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The thermodynamics of Am(III) complex formation in natural groundwater systems is one of the major topics of research in the field of high-level radioactive waste management. In this study, we investigate the absorption and luminescence properties of aqueous Am(III) complexes with a series of aliphatic dicarboxylates in order to learn the thermodynamic complexation behaviors in relation to binding geometries. The formation of Am(III) complexes with these carboxylate ligands induced distinct red shifts in the absorption spectra, which enabled chemical speciation. The formation constants determined by deconvolution of the absorption spectra showed a linear decrease for the three ligands (oxalate (Ox), malonate (Mal), and succinate (Suc)) and a mild decrease for the remaining ligands (glutarate (Glu) and adipate (Adi)). Time-resolved laser fluorescence spectroscopy (TRLFS) was used to obtain information about the aqua ligand, which indirectly indicated the bidentate bindings of these dicarboxylate ligands. A complementary attenuated total reflectance Fourier transform infrared (ATR-FTIR) study on Eu(III), which is a nonradioactive analogue of Am(III) ion, showed that the coordination modes differ depending on the alkyl chain length. Ox and Mal bind to Am(III) via side-on bidentate bindings with two carboxylate groups, resulting in the formation of stable 5- and 6-membered ring structures, respectively. On the other hand, Suc, Glu, and Adi form end-on bidentate bindings with a single carboxylate group, resulting in a 4-membered ring structure. Density functional theory calculations provided details about the bonding properties and supported the experimentally proposed coordination geometries. This study demonstrates that coordination mode-dependent changes in optical properties occur along with thermodynamic stability changes in Am(III)-dicarboxylate complexes.Based on high-resolution tandem mass spectrometry (HR-MS2) and global natural products social molecular networking (GNPS), we found that plant-derived daidzein and genistein derivatives are polyhalogenated by termite-associated Actinomadura species RB99. ACP-196 in vivo MS-guided purification from extracts of bacteria grown under optimized conditions led to the isolation of eight polychlorinated isoflavones, including six unreported derivatives, and seven novel polybrominated derivatives, two of which showed antimicrobial activity.A new approach for quantitively assessing putative crystal structures with applications in crystal structure prediction (CSP) is introduced that is based upon experimental solution- and magic-angle spinning (MAS) solid-state NMR data and density functional theory (DFT) calculation. For the specific case of tolfenamic acid (TFA), we consider experimental solution-state NMR for a range of solvents, experimental MAS NMR of polymorphs I and II, and DFT calculations for four polymorphs. The change in NMR chemical shift observed in passing from the solution state to the solid state (ΔδExperimental) is calculated as the difference between 1H and 13C experimental solid-state chemical shifts for each polymorphic form (δSolid expt) and the corresponding solution-state NMR chemical shifts (δSolution expt). Separately, we use the gauge-included projector augmented wave (GIPAW) method to calculate the NMR chemical shifts for each form (δSolid calc) and for TFA in solution (δSolution calc) using the dynamic 3D solution conng them against experimental 13C chemical shift data for forms I and II identifies matching narrow ranges of conformations, successfully predicting the conformation of tolfenamic acid in each form. This methodology can therefore be used in crystal structure prediction to both reduce the initial conformational search space and also quantitatively assess subsequent putative structures to reliably and unambiguously identify the correct structure.The non-natural cyclic amino acids (1S,3R,4S)-1-amino-3-fluoro-4-(fluoro-18F)cyclopentane-1-carboxylic acid ([18F]9) and (1S,3S,4R)-1-amino-3-fluoro-4-(fluoro-18F)cyclopentane-1-carboxylic acid ([18F]28) have been prepared in 10 and 1.7% decay corrected radiochemical yield, respectively, and in greater than 99% radiochemical purity. Cell assays in rat 9L gliosarcoma, human U87 ΔEGFR glioblastoma, and human DU145 androgen-independent prostate carcinoma tumor cells indicated that both compounds are substrates for amino acid transport primarily by system L, with some transport taking place via system ASC. In rats with 9L gliosarcoma, [18F]9 and [18F]28 provided high tumor to normal brain tissue ratios, with maximal ratios of 3.5 and 4.1, respectively. Biodistribution studies in healthy rats confirmed that both compounds are BBB permeable and that bladder accumulation is low until at least 5 min post injection.Methoxyphenols are one of the most abundant classes of biomarker tracers for atmospheric wood smoke pollution. The reactions of atmospheric oxidants (ozone, OH) with methoxyphenols can contribute to the formation of secondary organic aerosols (SOA). Here, for the first time, we use the well-established vertical wetted wall flow tube (VWWFT) reactor to assess the effect of ionic strength (I), pH, temperature, and ozone concentration on the reaction kinetics of ozone with acetosyringone (ACS), as a representative methoxyphenol compound. At fixed pH 3, typical for acidic atmospheric deliquescent particles, and at I = 0.9 M adjusted by Na2SO4, the uptake coefficient (γ) of O3 increases by 2 orders of magnitude from γ = (5.0 ± 0.8) × 10-8 on neat salt solution (Na2SO4) to γ = (6.0 ± 0.01) × 10-6 on a mixture of ACS and Na2SO4. The comparison of the uptake coefficients of O3 at different pH values indicates that the reaction kinetics strongly depends on the acidity of the phenolic group of ACS. The observed different reactivity of gas-phase ozone with ACS has implications for ozone uptake by the dilute aqueous phase of cloud droplets and by aerosol deliquescent particles loaded with inorganic salts, and it can affect the formation of SOA in the atmosphere.Criegee intermediates and alcohols are important species in the atmosphere. In this study, we use quantum chemistry and Born-Oppenheimer molecular dynamics (BOMD) simulations to investigate the reaction between methanol/ethanol and Criegee intermediates (anti- or syn-CH3CHOO) in the gas phase and at the air-water interface. Reactions at the interface are found to be much faster than those in the gas phase. When water molecules are available, loop structures can be formed to facilitate the reaction. In addition, nonloop reaction pathways characterized by the formation of hydrated protons, although with a low possibility, are also identified at the air-water interface. Implications of our results on the fate of Criegee intermediates in the atmosphere are discussed, which deepen our understanding of Criegee intermediate-alcohol chemistry in humid environments.
Read More: https://www.selleckchem.com/products/acalabrutinib.html
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