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Academic literature on the topic 'Stereoisomeri'

Author: Grafiati
Published: 11 March 2023

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Journal articles on the topic "Stereoisomeri"

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Costa, Maria L. M., Miguel Borges, Evaldo F. Vilela, Paulo de Marco Jr, and Eraldo R. Lima. "Effect of stereoisomers of the main component of the sex pheromone of Euschistus heros (F.) (Hemiptera: Pentatomidae) in the attractiveness of females." Anais da Sociedade Entomológica do Brasil 29, no. 3 (September 2000): 413–22. http://dx.doi.org/10.1590/s0301-80592000000300004.

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The attractiveness of Euschistus heros (F.) (Hemiptera: Pentatomidae) females to the eight stereoisomers of the methyl 2,6,10-trimethyltridecanoate, major component of the sex pheromone produced by the males of this species, was studied in a double choice olfactometer. Bioassays showed that the (2R, 6R, 10S) stereoisomer was necessary for the attractiveness of females, presenting better results in relation to the others. The stereoisomeric mixture was shown to present significative attractiveness to females, however, when compared to the (2R, 6R, 10S) stereoisomer, it showed lower attractiveness.
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Lapčík, Oldřich, Richard Hampl, Martin Hill, Luboslav Stárka, Alexander Kasal, Vladimír Pouzar, and Zdeněk Putz. "Radioimmunological and Chromatographic Properties of Tyrosine Methyl Ester Conjugates with Stereoisomeric Steroid Carboxy Derivatives." Collection of Czechoslovak Chemical Communications 61, no. 5 (1996): 799–807. http://dx.doi.org/10.1135/cccc19960799.

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Pure 3Z (syn) and 3E (anti) stereoisomers of testosterone 3-[O-(2-carboxyethyl)]oxime were synthesized, separated by HPLC or TLC, and used for preparation of tyrosine methyl ester (TME) conjugates by using mixed anhydride or carbodiimide-N-hydroxysuccinimide methods. While the latter method provided more than 96% of product with retained configuration, the mixed anhydride method yielded a mixture containing 26-40% of the opposite stereoisomer. The stereoisomers were used as model compounds, to which the other steroid TMEs and the corresponding radioiodinated products could be aligned according to their chromatographic properties. The TME conjugates of 3-(O-carboxymethyl)oximes of seven 4-en-3-oxo steroids were further prepared by carbodiimide-N-hydroxysuccinimide method. With exception of cortisol, the stereoisomeric (Z and E) radioiodinated TME conjugates could be separated by TLC. In addition, the conjugates with TME and consequently radioiodinated tracers were synthesized from hemisuccinates of cortisol and its 11α-isomer, via 11β- and 11α-hydroxy group. The radioiodinated conjugates were tested as radioligands with rabbit polyclonal antisera raised by using position-homologous conjugates of the respective steroid carboxy derivatives with bovine serum albumin as immunogens. With the exception of 11-deoxycorticosterone, the stereoisomeric Z and E radioiodinated TMEs did not differ in their binding properties. In the case of isomeric cortisol tracers conjugated through position 11 the antisera recognized only the sterically homologous radioligands, but the specificity of the system was poor.
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3

Kuchan, Matthew J., Søren K. Jensen, Elizabeth J. Johnson, and Jacqueline C. Lieblein-Boff. "The naturally occurring α-tocopherol stereoisomer RRR-α-tocopherol is predominant in the human infant brain." British Journal of Nutrition 116, no. 1 (May 16, 2016): 126–31. http://dx.doi.org/10.1017/s0007114516001719.

