Recent Submissions

  • Journal Article

    Synthesis of Gb3 Glycosphingolipids with Labeled Head Groups: Distribution in Phase-Separated Giant Unilamellar Vesicles 

    Sibold, Jeremias; Kettelhoit, Katharina; Vuong, Loan; Liu, Fangyuan; Werz, Daniel B.; Steinem, Claudia
    Angewandte Chemie International Edition
    The receptor lipid Gb3 is responsible for the specific internalization of Shiga toxin (STx) into cells. The head group of Gb3 defines the specificity of STx binding, and the backbone with different fatty acids is expected to influence its localization within membranes impacting membrane organization and protein internalization. To investigate this influence, a set of Gb3 glycosphingolipids labeled with a BODIPY fluorophore attached to the head group was synthesized. C24 fatty acids, saturated, unsaturated, α-hydroxylated derivatives, and a combination thereof, were attached to the sphingosine backbone. The synthetic Gb3 glycosphingolipids were reconstituted into coexisting liquid-ordered (lo )/liquid-disordered (ld ) giant unilamellar vesicles (GUVs), and STx binding was verified by fluorescence microscopy. Gb3 with the C24:0 fatty acid partitioned mostly in the lo phase, while the unsaturated C24:1 fatty acid distributes more into the ld phase. The α-hydroxylation does not influence its partitioning.
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  • Journal Article

    Organoaluminum Compounds as Catalysts for Monohydroboration of Carbodiimides 

    Shen, Qiumiao; Ma, Xiaoli; Li, Wenling; Liu, Wenqing; Ding, Yi; Yang, Zhi; Roesky, Herbert W.
    Chemistry – A European Journal 2019; 25(51) p.11918-11923
    he effectivecatalytic activity of organoaluminumcompoundsfor the monohydroboration of carbodiimideshas beendemonstrated. Twoaluminumcomplexes,2and3,weresynthesizedandcharacterized.Theefficientcatalyticperformances of fouraluminum hydridecomplexes L1AlH2(L1=HC(CMeNAr)2,Ar=2,6-Et2C6H3;1), L2AlH2(NMe3)(L2=o-C6H4F(CH=N-Ar),Ar=2,6-Et2C6H3;2), L3AlH(L3=2,6-bis(1-methylethyl)-N-(2-pyridinylmethylene)phenylamine;3), andL4AlH(NMe3)(L4=o-C6H4(N-Dipp)(CH=N-Dipp),Dipp=2,6-iPr2C6H3;4), andan aluminum alkylcomplex L1AlMe2(5)wereusedfor the monohydroboration of carbodiimidesin-vestigatedundersolvent-free andmildconditions. Com-pounds1–3and5can produce monohydroboratedN-boryl-formamidine, whereas4can affordtheC-borylformamidineproduct. Asuggested mechanismof this reactionwas ex-plored, andthe aluminumformamidinate compound6wascharacterized by single-crystal X-ray,also astoichiometricre-actionwas investigated.
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  • Journal Article

    Quantitation of eumelanin and pheomelanin markers in diverse biological samples by HPLC-UV-MS following solid-phase extraction 

    Affenzeller, Susanne; Frauendorf, Holm; Licha, Tobias; Jackson, Daniel J.; Wolkenstein, Klaus
    PLOS ONE 2019; 14(10): Art. e0223552
    Eumelanin and pheomelanin are well known and common pigments found in nature. However, their complex polymer structure and high thermostability complicate their direct chemical identification. A widely used analytical method is indirect determination using HPLC with UV detection of both types of melanin by their most abundant oxidation products: pyrrole-2,3-dicarboxylic acid (PDCA), pyrrole-2,3,5-tricarboxylic acid (PTCA), thiazole-4,5-dicarboxylic acid (TDCA), and thiazole-2,4,5-tricarboxylic acid (TTCA). An increasing interest in pigmentation in biological research led us to develop a highly sensitive and selective method to identify and quantify these melanin markers in diverse biological samples with complex matrices. By introducing solid-phase extraction (SPE, reversed-phase) following alkaline oxidation we could significantly decrease background signals while maintaining recoveries greater than 70%. Our HPLC-UV-MS method allows for confident peak identification via exact mass information in corresponding UV signals used for quantitation. In addition to synthetic melanin and Sepia officinalis ink as reference compounds eumelanin markers were detected in brown human hair and a brown bivalve shell (Mytilus edulis). Brown feathers from the common chicken (Gallus g. domesticus) yielded all four eumelanin and pheomelanin markers. The present method can be easily adapted for a wide range of future studies on biological samples with unknown melanin content.
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  • Journal Article

