Search results for "Microscopy."
showing 10 items of 3331 documents
Probing DNA conductivity with photoinduced electron transfer and scanning tunneling microscopy.
2012
Abstract The possibility that the stacked DNA bases can mediate vectorial electron transfer has been examined using two different approaches. Experiments on photoinduced electron transfer with intercalated donors and acceptors (either randomly bound or linked dyads of ruthenium complex and viologen) indicate that while DNA may be a better medium than acetonitrile for electron transfer over short distances (2-3-base pair, equivalent to 10-14Å centre-to-centre separation), it is a poor medium for transport over larger separations. Attempts to measure conductivity of individual DNA molecules using scanning tunneling microscopy to image mixed monolayers of mercaptohexanol (MCH) and 30-mer or 10…
Time-of-flight photoemission electron microscopy – a new way to chemical surface analysis
2001
Abstract The time structure of synchrotron radiation at BESSY I (Berlin) was utilised to operate a photoemission electron microscope in the time-of-flight mode. The electrons that are emitted from the sample surface with different energies are dispersed in a drift tube subsequent to the imaging optics. Two ways of fast image detection have been explored, a fast gated intensified CCD camera (800 ps gate time) and a special counting electronics in combination with a 3D (x,y,t)-resolving delay line detector ( time resolution ps). The latter device has a lateral resolution of about 50 μm in the image plane being equivalent to 1000 pixels along the image diagonal. An energy resolution of 400 meV…
Vertical and lateral drift corrections of scanning probe microscopy images
2010
A procedure is presented for image correction of scanning probe microscopy data that is distorted by linear thermal drift. The procedure is based on common ideas for drift correction, which the authors combine to a comprehensive step-by-step description of how to measure drift velocities in all three dimensions and how to correct the images using these velocities. The presented method does not require any knowledge about size or shape of the imaged structures. Thus, it is applicable to any type of scanning probe microscopy image, including images lacking periodic structures. Besides providing a simple, ready-to-use description of lateral and vertical drift correction, they derive all formul…
"Sweet Chemistry": a Green Way for Obtaining Selenium Nanoparticles Active against Cancer Cells
2017
We present an environment friendly synthesis of selenium nanoparticles and the study of their cytotoxic activity against uterine sarcoma cancer and fibroblasts cells. Amorphous selenium (a-SeNPs) and trigonal selenium (t-SeNPs) were synthesized using D-fructose as the reducing agent and characterized by high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDX), powder X-ray diffraction analysis (XRD), inductively coupled plasma optical emission spectrometry (ICP OES), dynamic light scattering (DLS) to obtain zeta potential values and cyclic voltammetry (CV). Particularly, a-SeNPs presented high toxicity toward the resistant cancer cell line MES-SA/…
The Contribution of Microscopy to the Study of Alzheimer’s Disease, Amyloid Plaques and Aβ Fibrillogenesis
2006
A broad survey is presented in this chapter, dealing with the impact that microscopy has made to the study of Alzheimer’s disease, amyloid plaques and amyloid-β fibrillogenesis. This includes classical light microscopy and the modern immunolabelling and confocal microscopies, together with the contribution of transmission electron microscopy and atomic force microscopy. Whilst usefully standing alone, the individual microscopies often contribute most effectively when they are integrated with cellular, biophysical and molecular approaches.
Chemokine Expression Is Involved in the Vascular Neogenesis of Ewing Sarcoma: A Preliminary Analysis of the Early Stages of Angiogenesis in a Xenogra…
2018
Background Ewing sarcoma (EWS) is the second most common bone cancer in pediatric patients. Angiogenesis is a major factor for tumor growth and metastasis. Our aim was to carry out a histological, immunohistochemical, and molecular characterization of the neovascularization established between xenotransplanted tumors and the host during the initial phases of growth in nude mice in three angiogenesis experiments (ES2, ES3, and ES4). Methods The original human EWS were implanted subcutaneously on the backs of three nude mice. Tumor pieces 3 mm–4 mm in size from early passages of Nu432, Nu495, and Nu471 were also implanted subcutaneously on the backs of three sets (ES2, ES3, and ES4) of athymi…
Activation of PPARβ/δ inhibits leukocyte recruitment, cell adhesion molecule expression, and chemokine release
2009
Abstract Activation of the nuclear receptor PPARb/d inhibits acute inflammatory responses in vitro with human primary cells and in vivo by targeting the endothelial cell-leukocyte interaction. The infiltration of PMNs into tissues is a prominent feature in inflammation. The mechanism underlying PMN recruitment depends on the release of chemotactic mediators and CAM expression on endothelial cells. The nuclear receptor PPARβ/δ is widely expressed in many tissues, including the vascular endothelium; however, its role in acute inflammation remains unclear. Using intravital microscopy in the mouse cremasteric microcirculation, we have shown that activation of PPARβ/δ by its selective ligand GW5…
Supramolecular PEG-co-oligo(p-benzamide)s prepared on a peptide synthesizer.
2007
An automated synthesis protocol has been developed for the preparation of oligo(p-benzamide)s on solid support using a commercial peptide synthesizer employing a variation of standard Fmoc chemistry. Bis(trichloromethyl carbonate) in NMP was used to activate the aromatic carboxylic acids for acylation of secondary aromatic amines on solid support. N-Protected hepta(p-benzamide) was automatically prepared on solid support and manually converted to a solid supported block co-oligomer by attaching a poly(ethylene glycol) chain. Cleavage from the support could be achieved with minimal loss of the p-methoxybenzyl N-protective group. While the N-protected block co-oligomer was molecularly dissolv…
Hierarchical Self-Organization of Perylene Bisimide–Melamine Assemblies to Fluorescent Mesoscopic Superstructures
2000
A series of three perylene tetracarboxylic acid bisimide dyes 3a-c bearing phenoxy substituents at the four bay positions of the perylene core were synthesized and their complexation behavior to complementary ditopic dialkyl melamines 8a-c was investigated. Binding constants and Gibbs binding energies for the hydrogen bonds between the imide and the complementary melamine moiety have been determined in several solvents by NMR and UV/Vis titration experiments with monotopic model compounds 5 and 9. The effects of the solvent polarity and specific solvent-solute interactions on the degree of polymerization of (3 x 8)n are discussed, and a general formula to estimate the chain length of [AA-BB…
Modulation of the growth and metabolic response of cyanobacteria by the multifaceted activity of naringenin
2017
The interactions between the plant-derived bioflavonoid, naringenin, and prokaryotic microalgae representatives (cyanobacteria), were investigated with respect to its influence on the growth and metabolic response of these microorganisms. To achieve reliable results, the growth of cyanobacteria was determined based on measurements of chlorophyll content, morphological changes were assessed through microscopic observations, and the chemical response of cells was determined using liquid and gas chromatography (HPLC; GC-FID). The results show that micromolar levels of naringenin stimulated the growth of cyanobacteria. Increased growth was observed for halophilic strains at naringenin concentra…