本研究係針對 cis-Pt(NH3)2Cl2 (cisplatin) 的衍生物, Pt(1R, 2R-dach)22+ (dach:diaminocyclohexane) ,探討其與cisplatin 反應途徑之異同,與反應條件及序列之偏好。 經由與cisplatin相同條件實驗結果,顯示 Pt(1R, 2R-dach)22+ 不會如 cisplatin 之反應途徑,與 DNA 產生 cis-GG 的交聯鍵結反應。 根據 UV 及 CD 升溫圖譜研究顯示 Pt(1R, 2R-dach)22+ 可與 AT-rich 之 DNA 序列產生溝槽結合反應。反應條件溫度需 40℃ , Pt(1R, 2R-dach)22+:DNA則需在 30:1 以上,為本實驗可產生反應之必要條件。 由本實驗 10 條 DNA 序列之 UV 及 CD 升溫圖譜分析,Pt(1R, 2R-dach)22+ 對含單結合位置的 DNA 序列,其結合強度皆不強,而對含雙結合位置的 DNA 序列則都近乎完全反應,推測d(CXXCGXXG)2 及d(CXXCCGGXXG)2 (X=A或T) 為 Pt(1R, 2R-dach)22+ 偏好之 DNA 序列特徵,為至少 2 組連續 A 或 T 的鹼基對,此協同性結合(cooperative binding) 為正協同作用 (positive cooperativity)。
This investigation was carried out via a cis-Pt(NH3)2Cl2 (cisplatin) derivative, Pt(1R, 2R-dach)22+ (dach:diaminocyclohexane), and focused on the different reaction pathways, reaction conditions and sequence preferences between cisplatin and Pt(1R, 2R-dach)22+. Under the same experiment conditions as cisplatin, the results suggested Pt(1R, 2R-dach)22+ do not follow the same mechanism as cisplatin, in forming cis-GG crosslink with DNA. Based on variable temperature UV and CD denaturation analysis, Pt(1R, 2R-dach)22+ can react with AT-rich DNA sequences through groove binding. Based on experiments carried out under various conditions, suggested that reaction temperature about 40℃ and Pt(1R, 2R-dach)22+:DNA over 30:1 were required to promote the reaction. Refer to UV and CD denaturation experiment of ten DNA samples of variable sequences in this work, Pt(1R, 2R-dach)22+ has only weak binding affinity to single binding site sequences, whereas double binding site sequences react almost completely with Pt(1R, 2R-dach)22+. The variable sequence studies suggested that the consensus sequences of Pt(1R, 2R-dach)22+-DNA sites are d(CXXCGXXG)2 and d(CXXCCGGXXG)2 (X=A or T) with at least 2 base pairs of A or T.
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