Speciation of gadolinium in surface water samples and plants by hydrophilic interaction chromatography hyphenated with inductively coupled plasma mass spectrometry

Hydrophilic interaction chromatography (HILIC) coupled with inductively coupled plasma mass spectrometry (ICP-MS) was optimized for speciation analysis of gadolinium-based contrast agents in environmental samples, in particular surface river waters and plants. Surface water samples from the Teltow channel, near Berlin, were investigated over a distance of 5 km downstream from the influx of a wastewater treatment plant. The total concentration of gadolinium increased significantly from 50 to 990 ng?L^?1 due to the influx of the contrast agents. After complete mixing with the river water, the concentration remained constant over a distance of at least 4 km. Two main substances [Dotarem® (Gd-DOTA) and Gadovist® (Gd-BT-DO3A)] have been identified in the river water using standards. A gadolinium-based contrast agent, possibly Gd-DOTA (Dotarem®), was also detected in water plant samples taken from the Teltow channel. Therefore, uptake of contrast agents [Gadovist® (Gd-BTDO3A), Magnevist® (Gd-DTPA), Omniscan® (Gd-DTPA-BMA), Dotarem® (Gd-DOTA), and Multihance® (Gd-BOPTA)] by plants was investigated in a model experiment using Lepidium sativum (cress plants). HILIC–ICP-MS was used for identification of different contrast agents, and a first approach for quantification using aqueous standard solutions was tested. For speciation analysis, all investigated contrast agents could be extracted from the plant tissues with a recovery of about 54 % for Multihance® (Gd-BOPTA) up to 106 % for Gadovist® (Gd-BT-DO3A). These experiments demonstrate that all contrast agents investigated are transported from the roots to the leaves where the highest content was measured.     

Regioselective Synthesis of Trichloromethyl‐Substituted Salicylates and Cyclohexenones by One‐Pot Cyclizations of 1,3‐Bis(trimethylsilyloxy)buta‐1,3‐dienes

A variety of 6‐(trichloromethyl)salicylates (=2‐hydroxy‐6‐(trichloromethyl)benzoates) were prepared by TiCl₄‐mediated cyclization of 1,3‐bis(trimethylsilyloxy)buta‐1,3‐dienes with 1,1,1‐trichloro‐4,4‐dimethoxybut‐3‐en‐2‐one. The employment of trimethylsilyl trifluoromethanesulfonate (Me₃SiOTf) as Lewis acid resulted in the formation of trichloromethyl‐substituted cyclohexenones. The cyclizations proceeded with good‐to‐very‐good regioselectivities.     

Anthracene Based Bulky Diol Hosts. Crystal Structures of a Free Host and of Inclusion Compounds with Dipolar Guests

X-ray crystal structures are reported of a free host compound 1, comprising two diphenylmethanol terminal groups attached to a central 9,10-ethynyl substituted anthracene unit, and of three inclusion compounds of a fluoren-9-ol substituted analogous host 2 with acetone, dimethyl sulphoxide (DMSO) and dimethylformamide (DMF) as guest, respectively. Despite the presence of two hydroxyl groups in 1, there is no O–H...O hydrogen bond between the molecules in the guest free crystal – only weaker C–H...O interactions and van der Waals' type connections. In the inclusion compounds of 2, H-bonded 1:2 host–guest associates are formed, where each of the host hydroxyl groups binds to a guest oxygen atom. The orientations of the host–guest connections in these complexes vary, being E for acetone and Z for both DMSO and DMF guests, relative to the host anthracene unit. The DMSO and DMF inclusion compounds of 2 proved to be isostructural.     

