Search results for "ACYLATION"
showing 10 items of 87 documents
Total Synthesis of the Antifungal Natural Product Mollisin
2013
Mollisin, a bioactive polyketide secondary metabolite of the fungus Mollisia caesia, was synthesized in nine linear steps from commercially available 2,6-dimethyl-γ-pyrone. A key transformation in this first total synthesis of mollisin was the ipso substitution of an arylstannane, which permitted the otherwise cumbersome introduction of the characteristic dichloroacetyl moiety. The fungal fungicide was obtained in an overall yield of 9 %.
Correlations in palmitoylation and multiple phosphorylation of rat bradykinin B2 receptor in Chinese hamster ovary cells.
1999
Rat bradykinin B2 receptor from unstimulated Chinese hamster ovary cells transfected with the corresponding cDNA has been isolated, and subsequent mass spectrometric analysis of multiple phosphorylated species and of the palmitoylation attachment site is described. Bradykinin B2 receptor was isolated on oligo(dT)-cellulose using N-(epsilon-maleimidocaproyloxy)succinimide-Met-Lys-bradykinin coupled to a protected (dA)30-mer. This allowed a one-step isolation of the receptor on an oligo(dT)-cellulose column via variation solely of salt concentration. After enzymatic in-gel digestion, matrix-assisted laser desorption ionization and electrospray ion trap mass spectrometric analysis of the isola…
Unraveling the SARS-CoV-2 Main Protease Mechanism Using Multiscale DFT/MM Methods
2020
<p>We present a detailed theoretical analysis of the reaction mechanism of proteolysis catalyzed by the main protease of SARS-CoV-2. Using multiscale simulation methods, we have characterized the interactions stablished by a peptidic substrate in the active site and then we have explored the free energy landscape associated to the acylation and de-acylation steps of the proteolysis reaction, characterizing the transition states of the process. Our mechanistic proposals can explain most of the experimental observations made on the highly similar ortholog protease of SARS-CoV. We point out to some key interactions that may facilitate the acylation process and thus can be crucial in the …
Unraveling the SARS-CoV-2 Main Protease Mechanism Using Multiscale Methods
2020
We present a detailed theoretical analysis of the reaction mechanism of proteolysis catalyzed by the main protease of SARS-CoV-2. Using multiscale simulation methods, we have characterized the interactions established by a peptidic substrate in the active site, and then we have explored the free energy landscape associated with the acylation and deacylation steps of the proteolysis reaction, characterizing the transition states of the process. Our mechanistic proposals can explain most of the experimental observations made on the highly similar ortholog protease of SARS-CoV. We point to some key interactions that may facilitate the acylation process and thus can be crucial in the design of …
Structural analysis of the lipid A isolated from Hafnia alvei 32 and PCM 1192 lipopolysaccharides[S]
2010
Hafnia alvei, a Gram-negative bacterium, is an opportunistic pathogen associated with mixed hospital infections, bacteremia, septicemia, and respiratory diseases. The majority of clinical symptoms of diseases caused by this bacterium have a lipopolysaccharide (LPS, endotoxin)-related origin. The lipid A structure affects the biological activity of endotoxins predominantly. Thus, the structure of H. alvei lipid A was analyzed for the first time. The major form, asymmetrically hexa-acylated lipid A built of beta-D-GlcpN4P-(1-->6)-alpha-D-GlcpN1P substituted with (R)-14:0(3-OH) at N-2 and O-3, 14:0(3-(R)-O-12:0) at N-2', and 14:0(3-(R)-O-14:0) at O-3', was identified by ESI-MS(n) and MALDI-tim…
On the dimerization of the primitive tRNAs: implications in the origin of genetic code.
2002
RNAs that catalyse their own aminoacylation have been recently selected in vitro. These findings support the notion that the primitive aminoacyl-tRNA synthetases may have been RNAs. In this paper, we propose a structural model for the first aminoacyl-tRNA synthetase consisting of an RNA complex formed between two primitive tRNA molecules through two intermolecular loop-strand interactions, and with implications in the origin of the genetic code.
