bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cooperative Bimetallic Catalysis via One‐Metal/Two‐Ligands: Mechanistic Insights of Polyfluoroarylation‐Allylation of Diazo Compounds
Authors: Wang Gao‐Yin , Ge Zhaoliang , Ding Kuiling , Wang Xiaoming 
Published: June 2023

AbstractMetal/ligand in situ assembly is crucial for tailoring the reactivity & selectivity in transition metal catalysis. Cooperative catalysis via a single metal/two ligands is still underdeveloped, since it is rather challenging to harness the distinct reactivity profiles of the species generated by self‐assembly of a single metal precursor with a mixture of different ligands. Herein, we report a catalytic system composed of a single metal/two ligands for a three‐component reaction of polyfluoroarene, α‐diazo ester, and allylic electrophile, leading to highly efficient construction of densely functionalized quaternary carbon centers, that are otherwise hardly accessible. Mechanistic studies suggest this reaction follows a cooperative bimetallic pathway via two catalysts with distinct reactivity profiles, which are assembled in situ from a single metal precursor and two ligands and work in concert to escort the transformation.
Copper‐Catalyzed Regiodivergent Internal Allylic Alkylations
Authors: Manna Madhu Sudan , Yoo Seok Yeol , Sharique Mohammed , Choi Hyoju , Pudasaini Bimal , Baik Mu‐Hyun , Tambar Uttam K. 
Published: June 2023

AbstractWe report a copper‐catalyzed, regioselective, and stereospecific alkylation of unbiased internal allylic carbonates with functionalized alkyl and aryl Grignard reagents. The reactions exhibit high stereospecificity and regioselectivity for either SN2 or SN2′ products under two sets of copper‐catalyzed conditions, which enables the preparation of a broad range of products with E‐alkene selectivity. Density functional theory calculations reveal the origins of the regioselectivity based on the different behaviors of homo‐ and heterocuprates.
Mechanistic Understanding of Efficient Polyethylene Hydrocracking over Two‐Dimensional Platinum‐Anchored Tungsten Trioxide
Authors: Zhou Qimin , Wang Deliang , Wang Qingyue , He Kailin , Lim Khak Ho , Yang Xuan , Wang Wen‐Jun , Li Bo‐Geng , Liu Pingwei 
Published: June 2023

AbstractChemical upcycling of polyethylene (PE) can convert plastic waste into valuable resources. However, engineering a catalyst that allows PE decomposition at low temperatures with high activity remains a significant challenge. Herein, we anchored 0.2 wt.% platinum (Pt) on defective two‐dimensional tungsten trioxide (2D WO3) nanosheets and achieved hydrocracking of high‐density polyethylene (HDPE) waste at 200–250 °C with a liquid fuel (C5–18) formation rate up to 1456 gproducts ⋅ gmetal species−1 ⋅ h−1. The reaction pathway over the bifunctional 2D Pt/WO3 is elucidated by quasi‐operando transmission infrared spectroscopy, where (I) well‐dispersed Pt immobilized on 2D WO3 nanosheets trigger the dissociation of hydrogen; (II) adsorption of PE and activation of C−C cleavage on WO3 are through the formation of C=O/C=C intermediates; (III) intermediates are converted to alkane products by the dissociated H. Our study directly illustrates the synergistic role of bifunctional Pt/WO3 catalyst in the hydrocracking of HDPE, paving the way for the development of high‐performance catalysts with optimized chemical and morphological properties.
Functional Characterization and Cyclization Mechanism of a Diterpene Synthase Catalyzing the Skeleton Formation of Cephalotane‐Type Diterpenoids
Authors: Li Changkang , Wang Shuai , Yin Xinxin , Guo Aobo , Xie Kebo , Chen Dawei , Sui Songyang , Han Yaotian , Liu Jimei , Chen Ridao , Dai Jungui 
Published: June 2023

