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1
Mosco, Alessandro. "Sviluppo di un bioindicatore naturale per il monitoraggio della qualità delle acque." Doctoral thesis, Università degli studi di Trieste, 2013. http://hdl.handle.net/10077/8557.
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2011/2012La concentrazione del glucosio emolinfatico è regolata nei Crostacei dal crustacean Hyperglycemic Hormone (cHH), un neuropeptide prodotto e rilasciato in circolo nel complesso organo X-ghiandola del seno, localizzato nei peduncoli oculari. Il cHH, oltre a essere coinvolto nella regolazione di diversi processi fisiologici, è implicato anche nelle risposte da stress di origine ambientale o dovute all’esposizione a xenobiotici, il cui risultato finale è un aumento della glicemia. In numerose specie di crostacei sono state identificate più forme circolanti del cHH, alcune delle quali derivano da geni diversi e si differenziano per la sequenza amminoacidica, altre invece risultano da processi di maturazione post-traduzionale dei peptidi come l’isomerizzazione della L-Phe3 con la conseguente formazione di D-Phe3. Le eventuali differenze nella funzione biologica di queste due isoforme chirali sono ancora poco chiare, ma gli scarsi studi sin qui condotti indicano che il D-cHH ha una maggiore e più prolungata attività iperglicemizzante. Inoltre, è stato proposto un suo coinvolgimento sia nell’inibizione della sintesi degli ecdisteroidi sia nella regolazione osmotica. Due sono stati gli indirizzi principali di ricerca sviluppati in questi anni di dottorato. Il primo è consistito nel gettare le basi per la realizzazione di un organismo bioindicatore capace di rilevare la presenza di sostanze tossiche cambiando la propria colorazione in modo facilmente visualizzabile, ed è stato completato con il clonaggio e l’identificazione del promotore del cHH di Astacus leptodactylus (Crustacea, Decapoda), la verifica in vitro della sua funzionalità e l’identificazione di possibili siti di legame per dei fattori di trascrizione. L’obiettivo finale è la modifica in via transiente di Palaemon elegans e Palaemonetes antennarius (Crustacea, Decapoda) mediante l’iniezione di emociti trasfettati con il plasmide veicolante il promotore del cHH ed un gene reporter che visualizza la risposta mediante colorazione dell’animale. Il secondo progetto ha riguardato la sintesi chimica di alcune forme chirali del cHH di A. leptodactylus che è l’unica strategia possibile per ottenere peptidi identici all’ormone nativo, essendo la sola capace di consentire l’introduzione di tutte le modificazioni post-traduzionali necessarie. I peptidi ottenuti sono stati quindi adoperati in saggi biologici in vivo per provare la loro funzionalità. Inoltre, è stato fatto uno studio per appurare il possibile ruolo del cHH nel controllo dell’aggressività in Procambarus clarkii (Crustacea, Decapoda). Per ottenere una quantità sufficiente delle forme chirali del cHH in modo da poterne studiare la funzione biologica, abbiamo scelto la strada della sintesi chimica in fase solida (SPPS). La SPPS è generalmente limitata alla sintesi di peptidi non più lunghi di 40 amminoacidi. Per ottenere sequenze più lunghe è necessario sintetizzare segmenti diversi e quindi ligarli assieme attraverso delle reazioni chimiche. In questo caso si è adoperata la native chemical ligation. Il primo passo ha riguardato la sintesi di sei segmenti (QVF-cHH4-38, QVdF-cHH4-38, pEVF-cHH4-38, pEVdF-cHH4-38, pEVdA-cHH4-38, cHH-39-72) che legati fra loro in maniera diversa avrebbero portato alla formazione di cinque peptidi ammidati al C-terminale, due con la L-Phe3 e la parte N-terminale libera oppure bloccata con il piroglutammato, due con la D-Phe3 e la parte N-terminale anch’essa libera oppure bloccata, e uno con la D-Phe3 sostituita dalla D-Ala3 e l’N-terminale bloccato dal piroglutammato. La sintesi dei diversi segmenti non ha dato particolari problemi, ma la purificazione del segmento cHH-39-72 è risultata particolarmente difficile, in quanto questo peptide è risultato essere molto poco solubile. Questo problema è stato risolto con l’aggiunta di gruppi –SO3 allo zolfo delle cisteine che ha reso solubile il segmento cHH-39-72. Sono stati quindi sintetizzati in quantità sufficienti, dell’ordine di un centinaio di microgrammi, le seguenti forme chirali del cHH: QVdF-cHH, QVF-cHH, pEVF-cHH, pEVdF-CHH e pEVdA-cHH. In quest’ultima isoforma la D-fenilalanina in posizione 3 è stata sostituita dalla D-alanina, per verificare se la fenilalanina avesse un ruolo fondamentale nella funzionalità del peptide. I peptidi di sintesi sono stati quindi utilizzati per eseguire dei saggi in vivo su A. leptodactylus, iniettando nei gamberi il cHH sintetico e verificando la risposta biologica indotta attraverso il dosaggio della glicemia. I prelievi per il dosaggio del glucosio sono stati fatti ai tempi 0 h, 1 h, 2 h, 4 h, 8 h e 24 h. Il profilo temporale della risposta glicemica indotta dalle due forme chirali è diverso, con il L-cHH avente un picco di risposta tra le 2 h e le 4 h, mentre il picco massimo della risposta del D-cHH è più tardivo, situandosi tra le 4 h e le 8 h. Invece, la differenza nella risposta iperglicemica tra la forma bloccata all’N-terminale (Glp-D-cHH) e la forma non bloccata (D-cHH) non è stata significativa a dimostrazione che la presenza del piroglutammato non influenza la risposta biologica indotta dal cHH. L’attività biologica dell’isomero Glp-dA-cHH è stata verificata usando il medesimo protocollo. L’attività iperglicemizzante di questo peptide è risultata essere significativamente inferiore a quella indotta dal Glp-D-cHH. Il risultato ottenuto dimostra che la porzione N-terminale del cHH è fondamentale per la funzionalità del peptide. Lo studio del promotore del cHH è stato effettuato su una sequenza clonata di 176 nucleotidi a monte della regione 5’ del gene per il cHH di A. leptodactylus, che è stata inserita in un vettore senza promotore (pGL3-Basic) a monte del gene reporter per la luciferasi. Con questo vettore sono state trasfettate cellule HEK 293T e la funzionalità del promotore è stata dimostrata da un incremento di circa 1000 volte nell’espressione della luciferasi rispetto a pGL3-Basic. La ricerca di eventuali siti di legame per elementi di regolazione presenti nella sequenza clonata ha consentito di identificare numerosi possibili siti di legame, inclusi una TATA box a -23, una CCAAT box a -78, due GC box a -63 e -70, ed altri per specifici elementi di trascrizione, più precisamente una sequenza a -91 dove i siti di legame per il cAMP response element-binding (CREB), l’elemento di risposta all’ipossia (HRE), il recettore per l’estrogeno (ER-alpha) si sovrappongono, mentre a -160 è stato identificato un possibile sito di legame per il recettore dell’ecdisone (EcR). L’influenza del cHH sull’aggressività in P. clarkii è stata studiata iniettando negli animali il cHH nativo estratto dalle ghiandole del seno. In generale gli animali in cui era stato iniettato il cHH hanno mostrato un aumento nell’espressione della dominanza, gli alfa attraverso un aumento della durata dei combattimenti e i beta per la maggiore intensità dei combattimenti che ne aumentava la dominanza fino a raggiungere una temporanea inversione della gerarchia. Il potenziamento del comportamento aggressivo potrebbe essere dovuto o a una modulazione da parte del cHH dei neuroni che controllano l’espressione del comportamento agonistico, oppure essere dovuto a una maggiore mobilizzazione delle risorse energetiche necessarie per la lotta. Per la prima volta sono state ottenute diverse isoforme del cHH mediante la sintesi peptidica in fase solida accoppiata alla native chemical ligation. I dati ottenuti indicano che questa è la strategia appropriata per la sintesi dei peptidi della famiglia del cHH, essendo l’unica in grado di consentire l’introduzione di tutte le modifiche post-traduzionali per ottenere un peptide identico all’ormone nativo. L’ottimizzazione del presente protocollo consente di rendere disponibili adeguate quantità di peptidi per esperimenti su larga scala, in vivo e in vitro, che possono portare a una migliore conoscenza della funzione del cHH e della relazione tra funzione e struttura. Inoltre sono state gettate le basi per la realizzazione di un organismo bioindicatore per monitorare l’inquinamento delle acque. È stato clonato il promotore del cHH di A. leptodactylus e per la prima volta la funzionalità di un promotore di un peptide della famiglia del cHH è stata verificata in un saggio in vitro. L’identificazione di diversi possibili siti di legame per gli elementi di regolazione nel promotore del cHH suggerisce che l’espressione del cHH sia regolata da svariati fattori fisiologici e ambientali. I risultati ottenuti sono rilevanti per futuri studi indirizzati alla comprensione del ruolo che i fattori di trascrizione identificati possono avere nella regolazione del promotore del cHH. Infine, lo studio sulla relazione di dominanza in Procambarus clarkii ha dimostrato, per la prima volta, che un neuropeptide, nella fattispecie il cHH, è in grado di modulare il comportamento aggressivo, sino a invertire, sia pur temporaneamente, il rango.