    Charge Storage Properties of Nanostructured Poly (3,4–ethylenedioxythiophene) Electrodes Revealed by Advanced Electrogravimetry 

    Lé, Tao; Aradilla, David; Bidan, Gérard; Billon, Florence; Debiemme-Chouvy, Catherine; Perrot, Hubert; Sel, Ozlem
    Nanomaterials 2019; 9(7): Art. 962
    PEDOT nanowires (NWs) directly grown on the conducting electrode of quartz resonators enable an advanced electrogravimetric analysis of their charge storage behavior. Electrochemical quartz crystal microbalance (EQCM) and its coupling with electrochemical impedance spectroscopy (ac-electrogravimetry or AC-EG) were used complementarily and reveal that TBA+, BF4- and ACN participate in the charge compensation process with different kinetics and quantity. BF4- anions were dominant in terms of concentration over TBA+ cations and the anion transfer results in the exclusion of the solvent molecules. TBA+ concentration variation in the electrode was small compared to that of the BF4- counterpart. However, Mw of TBA+ is much higher than BF4- (242.3 vs. 86.6 g·mol-1). Thus, TBA+ cations' gravimetric contribution to the EQCM response was more significant than that of BF4-. Additional contribution of ACN with an opposite flux direction compared with BF4-, led to a net mass gain/lost during a negative/positive potential scan, masking partially the anion response. Such subtleties of the interfacial ion transfer processes were disentangled due to the complementarity of the EQCM and AC-EG methodologies, which were applied here for the characterization of electrochemical processes at the PEDOT NW electrode/organic electrolyte interface.
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  • Journal Article

    Late-stage peptide C–H alkylation for bioorthogonal C–H activation featuring solid phase peptide synthesis 

    Schischko, Alexandra; Kaplaneris, Nikolaos; Rogge, Torben; Sirvinskaite, Giedre; Son, Jongwoo; Ackermann, Lutz
    Nature Communications 2019; 10(1): Art. 3553
    Methods for the late-stage diversification of structurally complex peptides hold enormous potential for advances in drug discovery, agrochemistry and pharmaceutical industries. While C-H arylations emerged for peptide modifications, they are largely limited to highly reactive, expensive and/or toxic reagents, such as silver(I) salts, in superstoichiometric quantities. In sharp contrast, we herein establish the ruthenium(II)-catalyzed C-H alkylation on structurally complex peptides. The additive-free ruthenium(II)carboxylate C-H activation manifold is characterized by ample substrate scope, racemization-free conditions and the chemo-selective tolerance of otherwise reactive functional groups, such as electrophilic ketone, bromo, ester, amide and nitro substituents. Mechanistic studies by experiment and computation feature an acid-enabled C-H ruthenation, along with a notable protodemetalation step. The transformative peptide C-H activation regime sets the stage for peptide ligation in solution and proves viable in a bioorthogonal fashion for C-H alkylations on user-friendly supports by means of solid phase peptide syntheses.
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  • Journal Article

    Blue and Long-Wave Ultraviolet Light Induce in vitro Neutrophil Extracellular Trap (NET) Formation 

