Stereoselective Synthesis of Tetrasubstituted Olefins via Visible-Light-Promoted Iodine-Mediated Homo-Coupling of Diazo.

A visible-light-promoted iodine-mediated homo-coupling of diazo was first described. A series of tetrasubstituted olefins were synthesized in high yields and with low to high Z-selectivities from phenyldiazoacetates. For 3-diazooxindoles, isoindigo derivatives were provided in moderate to high yields and with excellent E-selectivities. Experimental results showed that the reaction proceeded through a diiodo intermediate. The synthetic usefulness of this reaction was illustrated by the synthesis of maleimide derivatives and dispiro epoxy.

G-quadruplex binder pyridostatin as an effective multi-target ZIKV inhibitor.

At present, there are still no anti-Zika virus (ZIKV) drugs or vaccines approved by FDA with accurate targets and antiviral mechanisms. Considering the RNA G-quadruplex sequences in ZIKV genome, it is very meaningful to develop G-quadruplex binders as potential anti-ZIKV drugs with novel and accurate targets. In this paper, five classical G-quadruplex binders including Ber, Braco 19, NiL, 360A and PDS have been chosen to discuss their interaction with ZIKV RNA G-quadruplexes. PDS shows higher binding affinity and thermal stability than the other G-quadruplex binders. This property is further evidenced in cells by immunofluorescence microscopy. And PDS shows higher anti-ZIKV activity (EC50 = 4.2 ± 0.4 µM) than the other G-quadruplex binders as well as the positive control ribavirin, with a low cytotoxicity. By time-of-addition assay, PDS exerts antiviral activity at the post-entry process of ZIKV replication cycle, thus inhibiting ZIKV mRNA replication and protein expression. Furthermore, PDS combines with ZIKV NS2B-NS3 protease and reduces its catalytic activity. This study suggests that G-quadruplex binder PDS is an effective multi-target ZIKV inhibitor, which provides more guidance to design some novel anti-ZIKV drugs targeting ZIKV RNA G-quadruplexes.

Potent Neutralizing Antibodies Elicited by RBD-Fc-Based COVID-19 Vaccine Candidate Adjuvanted by the Th2-Skewing iNKT Cell Agonist.

The development of a safe and effective COVID-19 vaccine is of paramount importance to terminate the current pandemic. An adjuvant is crucial for improving the efficacy of the subunit COVID19 vaccine. α-Galactosylceramide (αGC) is a classical iNKT cell agonist which causes the rapid production of Th1- and Th2-associated cytokines; we, therefore, expect that the Th1- or Th2-skewing analogues of αGC can better enhance the immunogenicity of the receptor-binding domain in the spike protein of SARS-CoV-2 fused with the Fc region of human IgG (RBD-Fc). Herein, we developed a universal synthetic route to the Th1-biasing (α-C-GC) and Th2-biasing (OCH and C20:2) analogues. Immunization of mice demonstrated that αGC-adjuvanted RBD-Fc elicited a more potent humoral response than that observed with Alum and enabled the sparing of antigens. Remarkably, at a low dose of the RBD-Fc protein (2 µg), the Th2-biasing agonist C20:2 induced a significantly higher titer of the neutralizing antibody than that of Alum.

Comparative transcriptome analysis of the hyperaccumulator plant Phytolacca americana in response to cadmium stress.

To study the molecular mechanism of the hyperaccumulator plant Phytolacca americana against cadmium (Cd) stress, the leaves of P. americana treated with 400 µM Cd for 0, 2, 12, and 24 h were harvested for comparative transcriptome analysis. In total, 110.07 Gb of clean data were obtained, and 63,957 unigenes were acquired after being assembled. Due to the lack of P. americana genome information, only 24,517 unigenes were annotated by public databases. After Cd treatment, 5054 differentially expressed genes (DEGs) were identified. KEGG pathway enrichment analysis of DEGs showed that genes involved in the flavonoid biosynthesis and antenna proteins of photosynthesis were significantly down-regulated, while genes related to the lignin biosynthesis pathway were remarkably up-regulated, indicating that P. americana could synthesize more lignin to cope with Cd stress. Moreover, genes related to heavy metal accumulation, sulfur metabolism and glutathione metabolism were also significantly up-regulated. The gene expression pattern of several key genes related to distinct metabolic pathways was verified by qRT-PCR. The results indicated that the immobilization of lignin in cell wall, chelation, vacuolar compartmentalization, as well as the increase of thiol compounds content may be the important mechanisms of Cd detoxification in hyperaccumulator plant P. americana. Accession numbers: the raw data of P. americana transcriptome presented in this study are openly available in NCBI SRA database, under the BioProject of PRJNA649785. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13205-021-02865-x.

Human telomere double G-quadruplex recognition by berberine-bisquinolinium imaging conjugates in vitro and cells.

