Refine
Has Fulltext
- no (140)
Year of publication
- 2018 (140) (remove)
Document Type
- Article (140) (remove)
Language
- English (140)
Is part of the Bibliography
- yes (140) (remove)
Keywords
- SERS (3)
- Through-space NMR shieldings (TSNMRS) (3)
- Conformational analysis (2)
- DBD dyes (2)
- DFT (2)
- DNA origami (2)
- Gas phase electron diffraction (2)
- Metabolomics (2)
- Molecular dynamics (2)
- biomarker (2)
- biomaterials (2)
- cancer (2)
- enzymes (2)
- heterocycles (2)
- isomerization (2)
- metathesis (2)
- nanoparticles (2)
- photochemistry (2)
- radiation therapy (2)
- ring-opening polymerization (2)
- ruthenium (2)
- self-assembly (2)
- stability (2)
- 1-(Dimethylamino)-1-phenyl-1-silacyclohexane (1)
- 3-Fluoro-3-methyl-3-silatetrahydropyran (1)
- 3D printing (1)
- 6-Mercaptopurine (1)
- AOT/BDAC micelles (1)
- APCI (1)
- ATCUN motif (1)
- Acetone process (1)
- Adsorption (1)
- Aerophobicity (1)
- Air bubble repellence (1)
- Alkenyl cyclohexanone (1)
- Alkenyl cyclohexenone (1)
- Alkynes (1)
- Anionic surfactant (1)
- Anisotropy (1)
- Anisotropy effect (1)
- Annelation effect (1)
- Anti-aromaticity (1)
- Anti-inflammatory (1)
- Antibody binding (1)
- Antimalarial drug detection (1)
- Antimicrobial (1)
- Arenes (1)
- Aromaticity (1)
- Artemisinin (1)
- Aryllithium compounds (1)
- Betaines (1)
- Biomaterial (1)
- Biophysical chemistry (1)
- Biopolymer (1)
- Birth Weight (1)
- Bombyx mori silk (1)
- Boric acid (1)
- Born-Oppenheimer MD (1)
- Boron exposure (1)
- C-reactive protein (1)
- Carbenes (1)
- Cartilage repair (1)
- Celastraceae (1)
- Cellular uptake (1)
- Chitosan (1)
- Chronic kidney disease (1)
- Click chemistry (1)
- Colloidal lithography (1)
- Conformation analysis (1)
- Contact angle (1)
- Correlation function (1)
- Cryo-SEM (1)
- Cyclotella (1)
- Cytotoxicity (1)
- DNA (1)
- DNA damage (1)
- DNA recognition (1)
- DNA strand breaks (1)
- DOHaD (1)
- DSC (1)
- Diatom (1)
- Dimer (1)
- Dispersion (1)
- Domino reactions (1)
- EPR spectroscopy (1)
- Ecological risk assessment (1)
- Ecotoxicology (1)
- Electro-synthesized molecularly imprinted polymer (1)
- Electrochemical sensor (1)
- Enzymes (1)
- Europium (1)
- Excimer (1)
- FRET (1)
- FSH (1)
- Fluorescence (1)
- Fluorescence correlation (1)
- Forster resonance energy transfer(FRET) (1)
- Functional organic materials (1)
- GIAO (1)
- Gestational diabetes (1)
- Gold nanotriangles (1)
- Gold surface (1)
- Gold surfaces (1)
- Guatemala (1)
- Heparin (1)
- Herbicide (1)
- Heterocycles (1)
- High School/Introductory Chemistry (1)
- Hydrogel (1)
- Hypertension (1)
- Hypoxia (1)
- In-line monitoring (1)
- Inflammation (1)
- Infrared spectroscopy (1)
- Iso-chemical-shielding surfaces (ICSS) (1)
- Janus emulsion (1)
- LH (1)
- LSPR (1)
- Lactose (1)
- Lake Peten-Itza (1)
- Lannea rivae (1)
- Lannea schweinfurthii (1)
- Large Stokes shifts (1)
- Laser-induced breakdown spectroscopy (LIBS) (1)
- Leguminosae (1)
- Leishmania (1)
- Light scattering (1)
- Low-temperature NMR (1)
- Low-temperature d-NMR (1)
- Luminescence (1)
- Lysophosphatidylcholine (1)
- M062X/6-311G** calculations (1)
- MACE (1)
- MAPbX3 (1)
- MP2 (1)
- MP2 and CCSD(T) calculations (1)
- MS (1)
- Magnetic-responsive (1)
- Mars (1)
- Matrix metalloproteinase (1)
- Maytenus boaria (1)
- Mesomerism (1)
- Metal-proton exchange reaction (1)
- Microwave chemistry (1)
- Molecular biophysics (1)
- Monte Carlo (1)
- Multifunctionality (1)
- Multivariate data analysis (1)
- NICS (1)
- NMR (1)
- NMR spectroscopy (1)
- NMR structure (1)
- Nanoparticles (1)
- Near infrared light triggered shape-recovery (1)
- Negative control (1)
- Nontarget terrestrial plants (1)
- On-demand release (1)
- Organic Chemistry (1)
- Oxygen heterocycles (1)
- PCM (1)
- PLA (1)
- Palladium-catalyzed cross-coupling of arenediazonium salts with organoindium or organobismuth reagents (1)
- Partial least squares regression (PLSR) (1)
