Aging of Industrial Polypropylene Surfaces in Detergent Solution and Its Consequences for Biofilm Formation.

The performance of plastic components in water-bearing parts of industrial and household appliances, often in the presence of harsh environments and elevated temperatures, critically relies on the mechanical and thermal polymer stability. In this light, the precise knowledge of aging properties of polymers formulated with dedicated antiaging additive packages as well as various fillers is crucial for long-time device warranty. We investigated and analysed the time-dependent, polymer-liquid interface aging of different industrial performance polypropylene samples in aqueous detergent solution at high temperatures (95 °C). Special emphasis was put on the disadvantageous process of consecutive biofilm formation that often follows surface transformation and degradation. Atomic force microscopy, scanning electron microscopy, and infrared spectroscopy were used to monitor and analyse the surface aging process. Additionally, bacterial adhesion and biofilm formation was characterised by colony forming unit assays. One of the key findings is the observation of crystalline, fibre-like growth of ethylene bis stearamide (EBS) on the surface during the aging process. EBS is a widely used process aid and lubricant enabling the proper demoulding of injection moulding plastic parts. The aging-induced surface-covering EBS layers changed the surface morphology and promoted bacterial adhesion as well as biofilm formation of Pseudomonas aeruginosa.

CYP17A1-independent production of the neurosteroid-derived 5α-pregnan-3ß,6α-diol-20-one in androgen-responsive prostate cancer cell lines under serum starvation and inhibition by Abiraterone.

CYP17A1-independent intratumoral steroid hormone synthesis is regarded as one possible explanation for resistance to treatment with the CYP17-inhibitor Abiraterone (Abi). The aim of our study was therefore to investigate the steroid metabolism of prostate cancer cells under serum starvation and the effects of Abi treatment. We assessed steroid metabolism in a panel of prostate cancer cells under serum starvation by radioactivity detector-coupled HPLC and HPLC-ESI-ToF-mass spectrometry after treatment with pregnenolone, progesterone and allopregnanolone. We further evaluated the effects of Abi on steroid metabolism of testosterone, dihydrotestosterone (DHT) and dehydroepiandrosterone (DHEA) by enzyme immunoassays (EIAs). Androgen-responsive cell lines metabolized pregnenolone primarily to mitogenic steroid 5α-pregnan-3ß,6α-diol-20-one under serum starvation. Co-administration of Abi lead to detectable concentrations of the Abi metabolite Δ4-Abi (D4A), known to inhibit enzymes other than CYP17A1 in steroid metabolism. In addition, co-administration of Abi abrogated pregnenolone metabolism and resulted in a CYP17A1-independent significant increase of DHEA (13- to >100-fold) and DHT (2.5-fold) in androgen-responsive cells. Our results demonstrate the CYP17A1-independent formation of 5α-pregnan-3ß,6α-diol-20-one by androgen-responsive prostate cancer cells under serum starvation and its inhibition by Abi. Its metabolism from pregnenolone suggests a major steroidogenesis shift in these cells, hinting at a neuroendocrine transdifferentiation phenomenon. The marked increase of DHEA levels by Abi resembles the steroidogenic pathways in nervous tissue, in a manner that precludes CYP17A1 activity. To which extent these processes are responsible or involved in the development of resistance to Abi, needs to be further elucidated.

Biophysical Screening of a Focused Library for the Discovery of CYP121 Inhibitors as Novel Antimycobacterials.

The development of novel antimycobacterial agents against Mycobacterium tuberculosis (Mtb) is urgently required due to the appearance of multidrug resistance (MDR) combined with complicated long-term treatment. CYP121 was shown to be a promising novel target for inhibition of mycobacterial growth. In this study, we describe the rational discovery of new CYP121 inhibitors by a systematic screening based on biophysical and microbiological methods. The best hits originating from only one structural class gave initial information about molecular motifs required for binding and activity. The initial screening procedure was followed by mode-of-action studies and further biological characterizations. The results demonstrate superior antimycobacterial efficacy and a decreased toxicity profile of our frontrunner compound relative to the reference compound econazole. Due to its low molecular weight, promising biological profile, and physicochemical properties, this compound is an excellent starting point for further rational optimization.

In-depth Profiling of MvfR-Regulated Small Molecules in Pseudomonas aeruginosa after Quorum Sensing Inhibitor Treatment.

