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Microscopy Imaging (microscopy + imaging)
Selected AbstractsDirect Scanning Electron Microscopy Imaging of Ferroelectric Domains After Ion MillingJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2010Daniel Grüner A method for directly observing the ferroelectric domain structure by scanning electron microscopy after argon ion milling has been established. Its advantages are exemplified by exposing the domain structure in three widely used ferroelectric ceramics, BaTiO3, (Na,K)NbO3, and Pb(Ti,Zr)O3. Stable high-resolution images revealing domains with widths <30 nm have been obtained. The domain contrast is caused by electron channeling and is strongly dependent on the sample tilt angle. Owing to a strain- and defect-free surface generated by gentle ion milling, pronounced orientation contrast is observed. [source] Structure of the HIV-1 Rev response element alone and in complex with regulator of virion (Rev) studied by atomic force microscopyFEBS JOURNAL, Issue 15 2009Jesper Pallesen The interaction of multiple HIV-1 regulator of virion (Rev) proteins with the viral RNA target, the Rev response element (RRE), is critical for nuclear export of incompletely spliced and unspliced viral RNA, and for the onset of the late phase in the viral replication cycle. The heterogeneity of the Rev,RRE complex has made it difficult to study using conventional structural methods. In the present study, atomic force microscopy is applied to directly visualize the tertiary structure of the RRE RNA alone and in complex with Rev proteins. The appearance of the RRE is compatible with the earlier proposed RRE secondary structure in dimensions and overall shape, including a stalk and a head interpreted as stem I, and stem-loops II,V in the secondary structure model, respectively. Atomic force microscopy imaging of the Rev,RRE complex revealed an increased height of the structure both in the stalk and head regions, which is in accordance with a binding model in which Rev binding to a high affinity site in stem IIB triggers oligomerization of Rev proteins through cooperative binding along stem I in RRE. The present study demonstrates that atomic force microscopy comprises a useful technique to study complex biological structures of nucleic acids at high resolution. [source] Accelerating aging of zirconia femoral head implants: Change of surface structure and mechanical propertiesJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2007S. Chowdhury Abstract Recently, alternations of zirconia ceramic femoral heads of total hip prostheses during in vivo conditions have caused concern in the medical disciplines regarding phase transformation of zirconia prosthetic components. In this paper, we have investigated the mechanical and structural properties of different laboratory aged zirconia femoral heads and correlated changes in mechanical properties with the phase compositions of the sample. From laser microscope observation, cross-sectional Scanning electron microscopy imaging, and X-ray diffraction analysis on the surface of the zirconia femoral heads, we found monoclinic to tetragonal phase transformation in zirconia prostheses over time during the aging process in the laboratory. Mechanical properties, mainly hardness (H) and Young's modulus (E) values, were measured by nanoindentation technique on the surface of these implants. The results showed that both H and E values decreased with increased monoclinic phase in zirconia, thus confirming a phase transformation over time during aging. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006 [source] Novel biphasic traffic of endocytosed EGF to recycling and degradative compartments in lacrimal gland acinar cellsJOURNAL OF CELLULAR PHYSIOLOGY, Issue 1 2004Jiansong Xie The purpose of this study was to delineate the traffic patterns of EGF and EGF receptors (EGFR) in primary cultured acinar epithelial cells from rabbit lacrimal glands. Uptake of [125I]-EGF exhibited saturable and non-saturable, temperature-dependent components, suggesting both receptor-mediated and fluid phase endocytosis. Accumulation of [125I] was time-dependent over a 120-min period, but the content of intact [125I]-EGF decreased after reaching a maximum at 20 min. Analytical fractionation by sorbitol density gradient centrifugation and phase partitioning indicated that within 20 min at 37°C [125I] reached an early endosome, basal,lateral recycling endosome, pre-lysosome, and lysosome. Small components of the label also appeared to reach the Golgi complex and trans -Golgi network. Intact [125I]-EGF initially accumulated in the recycling endosome; the content in the recycling endosome subsequently decreased, and by 120 min increased amounts of [125I]-labeled degradation products appeared in the pre-lysosomes and lysosomes. Confocal microscopy imaging of FITC-EGF and LysoTrackerRed revealed FITC enriched in a dispersed system of non-acidic compartments at 20 min and in acidic compartments at 120 min. Both confocal immunofluorescence microscopy and analytical fractionation indicated that the intracellular EGFR pool was much larger than the plasma membrane-expressed pool at all times. Cells loaded with [125I]-EGF released a mixture of intact EGF and [125I]-labeled degradation products. The observations indicate that in lacrimal acinar cells, EGFR and EGF,EGFR complexes continually traffic between the plasma membranes and a system of endomembrane compartments; EGF-stimulation generates time-dependent signals that initially decrease, then increase, EGF,EGFR traffic to degradative compartments. J. Cell. Physiol. 199: 108,125, 2004© 2003 Wiley-Liss, Inc. [source] Preparation, characterization, and electrical properties of dual-emissive Langmuir-Blodgett films of some europium-substituted polyoxometalates and a platinum polyyne polymerJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2010Li Liu Abstract A new series of organometallic/inorganic composite Langmuir-Blodgett (LB) films consisting of a rigid-rod polyplatinyne polymer coordinated with 2,7-bis(buta-1,3-diynyl)-9,9-dihexylfluorene (denoted as PtP) as the ,-conjugated organometallic molecule, an europium-substituted polyoxometalate (POM; POM = Na9EuW10O36, K13[Eu(SiW11O39)2] and K5[Eu(SiW11O39)(H2O)2]) as the inorganic component, and an amphiphilic behenic acid (BA) as the auxiliary film-forming agent were prepared. Structural and photophysical characterization of these LB films were achieved by ,,A isotherms, absorption and photoluminescence spectra, atomic force microscopy imaging, scanning tunneling microscopy, and low-angle X-ray diffraction. Our experimental results indicate that stable, well-defined, and well-organized Langmuir and LB films are formed in pure water and POM subphases, and the presence of Eu-based POM in the subphase causes an area expansion. It is proposed that a lamellar layered structure exists for the PtP/BA/POM LB film in which the POM and PtP molecules can lay down with the interfacial planes. Luminescence spectra of the prepared hybrid LB films show that near-white emission spectra can be obtained due to the dual-emissive nature of the mixed PtP/POM blends. These Pt-polyyne-based LB films displayed interesting electric conductivity behavior. Among them, PtP/BA/POM 13-layer films showed a good electrical response, with the tunneling current up to ±100 nA when the voltage was monitored between ,1 and 7 V. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 879,888, 2010 [source] The effect of protein,precipitant interfaces and applied shear on the nucleation and growth of lysozyme crystalsACTA CRYSTALLOGRAPHICA SECTION D, Issue 11 2009Nuno M. Reis This paper is concerned with the effect of protein,precipitant interfaces and externally applied shear on the nucleation and growth kinetics of hen egg-white lysozyme crystals. The early stages of microbatch crystallization of lysozyme were explored using both optical and confocal fluorescence microscopy imaging. Initially, an antisolvent (precipitant) was added to a protein drop and the optical development of the protein,precipitant interface was followed with time. In the presence of the water-soluble polymer poly(ethylene glycol) (PEG) a sharp interface was observed to form immediately within the drop, giving an initial clear separation between the lighter protein solution and the heavier precipitant. This interface subsequently became unstable and quickly developed within a few seconds into several unstable `fingers' that represented regions of high concentration-gradient interfaces. Confocal microscopy demonstrated that the subsequent nucleation of protein crystals occurred preferentially in the region of these interfaces. Additional experiments using an optical shearing system demonstrated that oscillatory shear significantly decreased nucleation rates whilst extending the growth period of the lysozyme crystals. The experimental observations relating to both nucleation and growth have relevance in developing efficient and reliable protocols for general crystallization procedures and the controlled crystallization of single large high-quality protein crystals for use in X-ray crystallography. [source] Effects