- Perylene (1)
- Phosphatidylcholine acyl-alkyl C 32:1 (1)
- Photon Density Wave spectroscopy (1)
- Photon density wave spectroscopy (1)
- Pickering interfacial catalysis (1)
- Plant community model (1)
- Plant reproduction (1)
- Pleistocene (1)
- Poly(epsilon-caprolactone) networks (1)
- PolyNIPAM (1)
- Polymer functionalization (1)
- Polymer-coating (1)
- Polymerization (1)
- Porous poly(ether imide) microparticulate absorbers (1)
- Porous silicon (1)
- Principal component analysis (PCA) (1)
- Process analytical technology (1)
- Proline (1)
- Proteins (1)
- Pulsed interleaved excitation (1)
- RA-intramolecular hydrogen bond (1)
- Radical polymerization (1)
- Rare-earth elements (1)
- Rearrangement (1)
- Reproductive toxicity (1)
- Responsivity (1)
- Rheology (1)
- Ring current effect (1)
- STM-induced reactions (1)
- Scaffold contraction (1)
- Scaffold degradation (1)
- Scaffold stiffness (1)
- Semen parameters (1)
- Shape-memory polymer (1)
- Si(111)-7x7 (1)
- Single molecule fluorescence (1)
- Small angle neutron scattering (1)
- Sn(IV) alkoxide (1)
- Soil (1)
- Styrene (1)
- Superparamagnetic (1)
- Surface-initiated atom-transfer radical (1)
- Surfactant micelles (1)
- Switchable wettability (1)
- TCP (1)
- TEM (1)
- THP-1 cells (1)
- Temperature-memory effect (1)
- Template reaction (1)
- Tephrosia subtriflora (1)
- Testosterone (1)
- Thermo-responsive polymer (1)
- TiO2 nanotubes (1)
- Torque (1)
- Toxicity (1)
- Transient absorption (1)
- Turbid media (1)
- Type 2 Diabetes (1)
- UVB reduction (1)
- Uremic toxins (1)
- Vesicle (1)
- Vesicles (1)
- Vibronic spectrum (1)
- X-ray crystallography (1)
- X-ray diffraction (1)
- X-ray photoelectron spectroscopy (1)
- Zwitterionic surfactant (1)
- actin cytoskeleton (1)
- amphiphilic surface (1)
- anthracenes (1)
- anti-fouling materials (1)
- anti-inflammatory therapy (1)
- antifouling (1)
- antiplasmodial (1)
- aptamers (1)
- aridity (1)
- asymmetric catalysis (1)
- atomic force microscopy (1)
- azobenzene trimethylammonium bromide (1)
- biological applications of polymers (1)
- biphasic catalysis (1)
- block copolymers (1)
- bottom-up (1)
- calcium phosphate (1)
- calcium phosphate hybrid material (1)
- carbene ligands (1)
- carbohydrates (1)
- carotenoid (1)
- carotenoids (1)
- cascade reactions (1)
- catanionic surfactant bilayer (1)
- cation miscibility (1)
- cell adhesion (1)
- cell agglutination (1)
- cesium cation (1)
- charge transfer (1)
- chemical modification (1)
- chitosan (1)
- cluster models (1)
- cobalt nanoparticles (1)
- complexes (1)
- control body weight (1)
- copper (1)
- copper complex (1)
- core-shell materials (1)
- coumarins (1)
- crown compounds (1)
- crystal structure (1)
- crystallization (1)
- cyclic thermomechanical testing (1)
- cytotoxicity (1)
- dihydro-beta-agarofuran (1)
- dip-coating (1)
- dissociative electron attachment (1)
- disulfide (1)
- donor-acceptor systems (1)
- dyes/pigments (1)
- electromagnetic field enhancement (1)
- electrospray ionization mass spectrometry and modeling (1)
- endoperoxides (1)
- endothelial cells (1)
- energy-transfer (1)
- enzyme catalysis (1)
- enzyme-polymer conjugates (1)
- etanercept (1)
- fatty acids (1)
- ferromagnetic (1)
- fiber Bragg gratings (1)
- fiber etching (1)
- fiber-optical sensors (1)
- fibers (1)
- fibrinogen (1)
- fibroblast (1)
- flavonoid (1)
- flavonoids (1)
- flow photochemistry (1)
- fluorescence (1)
- fluorescent probes (1)
- focal adhesion (1)
- functionalization of polymers (1)
- galectin (1)
- gas chromatography (1)
- gelatin (1)
- gene silencing (1)
- glass (1)
- glucose homeostasis (1)
- glucosinolates (1)
- glycosynthases (1)
- gold (1)
- gold nanoparticles (1)
- gold nanotriangles (1)
- habitat (1)
- head-to-tail surfactant associates (1)
- helicenes (1)
- hemodialysis (1)
- hepcidin-25 (1)
- hybrid perovskites (1)
- hydrogel (1)
- hydrolysis (1)
- hydroxycinnamic acids (1)
