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11. Silver and palladium nanoparticles produced using a plant extract as reducing agent, stabilized with an ionic liquid: sizing by X-ray powder diffraction and dynamic light scattering

Author

Eya’ane Meva, Francois, Ntoumba, Agnes Antoinette, Belle Ebanda Kedi, Philippe, Tchoumbi, Edmond, Schmitz, Alexa, Schmolke, Laura, Klopotowski, Maximilian, Moll, Bastian, Kökcam-Demir, Ülkü, Mpondo Mpondo, Emmanuel Albert, Lehman, Leopold Gustave, and Janiak, Christoph

Published
2019
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20. The Complexity of Comparative Adsorption of C 6 Hydrocarbons (Benzene, Cyclohexane, n -Hexane) at Metal–Organic Frameworks.

Author

Jansen, Christian, Assahub, Nabil, Spieß, Alex, Liang, Jun, Schmitz, Alexa, Xing, Shanghua, Gökpinar, Serkan, and Janiak, Christoph

Subjects
METAL-organic frameworks, CYCLOHEXANE, BENZENE, ADSORPTION (Chemistry), HYDROCARBONS
Abstract

The relatively stable MOFs Alfum, MIL-160, DUT-4, DUT-5, MIL-53-TDC, MIL-53, UiO-66, UiO-66-NH2, UiO-66(F)4, UiO-67, DUT-67, NH2-MIL-125, MIL-125, MIL-101(Cr), ZIF-8, ZIF-11 and ZIF-7 were studied for their C6 sorption properties. An understanding of the uptake of the larger C6 molecules cannot simply be achieved with surface area and pore volume (from N2 sorption) but involves the complex micropore structure of the MOF. The maximum adsorption capacity at p p0−1 = 0.9 was shown by DUT-4 for benzene, MIL-101(Cr) for cyclohexane and DUT-5 for n-hexane. In the low-pressure range from p p0−1 = 0.1 down to 0.05 the highest benzene uptake is given by DUT-5, DUT-67/UiO-67 and MIL-101(Cr), for cyclohexane and n-hexane by DUT-5, UiO-67 and MIL-101(Cr). The highest uptake capacity at p p0−1 = 0.02 was seen with MIL-53 for benzene, MIL-125 for cyclohexane and DUT-5 for n-hexane. DUT-5 and MIL-101(Cr) are the MOFs with the widest pore window openings/cross sections but the low-pressure uptake seems to be controlled by a complex combination of ligand and pore-size effect. IAST selectivities between the three binary mixtures show a finely tuned and difficult to predict interplay of pore window size with (critical) adsorptive size and possibly a role of electrostatics through functional groups such as NH2. [ABSTRACT FROM AUTHOR]

Published
2022
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21. 1H NMR spectra, structure, and conformational exchange of S-n-alkyl-tetrahydrothiophenium cations of some ionic liquids.

Author

Hägele, Gerhard, Nazarski, Ryszard B., Schmitz, Alexa, Xing, Shanghua, and Janiak, Christoph

Abstract

S-n-alkyl-tetrahydrothiophenium cations [R-THT]+ in some iodide or tetraphenylborate ion-pairs [R-THT][X] (R = methyl to n-decyl, X−= I−, [BPh4]−, [NTf2]−) are characterized in the solid state by puckered THT rings in twist forms. In contrast, solution 1H NMR spectra of compounds [R-THT][X] indicate a rapid conformational exchange leading to dynamic [ABCD]2 spin systems due to eight protons of the THT ring. These strongly coupled spectra obtained at high magnetic fields were analyzed by iterative methods and simulated successfully. In addition, molecular modeling and gauge-including atomic orbitals (GIAOs) based calculations of proton NMR chemical shifts for two such ion-pair compounds in solution were performed at the density functional theory (DFT) level. As a result, conformational equilibrium between two different pairs of isoenergetic twist forms of the THT ring in [Me-THT][I] (global and local energy minima) was found to exist. These theoretical results are discussed in view of experimental 1H NMR spectral data. [ABSTRACT FROM AUTHOR]

Published
2022
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25. Odd–even effect for efficient bioreactions of chiral alcohols and boosted stability of the enzyme

