Compartmentalization and Transport in Synthetic Vesicles
Christine Schmitt,
Anna H. Lippert,
Navid Bonakdar,
Vahid Sandoghdar,
Lars M. Voll
Frontiers in Bioengineering and Biotechnology
4
19
(2016)
| Journal
Nanoscale vesicles have become a popular tool in life sciences. Besides liposomes that are generated from phospholipids of natural origin, polymersomes fabricated of synthetic block copolymers enjoy increasing popularity, as they represent more versatile membrane building blocks that can be selected based on their specific physicochemical properties, such as permeability, stability, or chemical reactivity. In this review, we focus on the application of simple and nested artificial vesicles in synthetic biology. First, we provide an introduction into the utilization of multicompartmented vesosomes as compartmentalized nanoscale bioreactors. In the bottom-up development of protocells from vesicular nanoreactors, the specific exchange of pathway intermediates across compartment boundaries represents a bottleneck for future studies. To date, most compartmented bioreactors rely on unspecific exchange of substrates and products. This is either based on changes in permeability of the coblock polymer shell by physicochemical triggers or by the incorporation of unspecific porin proteins into the vesicle membrane. Since the incorporation of membrane transport proteins into simple and nested artificial vesicles offers the potential for specific exchange of substances between subcompartments, it opens new vistas in the design of protocells. Therefore, we devote the main part of the review to summarize the technical advances in the use of phospholipids and block copolymers for the reconstitution of membrane proteins.
Purely bianisotropic scatterers
M. Albooyeh,
V. S. Asadchy,
R. Alaee,
S. M. Hashemi,
M. Yazdi,
M. S. Mirmoosa,
C. Rockstuhl,
C. R. Simovski,
S. A. Tretyakov
We analyze the spectral properties of the reduced quantum fluctuations arising from a single two-level emitter coupled to an optical nanostructure. A closed expression for the squeezing spectrum in this hybrid system is presented that includes the effect of additional phase decoherence. We consider a metallic nanoantenna to illustrate how the hybrid system can increase the bandwidth and overcome the limits to the generation of such spectral squeezing in terms of driving field intensity and the effect of pure dephasing.
Phase-change material-based nanoantennas with tunable radiation patterns
We theoretically investigate the interaction of light and a collection of emitters in a subwavelength one-dimensional medium (nanoguide), where enhanced emitter-photon coupling leads to efficient multiple scattering of photons. We show that the spectrum of the transmitted light undergoes normal-mode splitting even though no external cavity resonance is employed. By considering densities much higher than those encountered in cold atom experiments, we study the influence of the near-field dipole coupling and disorder on the resulting complex super-radiant and subradiant polaritonic states. In particular, we provide evidence for the longitudinal localization of light in a one-dimensional open system and provide a polaritonic phase diagram. Our results motivate a number of experiments, where new coherent superposition states of light and matter can be realized in the solid state.
Spectroscopy and microscopy of single molecules in nanoscopic channels:
spectral behavior vs. confinement depth
Benjamin Gmeiner,
Andreas Maser,
Tobias Utikal,
Stephan Goetzinger,
Vahid Sandoghdar
Physical Chemistry Chemical Physics
18
19588-19594
(2016)
| Journal
We perform high-resolution spectroscopy and localization microscopy to study single dye molecules confined to nanoscopic dimensions in one direction. We provide the fabrication details of our nanoscopic glass channels and the procedure for filling them with organic matrices. Optical data on hundreds of molecules in different channel depths show a clear trend from narrow stable lines in deep channels to broader linewidths in ultrathin matrices. In addition, we observe a steady blue shift of the center of the inhomogeneous band as the channels become thinner. Furthermore, we use super-resolution localization microscopy to correlate the positions and orientations of the individual dye molecules with the lateral landscape of the organic matrix, including cracks and strain-induced dislocations. Our results and methodology are useful for a number of studies in various fields such as physical chemistry, solid-state spectroscopy, and quantum nano-optics.
Visualization of lipids and proteins at high spatial and temporal resolution via interferometric scattering (iSCAT) microscopy
Susann Spindler,
Jens Ehrig,
Katharina Koenig,
Tristan Nowak,
Marek Piliarik,
Hannah E. Stein,
Richard W. Taylor,
Elisabeth Garanger,
Sebastien Lecommandoux,
Isabel D. Alves,
Vahid Sandoghdar
Microscopy based on the interferometric detection of light scattered from nanoparticles (iSCAT) was introduced in our laboratory more than a decade ago. In this work, we present various capabilities of iSCAT for biological studies by discussing a selection of our recent results. In particular, we show tracking of lipid molecules in supported lipid bilayers (SLBs), tracking of gold nanoparticles with diameters as small as 5 nm and at frame rates close to 1 MHz, 3D tracking of Tat peptide-coated nanoparticles on giant unilamellar vesicles (GUVs), imaging the formation of lipid bilayers, sensing single unlabelled proteins and tracking their motion under electric fields, as well as challenges of studying live cell membranes. These studies set the ground for future quantitative research on dynamic biophysical processes at the nanometer scale.
