The polar glycolipids were isolated from the thermophilic bacteria Meiothermus taiwanensis ATCC BAA‐400 by ethanol extraction and purified by Sephadex LH‐20 and silica gel column chromatography. The ...fatty acid composition of O‐acyl groups in the glycolipids was obtained by gas chromatography mass spectroscopy analysis on their methyl esters derived from methanolysis and was made mainly of C15:0 (34.0%) and C17:0 (42.3%) fatty acids, with the majority as branched fatty acids (over 80%). Removal of O‐acyl groups under mild basic conditions provided two glycolipids, which differ only in N‐acyl substitution on a hexosamine. Electrospray mass spectroscopy analysis revealed that one has a C17:0 N‐acyl group and the other hydroxy C17:0 in a ratio of about 1 : 3.5. Furthermore, complete de‐lipidation with strong base followed by selective N‐acetylation resulted in a homogeneous tetraglycosyl glycerol. The linkages and configurations of the carbohydrate moiety were then elucidated by MS and various NMR analyses. Thus, the major glycolipid from M. taiwanensis ATCC BAA‐400 was determined with the following structure: α‐Galp(1‐6)‐β‐Galp(1‐6)‐β‐GalNAcyl(1,2)‐α‐Glc(1,1)‐Gro diester, where N‐acyl is C17:0 or hydroxy C17:0 fatty acid and the glycerol esters were mainly iso‐ and anteisobranched C15:0 and C17:0.
The goal of this work is to study kinetics and quantitative structure‐activity relationships for steady states of Pseudomonas sp. lipase‐catalyzed hydrolysis of both diesters and monoesters of ...ethylene glycol. Based on the steady‐state kinetics of the enzyme‐catalyzed hydrolysis of the diesters of ethylene glycol, the diesters and the monoesters react simultaneously as soon as monoester has started to build up in the reaction medium. In other words, the apparent Km values of the diesters are the Km values of the diesters (KmA) plus the Km values of the monoesters (KmB), and all Vmax values are about the same. Moreover, the pH‐stat titration curve of the enzyme‐catalyzed hydrolysis of the diesters of ethylene glycol is initially hyperbolic, then there is a sharp falloff in the hydrolysis rate. The abrupt stoppage of the reaction (relaxation stage) may be due to the existence of two phases in the reaction medium, that is, the product (ethylene glycol) and the substrates (the diesters of ethylene glycol) are not miscible. Furthermore, quantitative structure‐activity relationships for varied acyl groups of mono‐and diesters of ethylene glycol are studied. The fact that both pKmA and pKmB values are linearly correlated with the hydrophobicity constant (π) but not with the electronic substituent constants (σ*) indicates that the affinity of these substrates for the enzyme depends only on the hydrophobicity of substrates.
The bioactive polysaccharides (named ZPF1) from yam (Dioscorea batatas) were chemically determined, suggesting repeating β-1,4-mannan as mainly having a feature of acetylation on C2−OH and C3−OH, ...around 28%. The ZPF1 participated in the stimulation of murine wild-type macrophages predominantly in tumor necrosis factor-α (TNFα). Toll-like receptor 4 is proved to be one of the cellular receptors in ZPF1-mediated TNFα secretion. Reactive oxygen species transmission and PI3-kinase are found necessary for regulating TNFα secretion by ZPF1 stimulation. Moreover, we found that extracellular signal-regulated kinase 1/2, Jun N-terminal kinase 1/2, and p38 mitogen-activated protein kinase play important roles in the regulation of TNFα secretion in ZPF1-stimulated macrophages.
The pH dependent lactonization of trisialic acid was examined using NMR and CE techniques. The combined studies indicate that lactonization is a dynamic, pH dependent process that occurs with ...preferential lactonization between the carbonyl of the central residue and the reducing end C-9 hydroxyl group.
Traditional medicines provide a fertile ground to explore potent lead compounds, yet their transformation into modern drugs is fraught with challenges in deciphering the target that is ...mechanistically valid for its biological activity. Herein we reveal that (Z)‐(+)‐isochaihulactone (1) exhibited significant inhibition against multiple‐drug‐resistant (MDR) cancer cell lines and mice xenografts. NMR spectroscopy showed that 1 resisted an off‐target thiolate, thus indicating that 1 was a target covalent inhibitor (TCI). By identifying the pharmacophore of 1 (α,β‐unsaturated moiety), a probe derived from 1 was designed and synthesized for TCI‐oriented activity‐based proteome profiling. By MS/MS and computer‐guided molecular biology approaches, an affinity‐driven Michael addition of the noncatalytic C247 residue of GAPDH was found to control the “ON/OFF” switch of apoptosis through non‐canonically nuclear GAPDH translocation, which bypasses the common apoptosis‐resistant route of MDR cancers.