Author

Bülow, Mark, Schmitz, Alexa, Mahmoudi, Termeh, Schmidt, Dana, Junglas, Fabian, Janiak, Christoph, and Held, Christoph

Abstract

We describe a holistic approach for achieving a nearly quantitative conversion for an enzymatic reaction while simultaneously increasing the long-term stability of the enzyme. The approach provided chemical control of bioreactions by utilizing newly synthesized tetrahydrothiophene-based ionic liquids (THT ILs). We showcased its power by using THT-ILs as additives at a low concentration (only 10 mmol L−1) in the alcohol dehydrogenase (ADH)-catalyzed synthesis of methylated 1-phenylethanol (Me-PE). We discovered an “odd–even” effect of the IL-cation chain length: Me-PE displayed beneficial interactions with THT ILs having odd-numbered chain lengths and deleterious interactions with those having even-numbered chain lengths. An intermolecular thermodynamic simulation of the bulk phase and critical micelle concentration investigations of the local surroundings of the THT-ILs proved the occurrence of these interactions, and these two methods confirmed the odd–even effect from different perspectives. Additionally, storing the ADH enzyme in pure THT IL at room temperature allowed for a boosted long-term stability of the enzyme (500 times greater than that in aqueous buffer) without the need for freezing., RSC Advances;10(47)

Published
2020
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30. Synthesis of plasmonic Fe/Al nanoparticles in ionic liquids

Author

Schmitz, Alexa, primary, Meyer, Hajo, additional, Meischein, Michael, additional, Garzón Manjón, Alba, additional, Schmolke, Laura, additional, Giesen, Beatriz, additional, Schlüsener, Carsten, additional, Simon, Paul, additional, Grin, Yuri, additional, Fischer, Roland A., additional, Scheu, Christina, additional, Ludwig, Alfred, additional, and Janiak, Christoph, additional

Published
2020
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35. Solid-Solution Mixed-Linker Synthesis of Isoreticular Al-Based MOFs for an Easy Hydrophilicity Tuning in Water-Sorption Heat Transformations

Author

Schlüsener, Carsten, Xhinovci, Mergime, Ernst, Sebastian-Johannes, Schmitz, Alexa, Tannert, Niels, Janiak, Christoph, and Publica

Subjects
Lüftungs- und Klimatechnik, Energieeffiziente Gebäude
Abstract

The solid-solution mixed-linker approach, where a linker is partially replaced by a similar one under retention of the isoreticular metal-organic framework (MOF) structure, offers an easy and inexpensive way to fine-tune MOF properties to design tailored compounds. A total of 10 aluminum mixed-linker MOFs, [Al(OH)(X)a(Y)1-a] (X = IPA, isophthalate; Y = FDC, 2,5-furandicarboxylate) spanning between the isostructural MOFs CAU-10-H (a = 1) and MIL-160 (a = 0), were synthesized by employing different ratios of the aforementioned linkers. CAU-10-H and MIL-160 have been reported as highly promising materials for cycling water sorption for heat transformation applications. A detailed characterization with a focus on the changes in the sorption properties for water vapor showed that the hydrophilicity is readily and easily tuned through the mixed-linker approach between the limits of MIL-160 and CAU-10-H. An increasing fraction of IPA shifts the steep increase in the S-shaped water adsorption isotherm in small steps from p/p0 = ∼0.05 for MIL-160 to p/p0 = ∼0.18 for CAU-10-H. Higher coefficient of performance (COPH) values for the mixed-linker materials over MIL-160 illustrate the well-balanced hydrophobicity/hydrophilicity of the former under the exemplary calculation conditions.

Published
2019

36. Air-Con Metal–Organic Frameworks in Binder Composites for Water Adsorption Heat Transformation Systems

Author

Gökpinar, Serkan, primary, Ernst, Sebastian-Johannes, additional, Hastürk, Emrah, additional, Möllers, Marc, additional, El Aita, Ilias, additional, Wiedey, Raphael, additional, Tannert, Niels, additional, Nießing, Sandra, additional, Abdpour, Soheil, additional, Schmitz, Alexa, additional, Quodbach, Julian, additional, Füldner, Gerrit, additional, Henninger, Stefan K., additional, and Janiak, Christoph, additional

Published
2019
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42. Tetrahydrothiophene‐Based Ionic Liquids: Synthesis and Thermodynamic Characterizations.

