Pb-activated Amine-assisted Photocatalytic Hydrogen Evolution Reaction on Organic-Inorganic Perovskites

We report here the reaction mechanism for explicit aqueous solvent quantum mechanics (QM) studies determining the energetics and reaction barriers for the photocatalytic hydrogen evolution reaction (HER) on CH_3NH_3PbI_3 surface. We find that both the lead (Pb) atoms and the surface organic molecules play essential roles, leading to a two-step Pb-activated amine-assisted (PbAAA) reaction mechanism involving an intermediate lead hydride state. Both H of H_2 product are extracted from surface organic molecules, while two protons from the solution migrate along water chains via the Grotthuss mechanism to replace the H in organic molecule. We obtain a reaction barrier of 1.08 eV for photochemical generation of H_2 on CH_3NH_3PbI_3 compared to 2.61 eV for the dark reaction. We expect this HER mechanism can also apply to the other organic perovskites, but the energy barriers and reaction rates may depend on the basicity of electrolyte and intrinsic structures of perovskites

Synthesis of ultra-narrow PbTe nanorods with extremely strong quantum confinement

Monodisperse, high-quality, ultra-narrow PbTe nanorods were synthesized for the first time in a one-pot, hot-injection reaction using trans-2-decenoic acid as the agents for lead precursors and tris(diethylamino)phosphine telluride together with free tris(diethylamino)phosphine as the telluride precursors. High monomer reactivity, rapid nucleation and fast growth rate derived from the new precursors led to the anisotropic growth of PbTe nanocrystals at low reaction temperatures

MFAP3L activation promotes colorectal cancer cell invasion and metastasis

AbstractAn abundance of microfibril-associated glycoprotein 3-like (MFAP3L) significantly correlates with distant metastasis in colorectal cancer (CRC), although the mechanism has yet to be explained. In this study, we observed that MFAP3L knock-down resulted in reduced CRC cell invasion and hepatic metastasis. We evaluated the cellular location and biochemical functions of MFAP3L and found that this protein was primarily localized in the nucleus of CRC cells and acted as a protein kinase. When EGFR translocated into the nucleus upon stimulation with EGF, MFAP3L was phosphorylated at Tyr287 within its SH2 motif, and the activated form of MFAP3L phosphorylated ERK2 at Thr185 and Tyr187. Moreover, the metastatic behavior of CRC cells in vitro and in vivo could be partially explained by activation of the nuclear ERK pathway through MFAP3L phosphorylation. Hence, we experimentally demonstrated for the first time that MFAP3L likely participates in the nuclear signaling of EGFR and ERK2 and acts as a novel nuclear kinase that impacts CRC metastasis

Spontaneous breaking and re-making of the RS-Au-SR staple in self-assembled ethylthiolate/Au(111) interface

The stability of the self-assembled RS–Au–SR (R = CH₂CH₃)/Au­(111) interface at room temperature has been investigated using scanning tunneling microscopy (STM) in conjunction with density functional theory (DFT) and MD calculations. The RS–Au–SR staple, also known as Au-adatom-dithiolate, assembles into staple rows along the [112̅] direction. STM imaging reveals that while the staple rows are able to maintain a static global structure, individual staples within the row are subjected to constant breaking and remaking of the Au–SR bond. The C₂S–Au–SC₂/Au­(111) interface is under a dynamic equilibrium and it is far from rigid. DFT/MD calculations show that a transient RS–Au–Au–SR complex can be formed when a free Au atom is added to the RS–Au–SR staple. The relatively high reactivity of the RS–Au–SR staple at room temperature could explain the reactivity of thiolate-protected Au nanoclusters, such as their ability to participate in ligand exchange and intercluster reactions

In Silico Optimization of Organic-Inorganic Hybrid Perovskites for Photocatalytic Hydrogen Evolution Reaction in Acidic Solution