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Abstractα-Tocopherol is the principal source of vitamin E, an essential nutrient that plays a crucial role in maintaining healthy brain function. Infant formula is routinely supplemented with synthetic α-tocopherol, a racaemic mixture of eight stereoisomers with less bioactivity than the natural stereoisomer RRR-α-tocopherol. α-Tocopherol stereoisomer profiles have not been previously reported in the human brain. In the present study, we analysed total α-tocopherol and α-tocopherol stereoisomers in the frontal cortex (FC), hippocampus (HPC) and visual cortex (VC) of infants (n 36) who died of sudden infant death syndrome or other conditions. RRR-α-tocopherol was the predominant stereoisomer in all brain regions (P<0·0001) and samples, despite a large intra-decedent range in total α-tocopherol (5–17 μg/g). Mean RRR-α-tocopherol concentrations in FC, HPC and VC were 10·5, 6·8 and 5·5 μg/g, respectively. In contrast, mean levels of the synthetic stereoisomers were RRS, 1–1·5; RSR, 0·8–1·0; RSS, 0·7–0·9; and Σ2S 0·2–0·3 μg/g. Samples from all but two decedents contained measurable levels of the synthetic stereoisomers, but the intra-decedent variation was large. The ratio of RRR:the sum of the synthetic 2R stereoisomers (RRS+RSR+RSS) averaged 2·5, 2·3 and 2·4 in FC, HPC and VC, respectively, and ranged from 1 to at least 4·7, indicating that infant brain discriminates against synthetic 2R stereoisomers in favour of RRR. These findings reveal that RRR-α-tocopherol is the predominant stereoisomer in infant brain. These data also indicate that the infant brain discriminates against the synthetic 2R stereoisomers, but is unable to do so completely. On the basis of these findings, investigation into the impact of α-tocopherol stereoisomers on neurodevelopment is warranted.
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Sheikh, Ishfaq Ahmad, and Mohd Amin Beg. "Structural Aspects of Potential Endocrine-Disrupting Activity of Stereoisomers for a Common Pesticide Permethrin against Androgen Receptor." Biology 10, no. 2 (February 11, 2021): 143. http://dx.doi.org/10.3390/biology10020143.

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Endocrine-disrupting chemicals (EDCs) are a serious global public health and environmental concern. Pyrethroids are insecticide chemicals that are extensively used for crop protection and household purposes but have been identified as EDCs. On account of their ubiquitous environmental presence, human exposure occurs via food, dermal, or inhalation routes and is associated with health problems, including reproductive dysfunction. Permethrin is the most commonly used pyrethroid, and with two chiral centers in its structure, it has four stereoisomeric forms (two enantiomer pairs), i.e., permethrin (1R,3R)-cis, permethrin (1R,3S)-trans, permethrin (1S,3S)-cis, and permethrin (1S,3R)-trans. The current study was performed for predicting the potential endocrine-disrupting activity of the aforementioned four stereoisomers of permethrin against the androgen receptor (AR). The structural binding characterization and binding energy estimations in the AR binding pocket were done using induced fit docking. The structural binding data indicated that all stereoisomers were placed stably in the AR binding pocket and that the estimated binding energy values were comparable to the AR native ligand, except for permethrin (1S,3S)-cis. Furthermore, the commonality in the amino acid interactions to that of the AR native ligand and the binding energy values suggested the potential AR-disrupting activity of all the stereoisomers; however, stereoselective differences were not observed. Taken together, the results suggest that human exposure to permethrin, either as a racemate mixture or in individual stereoisomer form, could potentially interfere with AR function, which may lead to male reproductive dysfunction.
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DIEUAIDE-NOUBHANI, Martine, Stanny ASSELBERGHS, Guy P. MANNAERTS, and Paul P. VAN VELDHOVEN. "Evidence that multifunctional protein 2, and not multifunctional protein 1, is involved in the peroxisomal β-oxidation of pristanic acid." Biochemical Journal 325, no. 2 (July 15, 1997): 367–73. http://dx.doi.org/10.1042/bj3250367.

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The second (enoyl-CoA hydratase) and third (3-hydroxyacyl-CoA dehydrogenase) steps of peroxisomal β-oxidation are catalysed by two separate multifunctional proteins (MFPs), MFP-1 being involved in the degradation of straight-chain fatty acids and MFP-2 in the β-oxidation of the side chain of cholesterol (bile acid synthesis). In the present study we determined which of the two MFPs is involved in the peroxisomal degradation of pristanic acid by using the synthetic analogue 2-methylpalmitic acid. The four stereoisomers of 3-hydroxy-2-methylpalmitoyl-CoA were separated by gas chromatography after hydrolysis, methylation and derivatization of the hydroxy group with (S)-2-phenylpropionic acid, and the stereoisomers were designated I–IV according to their order of elution from the column. Purified MFP-1 dehydrated stereoisomer IV but dehydrogenated stereoisomer III, so by itself MFP-1 is not capable of converting a branched enoyl-CoA into a 3-ketoacyl-CoA. In contrast, MFP-2 dehydrated and dehydrogenated the same stereoisomer (II), so it is highly probable that MFP-2 is involved in the peroxisomal degradation of branched fatty acids and that stereoisomer II is the physiological intermediate in branched fatty acid oxidation. By analogy with the results obtained with the four stereoisomers of the bile acid intermediate varanoyl-CoA, stereoisomer II can be assigned the 3R-hydroxy, 2R-methyl configuration.
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6