Author

Schmitz, Alexa, Bülow, Mark, Schmidt, Dana, Zaitsau, Dzmitry H., Junglas, Fabian, Knedel, Tim‐Oliver, Verevkin, Sergey P., Held, Christoph, and Janiak, Christoph

Subjects
*IONIC liquids, *VAPOR pressure, *ION exchange chromatography, *THERMOGRAVIMETRY, *MAGNETIC resonance
Abstract

S‐alkyltetrahydrothiophenium, [CnTHT]+ bis(trifluorosulfonyl)imide, [NTf2]− room temperature ionic liquids (ILs) and tetraphenylborate, [BPh4]− salts with alkyl chain lengths from C4 to C10 have been prepared. The ILs and salts were characterized and their purity verified by 1H‐ and 13C‐nuclear magnetic resonance, elemental analysis, ion chromatography, Karl‐Fischer titration, single crystal X‐ray diffraction as well as thermogravimetric analysis. The experimentally determined density and viscosity decrease with increasing temperature. The experimental solubility of the [CnTHT][NTf2]‐ILs in water (75 to 2.2 mg/L for C4 to C10) was modelled with very good agreement by Perturbed Chain Statistical Associating Fluid Theory (PC‐SAFT), based on the extremely low vapor pressures for the [CnTHT][NTf2]‐ILs measured in this work (4.15 to 0.037 ⋅ 10−7×psat for C4 to C10). PC‐SAFT is able to predict and correlate different thermodynamic properties by estimating the Helmholtz residual energy. [ABSTRACT FROM AUTHOR]

Published
2021
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45. Student Voice Report 2014

Author

Bello, Patrick Di, Kraus, Christine, Serson, William, Fu-Chyun Chu, Cody, Will, Iaffaldano, Brian, Bolormaa Jamiyansuren, Kilian, Ben, Minkenberg, Bastian, Read, Andrew, Schmitz, Alexa, Singha, Poonam, Squires, Caleb, Tayengwa, Reuben, Tian, Li, Turner, Sarah, Tyler, Marshall, and Upadhyaya, Indu

Published
2014
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50. A New Means To Identify Type 3 Secreted Effectors: Functionally Interchangeable Class IB Chaperones Recognize a Conserved Sequence

Author

Schmitz, Alexa M., Jahufar, Fathima F., Boyd, Justin D., Cho, Min Y., Costa, Sonia, Glicksman, Marcie Ann, and Lesser, Cammie

Abstract

Many Gram-negative bacteria utilize specialized secretion systems to inject proteins (effectors) directly into host cells. Little is known regarding how bacteria ensure that only small subsets of the thousands of proteins they encode are recognized as substrates of the secretion systems, limiting their identification through bioinformatic analyses. Many of these proteins require chaperones to direct their secretion. Here, using the newly described protein interaction platform assay, we demonstrate that type 3 secretion system class IB chaperones from one bacterium directly bind their own effectors as well as those from other species. In addition, we observe that expression of class IB homologs from seven species, including pathogens and endosymbionts, mediate the translocation of effectors from Shigella directly into host cells, demonstrating that class IB chaperones are often functionally interchangeable. Notably, class IB chaperones bind numerous effectors. However, as previously proposed, they are not promiscuous; rather they recognize a defined sequence that we designate the conserved chaperone-binding domain (CCBD) sequence [(LMIF)\(_{1}\)XXX(IV)\(_{5}\)XX(IV)\(_{8}\)X(N)\(_{10}\)]. This sequence is the first defined amino acid sequence to be identified for any interspecies bacterial secretion system, i.e., a system that delivers proteins directly into eukaryotic cells. This sequence provides a new means to identify substrates of type III secretion systems. Indeed, using a pattern search algorithm for the CCBD sequence, we have identified the first two probable effectors from an endosymbiont, Sodalis glossinidius.

Published
2012
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