- hypothalamus (1)
- immunoassay (1)
- in situ (1)
- ion beam (1)
- ionic strength (1)
- lanthanides (1)
- liposomes (1)
- low-energy electron (1)
- low-energy electrons (1)
- lupin (1)
- macrocycles (1)
- maleimide (1)
- mass spectrometry (1)
- materials science (1)
- membranes (1)
- metal complex (1)
- metal peptide (1)
- metallopeptide (1)
- metalloprotein (1)
- methylmercury (1)
- microbial activity (1)
- microgreen (1)
- microstructure (1)
- mild reaction conditions (1)
- miscibility gap (1)
- mitochondria (1)
- mold fungi (1)
- molecular weight (1)
- multiblock copolymer (1)
- multivalent ions (1)
- nanoarray (1)
- nanostructure fabrication (1)
- nanostructures (1)
- near-infrared absorption (1)
- neuropeptides (1)
- nickel (1)
- nitriles (1)
- o-Phenylenediamine (1)
- olefin metathesis (1)
- oligodepsipeptides (1)
- ontogeny (1)
- organocatalytic polymerization (1)
- oxygen plasma (1)
- pH sensing (1)
- pH-responsive (1)
- palmitoylation (1)
- pea (1)
- perovskite solar cells (1)
- photocatalytic water splitting (1)
- photocycloaddition (1)
- photodehydro-Diels-Alder reaction (1)
- photoluminescence (1)
- photolytic ablation (1)
- photonic crystals (1)
- poly(epsilon-caprolactone) (1)
- poly(lactic acid) (1)
- poly(n-butyl acrylate) (1)
- polylactide (1)
- polymer degradation (1)
- polymerization (1)
- polymyrcene (1)
- polystyrene (1)
- polysulfabetaine (1)
- polysulfobetaine (1)
- polyzwitterions (1)
- potassium (1)
- powder diffraction (1)
- prenylated flavanonol (1)
- probes (1)
- protein analysis (1)
- protein self-assembly (1)
- purity (1)
- racemization (1)
- radicals (1)
- radiosensitizers (1)
- ratiometric sensing (1)
- ratiometric sensors (1)
- reference (1)
- reference material (1)
- regioselectivity (1)
- renewable resource (1)
- rubidium cation (1)
- scale-up (1)
- scatchard plot (1)
- selective oxidations (1)
- self-healing (1)
- sesquiterpene (1)
- shape-memory effect (1)
- shape-memory polymer actuators (1)
- silkworm silk (1)
- silver nanoparticles (1)
- silver(1) complexes (1)
- singlet oxygen (1)
- skin equivalents (1)
- soft X-radiation (1)
- soft actuators (1)
- soft matter micro- and nanowires (1)
- sortase-mediated ligation (1)
- spectro-electrochemistry (1)
- spider silk (1)
- sputtering (1)
- stereocomplexation (1)
- streptavidin (1)
- structure elucidation (1)
- subtriflavanonol (1)
- superparamagnetic (1)
- supramolecular interactions (1)
- surface enhanced spectroscopy (1)
- surface-enhanced Raman spectroscopy (1)
- synthetic methods (1)
- telechelics (1)
- telomeric DNA (1)
- thermal processing of food (1)
- thermoplastics (1)
- thermoresponsive-nanogel (1)
- thiol-ene (1)
- tin(II) 2-ethylhexanoate (1)
- titania (1)
- topical (1)
- ultra-fast laser inscription (1)
- undulated nanoplatelets (1)
- upconversion (1)
- viability (1)
- volatile organic compounds (1)
- yolk-shell nanoparticles (1)
Institute
- Institut für Chemie (140) (remove)
Combining photochromism and nonlinear optical (NLO) properties of molecular switches-functionalized self-assembled monolayers (SAMs) represents a promising concept toward novel photonic and optoelectronic devices. Using second harmonic generation, density functional theory, and correlated wave function methods, we studied the switching abilities as well as the NLO contrasts between different molecular states of various fulgimide-containing SAMs on Si(111). Controlled variations of the linker systems as well as of the fulgimides enabled us to demonstrate very efficient reversible photoinduced ring-opening/closure reactions between the open and closed forms of the fulgimides. Thus, effective cross sections on the order of 10(-18) cm(-2) are observed. Moreover, the reversible switching is accompanied by pronounced NLO contrasts up to 32%. Further molecular engineering of the photochromic switches and the linker systems may even increase the NLO contrast upon switching.