Dersjant-Li, Jensen, Bos, and Peisker. "Bio-discrimination of α-tocopherol Stereoisomers in Rearing and Veal Calves Fed Milk Replacer Supplemented with All-rac-α-tocopheryl Acetate." International Journal for Vitamin and Nutrition Research 79, no. 4 (July 1, 2009): 199–211. http://dx.doi.org/10.1024/0300-9831.79.4.199.

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This study evaluated the biological discrimination of different α-tocopherol stereoisomers (i. e. RRR-, RRS-, RSR-, RSS- and the four 2S-α-tocopherols) from all-rac-α-tocopheryl acetate supplementation in milk replacer for rearing and veal calves respectively, in practical farming conditions. Two experiments were conducted. In experiment 1, six rearing calves were fed milk replacer supplemented with 80 mg/kg all-rac-α-tocopheryl acetate for a period of 9 weeks. The calves were supplied calf starter concentrate from 1 to 12 weeks. In experiment 2, six veal calves were fed milk replacer supplemented with 80 mg/kg all-rac-α-tocopheryl acetate for a period of 24 weeks. Blood samples were taken at the start and every 4 weeks until 12 weeks for rearing calves in experiment 1, and until slaughter (24 weeks) for veal calves in experiment 2. Liver, adipose, muscle, and brain samples were taken at slaughter of the six veal calves in experiment 2. The distribution of different α-tocopherol stereoisomers in feed, plasma, and tissues was analyzed. In both experiments, it was observed that RRR-α-tocopherol was the dominant stereoisomer in plasma and tissues. The average percentage of the RRR-α-tocopherol stereoisomer was 64 %, and 39 % of the total α-tocopherol in plasma for rearing and veal calves, respectively. The higher RRR-α-tocopherol stereoisomer proportion as percentage of the total α-tocopherol in rearing calves was related to higher dietary natural vitamin E intake. Other 2R-α-tocopherol stereoisomers had lower utilization efficiency than RRR-α-tocopherol stereoisomer. 2S-α-tocopherol stereoisomers were basically not utilized by calves.
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Tirri, Micaela, Paolo Frisoni, Sabrine Bilel, Raffaella Arfè, Claudio Trapella, Anna Fantinati, Giorgia Corli, et al. "Worsening of the Toxic Effects of (±)Cis-4,4′-DMAR Following Its Co-Administration with (±)Trans-4,4′-DMAR: Neuro-Behavioural, Physiological, Immunohistochemical and Metabolic Studies in Mice." International Journal of Molecular Sciences 22, no. 16 (August 16, 2021): 8771. http://dx.doi.org/10.3390/ijms22168771.

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4,4’-Dimethylaminorex (4,4’-DMAR) is a new synthetic stimulant, and only a little information has been made available so far regarding its pharmaco-toxicological effects. The aim of this study was to investigate the effects of the systemic administration of both the single (±)cis (0.1–60 mg/kg) and (±)trans (30 and 60 mg/kg) stereoisomers and their co-administration (e.g., (±)cis at 1, 10 or 60 mg/kg + (±)trans at 30 mg/kg) in mice. Moreover, we investigated the effect of 4,4′-DMAR on the expression of markers of oxidative/nitrosative stress (8-OHdG, iNOS, NT and NOX2), apoptosis (Smac/DIABLO and NF-κB), and heat shock proteins (HSP27, HSP70, HSP90) in the cerebral cortex. Our study demonstrated that the (±)cis stereoisomer dose-dependently induced psychomotor agitation, sweating, salivation, hyperthermia, stimulated aggression, convulsions and death. Conversely, the (±)trans stereoisomer was ineffective whilst the stereoisomers’ co-administration resulted in a worsening of the toxic (±)cis stereoisomer effects. This trend of responses was confirmed by immunohistochemical analysis on the cortex. Finally, we investigated the potentially toxic effects of stereoisomer co-administration by studying urinary excretion. The excretion study showed that the (±)trans stereoisomer reduced the metabolism of the (±)cis form and increased its amount in the urine, possibly reflecting its increased plasma levels and, therefore, the worsening of its toxicity.
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Cortinas, Lucia, Ana Barroeta, Jaume Galobart, and Søren K. Jensen. "Distribution of α-tocopherol stereoisomers in liver and thigh of chickens." British Journal of Nutrition 92, no. 2 (August 2004): 295–301. http://dx.doi.org/10.1079/bjn20041188.

