| 1. |
- Bassani, Carlos L., et al.
(författare)
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Nanocrystal Assemblies : Current Advances and Open Problems
- 2024
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Ingår i: ACS Nano. - 1936-0851. ; 18:23, s. 14791-14840
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Forskningsöversikt (refereegranskat)abstract
- We explore the potential of nanocrystals (a term used equivalently to nanoparticles) as building blocks for nanomaterials, and the current advances and open challenges for fundamental science developments and applications. Nanocrystal assemblies are inherently multiscale, and the generation of revolutionary material properties requires a precise understanding of the relationship between structure and function, the former being determined by classical effects and the latter often by quantum effects. With an emphasis on theory and computation, we discuss challenges that hamper current assembly strategies and to what extent nanocrystal assemblies represent thermodynamic equilibrium or kinetically trapped metastable states. We also examine dynamic effects and optimization of assembly protocols. Finally, we discuss promising material functions and examples of their realization with nanocrystal assemblies.
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| 2. |
- Chen, Xingchen, et al.
(författare)
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A Versatile and Robust Serine Protease Inhibitor Scaffold from Actinia tenebrosa
- 2019
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Ingår i: Marine Drugs. - : MDPI. - 1660-3397. ; 17:12
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Tidskriftsartikel (refereegranskat)abstract
- Serine proteases play pivotal roles in normal physiology and a spectrum of patho-physiological processes. Accordingly, there is considerable interest in the discovery and design of potent serine protease inhibitors for therapeutic applications. This led to concerted efforts to discover versatile and robust molecular scaffolds for inhibitor design. This investigation is a bioprospecting study that aims to isolate and identify protease inhibitors from the cnidarian Actinia tenebrosa. The study isolated two Kunitz-type protease inhibitors with very similar sequences but quite divergent inhibitory potencies when assayed against bovine trypsin, chymostrypsin, and a selection of human sequence-related peptidases. Homology modeling and molecular dynamics simulations of these inhibitors in complex with their targets were carried out and, collectively, these methodologies enabled the definition of a versatile scaffold for inhibitor design. Thermal denaturation studies showed that the inhibitors were remarkably robust. To gain a fine-grained map of the residues responsible for this stability, we conducted in silico alanine scanning and quantified individual residue contributions to the inhibitor’s stability. Sequences of these inhibitors were then used to search for Kunitz homologs in an A. tenebrosa transcriptome library, resulting in the discovery of a further 14 related sequences. Consensus analysis of these variants identified a rich molecular diversity of Kunitz domains and expanded the palette of potential residue substitutions for rational inhibitor design using this domain.
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| 3. |
- Chen, Xingchen, et al.
(författare)
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Potent, multi-target serine protease inhibition achieved by a simplified beta-sheet motif
- 2019
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Ingår i: PLOS ONE. - : Public Library Science. - 1932-6203. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Engagement of an extended beta-sheet is a common substrate/inhibitor interaction at the active site of serine proteases and is an important feature of Laskowski mechanism inhibitors that present a substrate-like loop to a target protease. This loop is cleaved but subsequently relegated forming a stable inhibitor/protease complex. Laskowski inhibitors are ubiquitous in nature and are used extensively in serine protease inhibitor design. However, most studies concentrate on introducing new sidechain interactions rather than the direct contributions of the substrate-like beta-sheet to enzyme inhibition. Here we report the crystal structure of an simplified beta-sheet inhibitory motif within the Sunflower Trypsin Inhibitor (SFTI) in complex with trypsin. We show that the intramolecular hydrogen bond network of this SFTI variant (SFTI-TCTR) engages the inhibitor sidechains that would normally interact with a target protease, giving mainchain interactions a more prominent role in complex formation. Despite having reduced sidechain interactions, this SFTI variant is remarkably potent and inhibits a diverse range of serine proteases. Crystal structural analysis and molecular modelling of SFTI-TCTR complexes again indicates an interface dominated by beta-sheet interactions, highlighting the importance of this motif and the adaptability of SFTI as a scaffold for inhibitor design.
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| 4. |
- Li, Xingchen, et al.