We previously reported the atomistic reaction mechanism for the photocatalytic hydrogen evolution reaction (HER) on the CH_3NH_3PbI_3 organic–inorganic hybrid perovskites based on quantum mechanics calculations of the transition-state barriers, including several layers of explicit acidic solvent. Here, we extend these studies using in silico optimization to discover additional promising photocatalysts. We consider replacing (i) Pb with Sn, (ii) I with Br, and (iii) CH_3NH_3 cation with several organic cations, including NH_2(CH)NH_2 cation as the photocatalyst for HER. We compared the activation barriers and reaction energies for each case. In our previous studies, we found that both H atoms of the H_2 product are extracted from surface organic cations with protons from the solution migrating along Grotthuss water chains to replace the H of the organic cations. This two-step reaction mechanism involves formation of an intermediate lead hydride bond, with the lead atoms and the surface organic cations both playing essential roles. Among the perovskites investigated here, we predict that NH_2(CH)NH_2PbI_3 exhibits the best HER performance with a predicted 10-fold improvement in the reaction rate compared to CH_3NH_3PbI_3. We also suggest that the lead-free tin iodide perovskites might exhibit a rate comparable to that of lead iodide perovskites with the same organic cations. However, replacing iodine by bromine significantly increases the activation barrier. We find for these lead iodide perovskites, the increased proton affinity of the surface organic cations enhances the photocatalytic efficiency, with NH2(CH)NH2 the best case examined

Clinical significance of a point mutation in DNA polymerase beta (POLB) gene in gastric cancer.

Gastric cancer (GC) is a major cause of global cancer mortality. Genetic variations in DNA repair genes can modulate DNA repair capability and, consequently, have been associated with risk of developing cancer. We have previously identified a T to C point mutation at nucleotide 889 (T889C) in DNA polymerase beta (POLB) gene, a key enzyme involved in base excision repair in primary GCs. The purpose of this study was to evaluate the mutation and expression of POLB in a larger cohort and to identify possible prognostic roles of the POLB alterations in GC. Primary GC specimens and their matched normal adjacent tissues were collected at the time of surgery. DNA, RNA and protein samples were isolated from GC specimens and cell lines. Mutations were detected by PCR-RFLP/DHPLC and sequencing analysis. POLB gene expression was examined by RT-PCR, tissue microarray, Western blotting and immunofluorescence assays. The function of the mutation was evaluated by chemosensitivity, MTT, Transwell matrigel invasion and host cell reactivation assays. The T889C mutation was detected in 18 (10.17%) of 177 GC patients. And the T889C mutation was associated with POLB overexpression, lymph nodes metastases and poor tumor differentiation. In addition, patients with- the mutation had significantly shorter survival time than those without-, following postoperative chemotherapy. Furthermore, cell lines with T889C mutation in POLB gene were more resistant to the treatment of 5-fluorouracil, cisplatin and epirubicin than those with wild type POLB. Forced expression of POLB gene with T889C mutation resulted in enhanced cell proliferation, invasion and resistance to anticancer drugs, along with increased DNA repair capability. These results suggest that POLB gene with T889C mutation in surgically resected primary gastric tissues may be clinically useful for predicting responsiveness to chemotherapy in patients with GC. The POLB gene alteration may serve as a prognostic biomarker for GC

Clinical Significance of a Point Mutation in DNA Polymerase Beta (POLB) Gene in Gastric Cancer.

Gastric cancer (GC) is a major cause of global cancer mortality. Genetic variations in DNA repair genes can modulate DNA repair capability and, consequently, have been associated with risk of developing cancer. We have previously identified a T to C point mutation at nucleotide 889 (T889C) in DNA polymerase beta (POLB) gene, a key enzyme involved in base excision repair in primary GCs. The purpose of this study was to evaluate the mutation and expression of POLB in a larger cohort and to identify possible prognostic roles of the POLB alterations in GC. Primary GC specimens and their matched normal adjacent tissues were collected at the time of surgery. DNA, RNA and protein samples were isolated from GC specimens and cell lines. Mutations were detected by PCR-RFLP/DHPLC and sequencing analysis. POLB gene expression was examined by RT-PCR, tissue microarray, Western blotting and immunofluorescence assays. The function of the mutation was evaluated by chemosensitivity, MTT, Transwell matrigel invasion and host cell reactivation assays. The T889C mutation was detected in 18 (10.17%) of 177 GC patients. And the T889C mutation was associated with POLB overexpression, lymph nodes metastases and poor tumor differentiation. In addition, patients with- the mutation had significantly shorter survival time than those without-, following postoperative chemotherapy. Furthermore, cell lines with T889C mutation in POLB gene were more resistant to the treatment of 5-fluorouracil, cisplatin and epirubicin than those with wild type POLB. Forced expression of POLB gene with T889C mutation resulted in enhanced cell proliferation, invasion and resistance to anticancer drugs, along with increased DNA repair capability. These results suggest that POLBgene with T889C mutation in surgically resected primary gastric tissues may be clinically useful for predicting responsiveness to chemotherapy in patients with GC. The POLB gene alteration may serve as a prognostic biomarker for GC

