Homo‐C‐nucleoside analogs IV. Synthesis of 4‐(2,5‐anhydro‐D‐altro‐pentitol‐1‐yl)‐2‐phenyl‐2H‐1,2,3‐triazole homo‐C‐nucleoside. CD assignment of the absolute configuration of the carbon bridge

Dehydrative cyclization of 4‐(D‐altro ‐pentitol‐1‐yl)2‐phenyl‐2H ‐1,2,3‐triazole in basic medium with one moler equivalent of p‐toluene sulfonyl chloride in pyridine solution gave the homo‐C‐ nucleoside 4‐(2,5‐anhydro‐D‐altro ‐1‐yl)‐2‐phenyl‐2H ‐1,2,3‐triazole. The structure and anomeric configuration was determined by acylation, nuclear magnetic resonance (NMR), and mass spectroscopy. The stereochemistry at the carbon bridge of homo‐C‐ nucleoside 2‐phenyl‐2H ‐1,2,3‐triazoles was determined by circular dichroism (CD) spectroscopy.     

Novel 3‐Oxo‐ and 3,24‐Dinor‐2,4‐secooleanane‐Type Triterpenes from Terminalia ivorensis A. Chev.

Two new oleanane‐type triterpenes named ivorengenin A (=3‐oxo‐2α,19α,24‐trihydroxyolean‐12‐en‐28‐oic acid; 1 ) and ivorengenin B (=4‐oxo‐19α‐hydroxy‐3,24‐dinor‐2,4‐secoolean‐12‐ene‐2,28‐dioic acid; 2 ), together with five known compounds, arjungenin, arjunic acid, betulinic acid, sericic acid, and oleanolic acid, were isolated from the barks of Terminalia ivorensis A. Chev . (Combretaceae). Their structures were established on the basis of 1D‐ and 2D‐NMR data, and mass spectrometry. A biogenetic pathway to the formation of these compounds from sericic acid, isolated as the major compound from this plant, was proposed. The antioxidant activities of different compounds were investigated by means of the 2,2‐azinobis(3‐ethylbenzothiazoline‐6‐sulfonic acid) (ABTS) and 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) assays, and IC₅₀ values were calculated and compared with Trolox activity. Antiproliferative activities of the isolated compounds were also evaluated against MDA‐MB‐231, PC3, HCT116, and T98G human cancer cell lines, against which the compounds showed significant cytotoxic activities.     

Covid‐19.bioreproducibility.org: A web resource for SARS‐CoV‐2‐related structural models

The COVID‐19 pandemic has triggered numerous scientific activities aimed at understanding the SARS‐CoV‐2 virus and ultimately developing treatments. Structural biologists have already determined hundreds of experimental X‐ray, cryo‐EM, and NMR structures of proteins and nucleic acids related to this coronavirus, and this number is still growing. To help biomedical researchers, who may not necessarily be experts in structural biology, navigate through the flood of structural models, we have created an online resource, covid19.bioreproducibility.org, that aggregates expert‐verified information about SARS‐CoV‐2‐related macromolecular models. In this article, we describe this web resource along with the suite of tools and methodologies used for assessing the structures presented therein.     

Erratum: Ochnaflavone inhibits TNF‐α‐induced human VSMC proliferation via regulation of cell cycle,ERK1/2, and MMP‐9. S.‐J. Suh,U.‐H. Jin,S.‐H. Kim,H.‐W. Chang,J.‐K. Son,S.H. Lee,K.‐H. Son,C.‐H. Kim

During the corresponding author's transfer from Dongguk University to Sungkyunkwan University in March 2006, data from the previous University was transferred to the corresponding author's new computer. During this data transfer there was a mixing of EMSA data from experiments involving Quercetin (QC), Ochnaflavone (OC), Tanshinone (TS), Crytotanshinone (CT), BMK, and natural extracts. The mixed EMSA data was inadvertently incorporated in more than one publication. Figure 6 has been corrected to new data with re‐confirmation. J. Cell. Biochem. 108: 337, 2009. © 2009 Wiley‐Liss, Inc.

