| 1. |
- Carraro, F., et al.
(författare)
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Phase dependent encapsulation and release profile of ZIF-based biocomposites
- 2020
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Ingår i: Chemical Science. - : Royal Society of Chemistry (RSC). - 2041-6520 .- 2041-6539. ; 11:13, s. 3397-3404
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Tidskriftsartikel (refereegranskat)abstract
- Biocomposites composed of Zeolitic Imidazolate Frameworks (ZIFs) are generating significant interest due to their facile synthesis, and capacity to protect proteins from harsh environments. Here we systematically varied the composition (i.e. relative amounts of ligand (2-methylimidazole), metal precursor (Zn(OAc)(2)center dot 2H(2)O), and protein) and post synthetic treatments (i.e. washes with water or water/ethanol) to prepare a series of protein@ZIF biocomposites. These data were used to construct two ternary phase diagrams that showed the synthesis conditions employed gave rise to five different phases including, for the first time, biocomposites based on ZIF-CO3-1. We examined the influence of the different phases on two properties relevant to drug delivery applications: encapsulation efficiency and release profile. The encapsulation efficiencies of bovine serum albumin and insulin were phase dependent and ranged from 75% to 100%. In addition, release profiles showed that 100% protein release varied between 40 and 300 minutes depending on the phase. This study provides a detailed compositional map for the targeted preparation of ZIF-based biocomposites of specific phases and a tool for the straightforward analysis of the crystalline phases of ZIF based materials (web application named ZIF phase analysis). These data will facilitate the progress of ZIF bio-composites in the fields of biomedicine and biotechnology.
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| 2. |
- Ge, Meng, 1993-, et al.
(författare)
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Direct Location of Organic Molecules in Framework Materials by Three-Dimensional Electron Diffraction
- 2022
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 144:33, s. 15165-15174
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Tidskriftsartikel (refereegranskat)abstract
- In the study of framework materials, probing interactions between frameworks and organic molecules is one of the most important tasks, which offers us a fundamental understanding of host–guest interactions in gas sorption, separation, catalysis, and framework structure formation. Single-crystal X-ray diffraction (SCXRD) is a conventional method to locate organic species and study such interactions. However, SCXRD demands large crystals whose quality is often vulnerable to, e.g., cracking on the crystals by introducing organic molecules, and this is a major challenge to use SCXRD for structural analysis. With the development of three-dimensional electron diffraction (3D ED), single-crystal structural analysis can be performed on very tiny crystals with sizes on the nanometer scale. Here, we analyze two framework materials, SU-8 and SU-68, with organic molecules inside their inorganic crystal structures. By applying 3D ED, with fast data collection and an ultralow electron dose (0.8–2.6 e– Å–2), we demonstrate for the first time that each nonhydrogen atom from the organic molecules can be ab initio located from structure solution, and they are shown as distinct and well-separated peaks in the difference electrostatic potential maps showing high accuracy and reliability. As a result, two different spatial configurations are identified for the same guest molecule in SU-8. We find that the organic molecules interact with the framework through strong hydrogen bonding, which is the key to immobilizing them at well-defined positions. In addition, we demonstrate that host–guest systems can be studied at room temperature. Providing high accuracy and reliability, we believe that 3D ED can be used as a powerful tool to study host–guest interactions, especially for nanocrystals.
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| 3. |
- Ge, Meng, et al.
(författare)
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High-Throughput Electron Diffraction Reveals a Hidden Novel Metal-Organic Framework for Electrocatalysis
- 2021
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 60:20, s. 11391-11397
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Tidskriftsartikel (refereegranskat)abstract
- Metal-organic frameworks (MOFs) are known for their versatile combination of inorganic building units and organic linkers, which offers immense opportunities in a wide range of applications. However, many MOFs are typically synthesized as multiphasic polycrystalline powders, which are challenging for studies by X-ray diffraction. Therefore, developing new structural characterization techniques is highly desired in order to accelerate discoveries of new materials. Here, we report a high-throughput approach for structural analysis of MOF nano- and sub-microcrystals by three-dimensional electron diffraction (3DED). A new zeolitic-imidazolate framework (ZIF), denoted ZIF-EC1, was first discovered in a trace amount during the study of a known ZIF-CO3-1 material by 3DED. The structures of both ZIFs were solved and refined using 3DED data. ZIF-EC1 has a dense 3D framework structure, which is built by linking mono- and bi-nuclear Zn clusters and 2-methylimidazolates (mIm(-)). With a composition of Zn-3(mIm)(5)(OH), ZIF-EC1 exhibits high N and Zn densities. We show that the N-doped carbon material derived from ZIF-EC1 is a promising electrocatalyst for oxygen reduction reaction (ORR). The discovery of this new MOF and its conversion to an efficient electrocatalyst highlights the power of 3DED in developing new materials and their applications.
