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Local Electronic Structure of Molecular Heterojunctions in a Single-Layer 2D Covalent Organic Framework
摘要： The synthesis of a single-layer covalent organic framework (COF) with spatially modulated internal potentials provides new opportunities for manipulating the electronic structure of molecularly defined materials. Here, the fabrication and electronic characterization of COF-420: a single-layer porphyrin-based square-lattice COF containing a periodic array of oriented, type II electronic heterojunctions is reported. In contrast to previous donor–acceptor COFs, COF-420 is constructed from building blocks that yield identical cores upon reticulation, but that are bridged by electrically asymmetric linkers supporting oriented electronic dipoles. Scanning tunneling spectroscopy reveals staggered gap (type II) band alignment between adjacent molecular cores in COF-420, in agreement with first-principles calculations. Hirshfeld charge analysis indicates that dipole fields from oriented imine linkages within COF-420 are the main cause of the staggered electronic structure in this square grid of atomically–precise heterojunctions.
关键词： type II heterojunctions,covalent organic frameworks,density functional theory,scanning tunneling microscopy and spectroscopy,electronic structure
更新于2025-09-09 09:28:46
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A blue fluorescent labeling technique utilizing micro- and nanoparticles for tracking in LIVE/DEAD® stained pathogenic biofilms of Staphylococcus aureus and Burkholderia cepacia
摘要： Strategies that target and treat biofilms are widely applied to bacterial cultures using popular live/dead staining techniques with mostly red or green fluorescent markers (eg, with SYTO? 9, propidium iodide, fluorescein). Therefore, visualizing drugs or micro- and nanoparticulate delivery systems to analyze their distribution and effects in biofilms requires a third fluorescent dye that does not interfere with the properties of the live/dead markers. The present study establishes and evaluates a model for tracking polymeric particles in fluorescently stained biological material. To this end, poly(d,l-lactide-co-glycolide) (PLGA)-based micro- and nanoparticles were used as well-established model systems, which, because of their favorable safety profiles, are expected to play important future roles with regard to drug delivery via inhalation. PLGA was covalently and stably labeled with 7-amino-4-methyl-3-coumarinylacetic acid (AMCA), after which blue fluorescent poly(ethylene glycol)-block-PLGA (PEG-PLGA) particles were prepared using a mixture of fluorescent AMCA-PLGA and PEG-PLGA. Because chitosan is known to reduce negative surface charge, blue fluorescent PEG-PLGA-particles with chitosan were also prepared. These micro- and nanoparticles were physicochemically characterized and could be clearly distinguished from live/dead stained bacteria in biofilms using confocal laser scanning microscopy.
关键词： 7-amino-4-methyl-3-coumarinylacetic acid,cystic fibrosis,PEG,PLGA,chitosan,hydrodynamic diameter,confocal laser scanning microscopy
更新于2025-09-09 09:28:46
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BCAbox Algorithm Expands Capabilities of Raman Microscope for Single Organelles Assessment
摘要： Raman microspectroscopy is a rapidly developing technique, which has an unparalleled potential for in situ proteomics, lipidomics, and metabolomics, due to its remarkable capability to analyze the molecular composition of live cells and single cellular organelles. However, the scope of Raman spectroscopy for bio-applications is limited by a lack of software tools for express-analysis of biomolecular composition based on Raman spectra. In this study, we have developed the first software toolbox for immediate analysis of intracellular Raman spectra using a powerful biomolecular component analysis (BCA) algorithm. Our software could be easily integrated with commercial Raman spectroscopy instrumentation, and serve for precise analysis of molecular content in major cellular organelles, including nucleoli, endoplasmic reticulum, Golgi apparatus, and mitochondria of either live or fixed cells. The proposed software may be applied in broad directions of cell science, and serve for further advancement and standardization of Raman spectroscopy.
