The ultimate detection limit in analytic chemistry and biology is the single molecule. Commonly, fluorescent dye labels or enzymatic amplification are employed. This requires additional labeling of the analyte, which modifies the species under investigation and therefore influences biological processes. Here, we utilize single gold nanoparticles to detect single unlabeled proteins with extremely high temporal resolution. This allows for monitoring the dynamic evolution of a single protein binding event on a millisecond time scale. The technique even resolves equilibrium coverage fluctuations, opening a window into Brownian dynamics of unlabeled macromolecules. Therefore, our method enables the study of protein folding dynamics, protein adsorption processes, and kinetics as well as nonequilibrium soft matter dynamics on the single molecule level.
Cu@Fe 3 O 4 heteroparticles with distinct morphologies were synthesized from organometallic reactants. The shape of the magnetic domains could be controlled by the solvent and reaction conditions. They display magnetic and optical properties that are useful for simultaneous magnetic and optical detection. After functionalization, the Cu@Fe 3 O 4 heterodimers become water soluble. The morphology, structure, magnetic and optical properties of the as-synthesized heterodimer nanoparticles were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), m€ ossbauer spectroscopy, superconducting quantum interference device (SQUID) magnetometry, and dark field imaging. A special advantage of these heterodimers lies in the fact that the nanodomains of different composition can be used e.g. for the formation of nitric oxide (NO) through the Cu domain and heterodimer nanoparticles can be removed from the reaction mixture by means of the magnetic domain (Fe 3 O 4 ).
Eine elegante Strategie zur Herstellung von funktionalisierten Au@MnO‐Nanokristallen wurde entwickelt. Die magnetischen „Nanoblumen“ zeichnen sich nicht nur als effiziente Trägermaterialien für den spezifischen Stofftransport aus, sondern sie eignen sich nach der Bindung von Fluorophoren an die Au‐ und MnO‐Komponenten auch für die multimodale Fluoreszenzbildgebung.
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