Biosynthesis of 15N-labeled cylindrospermopsin and its application as internal standard in stable isotope dilution analysis

Cylindrospermopsin (CYN) is a cyanobacterial toxin associated with human and animal poisonings. Due to its toxicity in combination with its widespread occurrence, the development of reliable methods for selective, sensitive detection and accurate quantification is mandatory. Liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis using stable isotope dilution analysis (SIDA) represents an ideal tool for this purpose. U-[¹⁵N₅]-CYN was synthesized by culturing Aphanizomenon flos-aquae in Na¹⁵NO₃-containing cyanobacteria growth medium followed by a cleanup using graphitized carbon black columns and mass spectrometric characterization. Subsequently, a SIDA-LC-MS/MS method for the quantification of CYN in freshwater and Brassica matrices was developed showing satisfactory performance data. The recovery ranged between 98 and 103 %; the limit of quantification was 15 ng/L in freshwater and 50 μg/kg dry weight in Brassica samples. The novel SIDA was applied for CYN determination in real freshwater samples as well as in kale and in vegetable mustard exposed to toxin-containing irrigation water. Two of the freshwater samples taken from German lakes were found to be CYN-contaminated above limit of quantification (17.9 and 60.8 ng/L). CYN is systemically available to the examined vegetable species after exposure of the rootstock leading to CYN mass fractions in kale and vegetable mustard leaves of 15.0 μg/kg fresh weight and 23.9 μg/kg fresh weight, respectively. CYN measurements in both matrices are exemplary for the versatile applicability of the developed method in environmental analysis.      

Water polyamorphism: reversibility and (dis)continuity

An understanding of water's anomalies is closely linked to an understanding of the phase diagram of water's metastable noncrystalline states. Despite the considerable effort, such an understanding has remained elusive and many puzzles regarding phase transitions in supercooled liquid water and their possible amorphous proxies at low temperatures remain. Here, decompression of very high density amorphous ice (VHDA) from 1.1 to 0.02 GPa at 140 K is studied by means of dilatometry and powder x-ray diffraction of quench-recovered states. It is shown that the three amorphous states of ice are reversibly connected to each other, i.e., LDA<-->e-HDA<-->VHDA. However, while the downstroke VHDA-->e-HDA transition takes place in the pressure range of 0.06 GPaLDA transition takes place quasi-discontinuously at p approximately 0.06 GPa. That is, two amorphous-amorphous transitions of a distinct nature are observed for the first time in a one-component system-a first-order-like transition (e-HDA-->LDA) and a transition which is not first-order like but possibly of higher order (VHDA-->e-HDA). VHDA and e-HDA are established as the most stable and limiting states in the course of the transition. We interpret this as evidence disfavoring the hypothesis of multiple first-order liquid-liquid transitions (and the option of a third critical point), but favoring a single first-order liquid-liquid transition (and the option of a second critical point).     

(Amidomethyl)pyridine zirconium and hafnium complexes: Synthesis and structural characterization

A series of 2-formyl and 2-acetylpyridines was condensed with 2,6-diisopropylaniline to yield the corresponding imines. Their reaction with sodium borohydride gave the respective N-arylaminomethylpyridines. Treatment of the N-arylformimino- or -acetiminopyridines with trimethylaluminum followed by hydrolysis furnished a series of the respective substituted N-arylaminoethylpyridine derivatives. Their reaction with tetrabenzylzirconium or tetrakis(dimethylamido)zirconium or -hafnium gave the corresponding (chelate ligand)MX₃ systems in a variety of cases. Some of these gave very active ethene polymerization catalysts upon activation with methylalumoxane. Six of the neutral aminoalkylpyridines were characterized by X-ray diffraction, as were eight of the zirconium or hafnium complexes and two aluminum chelate complex systems.     

Cultivation of Encapsulated Primary Human B Lymphocytes: A First Step toward a Bioartificial Germinal Center

Polyelectrolyte microcapsules based on sodium cellulose sulfate (SCS) and poly-diallyl-dimethyl-ammonium chloride (PDADMAC) have previously been proposed as a suitable ex vivo microenvironment for the cultivation and differentiation of primary human T lymphocytes. Here, the same system is investigated for the cultivation of human primary B cells derived from adult tonsillar tissue. Proliferation and differentiation into subtypes are followed and compared to suspension cultures of B cells from the same pool performed in parallel. Total cell expansion is somewhat lower in the capsules than in the suspension cultures. More importantly, however, the differentiation of the initially mainly memory B cells into various subtypes, in particular into plasma cell (PC), shows significant differences. Clearly, the microenvironment provided by the microcapsules is beneficial for an accelerated induction of a germinal center-like B cell phenotype and afterward supports the long-term survival of the PC cells. Then, varying the encapsulation conditions (i.e., presence of human serum and dedicated cytokines in the capsule core) provides a tool for finetuning the B cell response. Hence, this methodology is suggested to pave the way toward ex vivo development of human immune organoids.     