Vibrationally resolved absorption and emission (fluorescence) spectra of perylene and its N-derivatives in gas phase and in solution (acetonitrile) were simulated using a time-dependent approach based on correlation functions determined by density functional theory. By systematically varying the number and position of N atoms, it is shown that the presence of nitrogen heteroatoms has a negligible effect on the molecular structure and geometric distortions upon electronic transitions, while spectral properties change: in particular the number of N atoms is important while their position is less decisive. Thus, the N-substitution can be used to fine-tune the optical properties of perylene-based molecules.
We use clusters for the modeling of local ion resonances caused by low energy charge carriers in STM-induced desorption of benzene derivates from Si(111)-7 x 7. We perform Born-Oppenheimer molecular dynamics for the charged systems assuming vertical transitions to the charged states at zero temperature, to rationalize the low temperature activation energies, which are found in experiment for chlorobenzene. Our calculations suggest very similar low temperature activation energies for toluene and benzene. For the cationic resonance transitions to physisorption are found even at 0 K, while the anion remains chemisorbed during the propagations. Further, we also extend our previous static quantum chemical investigations to toluene and benzene. In addition, an in depth analysis of the ionization potentials and electron affinities, which are used to estimate resonance energies, is given.
Superparamagnetic cobalt nanoparticles (Co NPs) are an interesting material for self-assembly processes because of their magnetic properties. We investigated the magnetic field-induced assembly of superparamagnetic cobalt nanoparticles and compared three different approaches, namely, the assembly on solid substrates, at water-air, and ethylene glycol-air interfaces. Oleic acid- and trioctylphosphine oxide-coated Co NPs were synthesized via a thermolysis of cobalt carbonyl and dispersed into either hexane or toluene. The Co NP dispersion was dropped onto different substrates (e.g., transmission electron microscopy (TEM) grid, silicon wafer) and onto liquid surfaces. Transmission electron microscopy (TEM), scanning force microscopy, optical microscopy, as well as scanning electron microscopy showed that superparamagnetic Co NPs assembled into one-dimensional chains in an external magnetic field. By varying the concentration of the Co NP dispersion (1-5 mg/mL) and the strength of the magnetic field (4-54 mT), the morphology of the chains changed. Short, thin, and flexible chain structures were obtained at low NP concentration and low strength of magnetic field, whereas they became long, thick and straight when the NP concentration and the magnetic field strength increased. In comparison, the assembly of Co NPs from hexane dispersion at ethylene glycol-air interface showed the most regular and homogeneous alignment, since a more efficient spreading could be achieved on ethylene glycol than on water and solid substrates.
Hypothesis: An effective way for fixating vesicle structures is the insertion of monomers and cross-linking agents into their bilayer, and their subsequent polymerization can lead to the formation of polymeric nanocapsules. Particularly attractive here are vesicle systems that form spontaneously well-defined small vesicles, as obtaining such small nanocapsules with sizes below 100 nm is still challenging. Experiments: A spontaneously forming well-defined vesicle system composed of the surfactants TDMAO (tetradecyldimethylamine oxide), Pluronic L35, and LiPFOS (lithium perfluorooctylsulfonate) mixture was used as template for fixation by polymerization. Therefore, styrene monomer was incorporated into the vesicle bilayer and ultimately these structures were fixated by UV induced radical polymerization. Structural alteration of the vesicles upon loading with monomer and the cross-linker as well as the effect of subsequent polymerization in the membrane were investigated in detail by turbidity measurements, dynamic and static light scattering, (DLS, SLS), and small angle neutron scattering (SANS). Findings: The analysis showed the changes on vesicle structures due to the monomer loading, and that these structures can become permanently fixed by the polymerization process. The potential of this approach to produce well-defined nanocapsules starting from a self-assembled system and following polymerization is critically evaluated. (C) 2018 Elsevier Inc. All rights reserved.
