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- ItemDNAzymes as Catalysts for l-Tyrosine and Amyloid β Oxidation(Washington, DC : ACS Publications, 2020) Köhler, Tony; Patsis, Panagiotis A.; Hahn, Dominik; Ruland, André; Naas, Carolin; Müller, Martin; Thiele, JulianSingle-stranded deoxyribonucleic acids have an enormous potential for catalysis by applying tailored sequences of nucleotides for individual reaction conditions and substrates. If such a sequence is guanine-rich, it may arrange into a three-dimensional structure called G-quadruplex and give rise to a catalytically active DNA molecule, a DNAzyme, upon addition of hemin. Here, we present a DNAzyme-mediated reaction, which is the oxidation of l-tyrosine toward dityrosine by hydrogen peroxide. With an optimal stoichiometry between DNA and hemin of 1:10, we report an activity of 101.2 ± 3.5 μUnits (μU) of the artificial DNAzyme Dz-00 compared to 33.0 ± 1.8 μU of free hemin. Exemplarily, DNAzymes may take part in neurodegeneration caused by amyloid beta (Aβ) aggregation due to l-tyrosine oxidation. We show that the natural, human genome-derived DNAzyme In1-sp is able to oxidize Aβ peptides with a 4.6% higher yield and a 33.3% higher velocity of the reaction compared to free hemin. As the artificial DNAzyme Dz-00 is even able to catalyze Aβ peptide oxidation with a 64.2% higher yield and 337.1% higher velocity, an in-depth screening of human genome-derived DNAzymes may identify further candidates with similarly high catalytic activity in Aβ peptide oxidation.
- ItemAutofluorescence guided welding of heart tissue by laser pulse bursts at 1550 nm(Washington, DC : Optica, 2020) Litvinova, Karina; Chernysheva, Maria; Stegemann, Berthold; Leyva, FranciscoWound healing and other surgical technologies traditionally solved by suturing and stapling have recently been enhanced by the application of laser tissue welding. The usage of high energy laser radiation to anastomose tissues eliminates a foreign body reaction, reduces scar formation, and allows for the creation of watertight closure. In the current work, we show that an ultrafast pulsed fibre laser beam with 183 µJ·cm−2 energy fluence at 1550 nm provides successful welding of dissected chicken heart walls with the tensile strength of 1.03±0.12 kg·cm−2 equal to that of native tissue. The welding process was monitored employing fluorescence spectroscopy that detects the biochemical composition of tissues. We believe that fluorescence spectroscopy guided laser tissue welding is a promising approach for decreasing wound healing times and the avoiding risks of postoperative complications.
- ItemMetallofullerene photoswitches driven by photoinduced fullerene-to-metal electron transfer(Cambridge : RSC, 2021) Zalibera, Michal; Ziegs, Frank; Schiemenz, Sandra; Dubrovin, Vasilii; Lubitz, Wolfgang; Savitsky, Anton; Deng, Shihu H.M.; Wang, Xue-Bin; Advoshenko, Stanislav M.; Popov, Alexey A.We report on the discovery and detailed exploration of the unconventional photo-switching mechanism in metallofullerenes, in which the energy of the photon absorbed by the carbon cage π-system is transformed to mechanical motion of the endohedral cluster accompanied by accumulation of spin density on the metal atoms. Comprehensive photophysical and electron paramagnetic resonance (EPR) studies augmented by theoretical modelling are performed to address the phenomenon of the light-induced photo-switching and triplet state spin dynamics in a series of YxSc3−xN@C80 (x = 0–3) nitride clusterfullerenes. Variable temperature and time-resolved photoluminescence studies revealed a strong dependence of their photophysical properties on the number of Sc atoms in the cluster. All molecules in the series exhibit temperature-dependent luminescence assigned to the near-infrared thermally-activated delayed fluorescence (TADF) and phosphorescence. The emission wavelengths and Stokes shift increase systematically with the number of Sc atoms in the endohedral cluster, whereas the triplet state lifetime and S1–T1 gap decrease in this row. For Sc3N@C80, we also applied photoelectron spectroscopy to obtain the triplet state energy as well as the electron affinity. Spin distribution and dynamics in the triplet states are then studied by light-induced pulsed EPR and ENDOR spectroscopies. The spin–lattice relaxation times and triplet state lifetimes are determined from the temporal evolution of the electron spin echo after the laser pulse. Well resolved ENDOR spectra of triplets with a rich structure caused by the hyperfine and quadrupolar interactions with 14N, 45Sc, and 89Y nuclear spins are obtained. The systematic increase of the metal contribution to the triplet spin density from Y3N to Sc3N found in the ENDOR study points to a substantial fullerene-to-metal charge transfer in the excited state. These experimental results are rationalized with the help of ground-state and time-dependent DFT calculations, which revealed a substantial variation of the endohedral cluster position in the photoexcited states driven by the predisposition of Sc atoms to maximize their spin population.