XXIV Ciclo
1955
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Pratumyot, Yaowalak. "The Folding and Assembly of Stereoisomeric Twisted Baskets." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1471602282.
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Luk, Ka Fai. "Process development for separation and purification of schisandrin B stereoisomer from fructus schisandrae /." View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?BIEN%202007%20LUK.
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Girardin, André. "Nouvelle voie d'acces stereospecifique a la vitamine a, l'acide retinoique et son isomere 13-cis : synthese d'analogues." Université Louis Pasteur (Strasbourg) (1971-2008), 1987. http://www.theses.fr/1987STR13157.
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Les acides retinoiques all trans et 13-cis offrent un grand interet dans le domaine medical, en particulier pour le traitement de maladies de la peau. En vue d'obtenir des structures offrant un meilleur indice therapeutique, differents analogues de l'acide retinoique ont ete synthetises. Dans une premiere partie, une synthese originale de chromannes est decrite. Dans une seconde partie, les analogues sont prepares par reaction de wittig mais il s'avere que la purification des isomeres est extremement difficile. En vue de supprimer le probleme de la separation, il a ete realise une etude utilisant le titane a degre d'oxydation zero. Il a ete montre que l'utilisation de cette nouvelle methode permettait de preparer une chaine polyenique all trans ainsi qu'une chaine polyenique presentant un maillon cis terminal. Cette methode a ete utilisee pour preparer des exemples en serie terpenique ainsi qu'en serie aromatique
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Stojanovic, Sandra. "Controlling Dynamic Stereoisomerism in Gated Molecular Baskets." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1342802291.
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Brunet, Vincent. "Synthesis studies to single stereoisomers of the vicinal trifluoroalkane motif." Thesis, St Andrews, 2009. http://hdl.handle.net/10023/853.
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Shah, Vibhakar Jayantilal. "Synthesis of cannabidiol stereoisomers and analogs as potential anticonvulsant agents." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184523.
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Anticonvulsant activity of cannabidiol (CBD) has been well documented in various laboratory animal species and also in man. As part of our continuing effort to study and to define the structure anticonvulsant relationship several analogs of CBD were synthesized wherein its structural units, namely, the terpene ring, aryl ring and/or side chain were systematically modified. These analogs include the: (1) unnatural (+)-Cannabidol (1b), (2) Delta-3-carenyl analog-(+)-carenadiol (45a), its diacetate (45b) and its 1",1"-dimethylheptyl side chain analog (45c), and (3) unnatural 7-acetoxycannabidiol (46b). (+)-Cannabidiol (1b) was synthesized in about 20-25% yield from olivetol (51) and two different p-menthadienols (67 and 70) as monoterpenoid synthons. (-)-p-Mentha-1,8-dien-3-ol (67) was prepared from (-)-limonene (65) by chromium trioxide-pyridine complex oxidation followed by cerium trichloride assisted sodium borohydride reduction of the obtained ketone (66a). (-)-p-Mentha-2,8-dien-1-ol (70) was synthesized from 1:1 mixture of cis- (69a) and trans-epoxide (68a) of limonene (65) in about 35% yield. The reaction involves phenylselenide anion mediated stereospecific trans-diaxial opening of the epoxide ring to give the required alcohol (70) along with its regioisomer (71) as the major product (79%). The delta-3-carenyl analog (+)-carenadiol (45a) was synthesized from car-4-en-3β-ol (80) and olivetol (51) in about 20% yield. Car-4-en-3β-ol (80) was prepared in about 90-95% yield from the corresponding 3β,4β-epoxy carane (77) by following the same methodology described for (70). The compounds were evaluated for anticonvulsant activity in seizure susceptible (AGS) rats and for neurotoxicity in the rotorod (ROT) test. A general lack of stereoselectivity for the anti-AGS and ROT neurotoxic effects was observed for CBD and its derivatives. Thus (-)-CBD (1a) was marginally more potent than (+)-CBD (1b). But the CBD analog derived from (+)-car-3-ene (72), i.e., (+)-carenadiol (45a), is of interest because of its high protective index (PI = 5.1) and is therefore comparable to(1b) (to which it is stereochemically related) in potency. The 1",1"-dimethylheptyl derivative ((+)-45b), could not separate anticonvulsant activity from neurotoxicity. (Abstract shortened with permission of author.)
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Charbonnier, Florence. "Cycloaddition du dichlorocétène avec des éthers d'énols chiraux : application à la synthèse énantiosélective des (-)-[alpha]- et (+)-[bêta]- cuparénones." Grenoble 1, 1987. http://www.theses.fr/1987GRE10069.
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La cycloaddition du dichlorocetene et des ethers d'enols chiraux conduit a des cyclobutanones fonctionnalises avec une diastereoselectivite elevee. Des intermediaires de purete enantiomerique elevee (alpha-chlorocyclopentenones et derives) sont obtenus apres liberation de l'auxiliaire chiral. Dans ce contexte, de nouvelles methodes stereoselectives de preparation d'ethers d'enols chiraux ont ete mises au point. La reduction d'alpha-alcoxy phosphates d'enols issus de l'enolisation stereoselective d'esters a ete appliquee a l'obtention d'ethers d'enols de configuration z. La reduction d'ethers acetyleniques, pour lesquels une nouvelle methode de synthese est propose, a permis l'acces aux ethers d'enols de configuration z ou e. Le potentiel de la methode est illustre par la synthese des alpha-cuparenone-(r) et beta-cuparenone-(r) (isomeres naturels) enantiomeriquement pures a partir d'un meme intermediaire, issu de la cycloaddition asymetrique du dichlorocetene et d'un ether d'enol chiral approprie
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Capodiferro, Marco. "Determinazione delle barriere rotazionali di nuovi atropisomeri N-N: confronto tra metodi DFT e sperimentali." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/23195/.
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Theoretical DFT calculations on rotational barriers of tetrasubstituted hydrazines were performed in order to synthesize new enantioenriched atropoisomers with chiral N-N axis. The molecules studied were chosen to be subsequently synthesized through asymmetric organocatalysis. New atropoisomers with chiral N-N axis were synthesized through organocatalysis methods via enamine or phase transfer. Cinchona alkaloid derivatives were used as catalysts. HPLC analyzes show that the three new synthesized molecules are atropoisomers at room temperature. Using an asymmetric procedure to synthesize the molecules studied, it was possible to generate enantiomeric excesses that remained unchanged for more than three weeks. The experimental rotational barrier of one of the three synthesized compounds was calculated. The experimental energy barrier at 25°C (ΔG^≠=25,7 kcal/mol) was lower than the DFT calculations and with a tendency to increase with temperature, due to a negative reaction entropy.
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Hout, Jamal el. "Etude des mouvements moleculaires dans le polyacetylene par courant thermostimule." Toulouse 3, 1986. http://www.theses.fr/1986TOU30061.
