Screening steroid

Through fractionating WWTW effluents and screening those fractions with cell-based bioassays responsive to estrogens, the natural steroidal estrogens Ej and... 

A combinatorial approach for biocatalytic production of polyesters was demonstrated. A library of polyesters were synthesized in 96 deep-well plates from a combination of divinyl esters and glycols with lipases of different origin. In this screening, lipase CA was confirmed to be the most active biocatalyst for the polyester production. As acyl acceptor, 2,2,2-trifluoroethyl esters and vinyl esters were examined and the former produced the polymer of higher molecular weight. Various monomers such as carbohydrates, nucleic acids, and a natural steroid diol were used as acyl acceptor. 

We saw in Chapter 3 that bisubstrate reactions can conform to a number of different reaction mechanisms. We saw further that the apparent value of a substrate Km (KT) can vary with the degree of saturation of the other substrate of the reaction, in different ways depending on the mechanistic details. Hence the determination of balanced conditions for screening of an enzyme that catalyzes a bisubstrate reaction will require a prior knowledge of reaction mechanism. This places a necessary, but often overlooked, burden on the scientist to determine the reaction mechanism of the enzyme before finalizing assay conditions for HTS purposes. The importance of this mechanistic information cannot be overstated. We have already seen, in the examples of methotrexate inhibition of dihydrofolate, mycophenolic acid inhibiton of IMP dehydrogenase, and epristeride inhibition of steroid 5a-reductase (Chapter 3), how the [5]/A p ratio can influence one s ability to identify uncompetitive inhibitors of bisubstrate reactions. We have also seen that our ability to discover uncompetitive inhibitors of such reactions must be balanced with our ability to discover competitive inhibitors as well. 

Microbial transformations of four heteroyohimbine stereoisomers [ajmalicine (81a) tetrahydroalstonine (81b), isoajmalicine (81c), and akumigine (81d)] yielded mixtures of 10- and 11-hydroxylation products (786) (Scheme 21). Microorganisms known for their abilities to metabolize indole alkaloids, steroids, and antibiotics were intitially screened, and seven cultures were further used for preparative-scale incubations with alkaloid substrate. The microorganisms used and yields (by HPLC) of metabolites obtained from 81a-81d are shown in Table HI. 

Fig. 16. Screening of a steroid library using (top) MIP prepared against 11-a-hydroxyproges-terone (1), gradient elution using (bottom) non-imprinted control polymer, isocratic elution. Reprinted with permission from Ramstrom O, Ye L, Krook M, Mosbach K (1998) Anal Com-mun 35 9. Copyright 1998 The Royal Society of Chemistry...

Non steroidal antiinflammatory drugs were among the first classes of chiral compounds investigated in the early stages of the application of macrocyclic antibiotics as chiral selectors therefore, they were screened on vancomycin [7], teicoplanin [30], ristocetin A [33] CSPs under RPmode systems, and on avoparcin CSP under NP mode systems [37]. The enantioresolution of a variety of pro fens was later reported on commercially available vancomycin CSPs [128, 168], and recently on a ME-TAG CSP [58]. Ibuprofen enantiomers were also separated on a CDP-1-containing CSP [55]. Glycopeptide A-40,926 CSP was successfully employed in the analytical and semipreparative separation of 2-arylpropionic acids [63]. 

Kuronen P, Volin P, Laitalainen T. 1998. Reversed-phase high-performance liquid chromatographic screening method for serum steroids using retention index and diode-array detection. J Chromatogr B 718(2) 211-224. 

Dickey et al. (403) reported a list of tau-reducing compounds identified from an initial in-cell Western screening assay. Drugs resulting in more than 25% reductions in tan levels with less than 10% reductions in GAPDH include aggregation inhibitors (diazaquone, methylene blue) antibiotics (alexidine HCl) antiproliferatives (colchicine, albendazole, chelidonine, rotenone) and steroids (norethindrone) (403). 

A screening of about 40 strains currently used for steroid hydroxylation was undertaken, using reverse-phase HPLC and UV absorption to detect and quantitate metabolite formation. Most of the strains tested were able to metabolize extensively this substrate within a 1- to 5-day period, producing in the incubation medium variable amounts of at least eight hydroxylated metabolites (80-87), essentially depending on the strain used [189]. 

Lin BQ, Ji H, Li P, Fang W, Jiang Y, Inhibitors of acetylcholine esterase in vitro screening of steroidal alkaloids from Fritillaria species, Planta Afc 72 814—818,... 

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