6. Effect of OC on the TNF‐α‐induced DNA binding activities of MMP‐9, NF‐κB, and AP‐1 motif in HASMC. Cells were pretreated with indicated OC for 40 min in serum‐free medium, were incubated with TNF‐α (100 ng/ml) for 24 h. Nuclear extracts were analyzed by EMSA for the activated NF‐κB (A) and AP‐1 (B) using radiolabeled oligonucleotide probes, respectively. Indicated values are means of three triplicate experiments.     

Complete structure determination of N‐acetyl‐D‐galactosamine‐binding mistletoe lectin‐3 from Viscum album L. album

The primary structure of the B chain of the N‐acetyl‐D ‐galactosamine‐recognizing mistletoe lectin‐3 (ML‐3B) has been deduced from proteolytic digest peptides of the purified glycoprotein, their HPLC‐separation and Edman degradation and confirmation of the peptide sequences by MALDI‐MS. ML‐3B consists of 262 amino acid residues including 10 cysteine moieties. The structure and linkage of the carbohydrate side chains, connected to two N‐glycosylation sites at positions Asn⁹⁵ and Asn¹³⁵ of the lectin, were determined by a combination of glycosidase treatment and MALDI‐MS of corresponding glycopeptide fragments. The sequence alignment reveals a high homology with other B chains of type‐II RIPs, although there are remarkable differences in the D ‐galactose‐specific mistletoe lectin‐1B chain. The recently published primary structure of the mistletoe lectin‐3A chain 1 and the now available primary sequence of the 3B chain allowed the construction of a preliminary homology model of ML‐3. The model demonstrates, unequivocally, that ML‐3 is a member of the type‐II RIP family with rigid conservation of the enzymatic active site of the A chain and an identical overall protein fold. Specific amino acid residue exchanges and the different glycosylation pattern in comparison with ML‐1 are discussed and related to the properties of the two glycoproteins. The knowledge of the complete primary structure of mistletoe lectin‐3 is a major contribution towards more insight into the mechanism of the biological activity of commercial mistletoe preparations. Copyright © 2004 European Peptide Society and John Wiley & Sons, Ltd.     

Crystal structures of halohydrin hydrogen‐halide‐lyases from Corynebacterium sp. N‐1074

Halohydrin hydrogen‐halide‐lyase (H‐Lyase) is a bacterial enzyme that is involved in the degradation of halohydrins. This enzyme catalyzes the intramolecular nucleophilic displacement of a halogen by a vicinal hydroxyl group in halohydrins to produce the corresponding epoxides. The epoxide products are subsequently hydrolyzed by an epoxide hydrolase, yielding the corresponding 1, 2‐diol. Until now, six different H‐Lyases have been studied. These H‐Lyases are grouped into three subtypes (A, B, and C) based on amino acid sequence similarities and exhibit different enantioselectivity. Corynebacterium sp. strain N‐1074 has two different isozymes of H‐Lyase, HheA (A‐type) and HheB (B‐type). We have determined their crystal structures to elucidate the differences in enantioselectivity among them. All three groups share a similar structure, including catalytic sites. The lack of enantioselectivity of HheA seems to be due to the relatively wide size of the substrate tunnel compared to that of other H‐Lyases. Among the B‐type H‐Lyases, HheB shows relatively high enantioselectivity compared to that of HheB_GP1. This difference seems to be due to amino acid replacements at the active site tunnel. The binding mode of 1, 3‐dicyano‐2‐propanol at the catalytic site in the crystal structure of the HheB‐DiCN complex suggests that the product should be (R)‐epichlorohydrin, which agrees with the enantioselectivity of HheB. Comparison with the structure of HheC provides a clue for the difference in their enantioselectivity. Proteins 2015; 83:2230–2239. © 2015 Wiley Periodicals, Inc.