AbstractCsCTS, a new diterpene synthase from Cephalotaxus sinensis responsible for forming cephalotene, the core skeleton of cephalotane‐type diterpenoids with a highly rigid 6/6/5/7 tetracyclic ring system, was functionally characterized. The stepwise cyclization mechanism is proposed mainly based on structural investigation of its derailment products, and further demonstrated through isotopic labeling experiments and density functional theory calculations. Homology modeling and molecular dynamics simulation combined with site‐directed mutagenesis revealed the critical amino acid residues for the unique carbocation‐driven cascade cyclization mechanism of CsCTS. Altogether, this study reports the discovery of the diterpene synthase that catalyzes the first committed step of cephalotane‐type diterpenoid biosynthesis and delineates its cyclization mechanism, laying the foundation to decipher and artificially construct the complete biosynthetic pathway of this type diterpenoids.
Divergent Stabilities of Tetravalent Cerium, Uranium, and Neptunium Imidophosphorane Complexes**
Authors: Otte Kaitlyn S. , Niklas Julie E. , Studvick Chad M. , Boggiano Andrew C. , Bacsa John , Popov Ivan A. , La Pierre Henry S. 
Published: June 2023

AbstractThe study of the redox chemistry of mid‐actinides (U−Pu) has historically relied on cerium as a model, due to the accessibility of trivalent and tetravalent oxidation states for these ions. Recently, dramatic shifts of lanthanide 4+/3+ non‐aqueous redox couples have been established within a homoleptic imidophosphorane ligand framework. Herein we extend the chemistry of the imidophosphorane ligand (NPC=[N=PtBu(pyrr)2]−; pyrr=pyrrolidinyl) to tetrahomoleptic NPC complexes of neptunium and cerium (1‐M, 2‐M, M=Np, Ce) and present comparative structural, electrochemical, and theoretical studies of these complexes. Large cathodic shifts in the M4+/3+ (M=Ce, U, Np) couples underpin the stabilization of higher metal oxidation states owing to the strongly donating nature of the NPC ligands, providing access to the U5+/4+, U6+/5+, and to an unprecedented, well‐behaved Np5+/4+ redox couple. The differences in the chemical redox properties of the U vs. Ce and Np complexes are rationalized based on their redox potentials, degree of structural rearrangement upon reduction/oxidation, relative molecular orbital energies, and orbital composition analyses employing density functional theory.
Stereoselective Synthesis of the O‐antigen of A. baumannii ATCC 17961 Using Long‐Range Levulinoyl Group Participation
Authors: Duan Liangshen , Nie Qin , Hu Yongxin , Wang Liming , Guo Kaiyan , Zhou Zhuoyi , Song Xu , Tu Yuanhong , Liu Hui , Hansen Thomas , Sun Jian‐song , Zhang Qingju 
Published: June 2023

AbstractHerein, we described the first synthesis of the pentasaccharide and decasaccharide of the A. baumannii ATCC 17961 O‐antigen for developing a synthetic carbohydrate‐based vaccine against A. baumannii infection. The efficient synthesis of the rare sugar 2,3‐diacetamido‐glucuronate was achieved using our recently introduced organocatalytic glycosylation method. We found, for the first time, that long‐range levulinoyl group participation via a hydrogen bond can result in a significantly improved β‐selectivity in glycosylations. This solves the stereoselectivity problem of highly branched galactose acceptors. The proposed mechanism was supported by control experiments and DFT computations. Benefiting from the long‐range levulinoyl group participation strategy, the pentasaccharide donor and acceptor were obtained via an efficient [2+1+2] one‐pot glycosylation method and were used for the target decasaccharide synthesis.
Synthesis and properties of a new polycarboxylic acid multi‐polymer scale inhibitor suitable for industrial circulating water
Authors: Xiao Yulun , Ren Dajun , Zhai Junlin , Wang Zhaobo , Zhang Le , Xie Junfeng , Li Yajing , Zhang Shuqin , Zhang Xiaoqing , Gong Xiangyi , Chen Wangsheng 
Published: June 2023

