Indistinguishable Photons from a Single Molecule

We report the results of coincidence counting experiments at the output of a Michelson interferometer using the zero-phonon-line emission of a single molecule at $1.4 K$. Under continuous wave excitation, we observe the absence of coincidence counts as an indication of two-photon interference. This corresponds to the observation of Hong-Ou-Mandel correlations and proves the suitability of the zero-phonon-line emission of single molecules for applications in linear optics quantum computation.Comment: To appear in Phys. Rev. Let

Double-labelled HIV-1 particles for study of virus–cell interaction

AbstractHuman immunodeficiency virus (HIV) delivers its genome to a host cell through fusion of the viral envelope with a cellular membrane. While the viral and cellular proteins involved in entry have been analyzed in detail, the dynamics of virus–cell fusion are largely unknown. Single virus tracing (SVT) provides the unique opportunity to visualize viral particles in real time allowing direct observation of the dynamics of this stochastic process. For this purpose, we developed a double-coloured HIV derivative carrying a green fluorescent label attached to the viral matrix protein combined with a red label fused to the viral Vpr protein designed to distinguish between complete virions and subviral particles lacking MA after membrane fusion. We present here a detailed characterization of this novel tool together with exemplary live cell imaging studies, demonstrating its suitability for real-time analyses of HIV–cell interaction

Dynamics of HIV-1 Assembly and Release

Assembly and release of human immunodeficiency virus (HIV) occur at the plasma membrane of infected cells and are driven by the Gag polyprotein. Previous studies analyzed viral morphogenesis using biochemical methods and static images, while dynamic and kinetic information has been lacking until very recently. Using a combination of wide-field and total internal reflection fluorescence microscopy, we have investigated the assembly and release of fluorescently labeled HIV-1 at the plasma membrane of living cells with high time resolution. Gag assembled into discrete clusters corresponding to single virions. Formation of multiple particles from the same site was rarely observed. Using a photoconvertible fluorescent protein fused to Gag, we determined that assembly was nucleated preferentially by Gag molecules that had recently attached to the plasma membrane or arrived directly from the cytosol. Both membrane-bound and cytosol derived Gag polyproteins contributed to the growing bud. After their initial appearance, assembly sites accumulated at the plasma membrane of individual cells over 1–2 hours. Assembly kinetics were rapid: the number of Gag molecules at a budding site increased, following a saturating exponential with a rate constant of ∼5×10−3 s−1, corresponding to 8–9 min for 90% completion of assembly for a single virion. Release of extracellular particles was observed at ∼1,500±700 s after the onset of assembly. The ability of the virus to recruit components of the cellular ESCRT machinery or to undergo proteolytic maturation, or the absence of Vpu did not significantly alter the assembly kinetics

Inside Cover: Artificial Formation and Tuning of Glycoprotein Networks on Live Cell Membranes: A Single‐Molecule Tracking Study (ChemPhysChem 6/2016)

The trajectories of membrane proteins, which are artificially interconnected by biotin and streptavidin, are reminiscent of the work of action painters. This provided the inspiration to think of the different membrane biotin concentrations as colors that can be used to paint various networks onto cells by using the streptavidin brush. More information can be found in the Full Paper by C. Bräuchle et al. on page 829 in Issue 6, 2016 (DOI: 10.1002/cphc.201500809

Correlations between the ground state and the triplet state character orders of benzenoid hydrocarbons

The relative localization of the n-conjugation of benzenoid hydrocarbons in the ground state So and the lowest excited triplet state Ti is described by means of character orders. For molecules with the same unmber of electron sextets a linear correlation could be found between the mean character orders of So and Ti indicating the similarities in the electron distribution of these states. The relevance of this similarity for an earlier explanation of the zero-field splitting in Ti is give

PROPERTIES OF HOLOGRAPHIC MEDIA CONTAINING PURPLE MEMBRANE FROM HALOBACTERIUM HALOBIUM AND ITS FUNCTIONAL VARIANTS

Polymeric films of purple membrane (PM) from Halobacterium halobium, which contains the photochromic protein bacteriorhodopsin (BR) are well suited reversible media for holographic recording. The sensitivity (19 cm?/J), resolution (> 5000 lines/mm) and large spectral bandwidth (400 - 700 nm) of such films are absolutely comparable to the corres- ponding datas of the best known conventional photochromic materials for holography. By the development of a mutagenesis/selection procedure which allows to generate and isolate mutants of BR with modified photochemical characteristics, new possibilities raised to design bacteriorhodopsin based holographic recording media which cover the physical demands for different holographic applications like holographic storage and pattern recognition