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The effect of supplementation with different levels of all-rac-α-tocopheryl acetate and the inclusion of different dietary contents of PUFA on the deposition of α-tocopherol stereoisomers in liver and thigh of chickens was evaluated. Ninety-six 1-d-old Ross female broiler chickens were randomly distributed into eight experimental treatments (three replicates each) resulting from four levels of α-tocopheryl acetate without supplementation and supplemented with 100, 200 and 400 mg α-tocopheryl acetate/kg and two levels of dietary PUFA (15 and 61 g/kg). The feeds supplemented with α-tocopheryl acetate contained a similar proportion of each stereoisomer. The diets without α-tocopheryl acetate had the following α-tocopherol stereoisomers (%): RRR 35·1, RRS 24·5, RSR 25·3, RSS 13·9 and total 2S forms 1·3. Consumption of different levels of α-tocopheryl acetate did not lead to statistical differences in α-tocopherol stereoisomer proportion in the liver and thigh. In general, the stereoisomer profiles in the tissues studied were similar, responding to the stereoisomer profile of the diet. Both tissues preferentially accumulated 2R stereoisomer (69–100%). However, when α-tocopheryl acetate was used the discrimination was not specific for the RRR α-tocopherol form. Furthermore, the 2R:2S ratio had a tendency to increase as the polyunsaturation level of the diet increased.
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Hymøller, Lone, Saman Lashkari, Tove N. Clausen, and Søren K. Jensen. "Distribution of α-tocopherol stereoisomers in mink (Mustela vison) organs varies with the amount of all-rac-α-tocopheryl acetate in the diet." British Journal of Nutrition 120, no. 12 (October 17, 2018): 1332–37. http://dx.doi.org/10.1017/s0007114518002878.

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AbstractSynthetic α-tocopherol has eight isomeric configurations including four 2R (RSS, RRS, RSR, RRR) and four 2S (SRR, SSR, SRS, SSS). Only the RRR stereoisomer is naturally synthesised by plants. A ratio of 1·36:1 in biopotency of RRR-α-tocopheryl acetate to all-rac-α-tocopheryl acetate is generally accepted; however, studies indicate that neither biopotency of α-tocopherol stereoisomers nor bioavailability between them is constant, but depend on dose, time, animal species and organs. A total of forty growing young male mink were, after weaning, assigned one of the following treatments for 90 d: no α-tocopherol in diet (ALFA_0), 40 mg/kg RRR-α-tocopheryl acetate (NAT_40), 40 mg/kg all-rac-α-tocopheryl acetate (SYN_40) and 80 mg/kg feed all-rac-α-tocopheryl acetate (SYN_80). Mink were euthanised in CO2 and blood was collected by heart puncture. Mink were pelted and liver, heart, lungs, brain and abdominal fat were collected for α-tocopherol stereoisomer analysis. The proportion of RRR-α-tocopherol decreased in all organs and plasma with increasing amount of synthetic α-tocopherol stereoisomers in the diet (P≤0·05), whereas the proportion of all synthetic α-tocopherol stereoisomers increased with increasing amount of synthetic α-tocopherol stereoisomers in the diet (P≤0·05). The proportion of α-tocopherol stereoisomers in plasma, brain, heart, lungs and abdominal fat showed the following order: RRR>RRS, RSR, RSS>Σ2S, regardless of α-tocopherol supplement. The liver had the highest proportion of Σ2S stereoisomers, and lowest proportion of RRR-α-tocopherol. In conclusion, distribution of α-tocopherol stereoisomers differs with dose and form of α-tocopherol supplementation. The results did also reveal the liver’s role as the major organ for accumulation of Σ2S α-tocopherol stereoisomers.
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Brice-Tutt, Ariana C., Sanjeewa N. Senadheera, Michelle L. Ganno, Shainnel O. Eans, Tanvir Khaliq, Thomas F. Murray, Jay P. McLaughlin, and Jane V. Aldrich. "Phenylalanine Stereoisomers of CJ-15,208 and [d-Trp]CJ-15,208 Exhibit Distinctly Different Opioid Activity Profiles." Molecules 25, no. 17 (September 2, 2020): 3999. http://dx.doi.org/10.3390/molecules25173999.