关键词： single cell assay,biomolecular analysis,Raman spectrometry,microscopy
更新于2025-09-09 09:28:46
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Collection, pre-processing and on-the-fly analysis of data for high-resolution, single-particle cryo-electron microscopy
摘要： The dramatic growth in the use of cryo-electron microscopy (cryo-EM) to generate high-resolution structures of macromolecular complexes has changed the landscape of structural biology. The majority of structures deposited in the Electron Microscopy Data Bank (EMDB) at higher than 4-? resolution were collected on Titan Krios microscopes. Although the pipeline for single-particle data collection is becoming routine, there is much variation in how sessions are set up. Furthermore, when collection is under way, there are a range of approaches for efficiently moving and pre-processing these data. Here, we present a standard operating procedure for single-particle data collection with Thermo Fisher Scientific EPU software, using the two most common direct electron detectors (the Thermo Fisher Scientific Falcon 3 (F3EC) and the Gatan K2), as well as a strategy for structuring these data to enable efficient pre-processing and on-the-fly monitoring of data collection. This protocol takes 3–6 h to set up a typical automated data collection session.
关键词： cryo-electron microscopy,single-particle analysis,Gatan K2,Falcon 3,macromolecular complexes,Titan Krios,data pre-processing,EPU software,direct electron detectors,high-resolution structures
更新于2025-09-09 09:28:46
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Nucleation of diindenoperylene and pentacene at thermal and hyperthermal incident kinetic energies
摘要： The authors have examined the nucleation of diindenoperylene (DIP) on SiO2 employing primarily atomic force microscopy and focusing on the effect of incident kinetic energy employing both thermal and supersonic sources. For all incident kinetic energies examined (Ei ? 0.09–11.3 eV), the nucleation of DIP is homogeneous and the dependence of the maximum island density on the growth rate is described by a power law. A critical nucleus of approximately two molecules is implicated by our data. A re-examination of the nucleation of pentacene on SiO2 gives the same major result that the maximum island density is determined by the growth rate, and it is independent of the incident kinetic energy. These observations are readily understood by factoring in the size of the critical nucleus in each case, and the island density, which indicates that diffusive transport of molecules to the growing islands dominate the dynamics of growth in the submonolayer regime.
关键词： thermal,SiO2,supersonic sources,diindenoperylene,hyperthermal,kinetic energies,nucleation,atomic force microscopy,pentacene
更新于2025-09-09 09:28:46
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Photocatalytic Degradation of Gentian Violet with Li Doped Bismuth Oxide Nanorods
摘要： Li doped bismuth oxide nanorods have been synthesized via the hydrothermal route. The obtained nanorods possess semi-circular tips, the length and diameter are 1–5 μm and 50–350 nm, respectively. The photocatalytic activity of the Li doped bismuth oxide nanorods has been analyzed by the photocatalytic degradation of gentian violet (GV). GV with the concentration of 10 mg · mL?1 can be photodegraded totally in the presence of 10 mg Li doped bismuth oxide nanorods under UV light irradiation for 60 min. The photodegradation ratio of the Li doped bismuth oxide nanorods is closely relative to the content of the nanorods and initial GV concentration. The photodegradation ratio decreases obviously with the decrease of the content of the nanorods and increase of initial GV concentration.
关键词： Photocatalysis,Li Doped Bismuth Oxide Nanorods,Gentian Violet,Scanning Electron Microscopy
更新于2025-09-09 09:28:46
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[IEEE 2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) - Honolulu, HI, USA (2018.7.18-2018.7.21)] 2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) - Tracking Gene Expression via Light Sheet Microscopy and Computer Vision in Living Organisms
摘要： Automated tracking of spatiotemporal gene expression using in vivo microscopy images have given great insight into understanding developmental processes in multicellular organisms. Many existing analysis tools rely on the fluorescent tagging of cell wall or cell nuclei localized proteins to assess position, orientation, and overall shape of an organism; information necessary for determining locations of gene expression activity. Particularly in plants, organism lines that have fluorescent tags can take months to develop, which can be time consuming and costly. We propose an automated solution for analyzing spatial characteristics of gene expression without the necessity of fluorescent tagged cell walls or cell nuclei. Our solution indicates, segments, and tracks gene expression using a fluorescent imaging channel of a light sheet microscope while determining gene expression location within an organism from a Brightfield (non-fluorescent) imaging channel. We use the images obtained from the Arabidopsis thaliana root as a proof of concept for our solution by studying the effects of heat shock stress on CYCLIN B1 protein production.
