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Appropriate Substrates (appropriate + substrate)
Selected AbstractsNucleophilic Additions to Cyclic Nitrones en Route to Iminocyclitols , Total Syntheses of DMDP, 6-deoxy-DMDP, DAB-1, CYB-3, Nectrisine, and Radicamine BEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 17 2008Pedro Merino Abstract Highly diastereoselective nucleophilic additions to cyclic nitrones derived from L -malic acid and D -arabinose have been used for the construction of enantiomerically pure polyhydroxylated pyrrolidines. The synthetic strategy adopted was based on an oxidation/reduction protocol involving hydroxylamine/nitrone pairs and demonstrates the use of reagent- and substrate-derived stereocontrol. In most cases reactions took place with total diastereoselectivity and in quantitative yield, with no purification being necessary. By this strategy, 2-(hydroxymethyl)-, 2-(aminomethyl)-, and 2-aryl-substituted polyhydroxylated pyrrolidines have been prepared with abundant configurational diversity. The use of appropriate substrates and reagents allowed for approaches to DMDP, 6-deoxy-DMDP, DAB-1, CYB-3, nectrisine and radicamine B. Several analogues of these compounds with inverted configuration at one or more stereocenters were also prepared.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] In vitro testing to assess the UVA protection performance of sun care productsINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 1 2001Applied Cosmetics) Task Force, Members of the DGK (German Society for Scientific, Sun Protection'. Synopsis The UVA protection delivered by sunscreens is an issue of increasing importance due to the increasing knowledge about UVA-induced skin damage. In Europe there is no officially accepted method available to determine the degree of UVA protection. Therefore, the objective of the present study was to design a protocol combining the merits of an in vitro model, which are simple and reproducible, with aspects known to be relevant from in vivo studies. The principle is: an UV-transparent support to which the test product is applied, a (pre)irradiation and a transmission measurement. Transpore® tape (standard support for SPF determinations) was found to be incompatible with many preparations on prolonged contact times. Roughened quartz was adopted as a suitable alternative. Transmission measurements on this support are not reliable with a layer of 2 mg cm,2 (standard for SPF) due to detection limitations of spectrophotometers, hence a reduced layer of 0.75 mg cm,2 was adopted. Overall, it is very difficult to apply products in a reproducible thin layer on appropriate substrates. As a consequence, absolute parameters derived from the transmission profile show relatively large dispersion, whereas relative parameters, such as critical wavelength ,c[1] or UVA/UVB ratio are much less sensitive to unavoidable variations in layer thickness. An increase in deviations was observed when the samples were irradiated before measurement. It is crucial to control the output carefully (spectral distribution and even more importantly, irradiance and dose delivered) of the light source. By doing so and also taking into account the previous learning steps, a protocol was drafted and tested in a ringtest (four samples in six laboratories). The results are encouraging and show that if relative parameters (e.g. ,c, UVA/UVB ratio) are considered, the intra- as well as interlaboratory reproducibility is clearly better than can be obtained in vivo. In general, we describe a suitable method, which can be considered in any future official discussions about the methodology to determine UVA protection. Résumé La protection contre les UVA apportée par les écrans solaires est un sujet d'importance croissante en raison de la progression des connaissances concernant les dommages à la peau causés par les UVA. En Europe il n'existe pas de méthode disponible officiellement reconnue pour déterminer le degré de protection contre les UVA. Par conséquent, l'objectif de la présente étude est de concevoir un protocole associant les avantages d'un modèle in vitro, qui est simple et reproductible, avec des aspects connus comme appartenant aux études in vivo. Le principe est le suivant: un support transparent aux UV auquel le produit testé est appliqué, une (pré)irradiation et une mesure de transmission. Le ruban Transpore® (support standard pour la détermination des SPF) se révèle incompatible avec de nombreuses préparations lors de temps de contact prolongés. Le quartz rugueux est adopté comme alternative appropriée. Les mesures de transmission sur ce support ne sont pas fiables avec une couche de 2 mg/cm2 (norme pour les SPF) en raison des limites de détection des spectrophotomètres, et on adopte donc une couche réduite de 0,75 mg/cm2. Il est surtout très difficile d'appliquer des produits en une couche fine reproductible sur des substrats appropriés. En conséquence, les paramètres absolus tirés du profil de transmission montrent une assez grande dispersion, tandis que les paramètres