Molecular tools of double or multimeric G-quadruplexes have been given higher requirements on detection sensitivity, thermal stabilization and cell imaging to establish functions of these G-quadruplex aggregates and biological mechanisms as anticancer reagents. Here, two smart berberine-bisquinolinium conjugates (Ber-360A and Ber-PDS) by linking the berberine fluorophore ligand and an established G-quadruplex binder (i.e. bisquinolinium scaffold), have been designed and evaluated their activities and mechanisms for G-quadruplex aggregation. Two conjugates, especially Ber-PDS, are two highly selective, sensitive and fluorescent sensors which can distinguish human telomere double G-quadruplexes from other type G-quadruplexes and ds DNA. These two ligands could be the first example to stack two adjacent G-quadruplex units and fluorescently recognize human telomere double G-quadruplexes. Furthermore, conjugate Ber-PDS could enter the nucleoli and target G-quadruplex DNA through microscopy experiments, and also display strong telomerase inhibition and antitumor activities.

Dimers formed with the mixed-type G-quadruplex binder pyridostatin specifically recognize human telomere G-quadruplex dimers.

By choosing pyridostatin (PDS) with high thermal stabilization towards mixed-type G-quadruplexes as the monomer in dimers, three novel polyether-tethered PDS dimers (1a-c) were first synthesized and their interaction with human telomere G-quadruplex dimers (G2T1) was studied. Through the regulation of the linker length in PDS dimers, the dimer with a medium-length polyether linker (1b) showed higher binding selectivity and thermal stabilization (ΔTm = 29.5 °C) towards antiparallel G2T1 over G-quadruplex monomers (G1). Furthermore, the dimer with the longest-length polyether linker (1c) showed higher binding selectivity and thermal stabilization towards mixed-type G2T1 over mixed-type G1, c-kit 1, c-kit 2, c-myc and ds DNA. This work provides new insights into the development of G2T1 binders, especially mixed-type G2T1 binders, which could be promoted by a polymer formed with a mixed-type G-quadruplex binder. In addition, dimer 1c exhibited stronger telomerase inhibition than dimers 1a and 1b.

Genomic characterization and pathogenicity of porcine deltacoronavirus strain CHN-HG-2017 from China.

Porcine deltacoronavirus (PDCoV) was first detected in Hong Kong and has recently spread to many countries around the world. PDCoV causes acute diarrhea and vomiting in pigs, resulting in significant economic losses in the global pork industry. In this study, a Chinese PDCoV strain, designated CHN-HG-2017, was isolated from feces of a suckling piglet with severe watery diarrhea on a farm located in central China. Subsequently, the virus was identified by an indirect immunofluorescence assay and electron microscopy. A nucleotide sequence alignment showed that the whole genome of CHN-HG-2017 is 97.6%-99.1% identical to other PDCoV strains. Analysis of potential recombination sites showed that CHN-HG-2017 is a possible recombinant originating from the strains CH/SXD1/2015 and Vietnam/HaNoi6/2015. Furthermore, the pathogenicity of this recombinant PDCoV strain was investigated in 5-day-old piglets by oral inoculation. The challenged piglets developed typical symptoms, such as vomiting, anorexia, diarrhea and lethargy, from 1 to 7 days post-inoculation (DPI). Viral shedding was detected in rectal swabs until 14 DPI in the challenged piglets. Interestingly, high titers of virus-neutralizing antibodies in sera were detected at 21 DPI. Tissues of small intestines from CHN-HG-2017-infected piglets at 4 DPI displayed significant macroscopic and microscopic lesions with clear viral antigen expression. Our analysis of the full genome sequence of a recombinant PDCoV and its virulence in suckling piglets might provide new insights into the pathogenesis of PDCoV and facilitate further investigation of this newly emerged pathogen.

Highly efficient anion transport mediated by 1,3-bis(benzimidazol-2-yl)benzene derivatives bearing electron-withdrawing substituents.

1,3-Bis(benzimidazol-2-yl)benzene exhibits potent anionophoric activity through a process of anion exchange with a minor level of proton/anion symport. Modification of 1,3-bis(benzimidazol-2-yl)benzene with strong electron-withdrawing substituents, such as trifluoromethyl and nitro groups, leads to up to 789-fold increase in the activity. The benzimidazolyl-NH fragments, the relative position and the number of the benzimidazolyl groups on the central phenyl scaffold play an essential role in the transport.

Two new furostanol saponins from the fibrous root of Ophiopogon japonicus.

Two new furostanol saponins ophiopogonins J (1) and K (2) were isolated from the fibrous roots of Ophiopogon japonicus. The structures of 1 and 2 were established as (25R)-26-O-[(ß-D-glucopyranosyl-(1 --> 2)-ß-D-glucopyranosyl)]-14-hydroxy-furost-5,20(22)-diene 3-O-[α-L-rhamnopyranosyl-(1 --> 2)]-ß-D-glucopyranoside (1), and (25R)-26-O-[(ß-D-glucopyranosyl-(1 --> 2)-ß-D-glucopyranosyl)]-furost-5,20(22)-diene 3-O-α-L-rhamnopyranosyl-(1 --> 2)[(ß-D-xylopyranosyl-(1 --> 4)-ß-D-glucopyranoside)] (2) on the basis of spectroscopic means including HRESIMS, 1D, and 2D NMR experiments.