Cosmetic Formulations with Melaleuca alternifolia Essential Oil for the Improvement of Photoaged Skin: A Double-Blind,Randomized, Placebo-Controlled Clinical Study

This aim of this study was to evaluate the penetration depth, antioxidant capacity and the clinical efficacy of Melaleuca alternifolia pure essential oil and in a nanoemulsion to prevent skin photoaging. For this, 2% of pure essential oil or 2% of this essential oil in a nanoemulsion were vehiculated in a formulation. The skin penetration was evaluated using confocal Raman microspectroscopy. The radical protection factor was evaluated using electron paramagnetic resonance spectroscopy. For a clinical study, 40 male participants, aged 18–28 years, were enrolled, being divided into three groups: vehicle formulation, M. alternifolia pure essential oil and M. alternifolia Nanoemulsion. All the participants also received a sunscreen SPF 50 to use during the day. Before and after 90 days of study, skin hydrolipidics and morphological characteristics were performed by skin imaging and biophysical techniques. The nanoemulsion presented a lower antioxidant capacity and a higher penetration through the stratum corneum, reaching the viable epidermis, improving the stratum granulosum morphology. The groups presented an increase in the papillary depth, improving in the dermis echogenicity and the collagen fibers. Melaleuca alternifolia essential provides the potential to improve photoaged skin, being the application of nanoemulsion able to reach deeper skin layers.     

Rado Numbers fora(x+y)=bz

In the case of existence the smallest numberN=Ra_kis called a Rado number if it is guaranteed that anyk-coloring of the numbers 1, 2, …, Ncontains a monochromatic solution of a given system of linear equations. We will determine Ra_k(a, b) for the equationa(x+y)=bzifb=2 andb=a+1. Also, the case of monochromatic sequences {x_n} generated bya(x_n+x_n+1)=bx_n+2 is discussed.     

High Electromagnetic Field Enhancement of TiO2 Nanotube Electrodes

We present the fabrication of TiO₂ nanotube electrodes with high biocompatibility and extraordinary spectroscopic properties. Intense surface‐enhanced resonance Raman signals of the heme unit of the redox enzyme Cytochrome b₅ were observed upon covalent immobilization of the protein matrix on the TiO₂ surface, revealing overall preserved structural integrity and redox behavior. The enhancement factor could be rationally controlled by varying the electrode annealing temperature, reaching a record maximum value of over 70 at 475 °C. For the first time, such high values are reported for non‐directly surface‐interacting probes, for which the involvement of charge‐transfer processes in signal amplification can be excluded. The origin of the surface enhancement is exclusively attributed to enhanced localized electric fields resulting from the specific optical properties of the nanotubular geometry of the electrode.     

Structure of star-burst dendrimers: a comparison between small angle x-ray scattering and computer simulation results

We investigated the generation dependent shape and internal structure of star-burst dendrimers under good solvent conditions using small angle x-ray scattering and molecular modeling. Measurements have been performed on poly(amidoamine) dendrimers with generations ranging from g=0 up to g=8 at low concentrations in methanol. We described the static form factor P(q) by a model taking into account the compact, globular shape as well as the loose, polymeric character of dendrimers. Monomer distributions within dendrimers are of special interest for potential applications and have been characterized by the pair correlation function gamma(r), as well as by the monomer and end-group density profile, rho(r) and rho(e)(r), respectively. Monomer density profiles and gamma(r) can be derived from P(q) by modeling and via a model independent approach using the inverse Fourier transformation algorithm first introduced by Glatter. Experimental results are compared with computer simulations performed for single dendrimers of various generations using the cooperative motion algorithm. The simulation gives direct access to gamma(r) and rho(r), allows an independent determination of P(q), and yields in addition to the scattering experiment information about the distribution of the end groups. Excellent qualitative agreement between experiment and simulation has been found.     

Bis-picket-fence corroles

Superstructured corrole ligands related to the picket-fence porphyrins were obtained from (2,6-dichlorophenyl)dipyrromethane in two steps. Condensation with an aryl aldehyde followed by oxidative ring closure yields A₂B corroles with four peripheral bromine atoms. Palladium-catalyzed fourfold amidation at these positions results in the formation of the desired sterically encumbered species, accompanied mainly by disubstituted by-products. The insertion of iron ions into the blocked cavity of the new corrole ligands proves successful when directed towards the nitrosyl derivative. The X-ray crystallographic investigation of such an iron complex allows a detailed view of the steric restraints imposed by the bulky amido substituents.