Studies of surface coverage and orientation of DNA molecules immobilized onto preformed alkanethiol self-assembled monolayers
Studies of surface coverage and orientation of DNA molecules immobilized onto preformed alkanethiol self-assembled monolayers
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DOI：
10.1021/la9910834
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发表时间：
2000-04-04
期刊：
影响因子：
3.9
通讯作者：
Deng, L
中科院分区：
文献类型：
--
作者：
Huang, E;Zhou, FM;Deng, L
DNA 分子通过 N-羟基磺基琥珀酰亚胺 (NHS)/1-(3-(二甲基氨基)丙基)-3-乙基碳二亚胺盐酸盐 (EDC) 交联反应附着在金表面预先形成的羧酸盐封端的烷硫醇自组装单层 (SAM) 上。使用循环伏安法、石英晶体微天平 (QCM) 和原子力显微镜 (AFM) 来探测固定 DNA 分子的表面覆盖度和分子取向。 DNA 附着归因于 DNA 碱基上的羧酸基团和氨基之间形成酰胺键，因为研究并排除了 DNA 非特异性吸附到预先形成的 SAM 或 NHS 酯单层上的可能性。我们的伏安结果表明，烷硫醇 SAM 中最初可用于通过附着的 DNA 分子进行异质电子转移的位点被显着堵塞。 QCM 提供了固定 DNA 量的半定量测量。 AFM 图像首次揭示了相对有序的 DNA 薄膜可以在与由 SAM 的底层末端羧酸基团拉伸的 DNA 分子共价连接时形成。然而，固定时似乎发生了某些碎片。断裂可能是由于DNA分子和羧酸盐基团之间的强烈相互作用，其空间分布与DNA双螺旋内碱基上氨基的分离和分布并不完全吻合。
DNA molecules are attached onto carboxylate-terminated alkanethiol self-assembled monolayers (SAMs) preformed at gold surfaces via the N-hydroxysulfosuccinimide (NHS)/1-(3-(dimethylamino)propyl)-3-ethylcarbodiimide hydrochloride (EDC) cross-linking reaction. Cyclic voltammetry, quartz crystal microbalance (QCM), and atomic force microscopy (AFM) were used to probe the surface coverage and molecular orientation of the immobilized DNA molecules. The DNA attachment is attributed to the formation of amide bond between the carboxylate groups and the amino groups on the DNA bases since the possibility of nonspecific adsorption of DNA onto preformed SAMs or NHS ester monolayers was studied and excluded. Our voltammetric results indicate a significant blockage of the sites originally available in the alkanethiol SAMs for facile heterogeneous electron transfer by the attached DNA molecules. QCM provided a semiquantitative measurement of the amount of immobilized DNA. The AFM images, for the first time, revealed that relatively ordered DNA films can be formed in the covalent attachment with DNA molecules stretched by the underlying terminal carboxylate groups of the SAMs. However, certain fragmentation appears to have occurred upon immobilization. The fragmentation is probably due to the strong interaction between the DNA molecules and the carboxylate groups whose spatial distribution does not fit perfectly well with the separation and distribution of the amino groups on the bases within the DNA double helix.