Effect of Disorder on Ultrafast Exciton Dynamics Probed by Single Molecule Spectroscopy

We present a single-molecule study unraveling the effect of static disorder on the vibrational-assisted ultrafast exciton dynamics in multichromophoric systems. For every single complex, we probe the initial exciton relaxation process by an ultrafast pump-probe approach and the coupling to vibrational modes by emission spectra, while fluorescence lifetime analysis measures the amount of static disorder. Exploiting the wide range of disorder found from complex to complex, we demonstrate that static disorder accelerates the dephasing and energy relaxation rate of the exciton

TANGO1 builds a machine for collagen export by recruiting and spatially organizing COPII, tethers and membranes

Collagen export from the endoplasmic reticulum (ER) requires TANGO1, COPII coats, and retrograde fusion of ERGIC membranes. How do these components come together to produce a transport carrier commensurate with the bulky cargo collagen? TANGO1 is known to form a ring that corrals COPII coats, and we show here how this ring or fence is assembled. Our data reveal that a TANGO1 ring is organized by its radial interaction with COPII, and lateral interactions with cTAGE5, TANGO1-short or itself. Of particular interest is the finding that TANGO1 recruits ERGIC membranes for collagen export via the NRZ (NBAS/RINT1/ZW10) tether complex. Therefore, TANGO1 couples retrograde membrane flow to anterograde cargo transport. Without the NRZ complex, the TANGO1 ring does not assemble, suggesting its role in nucleating or stabilising this process. Thus, coordinated capture of COPII coats, cTAGE5, TANGO1-short, and tethers by TANGO1 assembles a collagen export machine at the ER.V Malhotra is an Institució Catalana de Recerca i Estudis Avançats professor at the Centre for Genomic Regulation, the work in his laboratory is funded by grants from the Ministerio de Economía, Industria y Competitividad Plan Nacional (ref. BFU2013-44188-P) and Consolider (CSD2009-00016). We acknowledge support of the Spanish Ministry of Economy and Competitiveness, through the Programmes ‘Centro de Excelencia Severo Ochoa 2013–2017’ (SEV-2012–0208) and Maria de Maeztu Units of Excellence in R and D (MDM-2015–0502). We acknowledge the support of the CERCA Programme/Generalitat de Catalunya. F Campelo and M García-Parajo acknowledge support by the Spanish Ministry of Economy and Competitiveness (‘Severo Ochoa’ Programme for Centres of Excellence in R and D (SEV-2015–240522) and FIS2014-56107-R), BFU2015-73288-JIN, AEI/FEDER; UE, Fundacion Privada Cellex, HFSP (GA RGP0027/2012), EC FP7-NANO-VISTA (GA 288263) and LaserLab 4 Europe (GA 654148). I. Raote and F. Campelo acknowledge support by the BIST Ignite Grant (eTANGO)

TANGO1 builds a machine for collagen export by recruiting and spatially organizing COPII, tethers and membranes

Collagen export from the endoplasmic reticulum (ER) requires TANGO1, COPII coats, and retrograde fusion of ERGIC membranes. How do these components come together to produce a transport carrier commensurate with the bulky cargo collagen? TANGO1 is known to form a ring that corrals COPII coats, and we show here how this ring or fence is assembled. Our data reveal that a TANGO1 ring is organized by its radial interaction with COPII, and lateral interactions with cTAGE5, TANGO1-short or itself. Of particular interest is the finding that TANGO1 recruits ERGIC membranes for collagen export via the NRZ (NBAS/RINT1/ZW10) tether complex. Therefore, TANGO1 couples retrograde membrane flow to anterograde cargo transport. Without the NRZ complex, the TANGO1 ring does not assemble, suggesting its role in nucleating or stabilising this process. Thus, coordinated capture of COPII coats, cTAGE5, TANGO1-short, and tethers by TANGO1 assembles a collagen export machine at the ER.V Malhotra is an Institució Catalana de Recerca i Estudis Avançats professor at the Centre for Genomic Regulation, the work in his laboratory is funded by grants from the Ministerio de Economía, Industria y Competitividad Plan Nacional (ref. BFU2013-44188-P) and Consolider (CSD2009-00016). We acknowledge support of the Spanish Ministry of Economy and Competitiveness, through the Programmes ‘Centro de Excelencia Severo Ochoa 2013–2017’ (SEV-2012–0208) and Maria de Maeztu Units of Excellence in R and D (MDM-2015–0502). We acknowledge the support of the CERCA Programme/Generalitat de Catalunya. F Campelo and M García-Parajo acknowledge support by the Spanish Ministry of Economy and Competitiveness (‘Severo Ochoa’ Programme for Centres of Excellence in R and D (SEV-2015–240522) and FIS2014-56107-R), BFU2015-73288-JIN, AEI/FEDER; UE, Fundacion Privada Cellex, HFSP (GA RGP0027/2012), EC FP7-NANO-VISTA (GA 288263) and LaserLab 4 Europe (GA 654148). I. Raote and F. Campelo acknowledge support by the BIST Ignite Grant (eTANGO)

