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Precursor Synthesis (precursor + synthesis)
Selected AbstractsPrecursor synthesis and radiolabelling of [11C]ADAM: a potential radioligand for the serotonin transporter exploration by PETJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 2 2001Johnny VERCOUILLIE Abstract The serotoninergic system is involved in a variety of neurological and psychiatric disorders. Exploration of the serotonin transporters (5-HTT) in living human brain by PET would be of great value for better understanding, diagnosis and therapeutic follow up of these diseases. In order to obtain a selective radioligand to explore the 5-HTT by PET we report the synthesis of [11C]N,N-dimethyl-2-(2-amino-4-iodophenylthio)-benzylamine ([11C]ADAM). The precursor for labelling N-demethyl ADAM, was obtained in five steps using 2,5-dibromonitrobenzene and 2-thio-N-methylbenzamide as starting material. [11C]ADAM was synthesised by N-alkylation of the precursor using [11C]methyl iodide in DMF. The incorporation yield of [11C]methyl iodide was in the range of 50 to 70%. Finally [11C]ADAM was obtained in 30 minutes synthesis time including HPLC and with a radiochemical purity better than 99%. Copyright © 2001 John Wiley & Sons, Ltd. [source] Heterologous expression and characterization of the exopolysaccharide from Streptococcus thermophilus Sfi39FEBS JOURNAL, Issue 19 2001Jacques-Edouard Germond The genes responsible for exopolysaccharide (EPS) synthesis in Streptococcus thermophilus Sfi39 were identified on a 20-kb genomic fragment. The two genes, epsE and epsG, were shown to be involved in EPS synthesis as their disruption lead to the loss of the ropy phenotype. Several naturally selected nonropy mutants were isolated, one acquired an insertion sequence (IS)-element (IS905) in the middle of the eps gene cluster. The eps gene cluster was cloned and transferred into a nonEPS-producing heterologous host, Lactococcus lactis MG1363. The EPS produced was shown by chemical analysis and NMR spectroscopy to be identical to the EPS produced by S. thermophilus Sfi39. This demonstrated first that all genes needed for EPS production and export were present in the S. thermophilus Sfi39 eps gene cluster, and second that the heterologous production of an EPS was possible by transfer of the complete eps gene cluster alone, provided that the heterologous host possessed all necessary genetic information for precursor synthesis. [source] 4-[18F]fluorophenyl ureas via carbamate-4-nitrophenyl esters and 4-[18F]fluoroaniline,JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 12 2006Sebastian Olma Abstract Four different no carrier added (n.c.a.) 4-[18F]fluorophenylurea derivatives are synthesized as model compounds via two alternative routes. In both cases carbamate-4-nitrophenylesters are used as intermediates. Either n.c.a. 4-[18F]fluoroaniline reacts with carbamates of several amines, or the carbamate of n.c.a. 4-[18F]fluoroaniline is formed at first and an amine is added subsequently to yield the urea derivative. The choice of the appropriate way of reaction depends on the possibilities of precursor synthesis. The radiochemical yields reach up to 80% after 50 min of synthesis time while no radiochemical by-products can be determined. These high yields were possible due to an optimized preparation of n.c.a. 4-[18F]fluoroaniline with a radiochemical yield of up to 90%. From the various ways of its radiosynthesis, the substitution with n.c.a. [18F]fluoride on dinitrobenzene is chosen, using phosphorous acid and palladium black for reduction of the second nitro group. Copyright © 2006 John Wiley & Sons, Ltd. [source] Spore cortex formation in Bacillus subtilis is regulated by accumulation of peptidoglycan precursors under the control of sigma KMOLECULAR MICROBIOLOGY, Issue 6 2007Pradeep Vasudevan Summary The bacterial endospore cortex peptidoglycan is synthesized between the double membranes of the developing forespore and is required for attainment of spore dehydration and dormancy. The Bacillus subtilis spoVB, spoVD and spoVE gene products are expressed in the mother cell compartment early during sporulation and play roles in cortex synthesis. Here we show that mutations in these genes block synthesis of cortex peptidoglycan and cause accumulation of peptidoglycan precursors, indicating a defect at the earliest steps of peptidoglycan polymerization. Loss of spoIV gene products involved in activation of later, ,K -dependent mother cell gene expression results in decreased synthesis of cortex peptidoglycan, even in the presence of the SpoV proteins that were synthesized earlier, apparently due to decreased precursor production. Data show that activation of ,K is required for increased synthesis of the soluble peptidoglycan precursors, and Western blot analyses show that increases in the precursor synthesis enzymes MurAA, MurB, MurC and MurF are dependent on ,K activation. Overall, our results indicate that a decrease in peptidoglycan precursor synthesis during early sporulation, followed by renewed precursor synthesis upon ,K activation, serves as a regulatory mechanism for the timing of spore cortex synthesis. [source] Cell wall growth during elongation and division: one ring to bind them?MOLECULAR MICROBIOLOGY, Issue 4 2007Dirk-Jan Scheffers Summary The role of the cell division protein FtsZ in bacterial cell wall (CW) synthesis is believed to be restricted to localizing proteins involved in the synthesis of the septal wall. In this issue of Molecular Microbiology, the groups of Christine Jacobs-Wagner and Waldemar Vollmer provide compelling evidence that in Caulobacter crescentus, FtsZ plays an additional role in CW synthesis in non-dividing cells. During elongation (cell growth) FtsZ is responsible for the incorporation of CW material in a zone at the midcell by recruiting MurG, a protein involved in peptidoglycan (PG) precursor synthesis. This resembles earlier findings of FtsZ mediated PG synthesis activity in Escherichia coli. A role of FtsZ in PG synthesis during elongation forces a rethink of the current model of CW synthesis in rod-shaped bacteria. [source] | ||||||||||