Well-defined dihydroxy telechelic oligodepsipeptides (oDPs), which have a high application potential as building blocks for scaffold materials for tissue engineering applications or particulate carrier systems for drug delivery applications are synthesized by ring-opening polymerization (ROP) of morpholine-2,5-diones (MDs) catalyzed by 1,1,6,6-tetra-n-butyl-1,6-distanna-2,5,7,10-tetraoxacyclodecane (Sn(IV) alkoxide). In contrast to ROP catalyzed by Sn(Oct)(2), the usage of Sn(IV) alkoxide leads to oDPs, with less side products and well-defined end groups, which is crucial for potential pharmaceutical applications. A slightly faster reaction of the ROP catalyzed by Sn(IV) alkoxide compared to the ROP initiated by Sn(Oct)(2)/EG is found. Copolymerization of different MDs resulted in amorphous copolymers with T(g)s between 44 and 54 degrees C depending on the molar comonomer ratios in the range from 25% to 75%. Based on the well-defined telechelic character of the Sn(IV) alkoxide synthesized oDPs as determined by matrix-assisted laser desorption/ionization time of flight measurements, they resemble interesting building blocks for subsequent postfunctionalization or multifunctional materials based on multiblock copolymer systems whereas the amorphous oDP-based copolymers are interesting building blocks for matrices of drug delivery systems.
Stepped supporting tools were developed and used in the university seminar Organic Chemistry taken by nonmajor chemistry students, which supported self-regulated learning. These supporting tools were also used for accompanying homework, which included a QR code that led to additional supporting tools. The application of stepped supporting tools in the seminars was evaluated by a four-item Likert scale. The students assessed the tools as a helpful instrument for solving tasks in chemistry.
The aqueous self-assembly behavior of a series of poly(ethylene glycol)-poly(l-/d-lactide) block copolymers and corresponding stereocomplexes is examined by differential scanning calorimetry, dynamic light scattering, and transmission electron microscopy. Block copolymers assemble into spherical micelles and worm-like aggregates at room temperature, whereby the fraction of the latter seemingly increases with decreasing lactide weight fraction or hydrophobicity. The formation of the worm-like aggregates arises from the crystallization of the polylactide by which the spherical micelles become colloidally unstable and fuse epitaxically with other micelles. The self-assembly behavior of the stereocomplex aggregates is found to be different from that of the block copolymers, resulting in rather irregular-shaped clusters of spherical micelles and pearl-necklace-like structures.
Material surfaces with tailored aerophobicity are crucial for applications where gas bubble wettability has to be controlled, e.g., gas storage and transport, electrodes, bioreactors or medical devices. Here, we present switchable underwater aerophobicity of hydrophobic polymeric substrates, which respond to heat with multilevel micro-and nanotopographical changes. The cross-linked poly[ethylene-co-(vinyl acetate)] substrates possess arrays of microcylinders with a nanorough top surface. It is hypothesized that the specific micro-/nanotopography of the surface allows trapping of a water film at the micro interspace and in this way generates the aerophobic behavior. The structured substrates were programmed to a temporarily stable, nanoscale flat substrate showing aerophilic behavior. Upon heating, the topographical changes caused a switch in contact angle from aerophilic to aerophobic for approaching air bubbles. In this way, the initial adhesion of air bubbles to the programmed flat substrate could be turned into repellence for the recovered substrate surface. The temperature at which the repellence of air bubbles starts can be adjusted from 58 +/- 3 degrees C to 73 +/- 3 degrees C by varying the deformation temperature applied during the temperature-memory programming procedure. The presented actively switching polymeric substrates are attractive candidates for applications, where an on-demand gas bubble repellence is advantageous. (c) 2018 Helmholtz-Zentrum Geesthacht, Zentrum fur Material- und Kustenforschung. Published by Elsevier Ltd.
We discuss recent investigations of the interaction of polyelectrolytes with proteins. In particular, we review our recent studies on the interaction of simple proteins such as human serum albumin (HSA) and lysozyme with linear polyelectrolytes, charged dendrimers, charged networks, and polyelectrolyte brushes. In all cases discussed here, we combined experimental work with molecular dynamics (MD) simulations and mean-field theories. In particular, isothermal titration calorimetry (ITC) has been employed to obtain the respective binding constants K-b and the Gibbs free energy of binding. MD simulations with explicit counterions but implicit water demonstrate that counterion release is the main driving force for the binding of proteins to strongly charged polyelectrolytes: patches of positive charges located on the surface of the protein become multivalent counterions of the polyelectrolyte, thereby releasing a number of counterions condensed on the polyelectrolyte. The binding Gibbs free energy due to counterion release is predicted to scale with the logarithm of the salt concentration in the system, which is verified by both simulations and experiment. In several cases, namely, for the interaction of proteins with linear polyelectrolytes and highly charged hydrophilic dendrimers, the binding constant could be calculated from simulations to very good approximation. This finding demonstrated that in these cases explicit hydration effects do not contribute to the Gibbs free energy of binding. The Gibbs free energy can also be used to predict the kinetics of protein uptake by microgels for a given system by applying dynamic density functional theory. The entire discussion demonstrates that the direct comparison of theory with experiments can lead to a full understanding of the interaction of proteins with charged polymers. Possible implications for applications, such as drug design, are discussed.
