Publications by authors named "Philipp Brandt"

9 Publications

  • Page 1 of 1

Capture and Separation of SO Traces in Metal-Organic Frameworks via Pre-Synthetic Pore Environment Tailoring by Methyl Groups.

Angew Chem Int Ed Engl 2021 Jun 15. Epub 2021 Jun 15.

Hoffmann Institute of Advanced Materials, Shenzhen Polytechnic, 7098 Liuxian Blvd, Nanshan District, Shenzhen, 518055, China.

Herein, we report a pre-synthetic pore environment design strategy to achieve stable methyl-functionalized metal-organic frameworks (MOFs) for preferential SO binding and thus enhanced low (partial) pressure SO adsorption and SO /CO separation. The enhanced sorption performance is for the first time attributed to an optimal pore size by increasing methyl group densities at the benzenedicarboxylate linker in [Ni (BDC-X) DABCO] (BDC-X=mono-, di-, and tetramethyl-1,4-benzenedicarboxylate/terephthalate; DABCO=1,4-diazabicyclo[2,2,2]octane). Monte Carlo simulations and first-principles density functional theory (DFT) calculations demonstrate the key role of methyl groups within the pore surface on the preferential SO affinity over the parent MOF. The SO separation potential by methyl-functionalized MOFs has been validated by gas sorption isotherms, ideal adsorbed solution theory calculations, simulated and experimental breakthrough curves, and DFT calculations.
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http://dx.doi.org/10.1002/anie.202105229DOI Listing
June 2021

Zirconium and Aluminum MOFs for Low-Pressure SO Adsorption and Potential Separation: Elucidating the Effect of Small Pores and NH Groups.

ACS Appl Mater Interfaces 2021 Jun 11;13(24):29137-29149. Epub 2021 Jun 11.

Institut für Anorganische Chemie und Strukturchemie, Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf, Germany.

Finding new adsorbents for the desulfurization of flue gases is a challenging task but is of current interest, as even low SO emissions impair the environment and health. Four Zr- and eight Al-MOFs (Zr-Fum, DUT-67(Zr), NU-1000, MOF-808, Al-Fum, MIL-53(Al), NH-MIL-53(Al), MIL-53(tdc)(Al), CAU-10-H, MIL-96(Al), MIL-100(Al), NH-MIL-101(Al)) were examined toward their SO sorption capability. Pore sizes in the range of about 4-8 Å are optimal for SO uptake in the low-pressure range (up to 0.1 bar). Pore widths that are only slightly larger than the kinetic diameter of 4.1 Å of the SO molecules allow for multi-side-dispersive interactions, which translate into high affinity at low pressure. Frameworks NH-MIL-53(Al) and NH-MIL-101(Al) with an NH-group at the linker tend to show enhanced SO affinity. Moreover, from single-gas adsorption isotherms, ideal adsorbed solution theory (IAST) selectivities toward binary SO/CO gas mixtures were determined with selectivity values between 35 and 53 at a molar fraction of 0.01 SO (10.000 ppm) and 1 bar for the frameworks Zr-Fum, MOF-808, NH-MIL-53(Al), and Al-Fum. Stability tests with exposure to dry SO during ≤10 h and humid SO during 5 h showed full retention of crystallinity and porosity for Zr-Fum and DUT-67(Zr). However, NU-1000, MOF-808, Al-Fum, MIL-53(tdc), CAU-10-H, and MIL-100(Al) exhibited ≥50-90% retained Brunauer-Emmett-Teller (BET)-surface area and pore volume; while NH-MIL-100(Al) and MIL-96(Al) demonstrated a major loss of porosity under dry SO and MIL-53(Al) and NH-MIL-53(Al) under humid SO. SO binding sites were revealed by density functional theory (DFT) simulation calculations with adsorption energies of -40 to -50 kJ·mol for Zr-Fum and Al-Fum and even above -50 kJ·mol for NH-MIL-53(Al), in agreement with the isosteric heat of adsorption near zero coverage (Δ). The predominant, highest binding energy noncovalent binding modes in both Zr-Fum and Al-Fum feature μ-OH···OSO hydrogen bonding interactions. The small pores of Al-Fum allow the interaction of two μ-OH bridges from opposite pore walls with the same SO molecule via OH···OSO···HO hydrogen bonds. For NH-MIL-53(Al), the DFT high-energy binding sites involve NH···OS together with the also present Al-μ-OH···OS hydrogen bonding interactions and C-π···SO, N···SO interactions.
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http://dx.doi.org/10.1021/acsami.1c06003DOI Listing
June 2021

Metabolic modeling predicts specific gut bacteria as key determinants for Candida albicans colonization levels.

ISME J 2021 05 15;15(5):1257-1270. Epub 2020 Dec 15.

Systems Biology & Bioinformatics Unit, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knöll Institute, 07745, Jena, Germany.

