The interaction between three widely used antimalarial drugs chloroquine, primaquine and amodiaquine with acrylamide dimer and trimer as a hydrogel model, were studied by means of density functional theory calculation in both vacuum and water environments, using the functional wb97xd with 6-31++G(d,p) basis set and polarizable continuum model (C-PCM) of solvent. According to binding energy, around −3.15 to −11.91 kJ/mol, the interaction between antimalarial compounds and hydrogel model are exothermic in nature. The extent of interaction found is primaquine > amodiaquine > chloroquine. The natural bond orbital (NBO) calculation and application of second-order perturbation theory show strong charge transfer between the antimalarial and hydrogel model. In addition, the results suggest these interactions are polar in nature, where hydrogen bonds play a principal role in stabilization of the complex. Comparing with the gas-phase, the complexes in the water environment are also stable, with suitable values of Log P (Partition coefficient), and dipolar momentum. Consequently, these results encourage to test acrylamide hydrogels as antimalarial delivery systems.
Iron is one of the most abundant non-volatile elements in the solar system. As a major component of planetary metallic alloys, its immiscibility with silicates plays a major role in planetary formation and differentiation. Information about these processes can be gained by studying the equilibrium Fe isotope fractionation between metal alloys and molten silicates at conditions of core formation. In particular, recent attention has been paid to 56 Fe/ 54 Fe equilibrium isotope fractionation at conditions relevant to Earth's core formation and the influence that light elements (O, H, C, Ni, Si and S) have had in this process. Most of these experimental studies relied on the measurement of Fe isotope fractionation from quenched phases of silicate melts and molten iron alloys. The experimental works are extremely challenging, and may suffer different drawbacks. To overcome this, we use ab-initio computational methods to perform a systematic study of the 56 Fe/ 54 Fe equilibrium isotope fractionation in molten and solid Fe 1-x S x alloys at conditions of the core formation (60 GPa, 3000 K). We show for the first time, that equilibrium isotope fractionation factors from solid systems can be used as proxies for molten systems with differences between these two methods less than 0.01 ‰ at the relevant P-T conditions. Additionally, we discuss the effect of sulphur concentration on the equilibrium Fe isotope fractionation and show that although there are some structural changes due to atom substitutions, the wide range of studied concentrations produces b -factors that are constant within ~ 0.01‰. Finally, we discuss the implications of our results for the interpretion of recent experiments and the understanding of core crystallization processes.
Using density functional theory electronic structure calculations, the equation of state, thermodynamic and elastic properties and sound wave velocities of Fe3S at pressures up to 250 GPa have been determined. Fe3S is found to be ferromagnetic at ambient conditions but becomes nonmagnetic at pressures above 50 GPa. This magnetic transition changes the c/a ratio leading to a more isotropic compressibility, and discontinuities in elastic constants and isotropic sound velocities. Thermal expansion, heat capacity and Grüneisen parameters are calculated at high pressures and elevated temperatures using the quasiharmonic approximation. We estimate Fe-Fe and Fe-S force constants, which vary with Fe environment, as well as the 56 Fe/ 54 Fe equilibrium reduced partition function in Fe3S and compare these results with recently reported experimental values. Finally, our calculations under the conditions of the Earth's inner core allow us to estimate a S content of 2.7 wt%S, assuming the only components of the inner core are Fe and Fe3S, a linear variation of elastic properties between end-members Fe and Fe3S and that Fe3S is kinetically stable. Possible consequences for the core-mantle boundary of Mars are also discussed. This is the peer-reviewed, final accepted version for American Mineralogist, published by the Mineralogical Society of America. The published version is subject to change. Cite as Authors (Year) Title. American Mineralogist, in press.
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