Pseudomonas aeruginosa is a Gram-negative bacterium, which causes opportunistic infections in immuno-compromised individuals. Due to its multiple resistances toward antibiotics, the development of new drugs is required. Interfering with Quorum Sensing (QS), a cell-to-cell communication system, has shown to be highly efficient in reducing P. aeruginosa pathogenicity. One of its QS systems employs Pseudomonas Quinolone Signal (PQS) and 4-hydroxy-2-heptylquinoline (HHQ) as signal molecules. Both activate the transcriptional regulator MvfR (Multiple Virulence Factor Regulator), also called PqsR, driving the production of QS molecules as well as toxins and biofilm formation. The aim of this work was to elucidate the effects of QS inhibitors (QSIs), such as MvfR antagonists and PqsBC inhibitors, on the biosynthesis of the MvfR-regulated small molecules 2'-aminoacetophenone (2-AA), dihydroxyquinoline (DHQ), HHQ, PQS, and 4-hydroxy-2-heptylquinoline-N-oxide (HQNO). The employed synthetic MvfR antagonist fully inhibited pqs small molecule formation showing expected sigmoidal dose-response curves for 2-AA, HQNO, HHQ and PQS. Surprisingly, DHQ levels were enhanced at lower antagonist concentrations followed by a full suppression at higher QSI amounts. This particular bi-phasic profile hinted at the accumulation of a biosynthetic intermediate resulting in the observed overproduction of the shunt product DHQ. Additionally, investigations on PqsBC inhibitors showed a reduction of MvfR natural ligands, while increased 2-AA, DHQ and HQNO levels compared to the untreated cells were detected. Moreover, PqsBC inhibitors did not show any significant effect in PA14 pqsC mutant demonstrating their target selectivity. As 2-AA is important for antibacterial tolerance, the QSIs were evaluated in their capability to attenuate persistence. Indeed, persister cells were reduced along with 2-AA inhibition resulting from MvfR antagonism, but not from PqsBC inhibition. In conclusion, antagonizing MvfR using a dosage capable of fully suppressing this QS system will lead to a favorable therapeutic outcome as DHQ overproduction is avoided and bacterial persistence is reduced.

Structure-functionality relationship and pharmacological profiles of Pseudomonas aeruginosa alkylquinolone quorum sensing modulators.

An important paradigm in anti-infective research is the antivirulence concept. Pathoblockers are compounds which disarm bacteria of their arsenal of virulence factors. PqsR is a transcriptional regulator controlling the production of such factors in Pseudomonas aeruginosa, most prominently pyocyanin. In this work, a series of tool compounds based on the structure of the natural ligand 2-heptyl-4-quinolone (HHQ) were used for probing the structure-functionality relationship. Four different profiles are identified namely agonists, antagonists, inverse agonists and biphasic modulators. Molecular docking studies revealed that each class of the PqsR modulators showed distinctive interactions in the PqsR binding domain. It was found that the substituents in position 3 of the quinolone core act as a switch between the different profiles, according to their ability to donate or accept a hydrogen bond, or form a hydrophobic interaction. Finally, it was shown that only inverse agonists were able to strongly inhibit pyocyanin production.

Discovery and Biophysical Evaluation of First Low Nanomolar Hits Targeting CYP125 of M.†tuberculosis.

Tuberculosis, which is predominantly caused by Mycobacterium tuberculosis (Mtb), is still the most lethal bacterial infection with 1.5 million casualties in 2014. Moreover, the fact that the appearance of resistant mutants and long-term treatment are coupled with economic problems in developing countries hampers an efficient therapy. Interference with the essential cholesterol metabolism of Mtb could be a promising novel strategy to fight Mtb infections. CYP125, a P450 enzyme in Mtb, has been shown to play an important role in this metabolic pathway. For this reason, we used a combined screening approach involving surface plasmon resonance spectroscopy and a heme coordination assay to identify new CYP125 binders by employing a focused P450-inhibitor library. We identified the first hits with high affinity and favorable ligand efficiencies. Furthermore, frontrunner compounds also showed selectivity toward CYP121 specific to Mtb and required for its survival. To date, these are the first compounds targeting CYP125 with low nanomolar affinity.

A study of acridine and acridinium-substituted bis(terpyridine)zinc(II) and ruthenium(II) complexes as photosensitizers for O2 (1Δg) generation.