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Arastoo, Mahmoud. "The synthesis and biological evaluation of stereoisomeric bis quaternary benzyltetrahydroisoquinolinium salts." Thesis, University of Strathclyde, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248731.
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Niger, Robert J. "Addition of arenesulfenyl chlorides to quadricyclene /." Online version of thesis, 1992. http://hdl.handle.net/1850/11153.
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Roeder, Michael. "Synthesis and analytics of single stereoisomers of valnoctamide - potential new antiepileptic drugs /." [S.l. : s.n.], 2000. http://www.gbv.de/dms/bs/toc/313887071.pdf.
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Neimert-Andersson, Kristina. "Synthesis of Polyhydroxylated Surfactants : Comparison of Surfactant Stereoisomers and Investigation of Haemolytic Activity." Doctoral thesis, Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-461.
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Keir, Sandra Dhian. "The role of racemic salbutamol and its stereoisomers on airway responsiveness in vivo." Thesis, King's College London (University of London), 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249720.
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Fang, Xiaojun. "Stereoisomeric selectivity of 2,3-dimercaptosuccinic acid in chelation therapy for heavy metal poisoning." Diss., The University of Arizona, 1995. http://hdl.handle.net/10150/187045.
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Racemic-2,3-dimercaptosuccinic acid (rac-DMSA)¹ was synthesized and its structure in the solid state was studied by single crystal X-ray analysis. The three-dimensional structure of rac-DMSA solid is stabilized by van der Waals forces, whereas the meso-DMSA solid is stabilized by hydrogen bonding. This accounts for the drastic difference in the solubilities of DMSA stereoisomers. The behavior of DMSA stereoisomers in aqueous solution were studied by potentiometric titration, IR and ¹H NMR. Rac-DMSA irreversibly converts to the meso form at an elevated temperature under acidic conditions. Two mechanisms were proposed to explain the conversion. At high pH rac-DMSA tends to form ion-paired complexes with alkaline counter ions via two carboxylate groups. At physiological pH DMSA stereoisomers form two intramolecular six-membered rings. The formation constants and the structures of lead and zinc chelates of DMSA stereoisomers formed in aqueous solution were determined by potentiometric titration, IR and ¹H NMR. Lead and zinc complex with rac-DMSA to a greater extent than with meso-DMSA. DMSA stereoisomers tend to form dimeric chelates with Zn²⁺, but monomeric chelates with Pb²⁺. In the zinc chelates of rac-DMSA two bulky carboxylate groups of the ligand have a staggered anti-relation, whereas in the zinc chelates of meso-DMSA two carboxylate groups assumes a staggered gauche-relation. This accounts for that the formation constants of zinc chelates of rac-DMSA are invariably larger than those of the corresponding chelates of meso-DMSA. The binding sites in PbL of DMSA stereoisomers are two thiolate groups and one carboxylate group of the ligands. In the lead chelates of the stereoisomers of DMSA, rac-DMSA exists in a staggered anti-conformation, but meso-DMSA favors a staggered gauche-conformation with respect to the bulky carboxylate groups. This accounts for that the formation constants of the lead chelates of rac-DMSA are invariably larger than those of the corresponding chelates of meso-DMSA. On the basis of our studies ZnL₂ chelate of rac-DMSA has been proposed to be a more effective lead chelator than meso-DMSA for therapeutical use.
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Morello, Glenn R. "Stereoselectivity in organometallic catalysis : analysis by means of computational and mathematical chemistry /." Electronic version (Microsoft Word), 2003. http://dl.uncw.edu/etd/2003/morellog/glennmorello.doc.
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Dickins, Rachel Sarah. "Chiral lanthanide complexes." Thesis, Durham University, 1997. http://etheses.dur.ac.uk/4706/.
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The use of chiral lanthanide complexes as probes to investigate interactions with other chiral molecules and macromolecules is of particular interest. A key step in the development of such systems is the preparation of a single, rigid enantiomer of the complex which is conformationally rigid on the NMR timescale or the lifetime of the metal-based emission. Chiral europium and terbium complexes are of particular concern as they may function as emissive probes and are amenable to analysis by circular dichroism and circularly polarised lummescence. Charge neutral and cationic complexes of N-substituted 1,4,7,10- tetraazacyclododecane, functionahsed with three phosphmate and one amide pendent arms, or two, three and four pendent amide arms containing a remote chiral centre, have been prepared. The chirality of the remote stereocentre determmes the helicity of the arrangement of the pendent arms and the conformation of the 12-membered macrocycle.The chiral europium and terbium complexes of the tetraamide complexes exist as single, rigid enantiomers, exhibiting a well-defined metal-based circularly polarised emission. Circular dichroism studies reveal that exciton coupling occurs between adjacent pairs of 1-naphthyl chromophores of tetraamides, whereas the constitutional 2- naphthyl isomers exhibit excimer formation. The behaviour of the di-, tri-, and tetraamide complexes in the presence of added anions has been investigated. The measurement of the luminescent lifetime of the excited state and the circularly polarised emission exhibited by the enantiopure complexes in aqueous solution affords a novel way of signalling the presence of selected oxy-anions.
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Paterson, David S. "Imaging cholinergic function in vivo in the brain with radioiodinated stereoisomers of quinuclidinyl benzilate." Thesis, University of Glasgow, 1998. http://theses.gla.ac.uk/3755/.
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This thesis evaluates the ability of (R,S)- and (R,R)-[125I]-QNB, two radioiodinated diastereoisomers of the high affinity muscarinic antagonist quinuclidinyl benzilate (QNB), to image dynamic changes in cholinergic function in the central nervous system using in vivo autoradiography. The regional uptake and retention of (R,S)-[125I]-QNB in the rat brain between 2 and 24 hours after intravenous administration was investigated to assess the utility of this technique to image muscarinic receptors in the central nervous system. Similarly, the uptake and retention of (R,R)-[125I]-QNB was investigated between 30 mins and 6 hours after administration using in vivo autoradiography and was compared to that of (R,S)-[125I]-QNB. Secondly, the sensitivity of (R,S)- and (R,R)-[125I]-QNB to dynamic changes in cholinergic neurotransmission in vivo, was assessed in conscious rats. The uptake and retention of (R,S)- and (R,R)-[125I]-QNB following a cholinergic challenge produced by administration of the long lasting AChE inhibitor heptylphysostigmine, was investigated. Regional brain levels of (R,S)- and (R,R)-[125I]-QNB in heptylphysostigmine treated animals were compared to levels in saline treated animals by in vivo autoradiography. The ability of ACh to displace (R,S)- and (R,R)-[125I]-QNB binding from rat brain sections in vitro in the presence of heptylphysostigmine was also investigated. Finally, the effects of heptylphysostigmine administration on regional cerebral blood flow were investigated using [14C]-IAP autoradiography in conscious rats. Three hypotheses were considered to account for the lack of radioligand displacement observed following heptylphysostigmine administration: 1) Heptylphysostigmine was ineffective in inhibiting AChE and raising synaptic ACh levels at the dosage used in this thesis. 2) A small amount of displacement occurred but was masked by the effects of increased cerebral blood flow. 3) (R,S)- and (R,R)-[125I]-QNB are of too high affinity for mAChRs to be displaced by endogenous neurotransmitter. The third hypothesis is viewed as the most plausible. In conclusion, (R,S)- and (R,R)-[125I]-QNB are unsuitable ligands for the detection of cholinergic function in vivo.
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Mann, Timothy Earl. "The synthesis and characterisation of a series of cyclic liquid-crystalline polymers and their stereoisomers." Thesis, University of Hull, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363268.
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Etzold, Bastian [Verfasser]. "Epimerisierung der Menthol-Stereoisomere: Kinetische und reaktionstechnische Studien für die heterogen katalysierte Mentholsynthese / Bastian Etzold." Aachen : Shaker, 2008. http://d-nb.info/1164342460/34.
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Mifsud, Janet. "Chiral aspects of the disposition and pharmacology of the enantiometers of ethosuximide." Thesis, Queen's University Belfast, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336672.
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Upadhyay, Sunil. "Synthesis and Antifungal Evaluation of Spirostane Saponins." ScholarWorks@UNO, 2011. http://scholarworks.uno.edu/td/1414.