SPECTRAL ASYMPTOTICS IN ONE-DIMENSIONAL PERIODIC LATTICES WITH GEOMETRIC
INTERACTION
Nanoantennas are well-known for their effective role in fluorescence enhancement, both in excitation and emission. Enhancements of 3-4 orders of magnitude have been reported. Yet in practice, the photon emission is limited by saturation due to the time that a molecule spends in singlet and especially triplet excited states. The maximal photon stream restricts the attainable enhancement. Furthermore, the total number of photons emitted is limited by photobleaching. The limited brightness and observation time are a drawback for applications, especially in biology. Here we challenge this photon limit, showing that nanoantennas can actually increase both saturation intensity and photostability. So far, this limit-shifting role of nanoantennas has hardly been explored. Specifically, we demonstrate that single light-harvesting complexes, under saturating excitation conditions, show over a 50-fold antenna-enhanced photon emission stream, with 10-fold more total photons, up to 108 detected photons, before photobleaching. This work shows yet another facet of the great potential of nanoantennas in the world of single-molecule biology.
Visualization and ligand-induced modulation of dopamine receptor
dimerization at the single molecule level
Alina Tabor,
Siegfried Weisenburger,
Ashutosh Banerjee,
Nirupam Purkayastha,
Jonas M. Kaindl,
Harald Huebner,
Luxi Wei,
Teja W. Groemer,
Johannes Kornhuber,
Nuska Tschammer,
Nigel J. M. Birdsall,
Gregory I. Mashanov,
Vahid Sandoghdar,
Peter Gmeiner
G protein–coupled receptors (GPCRs), including dopamine receptors, represent a group of important pharmacological targets. An increased formation of dopamine receptor D2 homodimers has been suggested to be associated with the pathophysiology of schizophrenia. Selective labeling and ligand-induced modulation of dimerization may therefore allow the investigation of the pathophysiological role of these dimers. Using TIRF microscopy at the single molecule level, transient formation of homodimers of dopamine receptors in the membrane of stably transfected CHO cells has been observed. The equilibrium between dimers and monomers was modulated by the binding of ligands; whereas antagonists showed a ratio that was identical to that of unliganded receptors, agonist-bound D2 receptor-ligand complexes resulted in an increase in dimerization. Addition of bivalent D2 receptor ligands also resulted in a large increase in D2 receptor dimers. A physical interaction between the protomers was confirmed using high resolution cryogenic localization microscopy, with ca. 9 nm between the centers of mass.
Partially Hydrated Electrons at the Air/Water Interface Observed by
UV-Excited Time-Resolved Heterodyne-Detected Vibrational Sum Frequency
Generation Spectroscopy
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
138
(24)
7551-7557
(2016)
| Journal
Hydrated electrons are the most fundamental anion species, consisting only of electrons and surrounding water molecules. Although hydrated electrons have been extensively studied in the bulk aqueous solutions, even their existence is still controversial at the water surface. Here, we report the observation and characterization of hydrated electrons at the air/water interface using new time-resolved interface-selective nonlinear vibrational spectroscopy. With the generation of electrons at the air/water interface by ultraviolet photoirradiation, we observed the appearance of a strong transient band in the OH stretch region by heterodyne-detected vibrational sum-frequency generation. Through the comparison with the time-resolved spectra at the air/indole solution interface, the transient band was assigned to the vibration of water molecules that solvate electrons at the interface. The analysis of the frequency and decay of the observed transient band indicated that the electrons are only partially hydrated at the water surface, and that they escape into the bulk within 100 ps.
Optically assisted trapping with high-permittivity dielectric rings:
Towards optical aerosol filtration
Rasoul Alaee,
Muamer Kadic,
Carsten Rockstuhl,
Ali Passian
Visualization of lipids and proteins at high spatial and temporal
resolution via interferometric scattering (iSCAT) microscopy
Susann Spindler,
Jens Ehrig,
Katharina König,
Tristan Nowak,
Marek Piliarik,
Hannah E. Stein,
Richard W. Taylor,
Elisabeth Garanger,
Sebastien Lecommandoux,
Isabel D. Alves,
Vahid Sandoghdar
Journal of Physics D - Applied Physics
49
274002
(2016)
| Journal
Microscopy based on the interferometric detection of light scattered from nanoparticles (iSCAT) was introduced in our laboratory more than a decade ago. In this work, we present various capabilities of iSCAT for biological studies by discussing a selection of our recent results. In particular, we show tracking of lipid molecules in supported lipid bilayers (SLBs), tracking of gold nanoparticles with diameters as small as 5 nm and at frame rates close to 1 MHz, 3D tracking of Tat peptide-coated nanoparticles on giant unilamellar vesicles (GUVs), imaging the formation of lipid bilayers, sensing single unlabelled proteins and tracking their motion under electric fields, as well as challenges of studying live cell membranes. These studies set the ground for future quantitative research on dynamic biophysical processes at the nanometer scale.
Optical force and torque on dipolar dual chiral particles
A. Rahimzadegan,
M. Fruhnert,
R. Alaee,
I. Fernandez-Corbaton,
C. Rockstuhl
The pioneering experiments in linear spectroscopy were performed using flames in the 1800s, but nonlinear optical measurements had to wait until lasers became available in the twentieth century. Because the nonlinear cross-section of materials is very small(1,2), macroscopic bulk samples and pulsed lasers are usually used. Numerous efforts have explored coherent nonlinear signal generation from individual nanoparticles(3-5) or small atomic ensembles(6-8) with millions of atoms. Experiments on a single semiconductor quantum dot have also been reported, albeit with a very small yield(9). Here, we report the coherent nonlinear spectroscopy of a single molecule under continuous-wave single-pass illumination and the switching of a laser beam by on the order of ten pump photons. The sharp molecular transitions and efficient photon-molecule coupling at a tight focus(10) allow for optical switching with less than a handful of pump photons and are thus promising for applications in quantum engineering(11).
Contact
Nano-Optics Division Prof. Vahid Sandoghdar
Max Planck Institute for the Science of Light Staudtstr. 2 91058 Erlangen, Germany