关键词： computer vision,CYCLIN B1,light sheet microscopy,gene expression,Arabidopsis thaliana
更新于2025-09-09 09:28:46
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Latent tracks in bulk yttrium-iron garnet crystals irradiated with low and high velocity krypton and xenon ions
摘要： Bulk yttrium-iron garnet (YIG) single crystals have been irradiated with swift Kr and Xe ions having energies from 0.4 to 22.8 MeV/u and electronic stopping powers from 8.9 to 28.9 keV/nm near the irradiated surface. Transmission electron microscopy (TEM) has been used for direct observation of non-overlapping amorphous latent tracks in the near surface region of the irradiated bulk YIG crystals. The amorphous track radii observed in this work have been compared with previously reported data from direct and indirect measurements. It was found that the thickness of the sample subjected to swift heavy ion irradiation does not significantly affect the resulting amorphous track size observed by TEM in YIG. The results also support previously observed consistency between direct TEM and indirect Rutherford backscattering in channelling mode (RBS/C) and Mossbauer spectroscopy (MS) methods for amorphous track evaluation in YIG when electronic stopping power is greater than ～13 keV/nm, which is sufficient to create cylindrical amorphous tracks by high velocity ions (E > 10 MeV/u). Indirect methods provide underestimated values compared to TEM when the electronic stopping power is below ～13 keV/nm, for which discrete amorphous tracks are supposed to be formed by high velocity ions.
关键词： Transmission electron microscopy,Latent tracks,Radiation damage,Yttrium-iron garnet,Swift heavy ions
更新于2025-09-09 09:28:46
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Study on the Application of Electric Field to Giant Vesicles Comprised of 1,2-Dilauroyl-Sn-Glycero-3-Phosphatidylcholine Using Optical Fluorescence Microscopy
摘要： The influence of alternating electric field (AC) in the structure and dynamics of giant unilamellar vesicles (GUVs) comprised of 1,2-dilauroyl-sn-glycero-3-phosphatidylcholine (DLPC) is reported. The investigations were conducted by using optical fluorescence microscopy as the method of analysis. The lipid membrane of the DLPC GUVs at the fluid phase can be deformed and they migrate towards the electrodes under AC electric field. Nevertheless, membrane disruption or vesicle fusion was never noticed. The addition of concentrated glucose solution influences the osmotic pressure of the system leading to the formation of filaments at the outer region of the GUVs. These long flexible cylinders do not retract spontaneously. However, the application of AC electric field (20 V/mm, 20 Hz) enables the filaments to be retracted back to the GUVs membrane at a calculated speed of 0.18 μm.s-1
关键词： Electric field,GUVs,Fluorescence microscopy,DLPC
更新于2025-09-09 09:28:46
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Manipulating and monitoring nanoparticles in micellar thin film superstructures
摘要： Understanding the dynamics of discrete self-assembled structures under influence of external triggers is of interest to harvest the potential of nano- and mesoscale materials. In particular, controlling the hierarchical organization of (macro)molecular and nanoparticle building blocks in monolayer superstructures is of paramount importance for tuning properties and characteristics. Here we show how the electron beam in cryo-transmission electron microscopy can be exploited to induce and follow local migration of building blocks and global migration of micellar aggregates inside micrometer-sized superstructures. We employ stroboscopic exposure to heat up and convert the vitrified superstructure into a liquid-like thin film under cryogenic conditions, resulting in controlled evaporation of water that finally leads to rupture of the micelle-containing superstructure. Micelle-embedded nanoparticles prove a powerful tool to study the complex hierarchically built-up superstructures, and to visualize both global movement of individual dendrimicelles and local migration of nanoparticles inside the micellar core during the exposure series.
关键词： cryo-transmission electron microscopy,self-assembly,nanoparticles,hierarchical organization,micellar thin film
更新于2025-09-09 09:28:46