(författare)
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Analysis on breakup dynamics of hydrogen taylor bubble formation in a cross-junction microchannel
- 2021
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Ingår i: International Journal of Hydrogen Energy. - : Elsevier BV. - 0360-3199. ; 46:67, s. 33438-33452
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Tidskriftsartikel (refereegranskat)abstract
- The pinch-off dynamics during hydrogen bubble formation was experimentally investigated in a cross-junction microchannel. A binarization interface recognizing and key frame tracking method was established. By analyzing the breakup dynamics through spatial and time domains, the effects of interfacial tension and viscosity on hydrogen bubble pinch-off were revealed. A transitional stage between a liquid squeezing stage and a free pinch-off stage was newly observed and the transitional stage was named as the wave model stage because of the long-wave approximation of the interface at this stage. The time criteria between the three stages are proved to be around 1/10 of tcap (capillary time) and around tcap to the pinch-off moment, respectively. However, the power law exponents of the minimum radial radius R0 for hydrogen - liquid flow, larger than those for nitrogen - liquid flow, are consistent with literature works in terms of both range and tendency.
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| 5. |
- Li, Xingchen, et al.
(författare)
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Breakup dynamics of gas-liquid interface during Taylor bubble formation in a microchannel flow-focusing device
- 2020
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Ingår i: Experimental Thermal and Fluid Science. - : Elsevier BV. - 0894-1777. ; 113
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Tidskriftsartikel (refereegranskat)abstract
- This work aims to investigate the breakup dynamics of the gas-liquid interface during bubble formation in a microchannel flow-focusing device. An interface tracking method is developed to capture the profiles of the gaseous thread evolution. The results show that the pinch-off period can be further divided into a liquid squeezing stage and a free pinch-off stage in both the radial and axial directions. The time domain criterion between these two stages in a low viscous liquid, with Ohnesorge numbers Oh≪1, is proved to be shorter than the capillary time. The effects of surface tension, viscosity and gas inertial force exerting on the interface during the free pinch-off stage are proved similar to those in a quiescent liquid pool. The power law of the minimum diameter at the gaseous thread to the pinch-off remaining time in the present experiments agrees with previous studies in both ranges (1/3 to 1/2) and tendency.
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| 6. |
- Li, Xingchen, et al.
(författare)
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Breakup dynamics of low-density gas and liquid interface during Taylor bubble formation in a microchannel flow-focusing device
- 2020
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Ingår i: Chemical Engineering Science. - : Elsevier BV. - 0009-2509. ; 215
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Tidskriftsartikel (refereegranskat)abstract
- This work aims to investigate the breakup dynamics of the low-density gas and liquid interface during bubble formation in a microchannel flow-focusing device. A high-contrast interface tracking method is developed. After the neck motion analysis in radial and axial directions, the time domain criterion between the liquid squeezing stage and the free pinch-off stage is proved to be two orders of magnitude less than the capillary time and is close to the viscous time of the liquid. Comparing to Nitrogen bubbles, the pinch-off point of Helium bubbles deflects downstream in viscous liquids and upstream in low surface tension liquids. Helium bubbles generate faster in viscous liquids and slower in low surface tension liquids. The power law exponents of thread diameter to the pinch-off remaining time in Helium experiments, which are larger than those in Nitrogen experiments, agree with previous studies in both ranges (1/3–1/2) and tendency.
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| 7. |
- Li, Xingchen, et al.
(författare)
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High conversion hydrogen peroxide microchannel reactors : Design and two-phase flow instability investigation
- 2021
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Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947. ; 422
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Tidskriftsartikel (refereegranskat)abstract
- Novel micro-scale reaction devices are progressing in various applications. Whereas, specialized gas-producing reactors of high conversion at micro/mini scale remain challenging and are rarely explored, but are needed urgently in new generation vehicles and aerospace applications. In this work, two kinds of high-aspect-ratio flat channel (200 μm depth, 5.0 mm width, and 40.0 mm length) microreactors with platinum foil catalyst, named as inlet reactors and outlet reactors, are designed and tested for H2O2 decomposition. The wavelet transform method is applied to analyze the effects of reactant flow rate and pin–fin configuration on flow instability in both the time domain and the frequency domain. The inlet reactors utilize periodic flow pattern transitions to achieve an independence of conversion on reactant flow rate. For outlet reactors, the upstream compressible slug volume and the backflow are restricted by the pin–fin array, and thus the H2O2 decomposition reaches a conversion of 59.0% at 5 ml/h reactant flow rate. This conversion is 300% higher than those of H2O2 decomposition in microchannel reactors ever reported in the literature. The results from this work can be used for the design and manufacturing of micro-scale reactors for gas involved applications.
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