Polymeric phthalates: Potential nonmigratory macromolecular plasticizers

The synthesis of 4‐vinyl‐1,2‐phthalate esters via Suzuki coupling is described, followed by nitroxide‐mediated polymerization to prepare short homopolymers (degree of polymerization [DP] = 10–40, polydispersity index [PDI] = 1.1–1.3). Random copolymers with n‐butyl acrylate (NBA) were prepared. Copolymers rich in phthalate ester residues of medium lengths (DP = 16–48, PDI = 1.2–1.8) and of shorter lengths (DP = 8–17, PDI = 1.2–1.3) were prepared. Copolymers rich in NBA residues were also prepared (DP = 13–19, PDI = 1.2–1.3). All polymers were oily liquids, with glass transitions temperatures undetected between 75 and ?40 °C, indicating these polymeric phthalates hold promise as potential nonmigratory phthalate plasticizers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Numerical Solution of the Fokker-Planck Equation with Time-Discontinuous Galerkin Methods

The response of non-linear dynamic systems under white noise excitation possesses Markov characteristics. The evolution of the probability density of the system response is represented by the Fokker-Planck equation, which characterizes advection and diffusion. The solution probability density distribution often possesses high gradients. Therefore an efficient numerical solution technique based on a discontinuous Galerkin approximation in the time domain is proposed for the solution of the Fokker-Planck equation. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Polypropylene–MAlN (M = Ti,Cr) interface interactions

We have studied the influence of transition metal (M = Ti, Cr) and nonmetal (N, O) valence electron concentration, surface defects, and radicals on the interaction of polypropylene and cubic M_0.5Al_0.5N (002) and (111) surfaces using ab initio calculations. For the ideal and defected surface, the work of separation is low and not affected by valence electron concentration, implying weak interactions. Striking differences occur for radicals, where an increase by two orders of magnitude is observed. This may be understood based on the electronic structure. Radicals give rise to strong bonding across the interface and hence strong interactions.     

Gels of shape-persistent macrocycles: the role of the interior

The aggregation of shape-persistent macrocycles with an empty cavity, an undecyldiether strand and a tetraethylene glycol strand leads in all cases to a macroscopic gelation of the solvent. However, the gelation temperatures are fine-tuned by the intraannular substituents.     

Dramatic enhancement of enone epoxidation rates in nonionic microemulsions

The ability of microemulsions to dissolve polar and non-polar components with a huge internal interface can overcome the reagent incompatibilities frequently encountered in organic reactions. We investigated model epoxidation reactions of alpha,beta-unsaturated enones and alkaline hydrogen peroxide in different nonionic microemulsions, both in the presence and absence of a phase-transfer agent (PTA). The obtained reaction profiles were compared with those for the corresponding surfactant-free two-phase systems. In addition, we defined a time constant tau as a measure for the rate of turnover. The epoxidation of trans-chalcone using an n-alkyl-polyoxyethylene surfactant based microemulsion was fastest in the system with the PTA (tau=66 min) and slightly slower without the PTA (tau=77 min). It was still slower in the two-phase system with a PTA (tau=114 min) and extremely sluggish without a phase-transfer agent. With n-alkyl beta-D-glucopyranoside as the surfactant the conversion was twice as fast than in the former microemulsion systems, but the PTA did not accelerate the reaction further (tau=35 and 33 min). The epoxidation of vitamin K(3), the second model system, was extremely accelerated. It proceeded a factor of approximately 35 faster in the microemulsion (tau=1.44 min) than in the corresponding two-phase system (tau=57 min).     

Chemical Approach to Functional Artificial Opals

Artificial opals are self‐assembled colloidal crystals, which consist of a cubic dense packing (fcc) of hard (not film‐forming) colloids with diameters ranging from 200 to 900 nm. Because of their periodic nanostructure the assemblies are able to reflect light that matches their periodicity, i.e., UV‐ to IR‐radiation depending on the size of the colloids. Thus, they present a subgroup of ‘photonic crystals’. While, originally, the chemistry inside the colloids and the resulting opals was of minor significance, nowadays the chemical variation of opals is becoming more and more important for the preparation of functional and patterned opals. The search for functional opals is, therefore, especially focused on four topics: I) coloring agents, II) incorporation of fluorescent materials, III) replication, and IV) the controlled incorporation of defects.

     

All-in-one disulfide bridging enables the generation of antibody conjugates with modular cargo loading

Antibody–drug conjugates (ADCs) are valuable therapeutic entities which leverage the specificity of antibodies to selectively deliver cytotoxins to antigen-expressing targets such as cancer cells. However, current methods for their construction still suffer from a number of shortcomings. For instance, using a single modification technology to modulate the drug-to-antibody ratio (DAR) in integer increments while maintaining homogeneity and stability remains exceptionally challenging. Herein, we report a novel method for the generation of antibody conjugates with modular cargo loading from native antibodies. Our approach relies on a new class of disulfide rebridging linkers, which can react with eight cysteine residues, thereby effecting all-in-one bridging of all four interchain disulfides in an IgG1 antibody with a single linker molecule. Modification of the antibody with the linker in a 1 : 1 ratio enabled the modulation of cargo loading in a quick and selective manner through derivatization of the linker with varying numbers of payload attachment handles to allow for attachment of either 1, 2, 3 or 4 payloads (fluorescent dyes or cytotoxins). Assessment of the biological activity of these conjugates demonstrated their exceptional stability in human plasma and utility for cell-selective cytotoxin delivery or imaging/diagnostic applications.

Tetra-divinylpyrimidine (TetraDVP) linkers offer a method for the generation of antibody conjugates with modular cargo loading and excellent stability via all-in-one disulfide bridging.     

Variability of doublecortin-associated dendrite maturation in adult hippocampal neurogenesis is independent of the regulation of precursor cell proliferation

Background  

In the course of adult hippocampal neurogenesis most regulation takes place during the phase of doublecortin (DCX) expression, either as pro-proliferative effect on precursor cells or as survival-promoting effect on postmitotic cells. We here obtained quantitative data about the proliferative population and the dynamics of postmitotic dendrite development during the period of DCX expression. The question was, whether any indication could be obtained that the initiation of dendrite development is timely bound to the exit from the cell cycle. Alternatively, the temporal course of morphological maturation might be subject to additional regulatory events.