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Methods for the preparation of novel antifungal saponins have been investigated in
order to further explore their medicinal utility and provide the opportunity to synthesize
their derivatives.
Through this work, several partially protected stereoisomers of Cholestane,
Androstane and Spirostane have been prepared which could be used for the synthesis of
various saponin derivatives in order to discover novel saponin based antifungal agent.
Various mono and disaccharide derivatives of these steroids have been synthesized and
evaluated for their antifungal activity against four pathogenic fungal strains. Among the
various derivatives maltose derivatives were found to have the best antifungal activity.
However there is a need for more extensive SAR studies to discover compounds with
better potency.
Additionally, the branched oligosaccharide synthesis was explored in two parts.
First, these results demonstrated that the central 2,3-branched portion can be synthesized
efficiently from a partially protected glucopyranosyl acceptor since the C-2 and C-3
alcohols differ in their reactivity in glycosylation reactions. Second, a tagged sugar based
strategy for synthesis of branched oliogosaccharides was developed, and found to be
effective for general synthesis of branched oligosaccharides.
Microwave assisted synthesis of cyclic imides have been explored this was a key
precursor for the synthesis of our tag molecules which were required for synthesis of
branched oligosachharides. A comparison of microwave versus conventional methods for
synthesis of cyclic imides has been studied. The synthesis of tagged sugars and their
selective deprotection to remove tag molecules were successfully explored in order to
have proof of concept for its applicability towards synthesis of branched
oligosaccharides.
Benzylic mono and dibromination was achieved in very high yields using
microwave conditions using environmentally friendly solvent in order to avoid use of
carcinogenic carbon tetrachloride as solvent for this type of reactions. In addition reaction
time was reduced to 30 minutes to 3 hours compared to convention methods, which
needed more than 15 hours for the benzylic bromination reaction.
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Chang, An-Ni. "Total synthesis of (3R,3'R,6'R)-lutein, (3R,3'R)-zeaxanthin and their stereoisomers." College Park, Md. : University of Maryland, 2008. http://hdl.handle.net/1903/9016.
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Thesis (Ph. D.)--University of Maryland, College Park, 2008.Thesis research directed by: Dept. of Chemistry and Biochemistry. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Xidos, James Dimitrios. "A theoretical study of stereoselectivity in the Diels-Alder reaction." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0015/NQ47505.pdf.
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Lamy, Dominique de. "Stéréospécificité et métabolisme d'un bêta-bloquant dans le cadre de l'ètude d'une relation pharmacocinétique-pharmacodynamie chez l'homme." Paris 5, 1989. http://www.theses.fr/1989PA05P175.
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Branitzki, Pierre. "Wirkmechanismen der Stereoisomere von Mepivacain, Ropivacain und Bupivacain an Tetrodotoxin-resistenten Natriumkanälen isolierter Spinalwurzelganglienneurone der erwachsenen Ratte." [S.l.] : [s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=960463372.
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Doroudian, Ahmad. "Pharmacokinetics and conjugative metabolism of labetalol stereoisomers in pregnant sheep : a chiral drug case study in pregnancy." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0022/NQ38879.pdf.
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Whiteside, R. G. "Studies of high speed countercurrent chromatography and liquid chromatography-atmospheric pressure ionisation/mass spectrometry in stereoisomeric separations." Thesis, Swansea University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636588.
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This thesis describes studies of High Speed Countercurrent Chromatography (HSCCC) and combined Liquid Chromatography-Mass Spectrometry using atmospheric pressure ionisation techniques (LC-API/MA) is stereoisomeric separations related to the pharmaceutical industry. Initially the development of a generic strategy for CCC methodology, which enables this technology to be widely acceptable as a choice for product separation, is discussed. Investigations in the application of HSCCC for chiral separations of diastereomers and enantiomers are also described. Stereoisomeric separations of diastereomers in LC-API/MS are described. In addition, the novel application of enantiomeric separations using cyclodextrin additives in LC-API/MS, are discussed. Chapter 1 gives a general introduction to the thesis. Chapter 2 focuses on the development of a novel generic CCC methodology that can be easily utilised by chromatographers not familiar with CCC technology. Possible correlations between non-chiral separations by CCC, and well established techniques, TLC and HPLC, are discussed through investigations with a range of compounds of varying hydrophobicity using various biphasic solvent systems. The chapter includes an examination of isocratic and gradient elution systems in CCC. Chapter 3 describes the application of cyclodextrins as chiral additives in HPLC and CCC for the enantiomeric separation of chiral drugs. Analytical RP-HPLC is examined as a possible modelling techniques for chiral CCC (Using CDs immobilised in the stationary phase) through investigations of the parameters that effect enantio-separations. This chapter also describes a novel application of the use of on-line mass spectrometry detection for LC chiral separations employing non-volatile cyclodextrins in the mobile phase. The performance of the MS detector is discussed, with regards to reproducibility, linear range of calibration and limits of detection. Optimisation of CCC for the isolation of two pairs of diastereomers from the cinchona alkaloid family; cinchonine and cinchonidine and quinine and quinidine is discussed in chapter 4.
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Scheithauer, Simone. "Vergleichende Analyse der Stereoisomeren der Rhenium-118(V)-Dimercaptobernsteinsäure in vitro und im Tiermodell /." Bonn, 2008. http://opac.nebis.ch/cgi-bin/showAbstract.pl?sys=000253926.
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Aman, Robert [Verfasser]. "Carotenoid Stereoisomers in Dietary Supplements and Vegetables: Isolation, Characterization and Effects of Processing on their Formation / Robert Aman." Aachen : Shaker, 2006. http://d-nb.info/1186586966/34.
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Canfield, Peter John. "The Polytope Formalism: isomerism and associated unimolecular isomerisation." Thesis, The University of Sydney, 2022. https://hdl.handle.net/2123/29731.
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This thesis concerns the ontology of isomerism, this encompassing the conceptual frameworks and relationships that comprise the subject matter; the necessary formal definitions, nomenclature, and representations that have impacts reaching into unexpected areas such as drug registration and patent specifications; the requisite controlled and precise vocabulary that facilitates nuanced communication; and the digital/computational formalisms that underpin the chemistry software and database tools that empower chemists to perform much of their work.
Using conceptual tools taken from Combinatorics, and Graph Theory, means are presented to provide a unified description of isomerism and associated unimolecular isomerisation spanning both constitutional isomerism and stereoisomerism called the Polytope Formalism. This includes unification of the varying approaches historically taken to describe and understand stereoisomerism in organic and inorganic compounds.
Work for this Thesis began with the synthesis, isolation, and characterisation of compounds not adequately describable using existing IUPAC recommendations. Generalisation of the polytopal-rearrangements model of stereoisomerisation used for inorganic chemistry led to the prescriptions that could deal with the synthesised compounds, revealing an unrecognised fundamental form of isomerism called akamptisomerism.
Following on, this Thesis describes how in attempting to place akamptisomerism within the context of existing stereoisomerism reveals significant systematic deficiencies in the IUPAC recommendations. These shortcomings have limited the conceptualisation of broad classes of compounds and hindered development of molecules for medicinal and technological applications.
It is shown how the Polytope Formalism can be applied to the description of constitutional isomerism in a practical manner. Finally, a radically different medicinal chemistry design strategy with broad application, based upon the principles, is described
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Bång, Joakim. "Purification, Stereoisomeric Analysis and Quantification of Biologically Active Compounds in Extracts from Pine Sawflies, African Butterflies and Orchid Bees." Doctoral thesis, Mittuniversitetet, Institutionen för naturvetenskap, teknik och matematik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-14662.
