Buchbesprechungen

Ohne Zusammenfassung     

Time multiplexing and parallelization in multifocal multiphoton microscopy

We investigate the imaging properties of high-aperture multifocal multiphoton microscopy on the basis of diffraction theory. Particular emphasis is placed on the relationship between the sectioning property and the distance between individual foci. Our results establish a relationship between the degree of parallelization and the axial resolution for both two- and three-photon excitation. In addition, we show quantitatively that if a matrix of temporal delays is inserted between the individual foci, it is, for the first time to our knowledge, possible to solve the classical conflict between the light budget and the sectioning property in three-dimensional microscopy and to provide a virtually unlimited density of foci at best axial resolution.     

Physik

Ohne Zusammenfassung     

Physik

Ohne Zusammenfassung     

Reversible photoswitching enables single-molecule fluorescence fluctuation spectroscopy at high molecular concentration

We demonstrate that photoswitchable markers enable fluorescence fluctuation spectroscopy at high molecular concentration. Reversible photoswitching allows precise control of the density of fluorescing entities, because the equilibrium between the fluorescent ON- and the dark OFF-state can be shifted through optical irradiation at a specific wavelength. Depending on the irradiation intensity, the concentration of the ON-state markers can be up to 1,000 times lower than the actual concentration of the labeled molecular entity. Photoswitching expands the range of single-molecule detection based experiments such as fluorescence fluctuation spectroscopy to large entity concentrations in the micromolar range.     

Characterization of nanostructured surfaces generated by reconstitution of the porin MspA from Mycobacterium smegmatis

Nanostructures with long-term stability at the surface of gold electrodes are generated by reconstituting the porin MspA from Mycobacterium smegmatis into a specially designed monolayer of long-chain lipid surfactant on gold. Tailored surface coverage of gold electrodes with long-chain surfactants is achieved by electrochemically assisted deposition of organic thiosulfates (Bunte salts). The subsequent reconstitution of the octameric-pore MspA is guided by its extraordinary self-assembling properties. Importantly, electrochemical reduction of copper(II) yields copper nanoparticles within the MspA nanopores. Electrochemical impedance spectroscopy, reflection electron microscopy, and atomic force microscopy (AFM) show that: 1) the MspA pores within the self-assembled monolayer (SAM) are monodisperse and electrochemically active, 2) MspA reconstitutes in SAMs and with a 10-nm thickness, 3) AFM is a suitable method to detect pores within SAMs, and 4) the electrochemical reduction of Cu2+ to Cu0 under overpotential conditions starts within the MspA pores.     

Schrifttumsberichte

Ohne Zusammenfassung