relatifs, tels que la longueur d'onde critique ,c[l] ou le rapport UVA/UVB sont beaucoup moins sensibles aux variations inévitables de l'épaisseur de la couche. On observe une augmentation des écarts lorsque les échantillons sont irradiés avant la mesure. Il est crucial de contrôler soigneusement la sortie (distribution spectrale et encore plus important, irradiation et dose délivrée) de la source lumineuse. Dans ces conditions, et en tenant aussi compte des enseignements des étapes précédentes, un protocole a étéébauché et testé lors d'un essai tournant (quatre échantillons dans six laboratoires). Les résultats sont encourageants et montrent que si on considère les paramètres relatifs (par exemple ,c, rapport UVA/UVB), la reproductibilité intra et interlaboratoires est clairement meilleures que ce qu'on peut obtenir in vivo. D'une façon générale, nous décrivons une méthode appropriée, qui peut être considérée dans tout échange officiel futur concernant la méthodologie pour déterminer la protection contre les UVA. [source] Effect of herbal teas on hepatic drug metabolizing enzymes in ratsJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 10 2001Pius P. Maliakal We have investigated the effect of herbal teas (peppermint, chamomile and dandelion) on the activity of hepatic phase I and phase II metabolizing enzymes using rat liver microsomes. Female Wistar rats were divided into six groups (n = 5 each). Three groups had free access to a tea solution (2 %) while the control group had water. Two groups received either green tea extract (0.1 %) or aqueous caffeine solution (0.0625 %). After four weeks of pretreatment, different cytochrome P450 (CYP) isoforms and phase II enzyme activities were determined by incubation of liver microsomes or cytosol with appropriate substrates. Activity of CYP1A2 in the liver microsomes of rats receiving dandelion, peppermint or chamomile tea was significantly decreased (P < 0.05) to 15 %, 24 % and 39 % of the control value, respectively. CYP1A2 activity was significantly increased by pretreatment with caffeine solution. No alterations were observed in the activities of CYP2D and CYP3A in any group of the pretreated rats. Activity of CYP2E in rats receiving dandelion or peppermint tea was significantly lower than in the control group, 48 % and 60 % of the control, respectively. There was a dramatic increase (244 % of control) in the activity of phase II detoxifying enzyme UDP-glucuronosyl transferase in the dandelion tea-pretreated group. There was no change in the activity of glutathione-S-transferase. The results suggested that, like green and black teas, certain herbal teas can cause modulation of phase I and phase II drug metabolizing enzymes. [source] Half-metallic ferromagnetism in wurtzite SrCPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 1 2008Chang-wen Zhang Abstract The first-principles full potential linearized augmented plane-wave method within density-functional theory is used to investigate electronic structure and magnetism of wurtzite (WZ) crystal structure SrC. It is shown that the WZ SrC is a true half-metallic ferromagnet with a magnetic moment of 2,B per formula unit. The large HM gaps (0.72 eV) and robustness of half-metallicity with respect to the lattice change make it possible candidate grown epitaxially on appropriate substrates in the form of films thick enough, and therefore should be useful in spintronics and other related applications. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Remodeling of the SCF complex-mediated ubiquitination system by compositional alteration of incorporated F-box proteinsPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 1 2010Mitsunori Kato Abstract Ubiquitination regulates not only the stability but the localization and activity of substrate proteins involved in a plethora of cellular processes. The Skp1,Cullin,F-box protein (SCF) complexes constitute a major family of ubiquitin protein ligases, in each member of which an F-box protein serves as the variable component responsible for substrate recognition, thereby defining the function of each complex. Here we studied whether the composition of F-box proteins in the SCF complexes is remodeled under different conditions. We exploited stable isotope labeling and MS for relative quantification of F-box proteins in the SCF complexes affinity-purified en masse from budding yeast cells at log and post-diauxic phases, and revealed an increment of Saf1, an F-box protein involved in entry into quiescence, during the diauxic shift. Similarly, we found that Met4 overexpression induces a specific increment of Met30, the F-box protein responsible for ubiquitination of Met4. These results illustrate a cellular response to environmental and genetic perturbations through remodeling of the SCF complex-mediated ubiquitination system. Compositional alteration of incorporated F-box proteins may redirect the activity of this system toward appropriate substrates to be ubiquitinated under individual conditions for the maintenance of cellular homeostasis. [source] | |||||||||||||