Pb-activated Amine-assisted Photocatalytic Hydrogen Evolution Reaction on Organic-Inorganic Perovskites

We report here the reaction mechanism for explicit aqueous solvent quantum mechanics (QM) studies determining the energetics and reaction barriers for the photocatalytic hydrogen evolution reaction (HER) on CH_3NH_3PbI_3 surface. We find that both the lead (Pb) atoms and the surface organic molecules play essential roles, leading to a two-step Pb-activated amine-assisted (PbAAA) reaction mechanism involving an intermediate lead hydride state. Both H of H_2 product are extracted from surface organic molecules, while two protons from the solution migrate along water chains via the Grotthuss mechanism to replace the H in organic molecule. We obtain a reaction barrier of 1.08 eV for photochemical generation of H_2 on CH_3NH_3PbI_3 compared to 2.61 eV for the dark reaction. We expect this HER mechanism can also apply to the other organic perovskites, but the energy barriers and reaction rates may depend on the basicity of electrolyte and intrinsic structures of perovskites

In Silico Optimization of Organic-Inorganic Hybrid Perovskites for Photocatalytic Hydrogen Evolution Reaction in Acidic Solution

We previously reported the atomistic reaction mechanism for the photocatalytic hydrogen evolution reaction (HER) on the CH_3NH_3PbI_3 organic–inorganic hybrid perovskites based on quantum mechanics calculations of the transition-state barriers, including several layers of explicit acidic solvent. Here, we extend these studies using in silico optimization to discover additional promising photocatalysts. We consider replacing (i) Pb with Sn, (ii) I with Br, and (iii) CH_3NH_3 cation with several organic cations, including NH_2(CH)NH_2 cation as the photocatalyst for HER. We compared the activation barriers and reaction energies for each case. In our previous studies, we found that both H atoms of the H_2 product are extracted from surface organic cations with protons from the solution migrating along Grotthuss water chains to replace the H of the organic cations. This two-step reaction mechanism involves formation of an intermediate lead hydride bond, with the lead atoms and the surface organic cations both playing essential roles. Among the perovskites investigated here, we predict that NH_2(CH)NH_2PbI_3 exhibits the best HER performance with a predicted 10-fold improvement in the reaction rate compared to CH_3NH_3PbI_3. We also suggest that the lead-free tin iodide perovskites might exhibit a rate comparable to that of lead iodide perovskites with the same organic cations. However, replacing iodine by bromine significantly increases the activation barrier. We find for these lead iodide perovskites, the increased proton affinity of the surface organic cations enhances the photocatalytic efficiency, with NH2(CH)NH2 the best case examined

A Point Mutation in DNA Polymerase β (POLB) Gene Is Associated with Increased Progesterone Receptor (PR) Expression and Intraperitoneal Metastasis in Gastric Cancer

Increased expression of progesterone receptor (PR) has been reported in gastric cancer (GC). We have previously identified a functional T889C point mutation in DNA polymerase beta (POLB), a DNA repair gene in GC. To provide a detailed analysis of molecular changes associated with the mutation, human cDNA microarrays focusing on 18 signal transduction pathways were used to analyze differential gene expression profiles between GC tissues with T889C mutant in POLB gene and those with wild type. Among the differentially expressed genes, notably, PR was one of the significantly up-regulated genes in T889C mutant POLB tissues, which were subsequently confirmed in POLB gene transfected AGS cell line. Interestingly, patients with T889C mutation and PR positivity were associated with higher incidence of intraperitoneal metastasis (IM). In vitro studies indicate that PR expression was upregulated in AGS cell line when transfected with T889C mutant expression vector. Cotransfection of T889C mutant allele and PR gene induced cell migration in the cell line. These data demonstrated that T889C mutation-associated PR overexpression results in increased IM. Therefore, T889C mutation-associated PR overexpression may serve as a biomarker for an adverse prognosis for human GC