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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Studies of the Base-Dependent Binding of Cu(T4) to DNA Hairpins (H_2T)4 = meso-Tetrakis(4-(N-methylpyridiumyl))porphyrin)
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Studies of the Base-Dependent Binding of Cu(T4) to DNA Hairpins (H_2T)4 = meso-Tetrakis(4-(N-methylpyridiumyl))porphyrin)

机译：Cu（T4）与DNA发夹（H_2T）4 =内消旋四（4（N-甲基吡啶基）卟啉）的碱基依赖性结合研究

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Water-soluble, cationic metalloporphyrins that bind to DNA show promise as artificial nucleases and as sensitizers for photodynamic therapy, but fundamental questions remain about the binding motifs and sequence specificities. To address these issues, we have studied the interactions of Cu(T) with a series of oligonucleotides that form hairpin structures (H_2T4 = meso-tetrakis(4-(N-methylpyridiniumyl))porphyrin). Each oligonucleotide is a 6-mer with a central run of four thymine (T) bases and complementary ends that can combine to form a specific sequence of six adenine-thymine (A = T) and guanine-cytosine (G≡C) base pairs. The techniques employed include thermal melting as well as circular dichroism (CD), absorbance, and emission spectroscopies. The number of G≡C base pairs in the stem is the most important factor that determines the melting temperature of the hairpin, and in every case investigated, the uptake of Cu(T4) stabilizes the hairpin. Depending on the nature of the adduct that forms, △ε varies from -22 to + 17 M~(-1) cm~(-1) in the Soret region of the CD spectrum, and the emission intensity from Cu(T4) changes by an order of magnitude. The results yield several useful insights regarding the binding interactions. One is that robust hydrogen bonding within a B-form duplex promotes intercalative binding of Cu(T4). Thus, if the composition is at least 50% G≡C base pairs, intercalation will occur even in the absense of a G≡C step. On the other hand, a run of four A = T base pairs defines a groove-binding site with an affinity comparable to that for intercalation at a G≡C. Step. Finally, at least in solutions containing excess oligonucleotide, there is no sign that either loop binding or hemiintercalation is a prevalent mode of interaction between Cu(T4) and hairpin hosts.
机译：与DNA结合的水溶性阳离子金属卟啉有望作为人造核酸酶和光动力疗法的敏化剂使用，但有关结合基序和序列特异性的基本问题仍然存在。为了解决这些问题，我们研究了Cu（T）与一系列形成发夹结构的寡核苷酸（H_2T4 =中四（4-（N-甲基吡啶基））卟啉的相互作用。每个寡核苷酸均为6聚体，中心有四个胸腺嘧啶（T）碱基和互补末端，可以结合形成六个腺嘌呤-胸腺嘧啶（A = T）和鸟嘌呤-胞嘧啶（G≡C）碱基对的特定序列。所采用的技术包括热熔以及圆二色性（CD），吸收率和发射光谱。茎中G≡C碱基对的数量是决定发夹融化温度的最重要因素，在每种情况下，对Cu（T4）的吸收都能稳定发夹。根据形成的加合物的性质，在CD光谱的Soret区，△ε在-22至+ 17 M〜（-1）cm〜（-1）之间变化，Cu（T4）的发射强度发生变化一个数量级。结果产生了一些有关结合相互作用的有用见解。一个是在B型双链体中牢固的氢键促进了Cu（T4）的嵌入键。因此，如果组成为至少50％的G≡C碱基对，则即使在没有G≡C步骤的情况下也会发生插入。另一方面，四个A ＝ T碱基对的行程定义了一个凹槽结合位点，其亲和力可与在G≡C处插入的亲和力相当。步。最后，至少在含有过量寡核苷酸的溶液中，没有迹象表明环结合或半嵌入是Cu（T4）与发夹宿主之间相互作用的普遍模式。

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