Search results for "Microscopy"
showing 10 items of 3390 documents
Supramolecular assembly using helical peptides
1997
Abstract We investigated supramolecular assemblies of various hydrophobic helical peptides. The assemblies were formed at the air/water interface or in aqueous medium. The hexadecapeptide, Boc-(Ala-Aib)8-OMe (BA16M), was reported to take α-helical structure by X-ray analysis. Several derivatives were prepared, which have the repeating sequence of Ala-Aib, Lys(Z)-Aib or Leu-Aib, or have the terminal chemically modified. CD spectra of the peptides indicated helical conformation in ethanol solution. The surface pressure-area isotherms of the peptide monolayers showed an inflection at the surface area corresponding to the cross section along the helix axis, and the monolayers were collapsed by …
Energy landscapes of ligand-receptor couples probed by dynamic force spectroscopy.
2013
Playing a dominant role in many biochemical processes are the dynamic properties of molecular linkages; examples include cell adhesion, enzyme-catalyzed reactions, and molecular recognition by antibodies. Dynamic force spectroscopy, namely separating molecular bonds under external force ramps has rapidly become a powerful tool to study the rugged energy landscape of noncovalent ligand-receptor bonds. The picture shows a surface and tip-bound pair being pulled apart and the derived potential energy diagram.
New Tools for Characterizing Metallic Nanoparticles: AgNPs, A Case Study.
2015
Currently, transmission electron microscopy (TEM) is the main technique for estimating the sizes of spherical nanoparticles (NPs) and through them, their concentrations. This paper demonstrates for the first time that C18 reversed-phase capillary liquid chromatography (Cap-LC) coupled to diode array detection (DAD) has the potential to estimate mean concentrations of silver nanoparticles (AgNPs) and thereby determine their average size. Direct injection of the sample without previous extraction or separation steps is carried out. Only a unique standard with a known AgNP size is needed for the calibration. In a first approach, the new method has been tested over silver nanoparticles, produce…
Confocal microscopy of single molecules of the green fluorescent protein
1998
Single molecule detection has been extended into life sciences by use of strongly fluorescent labels. The green fluorescent protein (GFP) as a self-fluorescent biomolecule has attracted considerable attention. Here, single molecules of the GFP-mutant Glu222Gln are immobilized in a polyvinylalcohol matrix and detected by confocal fluorescence microscopy. Although this mutant stabilizes one of both conformers of the wild-type GFP, the investigation of its fluorescence dynamics reveals strong signal fluctuations. This fluorescence behaviour is—at least partly—caused by reversible photochemical changes of the protein framework, that can relax into the fluorescent state on different timescales. …
Dating archeological lead artifacts from measurement of the corrosion content using the voltammetry of microparticles.
2011
A methodology for dating archeological lead artifacts based on the voltammetry of microparticles is described. This methodology is based on the comparison of the height of speci¿c voltammetric features from PbO2 and PbO corrosion products formed under long-term alteration conditions. Calibration of the method was performed with the help of a series of well-documented lead pieces from the funds of di¿erent museums of the Comunitat Valenciana (Spain) covering from the ¿fth century B.C. to present day. The variation of peak currents with the time of corrosion can be¿tted to the same potential rate law as that found by Reich (R = 0.070 ( 0.005), using measurements on the Meissner fraction in th…
Self-trapped exciton luminescence in crystalline α-quartz under two-photon laser excitation
2003
Abstract The luminescence of pure crystalline α-quartz is studied under pulsed ArF laser excitation. The luminescence parameters obtained correspond well with those of self-trapped excitons (STEs) in α-quartz, indicating that the excitation process is two-photon. The efficiency of two-photon excitation is of the same order of magnitude as the one-photon excitation of sodium salicylate. The STE luminescence decay kinetics and their temperature dependence under photoexcitation were recorded with higher accuracy than previously. Changes in the decay kinetics with temperature are explained by the splitting of the STE triplet state in zero magnetic field and are analyzed with the assumption of t…
Voltammetry of microparticles, scanning electrochemical microscopy and scanning tunneling microscopy applied to the study of dsDNA binding and damage…
2014
Abstract Microparticulate deposits of scorpiand-like azamacrocyclic receptors (L1–L4) attached to graphite electrodes provide distinctive voltammetric features in contact with aqueous DNA solutions at biological pH, denoting the formation of DNA surface complexes. This voltammetry allows for screening dsDNA, ssDNA and G-Quadruplex DNA using L4-modified electrodes. Scanning electrochemical microscopy and scanning tunneling microscopy examination of dsDNA fibers attached to the substrate electrode in contact with DMSO solutions containing ferrocene and receptor indicate that a synergic effect is exerted between electrochemically generated ferrocenium ion and the receptors so that they increas…
On-Surface Synthesis of Unsaturated Carbon Nanostructures with Regularly Fused Pentagon–Heptagon Pairs
2020
Multiple fused pentagon-heptagon pairs are frequently found as defects at the grain boundaries of the hexagonal graphene lattice and are suggested to have a fundamental influence on graphene-related materials. However, the construction of sp2-carbon skeletons with multiple regularly fused pentagon-heptagon pairs is challenging. In this work, we found that the pentagon-heptagon skeleton of azulene was rearranged during the thermal reaction of an azulene-incorporated organometallic polymer on Au(111). The resulting sp2-carbon frameworks were characterized by high-resolution scanning probe microscopy techniques and feature novel polycyclic architectures composed of multiple regularly fused pen…
Tuning the Magnetic Properties of Carbon by Nitrogen Doping of Its Graphene Domains
2015
Here we present the formation of predominantly sp-coordinate carbon with magnetic- and heteroatom-induced structural defects in a graphene lattice by a stoichiometric dehalogenation of perchlorinated (hetero)aromatic precursors [hexachlorobenzene, CCl (HCB), and pentachloropyridine, NCCl (PCP)] with transition metals such as copper in a combustion synthesis. This route allows the build-up of a carbon lattice by a chemistry free of hydrogen and oxygen compared to other pyrolytic approaches and yields either nitrogen-doped or -undoped graphene domains depending on the precursor. The resulting carbon was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM…