Heating Rate-Dependent Dehydrogenation in the Thermal Decomposition Process of Mg(BH₄)₂·6NH₃

The detailed mechanism of thermal decomposition of Mg­(BH₄)₂·6NH₃ synthesized via a mechanochemical reaction between Mg­(BH₄)₂ and NH₃ at room temperature was investigated for the first time. A six-step decomposition process, which involves several parallel and interrelated reactions, was elucidated through a series of structural examinations and property evaluations. First, the thermal decomposition of Mg­(BH₄)₂·6NH₃ evolves 3 equiv of NH₃ and forms Mg­(BH₄)₂·3NH₃. Subsequently, Mg­(BH₄)₂·3NH₃ decomposes to release an additional 1 equiv of NH₃ and 3 equiv of H₂ to produce the [MgNBHNH₃]­[BH₄] polymer. And then, [MgNBHNH₃]­[BH₄] further desorbs 3 equiv of H₂ through a three-step reaction to give rise to the formation of the polymer intermediates of [MgNBHNH₂]­[BH₄], MgNBHNH₂BH₂, and MgNBNHBH, respectively. Finally, an additional 1 equiv of H₂ is liberated from MgNBNHBH to yield Mg and BN as the resultant solid products. In total, about 7 equiv of H₂ and 4 equiv of NH₃ are released together from Mg­(BH₄)₂·6NH₃ upon heating. Moreover, there is a strong dependence of the gas compositions released from Mg­(BH₄)₂·6NH₃ on the heating rate because the decomposition reaction of Mg­(BH₄)₂·3NH₃ is sensitive to the heating rate, as the faster heating rate induces a lower ammonia evolution. The finding in this work provides us with insights into the dehydrogenation mechanisms of the metal borohydride ammoniates as hydrogen storage media

Cocaine and gp120 induced phosphorylation of MAPKs.

<p>Western blot analysis of time-dependent activation of ERK, JNK and p38 kinases in astrocytes treated with cocaine and gp120. Representative immunoblots are presented from 4 separate experiments.</p

Effects of cocaine and/or gp120 on mitochondrial membrane potential in rat astrocytes.

<p>(A) Cells treated with cocaine and/or gp120 for 18 h were assayed for mitochondrial membrane potential by staining with JC-1 dye. Treatment with cocaine/gp120 resulted in reduction of the aggregation of JC-1 dye in the mitochondria (red fluorescence) and decreased ratio of the aggregate (red fluorescence) to monomer JC-1 (green fluorescence) in the cells. Scale bars indicate 200 µm. (B) Quantification of Δψm expressed as a ratio of J-aggregate to JC-1 monomer (red∶ green) fluorescence intensity. All the data are presented as mean±SD of three individual experiments. ** p<0.01; ***p<0.001 versus control group; #p< 0.05 versus cocaine group; ∧p< 0.05 versus gp120 group.</p

NF-κB is involved in cocaine and gp120-induced astrocyte apoptosis.

<p>(A) Rat primary astrocytes grown on coverslips were treated with cocaine (10 µM) and/or gp120 IIIB (200 ng/ml) for 15 min and stained with an anti-NF-κB p65 antibody, followed by treatment with an Alexa Flour 488-conjugated secondary antibody. Slides were mounted in Slow Fade antifade reagent (with DAPI, blue nuclear stain) and images were captured by fluorescence microscope. Scale bars indicate 20 µm. (B) Western Blot analysis of nuclear extracts from cocaine and gp120-treated cells for varying times (5 to 60 min) using an antibody specific for p65 subunit of NF-κB. Representative immunoblot and the densitometric analysis of p NF-κB/histone from three separate experiments is presented. All the data in these figures are presented as mean±SD of three individual experiments. *<i>p</i><0.05 versus control group. (C) Inhibition of NF-κB using the specific inhibitor TPCK (10 µM) resulted in abrogation of cocaine and gp120 toxicity. **p<0.01 versus control group. # p<0.05 versus cocaine + gp120 group.</p

Effects of cocaine and/or gp120 exposure on caspase-3 activation in rat primary astrocytes.

<p>(A) Rat primary astrocytes treated with cocaine (10 µM) and/or gp120 IIIB (200 ng/ml) for 24 h were monitored for active caspase-3 by immunostaining using anti-cleaved caspase-3 antibody. Scale bars indicate 20 µm. (B) Rat primary astrocytes were treated with cocaine and/or gp120 for 24 h, followed by cell lysis and detection of anti-cleaved caspase-3 protein on a Western blot. (C) Densitometry scans of the ratio of band intensities of cleaved caspase-3/β-actin from three separate experiments. * p<0.05 versus control group; # p< 0.05 versus cocaine group; ∧p< 0.05 versus gp120 group.</p

Effects of cocaine and/or gp120 on intercellular ROS production in rat astrocytes.

<p>(A) Cells treated with cocaine in the absence or presence of gp120 for 1 h were assessed for production of ROS using DCFH-DA assay. Treatment of astrocytes with cocaine and/or gp120 resulted in increased ROS production. Scale bars indicate 200 µm. (B) Quantification of ROS fluorescence intensity in cells treated with gp120 and/or cocaine using fluorescence plate reader. All the data are presented as mean ± SD of four individual experiments. ** p<0.01; ***p<0.001 versus control group; ## p< 0.01 versus cocaine group; ∧∧ p< 0.01 versus gp120 group.</p

Effects of cocaine and/or gp120 on cell viability in rat primary astrocytes.

<p>(A) Effects of 1, 10, 100 µM cocaine in the presence or absence of gp120 IIIB (200 ng/ml) for 48 h on the survival of rat primary astrocytes using the MTT assay. (B) Effects of gp120 IIIB, heated inactivated gp120 IIIB and gp120 Bal (200 ng/ml) on the survival of rat primary astrocytes using the MTT assay. All the data are presented as mean ± SD of four individual experiments. *<i>p</i><0.05; **<i>p</i><0.01; ***p<0.001 versus control group; # p< 0.05 versus cocaine group; ∧ <i>p</i>< 0.05 versus gp120 group.</p

Inflammatory Cell Infiltration (ICI).

<p>Inflammatory Cell Infiltration (ICI).</p

Immunohistochemical expression of DSP.

<p>(A): Representative immunohistochemical images of the blank control group, the Ca(OH)₂ group, and the DBM group. a: The blank control group. Pulp morphology was normal. b- f: Ca(OH)₂ group (1, 3, 7, 14, 28 days). g- k: DBM group (1, 3, 7, 14, 28 days). (B): Mean IOD value of DSP. *means significant differences.</p

Results of the histopathological evaluation.

<p>ICI: Inflammatory cell infiltration, PTD: Pulp tissue disorganization, RDF: Reparative dentin formation.</p