Acylated oleanane-type saponins from Ganophyllum giganteum
2014
Abstract Five oleanane-type saponins , 3- O -β- D -glucuronopyranosylzanhic acid 28- O -β- D -xylopyranosyl-(1→3)-[α- L -rhamnopyranosyl-(1→2)]-(4- O -acetyl)-β- D -fucopyranosyl ester ( 1 ), 3- O -β- D -glucopyranosylzanhic acid 28- O -β- D -xylopyranosyl-(1→3)-[α- L -rhamnopyranosyl-(1→2)]-(4- O -acetyl)-β- D -fucopyranosyl ester ( 2 ), zanhic acid 28- O -β- D -xylopyranosyl-(1→3)-[α- L -rhamnopyranosyl-(1→2)]-(4- O -acetyl)-β- D -fucopyranosyl ester ( 3 ), zanhic acid 28- O -α- L -rhamnopyranosyl-(1→2)-4- O -[(3′-hydroxy-2′-methyl-butyroyloxy)-3-hydroxy-2-methyl-butyroyloxy]-β- D -fucopyranosyl ester ( 4 ), medicagenic acid 28- O -α- L -rhamnopyranosyl-(1→2)-4- O -[(3′-hydroxy-2′-methyl-…
Novel Acylated Triterpene Glycosides from Muraltia heisteria
2002
Four new acylated triterpene glycosides (1-4) have been isolated as two inseparable mixtures of the trans- and cis-3,4,5-trimethoxycinnamoyl derivatives (1,2 and 3,4) from the roots of Muraltia heisteria. The structures of these compounds were elucidated by various 1D and 2D NMR techniques, including (1)H and (13)C, COSY, NOESY, HSQC, TOCSY, and HMBC experiments and FABMS. Compounds 3 and 4 were shown to be cytotoxic in a human colon cancer cell line but did not show any ability to potentiate in vitro cisplatin cytotoxicity.
Acylated Preatroxigenin Glycosides from Atroxima congolana
2003
Six new acylated bisdesmosidic preatroxigenin saponins named atroximasaponins E1, E2 (1, 2), F1, F2 (3, 4), and G1, G2 (5, 6) were isolated as three inseparable mixtures of the trans- and cis-p-methoxycinnamoyl derivatives, from the roots of Atroxima congolana. Their structures were established through extensive NMR spectroscopic analysis as 3-O-beta-D-glucopyranosylpreatroxigenin-28-O-beta-D-xylopyranosyl-(1--4)-alpha-L-rhamnopyranosyl-(1--2)-[beta-D-glucopyranosyl-(1--3)]-[4-O-trans-p-methoxycinnamoyl]-beta-D-fucopyranoside (atroximasaponin E1, 1), and its cis-isomer, atroximasaponin E2 (2), 3-O-beta-D-glucopyranosylpreatroxigenin-28-O-beta-D-xylopyranosyl-(1--4)-alpha-L-rhamnopyranosyl-(…
Rational Synthesis of Multicyclic Bis[2]catenanes
2004
Bis-loop tetraurea calix[4]arene 6 has been prepared by acylation of the wide-rim calix[4]arene tetraamine 1 with the activated bis(urethane) 8 under dilution conditions. Similarly the bis(Boc-protected) tetraamine 2 is converted into the mono-loop derivative 3 which after deprotection and acylation gives the bisalkenyl derivative 5. In apolar solvents this tetraurea calix[4]arene 5 forms regioselectively a single hydrogen-bonded homodimer, from which the bis[2]catenane 10 a is formed in 49 % by a metathesis reaction followed by hydrogenation. Bis-loop derivative 6 forms no homodimers for steric reasons, but a stoichiometric mixture with the open-chain tetraalkenyl derivative 7 a contains e…