AbstractMultipolymer TPEG‐IA‐AMPS was synthesized by free‐radical polymerization using isopentenol polyoxyethylene ether (TPEG), itaconic acid (IA) and 2‐acrylamide‐2‐methylpropanesulfonic acid (AMPS) as monomers. In addition, the monomers and the synthesized multipolymer were characterized and analyzed by infrared spectroscopy (FTIR), hydrogen nuclear magnetic resonance (1H‐NMR) and gel permeation chromatography (GPC). And then, the control variable method and static scale inhibition method were used to measure the influence of different synthesis conditions on the calcium carbonate scale inhibition performance of multipolymer, and the optimum synthesis conditions of terpolymer were determined. Meanwhile, the influence of different factors on the scale inhibition performance of calcium carbonate scale and calcium sulfate scale under the optimum synthesis conditions was also explored. Moreover, scanning electron microscope (SEM) and x‐ray diffraction (XRD) were used to analyze the scale inhibition mechanism. The results show that the synthesized multipolymer TPEG‐IA‐AMPS is suitable for industrial recycling wastewater in harsh environment such as high alkalinity, high hardness and high PH.
Sustainable self‐curing epoxy adhesives from Chios natural Mastic (Pistacia lentiscus L.)
Authors: Anastasiou Dimitrios E. , Patsidis Anastasios C. , Andreopoulou Aikaterini K. 
Published: June 2023

AbstractThis study outlines a method for the epoxidation of poly‐beta‐myrcene, a biopolymer that can be easily extracted from the natural resin of the Chios Mastic tree (Pistacia lentiscus L.). The resulting epoxidation products are self‐curing, and have a nearly 100% green carbon content. These Mastic Epoxide products (MASTEP) have the potential to be useful thermosetting resins. One specific product (MASTEP A), was used as an adhesive to create Single Lap Joints, which were then subjected to tensile shear stress tests. MASTEP A was found to be 25%–83% stronger than three commonly used conventional or “semi‐green” epoxy adhesives. Another specific product (MASTEP B), was found able to be thermally converted into a semi‐crystalline form. In order to clarify the 3D chemical structure of MASTEP, IR, and DSC investigations were conducted. The entire production process was designed to be environmentally friendly. The results of this research represent a significant advancement in the development of environmentally friendly epoxies and pave the way to a wide range of potential further research.
Adipose tissue‐derived mesenchymal stem cells ameliorate cognitive impairment in Alzheimer's disease rat model: Emerging role ofSIRT1
Authors: Nabil Mohamed , Kassem Dina H. , Ali Azza A. , El‐Mesallamy Hala O. 
Published: June 2023

AbstractAlzheimer's disease (AD) is a complex form of neurodegenerative dementia. Growing body of evidence supports the cardinal role of sirtuin1 (SIRT1) in neurodegeneration and AD development. Recently, adipose tissue‐derived mesenchymal stem cells (Ad‐MSCs) have made their mark for a wide array of regenerative medicine applications, including neurodegenerative disorders. Therefore, the present study aimed to investigate the therapeutic potential of Ad‐MSCs in AD rat model, and to explore the possible implication of SIRT1. Ad‐MSCs were isolated from rat epididymal fat pads and properly characterized. Aluminum chloride was used to induce AD in rats, and afterward, a group of AD‐induced rats received a single dose of Ad‐MSCs (2 × 106cell, I.V per rat). One month after Ad‐MSCs transplantation, behavioral tests were done, brain tissues were collected, then histopathological and biochemical assessments were performed. Amyloid beta and SIRT1 levels were determined by enzyme‐linked immunosorbent assay. Whereas expression levels of neprilysin, BCL2 associated X protein,B‐cell lymphoma‐2,interleukin‐1β,interleukin‐6,and nerve growth factor in hippocampus and frontal cortex brain tissues were assessed using reverse transcriptase quantitative polymerase chain reaction. Our data demonstrated that transplantation of Ad‐MSCs alleviated cognitive impairment in AD rats. Additionally, they exhibited anti‐amyloidogenic, antiapoptotic, anti‐inflammatory, as well as neurogenic effects. Furthermore, Ad‐MSCs were found to possibly mediate their therapeutic effects, at least partially, via modulating both central and systemic SIRT1 levels. Hence, the current study portrays Ad‐MSCs as an effective therapeutic approach for AD management and opens the door for future investigations to further elucidate the role of SIRT1 and its interrelated molecular mediators in AD.
A phase II study of perioperative pembrolizumab plus mFOLFOX in patients with potentially resectable esophagus, gastroesophageal junction (GEJ), and stomach adenocarcinoma
Authors: Sun Weijing , Veeramachaneni Nirmal , Al‐Rajabi Raed , Madan Rashna , Kasi Anup , Al‐Kasspooles Mazin , Baranda Joaquina , Saeed Anwaar , Phadnis Milind A. , Godwin Andrew K. , Olyaee Mojtaba , Streeter Natalie , Nagji Alykhan , Dai Junqiang , Williamson Stephen 
Published: June 2023