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| 4. |
- Ge, Meng, 1993-
(författare)
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On the accuracy of crystal structural analysis and the potential of unraveling structural details by 3D electron diffraction
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Knowing the atomic crystal structures of ordered porous solids is essential in understanding their behaviors and properties, developing new applications, and designing new porous materials. Electrons have a much shorter wavelength and much stronger interaction with atoms in a crystal compared with X-ray. Therefore, electron crystallography can effectively determine the structures of nano- and micro-sized crystals. Three-dimensional electron diffraction (3D ED) methods have been developed for the structure determination of various types of complex crystal structures. Continuous rotation electron diffraction (cRED) has unique aspects in both fast data collection and accurate structure determination. This thesis focused on the accuracy of crystal structure analysis and the potential of unraveling structural details by cRED. The cRED method was first applied for the ab initio structure determination of a beam-sensitive biocomposite metal-organic framework (MOF), BSA@ZIF-CO3-1. The atomic structure of BSA@ZIF-CO3-1 obtained by cRED was the same compared to that obtained by single crystal X-ray diffraction (SCXRD). Accurate atomic structures could be obtained by cRED. The sample of BSA@ZIF-CO3-1 was initially regarded as a pure new phase, however, during the cRED data collection and processing procedure, two distinct crystal systems and unit cells were revealed. BSA@ZIF-CO3-1 was identified as the major phase in the sample, and a new MOF, denoted ZIF-EC1, as the minor phase. ZIF-EC1 has a dense 3D framework with high N and Zn densities, which is a promising candidate for electrocatalysis. The discovery of ZIF-EC1 was followed by investigating the effects of improving 3D ED data completeness on the structural analysis. I successfully solved the structures of ZIF-EC1 from each individual dataset with the lowest completeness of 44.5% and refined to a high precession (better than 0.04 Å). Then I merged ten datasets to obtain a high data completeness, the structural model is improved, peaks appear more spherical in the electrostatic potential maps. The next part of this thesis was focused on unraveling structural details. By applying cRED, each non-Hydrogen atom from guest molecules can be separately localized from the difference Fourier map for two open framework germanates, SU-8 and SU-68. The atomic structure of both the framework and the guest molecules obtained by cRED is as reliable and accurate as that obtained by SCXRD. In the last part, the application of cRED into determining structures for new materials are highlighted. The structure of two new MOFs, Cd-MOF and Pb-MOF are successfully determined by cRED.
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| 5. |
- Ge, Meng, et al.
(författare)
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On the completeness of three-dimensional electron diffraction data for structural analysis of metal-organic frameworks
- 2021
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Ingår i: Faraday discussions. - 1359-6640 .- 1364-5498. ; 231
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Tidskriftsartikel (refereegranskat)abstract
- Three-dimensional electron diffraction (3DED) has been proven as an effective and accurate method for structure determination of nano-sized crystals. In the past decade, the crystal structures of various new complex metal-organic frameworks (MOFs) have been revealed by 3DED, which has been the key to understand their properties. However, due to the design of transmission electron microscopes (TEMs), one drawback of 3DED experiments is the limited tilt range of goniometers, which often leads to incomplete 3DED data, particularly when the crystal symmetry is low. This drawback can be overcome by high throughput data collection using continuous rotation electron diffraction (cRED), where data from a large number of crystals can be collected and merged. Here, we investigate the effects of improving completeness on structural analysis of MOFs. We use ZIF-EC1, a zeolitic imidazolate framework (ZIF), as an example. ZIF-EC1 crystallizes in a monoclinic system with a plate-like morphology. cRED data of ZIF-EC1 with different completeness and resolution were analyzed. The data completeness increased to 92.0% by merging ten datasets. Although the structures could be solved from individual datasets with a completeness as low as 44.5% and refined to a high precision (better than 0.04 angstrom), we demonstrate that a high data completeness could improve the structural model, especially on the electrostatic potential map. We further discuss the strategy adopted during data merging. We also show that ZIF-EC1 doped with cobalt can act as an efficient electrocatalyst for oxygen reduction reactions.
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| 6. |
- Ge, Meng, et al.
