31P and 13C NMR Investigations of a Tert Butylcalix[4]Arene-Diphosphate

Abstract

The lanthanide induced ³¹P and ¹³C shifts for calix[4]arenediphosphate 1 are studied. From these investigations an exact assignment of all the 48 C atoms was possible.     

Influence of satellite groups on telechelic antimicrobial functions of polyoxazolines

The antimicrobial activity of poly(alkyloxazoline) telechelics with one quaternary N,N-dimethyldodecylammonium (DDA) end group was found to be greatly controlled by the non-bioactive distal end group, the so-called satellite group. In systematic investigations, the nature of the latter groups was varied to explore the mechanism of the satellite effect. To this end, poly(2-alkyl-1,3-oxazoline)s (alkyl = ethyl, methyl) with a DDA-group at the terminating end and varying alkyl, aminoalkyl, and polyphenyloxazoline block satellite groups, have been synthesized. Poly(oxazoline) derivatives with polydispersity indices of 1.06-1.20 and molecular weights from 2,200 to 12,800 g . mol(-1) could be obtained. The macromolecular structures have been confirmed by NMR spectroscopy and ESI-MS measurements. The polymers were investigated with regard to their antibacterial efficiency towards the Gram-positive bacterium Staphylococcus aureus and the Gram-negative bacterium Escherichia coli. It was found that the introduction of alkyl chain satellites of 4-10 carbon atoms in length afforded antimicrobial activity of the polymers against both microbes that was about 2-3 times higher than that of the well-known structurally comparable low molecular weight biocide, dodecyltrimethylammonium chloride (DTAC). Based on the antimicrobial effects of the investigated polymers, a mechanism for the satellite effect was proposed.     

Electrical biochip technology—a tool for microarrays and continuous monitoring

Based on electrical biochips made in Si-technology cost effective portable devices have been constructed for field applications and point of care diagnosis. These miniaturized amperometric biosensor devices enable the evaluation of biomolecular interactions by measuring the redox recycling of ELISA products, as well as the electrical monitoring of metabolites. The highly sensitive redox recycling is facilitated by interdigitated ultramicroelectrodes of high spatial resolution. The application of these electrical biochips as DNA microarrays for the molecular diagnosis of viral infections demonstrates the measurement procedure. Self-assembling of capture oligonucleotides via thiol-gold coupling has been used to construct the DNA interface on-chip. Another application for this electrical detection principle is continuous measuring with bead-based biosensors. Here, paramagnetic nanoparticles are used as carriers of the bioanalytical interface in ELISA format. A Si-micromachined glucose sensor for continuous monitoring in interstitial fluid ex vivo shows the flexibility of the electrical platform. Here the novel approach is a pore membrane in micrometer-dimensions acting as a diffusion barrier. The electrochemical detection takes place in a cavity containing glucose oxidase and a Pt-electrode surface. The common hydrogen peroxide detection, together with Si technology, enable precise differential measurements using a second cavity.     

Bio‐Orthogonal Polymer Coatings for Co‐Presentation of Biomolecules

Controlled presentation of biomolecules on synthetic substrates is an important aspect for biomaterials development. If the immobilization of multiple biomolecules is required, highly efficient orthogonal surface chemistries are needed to ensure the precision of the immobilization. In this communication, chemical vapor deposition (CVD) copolymerization is used to fabricate polymer coatings with controlled ratio of alkyne and pentafluorophenyl ester (Pfp‐ester) groups. Cyclic argine‐glycine‐aspartic acid (cRGD) adhesion peptide and epidermal growth factor (EGF) are immobilized through alkyne–azide cycloaddtion (“click” chemistry) and active ester–amine reaction, respectively. Cell studies with human umbilical vein endothelial cells (HUVEC) and A431 cell lines demonstrate the biological activity of the coimmobilized biomolecules.     

