Electronic Structure of Gold Carbonyl Compounds RAuL (R = CF₃, BO, Br, Cl, CH₃, HCC, Mes₃P, SIDipp; L = CO, N₂, BO) and Origins of Aurophilic Interactions in the Clusters [RAuL]_<i>n</i> (<i>n</i> = 2–4): A Theoretical Study

The bonding nature of CF₃AuCO and its clusters [CF₃AuCO]_<i>n</i> (<i>n</i> = 2–4) (Angew. Chem., Int. Ed. 2011, 50, 6571) have been theoretically investigated with density functional theory (B3LYP, B3LYP-D3, M06-2X, M06-2X-D3, M05-2X, M06L, B3PW91), the Hartree–Fock method (HF), second-order Møller–Plesset perturbation theory (MP2), and the coupled cluster method with perturbative triplets (CCSD­(T)) using a series of basis sets. For comparison, larger complexes that have been studied experimentally, [Mes₃PAuCO]⁺ and [SIDippAuCO]⁺, were also computed. Various ligands as well as their gold clusters [RAuL]_2–4 (R = OB, Br, Cl, CH₃, HCC; L = CO, N₂, OB) were also investigated. The Au–CO bonds consist of electrostatic attraction, Au←CO donation, and Au→CO π-back-bonding components. The LMOEDA results show that the major contributors of RAuL are found to be electrostatic, which linearly correlates with the interaction energy. Electrostatic stabilization is mainly responsible for aurophilic interactions in the formation of CF₃AuCO clusters

Panels A and B show expression of the EP4 receptor in adult mouse ventricular myocytes (AVM) and neonatal rat ventricular myocytes (NVM), respectively, as determined by RT-PCR.

<p>Neg ctl is the negative control lane. Note that the PCR product sizes are different in panel A and panel B because different primer sets were used for the two different species. Panel C shows expression of the fractalkine receptor (Cx3CR1) in adult mouse fibroblasts (AVF) and myocytes (AVM) and panel D shows expression of the fractalkine receptor in cultured neonatal rat ventricular fibroblasts (NVF) at passage two and in primary cultures of neonatal rat ventricular myocytes (NVM). Expression of the fractalkine receptor was also determined by RT-PCR.</p

Echocardiography of Male EP4 KO Mice and Wild Type Littermates.

<p><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0069832#pone-0069832-t001" target="_blank">Table 1</a> gives echocardiography data for male EP4 KO mice and their wild-type littermates (WT) that were used to determine fractalkine content of the left ventricle by ELISA. Values are means ± SE.</p>*<p>p<0.05,</p>**<p>p≤0.01 versus WT. Statistical analysis was performed using t-test. Abbreviations: SF, shortening fraction; EF, ejection fraction; LVDs, left ventricular dimension at systole; LVDd, left ventricular dimension at diastole; HR, heart rate; PWTd, posterior wall thickness at diastole; IVSTd, intraventricular septum thickness at diastole.</p

Effect of 5 ng/ml fractalkine on phosphorylation of cardiac troponin I.

<p>Panel A shows a representative Western blot of phosphorylated cardiac troponin I (upper panel) and total troponin I after treatment of AVM with vehicle (veh), isoproterenol (Iso), fractalkine (fract) or isoproterenol+fractalkine. N = 4 separate experiments. Statistical significance: *p<0.05 compared to vehicle treatment, +p<0.05 compared to isoproterenol treatment.</p

Scheme showing the proposed relationship between PGE₂, fractalkine and decreased contractility.

<p>We propose that PGE₂ acting on its EP4 receptor on cardiac fibroblasts increases fractalkine secretion. Fractalkine binds to its receptor (Cx3CR1) on cardiomyocytes thereby initiating a chain of events leading to decreased contractility. Also shown is the stimulation of fractalkine secretion from cardiomyocytes by hydrogen peroxide (reactive oxygen species, ROS), a mechanism that appears to be independent of PGE₂.</p

Panel A shows representative transients from vehicle and fractalkine-treated cells under isoproterenol-stimulated conditions.

<p>y-axis is the magnitude of cell shortening (contraction) in µm. Cells were paced at 3 Hz. Panels B and C show mean data for the effect of 5 ng/ml fractalkine on shortening velocity and lengthening velocity, respectively under isoproterenol-stimulated conditions. Statistical significance: *p<0.05 compared to cells treated with vehicle. N = 22–33 cells from 9 mice.</p

Effect of 5 ng/ml fractalkine on change in peak height from baseline (%) under isoproterenol-stimulated conditions (panel A) and change in intracellular calcium as indicated by a change in the Fura-2 ratio (panel B).

<p>Statistical significance: *p<0.05 compared to cells treated with vehicle.</p

Left ventricle (LV) fractalkine concentration in 28 week old male EP4 KO mice and WT controls.

<p>Values are corrected to ng fractalkine per mg LV weight. Fractalkine was determined by ELISA. *p<0.05.</p

Panel A shows representative transients of cells treated with either vehicle or 5 ng/ml fractalkine for 10 min.

<p>y-axis is the magnitude of cell shortening (contraction) in µm. Cells were paced at 3 Hz. Panels B and C show mean data for the effect of 5 ng/ml fractalkine on shortening velocity and lengthening velocity under basal conditions, respectively. Statistical significance: *p<0.05 compared to cells treated with vehicle. N = 22–33 cells from 9 mice.</p