McNulty McCoy (graintime4)
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. 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)
