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Narrowly distributed polyethylene-b-poly(ethylene oxide) diblock copolymers (PE-b-PEO) with a linear PE block were successfully synthesized by combination of click coupling reaction of azido-terminated polyethylene (PE−N3) and alkynyl-terminated poly(ethylene oxide) (PEO−CONHCH2CCH). PE−N3 derived from tosylation and subsequent substitution by sodium azide of hydroxyl-terminated PE (PE−OH) which was prepared by means of chain shuttling ethylene polymerization with 2,6-bis[1-(2,6- dimethylphenyl)imino ethyl] pyridine iron (II) dichloride (complex 1)/methylaluminoxane (MAO)/diethyl zinc (ZnEt2) and subsequent in situ oxidation with oxygen. PEO−CONHCH2CCH was synthesized through esterification the hydroxyl end-group on hydroxyl-terminated PEO (PEO−OH) with phosgene and subsequent amidation by propargyl amine. The self-assembly of three double-crystalline PE-b-PEO samples with different block length in water were investigated by laser light scattering (LLS) and transmission electron microscopy (TEM). It was found that, in water, a solvent selectively good for the PEO block, PE-b-PEO chains with proper PE block length could form spherical multicores micelles with the insoluble and crystallized PE blocks as the multicores and the soluble and swollen PEO blocks as the shell. These multicores in one micelle could reaggregate to a single-core as temperature increased. Differential scanning calorimetry (DSC) experiments showed that the crystallization of both PE and PEO blocks was intensely confined by the previously self-assembled structure of PE-b-PEO in aqueous solution.

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Diends-azido-terminated and diends-alkynyl-terminated poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) triblock copolymers (N 3 -PEO-b-PPO-b-PEO-N 3 and HCtC-PEO-b-PPO-b-PEO-CtCH) were respectively prepared and used together as the precursors for multiblock copolymer synthesis through coupling reaction by combination of self-assembly and click chemistry. The self-assembly of equimolar resultant triblock copolymers in water, a selective solvent for PEO, results in a core-shell structure with the insoluble and collapsed PPO blocks as the core and the soluble and swollen PEO blocks as the shell. The self-assembly concentrates and exposes the azido and alkynyl end groups on the periphery. The multiple click coupling reactions between the self-assembled diends-functionalized triblock copolymers were performed, leading to the highly efficient formation of -(-PEO-b-PPO-b-PEO-) nmultiblock copolymer chains. In comparison, the click coupling reaction was also presented in N,N-dimethylformamide (DMF) solution without self-assembly. It was found that the efficiency of the coupling reaction was very low, and no long multiblock copolymer chains were produced.

Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the etiologic agent of COVID-19, enters human cells using the angiotensin-converting enzyme 2 (ACE2) protein as a receptor. ACE2 is thus key to the infection and treatment of the coronavirus. ACE2 is highly expressed in the heart, respiratory and gastrointestinal tracts, playing important regulatory roles in the cardiovascular and other biologic systems. However, the genetic basis of the ACE2 protein levels is not well understood. Methods: We conduct so far the largest genome-wide association meta-analysis of plasma ACE2 levels in over 28,000 individuals of the SCALLOP Consortium. We summarize the cross-sectional epidemiologic correlates of circulating ACE2. Using the summary-statistics-based high-definition likelihood method, we estimate relevant genetic correlations with cardiometabolic phenotypes, COVID-19, and other human complex traits and diseases. We perform causal inference of soluble ACE2 on vascular disease outcomes and COVID-19 disease severity using Mendelian randomization. We also perform in silico functional analysis by integrating with other types of omics data. Results: We identified ten loci, including eight novel, capturing 30% of the protein's heritability. We detected that plasma ACE2 was genetically correlated with vascular diseases, severe COVID-19, and a wide range of human complex diseases and medications. An X-chromosome cis-pQTL-based Mendelian randomization analysis suggested a causal effect of elevated ACE2 levels on COVID-19 severity (odds ratio (OR), 1.63; 95% CI, 1.10 to 2.42; P = 0.01), hospitalization (OR, 1.52; 95% CI, 1.05 to 2.21; P = 0.03), and infection (OR, 1.60; 95% CI, 1.08 to 2.37; P = 0.02). Tissue- and cell-type-specific transcriptomic and epigenomic analysis revealed that the ACE2 regulatory variants were enriched for DNA methylation sites in blood immune cells. Conclusions: Human plasma ACE2 shares a genetic basis with cardiovascular disease, COVID-19, and other related diseases. The genetic architecture of the ACE2 protein is mapped, providing a useful resource for further biological and clinical studies on this coronavirus receptor.

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Objectives: This study aimed to explore efficacy and safety between LAMSs (lumen-apposing metal stents) and DPPSs (double-pigtail plastic stents) in endoscopic ultrasound-guided drainage for pancreatic fluid collections.Methods: Electronic databases were searched to identify relevant studies published until July 20, 2020.Results: Fifteen studies were identified in this study. Endoscopic ultrasoundguided drainage with LAMS has higher clinical success (90.01% vs 82.56%) (odds ratio [OR], 2.44; 95% confidence interval [CI], 1.79-3.33; P < 0.00001), less recurrence (OR, 0.44; 95% CI, 0.29-0.68; P = 0.0002), and fewer additional interventions (OR, 0.34; 95% CI, 0.211-0.55; P < 0.001). There was no significant difference between LAMS and DPPS in technical success (97.45% vs 97.38%) (OR, 0.92; 95% CI, 0.50-1.70; P = 0.80), adverse events (OR, 0.92; 95% CI, 0.41-2.09; P = 0.84), stent-related adverse events (OR, 0.78; 95% CI, 0.39-1.54; P = 0.47), and bleeding (OR, 1.47; 95% CI, 0.57-3.28; P = 0.42). Lumen-apposing metal stents have slightly more perforations (OR, 7.10; 95% CI, 1.22-41.30; P = 0.03) in studies of walled-off necrosis.Conclusions: Lumen-apposing metal stents have the advantage of higher clinical success, less recurrence, and fewer additional interventions. However, LAMS may increase perforation for walled-off necrosis.

In this study, we examined various alkylaluminums, including triethylaluminum (TEA), triisobutylaluminum (TIBA), and diethylaluminum chloride (DEAC), as cocatalysts for the activation of ethylene polymerizations in the presence of a fluorinated Fujita group invented titanium (FI-Ti) catalyst, bis[N-(3-tert-butylsalicylidene)-2,3,4,5,6-pentafluoroanilinato] titanium(IV) dichloride (complex 1). DEAC, because of the strong Lewis acidity, was an efficient cocatalyst for activating complex 1 for the ethylene polymerizations, whereas TEA and TIBA as cocatalysts could hardly polymerize ethylene. The effects of the polymerization temperature and Al/Ti molar ratio on the formation of active species, properties, and molecular weight of the resulting polyethylene were investigated. In the complex 1/ DEAC catalyst system, the oxidation states of Ti active species were determined by electron paramagnetic resonance. The results demonstrated that Ti(IV) active species were inclined to polymerize ethylene and yielded high-molecular-weight polyethylene. Comparatively, Ti(III) active species resulted from the reduction of Ti(IV) by DEAC and afforded oligomers. Moreover, the bigger steric bulk for the cocatalysts was necessary to achieve ethylene living polymerization with the fluorinated FI-Ti catalyst.