    Neubert, Elsa; Bach, Katharina Marie; Busse, Julia; Bogeski, Ivan; Schön, Michael P.; Kruss, Sebastian; Erpenbeck, Luise
    Frontiers in Immunology 2019; 10: Art. 2428
    Neutrophil Extracellular Traps (NETs) are produced by neutrophilic granulocytes and consist of decondensed chromatin decorated with antimicrobial peptides. They defend the organism against intruders and are released upon various stimuli including pathogens, mediators of inflammation, or chemical triggers. NET formation is also involved in inflammatory, cardiovascular, malignant diseases, and autoimmune disorders like rheumatoid arthritis, psoriasis, or systemic lupus erythematosus (SLE). In many autoimmune diseases like SLE or dermatomyositis, light of the ultraviolet-visible (UV-VIS) spectrum is well-known to trigger and aggravate disease severity. However, the underlying connection between NET formation, light exposure, and disease exacerbation remains elusive. We studied the effect of UVA (375 nm), blue (470 nm) and green (565 nm) light on NETosis in human neutrophils ex vivo. Our results show a dose- and wavelength-dependent induction of NETosis. Light-induced NETosis depended on the generation of extracellular reactive oxygen species (ROS) induced by riboflavin excitation and its subsequent reaction with tryptophan. The light-induced NETosis required both neutrophil elastase (NE) as well as myeloperoxidase (MPO) activation and induced histone citrullination. These findings suggest that NET formation as a response to light could be the hitherto missing link between elevated susceptibility to NET formation in autoimmune patients and photosensitivity for example in SLE and dermatomyositis patients. This novel connection could provide a clue for a deeper understanding of light-sensitive diseases in general and for the development of new pharmacological strategies to avoid disease exacerbation upon light exposure.
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  • Journal Article

    A critical comparison of neural network potentials for molecular reaction dynamics with exact permutation symmetry 

    Li, Jun; Song, Kaisheng; Behler, Jörg
    Physical Chemistry Chemical Physics 2019; 21(19) p.9672-9682
    The availability of accurate full-dimensional potential energy surfaces (PESs) is a mandatory condition for efficient computer simulations of molecular systems. Much effort has been devoted to developing reliable PESs with physically sound properties, such as the invariance of the energy with respect to the permutation of chemically identical atoms. In this work, we compare the performance of four neural network (NN)-based approaches with a rigorous permutation symmetry for fitting five typical reaction systems: OH + CO, H + H2S, H + NH3, H + CH4 and OH + CH4. The methods can be grouped into two categories, invariant polynomial based NNs and high-dimensional NN potentials (HD-NNPs). For the invariant polynomial based NNs, three types of polynomials, permutation invariant polynomials (PIPs), non-redundant PIPs (NRPIPs) and fundamental invariants (FIs), are used in the input layer of the NN. In HD-NNPs, the total energy is the sum of atomic contributions, each of which is given by an individual atomic NN with input vectors consisting of sets of atom-centered symmetry functions. Our results show that all methods exhibit a similar level of accuracy for the energies with respect to ab initio data obtained at the explicitly correlated coupled cluster level of theory (CCSD(T)-F12a). The HD-NNP method allows study of systems with larger numbers of atoms, making it more generally applicable than invariant polynomial based approaches, which in turn are computationally more efficient for smaller systems. To illustrate the applicability of the obtained potentials, quasi-classical trajectory calculations have been performed for the OH + CH4 → H2O + CH3 reaction to reveal its complicated mode specificity.
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  • Journal Article

    Effect of Adhesion and Substrate Elasticity on Neutrophil Extracellular Trap Formation 