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The macrocyclic tetrapeptide cyclo[Phe-d-Pro-Phe-Trp] (CJ-15,208) and its stereoisomer cyclo[Phe-d-Pro-Phe-d-Trp] exhibit different opioid activity profiles in vivo. The present study evaluated the influence of the Phe residues’ stereochemistry on the peptides’ opioid activity. Five stereoisomers were synthesized by a combination of solid-phase peptide synthesis and cyclization in solution. The analogs were evaluated in vitro for opioid receptor affinity in radioligand competition binding assays, and for opioid activity and selectivity in vivo in the mouse 55 °C warm-water tail-withdrawal assay. Potential liabilities of locomotor impairment, respiratory depression, acute tolerance development, and place conditioning were also assessed in vivo. All of the stereoisomers exhibited antinociception following either intracerebroventricular or oral administration differentially mediated by multiple opioid receptors, with kappa opioid receptor (KOR) activity contributing for all of the peptides. However, unlike the parent peptides, KOR antagonism was exhibited by only one stereoisomer, while another isomer produced DOR antagonism. The stereoisomers of CJ-15,208 lacked significant respiratory effects, while the [d-Trp]CJ-15,208 stereoisomers did not elicit antinociceptive tolerance. Two isomers, cyclo[d-Phe-d-Pro-d-Phe-Trp] (3) and cyclo[Phe-d-Pro-d-Phe-d-Trp] (5), did not elicit either preference or aversion in a conditioned place preference assay. Collectively, these stereoisomers represent new lead compounds for further investigation in the development of safer opioid analgesics.
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Dissertations / Theses on the topic "Stereoisomeri"

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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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2011/2012
La 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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Books on the topic "Stereoisomeri"

1

Spasov, Alexander A., Igor N. Iezhitsa, Pavel M. Vassiliev, Alexander A. Ozerov, and Renu Agarwal. Pharmacology of Drug Stereoisomers. Singapore: Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-19-2320-3.

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Chromatographic separations of stereoisomers. Boca Raton, Fla: CRC Press, 1985.

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1945-, Smith Donald F., ed. Handbook of stereoisomers--therapeutic drugs. Boca Raton, Fla: CRC Press, 1989.

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Bols, Mikael. Carbohydrate building blocks. New York, NY: J. Wiley, 1996.

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El-Basil, Sherif. Combinatorial organic chemistry: An educational approach. New York: Nova Science Publishers, 1999.

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J, Lough W., and Wainer Irving W, eds. Chirality in natural and applied science. Boca Raton: CRC Press/Blackwell Pub., 2002.

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Eusebio, Juaristi, ed. Enantioselective synthesis of [beta]-amino acids. New York: Wiley-VCH, 1997.

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1936-, Pályi G., Zucchi C. 1964-, Caglioti Luciano, and Interdisciplinary Symposium on Biological Chirality (3rd : 2003 : Modena, Italy), eds. Progress in biological chirality. Amsterdam: Elsevier, 2004.

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Y, Aboul-Enein Hassan, and Wainer Irving W, eds. The impact of stereochemistry on drug development and use. New York: Wiley, 1997.

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Nógrádi, M. Stereoselective synthesis: A practical approach. 2nd ed. Weinheim: VCH, 1995.

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Book chapters on the topic "Stereoisomeri"

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Hazen, Robert. "Stereoisomers." In Encyclopedia of Astrobiology, 1598. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-11274-4_1516.

