Influence of an Alkoxy Group on Bis-Triazinyl-Pyridines for Selective Extraction of Americium(III)

The extraction of americium(III), curium(III), and lanthanides(III) from nitric acid by 2,6-bis-(5,6-dimethyl-[1,2,4]-triazin-3-yl)-pyridine and 2,6-bis-(5,6-dimethyl-[1,2,4]-triazin-3-yl)-4-methoxypyridine was studied. The physico-chemical properties of these ligands, such as the protonation and complexation constants, were also determined to describe the influence of different substituent groups. The selectivity of substituted-BTP was confirmed both in complexation and in solvent extraction experiments. The presence of an alkoxy-group in position 4 of the pyridine decreases the BTP selectivity. Influence of a long alkyl chain on protonation and complexation constants was also studied with 2,6-bis-(5,6-dimethyl-[1,2,4]-triazin-3-yl)-4-dodecyloxypyridine.     

Assessing the differential affinity of small molecules for noncanonical DNA structures

The targeting of higher-order DNA structures has been thoroughly developed with G-quadruplex DNA but not with other structures like branched DNA (also known as DNA junctions). Because these alternative higher-order DNA architectures might be of high biological relevance, we implemented a high-throughput version of the FRET melting assay that enabled us to map the interactions of a candidate with four different DNA structures (duplex- and quadruplex DNA, three- and four-way junctions) in a rapid and reliable manner. We also introduce a novel index, the BONDS (branched and other noncanonical DNA selectivity) index, to conveniently quantify this differential affinity.     

Plasmonic near-field in the vicinity of a single gold nanoparticle investigated with fluorescence correlation spectroscopy

We proposed the estimation of the plasmonic near-field volume in the vicinity of a single gold nanoparticle, and observed experimentally the near-field variation due to a change in the polarization of the illuminating light. Under total-internal-reflection illumination, the plasmonic near-field volume is varied by tuning the polarization of the excitation light. The variation in the optical near-field around a single gold nanoparticle was simulated theoretically with a finite-difference time domain method, and was characterized experimentally employing a fluorescence correlation spectroscopy technique. The experimental results are in agreement quantitatively with the theoretical analysis. These results are highly relevant to important efforts to clarify the interaction between the emitter and the plasmonic antenna, and should be helpful in developing a plasmonic-enhanced total-internal-reflection fluorescence imaging microscope.     

Thermostable Transketolase from Geobacillus stearothermophilus: Characterization and Catalytic Properties

Here we have characterized the first transketolase (TK) from a thermophilic microorganism, Geobacillus stearothermophilus, which was expressed from a synthetic gene in Escherichia coli. The G. stearothermophilus TK (mTK_gst) retained 100% activity for one week at 50 °C and for 3 days at 65 °C, and has an optimum temperature range around 60–70 °C, which will be useful for preparative applications and for future biocatalyst development. The thermostability of the mTK_gst allowed us to carry out an easy, one‐step purification by heat shock treatment of crude cell extracts at 65 °C for 45 min, directly yielding 132 mg of pure mTK_gst from 1 L of culture. The reaction rate of mTK_gst with glycolaldehyde was 14 times higher at 70 °C than at 20 °C, and 4 times higher at 50 °C when compared to E. coli TK under identical conditions. When tested at 50 °C with other aldehydes as acceptors, mTK_gst activity was approximately 3 times higher than those obtained at 20 °C. Applications of this new TK in biocatalysis were performed with hydroxypyruvate as donor and three different aldehydes as acceptors – glycolaldehyde, D ‐glyceraldehyde and butyraldehyde – from which the corresponding products L ‐erythrulose 1 , D ‐xylulose 2 and 1,3‐dihydroxyhexan‐2‐one 3 were obtained, respectively. The optical rotations for products 1 and 2 indicate that the stereospecificity of mTK_gst is identical to that of other TK sources, leading to a (3S) configuration. With the non‐hydroxylated substrate, butanal, the ee value was 85% (3S), showing higher enantioselectivity than the E. coli TK (75% ee, 3S). Processes at elevated temperatures could offer opportunities to extend the applications of TK biocatalysis, by favoring hydrophobic aldehyde acceptor substrate solubility and tolerance towards non‐conventional media.     

Allelopathic Effects of Volatile Cineoles on Two Weedy Plant Species

The volatile monoterpene analogs, 1,4-cineole and 1,8-cineole, have been identified as components of many plant essential oils, but relatively little is known about their biological activities. We compared the effects of 1,4- and 1,8-cineole on two weedy plant species by monitoring germination, mitosis, root and shoot growth, chlorophyll content, and photosynthetic efficiency. 1,4-Cineole severely inhibited growth of roots and shoots, causing cork-screw shaped morphological distortion, whereas 1,8-cineole caused a decrease in root growth and germination rates. Chlorophyll fluorescence data (yield and F _v / F _m) indicated that 1,4-cineole caused significantly higher stress (P 0.001) to photosynthesis when compared to controls. Mitotic index data showed that 1,8-cineole severely decreased (P 0.001) all stages of mitosis when compared with controls, while 1,4-cineole only caused a decrease in the prophase stage (P 0.05). Although superficially similar in structure, these two cineoles appear to have different modes of action.     

HPHT treatment of CO2 containing and CO2-related brown diamonds

Ten type I diamonds containing CO₂ and three diamonds related to these (referred to as “Pseudo CO₂” diamonds) were treated by the HPHT process to observe changes in colour, colour distribution, inclusions, luminescence and spectral features in the visible to the mid-infrared regions. All samples were of predominantly brown colour before the treatment and had rather inhomogeneous colour distribution not related to strain like in classic type Ia brown diamonds. Upon HPHT treatment most of them changed to a more yellow hue, with a greenish modifying colour, but the dominant colour was still brown. The modification of colour was found to be much more discreet than it is the case for deformation-related type Ia brown diamond and the colour was not at all related to known centers such as H3. The colour modifications were caused by the destruction of broad absorption bands in the Vis–NIR spectrum by the HPHT process and generally increased transmission from 400 to 700 nm, likely related to a slight increase in single nitrogen, but no typical HPHT annealing related colour centers such as H3 and H2 were produced in the spectra of the samples. This could be confirmed by the luminescence when excited by shortwave and longwave UV light, under which all samples showed a yellow emission that was practically not modified by the treatment.The infrared spectra of the 10 CO₂ diamonds, defined by the presence of at least the CO₂ stretching (ν₃) and bending (ν₂) absorptions, were unusually modified by the HPHT treatment: the treatment caused the CO₂ bands to increase in intensity in diamonds with low to medium CO₂ content, and the apparently diminished the intensity of the nitrogen-related one phonon absorptions (when present). In the spectra of the three “Pseudo CO₂” samples, which lack by definition the CO₂ peaks, the CO₂ peaks were created and the one phonon absorption reduced by the treatment. The photoluminescence spectra exhibiting several unpublished emission peaks remained practically unchanged by HPHT processing: none of the emissions were annealed out and no new centers created.The data obtained by HPHT treatment leads us to propose, that the theory of solid CO₂ inclusions being responsible for the CO₂ absorptions in diamond may be erroneous, and that the CO₂ may be present structurally. Thus it is proposed that structurally bonded oxygen may play an important role in such diamonds.The present study indicates that treated CO₂ and “Pseudo CO₂” diamonds can in most cases not be identified by the methods available in well-equipped gemmological laboratories, since no detectable defect centers appear to be induced by the treatment.