of hydrophobicity and anions on self-assembly of the peptide EMK16-IIBIOPOLYMERS, Issue 4 2010Dawei Zou Abstract Effects of hydrophobic and electrostatic interactions on the self-assembling process of the ionic-complementary peptide EMK16-II are investigated by atomic force microscopy imaging, circular dichroism spectra, light scattering, and chromatography. It is found that the hydrophobicity of the peptide promotes the aggregation in pure water even at a very low concentration, resulting in a much lower critical aggregation concentration than that of another peptide, EAK16-II. The effect of anions in solution with different valences on electrostatic interactions is also important. Monovalent anions (Cl, and Ac,) with a proper concentration can facilitate the formation of peptide fibrils, with Cl, of smaller size being more effective than Ac, of larger size. However, only small amounts of fibrils, but plenty of large amorphous aggregates, are found when the peptide solution is incubated with multivalent anions, such as SO, C6H5O, and HPO. More importantly, by gel filtration chromatography, the citrate anion, which induces a similar effect on the self-assembling process of EMK16-II as that of SO and HPO, can interact with two or more positively charged residues of the peptide and reside in the amorphous aggregates. This implies a "salt bridge" effect of multivalent anions on the peptide self-assembling process, which can interpret a previous puzzle why divalent cations inhibit the formation of ordered nanofibrils of the ionic-complementary peptides. Thus, our results clarify the important effects of hydrophobic and electrostatic interactions on the self-assembling process of the ionic-complementary peptides. These are greatly helpful for us to understand the mechanism of peptides' self-assembling process and protein folding and aggregation. © 2009 Wiley Periodicals, Inc. Biopolymers 93: 318,329, 2010. This article was originally published online as an acceptedpreprint. The "Published Online" date corresponds to the preprintversion. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Selective bioparticle retention and characterization in a chip-integrated confocal ultrasonic cavityBIOTECHNOLOGY & BIOENGINEERING, Issue 2 2009J. Svennebring Abstract We demonstrate selective retention and positioning of cells or other bioparticles by ultrasonic manipulation in a microfluidic expansion chamber during microfluidic perfusion. The chamber is designed as a confocal ultrasonic resonator for maximum confinement of the ultrasonic force field at the chamber center, where the cells are trapped. We investigate the resonant modes in the expansion chamber and its connecting inlet channel by theoretical modeling and experimental verification during no-flow conditions. Furthermore, by triple-frequency ultrasonic actuation during continuous microfluidic sample feeding, a set of several manipulation functions performed in series is demonstrated: sample bypass,injection,aggregation and retention,positioning. Finally, we demonstrate transillumination microscopy imaging of ultrasonically trapped COS-7 cell aggregates. Biotechnol. Bioeng. 2009;103: 323,328. © 2009 Wiley Periodicals, Inc. [source] Baculovirus-mediated immediate-early gene expression and nuclear reorganization in human cellsCELLULAR MICROBIOLOGY, Issue 3 2008Johanna P. Laakkonen Summary Baculovirus, Autographa californica multiple nucleopolyhedrovirus (AcMNPV), has the ability to transduce mammalian cell lines without replication. The general objective of this study was to detect the transcription and expression of viral immediate-early genes in human cells and to examine the interactions between viral components and subnuclear structures. Viral capsids were seen in large, discrete foci in nuclei of both dividing and non-dividing human cells. Concurrently, the transcription of viral immediate-early transregulator genes (ie-1, ie-2) and translation of IE-2 protein were detected. Quantitative microscopy imaging and analysis showed that virus transduction altered the size of promyelocytic leukaemia nuclear bodies, which are suggested to be involved in replication and transcription of various viruses. Furthermore, altered distribution of the chromatin marker Draq5Ō and histone core protein (H2B) in transduced cells indicated that the virus was able to induce remodelling of the host cell chromatin. To conclude, this study shows that the non-replicative insect virus, baculovirus and its proteins can induce multiple changes in the cellular machinery of human cells. [source] | ||||||||||||||||