Receptor Concentration and Diffusivity Control Multivalent Binding of Sv40 to Membrane Bilayers
Oliwia M. Szklarczyk,
Nélido González-Segredo,
Philipp Kukura,
Ariella Oppenheim,
Daniel Choquet,
Vahid Sandoghdar,
Ari Helenius,
Ivo F. Sbalzarini,
Helge Ewers
Incoming Simian Virus 40 particles bind to their cellular receptor, the glycolipid GM1, in the plasma membrane and thereby induce membrane deformation beneath the virion leading to endocytosis and infection. Efficient membrane deformation depends on receptor lipid structure and the organization of binding sites on the internalizing particle. To determine the role of receptor diffusion, concentration and the number of receptors required for stable binding in this interaction, we analyze the binding of SV40 to GM1 in supported membrane bilayers by computational modeling based on experimental data. We measure the diffusion rates of SV40 virions in solution by fluorescence correlation spectroscopy and of the receptor in bilayers by single molecule tracking. Quartz-crystal microbalance with dissipation (QCM-D) is used to measure binding of SV40 virus-like particles to bilayers containing the viral receptor GM1. We develop a phenomenological stochastic dynamics model calibrated against this data, and use it to investigate the early events of virus attachment to lipid membranes. Our results indicate that SV40 requires at least 4 attached receptors to achieve stable binding. We moreover find that receptor diffusion is essential for the establishment of stable binding over the physiological range of receptor concentrations and that receptor concentration controls the mode of viral motion on the target membrane. Our results provide quantitative insight into the initial events of virus-host interaction at the nanoscopic level.
Cryogenic localization of single molecules with angstrom precision
Siegfried Weisenburger,
Jing Bo,
Alois Renn,
Vahid Sandoghdar
The precision in localizing a molecule is ultimately determined by the number of detected photons, which is in turn limited by photobleaching. Currently, fluorophores can be routinely localized to a few tens of nanometers at room temperature. In this work we demonstrate localization precision better than 3 Angstrom by substantial improvement of the molecular photostability at cryogenic temperatures. We discuss the challenges, solutions and promise of our methodology for high-performance co-localization and super-resolution microscopy.
We provide a general theoretical platform based on quantized radiation in absorptive and inhomogeneous media for investigating the coherent interaction of light with material structures in the immediate vicinity of quantum emitters. In the case of a very small metallic cluster, we demonstrate extreme regimes where a single emitter can either counteract or enhance particle absorption by 3 orders of magnitude. For larger structures, we show that an emitter can eliminate both scattering and absorption and cloak a plasmonic antenna. We provide physical interpretations of our results and discuss their applications in active metamaterials and quantum plasmonics. DOI: 10.1103/PhysRevLett.110.153605
Measuring three-dimensional interaction potentials using optical
interference
Nassir Mojarad,
Vahid Sandoghdar,
Madhavi Krishnan
We describe the application of three-dimensional (3D) scattering interferometric (iSCAT) imaging to the measurement of spatial interaction potentials for nano-objects in solution. We study electrostatically trapped gold particles in a nanofluidic device and present details on axial particle localization in the presence of a strongly reflecting interface. Our results demonstrate high-speed (similar to kHz) particle tracking with subnanometer localization precision in the axial and average 2.5 nm in the lateral dimension. A comparison of the measured levitation heights of trapped particles with the calculated values for traps of various geometries reveals good agreement. Our work demonstrates that iSCAT imaging delivers label-free, high-speed and accurate 3D tracking of nano-objects conducive to probing weak and long-range interaction potentials in solution. (C) 2013 Optical Society of America
Gain-tunable optomechanical cooling in a laser cavity
Li Ge,
Sanli Faez,
Florian Marquardt,
Hakan E. Tuereci
Physical Review A
87
(5)
053839
(2013)
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| PDF
We study the optical cooling of the cavity mirror in an active laser cavity. We find that the optical damping rate is vanishingly small for an incoherently pumped laser above threshold. In the presence of an additional external coherent drive however, the optical damping rate can be enhanced substantially with respect to that of a passive cavity. We show that the strength of the incoherent pump provides the means to tune the optical damping rate and the steady state phonon number. The system is found to undergo a transition from the weak optomechanical coupling regime to the strong optomechanical coupling regime as the strength of the incoherent pump is varied.
Performance of scientific cameras with different sensor types in
measuring dynamic processes in fluorescence microscopy
Jasmin Jung,
Siegfried Weisenburger,
Sahradha Albert,
Daniel F. Gilbert,
Oliver Friedrich,
Volker Eulenburg,
Johannes Kornhuber,
Teja W. Groemer
Microscopy Research and Technique
76
835-843
(2013)
| Journal
The plethora of available scientific cameras of different types challenges the biologically oriented experimenter when picking the appropriate camera for his experiment. In this study, we chose to investigate camera performances in a typical nonsingle molecule situation in life sciences, that is, quantitative measurements of fluorescence intensity changes from video data with typically skewed intensity distributions. Here, intensity profile dynamics of pH-sensors upon triggered changes of pH-environments in living cells served as a model system. The following camera types were tested: sCMOS, CCD (scientific and nonscientific) and EM-CCD (back-and front-illuminated). We found that although the EM-CCD cameras achieved the best absolute spatial SNR (signal-to-noise ratio) values, the sCMOS was at least of equal performance when the spatial SNR was related to the effective dynamic range, and it was superior in terms of temporal SNR. In the measurements of triggered intensity changes, the sCMOS camera had the advantage that it used the smallest fraction of its dynamic range when depicting intensity changes, and thus featured the best SNR at full usage of its dynamic range. (C) 2013 Wiley Periodicals, Inc.
