and fungi are primary constituents of airborne microbes in fine particulate matter and harmful to health. To evaluate the environmental quality of different poultry houses in Shandong Province, China, the airborne aerobic bacteria, airborne fungi, and airborne Escherichia coli were collected by the Andersen-6 air microorganism sampler. The fine particulate matter was collected by a ZR-3920 ambient air particulate matter sampler, and bacterial and fungal diversities and relative abundances analyzed using high-throughput sequencing. Results showed that the concentrations of airborne aerobic bacteria, airborne fungi, and airborne Escherichia coli in poultry houses were 0.167 to 4.484 × 104 CFU/m3, 0.236 to 4.735 × 103 CFU/m3, and 0 to 33.0 CFU/m3, respectively. 11.4 to 34.3% of aerobic bacteria and 16.8 to 37.5% of fungi were distributed at levels 5 and 6 (0.6 to 2.1 μm, the particle sizes similar to fine particulate matter) in the Andersen sampler. The concentration of fine particulate matter in the poultry houses was 114 to 230 μg/m3, which was higher than the safety value 10 specified by WHO. In fine particulate matter, the main bacteria at phylum level were Firmicutes, Bacteroidetes, and Proteobacteria, whereas the dominant phylum of fungus was Ascomycota and Basidiomycota. Importantly, the relative abundances of Escherichia and Corynebacterium in the broiler houses were greater than those in layer houses. However, the percentages of Aspergillus and Penicillium were 13.5 and 0.56%, with a relatively high level in the layer houses. Altogether, results revealed that the ambient air quality in the poultry houses sampled had a relatively high abundance of conditional pathogenic bacteria and concentration of fine particulate matter, which could threaten the health of animals and workers in those environments.

Cr L-Edge X-ray Absorption Spectroscopy of CrIII(acac)3 in Solution with Measured and Calculated Absolute Absorption Cross Sections

X-ray absorption spectroscopy at the L-edge of 3d transition metals is widely used for probing the valence electronic structure at the metal site via 2p-3d transitions. Assessing the information contained in L-edge absorption spectra requires systematic comparison of experiment and theory. We here investigate the Cr L-edge absorption spectrum of high-spin chromium acetylacetonate Cr^III(acac)₃ in solution. Using a transmission flatjet enables determining absolute absorption cross sections and spectra free from X-ray-induced sample damage. We address the challenges of measuring Cr L absorption edges spectrally close to the O K absorption edge of the solvent. We critically assess how experimental absorption cross sections can be used to extract information on the electronic structure of the studied system by comparing our results of this Cr^III (3d³) complex to our previous work on L-edge absorption cross sections of Mn^III(acac)₃ (3d⁴) and Mn^II(acac)₂ (3d⁵). Considering our experimental uncertainties, the most insightful experimental observable for this d³(Cr^III)-d⁴(Mn^III)-d⁵(Mn^II) series is the L-edge branching ratio, and we discuss it in comparison to semiempirical multiplet theory and ab initio restricted active space calculations. We further discuss and analyze trends in integrated absorption cross sections and correlate the spectral shapes with the local electronic structure at the metal sites.

X-ray-induced sample damage at the Mn L-edge: a case study for soft X-ray spectroscopy of transition metal complexes in solution

X-ray induced sample damage can impede electronic and structural investigations of radiation-sensitive samples studied with X-rays. Here we quantify dose-dependent sample damage to the prototypical MnIII(acac)3 complex in solution and at room temperature for the soft X-ray range, using X-ray absorption spectroscopy at the Mn L-edge. We observe the appearance of a reduced MnII species as the X-ray dose is increased. We find a half-damage dose of 1.6 MGy and quantify a spectroscopically tolerable dose on the order of 0.3 MGy (1 Gy = 1 J kg-1), where 90% of MnIII(acac)3 are intact. Our dose-limit is around one order of magnitude lower than the Henderson limit (half-damage dose of 20 MGy) which is commonly employed for protein crystallography with hard X-rays. It is comparable, however, to the dose-limits obtained for collecting un-damaged Mn K-edge spectra of the photosystem II protein, using hard X-rays. The dose-dependent reduction of MnIII observed here for solution samples occurs at a dose limit that is two to four orders of magnitude smaller than the dose limits previously reported for soft X-ray spectroscopy of iron samples in the solid phase. We compare our measured to calculated spectra from ab initio restricted active space (RAS) theory and discuss possible mechanisms for the observed dose-dependent damage of MnIII(acac)3 in solution. On the basis of our results, we assess the influence of sample damage in other experimental studies with soft X-rays from storage-ring synchrotron radiation sources and X-ray free-electron lasers.

