Antitumor activity of some new 1,3,8-trisubstituted purine-2,6-diones and 1,3,6-trisubstitutedthiazolo[2,3-f] purine-2,4-diones

New l,3,8-trisubsttiuted purine-2,6-diones and 1,3,6-trisubstituted thiazolo[2,3-f] purine-2,4-diones were designed and synthesized as potential antitumor agents. The cytotoxic effects of the tested compounds were assessed against two human malignant-cell lines: T-cell leukemia derived SKW-3 and breast cancer -derived MDA-MB-231 using the methyl thiazolyl tetrazolium [MTT-dye] reduction assay, after 72 h exposure. The data -were fitted to sigmoidal concentration response curves and the corresponding 1C 50 values were calculated using commercially available software [GraphPad Prizm]. Compound AH-206 was the most potent cytotoxic agent among the newly synthesized compounds, with 1C 50 value of 17.3 micro M. Prominent activity was also encountered with compounds AH-201, AH-205, AH-208, AH-214 and AH-217, all having 1C[50] values below 100 micro M

In vitro selection of specific aptamers against microcystin-LR / 中华预防医学杂志

<p><b>OBJECTIVE</b>In vitro selection of specific RNA aptamers against microcystin-LR from a random RNA pool.</p><p><b>METHODS</b>A RNA library with 40 randomized nucleotide positions was applied to select for specific aptamers to microcystin-LR covalently linked to Sepharose by using a standard in vitro selection protocol.</p><p><b>RESULTS</b>The specific enriched RNA aptamer for microcystin-LR increased step by step from initial round to 11th round after which a plateau of the aptamer quantity was observed between 11th and 13th round. The enriched RNAs from last round were reverse transcribed, PCR amplified and cloned into E. coli DH10 b competent cells. Sixty colonies were sequenced from which 38 sequences were aligned and classified into 3 families and 5 duplicates and no conserved sequences were found among them. Eight representative clones from the groups were selected for further binding experiments comparing with original pool RNA. Four clone RNAs were identified with relatively high affinity to microcystin-LR, of which MC25 clone RNA could combine with microcystin-LR as lower as 0.5 micromol/L.</p><p><b>CONCLUSION</b>Subpopulations of RNA molecules that bind specifically to microcystin-LR have been isolated from a population of random sequence RNA molecules, which might provide a new way for future application in environmental monitoring of microcystin.</p>