    Erpenbeck, Luise; Gruhn, Antonia Luise; Kudryasheva, Galina; Günay, Gökhan; Meyer, Daniel; Busse, Julia; Neubert, Elsa; Schön, Michael P.; Rehfeldt, Florian; Kruss, Sebastian
    Frontiers in Immunology 2019; 10: Art. 2320
    Neutrophils are the most abundant type of white blood cells. Upon stimulation, they are able to decondense and release their chromatin as neutrophil extracellular traps (NETs). This process (NETosis) is part of immune defense mechanisms but also plays an important role in many chronic and inflammatory diseases such as atherosclerosis, rheumatoid arthritis, diabetes, and cancer. For this reason,much effort has been invested into understanding biochemical signaling pathways in NETosis. However, the impact of the mechanical micro-environment and adhesion on NETosis is not well-understood. Here, we studied how adhesion and especially substrate elasticity affect NETosis. We employed polyacrylamide (PAA) gels with distinctly defined elasticities (Young’s modulus E) within the physiologically relevant range from 1 to 128 kPa and coated the gels with integrin ligands (collagen I, fibrinogen). Neutrophils were cultured on these substrates and stimulated with potent inducers of NETosis: phorbol 12-myristate 13-acetate (PMA) and lipopolysaccharide (LPS). Interestingly, PMA-induced NETosis was neither affected by substrate elasticity nor by different integrin ligands. In contrast, for LPS stimulation, NETosis rates increased with increasing substrate elasticity (E > 20 kPa). LPS-induced NETosis increased with increasing cell contact area, while PMA-induced NETosis did not require adhesion at all. Furthermore, inhibition of phosphatidylinositide 3 kinase (PI3K), which is involved in adhesion signaling, completely abolished LPS-induced NETosis but only slightly decreased PMA-induced NETosis. In summary, we show that LPS-induced NETosis depends on adhesion and substrate elasticity while PMA-induced NETosis is completely independent of adhesion.
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  • Journal Article

    A critical comparison of neural network potentials for molecular reaction dynamics with exact permutation symmetry 

    Li, Jun; Song, Kaisheng; Behler, Jörg
    Physical Chemistry Chemical Physics 2019; 21(19) p.9672-9682
    The availability of accurate full-dimensional potential energy surfaces (PESs) is a mandatory condition for efficient computer simulations of molecular systems. Much effort has been devoted to developing reliable PESs with physically sound properties, such as the invariance of the energy with respect to the permutation of chemically identical atoms. In this work, we compare the performance of four neural network (NN)-based approaches with a rigorous permutation symmetry for fitting five typical reaction systems: OH + CO, H + H2S, H + NH3, H + CH4 and OH + CH4. The methods can be grouped into two categories, invariant polynomial based NNs and high-dimensional NN potentials (HD-NNPs). For the invariant polynomial based NNs, three types of polynomials, permutation invariant polynomials (PIPs), non-redundant PIPs (NRPIPs) and fundamental invariants (FIs), are used in the input layer of the NN. In HD-NNPs, the total energy is the sum of atomic contributions, each of which is given by an individual atomic NN with input vectors consisting of sets of atom-centered symmetry functions. Our results show that all methods exhibit a similar level of accuracy for the energies with respect to ab initio data obtained at the explicitly correlated coupled cluster level of theory (CCSD(T)-F12a). The HD-NNP method allows study of systems with larger numbers of atoms, making it more generally applicable than invariant polynomial based approaches, which in turn are computationally more efficient for smaller systems. To illustrate the applicability of the obtained potentials, quasi-classical trajectory calculations have been performed for the OH + CH4 → H2O + CH3 reaction to reveal its complicated mode specificity.
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  • Journal Article

    PDB2INS: bridging the gap between small-molecule and macromolecular refinement 

    Lübben, Anna V.; Sheldrick, George M.
    Journal of Applied Crystallography 2019; 52(3) p.669-673
    The open-source Python program PDB2INS is designed to prepare a .ins file for refinement with SHELXL [Sheldrick (2015). Acta Cryst. C71, 3-8], taking atom coordinates and other information from a Protein Data Bank (PDB)-format file. If PDB2INS is provided with a four-character PDB code, both the PDB file and the accompanying mmCIF-format reflection data file (if available) are accessed via the internet from the PDB public archive [Read et al. (2011). Structure, 19, 1395-1412] or optionally from the PDB_REDO server [Joosten, Long, Murshudov & Perrakis (2014). IUCrJ, 1, 213-220]. The SHELX-format .ins (refinement instructions and atomic coordinates) and .hkl (reflection data) files can then be generated without further user intervention, appropriate restraints etc. being added automatically. PDB2INS was tested on the 23 974 X-ray structures deposited in the PDB between 2008 and 2018 that included reflection data to 1.7 Å or better resolution in a recognizable format. After creating the two input files for SHELXL without user intervention, ten cycles of conjugate-gradient least-squares refinement were performed. For 96% of these structures PDB2INS and SHELXL completed successfully without error messages.
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  • Journal Article

