110th Anniversary: Near-Total Epoxidation Selectivity and Hydrogen Peroxide Utilization with Nb-EISA Catalysts for Propylene Epoxidation

The Nb-EISA catalyst with relatively low Nb loadings (∼2 wt %) shows exceptional propylene epoxidation performance with H2O2 as oxidant at 30–40 °C, 5–9 bar propylene pressure with nearly total propylene oxide (PO) selectivity (>99%), H2O2 utilization (>99%) toward PO formation, high productivity (∼3200 mg/h/g), and mild Nb leaching (3–6%). The predominantly Lewis acidic nature of the Nb-EISA catalysts favors epoxidation while their relatively low Brønsted acidity inhibits H2O2 decomposition and Nb leaching. At higher Nb loadings (8–17 wt %), the catalytic performance deteriorates. However, significant performance improvements were achieved when the Nb-EISA materials are calcined in N2 (instead of air) during synthesis, depositing a carbon layer in the pores. The resulting pore hydrophobicity not only inhibits epoxide ring opening but also increases propylene concentration inside the pores resulting in higher EO productivity and lower H2O2 decomposition. The carbonized Nb-EISA materials also show improved stability to leaching

Formation of a gold-carbon dot nanocomposite with superior catalytic ability for the reduction of aromatic nitro groups in water

We report the synthesis of a gold-carbon dot nanocomposite and its utility as a recyclable catalyst for the reduction of aromatic nitro groups. The presence of carbon dots on gold nanosurfaces enhanced the reduction rate by two-fold

Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition)

In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. For example, a key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process versus those that measure fl ux through the autophagy pathway (i.e., the complete process including the amount and rate of cargo sequestered and degraded). In particular, a block in macroautophagy that results in autophagosome accumulation must be differentiated from stimuli that increase autophagic activity, defi ned as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (inmost higher eukaryotes and some protists such as Dictyostelium ) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the fi eld understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. It is worth emphasizing here that lysosomal digestion is a stage of autophagy and evaluating its competence is a crucial part of the evaluation of autophagic flux, or complete autophagy. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. Along these lines, because of the potential for pleiotropic effects due to blocking autophagy through genetic manipulation it is imperative to delete or knock down more than one autophagy-related gene. In addition, some individual Atg proteins, or groups of proteins, are involved in other cellular pathways so not all Atg proteins can be used as a specific marker for an autophagic process. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field

Synthesis and catalytic epoxidation potential of oxodiperoxo molybdenum (VI) complexes with 2-hydroxybenzohydroxamate and 2-hydroxybenzoate: the crystal structure of PPh4 [MoO (O2) 2 (HBA)]

info:eu-repo/semantics/publishe

Divergent route to the preparation of hybrid Pt–Fe 2,4,6-Tris(4-ethynyl)phenyl-1,3,5-triazine metallodendrimers for nonlinear optics

The synthesis strategy for the preparation of novel platinum acetylide homometallic and heterobimetallic dendrimers (containing Fe as the other metal fragment) based on a 2,4,6-tris(4-ethynyl)phenyl-1,3,5-triazine core (3) is reported. All the dendrimer generations (G0−G2) were synthesized under copper-free conditions following a divergent route. The G0-Pt dendrimer (4) was synthesized using the 1,3,5-triazine core (3) and cis[Pt(PEt3)2Cl2] with a molar ratio of 1/4. The advantage of the current method is that different dendrimers can be prepared by following the same procedure with only changes in the molar ratios of the reactants involved. For instance, when 3 reacts with 4 in a 4/1 molar ratio, the G1 dendrimer 7 is afforded without the peripheral Pt moiety, but the G1 dendrimer with the peripheral Pt moiety (8) is formed when 3 reacts with 4 in a 1/3 molar ratio. On the other hand, the G2 dendrimer with a peripheral Pt moiety (9) is synthesized when 7 reacts with 4 in a 1/6 molar ratio. The heterobimetallic dendrimers were synthesized up to generation 1 by capping the corresponding Pt dendrimers with the ethynylferrocenyl group (EFC). The respective G0 (6)- and G1-capped (10) dendrimers were synthesized when EFC reacted with 4 and 8 in molar ratios of 9/1 and 18/1, respectively. Nonlinear optical (NLO) polarizabilities measured by hyper-Rayleigh scattering (HRS) have been evaluated for the core 3, for the G0 dendrimer 4, and for the G0 dendrimer capped with EFC (6). In spite of the fact that the stability of the higher generations in chloroform is too low to allow HRS measurements, the reported NLO results show a remarkable enhancement (plus 50%) upon capping the zero dendrimer generation (6), reflecting the importance of the introduction of electron donor organometallic capping groups in the hyperpolarizabilities of the resulting dendrimers.info:eu-repo/semantics/publishedVersio

Oxo- and oxoperoxo-molybdenum(VI) complexes with aryl hydroxamates: synthesis, structure, and catalytic uses in highly efficient, selective, and ecologically benign peroxidic epoxidation of olefins

