Diblock polyampholytes at the silicon–water interface: Adsorption as a function of block ratio and molecular weight

Polyampholytes are highly charged macromolecules carrying oppositely charged functional groups. This article reports on the adsorption of a weak diblock polyampholyte, poly(methacrylic acid)‐block‐poly[(dimethylamino)ethyl methacrylate], as a function of the copolymer composition and molecular weight. The adsorption experiments were performed on silicon substrates from aqueous polymer solutions at different pHs. The amount of adsorbed polyampholyte chains to the surface was determined by ellipsometry, whereas lateral structures were investigated by scanning force microscopy. A strong influence of pH on the adsorbed amount and the lateral structure formation at the surface was observed. Especially at the isoelectric point, drastic changes in adsorption behavior were detected. At low molecular weights, an increased adsorbed amount was detected, a behavior in contrast to common theoretical predictions. This phenomenon is explained by the high stability of absorbed micelles, which cover the silicon surface as a dense layer. We conclude that micelle formation is an important process for polyampholyte adsorption, which needs to be taken into account more explicitly. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 709–718, 2001     

Near-Surface Structure of Plasma Polymer Films Affects Surface Behavior in Water and its Interaction with Proteins

Using low pressure plasma polymerization, nano-scaled oxygen-rich plasma polymer films (CO) were deposited onto pristine silicon wafers as well as on nitrogen-containing plasma polymer (CN) model surfaces. We investigate the influence of the nature of the substrate as well as a potential sub-surface effect emerging from the buried CO/CN interface, just nanometers below the surface. X-ray Photoelectron Spectroscopy and Time-of-Flight Secondary Ion Mass Spectrometry revealed two important phenomena that occurred during the deposition of the terminal CO layer: (1) a strong degree of oxidation, already for 1 nm nominal thickness, and (2) a gradual transition in chemical composition between the two layers, clearly indicating that effectively a vertical chemical gradient results, even when a two-step coating process was applied. Such terminal gradient film structures were used to study film stability in aqueous environments. Molecular rearrangements were scrutinized in the top-surface in contact with water and we found that the top-surface chemistry and wetting properties of the oxygen-rich termination layer matched those of thick CO reference coatings. Nevertheless, the adsorption of green fluorescent protein (GFP) was observed to be sensitive to the CO terminal layer thickness. Namely, an enhanced protein adsorption was observed for 1–2 nm thick CO layers on CN, whereas a significantly reduced protein adsorption was seen on ≥?3 nm thick CO terminal layers. We conclude that both, surface and sub-surface conditions significantly affect protein adsorption as opposed to the traditional consideration of surface properties alone.     

Die konstitution der fungistatischen ansamycin-antibiotica ansatrienin A und B

The structure of ansatrienin A ($\text{1}$) and B ($\text{6}$) is assigned by spin decoupling experiments and chemical reactions. The ansatrienins are unique members among the ansamycin-antibiotics because of their substituent pattern in the ansa bridge.     

Alkoxide bridged Copper(II) Hinokitiolato and Tropolonato Complexes: Polymorphism,Reconstructive Phase Transition,and Magnetic Properties

Polymorphism and an unexpected reconstructive phase transition in [Cu(trop)(μ‐OMe)]₂ (trop = tropolonate) were studied by single crystal and powder X‐ray diffraction; the phase transition is associated with a huge hysteresis of ca. 200 °C. In the readily reproducible crystal form, the methoxide‐bridged dinuclear subunits aggregate to infinite chains by longer bonds in the Jahn‐Teller distorted coordination sphere. Analogous alkoxide‐bridged derivatives with the substituted ligand hinokitiol (hino), [Cu(hino)(μ‐OR)]₂ (R = Me, Et, iPr) form pairs of dinuclear complexes and aggregate to discrete tetranuclear molecules. The inter‐cation distance patterns are reflected in the magnetic properties of these two structure types: Strong antiferromagnetic coupling within the dinuclear subunits is observed in either case, but susceptibility measurements confirm differences in exchange coupling between neighboring central Cu^II atoms.     