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Stereochemistry plays an important role in nature because biologically important molecules such as amino acids, nucleotides and sugars, only exist in enantiomerically pure forms. Semiochemicals carry messages, between the same species (pheromones) and between different species (allelochemicals). Both pheromones and allelochemicals can be used as environmentally friendly pest management. Many semiochemicals, i.e. behaviour modifying chemicals, consist of pure or well-defined mixtures of stereoisomers, where some of the other stereoisomers can be repellent. It is therefore important to be able to separate them to produce a synthetic pheromone in a mixture that is attractive. Pine sawflies are a family of insects that in some cases can be severe defoliators of conifer trees. Diprion pini, Diprion similis and Neodiprion sertifer are severe pests for these trees and have got the most attention in pine sawfly pheromone studies. The pheromone precursors are stored in the female body as long-chain secondary alcohols, which, when released, are esterified to acetates or propionates. The alcohols are chiral, and normally one of the stereoisomer is the main pheromone component, sometimes possible together with other stereoisomers as essential minor components. Bicyclus is a genus of African butterflies, and especially Bicyclus anynana has become a popular model for the study of life history evolution, morphology, mating choice and genetics. The wing pattern of Bicyclus differs depending on the season, with large eyespots during the rain-season and small or absent spots during the dry season. Euglossa is one of the genera among the orchid bees in the Neotropics that does not produce its own pheromone. Instead, the males collect fragrances from orchids and other sources and store them in a pocket in their hind legs. Both Bicyclus and Euglossa use semiochemicals similar to pine sawflies, and thus can be analysed by the same methods. Pheromones and other semiochemicals in insects are often present in low amounts in a complex matrix, and purification of the sample before chemical analysis is often required. A common method is gradient elution on a solid phase silica column. Separation of stereoisomers can be achieved either by using a column with a chiral stationary phase (CSP) or with pre-column derivatisation using a column with an achiral stationary phase (ASP) or a combination of both, with mass detection as the dominant detection method. The purpose of this work has been to improve the purification method, find suitable methods to separate the stereoisomers of secondary alcohols, and to apply this on extracts of insects. By selecting the right fractions to collect during gradient elution the purification method was optimised. To reduce plasticizer contamination from ordinary columns, solid phase columns of Teflon or glass were used. For pre-column derivatisation of different chiral alcohols various acid chlorides were tested. For the pine sawfly pheromone precursors enantiopure (2S)-2-acetoxypropionyl chloride was the best choice. To separate some of the stereoisomers achiral 2-naphthoyl chloride was used. For derivatisation of 6,10,14-trimethylpentadecan-2-ol (R)-trans-chrysanthemoyl chloride was the best choice. The derivatised alcohols were separated on different columns, both chiral and non-chiral. Varian FactorFour VF-23ms was chosen as a general-purpose column, the Agilent HP-88 column was the best column with an ASP of those tested, and the Chiraldex B-PA column (CSP) was the only one that could separate all eight stereoisomers of derivatised 3,7-dimethylundecan-2-ol, 3,7-dimethyldodecan-2-ol, and 3,7-dimethyltridecan-2-ol. To determine the stereoisomeric purity of standard solutions used in field experiments and extracts of different species of insects the optimised methods were applied. For extracts from B. anynana, Euglossa and Neodiprion lecontei this work describe the first determination of the stereochemistry of some of their semiochemicals. For the determination of the stereochemistry of chiral semiochemicals the methods for purification and separation presented herein have shown to be of great value. The results will hopefully contribute to a better understanding of the communication among insects, and ultimately to a more environmentally friendly pest control.Många naturligt förekommande kemiska ämnen finns som två spegelbilder av varandra, ungefär som höger och vänster hand. Dessa kan ha helt olika egenskaper och det är därför viktigt att kunna separera dem. Insekter och andra djur använder olika doftämnen för att kommunicera med varandra, om det är inom samma art kallas de för feromoner. De kan bestå av ett ämne eller en blandning av flera. Dessa doftämnen kan man även använda för att på ett miljövänligt sätt bekämpa skadeinsekter. En fälla med syntetiskt feromon för en viss insekt lockar endast till sig den arten, medan alla andra är opåverkade. Eftersom dessa ämnen ofta finns som spegelbilder där kanske bara den ena är aktiv och den andra rent av frånstötande, måste man kunna separera dem för att framställa ett syntetiskt feromon som är attraktivt. Målet med detta arbete har varit att bestämma feromonet hos olika arter av tallsteklar som kan vara svåra skadedjur på tallskog. De metoder som tagits fram har även tillämpats på några arter av afrikanska fjärilar samt orkidébin från Centralamerika eftersom de använder snarlika doftämnen. Att få fram feromonet från en insekt är lite som att leta efter in nål i en höstack eftersom de ofta bara innehåller några miljarddels gram per individ. Provet behöver först renas, och en del av arbetet i det här projektet har gått ut på att ta fram en lämplig reningsmetod. Huvudfokus har dock varit på att ta fram metoder som kan separera och identifiera det eller de ämnen, och spegelbilder av dessa, som doftämnena består av. När lämpliga metoder tagits fram har extrakt av olika insektsarter analyserats. I några fall är det första gången som deras feromon bestämts i detalj. Resultaten kan förhoppningsvis bidra till en ökad kunskap om insekters sätt att kommunicera, och i slutändan till miljövänligare bekämpning av skadeinsekter.
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Walz, Sarah [Verfasser], and Oliver [Akademischer Betreuer] Trapp. "Untersuchung interkonvertierender Stereoisomere und Reaktionen höherer Ordnung sowie Bestimmung der kritischen Mizellbildungskonzentration mittels Kapillarelektrophorese / Sarah Walz ; Betreuer: Oliver Trapp." Heidelberg : Universitätsbibliothek Heidelberg, 2016. http://d-nb.info/1180616537/34.
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Wang, Xiaozhao. "Enolization Regioselectivity Involving Stereoisomeric 4a-Methyl-5-methoxyperhydrobenzo[7]annulen-2-ones. Studies Toward the Enantioselective Synthesis of Tubiferal A." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1267062098.
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Uematsu, Yukitaka. "The virtue of biaryl stereoisomerism in molecular design of chiral phase-transfer catalysts for practical asymmetric synthesis." 京都大学 (Kyoto University), 2006. http://hdl.handle.net/2433/144206.
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Lusebrink, Inka. "Stereoisometrie, Biosynthese und biologische Wirkung des Stenusins, sowie weitere Inhaltsstoffe der Pygidialdrüsen der Kurzflügelkäfer Gattung Stenus (Staphylinidae, Coleoptera) /." Bayreuth, 2007. http://opac.nebis.ch/cgi-bin/showAbstract.pl?sys=000253127.
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Ogier, Lionel. "Synthèse de nouveaux analogues iodés du D-glucose." Université Joseph Fourier (Grenoble), 1998. http://www.theses.fr/1998GRE10264.
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Chez l'homme, de nombreuses pathologies sont liees a des dysfonctionnements du transport cellulaire du d-glucose. Les techniques d'imagerie etant un outil precieux pour detecter ces anomalies de transport, la synthese d'analogues du d-glucose radiomarques a l'iode (emetteur gamma) et utilisables en imagerie spect, a ete entreprise selon deux approches : la premiere repose sur l'utilisation du motif beta-iodoethoxyle qui a ete introduit sur diverses positions (1, 4, 5 et 6) du glucose. La seconde consiste a conserver tous les hydroxyles du glucose en introduisant le motif iode a partir des carbones du squelette. Ceci a ete effectue avec un motif iodomethyle sur les positions 3 et 6 ainsi que para-iodophenyle sur cette derniere. Tous les derives prepares ont fait l'objet d'une evaluation biologique, au moins preliminaire, sans toutefois presenter les proprietes d'un traceur du d-glucose, a l'exception du 6-deoxy-6-iodo-d-glucose (6-dig). Ce dernier, dont l'evaluation biologique sera poursuivie, a pu etre prepare a une echelle multi-grammes.
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Lagrange, Fabrice. "Diffusion transplacentaire des stéréo-isomères du kétoprofène." Bordeaux 2, 1996. http://www.theses.fr/1996BOR2P071.
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Wen, Yuexiang. "Remediation of mixed contaminants (polycyclic aromatic hydrocarbons and heavy metals) in soil with the s,s- stereoisomer of ethylenediaminedisuccinic acid and Brij98`." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=95136.