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Liebscher, Wolfgang, and Ekkehard Fluck. "Stereoisomerie." In Die systematische Nomenklatur der anorganischen Chemie, 290–306. Berlin, Heidelberg: Springer Berlin Heidelberg, 1999. http://dx.doi.org/10.1007/978-3-642-58368-1_8.

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Gooch, Jan W. "Stereoisomers." In Encyclopedic Dictionary of Polymers, 700. New York, NY: Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4419-6247-8_11208.

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Morgan, Michael M., MacDonald J. Christie, Luis De Lecea, Jason C. G. Halford, Josee E. Leysen, Warren H. Meck, Catalin V. Buhusi, et al. "Stereoisomers." In Encyclopedia of Psychopharmacology, 1283–84. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-540-68706-1_1144.

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Hazen, Robert. "Stereoisomers." In Encyclopedia of Astrobiology, 2376–77. Berlin, Heidelberg: Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-662-44185-5_1516.

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Latscha, Hans Peter, and Helmut Alfons Klein. "Stereoisomerie." In Springer-Lehrbuch, 356–69. Berlin, Heidelberg: Springer Berlin Heidelberg, 1991. http://dx.doi.org/10.1007/978-3-642-85882-6_20.

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Schmiermund, Torsten. "Stereoisomerie." In essentials, 17–21. Wiesbaden: Springer Fachmedien Wiesbaden, 2019. http://dx.doi.org/10.1007/978-3-658-28087-1_4.

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Vollhardt, Peter, and Neil Schore. "Stereoisomers." In Organic Chemistry, 286–365. New York: Macmillan Learning, 2014. http://dx.doi.org/10.1007/978-1-319-19197-9_5.

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Hazen, Robert. "Stereoisomers." In Encyclopedia of Astrobiology, 1. Berlin, Heidelberg: Springer Berlin Heidelberg, 2014. http://dx.doi.org/10.1007/978-3-642-27833-4_1516-4.

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Nahler, Gerhard. "stereoisomer." In Dictionary of Pharmaceutical Medicine, 174–75. Vienna: Springer Vienna, 2009. http://dx.doi.org/10.1007/978-3-211-89836-9_1332.

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Conference papers on the topic "Stereoisomeri"

1

Yamauchi, S., Y. Imai, H. Yokota, and M. Tonouchi. "Determination of stereoisomer in sugars by THz-TDS." In International Commission for Optics (ICO 22), edited by Ramón Rodríguez-Vera and Rufino Díaz-Uribe. SPIE, 2011. http://dx.doi.org/10.1117/12.902044.

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Grenier, Pierre-Anthony, Luc Brun, and Didier Villemin. "Taking into account stereoisomerism in the prediction of molecular properties." In 2016 23rd International Conference on Pattern Recognition (ICPR). IEEE, 2016. http://dx.doi.org/10.1109/icpr.2016.7899856.

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Ferrarini, Renan S., Alcindo A. Dos Santos, and João V. Comasseto. "Total Synthesis of Four Stereoisomers of Acaterin through a Te/Li Exchange Protocol." In 14th Brazilian Meeting on Organic Synthesis. São Paulo: Editora Edgard Blücher, 2013. http://dx.doi.org/10.5151/chempro-14bmos-r0199-1.

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Soldi, Rafael A., and Paulo H. G. Zarbin. "Synthesis of all possible stereoisomers of 6,10,13- trimethyltetradecan-2-one, male-produced sex pheromone of Pallantia macunaima." In 15th Brazilian Meeting on Organic Synthesis. São Paulo: Editora Edgard Blücher, 2013. http://dx.doi.org/10.5151/chempro-15bmos-bmos2013_201391512371.

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K.L., Narasimha Swamy, and Chandan Dasgupta. "Investigating the Nature of Students' Reasoning in Connecting Molecular Structures of Stereoisomers with their Physical Properties Using an AR App." In 2018 IEEE Ninth International Conference on Technology for Education (T4E). IEEE, 2018. http://dx.doi.org/10.1109/t4e.2018.00018.

