Beyond Kozeny–Carman: Predicting the Permeability in Porous Media

Transport in Porous Media - Various processes such as heterogeneous reactions or biofilm growth alter a porous medium’s underlying geometric structure. This significantly affects its...     

Molecular Engineering To Enhance Reactivity and Selectivity in an Ultrafast Photoclick Reaction

Light-induced 9,10-phenanthrenequinone-electron-rich alkene ( PQ-ERA ) photocycloadditions are an attractive new type of photoclick reaction, featuring fast conversions and high biocompatibility. However, the tunability of the reaction was hardly investigated up to now. To this end, we explored the influence of substituents on both reaction partners and the reaction rate between the PQs and ERAs . We identified new handles for functionalization and discovered that using enamines as ERAs leads to drastically enhanced rates (>5400 times faster), high photoreaction quantum yields ( Φ_P , up to 65 %), and multicolor emission output as well as a high fluorescence quantum yield of the adducts ( Φ_F , up to 97 %). Further investigation of the photophysical and photochemical properties provided insights to design orthogonal reaction systems both in solution and on nanoparticle surfaces for ultrafast chemoselective functionalization by photoclick reactions.     

Target-normal single spin asymmetries measured with positrons

The European Physical Journal A - The dipole response of the proton-magic nucleus $${}^{124}\hbox {Sn}$$ was previously investigated with electromagnetic and hadronic probes. Different responses...     

Rational design of a photoswitchable DNA glue enabling high regulatory function and supramolecular chirality transfer

Short, complementary DNA single strands with mismatched base pairs cannot undergo spontaneous formation of duplex DNA (dsDNA). Mismatch binding ligands (MBLs) can compensate this effect, inducing the formation of the double helix and thereby acting as a molecular glue. Here, we present the rational design of photoswitchable MBLs that allow for reversible dsDNA assembly by light. Careful choice of the azobenzene core structure results in excellent band separation of the E and Z isomers of the involved chromophores. This effect allows for efficient use of light as an external control element for duplex DNA formation and for an in-depth study of the DNA–ligand interaction by UV-Vis, SPR, and CD spectroscopy, revealing a tight mutual interaction and complementarity between the photoswitchable ligand and the mismatched DNA. We also show that the configuration of the switch reversibly dictates the conformation of the DNA strands, while the dsDNA serves as a chiral clamp and translates its chiral information onto the ligand inducing a preference in helical chirality of the Z isomer of the MBLs.

We present the rational design of photoswitchable DNA glue to trigger the reversible formation of duplex DNA by light. The supramolecular assembly shows a mutual interaction between ligand and DNA, which induces a preferred helicity in the switch.     

Dispersion-managed breathers with average normal dispersion

Analytic and numerical evidence is presented that demonstrates that a dispersion-managed breather can be supported in an optical fiber even when the average dispersion is in the normal regime. This nonlinear behavior, which is contrary to guiding-center theory, is shown to originate from the reversible dynamics associated with the strong quadratic chirp that is generated in both the anomalous and the normal dispersion regimes.     

Traceless parallel peptide purification by a first-in-class reductively cleavable linker system featuring a safety-release

Hundreds of peptides can be synthesized by automated parallel synthesizers in a single run. In contrast, the most widely used peptide purification method – high-pressure liquid chromatography (HPLC) – only allows one-by-one processing of each sample. The chromatographic purification of many peptides, therefore, remains a time-consuming and costly effort. Catch-and-release methods can be processed in parallel and potentially provide a remedy. However, no such system has yet provided a true alternative to HPLC. Herein we present the development of a side-reaction free, reductively cleavable linker. The linker is added to the target peptide as the last building block during peptide synthesis. After acidic cleavage from synthetic resin, the linker-tagged full-length peptide is caught onto an aldehyde-modified solid support by rapid oxime ligation, allowing removal of all impurities lacking the linker by washing. Reducing the aryl azide to an aniline sensitizes the linker for cleavage. However, scission does not occur at non-acidic pH enabling wash out of reducing agent. Final acidic treatment safely liberates the peptide by an acid-catalysed 1,6-elimination. We showcase this first-in-class reductively cleavable linker system in the parallel purification of a personalized neoantigen cocktail, containing 20 peptides for cancer immunotherapy within six hours.

A first-in-class reductively cleavable linker system that enables parallel and traceless purification of peptides through a safety-release is introduced with three linker types and showcased by rapid production of 20 personalized neoantigen peptides.     

Aromatic substitution by N-arylhydroxylamines—II : Generation of nitrenes from arylhydroxylamines and N-benzenesulfonylhydroxylamines and phosphorous pentoxide

Substitution of benzene by N-benzene- and N-(4-methylbenzenesulfonyl)hydroxylamines occurs in the presence of phosphorous pentoxide whereas N-methyl-N-benzenesulfonylhydroxylamine gave no substitution product under the same conditions. When N-(4-methylbenzenesulfonyl)hydroxylamine was treated with phosphorous pentoxide in pyridine, N-(4-methylbenzenesulfonimido)pyridinium ylide was formed. Nitrene intermediates are postulated to account for these products. Similarly carbazole was formed from 2-hydroxylamino[1,1′-biphenyl] and phosphorous pentoxide but with phosphorous pentachloride, 3- and 3-chloro-2-amino[1,1′-biphenyls] were formed, most likely via a nitrenium ion intermediate.     

Antimicrobial equipment of poly(isoprene) applying thiol‐ene chemistry

The functionalization of anionically polymerized isoprene with cysteamine applying the thiol‐ene reaction is reported. Antimicrobial activity is implemented by quaternization of the amino functionality by either alkylation or by protonation. The resulting polymers were tested against Gram‐positive as well as Gram‐negative bacteria strains according to the Japanese Industrial Standard Z2801:2000 protocol, partly revealing excellent biocidal performance. Thermal stability up to 200°C allows extrusion processing of the functionalized poly(isoprene)s. The best performing polymer, that is, bearing butylated ammonium‐groups, was compounded with the commodity material poly(propylene). The compound bearing 5 wt % of the biocidal polymer exhibited satisfactory biocidal properties. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Spectral filtering for mode locking in the normal dispersive regime

A theoretical model that characterizes the physical process responsible for generating ultrashort, high-energy, mode-locked pulses in a normal-dispersion laser cavity with strong spectral filtering is developed. According to this model, two of the critical physical parameters used to achieve optimal performance are the ratio of the filter bandwidth to the gain bandwidth and the placement of the output coupler in the laser cavity. The spectral filtering plays a crucial role in maintaining a short pulse duration with high energy. This phenomenon is generic to mode locking with normal dispersion.