A solution obtained by dissolving MoO<SUB>3</SUB> in H<SUB>2</SUB>O<SUB>2</SUB> reacts separately with secondary hydroxamic acids (viz., N-benzoyl N-phenyl hydroxamic acid (BPHAH), N-benzoyl N-ortho-, -meta-, -para-tolyl hydroxamic acids, (BOTHAH, BMTHAH, and BPTHAH, respectively), and N-cinnamoyl N-phenyl hydroxamic acid (CPHAH) affording [MoO(O<SUB>2</SUB>)(BPHA)<SUB>2</SUB>] (1), [MoO(O<SUB>2</SUB>)(BOTHA)<SUB>2</SUB>] (2), [MoO(O<SUB>2</SUB>)(BMTHA)<SUB>2</SUB>] (3), [MoO(O<SUB>2</SUB>)(BPTHA)<SUB>2</SUB>] (4), and [Mo(O)<SUB>2</SUB>(CPHA)<SUB>2</SUB>] (5), respectively. The O and O<SUB>2</SUB> are situated cis to each other in 2-4, but in each case, they are disordered and distributed over four sites. This disorder does not exist in the 6-coordinate cis dioxo complex 5, to which crude MoO(O<SUB>2</SUB>)(CPHA)<SUB>2</SUB> (5') was converted during recrystallization. An aqueous molybdate solution readily reacts with all those hydroxamic acids producing [Mo(O)<SUB>2</SUB>(hydroxamate)<SUB>2</SUB>] (6). While 2, 3, and 4 possess a very distorted pentagonal bipyramidal structure, 5 has a distorted octahedral geometry. In the solid state, as well as in solution, 5 exists as two apparently enantiomerically related molecules differing in the orientation of the pendant phenyl rings. To emphasize that the formation and structural uniqueness of 5 compared to 1-4 is caused by the influence of the cinnamoyl residue, one compound of the 6 series, namely, [Mo(O)<SUB>2</SUB>(BPHA)<SUB>2</SUB>] (6A), was structurally characterized to prove directly that the special stereochemical properties of 5 rely on the special electronic structure of CPHA- ligand. Complexes 1-5, as well as 6, show high potential and selectivity as catalysts in the epoxidation of olefins at room temperature in the presence of NaHCO<SUB>3</SUB> as a promoter and H<SUB>2</SUB>O<SUB>2</SUB> as a terminal oxidant. A comparative epoxidation study has been performed to determine the relative efficiency of the catalysts. To make the epoxidation method cost effective, a study to optimize the use of H<SUB>2</SUB>O<SUB>2</SUB> has also been performed. To obtain evidence in favor of our suggested mechanism to this homogeneous olefin → epoxide conversion, it was necessary to synthesize a peroxo-rich compound, namely, [MoO(O<SUB>2</SUB>)<SUB>2</SUB>BMTHA]<SUP>−</SUP> (7), but the attempted synthesis culminated in the isolation of [MoO(O<SUB>2</SUB>)<SUB>2</SUB>(C<SUB>6</SUB>H<SUB>5</SUB>COO)]<SUP>−</SUP> (8), obviously, via the hydrolysis of coordinated BMTHA

Divergent Route to the Preparation of Hybrid Pt–Fe 2,4,6-Tris(4-ethynyl)phenyl-1,3,5-triazine Metallodendrimers for Nonlinear Optics

The synthesis strategy for the preparation of novel platinum acetylide homometallic and heterobimetallic dendrimers (containing Fe as the other metal fragment) based on a 2,4,6-tris­(4-ethynyl)­phenyl-1,3,5-triazine core (<b>3</b>) is reported. All the dendrimer generations (G0–G2) were synthesized under copper-free conditions following a divergent route. The G0-Pt dendrimer (<b>4</b>) was synthesized using the 1,3,5-triazine core (<b>3</b>) and <i>cis</i>-[Pt­(PEt₃)₂Cl₂] with a molar ratio of 1/4. The advantage of the current method is that different dendrimers can be prepared by following the same procedure with only changes in the molar ratios of the reactants involved. For instance, when <b>3</b> reacts with <b>4</b> in a 4/1 molar ratio, the G1 dendrimer <b>7</b> is afforded without the peripheral Pt moiety, but the G1 dendrimer with the peripheral Pt moiety (<b>8</b>) is formed when <b>3</b> reacts with <b>4</b> in a 1/3 molar ratio. On the other hand, the G2 dendrimer with a peripheral Pt moiety (<b>9</b>) is synthesized when <b>7</b> reacts with <b>4</b> in a 1/6 molar ratio. The heterobimetallic dendrimers were synthesized up to generation 1 by capping the corresponding Pt dendrimers with the ethynylferrocenyl group (EFC). The respective G0 (<b>6</b>)- and G1-capped (<b>10</b>) dendrimers were synthesized when EFC reacted with <b>4</b> and <b>8</b> in molar ratios of 9/1 and 18/1, respectively. Nonlinear optical (NLO) polarizabilities measured by hyper-Rayleigh scattering (HRS) have been evaluated for the core <b>3</b>, for the G0 dendrimer <b>4</b>, and for the G0 dendrimer capped with EFC (<b>6</b>). In spite of the fact that the stability of the higher generations in chloroform is too low to allow HRS measurements, the reported NLO results show a remarkable enhancement (plus 50%) upon capping the zero dendrimer generation (<b>6</b>), reflecting the importance of the introduction of electron donor organometallic capping groups in the hyperpolarizabilities of the resulting dendrimers

Antidiabetic, Antioxidant and Antihyperlipidemic Status of Heliotropium zeylanicum Extract on Streptozotocin-Induced Diabetes in Rats

The potential role of the methanolic extract of Heliotropium zeylanicum (BURM.F) LAMK (MEHZ) in the treatment of diabetes along with its antioxidant and antihyperlipidemic effects was studied in streptozotocin-induced diabetic rats. Oral administration of (MEHZ) 150 and 300 mg/kg/d for 14 d significantly decreased the blood glucose level and considerably increased the body weight, food intake, and liquid intake of diabetic-induced rats. MEHZ significantly decreased thiobarbituric acid reactive substances and significantly increased reduced glutathione, superoxide dismutase and catalase in streptozotocin-induced diabetic rats at the end of 14 d of treatment. The study also investigated the antihyperlipidemic potential of MEHZ. The results show that the active fraction of MEHZ is promising for development of a standardized phytomedicine for the treatment of diabetes mellitus