Search results for "Urine"
showing 10 items of 924 documents
Synthesis of 2-amino-6-(2-[18F]fluoro-pyridine-4-ylmethoxy)-9-(octyl-β-d-glucosyl)-purine: a novel radioligand for positron emission tomography studi…
2002
Abstract The synthesis of the novel glucose conjugated O6-methylguanine-DNA methyltransferase (MGMT) inhibitor 2-amino-6-(2-[18F]fluoro-pyridine-4-ylmethoxy)-9-(octyl-α- d -glucosyl)-purine is reported. This compound might serve as a radiotracer for the determination of the MGMT status of tumour tissue.
Dimethylpyridin-4-ylamine-Catalysed Alcoholysis of 2-Amino-N,N,N-Trimethyl-9H-purine-6-ylammonium Chloride: An Effective Route to O6-Substituted Guan…
2002
Dimethylpyridin-4-ylamine (DMAP)-catalysed reactions of 2-amino-N,N,N-trimethyl-9H-purine-6-ylammonium chloride with fluoropyridine methoxides and various other alkoxides in DMSO at 60 °C gave the corresponding coupling products in moderate to good yields between 20-87%. Under these reaction conditions, fluorinated O 6 -substituted Guanine derivatives have been synthesized which could not be obtained via known analogous literature procedures. The respective yields of known O 6 -substituted guanine derivatives could be significantly improved by using this method. The efficient use of DMAP as an excellent nucleophilic catalyst in the syntheses of O 6 -substituted Guanine derivatives has thus …
Substituent effects on the stability of the four most stable tautomers of adenine and purine
2019
Substituent effects at the C2-, C8- and N-positions of adenine and purine in their four the most stable tautomers are studied by means of B97D3/aug-cc-pvdz computation applying substituents of varying electronic properties: NO2, CN, CHO, Cl, F, H, Me, OMe, OH and NH2. The substituent effect is characterized by the substituent effect stabilization energy (SESE) and substituent Hammett constant σ. For adenine, SESE is obtained with purine as the reference system. Additionally, for both adenine and purine, SESE characteristics are estimated with benzene, imidazole and amino-pyrimidine as reference systems, when possible, taking into account substitution in topologically equivalent positions. T…
Nucleoside uptake in male germ cells of the polychaeteNereis virens
1997
Summary Uptake of inosine and guanosine was measured in male germ ceils of the polychaete Nereis virens at different stages of development. In spermatogonia I (spg I) and spermatid stages, total inosine uptake at 12°C and ambient concentrations of 100 μmol/1 was relatively low (10–50 nmol·ml of packed cell volume pcv−l·h−1). A rapid increase (150–300 nmol·ml of pcv-1·h−1) was found during transition from spg I to spg II with a subsequent decline to low values (10–30 nmol·ml of pcv−1·h−1) in spermatocyte and spermatid stages. This transient increase may be related to the proliferative activity of spg I stages leading to spg II stages, which increases the demand of purine precursors for nucle…
Nucleotide pool changes in coelomic cells (eleocytes) of the polychaete Nereis virens during sexual maturation
1998
Eleocytes (a type of coelomic cell) of the polychaete Nereis virens can store large amounts of adenine nucleotides at certain times. Since eleocytes have specific functions related to gametogenesis, we tested whether the presence of these large nucleotide stores in eleocytes is specific to gender or related to specific events during gametogenesis. Nucleotide pools in eleocytes isolated at different stages of sexual maturation from N. virens were analysed using high-performance liquid chromatography. Eleocytes from immature and male animals had extremely high concentrations of both AMP and ADP (each > 10 µmol/ml of packed cell volume). In eleocytes from male animals, the high nucleotide stor…
Metabolite supply in oocytes of Nereis virens: role of nucleosides
1999
Gamete development in Nereis virens and other nereidid polychaetes is organized in a simple way. Follicular tissues are absent and the germ cells develop floating freely in the coelomic fluid, which thus serves as the vehicle for the supply of substances required for oocyte growth. This overview focusses on the role of exogenous purine nucleosides for the growing oocytes. Eleocytes, a coelomic cell type which is proliferated in large amounts at the beginning of sexual maturation, supply purine nucleosides to support nucleic acid synthesis in the oocytes. Eleocytes can store large amounts of purine nucleotides (up to 50 µ mol ml−1 cell vol.) in the form of AMP and ADP. During oogenesis, thes…
Uptake and Metabolism of Purine Nucleosides and Purine Nucleoside Analogues by Cells
1979
Since the discovery of purine nucleotides and purine nucleosides, 1847 by Liebig (1) (inosinic acid) and 1885 by Schulze et al. (2) (guanosine),it was only relatively recently that purine- and purine-nucleoside analogues have been considered to be effective antitumor or antiviral agents. It is due to Prusoff, Schabel and S.S. Cohen that on the other hand pyrimidine nucleoside analogues have already been used clinically as drugs for a number of years.
Impact of the Substituents on the Electronic Structure of the Four Most Stable Tautomers of Purine and Their Adenine Analogues
2020
Substituent effects at the C2-, C8-, and N-positions of adenine and purine on the structural and π-electronic changes in their four tautomers were studied using the B97D3/aug-cc-pvdz computational level. The effect of various substituents (NO2, CN, CHO, Cl, F, H, Me, OMe, OH, and NH2) was characterized by the charge of the substituent active region (cSAR) approach and Hammett substituent constants σ. It has been found that for both adenine and purine derivatives, substituents from the C8–X position have a stronger influence on their electronic structure than from the C2–X and N–X positions. The presence of the amino group in adenine enhances the substituent effect compared to that which occ…
Global effects of ade8 deletion on budding yeast metabolism
2021
AbstractPurine auxotrophy is a typical marker for many laboratory yeast strains. Supplementation of additional purine source (like adenine) is necessary to cultivate these strains. If not supplied in adequate amounts, purine starvation sets in. We tested purine starvation effects in budding yeast Saccharomyces cerevisiae ade8 knockout. We explored effects brought by purine starvation in cellular, central carbon metabolism and in the global transcriptome level.We observed that cells cultivated in purine depleted media became significantly more tolerant to severe thermal, oxidative and desiccation stresses when compared to the cells cultivated in media with all necessary supplements. When sta…
NMR Quantification of Tautomeric Populations in Biogenic Purine Bases
2009
Purine bases such as purine, adenine, hypoxanthine, and mercaptopurine are known to exist in several tautomeric forms. Characterization of their tautomeric equilibria is important not only for predicting the regioselectivity of their N-alkylation reactions but also for gaining knowledge of the patterns with which these compounds of significant biological activity form hydrogen bonds with their biological targets. Low-temperature 1H- and 13C-NMR spectroscopy were used to investigate the tautomeric equilibria for purine and some purine derivatives in methanol and N,N-dimethylformamide solutions. The N(7)H and N(9)H tautomeric forms were quantified by integrating the individual 1H NMR signals …