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Sonstrom, Reilly, W. Harman, Jacob Smith, Brooks Pate, Chris Pede, Umme Hossain, and Jate Bernard. "THE APPLICATION OF MOLECULAR ROTATIONAL SPECTROSCOPY TO ANALYZE REGIO- AND STEREOISOMERS OF CYCLOHEXENE PRODUCED FROM REACTIONS OF A TUNGSTEN BENZENE COMPLEX." In 74th International Symposium on Molecular Spectroscopy. Urbana, Illinois: University of Illinois at Urbana-Champaign, 2019. http://dx.doi.org/10.15278/isms.2019.mh03.

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Ghavami, Ahmad, Blair D. Johnston, Morten T. Jensen, Birte Svenson, and Morten B. Mario Pinto. "SYNTHESIS OF A NEW CLASS OF GLYCOSIDASE INHIBITORS: SALACINOL, ITS STEREOISOMERS, AND NITROGEN AND SELENIUM ANALOGUES, AND THEIR EVALUATION AS GLYCOSIDASE INHIBITORS." In XXIst International Carbohydrate Symposium 2002. TheScientificWorld Ltd, 2002. http://dx.doi.org/10.1100/tsw.2002.510.

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Oliveira, C. R., T. A. Barra, V. B. Pereira, G. R. S. G. Salgueiro, and D. A. Azevedo. "Overview of the Cheilanthane Stereoisomer Series from Brazilian Pre-Salt and Post-Salt Crude Oils by Gc/Qqq-Ms and Gc×Gc-Tofms." In 29th International Meeting on Organic Geochemistry. European Association of Geoscientists & Engineers, 2019. http://dx.doi.org/10.3997/2214-4609.201902984.

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Christie, D. J., H. Diaz-Arauzo, and J. M. Cook. "REACTIONS OF DRUG-DEPENDENT ANTIBODIES WITH METABOLITES OF QUININE (Qn) AND QUINIDINE (Qd)." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644578.

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In many cases of drug-induced immunologic thrombocytopenia (DITP), a metabolite, rather than the native drug, is suspected of provoking the destructive drug-dependent antibodies (DDAB) responsible for this severe hemorrhagic disorder. However, this has not previously been investigated for Qn- and Qd-DDAB. We report evidence that the native drugs, and not their metabolites, are the provocative agents in Qn and Qd DITP. Reactions of Qn- and Qd-DDAB with platelets were studied with the native drugs and four of their metabolites: the N-oxide and 10,11-diol derivatives (quinuclidine ring modifications), the des-methyl derivatives (aromatic quinoline ring modification), and 2'-quininone and 2'-quinidinone (2'-oxo derivatives) (also quinoline ring modifications on Qn and Qd, respectively). Five antibodies were studied:two Group 1 DDAB (specific for compounds with native configuration at asymmetric carbon positions), two Group 2 DDAB (similar to Group 1 DDAB but also known to require the methoxy group on the quinuclidine ring for full activity), and one Group 3 DDAB (reactive with the native drug, its stereoisomer, and several nonmetabolic analogs of both compounds) . Using a complement-dependent 51Cr-lysis assay, the reactions of all DDAB with platelets and the four metabolites were similar to 100-fold weaker when compared to reactions obtained with the native drug, with these exceptions:Group 2 DDAB failed to react with the desmethyl and 2'-oxo metabolites and the Group 3 DDAB failed to react with 2'-oxo Qd. This observation shows that the activity of certain DDAB is critically dependent on the native quinoline ring structure. Importantly, none of the DDAB reacted more strongly with any of the metabolites tested when compared with reactions in the presence of the native drug. These findings indicate that DDAB react with platelets preferentially in the presence of the unaltered Qn and Qd molecules and suggest that, while the role of metabolites cannot be entirely ruled out, the native structure of the drug molecule is sufficient to stimulate production of the antibodies responsible for DITP.
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Reports on the topic "Stereoisomeri"

1

Kemnitzer, John E., Stephen P. McCarthy, and Richard A. Gross. Poly(Beta-Hydroxybutyrate) Stereoisomers: A Model Study of the Effects of Stereochemical and Morphological Variables on Polymer Biological Degradability. Fort Belvoir, VA: Defense Technical Information Center, January 1992. http://dx.doi.org/10.21236/ada271046.

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