Search results for "Bond"
showing 10 items of 3527 documents
A Microscopic Description of SARS-CoV-2 Main Protease Inhibition with Michael Acceptors. Strategies for Improving Inhibitors Design
2020
The irreversible inhibition of the main protease of SARS-CoV-2 by a Michael acceptor known as N3 has been investigated using multiscale methods. The noncovalent enzyme–inhibitor complex was simulated using classical molecular dynamics techniques and the pose of the inhibitor in the active site was compared to that of the natural substrate, a peptide containing the Gln–Ser scissile bond. The formation of the covalent enzyme–inhibitor complex was then simulated using hybrid QM/MM free energy methods. After binding, the reaction mechanism was found to be composed of two steps: (i) the activation of the catalytic dyad (Cys145 and His41) to form an ion pair and (ii) a Michael addition where the …
Interactions between volatiles and lipids in complex systems
1998
Partition equilibria of three aroma compounds in three different biphasic systems were studied by a liquid/liquid partition technique to investigate interactions that occur between volatiles and lipids in biphasic solutions. The lipids used were linoleic acid and ricinoleic acid and tetradecane as a model. The three aroma compounds were ethyl acetate, 2,5-dimethylpyrazine, and oct-1-en-3-ol. The results showed that the intermolecular forces involved were weak. Infrared spectroscopy was then performed on binary systems (tetradecane and linoleic acid or aroma compound) and on ternary systems (tetradecane, linoleic acid, and aroma compound) to determine the nature of the interactions. This met…
Electrochemical modifications of proteins: disulfide bonds reduction
2002
International audience; Electrochemical reduction of lysozyme disulfide bonds was achieved at pH between 10 and 11.Below pH 10, no disulfide bond cleavage was observed. At pH higher than 12, the cleavage of disulfide bonds is essentially due to hydrolysis. The addition of denaturant considerably enhanced the performance of the electrochemical device.
A detailed identification study on high-temperature degradation products of oleic and linoleic acid methyl esters by GC–MS and GC–FTIR
2012
GC-MS and GC-FTIR were complementarily applied to identify oxidation compounds formed under frying conditions in methyl oleate and linoleate heated at 180ºC. The study was focused on the compounds that originated through hydroperoxide scission that remain attached to the glyceridic backbone in fats and oils and form part of non-volatile molecules. Twenty one short-chain esterified compounds, consisting of 8 aldehydes, 3 methyl ketones, 4 primary alcohols, 5 alkanes and 1 furan, were identified. In addition, twenty non-esterified volatile compounds, consisting of alcohols, aldehydes and acids, were also identified as major non-esterified components. Furanoid compounds of 18 carbon atoms form…
Metabolic detoxification: implications for thresholds.
2000
The fact that chemical carcinogenesis involves single, isolated, essentially irreversible molecular events as discrete steps, several of which must occur in a row to finally culminate in the development of a malignancy, rather suggests that an absolute threshold for chemical carcinogens may not exist. However, practical thresholds may exist due to saturable pathways involved in the metabolic processing, especially in the metabolic inactivation, of such compounds. An important example for such a pathway is the enzymatic hydrolysis of epoxides via epoxide hydrolases, a group of enzymes for which the catalytic mechanism has recently been established. These enzymes convert their substrates via…
¿Una feria de cambios a la valenciana? Debate financiero y energía emprendedora en el siglo XVII
2020
In 1619 Philip IV sent to print a Real Pragmatic [Royal Pragmatic legislation] that would regulate changes between Valencia and Medina del Campo being introduced by Valencian merchant families to enable them to receive interest on their loans without being accused of usury. Only three years later, in 1622, the Republic of Genoa inaugurated the exchange fairs of Novi Ligure, with which the Genoese consolidated their international position in the international credit market. These apparently independent circumstances constitute an important episode for international financial knowledge and the transformation of the Mediterranean credit market during the seventeenth century. Studying financial…
All bonds are not the same: A response surface analysis of the perceptions of positive bonding relationships in therapy groups
2017
Intrapersonal split alliances were defined as discrepancies in how group members perceived their positive bonding relationships with the group leader, the other group members, and the group-as-a-whole, and were related to group members' outcome. Participants were 168 patients (116 women and 52 men) diagnosed as overweight or obese who participated in 1 of 20, 12-session, therapy groups for weight management. Group members completed the Outcome Questionnaire-45 (OQ-45, Lambert et al., 2004) pre- and posttreatment and the Group Questionnaire (GQ, Krogel et al., 2013) at early, middle and late group sessions. Early, middle, and late ratings were aggregated because bond scores were consistent a…
Crystal and solution structures of di-n-butyltin(IV) complexes of 5-[(E)-2-(4-methoxyphenyl)-1-diazenyl]quinolin-8-ol and benzoic acid derivatives: E…
2009
Abstract Reactions of nBu2SnCl(L1) (1), where L1 = acid residue of 5-[(E)-2-(4-methoxyphenyl)-1-diazenyl]quinolin-8-ol, with various substituted benzoic acids in refluxing toluene, in the presence of triethylamine, yielded dimeric mixed ligand di-n-butyltin(IV) complexes of composition [nBu2Sn(L1)(L2–6)]2 where L2 = benzene carboxylate (2), L3 = 2-[(E)-2-(2-hydroxy-5-methylphenyl)-1-diazenyl]benzoate (3), L4 = 5-[(E)-2-(4-methylphenyl)-1-diazenyl]-2-hydroxybenzoate (4), L5 = 2-{(E)-4-hydroxy-3-[(E)-4-chlorophenyliminomethyl]-phenyldiazenyl}benzoate (5) and L6 = 2-[(E)-(3-formyl-4-hydroxyphenyl)-diazenyl]benzoate (6). All complexes (1–6) have been characterized by elemental analyses, IR, 1H,…
Intermolecular oxidative dehydrogenative 3,3′-coupling of benzo[b]furans and benzo[b]thiophenes promoted by DDQ/H+: total synthesis of shandougenine B
2016
With an excess of a strong acid, 2,3-dichloro-5,6-dicyano-1,4-quinone (DDQ) is shown to promote metal-free intermolecular oxidative dehydrogenative (ODH) 3,3'-coupling of 2-aryl-benzo[b]furans and 2-aryl-benzo[b]thiophenes up to 92% yield as demonstrated with 9 substrates. Based on the analysis of oxidation potentials and molecular orbitals combined with EPR, NMR and UV-Vis observations, the studied reaction is initiated by a DDQ-substrate charge transfer complex and presumably proceeds via oxidation of the substrate into an electrophilic radical cation that further reacts with another molecule of a neutral substrate. The coupling reactivity can easily be predicted from the oxidation potent…
Superfluorinated ionic liquid crystals based on supramolecular, halogen-bonded anions
2016
Unconventional ionic liquid crystals in which the liquid crystallinity is enabled by halogen-bonded supramolecular anions [CnF2 n+1-I⋯I⋯I-CnF2 n+1]- are reported. The material system is unique in many ways, demonstrating for the first time 1) ionic, halogen-bonded liquid crystals, and 2) imidazolium-based ionic liquid crystals in which the occurrence of liquid crystallinity is not driven by the alkyl chains of the cation. Out of the ordinary: The high directionality of halogen bonds and the fluorophobic effect were exploited in the design and synthesis of a new family of unconventional superfluorinated ionic liquid crystals. The liquid crystallinity of the system is driven by halogen-bonded…