Catalytic dehydrogenation of propane over a Pt-based catalyst to propylene has received considerable interests in recent years because this route is able to provide an economical and efficient way to fill the gap between supply and demand in propylene market. The low dispersion of a Pt particle at the support surface and sintering of Pt nanoparticles under the harsh reaction condition are the main challenges in the practical application of this catalyst. Herein, highly efficient Pt/Sn-Beta catalysts are developed for propane dehydrogenation, which exhibits high activity, selectivity, and stability in this reaction. Full characterizations with XRD, STEM, XPS, CO-IR, H2-TPR, and Py-IR techniques on these catalysts reveal that the Pt clusters are localized at the Sn single-site in the zeolitic framework, which allows the generated Pt clusters to be homogeneously dispersed at the surface zeolite. The high performance of Pt/Sn-Beta catalysts under a high reaction temperature is mainly due to a strong interaction between the Pt cluster and Sn-zeolite. An initial propane conversion of 50%, high propylene selectivity of above 99%, low deactivation rate of 0.006 h–1, high TOF of 114 s–1, and good regenerability have been achieved in the Pt-Sn2.00/Sn-Beta catalyst for propane dehydrogenation at 570 °C.

Metallic 1T-phase transition metal dichalcogenides (TMDs) are of considerable interest in enhancing catalytic applications due to their abundant active sites and good conductivity. However, the unstable nature of 1T-phase TMDs greatly impedes their practical applications. Herein, we developed a new approach for the synthesis of highly stable 1T-phase Au/Pd-MoS2 nanosheets (NSs) through a metal assembly induced ultrastable phase transition for achieving a very high electrocatalytic activity in the hydrogen evolution reaction. The phase transition was evoked by a novel mechanism of lattice-mismatch-induced strain based on density functional theory (DFT) calculations. Raman spectroscopy and transmission electron microscopy (TEM) were used to confirm the phase transition on experimental grounds. A novel heterostructured 1T MoS2–Au/Pd catalyst was designed and synthesized using this mechanism, and the catalyst exhibited a 0 mV onset potential in the hydrogen evolution reaction under light illumination. Therefore, this method can potentially be used to fabricate 1T-phase TMDs with remarkably enhanced activities for different applications.

The transfer of ubiquitin (Ub) to a substrate protein requires a cascade of E1 activating, E2 conjugating, and E3 ligating enzymes. E3 Ub ligases containing U-box and RING domains bind both E2ϳUb conjugates and substrates to facilitate transfer of the Ub molecule. Although the overall mode of action of E3 ligases is well established, many of the mechanistic details that determine the outcome of ubiquitination are poorly understood. CHIP (carboxyl terminus of Hsc70-interacting protein) is a U-box E3 ligase that serves as a co-chaperone to heat shock proteins and is critical for the regulation of unfolded proteins in the cytosol. We have performed a systematic analysis of the interactions of CHIP with E2 conjugating enzymes and found that only a subset bind and function. Moreover, some E2 enzymes function in pairs to create products that neither create individually. Characterization of the products of these reactions showed that different E2 enzymes produce different ubiquitination products, i.e. that E2 determines the outcome of Ub transfer. Site-directed mutagenesis on the E2 enzymes Ube2D1 and Ube2L3 (UbcH5a and UbcH7) established that an SPA motif in loop 7 of E2 is required for binding to CHIP but is not sufficient for activation of the E2ϳUb conjugate and consequent ubiquitination activity. These data support the proposal that the E2 SPA motif provides specificity for binding to CHIP, whereas activation of the E2ϳUb conjugate is derived from other molecular determinants.Ubiquitination is a key post-translational modification most commonly associated with protein turnover via degradation in the 26 S proteasome but is also involved in the regulation of gene expression, protein activation, and localization (1, 2). To modify a substrate, ubiquitin (Ub) 2 is covalently attached to a lysine through its C-terminal glycine by the sequential action of a cascade of three enzymes. The E1 ubiquitin-activating enzyme uses ATP to generate a thioester bond to Ub and then hands off the Ub to an E2 ubiquitin-conjugating enzyme via thioester bond transfer, a process known as charging the E2 enzyme. In the final step, the E3 ubiquitin ligase catalyzes ligation of Ub to the substrate. U-box-and RING-type E3 ligases act as scaffolds to bring together the E2ϳUb conjugate and the substrate. These E3 enzymes also play a critically important role in activating the E2ϳUb conjugate, which is otherwise unable to efficiently transfer Ub to a substrate. Creation of polyubiquitin chains is thought to occur by multiple cycles of E2 charging and cycling through the E3-substrate complex. Recent evidence has shown that polyubiquitination may result from the action of combinations of E2 and E3 enzymes with separate initiation and elongation functions (3-8). The location, length, and linkage of ubiquitination are all important parts of the signal resulting from ubiquitin attachment.Consistent with the diversity of functional roles, there are numerous potential products that result from protein ubiquitination. Although the basic mechanisms of ub...

Nanocarbon-supported Pt nanoparticles (NPs) were prepared and tested for the propane dehydrogenation reaction (PDH). The nanocarbon support is composed of a nanodiamond core and a defective, ultrathin graphene nanoshell (ND@G). The Pt/ND@G catalyst experienced slight deactivation during the 100 h PDH test, while the Pt/Al 2 O 3 catalyst showed severe deactivation after the 20 h PDH test. Pt NPs exhibited superior sintering resistance versus that of the ND@G support. This particular support structure of ND@G allows electrons on the defects to transfer to the Pt NPs, leading to a strong metal−support interaction, which significantly prevents Pt NP sintering and promotes the desorption of electron-rich propylene. This electron transfer mechanism was also confirmed by a CO catalytic oxidation test.