One-Step Synthesis of PEG-Coated Gold Nanoparticles by Rapid Microwave
Heating
Seung Kwon Seol,
Daeho Kim,
Sunshin Jung,
Won Suk Chang,
Ji Tae Kim
Polyethylene Glycol-(PEG-) coated gold nanoparticles (PEG-AuNPs) are synthesized by a one-step route with rapid microwave heating. Homogeneous nucleation of the primary gold particles is enhanced by increasing the applied microwave power during the initial stage of the synthesis, increasing the temperature ramping rate (R-r) and resulting in decreased size and improved uniformity of the synthesized PEG-AuNPs. Using rapid microwave heating, we successfully produce uniform colloidal PEG-AuNPs with an average diameter of 14.3 +/- 2.5 nm within a few minutes. By appropriate tuning of the growth parameters, microwave synthesis can produce largely colloidal PEG-AuNPs with high uniformity.
Mode structure and polaritonic contributions to the Casimir effect in a
magnetodielectric cavity
We present a full analysis of the mode spectrum in a cavity formed by two parallel plates, one of which is magnetodielectric (metamaterial) while the other one is metallic, and obtain dispersion relations in closed form. The optical properties of the cavity walls are described in terms of realistic models for effective permittivity and permeability. Surface polaritons, i.e., electromagnetic modes that have at least partly an evanescent character, are shown to dominate the Casimir interaction at small separations. We analyze in detail the s-polarized polaritons, which are a characteristic feature of a magnetodielectric configuration, and discuss their role in the repulsive Casimir force.
A class of nonparaxial accelerating optical waves is introduced. These are beams with a Bessel-like profile that are capable of shifting laterally along fairly arbitrary trajectories as the wave propagates in free space. The concept expands on our previous proposal of paraxial accelerating Bessel-like beams to include beams with subwavelength lobes and/or large trajectory angles. Such waves are produced when the phase at the input plane is engineered so that the interfering ray cones are made to focus along the prespecified path. When the angle of these cones is fixed, the beams possess a diffraction-free Bessel profile on planes that stay normal to their trajectory, which can be considered as a generalized definition of diffractionless propagation in the nonparaxial regime. The analytical procedure leading to these results is based on a ray-optics interpretation of Rayleigh-Sommerfeld diffraction and is presented in detail. The evolution of the proposed waves is demonstrated through a series of numerical examples and a variety of trajectories.
Ultrafast coherent nanoscopy
Xue-Wen Chen,
Ahmad Mohammadi,
Amir Hossein Baradaran Ghasemi,
Mario Agio
The dramatic advances of nanotechnology experienced in recent years enabled us to fabricate optical nanostructures or nano-antennas that greatly enhance the conversion of localised electromagnetic energy into radiation and vice versa. Nano-antennas offer the required improvements in terms of bandwidth, interaction strength and resolution for combining ultrafast spectroscopy, nano-optics and quantum optics to fundamentally push forward the possibility of the coherent optical access on individual nanostructures or even molecules above cryogenic temperatures, where dephasing processes typically occur at very short time scales. In this context, we discuss recent progress in the theoretical description of light-matter interaction at the nanoscale and related experimental findings. Moreover, we present concrete examples in support of our vision and propose a series of experiments that aim at exploring novel promising regimes of optical coherence and quantum optics in advanced spectroscopy. We envisage extensions to ultrafast and nonlinear phenomena, especially in the direction of multidimensional nanoscopy.
Antennas, quantum optics and near-field microscopy
Vahid Sandoghdar,
Mario Agio,
Xue-Wen Chen,
Stephan Götzinger,
Kwang-Geol Lee
The atom is the most elementary constituent of any model that describes the quantum nature of light–matter interaction. Because atoms emit and absorb light at well-defined frequencies, nineteenth century scientists thought of them as collections of harmonically oscillating electric dipole moments or EHDs. In the language of modern physics, the latter represent dipolar transitions among the various quantum mechanical states of an atom.<br><br>In a strict definition, the field of quantum optics deals with problems that not only require the quantization of matter but also of the electromagnetic field, with examples such as (i) generation of squeezed light or Fock states, (ii) strong coupling of an atom and a photon, (iii) entanglement of a photon with an atom and (iv) Casimir and van der Waals forces. There are also many other important topics that have been discussed within the quantum optics community but do not necessarily require a full quantum electrodynamic (QED) treatment. Examples are (i) cooling and trapping of atoms, (ii) precision spectroscopy and (iii) modification of spontaneous emission.<br><br>The simple picture of a TLS as an EHD remains very insightful and valuable to this day. Indeed, much of what we discuss in this chapter has to do with the interplay between the quantum and classical mechanical characters of dipolar oscillators. For instance, the extinction cross-section of a TLS, given by 3λ2/2π, can be derived just as well using quantum mechanics [70] or classical optics [234]. Another example, albeit more subtle, concerns the spontaneous emission rate.
Contact
Nano-Optics Division Prof. Vahid Sandoghdar
Max Planck Institute for the Science of Light Staudtstr. 2 91058 Erlangen, Germany
