Configurational isomers and conformational structures of lycopene
Notice bibliographique
Résumé
Lycopene is an effective antioxidant in vivo and although it is present in its alltrans isomeric form in fruits and vegetables, serum and tissue samples show a predominance of various cis-isomers of lycopene.The present study was undertaken to investigate the molecular structure of several c/s-isomers of lycopene using an ab initio molecular computations.Relative stability of selected c/s-isomers of lycopene with respect to the all-trans isomer was studied.The following sequence of stability was observed.5-cis > all-treats > 9-cis > 13 -cis > 15 -cis > 7-cis > 11 -cisThe first four of these isomers had relative energies within + 1 kcal/mol, but the fifth isomer (i.e.15-cw) was within 3 kcal.mol" 1 .However, the last two isomers were less stable than the al\-trans isomer with more than 5 kcal.mol" 1 .Conformational study indicated that the central conjugated part of every lycopene isomer is planar.However, the two tail ends of the molecules, each containing three single C-C bonds, avoid coplanarity.Such conformations resulted in two non-equivalent C-H bond lengths in each of the two allylic pro-chiral methylene group (>C=CH-CH 2 -CH 2 -CH=C<).The putative mechanism of isomerization, involving one of the prochiral CH 2 groups is proposed.The exploratory conformational study was carried out on a Ci-Cg truncated lycopene.Likewise, the mechanistic study was conducted on a Ci-Cio fragment model of lycopene.ii DISCLAIMER Lycopene, the principal red pigment of tomato, was probably known for over a centruy even though it was isolated in pure form only in 1910.It took about three quarters of a century to recognize its anti-oxidant actitivity.The medical importance of Lycopene became apparent in the 1990 and its role in cardiovascular medicine is now eminently obvious.In spite of all these developments, Lycopene's mechanism of scavenging reactive oxygen species (ROS) is not well understood.The term ROS includes everything from singlet oxygen via superoxide anion and hydrogen peroxide, all the way to hydroxyl radical.Yet, it remians to be seen if Lycopene can react with all of them or some selected few species of ROS.The present dissertation will concentrate on the various isomeric forms and their numerous conformational structures of Lycopene.Since the electron density distribution of all these various structural forms are different, therefore they will have different chemical reactivity.It is not unreasonable to expect that these different chemical reactivities may well predetermine the anti-oxidant activities of Lycopene isomers and conformers.However, as the present dissertation represents a 'progress report* on Lycopene, along the lengthy road of research, the anti-oxidant activity of Lycopene will not be discussed.The dissertation, as its title suggests, will deal with the stability of the various configurational isomers and conformational structures of Lycopene.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,001 | 0,001 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,012 | 0,001 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».