Strategies to surface-functionalize scaffolds by covalent binding of biologically active compounds are of fundamental interest to control the interactions between scaffolds and biomolecules or cells. Poly(para-dioxanone) (PPDO) is a clinically established polymer that has shown potential as temporary implant, eg, for the reconstruction of the inferior vena cava, as a nonwoven fiber mesh. However, PPDO lacks suitable chemical groups for covalent functionalization. Furthermore, PPDO is highly sensitive to hydrolysis, reflected by short in vivo half-life times and degradation during storage. Establishing a method for covalent functionalization without degradation of this hydrolyzable polymer is therefore important to enable the surface tailoring for tissue engineering applications. It was hypothesized that treatment of PPDO with an N-hydroxysuccinimide ester group bearing perfluorophenyl azide (PFPA) under UV irradiation would allow efficient surface functionalization of the scaffold. X-ray photoelectron spectroscopy and attenuated total reflectance Fourier-transformed infrared spectroscopy investigation revealed the successful binding, while a gel permeation chromatography study showed that degradation did not occur under these conditions. Coupling of a rhodamine dye to the N-hydroxysuccinimide esters on the surface of a PFPA-functionalized scaffold via its amine linker showed a homogenous staining of the PPDO in laser confocal microscopy. The PFPA method is therefore applicable even to the surface functionalization of hydrolytically labile polymers, and it was demonstrated that PFPA chemistry may serve as a versatile tool for the (bio-)functionalization of PPDO scaffolds.
Here we present a self-made annular continuous-flow reactor that can be used in the UV/vis range in an internal numbering-up manner. As a model reaction, we chose a powerful batch-scale-limited benzoannelation method, namely, an intramolecular photodehydro-Diels-Alder (IMPDDA) reaction. The scale-up potential of this particular photochemical benchmark reaction toward the preparation of macrocylic (1,7)naphthalenophanes by variation of selected flow parameters is presented.
Different signal amplification strategies to improve the detection sensitivity of immunoassays have been applied which utilize enzymatic reactions, nanomaterials, or liposomes. The latter are very attractive materials for signal amplification because liposomes can be loaded with a large amount of signaling molecules, leading to a high sensitivity. In addition, liposomes can be used as a cell-like "bioscaffold" to directly test recognition schemes aiming at cell-related processes. This study demonstrates an easy and fast approach to link the novel hydrophobic optical probe based on [1,3]dioxolo[4,5-f]-[1,3]benzodioxole (DBD dye mm239) with tunable optical properties to hydrophilic recognition elements (e.g., antibodies) using liposomes for signal amplification and as carrier of the hydrophobic dye. The fluorescence properties of mm239 (e.g., long fluorescence lifetime, large Stokes shift, high photostability, and high quantum yield), its high hydrophobicity for efficient anchoring in liposomes, and a maleimide bioreactive group were applied in a unique combination to build a concept for the coupling of antibodies or other protein markers to liposomes (coupling to membranes can be envisaged). The concept further allowed us to avoid multiple dye labeling of the antibody. Here, anti-TAMRA-antibody (DC7-Ab) was attached to the liposomes. In proof-of-concept, steady-state as well as time-resolved fluorescence measurements (e.g., fluorescence depolarization) in combination with single molecule detection (fluorescence correlation spectroscopy, FCS) were used to analyze the binding interaction between DC7-Ab and liposomes as well as the binding of the antigen rhodamine 6G (R6G) to the antibody. Here, the Forster resonance energy transfer (FRET) between mm239 and R6G was monitored. In addition to ensemble FRET data, single-molecule FRET (PIE-FRET) experiments using pulsed interleaved excitation were used to characterize in detail the binding on a single-molecule level to avoid averaging out effects.