The homoleptic zinc(II) and ruthenium(II) metal complexes of bis(tridentate) 9-acridine and 10-methyl-9-acridinium-substituted terpyridines were tested for their suitability as triplet photosensitizers (PS) using the photooxidation of 1,5-dihydroxynaphthalene (DHN) to Juglone as a model reaction. Singlet oxygen (O2(1)Δg) generation is superior or comparable to Ru(bpy)3(2+) for the acridine complexes, whereas the acridinium complexes are ineffective. The molecular structure of the bis(9-(5-([2,2':6',2''-terpyridin]-4'-yl)thien-2-yl)-10-methylacridinium)zinc(II) complex ([Zn(MeATT)2][PF6]4) is determined by X-ray structure analysis, whereas for other complexes DFT calculations were performed for structural parameters to obtain insights into their electronic properties.

Tris(tetraceno)triquinacenes: synthesis and photophysical properties of threefold linearly extended tribenzotriquinacenes.

The linear extension of the rigid, C(3v)-symmetrical carbon framework of tribenzotriquinacene (TBTQ) along its three wings is reported. The key step of the extension procedure consists of a Diels-Alder reaction of three ortho-quinodimethane units generated in situ at the triquinacene core. The use of 1,4-naphthoquinone provides a facile and particularly efficient access to tris(tetraceno)-annellated triquinacenes. The steady-state photophysical properties of these new oligotetracenes bearing three mutually orthogonal chomophores are determined and analyzed by DFT calculations.

Macrocycle breathing in [2]rotaxanes with tetralactam macrocycles.

The structural dynamics of two pairs of [2]rotaxanes were compared using variable-temperature NMR. Each rotaxane had a surrounding tetralactam macrocycle with either 2,6-pyridine dicarboxamide or isophthalamide bridging units. Differences were observed in two types of rotational processes: spinning of the phenylene wall units in the surrounding macrocycle of squaraine rotaxanes and macrocycle pirouetting in xanthone rotaxanes. The rotaxanes with macrocycles containing 2,6-pyridine dicarboxamide bridges exhibited higher rotational barriers due to a cavity contraction effect, which disfavored macrocycle breathing.

Cycloaddition to an anthracene-derived macrocyclic receptor with supramolecular control of regioselectivity.

N-Ethylmaleimide and maleic anhydride add to the interior face of one anthracene wall with unusual 1,4-regioselectivity, whereas singlet oxygen adds to both anthracene walls with 9,10-regioselectivity.

A new fluorescent calix crown ether: synthesis and complex formation with alkali metal ions.

We synthesised a new N-benzylaza-21-crown-7 ether 5 with a dihydroxy coumarin as a fluorescence sensor and investigated the binding behaviour towards alkali metal cations in methanol by fluorescence titrations. The association constants are within one order of magnitude, with the exception of sodium. Potassium is the preferred binding partner (K(Na)=330 M(-1); K(K)=8600 M(-1); K(Rb)=8200 M(-1); K(Cs)=4400 M(-1)). The corresponding aza-21-crown-7 ether (6) was attached by a methylene unit to a resorcarene to give fluorescent calix crown ether 12. The binding abilities of the calix crown ether towards alkali metal ions in methanol have also been investigated, and an increasing complex stability, distinct for potassium and rubidium in comparison with 5, was found: K(Na)=440 M(-1); K(K)=110,000 M(-1); K(Rb)=63,000 M(-1); K(Cs)=20,000 M(-1). Like bis(crown ether)s, a cooperative complexation of the crown ether and the cavitand scaffold can be assumed. The proposed complex geometry is supported by Kohn-Sham DFT calculations for the potassium and caesium complexes.

Upscaling for the time-harmonic Maxwell equations with heterogeneous magnetic materials.

This paper presents a theoretical method for the upscaling of the time-harmonic Maxwell equations. We use the eddy current approximation of the Maxwell equations to describe the fields in heterogeneous materials. The magnetic permeability of the media is assumed to have random heterogeneities given by a Gaussian random field. The upscaling is based on the coarse graining method which applies projections and Green's function formalism in Fourier space to scale the electric field. An upscaled Maxwell equation is derived which includes an effective magnetic permeability tensor. The effective permeability explicitly depends on the given scale for the upscaling. The scale-dependent permeability is calculated by a second-order perturbative expansion, and we discuss the future verification and the application of the results.