Fast Gas-Adsorption Kinetics in Supraparticle-Based MOF Packings with Hierarchical Porosity.

Metal-organic frameworks (MOFs) are microporous adsorbents for high-throughput gas separation. Such materials exhibit distinct adsorption characteristics owing to the flexibility of the crystal framework in a nanoparticle, which can be different from its bulk crystal. However, for practical applications, such particles need to be compacted into macroscopic pellets, creating mass-transport limitations. In this work, this problem is addressed by forming materials with structural hierarchy, using a supraparticle-based approach. Spherical supraparticles composed of nanosized MOF particles are fabricated by emulsion templating and they are used as the structural component forming a macroscopic material. Zeolitic imidazolate framework-8 (ZIF-8) particles are used as a model system and the gas-adsorption kinetics of the hierarchical material are compared with conventional pellets without structural hierarchy. It is demonstrated that a pellet packed with supraparticles exhibits a 30 times faster adsorption rate compared to an unstructured ZIF-8 powder pellet. These results underline the importance of controlling structural hierarchy to maximize the performance of existing materials. In the hierarchical MOFs, large macropores between the supraparticles, smaller macropores between individual ZIF-8 primary particles, and micropores inherent to the ZIF-8 framework collude to combine large surface area, defined adsorption sites, and efficient mass transport to enhance performance.

Non-canonical Shedding of TNFα by SPPL2a Is Determined by the Conformational Flexibility of Its Transmembrane Helix.

Ectodomain (EC) shedding defines the proteolytic removal of a membrane protein EC and acts as an important molecular switch in signaling and other cellular processes. Using tumor necrosis factor (TNF)α as a model substrate, we identify a non-canonical shedding activity of SPPL2a, an intramembrane cleaving aspartyl protease of the GxGD type. Proline insertions in the TNFα transmembrane (TM) helix strongly increased SPPL2a non-canonical shedding, while leucine mutations decreased this cleavage. Using biophysical and structural analysis, as well as molecular dynamic simulations, we identified a flexible region in the center of the TNFα wildtype TM domain, which plays an important role in the processing of TNFα by SPPL2a. This study combines molecular biology, biochemistry, and biophysics to provide insights into the dynamic architecture of a substrate's TM helix and its impact on non-canonical shedding. Thus, these data will provide the basis to identify further physiological substrates of non-canonical shedding in the future.

Glycine Perturbs Local and Global Conformational Flexibility of a Transmembrane Helix.

Flexible transmembrane helices frequently support the conformational transitions between different functional states of membrane proteins. While proline is well known to distort and destabilize transmembrane helices, the role of glycine is still debated. Here, we systematically investigated the effect of glycine on transmembrane helix flexibility by placing it at different sites within the otherwise uniform leucine/valine repeat sequence of the LV16 model helix. We show that amide deuterium/hydrogen exchange kinetics are increased near glycine. Molecular dynamics simulations reproduce the measured exchange kinetics and reveal, at atomic resolution, a severe packing defect at glycine that enhances local hydration. Furthermore, glycine alters H-bond occupancies and triggers a redistribution of α-helical and 310-helical H-bonds. These effects facilitate local helix bending at the glycine site and change the collective dynamics of the helix.

CD14 is a key organizer of microglial responses to CNS infection and injury.

Microglia, innate immune cells of the CNS, sense infection and damage through overlapping receptor sets. Toll-like receptor (TLR) 4 recognizes bacterial lipopolysaccharide (LPS) and multiple injury-associated factors. We show that its co-receptor CD14 serves three non-redundant functions in microglia. First, it confers an up to 100-fold higher LPS sensitivity compared to peripheral macrophages to enable efficient proinflammatory cytokine induction. Second, CD14 prevents excessive responses to massive LPS challenges via an interferon ß-mediated feedback. Third, CD14 is mandatory for microglial reactions to tissue damage-associated signals. In mice, these functions are essential for balanced CNS responses to bacterial infection, traumatic and ischemic injuries, since CD14 deficiency causes either hypo- or hyperinflammation, insufficient or exaggerated immune cell recruitment or worsened stroke outcomes. While CD14 orchestrates functions of TLR4 and related immune receptors, it is itself regulated by TLR and non-TLR systems to thereby fine-tune microglial damage-sensing capacity upon infectious and non-infectious CNS challenges.

Influence of denaturation and aggregation of ß-lactoglobulin on its tryptic hydrolysis and the release of functional peptides.

Whereas previous studies showed that thermal pre-treatment of whey proteins promote their enzymatic hydrolysis, to date no correlation between the conformation of denatured protein and the release of individual peptides has been considered. Hence, in this study total denaturation of ß-lactoglobulin was performed at defined pH-values to enable the generation of different denatured particles. The denatured proteins were used as substrate for tryptic hydrolysis and the hydrolysis progress was characterised by the degree of hydrolysis (DH) and the release of functional peptides, detected using LC-ESI-TOF/MS. Denaturation and subsequent aggregation of ß-lactoglobulin, induced by thermal treatment at pH 5.1, altered the DH slightly, whereas the release of investigated peptides was significantly decreased. Contrary, denaturation at pH 6.8 and 8.0 led to formation of non-native monomers and reduced the DH to 75%, but showed promoting as well as reducing effects on the release of peptides, depending on their location within the protein.

Weight loss by telemonitoring of nutrition and physical activity in patients with metabolic syndrome for 1 year.