AbstractBackgroundPerioperative chemotherapy/chemoradiation is standard in esophageal/gastric/gastroesophageal junction (GEJ) adenocarcinoma, immune checkpoint inhibitors (ICI) effect in setting of metastatic and postoperatively. This study is to assess ICI + chemotherapy perioperatively.MethodsPatients with locally advanced (T1N1‐3M0 or T2‐3NanyM0) potentially resectable esophageal/gastric/GEJ adenocarcinoma by PET/EUS/CT and staging‐laparoscopy, were treated preoperative 4 cycles mFOLFOX6 (Oxaliplatin 85 mg/m2/Leucovorin 400 mg/m2/5‐FU bolus 400 mg/m2 then infusion 2400 mg/m2 for 46 h q2weeks) and 3 cycles pembrolizumab (200 mg q3week). Those without distal disease post‐neoadjuvant and eligible for resection underwent surgery. Postoperative treatment was initiated at 4–8 weeks with 4 cycles mFOLFOX and 12 cycles pembrolizumab. The primary objective is pathological response (ypRR with tumor regression score, TRS ≤2). The expression of ICI‐related markers PD‐L1 (CPS), CD8, and CD20 were analyzed before and after preoperative therapy.ResultsThirty‐seven patients completed the preoperative treatment. Twenty‐nine patients had curative R0 resection. 6/29 (21%; 95% CI: 0.08–0.40) achieved ypCR with TRS 0 in resected patients. 26/29 (90%; 95% CI: 0.73–0.98) had ypRR with TRS ≤2. Twenty‐six patients finished adjuvant therapy with a median 36.3‐month follow‐up. Three patients had recurrence/metastatic disease (at 9‐, 10‐, 22 months enrollment) with one dead at 23 months, and two are still alive at 28 and 36.5 months. The remaining (23/26) are free of disease with 3 years DFS of 88.5% and 3 years OS of 92.3%. There were no unexpected toxicities. Preoperative ICI + chemotherapy enhanced immune responses significantly with increasing expression of PD‐L1 (CPS ≥10, p = 0.0078) and CD8 (>5%, p = 0.0059).ConclusionsThe perioperative pembrolizumab and mFOLFOX combination in resectable esophageal/gastric/GEJ adenocarcinoma is very effective with 90% ypRR, 21% ypCR, and impressive long‐time survival benefits.
Genomic characterization between HER2‐positive and negative gastric cancer patients in a prospective trial
Authors: Hu Qingjiang , Oki Eiji , Yamada Teppei , Kashiwada Tomomi , Sonoda Hideto , Kataoka Masato , Kawanaka Hirofumi , Tsuji Yasushi , Makiyama Akitaka , Nakashima Yuichiro , Ota Mitsuhiko , Kimura Yasue , Yoshizumi Tomoharu 
Published: June 2023

