On the nature of inter-anion coinage bonds.

To explore the binding energy profiles and elucidate the bonding nature in counter-intuitive anion⋯anion coinage bonds (CiBs), thirty-one complexes were constructed, and the inter-anion CiBs were studied theoretically. The metastability was evidenced by the characteristic potential wells in six cases, demonstrating that anions [Au(CN)4]-, [Ag(CN)2]- and [AuO]- are appropriate building blocks for CiBs. The kinetic stability was further supported by ab initio molecular dynamics (AIMD) simulations and the analyses based on the local vibrational mode and quantum theory of atoms in molecules (QTAIM) methods. The anion⋯anion CiBs in the dimers of [AuCl4]- and [Au(CN)4]- previously observed in condensed phases were confirmed to be thoroughly repulsive under vacuum, but turned attractive in the crystal environment which was simulated using the solvation model based on density (SMD). However, the intrinsic strength of the inter-anion bonding is barely variated by the environment, as it is the combination of the inter-anion interaction and the environment effect that stabilizes the anion pairs. The block-localized wavefunction (BLW) method and its corresponding energy decomposition (BLW-ED) approach were further employed aiming at a chemically meaningful explanation for these counterintuitive phenomena. By inspecting the profiles of energy components, we identified the vital distinction between inter-anion CiBs and conventional non-covalent interactions lying in the electrostatic interaction, which variates nonmonotonically in the inter-anion complexes. The electrostatic interaction also dominates the depth of potential wells, which is commonly used to evaluate the kinetic stability, while Pauli exchange repulsion is the most repulsive factor preventing the formation of anion adducts. The importance of the Pauli exchange repulsion was further highlighted by comparing cases with and without metastability, in which the absence of a potential well is solely caused by the enhancement of the Pauli exchange repulsion.

Classical Electrostatics Remains the Driving Force for Interanion Hydrogen and Halogen Bonding.

Interanion hydrogen bonding (IAHB) and halogen bonding (IAXB) have emerged as a counterintuitive linker in a range of fascinating applications. Despite the overall repulsive (positive) binding energy, anions are trapped in a local minimum with its corresponding transition state (TS) preventing dissociation. In other words, the adduct of anions is metastable. Seemingly, the electrostatic paradigm and force field description of hydrogen/halogen bonding (HB/XB) are challenged, because of the preconceived Coulombic repulsion. Aiming at an insightful understanding of these interanion phenomena, we employed the energy decomposition approach based on the block-localized wavefunction method (BLW-ED) to investigate a series of exemplary interanion complexes. As expected, the key distinction from the conventional HB/XB lies in the electrostatic interaction, which is not increasingly repulsive as anions gradually approach to each other. Rather, there is a Coulombic barrier at a certain point. After this point, the electrostatic repulsion diminishes with the decreasing distance between anions. Differently, other energy components vary monotonically just like in conventional cases. The nonmonotonic characteristic of the electrostatic interaction in interanion complexes was reproduced using the multipole expansion in AMOEBA polarizable force field in which the state-specified atomic multipoles were adopted. This suggests that the nonmonotonicity can be well interpreted by classical electrostatic theory and there is no conceptual difference between conventional HB/XB and IAHB/IAXB. The stability of IAHB/IAXB depends on the competition between the local attractive HB/XB and the global Coulombic repulsion of net charges, though there is cooperativity between these two contrasting forces. This concise model was supported by the attractive IAHB/IAXB in modified molecular capsules, which exhibit strong quadruple HB/XBs and a considerable distance between charged substituents.

Different effects of lysophosphatidic acid on L-type calcium current in neonatal rat ventricular myocytes with and without H2O2 treatment.

L-type calcium current (I(Ca-L)) alterations are implicated in various cardiac diseases, and the lysophosphatidic acid (LPA) level increases in several ischemic heart diseases. We investigated the effects of LPA on I(Ca-L) in normal and H2O2-treated neonatal rat ventricular myocytes. LPA treatment (24h) increased the action potential duration (APD) and I(Ca-L) in normal ventricular myocytes, but it decreased these parameters in H2O2-treated myocytes. LPA increased the single-channel open probability of L-type calcium channels in both normal and H2O2-treated myocytes. LPA activated calcineurin (CaN) and induced the cytoplasm-to-nucleus translocation of nuclear factor of activated T-cells (NFAT) in H2O2-treated cardiomyocytes. In H2O2-treated cardiomyocytes, LPA decreased Ca(v)1.2 mRNA and protein expression levels at 4 and 8h, respectively. A CaN inhibitor (FK-506) prevented LPA-induced APD, I(Ca-L), and Ca(v)1.2 mRNA and protein down-regulation. The LPA-induced I(Ca-L) increase in normal cardiomyocytes was CaN-NFAT signaling-independent, and LPA did not affect Ca(v)1.2 mRNA or protein expression. In conclusion, LPA increases the I(Ca-L) in normal ventricular myocytes by increasing the single-channel open probability of L-type calcium channels, and LPA decreases I(Ca-L) in H2O2-treated cardiomyocytes via the CaN-NFAT pathway.