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171.
Surface-attached nanobubbles are spherical cap–shaped gas bubbles that remain stable in size in saturated liquids. Their positional stability resulted in a manifold of experimental techniques to record their topography, softness, and chemical composition. Here, we summarize these techniques and how to distinguish them from nongaseous objects commonly found on surfaces in contact with liquids. 相似文献
172.
We demonstrate the capability of differential interference contrast (DIC) microscopy as a simple and useful tool for studying
cellular events without fluorescence labeling. By coupling an advanced DIC microscope to a computer-controlled motorized vertical
stage and a high-speed, high-resolution CCD camera, real-time three-dimensional monitoring is possible in a high-throughput
manner. The performance among three modes of microscopy, bright-field, dark-field and DIC, in terms of horizontal resolving
power and vertical sectioning was investigated. As a model, exocytosis of rat peritoneal mast cells was recorded on the subsecond
time scale. Three-dimensional tracking of granules during degranulation was achieved and granule–granule fusion before plasma
membrane fusion was recorded.
Electronic Supplementary Material Supplementary material is available for this article at 相似文献
173.
174.
Dr. Maria Dell Dr. Mai Anh Tran Dr. Michael J. Capper Dr. Srividhya Sundaram Jonas Fiedler Prof. Dr. Jesko Koehnke Prof. Dr. Ute A. Hellmich Prof. Dr. Christian Hertweck 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2024,136(9):e202315850
Modular polyketide synthases (PKSs) are giant assembly lines that produce an impressive range of biologically active compounds. However, our understanding of the structural dynamics of these megasynthases, specifically the delivery of acyl carrier protein (ACP)-bound building blocks to the catalytic site of the ketosynthase (KS) domain, remains severely limited. Using a multipronged structural approach, we report details of the inter-domain interactions after C−C bond formation in a chain-branching module of the rhizoxin PKS. Mechanism-based crosslinking of an engineered module was achieved using a synthetic substrate surrogate that serves as a Michael acceptor. The crosslinked protein allowed us to identify an asymmetric state of the dimeric protein complex upon C−C bond formation by cryo-electron microscopy (cryo-EM). The possible existence of two ACP binding sites, one of them a potential “parking position” for substrate loading, was also indicated by AlphaFold2 predictions. NMR spectroscopy showed that a transient complex is formed in solution, independent of the linker domains, and photochemical crosslinking/mass spectrometry of the standalone domains allowed us to pinpoint the interdomain interaction sites. The structural insights into a branching PKS module arrested after C−C bond formation allows a better understanding of domain dynamics and provides valuable information for the rational design of modular assembly lines. 相似文献
175.
Chuyun Deng 《Talanta》2010,82(2):771-882
Fluorescence resonance energy transfer (FRET) is widely used to obtain the distance between a donor and an acceptor in biological research. However, the detection of FRET efficiencies with fluorescence microscopy imaging systems remains a great challenge due to the difficulties of transferring gray scales of the images into fluorescence intensities, and the absence of exact quantum yields of donors and acceptors. Herein, we presented a new method to detect the FRET efficiency in imaging systems by analyzing the photo-bleaching-induced changes in fluorescent intensities of quantum dots (QDs, donors) and Cy5 dyes (acceptors). Our method is different from the previous acceptor-photo-bleaching studies in imaging systems by theoretically analyzing the bleaching process, and bringing forward a new parameter which is universal for samples of the same kind. It is convenient for calculating FRET efficiencies. There is hardly any spectral crosstalk between 605QD and Cy5, thus the FRET result is more accurate than that of many other common FRET pairs. The lengths of single-stranded and double-stranded DNA fragments in solution were determined via the analysis of FRET efficiency values. This technique provides a reliable approach to study biomacromolecules in living cells through fluorescent imaging and in situ measurements. 相似文献
176.
177.
O. Sandig J. Herrero-Albillos F.M. Römer N. Friedenberger J. Kurde T. Noll M. Farle F. Kronast 《Journal of Electron Spectroscopy and Related Phenomena》2012
The Spin-resolved Photoelectron Emission Microscope (SPEEM) is a permanently installed set-up at Helmholtz-Zentrum Berlin (HZB). Due to its specific contrast it is mainly used for magnetic imaging and micro-spectroscopy with quantitative analysis. A crucial point in magnetic imaging is the application of magnetic fields. Many experiments require observation of magnetic responses or the preparation of a certain magnetic state during the measurement. We present a dedicated magnetic sample holder combining magnetic field during imaging with additional temperature control. This set-up enables SPEEM to measure magnetization curves of individual Fe nanocubes (18 nm)3 in size. If additionally alternating magnetic fields are applied we can image the local magnetic AC susceptibility (χAC) as a function of temperature. The latter is ideally suited to visualize local variations of the Curie temperature (TC) in nano- and microstructures. 相似文献
178.
P.A. Mosier-Boss L.P.G. ForsleyP. Carbonnelle M.S. MoreyJ.R. Tinsley J.P. HurleyF.E. Gordon 《Radiation measurements》2012,47(1):57-66
A solid state nuclear track detector, CR-39, was exposed to DT neutrons. After etching, the resultant tracks were analyzed using both an optical microscope and a scanning electron microscope (SEM). In this communication, both methods of analyzing DT neutron tracks are discussed. 相似文献
179.
Átila Madureira Bueno José Manoel Balthazar 《Communications in Nonlinear Science & Numerical Simulation》2012,17(7):3101-3111
Since the mid 1980s the Atomic Force Microscope is one the most powerful tools to perform surface investigation, and since 1995 Non-Contact AFM achieved true atomic resolution. The Frequency-Modulated Atomic Force Microscope (FM-AFM) operates in the dynamic mode, which means that the control system of the FM-AFM must force the microcantilever to oscillate with constant amplitude and frequency. However, tip-sample interaction forces cause modulations in the microcantilever motion. A Phase-Locked loop (PLL) is used to demodulate the tip-sample interaction forces from the microcantilever motion. The demodulated signal is used as the feedback signal to the control system, and to generate both topographic and dissipation images. As a consequence, a proper design of the PLL is vital to the FM-AFM performance. In this work, using bifurcation analysis, the lock-in range of the PLL is determined as a function of the frequency shift (Ω) of the microcantilever and of the other design parameters, providing a technique to properly design the PLL in the FM-AFM system. 相似文献
180.
Guohai Situ Michael Warber Giancarlo Pedrini Wolfgang Osten 《Optics Communications》2010,283(7):1273-1277
We demonstrate two methods based on Fourier plane filtering using (a) a fractional spiral phase plate (SPP) and (b) an off-axial SPP for phase contrast enhancement in optical microscopy. In comparison to previous works, a spatially incoherent LED is used in the Köhler illumination as the light source to illuminate the biological specimen. We demonstrate that both these methods can transform the phase specimen into a relief-like view even under such illumination. The degree and orientation of enhancement can be controlled by changing the phase structure of the filter. The SPP is displayed on a phase-only spatial light modulator, and can be integrated into the optical path of standard microscopes. 相似文献