Wolf Lauren K, Gao Yang, Georgiadis Rosina M
Department of Chemistry, Boston University, Boston, Massachusetts 02215, USA.
Langmuir. 2004 Apr 13;20(8):3357-61. doi: 10.1021/la036125+.
We present results of the first systematic study on in situ sequence-dependent kinetics for short single-strand oligonucleotide surface immobilization. By measuring film coverage for both thiolated and nonthiolated homo-oligomers as a function of adsorption time, we determine the relative contribution of specific thiol-surface and nonspecific DNA-surface interactions to the overall mechanism of DNA-thiol attachment to gold. We find that sequence-dependent nonspecific surface interactions play a significant role in DNA-thiol immobilization, influencing not only the kinetics but also the extent of oligomer adsorption. For example, sequences that initially form strong, rapid nonspecific contacts with the surface hinder long-time thiol adsorption (i.e., poly(dA)-thiol). In contrast, sequences with nucleotides that initially bind slowly and weakly to the surface (i.e., poly(dT)-thiol) do not obstruct further thiol adsorption, resulting in higher film coverage and Langmuir immobilization kinetics. This view of the DNA-thiol immobilization mechanism is further supported by sequence-dependent rinsing losses observed for thiolated DNA strands but not for analogous nonthiolated strands. Nonthiolated strands contact the surface strongly in a more horizontal orientation, whereas thiolated strands attain a more upright orientation that allows vertical DNA-DNA base-stacking. The results clearly illustrate the importance and interplay of competitive specific and nonspecific forces in forming DNA-thiol films. The specific coverage attained and the time dependence of the adsorption process depend on the prevailing sequence composition.
我们展示了关于短单链寡核苷酸表面固定原位序列依赖性动力学的首次系统研究结果。通过测量硫醇化和非硫醇化同聚物的膜覆盖率作为吸附时间的函数，我们确定了特定硫醇 - 表面和非特异性DNA - 表面相互作用对DNA - 硫醇附着到金的整体机制的相对贡献。我们发现序列依赖性非特异性表面相互作用在DNA - 硫醇固定中起重要作用，不仅影响动力学，还影响寡聚物吸附的程度。例如，最初与表面形成强而快速的非特异性接触的序列会阻碍长时间的硫醇吸附（即聚（dA） - 硫醇）。相反，其核苷酸最初与表面缓慢且弱结合的序列（即聚（dT） - 硫醇）不会阻碍进一步的硫醇吸附，从而导致更高的膜覆盖率和朗缪尔固定动力学。硫醇化DNA链观察到的序列依赖性冲洗损失进一步支持了这种DNA - 硫醇固定机制的观点，而类似的非硫醇化链则没有这种情况。非硫醇化链以更水平的方向与表面强烈接触，而硫醇化链则达到更直立的方向，允许垂直的DNA - DNA碱基堆积。结果清楚地说明了在形成DNA - 硫醇膜中竞争性特异性和非特异性力的重要性和相互作用。达到的特定覆盖率和吸附过程的时间依赖性取决于主要的序列组成。
