Paraxanthine-d6 is intended for use as an internal standard for the quantification of paraxanthine (Item No. 21068) by GC- or LC-MS. Paraxanthine is an active metabolite of caffeine (Item No. 14118).{58128} It is formed via N3-demethylation of caffeine by the cytochrome P450 (CYP) isoform CYP1A2. Paraxanthine is an adenosine A1 and A2 receptor antagonist (Kis = 35 and 22 µM, respectively).{38151} In vivo, paraxanthine (30 mg/kg) increases striatal cGMP and extracellular striatal dopamine levels and locomotor activity, as well as inhibits motor depression induced by the adenosine A1 agonist CPA (N6-cyclopentyladenosine; Item No. 21448) or the adenosine A2 receptor agonist CGS 21680 (Item No. 17126) in rats not habituated to caffeine.{38150} It also promotes wakefulness and increases locomotor activity and core temperature in narcoleptic transgenic mice without increasing behavioral anxiety.{38152}
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An internal standard for the quantification of paraxanthine by GC- or LC-MS
Formal name: 3,7-dihydro-1,7-di(methyl-d3)-1H-purine-2,6-dione
Synonyms: 1,7-Dimethylxanthine-d6
Molecular weight: 186.2
CAS: 117490-41-2
Purity: ≥99% deuterated forms (d1-d6); ≤1% d0
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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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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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 nuclear factor-κB (NF-κB) regulates the expression of numerous genes involved in immunity and inflammation, cellular stress responses, growth, and apoptosis. Resveratrol, a polyphenolic trans-stilbene, is a known inhibitor of the activation of NF-κB and exhibits activity against a wide variety of cancer cells. CAY10512 is a substituted trans-stilbene analog of resveratrol that is 100-fold more potent as measured by antioxidant activity. The IC50 value for inhibition of TNFα-induced activation of NF-κB by CAY10512 is 0.15 µM compared to 20 µM by resveratrol.{14545}
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