Dynamic and direct visualization of interfacial evolution is helpful in gaining fundamental knowledge of all-solid-state-lithium battery working/degradation mechanisms and clarifying future research directions for constructing next-generation batteries. Herein, in situ and in operando synchrotron X-ray tomography and energy dispersive diffraction were simultaneously employed to record the morphological and compositional evolution of the interface of InLi-anode|sulfide-solid-electrolyte during battery cycling. Compelling morphological evidence of interfacial degradation during all-solid-state-lithium battery operation has been directly visualized by tomographic measurement. The accompanying energy dispersive diffraction results agree well with the observed morphological deterioration and the recorded electrochemical performance. It is concluded from the current investigation that a fundamental understanding of the phenomena occurring at the solid-solid electrode|electrolyte interface during all-solid-state-lithium battery cycling is critical for future progress in cell performance improvement and may determine its final commercial viability.
The combination of gold nanoparticles with liposomes is important for nano- and biotechnology. Here, we present direct, label-free characterization of liposome structure and composition at the site of its interaction with citrate-stabilized gold nanoparticles by surface-enhanced Raman scattering (SERS) and cryogenic electron microscopy (cryo-EM). Evidenced by the vibrational spectra and cryo-EM, the gold nanoparticles destroy the bilayer structure of interacting liposomes in the presence of a high amount of citrate, while at lower citrate concentration the nanoparticles interact with the surface of the intact liposomes. The spectra of phosphatidylcholine and phosphatidylcholine/sphingomyelin liposomes show that at the site of interaction the lipid chains are in the gel phase. The SERS spectra indicate that cholesterol has strong effects on the contacts of the vesicles with the nanoparticles. By combining cryo-EM and SERS, the structure and properties of lipid nanoparticle composites could be tailored for the development of drug delivery systems.
8-Allylcoumarins are conveniently accessible through a microwave-promoted tandem Claisen rearrangement/Wittig olefination/cyclization sequence. They serve as a versatile platform for the annellation of five- to seven-membered rings using ring-closing olefin metathesis (RCM). Furano-, pyrano-, oxepino- and azepinocoumarins were synthesized from the same set of precursors using Ru-catalyzed double bond isomerizations and RCM in a defined order. One class of products, pyrano[2,3-f]chromene-2,8-diones, were inaccessible through direct RCM of an acrylate, but became available from the analogous allyl ether via an assisted tandem catalytic RCM/allylic oxidation sequence.
The series of novel 3,3′-bis(trisarylsilyl)- and 3,3′-bis(arylalkylsilyl)-substituted binaphtholate rare-earth-metal complexes 2a–i (SiR3 = Si(o-biphenylene)Ph (a), SiCyPh2 (b), Si-t-BuPh2 (c), Si(i-Pr)3 (d), SiCy2Ph (e), Si(2-tolyl)Ph2 (f), Si(4-t-Bu-C6H4)3 (g), Si(4-MeO-C6H4)Ph2 (h), SiBnPh2 (i)) have been prepared via arene elimination from [Ln(o-C6H4CH2NMe2)3] (Ln = Y, Lu) and the corresponding 3,3′-bis(silyl)-substituted binaphthol. The complexes exhibit high catalytic activity in the hydroamination/cyclization of aminoalkenes, with activities exceeding 1000 h–1 for (R)-2f-Ln, (R)-2g-Ln, and (R)-2h-Ln in the cyclization of 2,2-diphenylpent-4-enylamine (3a) at 25 °C, while the rigid dibenzosilole-substituted complexes (R)-2a-Ln and the triisopropylsilyl-substituted complexes (R)-2d-Ln exhibited the lowest activity in the range of 150–270 h–1. Catalysts (R)-2b-Lu, (R)-2c-Lu, (R)-2f-Lu, and (R)-2i-Lu provide the highest selectivities for the majority of the substrates, while the yttrium congeners are usually less selective. The highest enantioselectivities of 96% ee were observed using (R)-2a-Lu and (R)-2c-Lu in the cyclization of (4E)-2,2,5-triphenylpent-4-enylamine (9). The reactions show apparently zero-order rate dependence on substrate concentration and first-order rate dependence on catalyst concentration, with some reactions exhibiting a slightly accelerated rate at high conversion due to a shift in the equilibrium between a less active, higher coordinate catalyst species in favor of a more active, lower coordinate species as a result of weaker binding of the hydroamination product in comparison to the aminoalkene substrate. The shift in equilibrium from the higher to the lower coordinate species is also entropically favored at elevated temperatures, which results in an unusual increase in selectivity in the cyclization of 2,2-dimethylpent-4-enylamine (3d), presumably due to a higher selectivity of the lower coordinate catalyst species. All binaphtholate yttrium complexes, except (R)-2a-Y, are catalytically active in the intermolecular hydroamination of benzylamines with terminal alkenes. The highest selectivity of 66% ee was observed for the reaction of benzylamine with 4-phenyl-1-butene using (R)-2h-Y at 110 °C.