- ItemPropagation-assisted generation of intense few-femtosecond high-harmonic pulses(Bristol : IOP Publishing, 2020) Major, B.; Kretschmar, M.; Ghafur, O.; Hoffmann, A.; Kovács, K.; Varjú, K.; Senfftleben, B.; Tümmler, J.; Will, I.; Nagy, T.; Rupp, D.; Vrakking, M.J.J.; Tosa, V.; Schütte, B.The ongoing development of intense high-harmonic generation (HHG) sources has recently enabled highly non-linear ionization of atoms by the absorption of at least 10 extreme-ultraviolet (XUV) photons within a single atom (Senfftleben et al, arXiv:1911.01375). Here we investigate how the generation of these very intense HHG pulses in our 18-m-long beamline is aided by the reshaping of the fundamental, few-cycle, near-infrared (NIR) driving laser within a 30-cm-long HHG Xe medium. Using an incident NIR intensity that is higher than what is required for phase-matched HHG, signatures of reshaping are found by measuring the NIR blueshift and the fluorescence from the HHG medium along the propagation axis. These results are well reproduced by numerical calculations that show temporal compression of the NIR pulses in the HHG medium. The simulations predict that after refocusing an XUV beam waist radius of 320 nm and a clean attosecond pulse train can be obtained in the focal plane, with an estimated XUV peak intensity of 9 × 1015 W cm-2. Our results show that XUV intensities that were previously only available at large-scale facilities can now be obtained using moderately powerful table-top light sources. © 2020 The Author(s). Published by IOP Publishing Ltd
- ItemSuper-resolution RESOLFT microscopy of lipid bilayers using a fluorophore-switch dyad(Cambridge : RSC, 2020) Frawley, Andrew T.; Wycisk, Virginia; Xiong, Yaoyao; Galiani, Silvia; Sezgin, Erdinc; Urbančič, Iztok; Vargas Jentzsch, Andreas; Leslie, Kathryn G.; Eggeling, Christian; Anderson, Harry L.Dyads consisting of a photochromic switch covalently linked to a fluorescent dye allow the emission from the dye to be controlled by reversible photoisomerization of the switch; one form of the switch quenches fluorescence by accepting energy from the dye. Here we investigate the use of dyads of this type for super-resolution imaging of lipid bilayers. Giant unilamellar vesicles stained with the dyads were imaged with about a two-fold resolution-enhancement compared with conventional confocal microscopy. This was achieved by exciting the fluorophore at 594 nm, using a switch activated by violet and red light (405/640 nm). This journal is © The Royal Society of Chemistry.
- ItemDirect supercritical angle localization microscopy for nanometer 3D superresolution([London] : Nature Publishing Group UK, 2021) Dasgupta, Anindita; Deschamps, Joran; Matti, Ulf; Hübner, Uwe; Becker, Jan; Strauss, Sebastian; Jungmann, Ralf; Heintzmann, Rainer; Ries, Jonas3D single molecule localization microscopy (SMLM) is an emerging superresolution method for structural cell biology, as it allows probing precise positions of proteins in cellular structures. In supercritical angle localization microscopy (SALM), z-positions of single fluorophores are extracted from the intensity of supercritical angle fluorescence, which strongly depends on their distance to the coverslip. Here, we realize the full potential of SALM and improve its z-resolution by more than four-fold compared to the state-of-the-art by directly splitting supercritical and undercritical emission, using an ultra-high NA objective, and applying fitting routines to extract precise intensities of single emitters. We demonstrate nanometer isotropic localization precision on DNA origami structures, and on clathrin coated vesicles and microtubules in cells, illustrating the potential of SALM for cell biology.
