Ostblom Mattias, Liedberg Bo, Demers Linette M, Mirkin Chad A
Division of Molecular Physics, Department of Physics, Chemistry and Biology, Linköping University, S-581 83 Linköping, Sweden.
J Phys Chem B. 2005 Aug 11;109(31):15150-60. doi: 10.1021/jp051617b.
The structure and desorption dynamics of mono- and multilayer samples of adenine, cytosine, guanine, and thymine on polycrystalline gold thin films are studied using temperature-programmed desorption-infrared reflection absorption spectroscopy (TPD-IRAS) and temperature-programmed desorption-mass spectroscopy (TPD-MS). It is shown that the pyrimidines, adenine and guanine, adsorb to gold in a complex manner and that both adhesive (adenine) and cohesive (guanine) interactions contribute the apparent binding energies to the substrate surface. Adenine displays at least two adsorption sites, including a high-energy site (210 degrees C, approximately 136 kJ/mol), wherein the molecule coordinates to the gold substrate via the NH2 group in an sp3-like, strongly perturbed, nonplanar configuration. The purines, cytosine and thymine, display a less complicated adsorption/desorption behavior. The desorption energy for cytosine (160 degrees C, approximately 122 kJ/mol) is similar to those obtained for adenine and guanine, but desorption occurs from a single site of dispersed, nonaggregated cytosine. Thymine desorbs also from a single site but at a significantly lower energy (100 degrees C, approximately 104 kJ/mol). Infrared data reveal that the monolayer architectures discussed herein are structurally very different from those observed for the bases in the bulk crystalline state. It is also evident that both pyrimidines and purines adsorb on gold with the plane of the molecule in a nonparallel orientation with respect to the substrate surface. The results of this work are discussed in the context of improving the understanding of the design of capturing oligonucleotides or DNA strands for bioanalytical applications, in particular, for gold nanoparticle-based assays.
利用程序升温脱附-红外反射吸收光谱法（TPD-IRAS）和程序升温脱附-质谱法（TPD-MS）研究了腺嘌呤、胞嘧啶、鸟嘌呤和胸腺嘧啶在多晶金薄膜上的单层和多层样品的结构及脱附动力学。结果表明，嘧啶、腺嘌呤和鸟嘌呤以复杂的方式吸附于金表面，且粘附（腺嘌呤）和内聚（鸟嘌呤）相互作用均对底物表面的表观结合能有贡献。腺嘌呤显示出至少两个吸附位点，包括一个高能位点（210℃，约136kJ/mol），在此位点分子通过NH2基团以类似sp3的、强烈扰动的非平面构型与金底物配位。嘌呤、胞嘧啶和胸腺嘧啶表现出较简单的吸附/脱附行为。胞嘧啶的脱附能（160℃，约122kJ/mol）与腺嘌呤和鸟嘌呤的脱附能相似，但脱附发生在分散的、非聚集的胞嘧啶的单个位点。胸腺嘧啶也从单个位点脱附，但能量显著较低（100℃，约104kJ/mol）。红外数据表明，本文讨论的单层结构在结构上与在块状晶体状态下观察到的碱基结构有很大不同。同样明显的是，嘧啶和嘌呤均以分子平面相对于底物表面非平行的取向吸附在金上。本文工作的结果是在增进对用于生物分析应用（特别是基于金纳米颗粒的分析）的捕获寡核苷酸或DNA链设计的理解的背景下进行讨论的。