AbstractBackgroundWe aimed to clarify the genomic characteristics of HER2‐positive and negative gastric cancer cases that potentially affect tumor progression and treatment response in a prospective trial.MethodsWe collected 80 formalin‐fixed paraffin‐embedded (FFPE) samples (49 HER2+ and 31 HER2‐) from gastric cancer patients who participated in the TROX‐A1 trial (UMIN000036865). We queried a 435‐gene panel (CANCERPLEX‐JP) to generate comprehensive genomic profiling data, including the tumor mutation burden, somatic mutations, and copy number variations. In addition, the genomic differences between HER2+ and HER2‐ gastric cancer patients were analyzed.ResultsMutational analyses showed that TP53 was the most frequently mutated gene regardless of HER2 status. ARID1A mutation was significantly enriched in HER2‐negative patients. The number of total mutations in HER2‐negative patients with ARID1A mutation was remarkably higher than that in HER2‐positive patients. Next, copy number variation analyses showed that the number of amplified genes (such as CCNE1, PGAP3, and CDK12) in HER2‐positive cases was significantly higher than that in HER2‐negative cases. Moreover, PTEN deletion was more common in HER2‐positive cases. Finally, we found that, compared with HER2‐positive patients, HER2‐negative patients tended to have a higher tumor mutation burden, particularly in patients with ARID1A mutation. Pathway analyses of the gene alterations showed an enrichment of several immune‐related pathways in HER2‐negative patients.ConclusionsAccording to the genomic profiling of HER2‐positive and negative gastric cancer, several gene alterations in the HER2 pathway may be the potential mechanism underlying trastuzumab resistance. Relative to HER2‐positive gastric cancer, HER2‐negative gastric tumors with ARID1A mutation may be sensitive to immune checkpoint inhibitors.
A Meta‐Analysis of Catalytic Hydrogenation of Levulinic Acid to γ‐Valerolactone
Authors: Niaze Ambereen Aziz , Dhaker Deepa , Upadhyayula Sreedevi 
Published: June 2023

AbstractSelective hydrogenation of biomass‐derived levulinic acid (LA) to γ‐valerolactone (GVL) is an important reaction in biomass upgradation to produce valuable fuels and chemicals. Increasing demand for renewable energy sources has stipulated growth in catalytic research and has generated a massive amount of experimental data over the years. Inside this numerous data, fresh insights into property‐performance associations can be found. However, the incomplete existence and unclear structure of these data records have hampered systematic information extraction thus far. This research proposes a meta‐analysis approach for identifying associations between the physico‐chemical properties of a catalyst and its reaction performance. The approach combines data from literature with insights from textbooks and statistical methods. A hypothesis is formulated based on a researcher's intuition and statistical significance is checked against the data. Repetitive hypothesis refining gives robust, clear, and analyzable chemical models. The results can be used to guide future research and catalyst production. The method for catalytic hydrogenation of LA to GVL is shown and validated here.
Nucleobase and Linker Modification for Triple‐Helical Recognition of Pyrimidines in RNA Using Peptide Nucleic Acids
Authors: Kumpina Ilze , Baskevics Vladislavs , Nguyen Khoi D. , Katkevics Martins , Rozners Eriks 
Published: June 2023

AbstractTriple‐helical recognition of any sequence of double‐stranded RNA requires high affinity Hoogsteen hydrogen binding to pyrimidine interruptions of polypurine tracts. Because pyrimidines have only one hydrogen bond donor/acceptor on Hoogsteen face, their triple‐helical recognition is a formidable problem. The present study explored various five‐membered heterocycles and linkers that connect nucleobases to backbone of peptide nucleic acid (PNA) to optimize formation of X•C‐G and Y•U‐A triplets. Molecular modeling and biophysical (UV melting and isothermal titration calorimetry) results revealed a complex interplay between the heterocyclic nucleobase and linker to PNA backbone. While the five‐membered heterocycles did not improve pyrimidine recognition, increasing the linker length by four atoms provided promising gains in binding affinity and selectivity. The results suggest that further optimization of heterocyclic bases with extended linkers to PNA backbone may be a promising approach to triple‐helical recognition of RNA.
Astragaloside II enhanced sensitivity of ovarian cancer cells to cisplatin via triggering apoptosis and autophagy
Authors: Zhang Lijia , Liu Ye , Lei Xue , Liu Xiaowai , Sun Heng , Liu Songjiang 
Published: June 2023