Widerstand überwinden: Eine neue Klasse von Inhibitoren wurde entdeckt, die am nichtkatalytischen C247‐Rest von GAPDH angreifen, um SIAH1‐abhängige Apoptose und Androgenrezeptor‐Abbau auszulösen (siehe Bild). Die affinitätsgetriebene Michael‐Addition von Isochaihulacton kontrolliert das Ein‐ und Ausschalten der Apoptose über einen Mechanismus, der die gewöhnliche apoptoseresistente Route von multiwirkstoffresistenten Krebsarten umgeht.
For the first time, four (eclipsed-(O,O)-, gauche-, anti-, and eclipsed-(O,H)-) conformations of the ethylene glycol backbone of 1,2-ethylene-di-N-n- propylcarbamate (1) are detected in the mixed ...micelle of Triton X-100 and compound 1 from 600 MHz 1H NMR. Compound 1 is synthesized as a short-chain analog of glycerol lipid to probe the conformation of the ethylene glycol backbone of compound 1 in the Triton X-100 mixed micelle. From the 600 MHz 1H NMR study, the singlet at 4.26 ppm for the ethylene protons of compound 1 splits into four signals (3.68 and 3.70 (AX), 4.15 (quartet), 4.26 (singlet), and 4.30 (singlet)) after formation of the mixed micelle with Triton X-100. These four signals are assigned as the ethylene protons of the eclipsed-(O,H)-, gauche-, anti-, and eclipsed- (O,O)-conformations of the ethylene glycol backbone of compound 1 in the Triton X-100 mixed micelles, respectively. The population of gauche and anti conformations depends on the concentration of compound 1 in the Triton X-100 mixed micelle. Furthermore, the population of anti conformation is proportional but that of the gauche conformation is inversely proportional to the concentration of compound 1 in the Triton X-100 mixed micelle. Therefore, these four conformers of compound 1 are apparently trapped in the Triton X-100 mixed micelle. Alternatively, the major conformation of the ethylene glycol backbones of Triton X-100 is proposed as the gauche conformation in the mixed micelle because most ethylene glycol moieties of Triton X-100 curl in the mixed micelle and show a quartet at 3.65 ppm.
The structures of micelles of taurocholate (TC) have been debated for many years. According to Funasaki's model based on 2D NMR studies, anti‐parallel and parallel back‐to‐back dimers have been ...proposed as two major fragments in the micellar TC. However, according to Galantini's model based on X‐ray crystal structure, anti‐parallel and parallel face‐to‐face dimers have been proposed as two major fragments in the micelle. We propose a combined model from these two models for the structures of micelles of TC and suggest that these structures are equally composed of these four dimeric fragments. Lipid molecules can only insert into back‐to‐back dimeric fragments but not into face‐to‐face dimeric fragments in the mixed micelles of TC and lipid. A short‐chain analog of glycerol lipid, 1,2‐ethylene‐di‐N‐n‐butylcarbamate (1), was synthesized and was mixed with the micellar TC to form the mixed micelle of TC and compound 1. From the 1H NMR spectra, the ω‐methyl and β‐methylene protons of compound 1 split after formation of the mixed micelle with TC. Therefore, half of the compound 1 molecules insert into the anti‐parallel back‐to‐back dimers in the mixed micelle, and the other half of the compound 1 molecules insert into the parallel back‐to‐back dimers in the mixed micelle.
The structures of micelles of taurocholate (TC) have been debated for many years. According to Funasaki's model based on 2D NMR studies, anti-parallel and parallel back-to-back dimers have been ...proposed as two major fragments in the micellar TC. However, according to Galantini's model based on X-ray crystal structure, anti-parallel and parallel face-to-face dimers have been proposed as two major fragments in the micelle. We propose a combined model from these two models for the structures of micelles of TC and suggest that these structures are equally composed of these four dimeric fragments. Lipid molecules can only insert into back-to-back dimeric fragments but not into face-to-face dimeric fragments in the mixed micelles of TC and lipid. A short-chain analog of glycerol lipid, 1,2-ethylene-di-N-n-butylcarbamate (1), was synthesized and was mixed with the micellar TC to form the mixed micelle of TC and compound 1. From the ¹H NMR spectra, the ω-methyl and β-methylene protons of compound 1 split after formation of the mixed micelle with TC. Therefore, half of the compound 1 molecules insert into the anti-parallel back-to-back dimers in the mixed micelle, and the other half of the compound 1 molecules insert into the parallel back-to-back dimers in the mixed micelle.
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