    Fluorinated nanobodies for targeted molecular imaging of biological samples using nanoscale secondary ion mass spectrometry 

    Kabatas, Selda; Agüi-Gonzalez, Paola; Hinrichs, Rena; Jähne, Sebastian; Opazo, Felipe; Diederichsen, Ulf; Rizzoli, Silvio O.; Phan, Nhu T. N.
    Journal of Analytical Atomic Spectrometry 2019; 34(6) p.1083-1087
    Molecular imaging of targeted large biomolecules has been restricted in SIMS due to the limited number of probes containing SIMS-detectable isotopes. We introduce here new 19F-containing molecules that can be conjugated in a site-specific manner to nanobodies able to recognize fluorescent proteins (FPs) or mouse immunoglobulins (Igs). In this work, we demonstrate that it is possible to use the 19F-nanobodies to reveal the location of several cellular proteins previously tagged with FPs or Igs. This enables specific bio-imaging in SIMS for a vast repertoire of biomolecules, offering new opportunities to study specific structural and functional molecular interactions in biological specimens.
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  • Journal Article

    Shock wave and modelling study of the dissociation pathways of (C2F5)3N 

    Cobos, C. J.; Hintzer, K.; Sölter, L.; Tellbach, E.; Thaler, A.; Troe, J.
    Physical Chemistry Chemical Physics 2019; 21(19) p.9785-9792
    The thermal decomposition of perfluorotriethylamine, (C2F5)3N, was investigated in shock waves by monitoring the formation of CF2. Experiments were performed over the temperature range of 1120-1450 K with reactant concentrations between 100 and 1000 ppm of (C2F5)3N in the bath gas Ar and with [Ar] in the range of (0.7-5.5) × 10-5 mol cm-3. The experiments were accompanied by quantum-chemical calculations of the energies of various dissociation paths and by rate calculations, in particular for the dissociation of C2F5via C2F5 → CF3 + CF2. The overall reaction can proceed in different ways, either by a sequence of successive C-N bond ruptures followed by fast C2F5 decompositions, or by a sequence of alternating C-C and C-N bond ruptures. A cross-over between the two pathways can also take place. At temperatures below about 1300 K, yields of less than one CF2 per (C2F5)3N decomposed were observed. On the other hand, at temperatures around 2000 K, when besides the parent molecule, CF3 also dissociates, yields of six CF2 per (C2F5)3N decomposed were measured. The rate-delaying steps of the dissociation mechanism at intermediate temperatures were suggested to be the processes (C2F5)NCF2 → (C2F5)N + CF2 and (CF2)N → N + CF2. The reduction of the CF2 yields at low temperatures was tentatively attributed to a branching of the mechanism at the level of (C2F5)2NCF2, from where the cyclic final product perfluoro-N-methylpyrrolidine, (C4F8)NCF3, is formed which was identified in earlier work from the literature
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  • Journal Article

    5-(Cyano)dibenzothiophenium Triflate: A Sulfur-Based Reagent for Electrophilic Cyanation and Cyanocyclizations 

    Li, Xiangdong; Golz, Christopher; Alcarazo, Manuel
    Angewandte Chemie International Edition 2019; 58(28) p.9496-9500
    The synthesis of 5-(cyano)dibenzothiophenium triflate 9, prepared by activation of dibenzo[b,d]thiophene-5-oxide with Tf2 O and subsequent reaction with TMSCN is reported, and its reactivity as electrophilic cyanation reagent evaluated. The scalable preparation, easy handling and broad substrate scope of the electrophilic cyanation promoted by 9, which includes amines, thiols, silyl enol ethers, alkenes, electron rich (hetero)arenes and polyaromatic hydrocarbons, illustrate the synthetic potential of this reagent. Importantly, Lewis acid activation of the reagent is not required for the transfer process. We additionally report herein biomimetic cyanocyclization cascade reactions, which are not promoted by typical electrophilic cyanation reagents, demonstrating the superior ability of 9 to trigger challenging transformations.
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  • Journal Article