OBJECTIVE: Mobile technology can improve lifestyle programs, but the monitoring techniques and carer feedback need to be optimized. To this end, we investigated the efficacy of telemonitoring physical activity and nutrition over 12 months in patients with metabolic syndrome in a randomized, parallel-group, open trial. METHODS: Screening all over Germany yielded 184 patients with metabolic syndrome. All patients attended a single 2-hour instruction meeting in their region concerning a combination diet and the importance of physical activity. Thereafter they were randomized into a control group (controls, n = 62) or one of 2 different intervention groups. Both intervention groups were issued accelerometers, which measured physical activity, recorded daily weight and calorie intake, and transmitted these data to a central server for use by patient carers. In the Active Body Control Program of University of Magdeburg (ABC) intervention group (n = 60), information and motivation was ensured by weekly letters. In the 4sigma telephone coaching (4S) intervention group (n = 58), this was accomplished by monthly telephone calls from the carers. Clinical and biochemical data for all patients were collected at 0, 4, 8, and 12 months without any regular face-to-face meetings between patients and carers. The primary endpoint was weight loss and the secondary endpoint was the presence of metabolic syndrome. RESULTS: After 12 months the dropout rates in the control, 4S, and ABC groups were respectively 35%, 17%, and 18%. The adjusted relative weight losses after 12 months were respectively 3.7%, 8.6%, and 11.4% (all p < 0.000 versus baseline). ABC was more effective than 4S (p = 0.041); 43% of the patients completing the study in the ABC group lost more than 15% of their baseline weight. The diagnosis of metabolic syndrome was no longer applicable in 58% of the cases in the ABC group, in 41% of the 4S group, and in 33% of the controls. CONCLUSIONS: Telemonitoring of physical activity and nutrition markedly improves weight loss and markers of metabolic syndrome.

Vitamin d deficiency reduces the immune response, phagocytosis rate, and intracellular killing rate of microglial cells.

Meningitis and meningoencephalitis caused by Escherichia coli are associated with high rates of mortality and neurological sequelae. A high prevalence of neurological disorders has been observed in geriatric populations at risk of hypovitaminosis D. Vitamin D has potent effects on human immunity, including induction of antimicrobial peptides (AMPs) and suppression of T-cell proliferation, but its influence on microglial cells is unknown. The purpose of the present study was to determine the effects of vitamin D deficiency on the phagocytosis rate, intracellular killing, and immune response of murine microglial cultures after stimulation with the Toll-like receptor (TLR) agonists tripalmitoyl-S-glyceryl-cysteine (TLR1/2), poly(I·C) (TLR3), lipopolysaccharide (TLR4), and CpG oligodeoxynucleotide (TLR9). Upon stimulation with high concentrations of TLR agonists, the release of tumor necrosis factor alpha (TNF-α) and interleukin 6 (IL-6) was decreased in vitamin D-deficient compared to that in vitamin D-sufficient microglial cultures. Phagocytosis of E. coli K1 after stimulation of microglial cells with high concentrations of TLR3, -4, and -9 agonists and intracellular killing of E. coli K1 after stimulation with high concentrations of all TLR agonists were lower in vitamin D-deficient microglial cells than in the respective control cells. Our observations suggest that vitamin D deficiency may impair the resistance of the brain against bacterial infections.

Requirement of the RNA-editing enzyme ADAR2 for normal physiology in mice.

ADAR2, an RNA editing enzyme that converts specific adenosines to inosines in certain pre-mRNAs, often leading to amino acid substitutions in the encoded proteins, is mainly expressed in brain. Of all ADAR2-mediated edits, a single one in the pre-mRNA of the AMPA receptor subunit GluA2 is essential for survival. Hence, early postnatal death of mice lacking ADAR2 is averted when the critical edit is engineered into both GluA2 encoding Gria2 alleles. Adar2(-/-)/Gria2(R/R) mice display normal appearance and life span, but the general phenotypic effects of global lack of ADAR2 have remained unexplored. Here we have employed the Adar2(-/-)/Gria2(R/R) mouse line, and Gria2(R/R) mice as controls, to study the phenotypic consequences of loss of all ADAR2-mediated edits except the critical one in GluA2. Our extended phenotypic analysis covering ∼320 parameters identified significant changes related to absence of ADAR2 in behavior, hearing ability, allergy parameters and transcript profiles of brain.

The benzene metabolite para-benzoquinone is genotoxic in human, phorbol-12-acetate-13-myristate induced, peripheral blood mononuclear cells at low concentrations.

Benzene is one of the most prominent occupational and environmental pollutants. The substance is a proven human carcinogen that induces hematologic malignancies in humans, probably at even low doses. Yet knowledge of the mechanisms leading to benzene-induced carcinogenesis is still incomplete. Benzene itself is not genotoxic. The generation of carcinogenic metabolites involves the production of oxidized intermediates such as catechol, hydroquinone and para-benzoquinone (p-BQ) in the liver. Further activation to the ultimate carcinogenic intermediates is most probably catalyzed by myeloperoxidase (MPO). Yet the products of the MPO pathway have not been identified. If an oxidized benzene metabolite such as p-BQ was actually the precursor for the ultimate carcinogenic benzene metabolite and further activation proceeds via MPO mediated reactions, it should be possible to activate p-BQ to a genotoxic compound in vitro. We tested this hypothesis with phorbol-12-acetate-13-myristate (PMA) activated peripheral blood cells exposed to p-BQ, using the cytokinesis-block micronucleus test. Addition of 20-28 ng/ml PMA caused a significant increase of micronuclei at low and non-cytotoxic p-BQ concentrations between 0.04 and 0.2 microg/ml (0.37-1.85 microM). Thus with PMA or p-BQ alone no reproducible elevation of micronuclei was seen up to toxic concentrations. PMA and p-BQ induce micronuclei when administered jointly. Our results add further support to the hypothesis that MPO is a key enzyme in the activation of benzene.