[The impact of male circumcision on the natural history of genital HPV infection: a prospective cohort study]

Objective: To analyze the correlation between circumcision and incidence and clearance of male genital HPV infection. Methods: From May to July 2014, 18-55 year old men who had sexual behavior history were recruited from the general population in Liuzhou, Guangxi to set up a cohort. Totally, 113 circumcised and 560 uncircumcised men were enrolled and interviewed using a questionnaire (including information on demographic characteristics and sexual behaviors), then they were followed-up with 6-month interval for 2 times. On each visit, specimens of male external genitalia were collected and genotyped for HPV DNA. The differences of incidence and clearance of genital HPV infections between circumcised and uncircumcised men were analyzed by Log-rank test. Cox regression was used to analyze the relationship between circumcision and incidence and clearance of HPV infection. Results: The median age (P(25), P(75)) of circumcised and uncircumcised men were 28 (24, 35) and 32 (24, 31), respectively. The incidences of any HPV infections were 9.1 (95%CI: 2.4-15.7) and 8.4 (95% CI: 5.6-11.2) per 1 000 person-months (χ(2)=0.10, P=0.758), respectively. The clearance of circumcised men [136.3 (95%CI: 70.0-202.7) per 1 000 person-months] was higher than that in uncircumcised men [89.6 (95%CI: 65.9-113.3) per 1 000 person-months] (χ(2)=8.19, P=0.004). In multivariate COX regression analysis, compared with uncircumcised men, circumcised men had higher possibility to clear any HPV infections (HR: 2.41, 95%CI: 1.30-4.46). Compared with men having one sexual partner, people having more than 4 sexual partners had lower possibility to clear any HPV infections (HR: 0.49, 95%CI: 0.25-0.96). Compared with 18-25 years old men, men aged 26-35 years old had higher possibility to clear high-risk HPV infections (HR: 2.14, 95%CI: 1.08-4.23). Conclusion: Circumcised and uncircumcised men had similar incidence of genital HPV infection, whereas, men conducted circumcision and having fewer sexual partners could increase the clearance of genital HPV infections.

Direct Determination of Absolute Absorption Cross Sections at the L-Edge of Dilute Mn Complexes in Solution Using a Transmission Flatjet

The 3d transition metals play a pivotal role in many charge transfer processes in catalysis and biology. X-ray absorption spectroscopy at the L-edge of metal sites probes metal 2p-3d excitations, providing key access to their valence electronic structure, which is crucial for understanding these processes. We report L-edge absorption spectra of MnII(acac)2 and MnIII(acac)3 complexes in solution, utilizing a liquid flatjet for X-ray absorption spectroscopy in transmission mode. With this, we derive absolute absorption cross-sections for the L-edge transitions with peak magnitudes as large as 12 and 9 Mb for MnII(acac)2 and MnIII(acac)3, respectively. We provide insight into the electronic structure with ab initio restricted active space calculations of these L-edge transitions, reproducing the experimental spectra with excellent agreement in terms of shapes, relative energies, and relative intensities for the two complexes. Crystal field multiplet theory is used to assign spectral features in terms of the electronic structure. Comparison to charge transfer multiplet calculations reveals the importance of charge transfer in the core-excited final states. On the basis of our experimental observations, we extrapolate the feasibility of 3d transition metal L-edge absorption spectroscopy using the liquid flatjet approach in probing highly dilute biological solution samples and possible extensions to table-top soft X-ray sources.

Pure red cell aplasia with t-cell large granular lymphocytic leukemia

Pure red cell aplasia (PRCA) develops as a result of erythroid precursors failing to reach maturity in the bone marrow, which eventually leads to anemia. Here we present a case of a 64-year-old Asian male with a medical history of colorectal adenocarcinoma who had been treated with 6 cycles of oxaliplatin and capecitabine four years ago. The patient was diagnosed with PRCA and T-cell large granular lymphocyte leukemia.

[Relationship between overnight urinary sodium to potassium ratio and the risk of cardiovascular disease]