- ItemEvidence of the dominant production mechanism of ammonia in a hydrogen plasma with parts per million of nitrogen([Melville, NY] : American Institute of Physics, 2021) Ellis, J.; Köpp, D.; Lang, N.; van Helden, J. H.Absolute ground state atomic hydrogen densities were measured, by the utilization of two-photon absorption laser induced fluorescence, in a low-pressure electron cyclotron resonance plasma as a function of nitrogen admixtures - 0 to 5000 ppm. At nitrogen admixtures of 1500 ppm and higher, the spectral distribution of the fluorescence changes from a single Gaussian to a double Gaussian distribution; this is due to a separate, nascent contribution arising from the photolysis of an ammonia molecule. At nitrogen admixtures of 5000 ppm, the nascent contribution becomes the dominant contribution at all investigated pressures. Thermal loading experiments were conducted by heating the chamber walls to different temperatures; this showed a decrease in the nascent contributions with increasing temperature. This is explained by considering how the temperature influences recombination coefficients, and from which, it can be stated that the Langmuir-Hinshelwood recombination mechanism is dominant over the Eley-Rideal mechanism.
- ItemOn-chip fluorescence detection using photonic bandgap guiding optofluidic hollow-core light cage(Melville, NY : AIP Publishing, 2022) Kim, Jisoo; Jang, Bumjoon; Wieduwilt, Torsten; Warren-Smith, Stephen C.; Bürger, Johannes; Maier, Stefan A.; Schmidt, Markus A.The on-chip detection of fluorescent light is essential for many bioanalytical and life-science related applications. Here, the optofluidic light cage consisting of a sparse array of micrometer encircling a hollow core represents an innovative concept, particularly for on-chip waveguide-based spectroscopy. In the present work, we demonstrate the potential of the optofluidic light cage concept in the context of integrated on-chip fluorescence spectroscopy. Specifically, we show that fluorescent light from a dye-doped aqueous solution generated in the core of a nanoprinted dual-ring light cage can be efficiently captured and guided to the waveguide ports. Notably, the fluorescence collection occurs predominantly in the fundamental mode, a property that distinguishes it from evanescent field-based waveguide detection schemes that favor collection in higher-order modes. Through exploiting the flexibility of waveguide design and 3D nanoprinting, both excitation and emission have been localized in the high transmission domains of the fundamental core mode. Fast diffusion, detection limits comparable to bulk measurements, and the potential of this approach in terms of device integration were demonstrated. Together with previous results on absorption spectroscopy, the achievements presented here suggest that the optofluidic light cage concept defines a novel photonic platform for integrated on-chip spectroscopic devices and real-time sensors compatible with both the fiber circuitry and microfluidics. Applications in areas such as bioanalytics and environmental sciences are conceivable, while more sophisticated applications such as nanoparticle tracking analysis and integrated Raman spectroscopy could be envisioned,
- ItemComputer vision vs. spectrofluorometer-assisted detection of common nitro-explosive components with bola-type PAH-based chemosensors(London : RSC Publishing, 2021) Kovalev, Igor S.; Sadieva, Leila K.; Taniya, Olga S.; Yurk, Victoria M.; Minin, Artem S.; Santra, Sougata; Zyryanov, Grigory V.; Charushin, Valery N.; Chupakhin, Oleg N.; Tsurkan, Mikhail V.Computer vision (CV) algorithms are widely utilized in imaging processing for medical and personal electronics applications. In sensorics CV can provide a great potential to quantitate chemosensors' signals. Here we wish to describe a method for the CV-assisted spectrofluorometer-free detection of common nitro-explosive components, e.g. 2,4-dinitrotoluene (DNT) and 2,4,6-trinitrotoluene (TNT), by using polyaromatic hydrocarbon (PAH, PAH = 1-pyrenyl or 9-anthracenyl) – based bola-type chemosensors. The PAH components of these chemical bolas are able to form stable, bright emissive in a visual wavelength region excimers, which allows their use as extended matrices of the RGB colors after imaging and digital processing. In non-polar solvents, the excimers have poor chemosensing properties, while in aqueous solutions, due to the possible micellar formation, these excimers provide “turn-off” fluorescence detection of DNT and TNT in the sub-nanomolar concentrations. A combination of these PAH-based fluorescent chemosensors with the proposed CV-assisted algorithm offers a fast and convenient approach for on-site, real-time, multi-thread analyte detection without the use of fluorometers. Although we focus on the analysis of nitro-explosives, the presented method is a conceptual work describing a general use of CV for quantitative fluorescence detection of various analytes as a simpler alternative to spectrofluorometer-assisted methods.