Etude de la regioselectivite et de la stereospecificite de l'oxydation d'acides gras par des monooxygenases a cytochrome P-450

SIGLEINIST TD 19548 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Epoxidation of cis and trans Δ9-unsaturated lauric acids by a cytochrome P-450-dependent system from higher plant microsomes

AbstractA new epoxygenase, differing in substrate and stereospecificity from those previously described in mammals, bacteria and Vicia faba, has been characterized in higher plants. A microsomal fraction from Jerusalem artichoke tubers which catalyses in-chain monohydroxylation of lauric acid has now been found to convert synthetic 9-dodecenoic acid (9-DDNA) to 9,10-epoxylauric acid. Epoxidation of the cis and trans isomers proceeds at similar rates affording the corresponding cis and trans epoxides. This reaction is dependent upon O2 and NADPH and does not occur with boiled microsomes. Lauric acid, carbon monoxide and polyclonal antibody against NADPH-cytochrome P-450 reductase from Jerusalem artichoke inhibit epoxide formation. Compared to freshly sliced tuber tissues, epoxidation activity was strongly enhanced in tissues aged in 20 mM aminopyrine solution. The possibility that 9, 10-epoxidation of 9-DDNA is catalyzed by the cytochrome P-450 isoenzyme involved in lauric acid in-chain hydroxylation in this plant was investigated

Surface chemistry and spectroscopy of the β-galactosidase Langmuir monolayer

[Display omitted] The changes of interfacial properties of β-galactosidase introduced into different pH environments are investigated through surface chemistry and in situ spectroscopy. Conditions for an optimal Langmuir monolayer formation were firstly obtained by varying the subphase salt concentration and the surface-pressure area isotherm was used to extrapolate the limiting molecular area of the enzyme monolayer to be around 42,000Å2molecule−1. Surface pressure stability measurements held at 20mN/m for 90min along with compression–decompression cycles revealed no aggregate formation at the air–water interface. Consistent with the data obtained from the isotherm, in situ UV–Vis and fluorescence spectroscopy shows a steep rise in absorbance and photoluminescence intensity correlating to with a switch from a liquid-expanded to a liquid-condensed phase. A decrease in subphase pH increased the electrostatic repulsion as the enzyme was protonated, leading to an expanded monolayer. Infrared absorption–reflection spectroscopy demonstrates that the enzyme adopts mainly β-sheet conformation at the air–water interface before and during the compression

Stereochemistry of oxidized fatty acids generated during catalytic oxygenation of lauric acid and unsaturated analogs by plant microsomes

AbstractThe capacity of microsomes from aminopyrine-induced Jerusalem artichoke (Helianthus tuberosus L.) to oxidize saturated and unsaturated fatty acids has been investigated using lauric acid and a series of unsaturated lauric acid analogs (7-, 8-, 9- and 10-dodecenoic acids) as radiolabeled substrates. In the presence of NADH, lauric acid was mono-hydroxylated principally at carbon 9. Steric analysis of this product showed a low enantiomeric excess of 28%. Mono-hydroxylated and mono-epoxidated reaction products were formed from the unsaturated analogs. The epoxidation/hydroxylation ratio was related to the position of the double bond in the aliphatic chain. The oxidation of 7-dodecenoic acid (7-DDNA) and 10-DDNA produced mainly 9-hydroxy-7-DDNA and 9-hydroxy-10-DDNA plus minor amounts of 7,8-epoxy- or 10,11-epoxylauric acid, respectively. In contrast, 8- and 9-DDNAs yielded essentially 8,9-epoxy- and 9,10-epoxylauric acids and smaller amounts of 10-hydroxy-9-DDNA and 8-hydroxy-9-DDNA, respectively. The optical purity and the absolute configuration of the major metabolites were investigated. Epoxidation ofZ 8-DDNA andZ 9-DDNA occurs with high enantiomeric excesses. When the double bond was in theZ configuration, (8S,9R)/(8R,9S) 8,9-epoxylauric acid (93/7) or (9R,10S)/(9S,10R) 9,10-epoxylauric acid (89/11) were produced. In contrast, when the double bond was in theE configuration, steric analysis showed an enantiomeric ratio of 52/48 forE 8,9-epoxide and of 59/41 forE 9,10-epoxide,Z 7-DDNA led to the formation of 98% of the 9(S)-hydroxy-Z 7-DDNA enantiomer, while 9-hydroxy-Z 10-DDNA derived fromZ 10-DDNA was 35% (R) and 65% (S)

Emotive response to a hybrid-face robot and translation to consumer social robots

We present the conceptual formulation, design, fabrication, control, and commercial translation of an Internet of Things (IoT)-enabled social robot as mapped through validation of human emotional response to its affective interactions. The robot design centers on a humanoid hybrid face that integrates a rigid faceplate with a digital display to simplify conveyance of complex facial movements while providing the impression of 3-D depth. We map the emotions of the robot to specific facial feature parameters, characterize recognisability of archetypical facial expressions, and introduce pupil dilation as an additional degree of freedom for emotion conveyance. Human interaction experiments demonstrate the ability to effectively convey emotion from the hybrid-robot face to humans. Conveyance is quantified by studying neurophysiological electroencephalography (EEG) response to perceived emotional information as well as through qualitative interviews. The results demonstrate core hybrid-face robotic expressions can be discriminated by humans (80%+recognition) and invoke face-sensitive neurophysiological event-related potentials, such as N170 and vertex positive potentials in EEG. The hybrid-face robot concept has been modified, implemented, and released in the commercial IoT robotic platform Miko (“My Companion”), an affective robot currently in use for human–robot interaction with children. We demonstrate that human EEG responses to Miko emotions are comparative to that of the hybrid-face robot validating design modifications implemented for large-scale distribution. Finally, interviews show above 90% expression recognition rates in our commercial robot. We conclude that simplified hybrid-face abstraction conveys emotions effectively and enhances human–robot interaction

β‑Galactosidase Langmuir Monolayer at Air/X-gal Subphase Interface

This article investigates the surface chemistry properties of the β-galactosidase monolayer at the air-subphase interface at the vicinity of its substrate, X-gal. We have demonstrated that the β-galactosidase in the monolayer form remained active and performed hydrolysis of the X-gal in the subphase. We investigated the β-galactosidase Langmuir monolayer in absence and presence of X-gal in the subphase of varying concentration of X-gal with the sodium chloride solution. It was found that the limiting molecular area as well as the collapse surface pressure kept on decreasing with the increasing concentration of X-gal. In accordance to the data obtained from the isotherm it was also found that β-galactosidase forms a stable monolayer that does not aggregate at the air-subphase interface. The stability of the monolayer at the air-subphase interface was studied by using compression–decompression cycles with and without X-gal at varying concentration and different surface pressures. The infrared reflection–absorption spectroscopy (IRRAS) and Brewster angle microscopy (BAM) of β-galactosidase Langmuir monolayer was also investigated for pure and mixed β-galactosidase at the air-subphase