(författare)
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Three-Dimensional Electron Diffraction for Structural Analysis of Beam-Sensitive Metal-Organic Frameworks
- 2021
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Ingår i: Crystals. - : MDPI AG. - 2073-4352. ; 11:3
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Forskningsöversikt (refereegranskat)abstract
- Electrons interact strongly with matter, which makes it possible to obtain high-resolution electron diffraction data from nano- and submicron-sized crystals. Using electron beam as a radiation source in a transmission electron microscope (TEM), ab initio structure determination can be conducted from crystals that are 6-7 orders of magnitude smaller than using X-rays. The rapid development of three-dimensional electron diffraction (3DED) techniques has attracted increasing interests in the field of metal-organic frameworks (MOFs), where it is often difficult to obtain large and high-quality crystals for single-crystal X-ray diffraction. Nowadays, a 3DED dataset can be acquired in 15-250 s by applying continuous crystal rotation, and the required electron dose rate can be very low (<0.1 e s(-1) angstrom(-2)). In this review, we describe the evolution of 3DED data collection techniques and how the recent development of continuous rotation electron diffraction techniques improves data quality. We further describe the structure elucidation of MOFs using 3DED techniques, showing examples of using both low- and high-resolution 3DED data. With an improved data quality, 3DED can achieve a high accuracy, and reveal more structural details of MOFs. Because the physical and chemical properties of MOFs are closely associated with their crystal structures, we believe 3DED will only increase its importance in developing MOF materials.
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| 7. |
- Ge, Xiaodong, et al.
(författare)
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Amelioration of type 2 diabetes by the novel 6, 8-guanidyl luteolin quinone-chromium coordination via biochemical mechanisms and gut microbiota interaction
- 2023
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Ingår i: JOURNAL OF ADVANCED RESEARCH. - : Elsevier. - 2090-1232 .- 2090-1224. ; 46, s. 173-188
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Luteolin is a plant-derived flavonoid that exhibits a broad range of pharmacological activ-ities. Studies on luteolin have mainly focused on its use for hyperlipidaemia prevention, whereas the capacity of the flavonoid to hinder hyperglycaemia development remains underexplored.Objectives: To probe the anti-hyperglycemic mechanism of 6,8-guanidyl luteolin quinone-chromium coordination (GLQ.Cr), and to assess its regulatory effect on intestinal microbiota in type 2 diabetes mel-litus (T2DM) mice.Methods: High-sucrose/high-fat diet-induced and intraperitoneal injection of streptozotocin was used to develop a T2DM model. Glycometabolism related indicators, histopathology, and gut microbiota compo-sition in caecum samples were evaluated, and RNA sequencing (RNA-seq) of liver samples was con-ducted. Faecal microbiota transplantation (FMT) was further used to verify the anti-hyperglycemic activity of intestinal microbiota.Results: The administration of GLQ.Cr alleviated hyperglycaemia symptoms by improving liver and pan-creatic functions and modulating gut microbe communities (Lactobacillus, Alistipes, Parabacteroides, Lachnoclostridium, and Desulfovibrio). RNA-seq analysis showed that GLQ.Cr mainly affected the peroxi-some proliferative activated receptor (PPAR) signalling pathway in order to regulate abnormal glucose metabolism. FMT significantly modulated the abundance of Lactobacillus, Alloprevotella, Alistipes, Bacteroides, Ruminiclostridium, Brevundimonas and Pseudomonas in the caecum to balance blood glucose levels and counteract T2DM mice inflammation.Conclusion: GLQ.Cr improved the abnormal glucose metabolism in T2DM mice by regulating the PPAR signalling pathway and modulating intestinal microbial composition. FMT can improve the intestinal microecology of the recipient and in turn ameliorate the symptoms of T2DM-induced hyperglycaemia.
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| 8. |
- Huang, Zhehao, et al.
(författare)
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Can 3D electron diffraction provide accurate atomic structures of metal-organic frameworks?
- 2021
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Ingår i: Faraday discussions. - : Royal Society of Chemistry (RSC). - 1359-6640 .- 1364-5498. ; 225:0, s. 118-132
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Tidskriftsartikel (refereegranskat)abstract
- Many framework materials such as metal–organic frameworks (MOFs) or porous coordination polymers (PCPs) are synthesized as polycrystalline powders, which are too small for structure determination by single crystal X-ray diffraction (SCXRD). Here, we show that a three-dimensional (3D) electron diffraction method, namely continuous rotation electron diffraction (cRED), can be used for ab initio structure determination of such materials. As an example, we present the complete structural analysis of a biocomposite, denoted BSA@ZIF-CO3-1, in which Bovine Serum Albumin (BSA) was encapsulated in a zeolitic imidazolate framework (ZIF). Low electron dose was combined with ultrafast cRED data collection to minimize electron beam damage to the sample. We demonstrate that the atomic structure obtained by cRED is as reliable and accurate as that obtained by single crystal X-ray diffraction. The high accuracy and fast data collection open new opportunities for investigation of cooperative phenomena in framework structures at the atomic level.
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