Sphingomyelin metabolism controls the shape and function of the Golgi cisternae

The flat Golgi cisterna is a highly conserved feature of eukaryotic cells, but how is this morphology achieved and is it related to its function in cargo sorting and export? A physical model of cisterna morphology led us to propose that sphingomyelin (SM) metabolism at the trans-Golgi membranes in mammalian cells essentially controls the structural features of a Golgi cisterna by regulating its association to curvature-generating proteins. An experimental test of this hypothesis revealed that affecting SM homeostasis converted flat cisternae into highly curled membranes with a concomitant dissociation of membrane curvature-generating proteins. These data lend support to our hypothesis that SM metabolism controls the structural organization of a Golgi cisterna. Together with our previously presented role of SM in controlling the location of proteins involved in glycosylation and vesicle formation, our data reveal the significance of SM metabolism in the structural organization and function of Golgi cisternae.FC and MGP acknowledge support by the Spanish Ministry of Economy and Competitiveness ('Severo Ochoa' Programme for Centres of Excellence in R and D (SEV-2015-240522) and FIS2014-56107-R), BFU2015-73288-JIN, AEI/FEDER;UE, Fundacion Privada Cellex, HFSP (GA RGP0027/2012), EC FP7-NANO-VISTA (GA 288263) and LaserLab 4 Europe (GA 654148). MMK is supported by the Israel Science Foundation. VM acknowledges support from the Spanish Ministry of Economy and Competitiveness through the Programme 'Centro de Excelencia Severo Ochoa 2013-298 2017' (SEV-2012-0208); and support from the CERCA Programme / Generalitat de Catalunya. VM is an Institucio´ Catalana de Recerca i Estudis Avanc¸ ats (ICREA) professor at the Center for Genomic Regulation and the work in his laboratory is funded by grants from MINECO's Plan Nacional (BFU2013-44188-P), Consolider (CSD2009-00016), and European Research Council (268692). The project has received research funding from the European Union

Plasmonic Nanoantennas Enable Forbidden Förster Dipole-Dipole Energy Transfer and Enhance the FRET Efficiency

Förster resonance energy transfer (FRET) plays a key role in biochemistry, organic photovoltaics, and lighting sources. FRET is commonly used as a nanoruler for the short (nanometer) distance between donor and acceptor dyes, yet FRET is equally sensitive to the mutual dipole orientation. The orientation dependence complicates the FRET analysis in biological samples and may even lead to the absence of FRET for perpendicularly oriented donor and acceptor dipoles. Here, we exploit the strongly inhomogeneous and localized fields in plasmonic nanoantennas to open new energy transfer routes, overcoming the limitations from the mutual dipole orientation to ultimately enhance the FRET efficiency. We demonstrate that the simultaneous presence of perpendicular near-field components in the nanoantenna sets favorable energy transfer routes that increase the FRET efficiency up to 50% for nearly perpendicular donor and acceptor dipoles. This new facet of plasmonic nanoantennas enables dipole–dipole energy transfer that would otherwise be forbidden in a homogeneous environment. As such, our approach further increases the applicability of single-molecule FRET over diffraction-limited approaches, with the additional benefits of higher sensitivities and higher concentration ranges toward physiological levels.Peer Reviewe

Effect of disorder on ultrafast exciton dynamics probed by single molecule spectroscopy

We present a single-molecule study unraveling the effect of static disorder on the vibrational-assisted ultrafast exciton dynamics in multichromophoric systems. For every single complex, we probe the initial exciton relaxation process by an ultrafast pump-probe approach and the coupling to vibrational modes by emission spectra, while fluorescence lifetime analysis measures the amount of static disorder. Exploiting the wide range of disorder found from complex to complex, we demonstrate that static disorder accelerates the dephasing and energy relaxation rate of the exciton

Single-Molecule Pump-Probe Detection Resolves Ultrafast Pathways in Individual and Coupled Quantum Systems

We report the first experimental study of individual molecules with femtosecond time resolution using a novel ultrafast single-molecule pump-probe method. A wide range of relaxation times from below 100 up to 400 fs is found, revealing energy redistribution over different vibrational modes and phonon coupling to the nanoenvironment. Addressing quantum-coupled molecules we find longer decay times, pointing towards inhibited intramolecular decay due to delocalized excitation. Interestingly, each individual system shows discrete jumps in femtosecond response, reflecting sudden breakup of the coupled superradiant state

All-Dielectric Silicon Nanogap Antennas To Enhance the Fluorescence of Single Molecules

International audiencePlasmonic antennas have a profound impact on nanophotonics as they provide efficient means to manipulate light and enhance light–matter interactions at the nanoscale. However, the large absorption losses found in metals can severely limit the plasmonic applications in the visible spectral range. Here, we demonstrate the effectiveness of an alternative approach using all-dielectric nanoantennas based on silicon dimers to enhance the fluorescence detection of single molecules. The silicon antenna design is optimized to confine the near-field intensity in the 20 nm nanogap and reach a 270-fold fluorescence enhancement in a nanoscale volume of λ3/1800 with dielectric materials only. Our conclusions are assessed by combining polarization resolved optical spectroscopy of individual antennas, scanning electron microscopy, numerical simulations, fluorescence lifetime measurements, fluorescence burst analysis, and fluorescence correlation spectroscopy. This work demonstrates that all-silicon nanoantennas are a valid alternative to plasmonic devices for enhanced single molecule fluorescence sensing, with the additional key advantages of reduced nonradiative quenching, negligible heat generation, cost-efficiency, and complementary metal–oxide–semiconductor (CMOS) compatibility