Preparation of Biomolecule Microstructures and Microarrays by Thiol–ene Photoimmobilization

A mild, fast and flexible method for photoimmobilization of biomolecules based on the light‐initiated thiol–ene reaction has been developed. After investigation and optimization of various surface materials, surface chemistries and reaction parameters, microstructures and microarrays of biotin, oligonucleotides, peptides, and MUC1 tandem repeat glycopeptides were prepared with this photoimmobilization method. Furthermore, MUC1 tandem repeat glycopeptide microarrays were successfully used to probe antibodies in mouse serum obtained from vaccinated mice. Dimensions of biomolecule microstructures were shown to be freely controllable through photolithographic techniques, and features down to 5 μm in size covering an area of up to 75×25 mm were created. Use of a confocal laser microscope with a UV laser as UV‐light source enabled further reduction of biotin feature size opening access to nanostructured biochips.     

Silicone sampling tubes can cause drastic artifacts in measurements with aerosol instrumentation based on unipolar diffusion charging

Aerosol instrumentation based on unipolar diffusion charging has become popular in the recent years. These instruments can be made very small, making them suitable as personal monitors. In many applications, including personal monitoring, the use of flexible sampling tubes is required. We found that degassing from these sampling tubes can alter the gas composition of the aerosol, which changes the ion properties in the unipolar charger. As a result, the particle concentrations, measured with a unipolar diffusion charger are biased. The strongest effect was found with new, conductive silicone tubes, because of the degassing of siloxanes. Results obtained with one miniature diffusion size classifier unit were by a factor of approximately two too low. Partector and Nanoparticle Surface Area Monitor showed in principle the same behavior, but to a lower degree. Other tube materials were found to have even the opposite effect, i.e., the measured concentrations increased, when measuring through a tube. The largest observed increase was, however, only approximately 14%. Tygon? tubes were found to be the best compromise considering particle losses and effect on the diffusion charger.

Copyright © 2016 American Association for Aerosol Research     

Determination of Site Specific Adsorption Energies of CO on Copper

The binding energies of (isolated) CO molecules adsorbed at several atomic sites (terrace, step, kink) on a number of differently oriented copper surfaces have been measured by thermal desorption spectroscopy (TDS). In addition to the three low-indexed Cu surfaces several regular stepped and kinked single crystal surfaces have been employed. Using LEED measurements together with available data in the literature allowed identification of the various different CO adlayers and to assign the different TDS binding energies to the different adsorbate sites. For the close-packed surfaces binding energies between 47 kJ/mol (Cu(111)) and 51 kJ/mol (Cu(100)) were observed, which increased to 58 kJ/mol for CO molecules bound to step edges. Unexpectedly, for kink sites the same binding energy (to within 1 kJ/mol) as for step edges was observed. Moreover, a very similar binding energy of 58 kJ/mol was also measured for random defect sites on sputtered and on poly-crystalline substrates.     

Gas Transport Mechanisms through Molecular Thin Carbon Nanomembranes

Molecular thin carbon nanomembranes (CNMs) synthesized by electron irradiation induced cross-linking of aromatic self-assembled monolayers (SAMs) are promising 2D materials for the next generation of filtration technologies. Their unique properties including ultimately low thickness of ≈1 nm, sub-nanometer porosity, mechanical and chemical stability are attractive for the development of innovative filters with low energy consumption, improved selectivity, and robustness. However, the permeation mechanisms through CNMs resulting in, e.g., an ≈1000 times higher fluxes of water in comparison to helium have not been yet understood. Here, a study of the permeation of He, Ne, D₂, CO₂, Ar, O₂ and D₂O using mass spectrometry in the temperature range from room temperature to ≈120 °C is studied. As a model system, CNMs made from [1″,4′,1′,1]-terphenyl-4-thiol SAMs are investigated. It is found out that all studied gases experience an activation energy barrier upon the permeation which scales with their kinetic diameters. Moreover, their permeation rates are dependent on the adsorption on the nanomembrane surface. These findings enable to rationalize the permeation mechanisms and establish a model, which paves the way toward the rational design not only of CNMs but also of other organic and inorganic 2D materials for energy-efficient and highly selective filtration applications.     

Trapped Pore Waters in the Open Proton Channel HV1

The voltage-gated proton channel, H_V1, is crucial for innate immune responses. According to alternative hypotheses, protons either hop on top of an uninterrupted water wire or bypass titratable amino acids, interrupting the water wire halfway across the membrane. To distinguish between both hypotheses, the water mobility for the putative case of an uninterrupted wire is estimated. The predicted single-channel water permeability 2.3 × 10⁻¹² cm³ s⁻¹ reflects the permeability-governing number of hydrogen bonds between water molecules in single-file configuration and pore residues. However, the measured unitary water permeability does not confirm the predicted value. Osmotic deflation of reconstituted lipid vesicles reveals negligible water permeability of the H_V1 wild-type channel and the D174A mutant open at 0 mV. The conductance of 1400 H⁺ s⁻¹ per wild-type channel agrees with the calculated diffusion limit for a ≈2 Å capture radius for protons. Removal of a charged amino acid (D174) at the pore mouth decreases H⁺ conductance by reducing the capture radius. At least one intervening amino acid contributes to H⁺ conductance while interrupting the water wire across the membrane.     

The impact of product characteristics and innovativeness on the benefits of collaboration

Horizontal collaboration is a promising avenue to improve the efficiency of logistical operations. However, the benefits strongly depend on the degree of fit between partners. In this paper, we analyze the impact of the partners' product characteristics on those benefits, focusing on their innovativeness. Companies supplying functional versus innovative products have different requirements in supply chain efficiency and responsiveness, which impacts the benefits that can be reached with a given partner. To assess the collaborative benefits, we use a location–inventory model accounting for the partners' individual interests and the costs revealing the responsiveness level of the supply chain (facilities, transportation, cycle inventory, safety stocks and stock-outs). The model offers a set of Pareto-optimal solutions balancing the partners' costs to support the selection and negotiation process. Finally, we perform numerical experiments in which the partners supply products with identical or different levels of innovativeness and with various demand volumes, leading to valuable managerial insights on the impact of product characteristics on collaborative benefits.     

Alkoxy‐Substituted Hexastyrylbenzenes

Star‐shaped compounds 2a–e with a central benzene ring and six p‐substituted, (E)‐configured styryl groups have been prepared by a sequence of three‐fold Heck and three‐fold Wittig–Horner reactions. Alkoxy chains (OC₃H₇, OC₆H₁₃, OC₁₀H₂₁, OC₁₂H₂₅) on all six arms guarantee a good solubility of 2a–d , whereas the alternating hexyloxy and cyano substitution in 2e leads to an almost insoluble push‐pull system. Irradiation into the long‐wavelength absorption of 2a–d (with λ_max values of 341–342 nm) results in a statistical photocross‐linking, which is characterized by the complete degradation of all stilbene chromophores.