Objective: To explore the relationship between overnight urinary sodium to potassium ratio and the risk of cardiovascular disease (CVD). Methods: A subsample of 10 percent of the participants (35-59 years old) from the People's Republic of China-United States Collaborative Study of Cardiovascular and Cardiopulmonary Epidemiology (prospective survey) were used. Three consecutive overnight urine samples were collected in the autumn of 1983-1984 and the spring in 1985-1986, respectively. Urinary sodium and potassium were detected and calculated for 8 hours excretion. The occurrences of cardiovascular events were recorded in 2 years interval from 1987-1988 until December 31, 2005. Participants were divided into first ratio group, second ratio group, and third ratio group based on the tertiles of sodium to potassium ratio. Cox proportional hazard regression model was used to determine the relationship between sodium to potassium ratio and risk of CVD. In addition, participants were divided into 2 subgroups by the median of overnight urinary sodium and potassium, and then combined each other for 4 subgroups including low sodium-low potassium group, low sodium-high potassium group, high sodium-low potassium group, and high sodium-high potassium group, to explore the relationship between different sodium-potassium combinations and the risk of CVD. Results: A total of 954 participants were included in the final analysis, of whom 459 (48.1%) were males. There were 318 cases in the first, second and third ratio group, respectively. There were 347 cases in low sodium-low potassium group and high sodium-high potassium group, and 130 cases in low sodium-high potassium group and high sodium-low potassium group. After a median follow-up of 18.6 (18.3, 19.3) years, cardiovascular events occurred in 81 participants, including 64 stroke and 20 coronary heart disease events. Multivariate analysis showed that comparing with the first ratio group, the hazard ratios (HR) in the second and the third ratio groups were 2.04 (95%CI 1.06-3.95, P=0.034) and 2.07 (95%CI 1.07-4.03, P=0.032), respectively. The CVD risk in low sodium-low potassium group was 24% higher than the low sodium-high potassium group (reference), but this result did not reach statistical significant level (P=0.685). The risks in high sodium-high potassium group (HR=3.32, 95%CI 1.26-8.76,P=0.015) and high sodium-low potassium (HR=3.04, 95%CI 1.05-8.83, P=0.041) group were both significantly increased. Conclusions: Overnight urinary sodium to potassium ratio is positively correlated with the risk of cardiovascular events. High urinary sodium plays a more important role for the increased risk of cardiovascular events than low potassium.

Fingerprints of electronic, spin and structural dynamics from resonant inelastic soft X-ray scattering in transient photo-chemical species

We describe how inversion symmetry separation of electronic state manifolds in resonant inelastic soft X-ray scattering (RIXS) can be applied to probe excited-state dynamics with compelling selectivity. In a case study of Fe L3-edge RIXS in the ferricyanide complex Fe(CN)63-, we demonstrate with multi-configurational restricted active space spectrum simulations how the information content of RIXS spectral fingerprints can be used to unambiguously separate species of different electronic configurations, spin multiplicities, and structures, with possible involvement in the decay dynamics of photo-excited ligand-to-metal charge-transfer. Specifically, we propose that this could be applied to confirm or reject the presence of a hitherto elusive transient Quartet species. Thus, RIXS offers a particular possibility to settle a recent controversy regarding the decay pathway, and we expect the technique to be similarly applicable in other model systems of photo-induced dynamics.

MicroRNA-126 deficiency enhanced the activation and function of CD4+ T cells by elevating IRS-1 pathway

Recent evidence has shown that microRNA-126 (miR-126) has been involved in the development and function of immune cells, which contributed to the pathogenesis of related clinical diseases. However, the potential role of miR-126 in the development and function of CD4+ T cells remains largely unknown. Here we first found that the activation and proliferation, as well as the expression of interferon (IFN)-γ, of CD4+ T cells from miR-126 knock-down (KD) mice using the miRNA-sponge technique were enhanced significantly in vitro, compared with those in CD4+ T cells from wild-type (WT) mice. To monitor further the possible effect of miR-126 deficiency on the function of CD4+ T cells in vivo, we used dextran sulphate sodium (DSS)-induced murine model of acute autoimmune colitis and found that miR-126 deficiency could elevate the pathology of colitis. Importantly, the proportion of CD4+ T cells in splenocytes increased significantly in miR-126KD mice. Moreover, the expression levels of CD69 and CD44 on CD4+ T cells increased significantly and the expression level of CD62L decreased significantly. Of note, adoptive cell transfer assay showed that the pathology of colitis was more serious in carboxyfluorescein succinimidyl ester (CFSE)-labelled miR-126KD CD4+ T cell-transferred group, compared with that in the CFSE-labelled WT CD4+ T cells transferred group. Consistently, the expression levels of CD69 and CD44 on CFSE+ cells increased significantly. Furthermore, both the proliferation and IFN-γ secretion of CFSE+ cells also increased significantly in the CFSE-labelled miR-126KD CD4+ T cell-transferred group. Mechanistic evidence showed that the expression of insulin receptor substrate 1 (IRS-1), as a functional target of miR-126, was elevated in CD4+ T cells from miR-126KD mice, accompanied by altered transduction of the extracellular regulated kinase, protein B (AKT) and nuclear factor kappa B (NF-κB) pathway. Our data revealed a novel role in which miR-126 was an intrinsic regulator in the function of CD4+ T cells, which provided preliminary basis for exploring further the role of miR-126 in the development, function of CD4+ T cells and related clinical diseases.