    Isolation of base stabilized fluoroborylene and its radical cation 

    Sarkar, Samir Kumar; Siddiqui, Mujahuddin M.; Kundu, Subrata; Ghosh, Munmun; Kretsch, Johannes; Stollberg, Peter; Herbst-Irmer, Regine; Stalke, Dietmar; Stückl, A. Claudia; Schwederski, Brigitte; et al.
    Kaim, WolfgangGhorai, SagarJemmis, Eluvathingal D.Roesky, Herbert W.
    Dalton Transactions 2019; 48(24) p.8551-8555
    Herein, we report the synthesis and characterization of the metal free low valent fluoroborylene [(Me-cAAC)2BF] (1) stabilized by cyclic (alkyl)(amino) carbene (cAAC). The fluoroborylene 1 is obtained by the reductive defluorination of Me-cAAC:BF3 with 2.0 equivalents of KC8 in the presence of 1.0 equivalent of Me-cAAC. Due to its highly electron rich nature, 1 underwent one-electron oxidation with 1.0 equivalent of lithium tetrakis(pentafluorophenyl)borate [LiB(C6F5)4] to form the radical cation [(Me-cAAC)2BF]˙+[B(C6F5)4]- (2). DFT studies suggested that the lone pair of electrons is localized on the boron atom in 1, which explains its unprecedented reactivity. Both compounds 1 and 2 were characterized by X-ray crystallography. The radical cation 2 was studied by EPR spectroscopy.
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  • Journal Article

    On the Competition Between Electron Autodetachment and Dissociation of Molecular Anions 

    Marowsky, Gerd; Troe, Jürgen; Viggiano, Albert A.
    Journal of The American Society for Mass Spectrometry
    We treat the competition between autodetachment of electrons and unimolecular dissociation of excited molecular anions as a rigid-/loose-activated complex multichannel reaction system. To start, the temperature and pressure dependences under thermal excitation conditions are represented in terms of falloff curves of separated single-channel processes within the framework of unimolecular reaction kinetics. Channel couplings, caused by collisional energy transfer and "rotational channel switching" due to angular momentum effects, are introduced afterward. The importance of angular momentum considerations is stressed in addition to the usual energy treatment. Non-thermal excitation conditions, such as typical for chemical activation and complex-forming bimolecular reactions, are considered as well. The dynamics of excited SF6- anions serves as the principal example. Other anions such as CF3- and POCl3- are also discussed.
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  • Journal Article

    Chirality enriched carbon nanotubes with tunable wrapping via corona phase exchange purification (CPEP) 

    Nißler, Robert; Mann, Florian A.; Preiß, Helen; Selvaggio, Gabriele; Herrmann, Niklas; Kruss, Sebastian
    Nanoscale 2019; 11(23) p.11159-11166
    Single-walled carbon nanotubes (SWCNTs) have unique photophysical properties and serve as building blocks for biosensors, functional materials and devices. For many applications it is crucial to use chirality-pure SWCNTs, which requires sophisticated processes. Purification procedures such as wrapping by certain polymers, phase separation, density gradient centrifugation or gel chromatography have been developed and yield distinct SWCNT species wrapped by a specific polymer or surfactant. However, many applications require a different organic functionalization (corona) around the SWCNTs instead of the one used for the purification process. Here, we present a novel efficient and straightforward process to gain chirality pure SWCNTs with tunable functionalization. Our approach uses polyfluorene (PFO) polymers to enrich certain chiralities but the polymer is removed again and finally exchanged to any desired organic phase. We demonstrate this concept by dispersing SWCNTs in poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(6,6'-{2,2'-bipyridine})] (PFO-BPy), which is known to preferentially solubilize (6,5)-SWCNTs. Then PFO-BPy is removed and recycled, while letting the SWCNTs adsorb/agglomerate on sodium chloride (NaCl) crystals, which act as a toluene-stable but water-soluble filler material. In the last step these purified SWCNTs are redispersed in different polymers, surfactants and ssDNA. This corona phase exchange purification (CPEP) approach was also extended to other PFO variants to enrich and functionalize (7,5)-SWCNTs. CPEP purified and functionalized SWCNTs display monodisperse nIR spectra, which are important for fundamental studies and applications that rely on spectral changes. We show this advantage for SWCNT-based nIR fluorescent sensors for the neurotransmitter dopamine and red-shifted sp3 defect peaks . In summary, CPEP makes use of PFO polymers for chirality enrichment but provides access to chirality enriched SWCNTs functionalized in any desired polymer, surfactant or biopolymer.
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  • Journal Article