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The efficiencies of extraction with the [S,S]-stereoisomer of ethylenediaminedisuccinic acid ([S,S]-EDDS) on selected toxicants were investigated. A soil washing procedure to solubilize mixed contaminants, polycyclic aromatic hydrocarbon (PAH) compounds and heavy metals from soil, into an aqueous mobilizing solution containing 0.1 M EDDS-6% (V/V) Brij98 was optimized and evaluated. The optimized procedure with EDDS had mobilized a total of 101% of B[a]P burden from the soil after nine successive equilibrations with the same charge of mobilization aids (complexing reagent plus surfactant), which was 21% higher than analogous extractions with the equivalent quantity of EDTA and 28% higher than extractions in the absence of complexing reagent (surfactant Brij98 alone). In contrast to B[a]P, chrysene recovery was not affected appreciably by the presence of the EDDS reagent. Modelling of the extraction process for PAH compounds remaining within the soil revealed that B[a]P was extracted more efficiently in the presence of EDDS, i.e. the number of washes needed to reduce the initial concentration of B[a]P by half was less than the predicted number of washes in the presence of EDTA or Brij98, and the differences were significant at the 95% level of confidence. EDDS also had an appreciable influence on heavy metal exraction efficiency. Most analyte metals, (Al, As, Cd, Cr, Cu, Fe, Ni, Pb and Zn,) were extracted more efficiently in the presence of EDDS than in the presence of an equivalent quantity of EDTA or in the absence of complexing reagent. By contrast, the mobilization of Ca, Mg, and Mn by EDDS was decreased when compared with EDTA and/or surfactant alone.Les efficacités d'extraction choisis avec le stéréoisomère [S,S] de l'acide éthylènediaminedisuccinique ([S,S] - EDDS) sur des produits toxiques sélectionnées ont été étudiées. Un procédé de lavage a été optimisé et évalué pour solubiliser simultanément les composés aromatiques polycycliques de l'hydrocarbure (APH) et les métaux lourds du sol, dans une solution de mobilisation aqueuse contenant 0.1 M EDDS-6% (V/V) Brij98. Le procédé optimisé avec l'agent chélateur EDDS a mobilisé du sol un total de 101% de B [a] P après neuf extractions successifs. Comparativement, quand les expériences ont été réalisée avec EDTA ou sans l'adition d'agent complexant (seulement agent tensio-actif Brij 98), l'EDDS augment la efficacité un 21% par rapport à EDTA et 28% à la solution traitante en absence de agente complexant. Cependant, l'extraction de chrysène n'a pas été sensiblement affectée par la présence du réactif chélateur EDDS. La modélisation du processus d'extraction pour des composés organiques, APH, qui restent dans le sol a indiqué que B [a] P a été extraite plus efficacement en présence d'EDDS, c.-à-d. le nombre de lavages requis pour réduire la concentration initiale de B [a] P à la moitié était moins que le nombre prévu de lavages en présence d'EDTA ou de Brij98 seulement, et les différences étaient significatives au niveau de 95% de la confiance. L'EDDS a également eu une influence appréciable sur l'efficacité d'extraction de métaux lourds. La plupart des métaux analysés, (Al, As, Cd, Cr, Cu, Fe, Ni, Pb et Zn,) ont été extraits plus efficacement en présence d'EDDS qu'en présence d'une quantité équivalente d'EDTA ou en l'absence du réactif complexant. Néanmoins, l'extraction du Ca, du magnésium, et du manganèse par EDDS ont été diminués en comparaison avec seuls l'EDTA et/ou l'agent tensio-actif. fr
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Konarski, Stefan [Verfasser]. "Quantenchemische Untersuchungen zu stereoisomeren Nickel-Bis-(2-phosphanylphenolato)-Chelatkomplexen und zur chemischen Verschiebung von 1H-Inden-Dimeren / Stefan Konarski." Dortmund : Universitätsbibliothek Technische Universität Dortmund, 2005. http://d-nb.info/1011533235/34.
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Duchesne, Jean-Pierre. "Nouvelle voie d'acces aux aldehydes terpeniques : synthese stereoselective des isomeres 11-trans du retinal a l'aide de sulfones." Paris 6, 1987. http://www.theses.fr/1987PA066347.
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Shakirullah, Mohammad. "Oxygenation et degradation du polymere, decoloration du sensibilisateur lors de la photooxygenation du polybutadiene-1,4 cis sensibilisee par les colorants." Université Louis Pasteur (Strasbourg) (1971-2008), 1987. http://www.theses.fr/1987STR13081.
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Sous l'influence conjuguee de la lumiere et de l'oxygene, une solution de polymere et de bleu de methylene subit plusieurs transformations. La photooxygenation conduit uniquement a des hydroperoxydes allergiques: interaction entre l'etat triplet du bleu de methylene et les groupes hydroperoxydes portes par les chaines macromoleculaires. Cinetique et mecanisme
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Kröner, Dominik (Dr rer nat ). "Analysis and control of light-induced processes in molecules: Electron and nuclear quantum dynamics for aspects of stereoisomerism and spectroscopy." Thesis, Universität Potsdam, 2013. http://opus.kobv.de/ubp/volltexte/2014/7047/.
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The habilitation thesis covers theoretical investigations on light-induced processes in molecules. The study is focussed on changes of the molecular electronic structure and geometry, caused either by photoexcitation in the event of a spectroscopic analysis, or by a selective control with shaped laser pulses. The applied and developed methods are predominantly based on quantum chemistry as well as on electron and nuclear quantum dynamics, and in parts on molecular dynamics. The studied scientific problems deal with stereoisomerism and the question of how to either switch or distinguish chiral molecules using laser pulses, and with the essentials for the simulation of the spectroscopic response of biochromophores, in order to unravel their photophysics. The accomplished findings not only explain experimental results and extend existing approaches, but also contribute significantly to the basic understanding of the investigated light-driven molecular processes. The main achievements can be divided in three parts:
First, a quantum theory for an enantio- and diastereoselective or, in general, stereoselective laser pulse control was developed and successfully applied to influence the chirality of molecular switches. The proposed axially chiral molecules possess different numbers of "switchable" stable chiral conformations, with one particular switch featuring even a true achiral "off"-state which allows to enantioselectively "turn on" its chirality. Furthermore, surface mounted chiral molecular switches with several well-defined orientations were treated, where a newly devised highly flexible stochastic pulse optimization technique provides high stereoselectivity and efficiency at the same time, even for coupled chirality-changing degrees of freedom. Despite the model character of these studies, the proposed types of chiral molecular switches and, all the more, the developed basic concepts are generally applicable to design laser pulse controlled catalysts for asymmetric synthesis, or to achieve selective changes in the chirality of liquid crystals or in chiroptical nanodevices, implementable in information processing or as data storage.
Second, laser-driven electron wavepacket dynamics based on ab initio calculations, namely time-dependent configuration interaction, was extended by the explicit inclusion of magnetic field-magnetic dipole interactions for the simulation of the qualitative and quantitative distinction of enantiomers in mass spectrometry by means of circularly polarized ultrashort laser pulses. The developed approach not only allows to explain the origin of the experimentally observed influence of the pulse duration on the detected circular dichroism in the ion yield, but also to predict laser pulse parameters for an optimal distinction of enantiomers by ultrashort shaped laser pulses. Moreover, these investigations in combination with the previous ones provide a fundamental understanding of the relevance of electric and magnetic interactions between linearly or non-linearly polarized laser pulses and (pro-)chiral molecules for either control by enantioselective excitation or distinction by enantiospecific excitation.
