Aryl‐Phosphonate Lanthanide Complexes and Their Fluorinated Derivatives: Investigation of Their Unusual Relaxometric Behavior and Potential Application as Dual Frequency 1H/19F MRI Probes

A series of low molecular weight lanthanide complexes were developed that have high ¹H longitudinal relaxivities (r₁) and the potential to be used as dual frequency ¹H and ¹⁹F MR probes. Their behavior was investigated in more detail through relaxometry, pH‐potentiometry, luminescence, and multinuclear NMR spectroscopy. Fitting of the ¹H NMRD and ¹⁷O NMR profiles demonstrated a very short water residence lifetime (<10 ns) and an appreciable second sphere effect. At lower field strengths (20 MHz), two of the complexes displayed a peak in r₁ (21.7 and 16.3 mM ^?1 s^?1) caused by an agglomeration, that can be disrupted through the addition of phosphate anions. NMR spectroscopy revealed that at least two species are present in solution interconverting through an intramolecular binding process. Two complexes provided a suitable signal in ¹⁹F NMR spectroscopy and through the selection of optimized imaging parameters, phantom images were obtained in a MRI scanner at concentrations as low as 1 mM . The developed probes could be visualized through both ¹H and ¹⁹F MRI, showing their capability to function as dual frequency MRI contrast agents.     

Fingerprinting pre-historical symbolic artefacts by a non-destructive methodological approach

Journal of Radioanalytical and Nuclear Chemistry - A contribution to the discussion about Vila Nova de São Pedro (VNSP) as a production centre of symbolic lithic artefacts, the origin of raw...     

Effect of bulk density on flame resistance of rockwool in combined fire-resistant facings

Journal of Thermal Analysis and Calorimetry - Fire protection of steel structures is playing an increasingly important role nowadays. The fire protection of steel structures can be solved with...     

An Abnormal N‐Heterocyclic Carbene–Carbon Dioxide Adduct from Imidazolium Acetate Ionic Liquids: The Importance of Basicity

In the reaction of 1‐ethyl‐3‐methylimidazolium acetate [C₂C₁Im][OAc] ionic liquid with carbon dioxide at 125 °C and 10 MPa, not only the known N‐heterocyclic carbene (NHC)–CO₂ adduct I , but also isomeric aNHC‐CO₂ adducts II and III were obtained. The abnormal NHC‐CO₂ adducts are stabilized by the presence of the polarizing basic acetate anion, according to static DFT calculations and ab initio molecular dynamics studies. A further possible reaction pathway is facilitated by the high basicity of the system, deprotonating the initially formed NHC‐CO₂ adduct I , which can then be converted in the presence of the excess of CO₂ to the more stable 2‐deprotonated anionic abnormal NHC–CO₂ adduct via the anionic imidazolium‐2,4‐dicarboxylate according to DFT calculations on model compounds. This suggests a generalizable pathway to abnormal NHC complex formation.     

Synthesis of 1,2,7,7a-tetrahydro-1aH-cyclopropa[b]quinoline-1a-carboxylic acid derivatives, doubly constrained ACC derivatives, by a remarkable cyclopropanation process

Reaction of N-benzoyl-1,2,3,4-tetrahydroquinoline-2-carboxylic acid with acetic anhydride resulted in 1H,3H,5H-oxazolo[3,4-a]quinolin-3-one derivative 13. Different cyclopropanation processes were applied to 13, but only diazomethane in the presence of water furnished the hitherto unknown methyl 1,2,7,7a-tetrahydro-1aH-cyclopropa[b]quinoline-1a-carboxylate 14, which can be considered as a doubly constrained 1-aminocyclopropane-1-carboxylic acid system. The mechanism of the cyclopropanation was studied in detail. The new ACC ester 14 was transformed into fused tetracyclic hydantoin derivatives, which comprised a new type of heterocyclic system.     