Candida albicans is a leading cause of life-threatening hospital-acquired infections and can lead to Candidemia with sepsis-like symptoms and high mortality rates. We reconstructed a genome-scale C. albicans metabolic model to investigate bacterial-fungal metabolic interactions in the gut as determinants of fungal abundance. We optimized the predictive capacity of our model using wild type and mutant C. albicans growth data and used it for in silico metabolic interaction predictions. Our analysis of more than 900 paired fungal-bacterial metabolic models predicted key gut bacterial species modulating C. albicans colonization levels. Among the studied microbes, Alistipes putredinis was predicted to negatively affect C. albicans levels. We confirmed these findings by metagenomic sequencing of stool samples from 24 human subjects and by fungal growth experiments in bacterial spent media. Furthermore, our pairwise simulations guided us to specific metabolites with promoting or inhibitory effect to the fungus when exposed in defined media under carbon and nitrogen limitation. Our study demonstrates that in silico metabolic prediction can lead to the identification of gut microbiome features that can significantly affect potentially harmful levels of C. albicans.
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http://dx.doi.org/10.1038/s41396-020-00848-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8115155PMC
May 2021

Catch the wave: Metabolomic analyses in human pathogenic fungi.

PLoS Pathog 2020 08 20;16(8):e1008757. Epub 2020 Aug 20.

Septomics Research Center, Friedrich Schiller University and Leibniz Institute for Natural Product Research and Infection Biology-Hans Knöll Institute, Jena, Germany.

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http://dx.doi.org/10.1371/journal.ppat.1008757DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7440615PMC
August 2020

Clinical Vaginal Isolates and a Laboratory Strain Show Divergent Behaviors during Macrophage Interactions.

mSphere 2020 08 19;5(4). Epub 2020 Aug 19.

Septomics Research Center, Friedrich Schiller University and Leibniz Institute for Natural Product Research and Infection Biology-Hans Knoell Institute, Jena, Germany

Typically, established lab strains are widely used to study host-pathogen interactions. However, to better reflect the infection process, the experimental use of clinical isolates has come more into focus. Here, we analyzed the interaction of multiple vaginal isolates of the opportunistic fungal pathogen , the most common cause of vulvovaginal candidiasis in women, with key players of the host immune system: macrophages. We tested several strains isolated from asymptomatic or symptomatic women with acute and recurrent infections. While all clinical strains showed a response similar to the commonly used lab strain SC5314 in various assays, they displayed remarkable differences during interaction with macrophages. This coincided with significantly reduced β-glucan exposure on the cell surface, which appeared to be a shared property among the tested vaginal strains for yeast extract/peptone/dextrose-grown cells, which is partly lost when the isolates faced vaginal niche-like nutrient conditions. However, macrophage damage, survival of phagocytosis, and filamentation capacities were highly strain-specific. These results highlight the high heterogeneity of strains in host-pathogen interactions, which have to be taken into account to bridge the gap between laboratory-gained data and disease-related outcomes in an actual patient. Vulvovaginal candidiasis is one of the most common fungal infections in humans with as the major causative agent. This study is the first to compare clinical vaginal isolates of defined patient groups in their interaction with macrophages, highlighting the vastly different outcomes in comparison to a laboratory strain using commonly applied virulence-determining assays.
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http://dx.doi.org/10.1128/mSphere.00393-20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7407065PMC
August 2020

The Transcription Factor Stp2 Is Important for Biofilm Establishment and Sustainability.

Front Microbiol 2020 30;11:794. Epub 2020 Apr 30.

Septomics Research Center, Friedrich Schiller University and Leibniz Institute for Natural Product Research and Infection Biology - Hans Knöll Institute, Jena, Germany.

The fungal pathogen forms polymorphic biofilms where hyphal morphogenesis and metabolic adaptation are tightly coordinated by a complex intertwined network of transcription factors. The sensing and metabolism of amino acids play important roles during various phases of biofilm development - from adhesion to maturation. Stp2 is a transcription factor that activates the expression of amino acid permease genes and is required for environmental alkalinization and hyphal growth and during macrophage phagocytosis. While it is well established that Stp2 is activated in response to external amino acids, its role in biofilm formation remains unknown. In addition to widely used techniques, we applied newly developed approaches for automated image analysis to quantify Stp2-regulated filamentation and biofilm growth. Our results show that in the Δ deletion mutant adherence to abiotic surfaces and initial germ tube formation were strongly impaired, but formed mature biofilms with cell density and morphological structures comparable to the control strains. Stp2-dependent nutrient adaptation appeared to play an important role in biofilm development: Δ biofilms formed under continuous nutrient flow displayed an overall reduction in biofilm formation, whereas under steady conditions the mutant strain formed biofilms with lower metabolic activity, resulting in increased cell survival and biofilm longevity. A deletion of led to increased rapamycin susceptibility and transcriptional activation of , the transcriptional regulator of the general amino acid control pathway, demonstrating a connection of Stp2 to other nutrient-responsive pathways. In summary, the transcription factor Stp2 is important for biofilm formation, where it contributes to adherence and induction of morphogenesis, and mediates nutrient adaption and cell longevity in mature biofilms.
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http://dx.doi.org/10.3389/fmicb.2020.00794DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7203782PMC
April 2020

Encapsulation of Phosphorescent Pt(II) Complexes in Zn-Based Metal-Organic Frameworks toward Oxygen-Sensing Porous Materials.