Third, for selected light-sensitive biological systems of central importance, like e.g. antenna complexes of photosynthesis, simulations of processes which take place during and after photoexcitation of their chromophores were performed, in order to explain experimental (spectroscopic) findings as well as to understand the underlying photophysical and photochemical principles. In particular, aspects of normal mode mixing due to geometrical changes upon photoexcitation and their impact on (time-dependent) vibronic and resonance Raman spectra, as well as on intramolecular energy redistribution were addressed. In order to explain unresolved experimental findings, a simulation program for the calculation of vibronic and resonance Raman spectra, accounting for changes in both vibrational frequencies and normal modes, was created based on a time-dependent formalism. In addition, the influence of the biochemical environment on the electronic structure of the chromophores was studied by electrostatic interactions and mechanical embedding using hybrid quantum-classical methods. Environmental effects were found to be of importance, in particular, for the excitonic coupling of chromophores in light-harvesting complex II. Although the simulations for such highly complex systems are still restricted by various approximations, the improved approaches and obtained results have proven to be important contributions for a better understanding of light-induced processes in biosystems which also adds to efforts of their artificial reproduction.Die Habilitationsschrift behandelt theoretische Untersuchungen von durch Licht ausgelösten Prozessen in Molekülen. Der Schwerpunkt liegt dabei auf Veränderungen in der Elektronenstruktur und der Geometrie der Moleküle, die durch Bestrahlung mit Licht entweder bei einer spektroskopischen Untersuchung oder bei gezielter Kontrolle durch geformte Laserpulse herbeigeführt werden. Um die dabei auftretende Elektronen- und Kerndynamik zu simulieren, wurden vornehmlich quantentheoretische Methoden eingesetzt und weiterentwickelt. Die wissenschaftlichen Fragestellungen beschäftigen sich mit dem gezielten Verändern und dem Erkennen der räumlichen Struktur von Molekülen ohne Drehspiegelachse, der sog. molekularen Chiralität, sowie mit durch Licht eingeleiteten Prozessen in biologisch relevanten Pigmenten auf sehr kurzen Zeitskalen. Die entwickelten Ansätze und gewonnenen Erkenntnisse lassen sich drei Haupterfolge unterteilen: Erstens gelang die Entwicklung einer generellen Kontrolltheorie für das Ein- und Umschalten von molekularer Chiralität mit geformten Laserpulsen. Dabei wird die räumliche Struktur der vorgeschlagenen molekularen Schalter zwischen ihren stabilen sog. stereoisomeren Formen selektiv geändert, was sich auf ihre optischen und chemischen Eigenschaften auswirkt. Für komplexere Bedingungen, wie z.B. auf einer Oberfläche verankerten molekularen Schaltern verschiedener Orientierung, wurde eine neue Pulsoptimierungsmethode basierend auf Wahrscheinlichkeiten und Statistik entwickelt. Solche laserpulskontrollierten chiralen molekularen Schalter hofft man u.a. in der Nanotechnologie zum Einsatz zu bringen, wo sie z.B. als Informationsspeicher dienen könnten. Zweitens konnte geklärt werden, welche die wesentlichen Einflüsse sind, die das Erkennen von sog. Enantiomeren, das sind spiegelbildliche Moleküle von entgegengesetzter Chiralität, nach Ionisierung durch ultrakurze zirkular polarisierte Laserpulse ermöglichen. Diese Form des sog. Zirkulardichroismus in der Ionenausbeute erlaubt die quantitative und qualitative Unterscheidung von Enantiomeren in der Massenspektrometrie. Durch Simulation der Elektronendynamik während der Laseranregung konnte u.a. erstmals gezeigt werden, dass neben der Zirkularpolarisation der Laserpulse vor allem die schwachen magnetischen Wechselwirkungen für die Unterscheidung entscheidend sind. Drittens wurden die Spektren von in der Natur vorkommenden Pigmenten simuliert, welche u.a. an wichtigen biologischen Funktionen, wie dem Sammeln von Sonnenenergie für die Photosynthese, beteiligt sind. Die Lichtanregung führt dabei zu einer Veränderung der Elektronenstruktur und Geometrie der Pigmente, wobei letzteres wichtige Konsequenzen für die Verteilung der Energie auf die spektroskopisch beobachteten Molekülschwingungen mit sich bringen. Auch der wichtige Einfluss der biochemischen Umgebung auf die Elektronenstruktur der Pigmente bzw. den Energietransfer zwischen solchen wurde untersucht. Neben der Klärung experimenteller Ergebnisse ermöglichen die Untersuchungen neue Einblicke in die fundamentalen Prozesse kurz nach der Lichtanregung -- Erkenntnisse, die auch für die technische Nachahmung der biologischen Funktionen von Bedeutung sein können.
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Nörenberg, Svenja [Verfasser], Karl-Heinz [Akademischer Betreuer] Engel, Karl-Heinz [Gutachter] Engel, and Peter [Gutachter] Schieberle. "Analysis and sensory evaluation of the stereoisomers of 4-mercapto-2-alkanols / Svenja Nörenberg ; Gutachter: Karl-Heinz Engel, Peter Schieberle ; Betreuer: Karl-Heinz Engel." München : Universitätsbibliothek der TU München, 2018. http://d-nb.info/1166315096/34.
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Salgado, Paula Regina Rodrigues. "Estereoisômeros da epóxi-carvona com atividade anticonvulsivante: um estudo comparativo." Universidade Federal da Paraíba, 2016. http://tede.biblioteca.ufpb.br:8080/handle/tede/8268.
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The epoxy-carvone (EC) is a monoterpene present in herbs with proven pharmacological activity in the CNS, including, antinociceptive and anticonvulsant. This substance has chiral centers that permit the generation of four stereoisomers, called (+)-cis-EC, (-)-cis-EC, (+)-trans-EC and (-)-trans-EC, whose comparative anticonvulsant effects have never been studied. This work aims to investigate in a comparative way the anticonvulsant activity of enantiomers of EC cited in experimental models of chemical and electrical induction of seizures in mice and quantifying pro-inflammatory cytokines and perform histopathological analysis of the treated animals. In the test of the seizures induced by pentylenetetrazol, all stereoisomers tested (300 mg/kg; ip) were effective in protecting seizures, increasing the latency for appearances thereof. Since the test of the seizures induced by pilocarpine, substances (+)-cis-EC, (+)-trans-EC and (-)-trans-EC were most prominent in the reduction of parameters related to the activation of cholinergic receptors, and increase the latency to onset of seizures. No significant results were obtained in the test of seizures induced by strychnine, suggesting that possibly these drugs do not act in glycine receptors. In the maximum atrial electroshock model, difference was evident in the effect of EC stereoisomers and despite all reduce the duration of significantly convulsions, substances (+)-trans-EC and (-)-trans-EC showed a reduction even more pronounced. In the kindling test, (+)-cis-EC and (-)-cis-EC reduced the average scores presented with a small but noticeable, especially (+)-cis-EC. The stereoisomer (+)-cis-EC decreased levels of proinflammatory cytokines IL-1β, IL-6 and TNFα in the kindling test, whereas comparatively (-)-cis-EC did not reduce the amount of IL -1β. Histopathological analysis showed greater hippocampal neuronal protection for those treated with (+)-cis-EC. The group treated with (-)-cis-CE exhibited inflammatory components in this tissue, which again lists (+)-cis-EC as a promising, compared. Thus, these results show that the EC stereoisomers has similar anticonvulsant potential, especially (+)-cis-EC, which interferes possibly potentiating inhibitory pathways or inhibiting excitatory pathways, in addition to changing levels of cytokines involved in epileptic condition and promote neuronal protection mechanisms that require further investigation.