Recoverable strain storage capacity of shape memory polyethylene

Shape memory polymers (SMPs) are an important class of smart materials. So far the focus of such polymers was to find suited triggers for various application fields. Thus, the potential of most of these macromolecular networks regarding their maximally storable strain capability was not explored. In this study, the polyethylenes HDPE, LDPE, and ethylene‐1‐octene (EOC) were systematically investigated with respect to their strain storage potential. To achieve maximum strains, the polymers were chemically cross‐linked in such a way that they are at the borderline between thermoplastics and elastomers. All investigated polymers showed higher strain storage than literature reported systems and exhibited excellent shape memory parameters. The highest stored strain was found for networks of EOC with fully recoverable 1400%. Interestingly, this value could not be enlarged by using EOCs with higher molecular weight, which is probably due to increasing content of entanglements as confirmed by Mooney‐Rivlin. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1033–1040     

Layer-by-layer assembled films of cellulose nanowires with antireflective properties

Natural nanowires (NWs) of cellulose obtained from a marine animal tunicate display surprisingly high uniformity and aspect ratio comparable with synthetic NWs. Their layer-by-layer assembled (LBL) films show strong antireflection (AR) properties having an origin in a novel highly porous architecture reminiscent of a "flattened matchsticks pile", with film-thickness-dependent porosity and optical properties created by randomly oriented and overlapping NWs. At an optimum number of LBL deposition cycles, light transmittance reaches nearly 100% (lambda approximately 400 nm) when deposited on a microscope glass slide and the refractive index is approximately 1.28 at lambda = 532 nm. In accordance with AR theory, the transmittance maximum red-shifts and begins to decrease after reaching the maximum with increasing film thickness as a result of increased light scattering. This first example of LBL layers of cellulose NWs can be seen as an exemplary structure for any rigid axial nanocolloids, for which, given the refractive index match, AR properties are expected to be a common property. Unique mechanical properties of the tunicate NWs are also a great asset for optical coatings.     

Aerobic oxidation of 2,3,6-trimethylphenol to trimethyl-1,4-benzoquinone with copper(II) chloride as catalyst in ionic liquid and structure of the active species

TMQ is an important precursor in industrial vitamin E synthesis. We report a "green chemistry approach" with respect to the highly selective and environmentally friendly oxidation of 2,3,6-trimethylphenol (TMP) to trimethyl-1,4-benzoquinone (TMQ) with molecular oxygen as oxidant and a copper catalyst immobilized in a molten salt. n-Butanol as co-solvent has a positive effect on the activity and selectivity. The structurally characterized catalyst, a 1-n-butyl-3-methylimidazolium oxotetracuprat, is formed in situ via hydrolysis of CuCl2 in the presence of imidazolium chloride. We propose a mechanism of oxidative phenolate activation at a [Cu4(mu4-O)]6+ core as electronically coupled electron acceptor, formation of a copper-bound phenolate radical anion, spin delocalization into the aromatic ring, and attack by triplet oxygen at the para position. Attack of Cu(I) as reduction equivalent at the peroxy radical, proton-mediated elimination of a copper(II)-hydroxo species, will either substitute a copper(I) site in the reduced oxo cluster or take up an electron from the reduced mixed valent cluster [Cu4(mu4-O)]6+ to regenerate the oxidized cluster as the active electron acceptor.     

Synthesis of polyester nanoparticles in miniemulsion obtained by radical ring-opening of BMDO and their potential as biodegradable drug carriers

5,6-Benzo-2-methylene-1,3-dioxepane (BMDO) is used to obtain degradable polymeric nanoparticles via a statistical free-radical copolymerization with MMA and styrene in direct miniemulsion. The nanoparticles are analyzed by means of IR, NMR, DLS, SEM, and TEM. They show excellent cellular uptake and drug delivery properties. The cellular uptake into HeLa cells of particles resulting from copolymerization of BMDO with styrene is drastically enhanced compared to pure polystyrene. As a model drug system, paclitaxel is incorporated in PBMDO particles and its release and the effect on HeLa cells is studied and compared to commercial drug formulations. It is found that a drug delivery system based on PBMDO shows an excellent pharmacological effect.