Inorg Chem 2020 May 7;59(10):7252-7264. Epub 2020 May 7.

CiMIC, SoN, Institut für Anorganische und Analytische Chemie, Westfälische Wilhelms-Universität Münster, Corrensstraße 28/30, 48149 Münster, Germany.

In this work, we synthesized two tailored phosphorescent Pt(II) complexes bearing a cyclometalating tridentate thiazole-based C^N*N pincer luminophore () and exchangeable chlorido () or cyanido () coligands. While both complexes showed photoluminescence from metal-perturbed ligand-centered triplet states (MP-LC), reached the highest phosphorescence quantum yields and displayed a significant sensitivity toward quenching by O. We encapsulated them into two Zn-based metal-organic frameworks, namely, and . The incorporation of the organometallic compounds in the resulting composites , , , and was verified by powder X-ray diffractometry, scanning electron microscopy, time-resolved photoluminescence spectroscopy and microscopy, as well as N- and Ar-gas sorption studies. The amount of encapsulated complex was determined by graphite furnace atomic absorption spectroscopy, showing a maximum loading of 3.7 wt %. If compared with their solid state forms, the solid-solution composites showed prolonged O-sensitive excited state lifetimes for the complexes at room temperature, reaching up to 18.4 μs under an Ar atmosphere, which is comparable with the behavior of the complex in liquid solutions or even frozen glassy matrices at 77 K.
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http://dx.doi.org/10.1021/acs.inorgchem.0c00678DOI Listing
May 2020

Metal-Organic Frameworks with Potential Application for SO Separation and Flue Gas Desulfurization.

ACS Appl Mater Interfaces 2019 May 2;11(19):17350-17358. Epub 2019 May 2.

Hoffmann Institute of Advanced Materials , Shenzhen Polytechnic , 7098 Liuxian Blvd. , Nanshan District, Shenzhen 518055 , China.

Sulfur dioxide (SO) is an acidic and toxic gas and its emission from utilizing energy from fossil fuels or in industrial processes harms human health and environment. Therefore, it is of great interest to find new materials for SO sorption to improve classic flue gas desulfurization. In this work, we present SO sorption studies for the three different metal-organic frameworks MOF-177, NH-MIL-125(Ti), and MIL-160. MOF-177 revealed a new record high SO uptake (25.7 mmol·g at 293 K and 1 bar). Both NH-MIL-125(Ti) and MIL-160 show particular high SO uptakes at low pressures ( p < 0.01 bar) and thus are interesting candidates for the removal of remaining SO traces below 500 ppm from flue gas mixtures. The aluminum furandicarboxylate MOF MIL-160 is the most promising material, especially under application-orientated conditions, and features excellent ideal adsorbed solution theory selectivities (124-128 at 293 K, 1 bar; 79-95 at 353 K, 1 bar) and breakthrough performance with high onset time, combined with high stability under both humid and dry SO exposure. The outstanding sorption capability of MIL-160 could be explained by DFT simulation calculations and matching heat of adsorption for the binding sites O···S and OH···O (both ∼40 kJ·mol) and O···S (∼55-60 kJ·mol).
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http://dx.doi.org/10.1021/acsami.9b00029DOI Listing
May 2019

Candida albicans responds to glycostructure damage by Ace2-mediated feedback regulation of Cek1 signaling.

Mol Microbiol 2016 12 7;102(5):827-849. Epub 2016 Oct 7.

Department Biologie, Molekulare Mykologie, Heinrich-Heine-Universität, 40225, Düsseldorf, Germany.

Candida albicans uses the Cek1 MAPK pathway to restore cells from damage of its cell wall glycostructures. Defective protein N- or O-glycosylation activates Cek1 and the transcription factor Ace2 as its downstream target, to upregulate genes encoding protein O-mannosyltransferases (Pmt proteins). In unstressed cells, Cek1-Ace2 activity blocks expression of PMT1, which is de-repressed by tunicamycin. Genomic binding targets of Ace2 included ZCF21, which was upregulated by Ace2 and found to repress PMT1 transcription in unstressed cells. Surprisingly, genes encoding components of the Cek1 pathway including MSB2, CST20, HST7, CEK1 and ACE2 were also identified as Ace2 targets indicating Ace2-mediated transcriptional amplification of pathway genes under N-glycosylation stress. In this condition, physical interaction of the Ace2 protein with the upstream MAPKKK Cst20 was detected. Cst20-GFP showed stress-induced import from the cytoplasm into the nucleus and phosphorylation of Ace2. Interestingly, forced nuclear localization of Cst20 inhibited Cek1-Ace2 signaling, while forced cytoplasmic localization of Cst20 retained full signaling activity, suggesting that nuclear Cst20 downregulates the Cek1 pathway. Collectively, the results indicate that Ace2 is a versatile multifunctional transcriptional regulator, which activates glycostress responses of C. albicans by both positive forward and negative feedback regulation of Cek1 signaling.
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http://dx.doi.org/10.1111/mmi.13494DOI Listing
December 2016