Quasiregular Mappings on Sub-Riemannian Manifolds

We study mappings on sub-Riemannian manifolds which are quasiregular with respect to the Carnot–Carathéodory distances and discuss several related notions. On H-type Carnot groups, quasiregular mappings have been introduced earlier using an analytic definition, but so far, a good working definition in the same spirit is not available in the setting of general sub-Riemannian manifolds. In the present paper we adopt therefore a metric rather than analytic viewpoint. As a first main result, we prove that the sub-Riemannian lens space admits nontrivial uniformly quasiregular (UQR) mappings, that is, quasiregular mappings with a uniform bound on the distortion of all the iterates. In doing so, we also obtain new examples of UQR maps on the standard sub-Riemannian spheres. The proof is based on a method for building conformal traps on sub-Riemannian spheres using quasiconformal flows, and an adaptation of this approach to quotients of spheres. One may then study the quasiregular semigroup generated by a UQR mapping. In the second part of the paper we follow Tukia to prove the existence of a measurable conformal structure which is invariant under such a semigroup. Here, the conformal structure is specified only on the horizontal distribution, and the pullback is defined using the Margulis–Mostow derivative (which generalizes the classical and Pansu derivatives).     

Miniaturized diode laser module emitting green light at 532 nm with a power of more than 900 mW for next-generation holographic displays

We present a micro-integrated laser module based on an amplified diode laser and second harmonic generation which is a promising candidate for a green light source in next-generation 3D holographic displays. The light emitted by the amplified laser has a wavelength of 1064 nm, reaches a power up to 8.2 W and has a long coherence length of >400 m. For second harmonic generation, we tested two geometries of periodically poled lithium niobate crystals in single pass: a bulk crystal and a planar waveguide crystal. With the planar waveguide crystal, we achieve an output power >900 mW and a coherence length >20 m at a wavelength of 532 nm.     

Assembly of DNA-functionalized gold nanoparticles studied by UV/Vis-spectroscopy and dynamic light scattering

The DNA mediated assembly of complementary DNA-functionalized gold nanoparticles (DNA-AuNP) was investigated by means of UV/Vis-spectroscopy and Dynamic Light Scattering (DLS). The melting temperature of the aggregates was determined to be T(m) = 31 degrees C. Characterization of the assembly at 20 degrees C, 25 degrees C and 30 degrees C showed a decrease of the initial assembly growth rate with increasing temperature. The correlation of the wavelengths at the absorbance maxima lambda(max) and the hydrodynamic radii R(h) of the AuNP assemblies proved the dependence of the optical properties on the assembly size while at higher assembly temperature (30 degrees C) a larger redshift of lambda(max) with increasing R(h) was observed than at lower temperatures. This tendency might give information about the dependence of the internal structure of the DNA-AuNP assemblies on assembly temperature. It is assumed that at higher temperatures more compact assemblies are built than at lower temperatures of 20 degrees C and 25 degrees C. To the best of our knowledge, this is the first systematic time-resolved in situ investigation of DNA-mediated AuNP assembly by UV/Vis-spectroscopy and DLS.     

Quinomethides versus unsymmetric hybrids: two variations of non-radicaloid SEM-states in four-electron redox systems of bis-4<Emphasis Type="Italic">H</Emphasis>-imidazoles

A series of bis-4H-imidazoles 1a-h has been synthesized and characterized. Due to the integration of rigid substructures, the first fluorescent 4H-imidazole 1h which possesses the substructure of pyrrolo-pyrrol was obtained. Upon protonation of bis-4H-imidazoles, a bathochromic shift of 100 to almost 200 nm was observed originating from the transformation of merocyanine chromophores into cyanines. All 4H-imidazoles were reduced chemically yielding bridged 1H-imidazoles which immediately reoxidize when exposed to air. Stable quinomethide-like species 3a,b which represent the SEM form in this four-electron redox system are only observed during the reduction of bis-4H-imidazoles 1a,b. Influenced by larger bridging elements in derivatives 1c–1h, the electronic communication between terminal 4H-imidazoles is impaired. Therefore, detection and isolation of neither quinomethide-like nor biradikaloid SEM forms succeeded. Most likely a very fast electron-transfer-step leads to unsymmetric hybrids, consisting of one 1H- and one 4H-imidazole. The new synthesized derivative 1k is not only such a stable hybrid molecule, but also may be an indication for the existence of non-quinoid SEM-forms.     

Colchicin

Colchicin was extracted from grinded seeds of meadow saffron and purified by flash chromatography and preparative HPLC. All analytical spectra were recorded and are reproduced either in the main part or in the supporting information. The NMR‐ and mass‐spectra have been interpreted and compared with theoretical calculations of the ¹³C chemical shifts. The project is a follow up of the recent book “Classics in Spectroscopy” by S. Berger und D. Sicker (Wiley‐VCH 2009).     

A New Method to Record Subglottal Pressure Waves: Potential Applications

Rapid subglottal pressure changes related to the glottal cycles influence the aerodynamics of phonation. Various methods to measure these have been developed, but are not practical for routine phoniatric use. For that reason, a noninvasive measurement tool is necessary. This article presents a technique that uses a microphone positioned at the skin of the jugular fossa to record the signal which arises in the subglottal spaces and is transmitted through the soft tissue to the surface of the skin. Using the program Glottal Segmentation of Voice and Speech, jugular microphone recordings from two healthy subjects were compared with simultaneously recorded direct intratracheal measurements during the same phonation. A systematic error arising from the transmission properties of the microphone and the soft tissue leads to phase and amplitude deviations. These must be taken into account and require correction. This correction procedure leads to high correlations and a good agreement between the two signals. Even without this correction the jugular microphone measurements proved to be useful as a diagnostic and a therapeutic tool in cases where chest resonance specific processes appear affected. In addition, they offer material for research purposes. Although based on a small number of subjects, the new method shows a good validity; testing on a larger number of subjects will probably strengthen the validity.