AbstractCisplatin (DDP) based chemotherapy occurs a reduced therapeutic effect on the later treatment of ovarian cancer (OC) due to DDP resistance. Astragaloside II (ASII), a natural product extracted from Radix Astragali, has shown promising anticancer effects. However, the effects of ASII on OC have not been clarified. In this study, we found that ASII inhibited cell growth and promoted cell apoptosis of DDP‐resistant OC cells in vitro and in vivo. Further study showed that ASII downregulated multidrug resistance‐related protein MDR1 and cell cycle‐related protein Cyclin D1 and PCNA, and also upregulated apoptosis‐related protein leaved PRAP and cleaved caspase‐3. In addition, ASII induced autophagy, characterized by upregulation of LC3II expression, downregulation of p62 expression, and elevation of LC3 punctuation, may be associated with inhibition of the AKT/mTOR signaling pathway. Moreover, the messenger RNA‐sequencing was used to identify potential molecules regulated by ASII. In conclusion, these findings indicated that ASII increased sensitivity of DDP in the treatment of OC.
A Doubly Dissipative System Driven by Chemical and Radiative Stimuli
Authors: Valentini Matteo , Frateloreto Federico , Conti Matteo , Cacciapaglia Roberta , Del Giudice Daniele , Di Stefano Stefano 
Published: June 2023

AbstractThe operation of a dissipative network composed of two or three different crown‐ether receptors and an alkali metal cation can be temporally driven by the use (combined or not) of two orthogonal stimuli of a different nature. More specifically, irradiation with light at a proper wavelength and/or addition of an activated carboxylic acid, are used to modulate the binding capability of the above crown‐ethers towards the metal ion, allowing to control over time the occupancy of the metal cation in the crown‐ether moiety of a given ligand. Thus, application of either or both of the stimuli to an initially equilibrated system, where the metal cation is distributed among the crown‐ether receptors depending on the different affinities, causes a programmable change in the receptor occupancies. Consequently, the system is induced to evolve to one or more out‐of‐equilibrium states with different distributions of the metal cation among the different receptors. When the fuel is exhausted or/and the irradiation interrupted, the system reversibly and autonomously goes back to the initial equilibrium state. Such results may contribute to the achievement of new dissipative systems that, taking advantage of multiple and orthogonal stimuli, are featured with more sophisticated operating mechanisms and time programmability.
Photoelectron Photoion Coincidence Spectroscopy of Biradicals
Authors: Fischer Ingo , Hemberger Patrick 
Published: June 2023

AbstractThe electronic structure of biradicals is characterized by the presence of two unpaired electrons in degenerate or near‐degenerate molecular orbitals. In particular, some of the most relevant species are highly reactive, difficult to generate cleanly and can only be studied in the gas phase or in matrices. Unveiling their electronic structure is, however, of paramount interest to understand their chemistry. Photoelectron photoion coincidence (PEPICO) spectroscopy is an excellent approach to explore the electronic states of biradicals, because it enables a direct correlation between the detected ions and electrons. This permits to extract unique vibrationally resolved photoion mass‐selected threshold photoelectron spectra (ms‐TPES) to obtain insight in the electronic structure of both the neutral and the cation. In this review we highlight most recent advances on the spectroscopy of biradicals and biradicaloids, utilizing PEPICO spectroscopy and vacuum ultraviolet (VUV) synchrotron radiation.