Xanthine is a purine base and intermediate in the biosynthesis of uric acid (Item No. 16219).{59425,59426} It is formed during mammalian purine catabolism in the liver via oxidation of hypoxanthine (Item No. 22254) by xanthine oxidase (XO), which also oxidizes xanthine to produce uric acid.{59425,59427} Xanthine is also formed from guanine, xanthosine, or hypoxanthine during purine catabolism in plants.{59428} It has been found in a variety of commercial foodstuffs, including beer yeast, mushrooms, vegetables, fish, and beef.{59429} Urinary xanthine levels are decreased in patients with primary gout.{59430} Xanthine has also been used in the synthesis of xanthine derivatives that have anticancer or anti-inflammatory activities in vitro.{59431}
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A purine base and intermediate in uric acid biosynthesis; been found in a variety of commercial foodstuffs; urinary levels are decreased in patients with primary gout; has been used in the synthesis of xanthine derivatives that have anticancer or anti-inflammatory activities in vitro
Formal name: 3,9-dihydro-1H-purine-2,6-dione
Synonyms: 2,6-Dihydroxypurine|NSC 14664
Molecular weight: 152.1
CAS: 69-89-6
Purity: ≥98%
Formulation: A crystalline solid
The tetracycline repressor (TetR) is a transcriptional regulator which normally binds tightly to its palindromic tetO operator DNA, blocking gene expression.{17508} Tet causes the repressor to dissociate from the DNA, allowing transcription to occur. A novel reverse TetR (revTetR) requires tetracycline as a co-repressor to bind tetO and block transcription.{17509,17510} Anhydrotetracycline (hydrochloride) is a powerful effector in both the tetracycline repressor (TetR) and reverse TetR (revTetR) systems, binding the Tet repressor 35-fold more strongly than Tet.{17508,17511} Moreover, anhydrotetracycline poorly binds the 30S ribosomal subunit, compared to Tet,{17512} so it does not act as a general inhibitor of translation and is a poor antibiotic. Perhaps related to this, the concentration of anhydrotetracycline that inhibits eukaryotic cell growth is more than a 1,000-fold above the dose that alters transcription through TetR.{17508}
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The PtdIn phosphates play an important role in the generation and transduction of intracellular signals.{8344,4096,14518} PtdIns-(3,4,5)-P3-biotin is an affinity probe which allows the PIP3 to be detected through an interaction with the biotin ligand. This design allows PtdIns-(3,4,5)-P3-biotin to serve as a general probe for any protein with a high affinity binding interaction with inositol-(3,4,5)-triphosphate phospholipids, such as phosphatidylinositol 3-kinase, PTEN, or PH-domain-containing proteins.
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The maintenance of embryonic stem cells in culture typically requires feeder cells and various exogenous factors found in serum. Murine embryonic stem (mES) cells can be maintained in the absence of feeder cells and serum but require the leukemia inhibitor factor (LIF) and bone morphogenic protein (BMP) to prevent differentiation and promote self-renewal. SC-1 is a small molecule activator of stem cell renewal that allows the propagation of OG2 mES cells for at least 10 passages in an undifferentiated state.{14533} The activity of SC-1 is mediated by the combined inhibition of RasGAP and ERK1 with Kd values of 98 and 212 nM, respectively.{14533} Inhibition of RasGAP increases Ras signaling via the PI3-kinase pathway which promotes self-renewal, whereas inhibition of ERK blocks differentiation.
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Cyclin-dependent kinases (CDKs) are key regulators of cell cycle progression and are therefore promising targets for cancer therapy. (R)-Roscovitine is a potent inhibitor of Cdk2/cyclin E with an IC50 value of 0.1 µM.{14988} It also inhibits Cdk7/cyclin H, Cdk5/p35, and cell division cycle (cdc)/cyclin B with IC50 values of 0.49, 0.16, and 0.65 µM, respectively.{14987,14988,14991} (R)-Roscovitine inhibits the growth of rapidly proliferating cells with an average IC50 value of 15.2 µM against a panel of 19 human tumor cell lines.{14988} In murine models of polycystic kidney disease, (R)-roscovitine effectively inhibited disease progression at doses of 50-100 mg/kg.{14564}
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