    Fluorinated nanobodies for targeted molecular imaging of biological samples using nanoscale secondary ion mass spectrometry 

    Kabatas, Selda; Agüi-Gonzalez, Paola; Hinrichs, Rena; Jähne, Sebastian; Opazo, Felipe; Diederichsen, Ulf; Rizzoli, Silvio O.; Phan, Nhu T. N.
    Journal of Analytical Atomic Spectrometry 2019; 34(6) p.1083-1087
    Molecular imaging of targeted large biomolecules has been restricted in SIMS due to the limited number of probes containing SIMS-detectable isotopes. We introduce here new 19F-containing molecules that can be conjugated in a site-specific manner to nanobodies able to recognize fluorescent proteins (FPs) or mouse immunoglobulins (Igs). In this work, we demonstrate that it is possible to use the 19F-nanobodies to reveal the location of several cellular proteins previously tagged with FPs or Igs. This enables specific bio-imaging in SIMS for a vast repertoire of biomolecules, offering new opportunities to study specific structural and functional molecular interactions in biological specimens.
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  • Journal Article

    Orbital-Dependent Electronic Friction Significantly Affects the Description of Reactive Scattering of N 2 from Ru(0001) 

    Spiering, Paul; Shakouri, Khosrow; Behler, Jörg; Kroes, Geert-Jan; Meyer, Jörg
    The Journal of Physical Chemistry Letters 2019; 10(11) p.2957-2962
    Electron-hole pair (ehp) excitation is thought to substantially affect the dynamics of molecules on metal surfaces, but it is not clear whether this can be better addressed by orbital-dependent friction (ODF) or the local density friction approximation (LDFA). We investigate the effect of ehp excitation on the dissociative chemisorption of N2 on and its inelastic scattering from Ru(0001), which is the benchmark system of highly activated dissociation, with these two different models. ODF is in better agreement with the best experimental estimates for the reaction probabilities than LDFA, yields results for vibrational excitation in better agreement with experiment, but slightly overestimates the translational energy loss during scattering. N2 on Ru(0001) is thus the first system for which the ODF and LDFA approaches are shown to yield substantially different results for easily accessible experimental observables, including reaction probabilities.
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  • Journal Article

    Interconversion of Phosphinyl Radical and Phosphinidene Complexes by Proton Coupled Electron Transfer 

    Abbenseth, Josh; Delony, Daniel; Neben, Marc C.; Würtele, Christian; de Bruin, Bas; Schneider, Sven
    Angewandte Chemie International Edition 2019; 58(19) p.6338-6341
    The isolable complex [Os(PHMes*)H(PNP)] (Mes*=2,4,6-t Bu3 C6 H3 ; PNP=N{CHCHPt Bu2 }2 ) exhibits high phosphinyl radical character. This compound offers access to the phosphinidene complex [Os(PMes*)H(PNP)] by P-H proton coupled electron transfer (PCET). The P-H bond dissociation energy (BDE) was determined by isothermal titration calorimetry and supporting DFT computations. The phosphinidene product exhibits electrophilic reactivity as demonstrated by intramolecular C-H activation.
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  • Journal Article

    A bio-inspired imidazole-functionalised copper cage complex 

    Bete, Sarah C.; Würtele, Christian; Otte, Matthias
    Chemical Communications 2019; 55(30) p.4427-4430
    An imidazole-functionalised cage is synthesised that can coordinate to Cu(i). X-ray analysis reveals a T-shaped coordination of copper by the imidazole ligands reminiscent of the coordination geometry found in enzymatic active sites. This cage complex can catalyse the oxidation of benzylic alcohols to benzaldehydes utilizing oxygen as the terminal oxidant.
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