A epóxi-carvona (EC) é um monoterpeno presente em plantas aromáticas com atividades farmacológicas já comprovadas no sistema nervoso central, entre elas, antinociceptiva e anticonvulsivante. Esta substância apresenta centros quirais que possibilitam a geração de quatro estereoisômeros, denominados (+)-cis-EC, (-)-cis-EC, (+)-trans-EC e (-)-trans-EC, cujos efeitos anticonvulsivantes comparativos nunca foram estudados. Este trabalho visa investigar de forma comparativa a atividade anticonvulsivante dos citados estereoisômeros da EC em modelos experimentais de indução química e elétrica de convulsão em camundongos, bem como quantificar citocinas pró-inflamatórias e realizar análise histopatológica dos animais tratados. No teste das convulsões induzidas pelo pentilenotetrazol, todos os estereoisômeros testados (300 mg/kg; i.p.) foram efetivos na proteção das convulsões, aumentando a latência para surgimentos das mesmas. Já no teste das convulsões induzidas pela pilocarpina, as substâncias (+)-cis-EC, (+)-trans-EC e (-)-trans-EC tiveram maior destaque na redução de parâmetros relacionados à ativação de receptores colinérgicos, além de aumentarem a latência para início das convulsões. Não foram obtidos resultados significativos no teste das convulsões induzidas pela estricnina, sugerindo-se que possivelmente estas drogas não atuem em receptores de glicina. No modelo do eletrochoque auricular máximo, evidenciou-se diferença no efeito dos estereoisômeros da EC e apesar de todos reduzirem a duração das convulsões de forma significativa, as substâncias (+)-trans-EC e (-)-trans-EC apresentaram uma redução ainda mais acentuada. No teste do “kindling”, (+)-cis-EC e (-)-cis-EC reduziram a média dos escores apresentados, com pequeno mas visível destaque para (+)-cis-EC. O estereoisômero (+)-cis-EC diminuiu os níveis das citocinas pró-inflamatórias IL-1β, IL-6 e TNFα no teste do “kindling”, enquanto, comparativamente, (-)-cis-EC não reduziu a quantidade de IL-1β. A análise histopatológica do hipocampo evidenciou proteção neuronal maior para os tratados com (+)-cis-EC. O grupo que recebeu (-)-cis-EC exibiu componentes inflamatórios neste tecido, o que elenca mais uma vez (+)-cis-EC como promissor, comparativamente. Sendo assim, esses resultados mostram que os estereoisômeros da EC tem similar potencial anticonvulsivante, com destaque para (+)-cis-EC, que possivelmente interfere potencializando vias inibitórias ou inibindo vias excitatórias, além de alterar os níveis de citocinas envolvidas no processo epileptogênico e promover proteção neuronal por mecanismos que requerem maiores investigações
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Yan, Hongmei. "Stereoselective transport of drugs across the blood-brain barrier (BBB) in vivo and in vitro : pharmacokinetic and pharmacodynamic studies of the (S)- and (R)-enantiomers of different 5-HT₁A receptor agonists and antagonists /." Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2002. http://publications.uu.se/theses/91-554-5280-9/.
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Carvalho, Teresa Maria de Jesus Ponte. "Influência do diabetes mellitus gestacional na disposição cinética e metabolismo estereosseletivos do labetalol em pacientes com hipertensão arterial." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/60/60134/tde-13072009-151617/.
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O labetalol, um anti-hipertensivo considerado seguro para uso em gestantes, está disponível na clínica como mistura de dois racematos (quatro estereoisômeros), sendo o isômero (R,R) antagonista e o (S,R) responsável pela atividade bloqueadora. O estudo investiga a influência do diabetes mellitus gestacional (DMG) na disposição cinética e no metabolismo estereosseletivos do labetalol administrado por via endovenosa ou oral. Foram investigadas 30 gestantes hipertensas distribuídas em 04 grupos: não diabéticas tratadas com dose única de 40 mg de cloridrato de labetalol endovenoso (grupo EVH, n=8) ou 100 mg de cloridrato de labetalol via oral (grupo VOH, n=9) e diabéticas tratadas com 40 mg de cloridrato de labetalol endovenoso (grupo EVD, n=6) ou 100 mg de cloridrato de labetalol via oral (grupo VOD, n=7). As amostras seriadas de sangue foram coletadas até 12 h (via oral) ou 15 h (via endovenosa) após a administração do cloridrato de labetalol. Os estereoisômeros do labetalol em plasma foram analisados em coluna de fase quiral Chirobiotic V empregando LC-MS-MS. Os parâmetros farmacocinéticos do labetalol inalterado e labetalol glicuronídeo foram calculados com auxílio do programa WinNonlin e avaliados empregando os testes de Mann-Whitney e Friedman com pós-teste de Dunn (p<0,05). A farmacocinética do labetalol não é estereosseletiva em gestantes diabéticas e não diabéticas tratadas com o fármaco por via endovenosa. No entanto, a administração oral de labetalol resulta em menores valores de área sob a curva concentração plasmática versus tempo (AUC) para o isômero ativo (R,R)-labetalol tanto em gestantes diabéticas (60,9 vs 162,7 vs 157,9 vs 114,6 ng.h/mL, respectivamente para (R,R,); (SR); (S,S,) e (R,S)) quanto não diabéticas (45,6 vs 84,2 vs 89,4 vs 78,3 ng.h/mL, respectivamente para (R,R,); (SR); (S,S,) e (R,S)). O DMG resulta em alterações na disposição cinética dos estereoisômeros do labetalol na administração oral. Os valores de AUC do isômero inativo (S,S)-labetalol (157,9 vs 89,4 ng.h/mL) e para o isômero -bloqueador (S,R)-labetalol (162.7 vs 84.2 ng.h/mL) são maiores (p<0,05) nas gestantes diabéticas do que nas gestantes não diabéticas. As gestantes diabéticas também mostram maior biodisponibilidade oral do isômero (S,R)-labetalol (54,7 vs 24,0 %) explicada pela reduzida eliminação pré-sistêmica conseqüente da menor capacidade de conjugação com o ácido glicurônico (68,4 vs 77,9 %). Os valores de AUC do isômero (S,R) aproximadamente 100 % maiores nas gestantess diabéticas tratadas com o fármaco por via oral (162,7 vs 84,2 ng.h/mL) pode ter relevância clínica considerando a atividade -bloqueadora do referido isômero.Labetalol, a hypertensive agent considered to be safe for use by pregnant women, is clinically available as a mixture of two racemates, with the (R,R) isomer being a antagonist and the (S,R) isomer being responsible for the blocking activity. The study investigated the influence of gestational diabetes mellitus (GDM) on the kinetic disposition and stereoselective metabolism of labetalol administered by the intravenous or oral route. Thirty hypertensive pregnant women were divided into 4 groups: non-diabetic women treated with a single 40 mg dose of intravenous labetalol hydrochloride (IVH group, n=8) or with 100 mg labetalol hydrochloride by the oral route (OH group, n=9) and diabetic women treated with 40 mg intravenous labetalol hydrochloride (IVD), n=6) or with 100 mg labetalol hydrochloride by the oral route (OD, n=7). Serial blood samples were collected up to 12 h (oral route) or 15 h (intravenous route) after the administration of labetalol hydrochloride. The labetalol stereoisomers in plasma were analyzed with a chiral phase Chirobiotic V column by LC-MS-MS. The pharmacokinetic parameters of unchanged labetalol and glucuronide labetalol were calculated using the WinNolin software and analyzed by the Mann-Whitney and Friedman tests followed by the Dunn test (p<0.05). The pharmacokinetics of labetalol was not stereoselective in diabetic or non-diabetic pregnant women treated with the drug by the intravenous route. However, oral administration of labetalol resulted in lower values of the area under the plasma concentration versus time curve (AUC) for the active isomer (R,R)-labetalol both in diabetic (60.9 vs 162.7 vs 157.9 vs 114.6 ng.h/mL, respectively for (R,R,), (SR), (S,S,) and (R,S)) and non-diabetic pregnant women (45.6 vs 84.2 vs 89.4 vs 78.3 ng.h/mL, respectively for (R,R,), (SR), (S,S,) and (R,S)). GDM involves changes in the kinetic disposition of the stereoisomers of labetalol when administered by the oral route. The AUC values for the inactive (S,S)-labetalol (157.9 vs 89.4 ng.h/mL) and for the -blocking (S,R) isomer (162.7 vs 84.2 ng.h/mL) were higher (p<0.05) for the diabetic than the non-diabetic pregnant women. The diabetic pregnant women showed greater oral bioavailability of the (S,R)-labetalol isomer (54.7 vs 24.0 %), explained by the reduced pre-systemic elimination due to the lower capacity for conjugation with glucuronic acid (68.4 vs 77.9 %). The approximately 100 % higher AUC values of the (S,R) isomer for the diabetic pregnant women treated with the drug by the oral route may be of clinical relevance in view of the -blocking activity of the isomer in question.
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Gravier-Pelletier, Christine. "Synthese du leucotriene enantiomeriquement pru ltb quatre et d'un analogue a partir du d-manniotol." Paris 6, 1986. http://www.theses.fr/1986PA066507.
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Leppchen, Kathrin. "Anwendung von Saccharomyces cerevisiae in der Biotechnologie und Oberflächenchemie /." München : Verl. Dr. Hut, 2009. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=017317794&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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