This paper presents recent advances in the use of molecular simulations and extended X-ray absorption fine structure (EXAFS) spectroscopy, which enable us to understand solvated ions in solution. We report and discuss the EXAFS spectra and related properties governing solvation processes of different ions in water and methanol. Molecular dynamics (MD) trajectories are coupled to electron scattering simulations to generate the MD-EXAFS spectra, which are found to be in very good agreement with the corresponding experimental measurements. From these simulated spectra, the ion-oxygen distances for the first hydration shell are in agreement with experiment within 0.05-0.1 A. The ionic species studied range from monovalent to divalent, positive and negative: K+, Ca2+, and Cl-. This work demonstrates that the combination of MD-EXAFS and the corresponding experimental measurement provides a powerful tool in the analysis of the solvation structure of aqueous ionic solutions. We also investigate the value of electronic structure analysis of small aqueous clusters as a benchmark to the empirical potentials. In a novel computational approach, we determine the Debye-Waller factors for Ca2+, K+, and Cl- in water by combining the harmonic analysis of data obtained from electronic structure calculations on finite ion-water clusters, providing excellent agreement with the experimental values, and discuss how they compare with results from a harmonic classical statistical mechanical analysis of an empirical potential.

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Spin-polarized density functional theory (DFT) calculations and periodic slab models were used to study the reactive pathways leading to corrosion products on the low-index (100) surface of iron. We determined the binding energies of CO 2 and the barrier to decomposition of adsorbed CO 2 to O + CO, as well as to the formation of adsorbed CO 3 2and H 2 CO 3 on the Fe(100) surface. The barriers of these pathways were determined with nudged elastic band (NEB) calculations. Short trajectories with DFT-based dynamics were employed to identify the most important species. These simulations (up to 0.5 ML coverage) show that CO 2 is spontaneously activated and can bind with two or all three atoms assuming bent configurations strongly reminiscent of the radical CO 2 -. This spontaneous activation of CO 2 is possible through charge rearrangement of the slab density. The CO 2 decomposition to O + CO has a barrier of 5.0 kcal/mol. The subsequent formation of CO 3 2by reaction with an incoming CO 2 is strongly favored thermodynamically. Interaction of H 2 O with the adsorbed CO 2 forms a loosely bound complex that leads to the formation of surface-bound carbonic acid, with a barrier of approximately 35.0 kcal/mol.

Recent progress in hypertension therapy allows us to select appropriate drugs from the large variety of antihypertensive drugs for treating hypertensive patients, once hypertension is diagnosed. Antihypertensive drugs include angiotensin I converting enzyme (ACE) inhibitors, diuretics, calcium entry blockers, P-adrenergic receptor antagonists, a,-adrenergic receptor antagonists, centrally acting a2-adrenergic receptor stimulants, and so forth. It may be said that we are hardly in need of any more drugs against hypertension. Most of these drugs, however, are used for "therapeutic purposes" to suppress the symptoms of hypertension by mitigation of the increased vascular tone. We do not have any prophylactic drugs, since neither the primary cause nor the pathogenesis of essential hypertension has yet been properly identified, despite intensive research on the mechanisms involved in its development.ACE inhibitors are among the most effective antihypertensives. However, studies over a period of years on the genetic and environmental determi-Advancer m Phameculogy, Volume 44 nants of hypertension, lipid abnormalities, and coronary artery disease in Utah in population-based multigenerational pedigrees (Williams et al., 1993) and related investigations revealed that the genetic loci for the structural genes for renin (Williams et al., 1993) and ACE (Jeunemaitre et al., 1992a) and the sodium antiport system (Lifton et al., 1991) were not DNA markers for hypertension.In contrast, segregating single-gene effects were found for several "intermediate phenotypes" associated with hypertension, including intraerythro- Renal Kallikrein-Kinin System in Hypertension I49Although the etiology of essential hypertension is still obscure despite all efforts to identify it, an ongoing series of studies with BN-Ka rats have led us to a reliable hypothesis on the role of the renal kallikrein-kinin system in this condition and also on its role in preventing the development of hypertension in the early stage. This chapter discusses the possible suppressive role of the renal kallikrein-kinin system in hypertension and, on this basis, will propose the novel types of antihypertensive drugs.

Cu-zeolites are able to directly convert methane to methanol via a three-step process using O 2 as oxidant. Among the different zeolite topologies, Cu-exchanged mordenite (MOR) shows the highest methanol yields, attributed to a preferential formation of active Cu–oxo species in its 8-MR pores. The presence of extra-framework or partially detached Al species entrained in the micropores of MOR leads to the formation of nearly homotopic redox active Cu–Al–oxo nanoclusters with the ability to activate CH 4 . Studies of the activity of these sites together with characterization by 27 Al NMR and IR spectroscopy leads to the conclusion that the active species are located in the 8-MR side pockets of MOR, and it consists of two Cu ions and one Al linked by O. This Cu–Al–oxo cluster shows an activity per Cu in methane oxidation significantly higher than of any previously reported active Cu–oxo species. In order to determine unambiguously the structure of the active Cu–Al–oxo cluster, we combine experimental XANES of Cu K- and L-edges, Cu K-edge HERFD-XANES, and Cu K-edge EXAFS with TDDFT and AIMD-assisted simulations. Our results provide evidence of a [Cu 2 AlO 3 ] 2+ cluster exchanged on MOR Al pairs that is able to oxidize up to two methane molecules per cluster at ambient pressure.

The fundamental adsorption of CO 2 onto poorly crystalline kaolinite (KGa-2) under conditions relevant to geologic sequestration has been investigated using a quartz crystal microbalance (QCM) and density functional theory (DFT) methods. The QCM data indicated linear adsorption of CO 2 (0−0.3 mmol of CO 2 /g of KGa-2) onto the kaolinite surface up through the gaseous state (0.186 g/cm 3 ). However, in the supercritical region, the extent of CO 2 adsorption increases dramatically, reaching a peak (0.9−1.2 mmol of CO 2 /g of KGa-2) near 0.40 g/cm 3 , before declining rapidly. DFT studies of interactions of CO 2 with kaolinite surface models confirm that surface adsorption is favored up to ∼0.34 g/cm 3 of CO 2 , showing distorted T-shaped CO 2 −CO 2 clustering, typical of supercritical CO 2 aggregation over the surface at higher densities. Beyond this point, the adsorption energy gain for any additional CO 2 becomes smaller than the CO 2 interaction energy (∼0.2 eV) in the supercritical medium, resulting in the desorption of CO 2 from the kaolinite surface.

Aqueous complexation, adsorption, and redox chemistry of actinide species at mineral surfaces have a significant impact on their transport and reactive behavior in chemically and physically heterogeneous environments. The adsorption configurations and energies of microsolvated uranyl dication species, UO(2)(H(2)O)(n)(2+), were determined on fully hydroxylated and proton-deficient α-alumina(0001)-like finite cluster models. The significant size of the models provides faithful representations of features that have emerged from periodic calculations, but most importantly, they afford us a systematic study of the adsorption mechanism, the effect of secondary solvation shells and an explicit treatment of the total charge. Based on this cluster representation, the energetics computed from the difference between the optimized structures and the appropriate reference states point to a preference for an inner-sphere type complex.