Non-Born-Oppenheimer quantum dynamics of H-2(+) and HD+ excited by single one-cycle laser pulses linearly polarized along the molecular (z) axis have been studied within a three-dimensional model, including the internuclear distance R and electron coordinates z and rho, by means of the numerical solution of the time-dependent Schrodinger equation on the timescale of about 200 fs. Laser carrier frequencies corresponding to the wavelengths of lambda(l) = 400 and 50 nm have been used and the amplitudes of the pulses have been chosen such that the energies of H-2(+) and HD+ are above the dissociation threshold after the ends of the laser pulses. It is shown that excitation of H-2(+) and HD+ above the dissociation threshold is accompanied by formation of vibrationally "hot" and "cold" ensembles of molecules. Dissociation of vibrationally "hot" molecules does not prevent the appearance of post-laser-pulse electronic oscillations, parallel z oscillations, and transversal rho oscillations. Moreover, dissociation of "hot" molecules does not influence characteristic frequencies of electronic z and rho oscillations. The main difference between the laser-induced quantum dynamics of homonuclear H-2(+) and its heteronuclear isotope HD+ is that fast post-laser-pulse electronic z oscillations in H-2(+) are regularly shaped with the period of tau(shp) approximate to 30 fs corresponding to nuclear oscillations in H-2(+), while electronic z oscillations in HD+ arise as "echo pulses" of its initial excitation and appear with the period of tau(echo) approximate to 80 fs corresponding to nuclear motion in HD+. Accordingly, corresponding power spectra of nuclear motion contain strong low-frequency harmonics at omega(shp) = 2 pi/tau(shp) in H2(+) and omega(echo) = 2 pi/tau(echo) in HD+. Power spectra related to both electronic and nuclear motion have been calculated in the acceleration form. Both higher- and lower-order harmonics are generated at the laser wavelength lambda(l) = 400 nm, while only lower-order harmonics are well pronounced at lambda(l) = 50 nm. It is also shown that a rationalized harmonic order, defined in terms of the frequency of the laser-induced electronic z oscillations, agrees with the concept of inversion symmetry for electronic motion in diatomic molecules.
Fabrication of well-ordered porous silicon tubular structures using colloidal lithography and metal assisted chemical etching is reported. A continuous hexagonal hole/particle gold pattern was designed over monocrystalline silicon through deposition of polyNIPAM microspheres, followed by the surface decoration with gold nanoparticles and thermal treatment. An etching reaction with HF, ethanol and H2O2 dissolved the silicon in contact with the metal nanoparticles (NP), creating a porous tubular array in the "off-metal area". The morphological characterization revealed the formation of a cylindrical hollow porous tubular shape with external and internal diameter of approx. 900 nm and 400 nm respectively, though it can be tuned to other desired sizes by choosing an appropriate dimension for the microspheres. The porous morphology and optical properties were studied as a function of resistivity of silicon substrates. Compared to two different gold templates on cSi and nontubular porous pillar structures, porous silicon tubular framework revealed a maximum surface enhanced Raman scattering enhancement factor of 10(6) for the detection of 6-mercaptopurine (6-MP). Due to the large surface area available for any surface modification, open nanostructured platforms such as those studied here have potential applications in the field of reflection/photoluminescene and SERS based optical bio-/chemical sensors.
Hepcidin-25 was identified as themain iron regulator in the human body, and it by binds to the sole iron-exporter ferroportin. Studies showed that the N-terminus of hepcidin is responsible for this interaction, the same N-terminus that encompasses a small copper(II) binding site known as the ATCUN (amino-terminal Cu(II)- and Ni(II)-binding) motif. Interestingly, this copper-binding property is largely ignored in most papers dealing with hepcidin-25. In this context, detailed investigations of the complex formed between hepcidin-25 and copper could reveal insight into its biological role. The present work focuses on metal-bound hepcidin-25 that can be considered the biologically active form. The first part is devoted to the reversed-phase chromatographic separation of copper-bound and copper-free hepcidin-25 achieved by applying basic mobile phases containing 0.1% ammonia. Further, mass spectrometry (tandemmass spectrometry (MS/MS), high-resolutionmass spectrometry (HRMS)) and nuclear magnetic resonance (NMR) spectroscopy were employed to characterize the copper-peptide. Lastly, a three-dimensional (3D)model of hepcidin-25with bound copper(II) is presented. The identification of metal complexes and potential isoforms and isomers, from which the latter usually are left undetected by mass spectrometry, led to the conclusion that complementary analytical methods are needed to characterize a peptide calibrant or referencematerial comprehensively. Quantitative nuclear magnetic resonance (qNMR), inductively-coupled plasma mass spectrometry (ICP-MS), ion-mobility spectrometry (IMS) and chiral amino acid analysis (AAA) should be considered among others.