Intranasal irradiation with the xenon chloride ultraviolet B laser improves allergic rhinitis

We earlier reported that the 308 nm xenon chloride (XeCl) ultraviolet B (UVB) laser is highly effective for the treatment of inflammatory skin diseases. Since UVB irradiation has been shown to exert both local and systemic immunosuppression, we investigated the clinical efficacy of UVB irradiation in allergic rhinitis. In an open study, groups of patients with severe allergic rhinitis received intranasal irradiation with a 308 nm XeCl UVB excimer laser for two weeks. In the low-dose group (n=10), treatment was given twice weekly, starting with 0.25x the individual minimal erythema dose (MED), whereas patients in the medium-dose group (n=8) were treated four times weekly, starting with 0.4x MED. In each group, the dosage was gradually increased. Evaluation was based on the symptom scores. The effect of the XeCl laser on the skin prick test reaction was also studied. In the low-dose group, seven patients completed the study, and there was no improvement in the nasal symptoms. In the medium-dose group, the XeCl UVB irradiation significantly inhibited the rhinorrhoea, the sneezing, the nasal obstruction and the total nasal score (p<0.05). The XeCl UVB excimer laser also inhibited the allergen-induced skin prick test in a dose-dependent manner. These results suggest that the XeCl UVB excimer laser might serve as a new therapeutic tool in the treatment of allergic rhinitis.     

Subunit rotation models activation of serotonin 5-HT<Subscript>3AB</Subscript> receptors by agonists

The N-terminal extracellular regions of heterooligomeric 3AB-type human 5-hydroxytryptamine receptors (5-HT3ABR) were modelled based on the crystal structure of snail acetylcholine binding protein AChBP. Stepwise rotation of subunit A by 5 degrees was performed between -10 degrees and 15 degrees to mimic agonist binding and receptor activation. Anticlockwise rotation reduced the size of the binding cavity in interface AB and reorganised the network of hydrogen bonds along the interface. AB subunit dimers with different rotations were applied for docking of ligands with different efficacies: 5-HT, m-chlorophenylbiguanide, SR 57227, quinolinyl piperazine and lerisetron derivatives. All ligands were docked into the dimer with -10 degrees rotation representing ligand-free, open binding cavities similarly, without pharmacological discrimination. Their ammonium ions were in hydrogen bonding distance to the backbone carbonyl of W183. Anticlockwise rotation and contraction of the binding cavity led to distinctive docking interactions of agonists with E129 and cation-pi interactions of their ammonium ions. Side chains of several further amino acids participating in docking (Y143, Y153, Y234 and E236) are in agreement with the effects of point mutations in the binding loops. Our model postulates that 5-HT binds to W183 in a hydrophobic cleft as well as to E236 in a hydrophilic vestibule. Then it elicits anticlockwise rotation to draw in loop C via pi-cation-pi interactions of its ammonium ion with W183 and Y234. Finally, closure of the binding cavity might end in rebinding of 5-HT to E129 in the hydrophilic vestibule.     

Characterisation of a hydraulic high-pressure sample introduction assisted flow injection-inductively coupled plasma time-of-flight mass spectrometry system and its application to the analysis of biological samples

A flow injection (FI) method was developed using hydraulic high-pressure nebulization as a sample introduction system, coupled to inductively coupled plasma time-of-flight mass spectrometer (ICP-TOFMS) for rapid and simultaneous determination of 19 elements. The operating conditions of the system (analyte flow rate, heating and cooling temperatures of the desolvation module, carrier gas flow rate) for the simultaneous determination of 19 analytes were optimised. The optimum parameters of the sample introduction system were found to be 1.4 ml min⁻¹ and 1.35 l min⁻¹ for the analyte solution and nebulizer flow rates, respectively. A compromised condition for heating and cooling stage temperatures of 170 and −5 °C was chosen. The detection limits were compared to those obtained by using ICP-TOFMS with alternative sample introduction techniques e.g. conventional nebulization, flow injection chemical hydride generation (FI-CHG) and the obtained results were comparable or better than those resulting from alternative sample introduction. Applying the optimised conditions the simultaneous determination of Ag, As, Ba, Cd, Co, Cu, Ga, In, Li, Mn, Mo, Pb, Sb, Se, Sn, Sr, Tl, V and Zn was carried out. Absolute detection limits (3σ) in the range of 2-750 pg and precision between 0.5 and 9.6% from five replicate measurements of 10 ng ml⁻¹ multielemental sample solutions were achieved by using a 200 μl sample loop. The developed method was applied for the analysis of certified reference materials of biological origin (TORT-2 “Lobster Hepatopancrease”, BCR-422 “Cod Muscle” and IAEA MA-B-3/TM “Fish Homogenate”), and the results showed good agreement with the certified values.