Bioactive,Elastic, and Biodegradable Emulsion Electrospun DegraPol Tube Delivering PDGF‐BB for Tendon Rupture Repair

Healing of tendon ruptures represents a major challenge in musculoskeletal injuries and combinations of biomaterials with biological factors are suggested as viable option for improved healing. The standard approach of repair by conventional suture leads to incomplete healing or rerupture. Here, a new elastic type of DegraPol® (DP), a polyester urethane, is explored as a delivery device for platelet‐derived growth factor—BB (PDGF‐BB) to promote tendon healing. Using emulsion electrospinning as an easy method for incorporation of biomolecules within polymers, DegraPol® supports loading and release of PDGF‐BB. Morphological, mechanical and delivery device properties of the bioactive DP scaffolds, as well as differences arising due to different electrospinning parameters are studied. Emulsion electrospun DP scaffolds result in thinner fibers than pure DP scaffolds and experience decreased strain at break [%], but high enough for successful surgeon handling. PDGF‐BB is released in a sustained manner from emulsion electrospun DP, but not completely, with still large amount of it being inside the polymeric fibers after 30 d. In vitro studies show that the bioactive scaffolds promote tenocyte proliferation in serum free and serum⁺ conditions, demonstrating the potential of this surgeon‐friendly bioactive delivery device to be used for tendon repair.

     

Unexpected phenyl group rearrangement during an intramolecular Scholl reaction leading to an alkoxy-substituted hexa-peri-hexabenzocoronene

A simple dimethoxy-substituted hexa-peri-hexabenzocoronene (m-dimethoxy HBC) was unexpectedly obtained along with a bis-spirocyclic dienone during an intramolecular Scholl reaction of its para isomer.     

The unexpected versatility of P(4)S(3) as a building block in polymeric copper halide networks: 2,3-P, 1,2,3-P and all-P coordination

Layering solutions of P(4)S(3) in CH(2)Cl(2) with solutions of CuCl or CuI in CH(3)CN gives the coordination polymers (P(4)S(3))(3)(CuCl)(7) (1), (P(4)S(3))(2)(CuCl)(3) (2), (P(4)S(3))(CuI) (3) and (P(4)S(3))(CuI)(3) (4), respectively, after slow diffusion. The yellow compounds were characterised by elemental analysis, (31)P magic-angle spinning (MAS) NMR spectroscopy and single-crystal X-ray crystallography. The solid-state structures demonstrate the unexpected ligand versatility of the P(4)S(3) molecule, which interacts through two, three, or even all of the phosphorus atoms with copper according to the nature of the copper halide. Compound 1 has a three-dimensional network in which linear and cylindrical infinite CuCl subunits coexist with diatomic CuCl building blocks. For the first time, all four P atoms of the P(4)S(3) cage are involved in coordination with metal atoms. The 3D structure of 2 contains stacks of P(4)S(3) that are interconnected by slightly undulated and planar [CuCl](n) ribbons. Compound 3 is a one-dimensional polymer composed of alternating (CuI)(2) rings and P(4)S(3) bridges. The structure of 4 consists of undulated [CuI](n) layers in which the P(4)S(3) cage functions as a bridge within the layer, as well as a spacer between the layers. The (31)P MAS NMR spectra obtained are in good agreement with the solid-state structures obtained crystallographically. Thus, analytically pure 3 and 4 show singlet peaks that correspond to uncoordinated P and quartets owing to coupling with (63)Cu and (65)Cu, respectively, whereas that of 1 contains quartets according to all-P coordination. The spectrum of 2 was obtained from a sample that still contained 40 % of 1.     

Prediction of humic acid content and respiration activity of biogenic waste by means of Fourier transform infrared (FTIR) spectra and partial least squares regression (PLS-R) models

Fourier transform infrared (FTIR) spectroscopy has been proven to be an appropriate analytical method for the qualitative assessment of compost stability. This study focuses on quantitative determination of two time-consuming parameters: humic acid (HA) contents and respiration activity. Reactivity/stability and humification were quantified by respiration activities (oxygen uptake) and humic acid contents. These features are also reflected by a specific infrared spectroscopic pattern. Based on this relationship partial least squares regression (PLS-R) models for the prediction of respiration activities and humic acid contents were calculated. Characteristic wavenumber regions that are assigned to the biological/chemical parameter were selected for multivariate data analysis. The coefficient of determination (R²) obtained for the humic acid prediction model from infrared spectra was 87% with a root mean square error of cross-validation (RMSECV) of 2.6% organic dry matter (ODM). The prediction model for respiration activity resulted in a R² of 94% and a RMSECV for oxygen uptake of 2.9 mg g⁻¹ dry matter (DM).