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Integrating a High-Force Optical Trap with Gold Nanoposts and a Robust Gold-DNA Bond

机译：将高强制性光学陷阱与金纳米柱和牢固的金DNA结合。

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Gold-thiol chemistry is widely used in nanotechnology but has not been exploited in optical-trapping experiments due to laser-induced ablation of gold. We circumvented this problem by using an array of gold nanoposts (r = 50-250 nm, h approximate to 20 nm) that allowed for quantitative optical-trapping assays without direct irradiation of the gold. DNA was covalently attached to the gold via dithiol phosphoramidite (DTPA). By using three DTPAs, the gold-DNA bond was not cleaved in the presence of excess thiolated compounds. This chemical robustness allowed us to reduce nonspecific sticking by passivating the unreacted gold with methoxy-(polyethylene glycol)-thiol. We routinely achieved single beads anchored to the nanoposts by single DNA molecules. We measured DNA's elasticity and its overstretching transition, demonstrating moderate- and high-force optical-trapping assays using gold-thiol chemistry. Force spectroscopy measurements were consistent with the rupture of the strepavidin-biotin bond between the bead and the DNA. This implied that the DNA remained anchored to the surface due to the strong gold-thiol bond. Consistent with this conclusion, we repeatedly reattached the trapped bead to the same individual DNA molecule. Thus, surface conjugation of biomolecules onto an array of gold nanostructures by chemically and mechanically robust bonds provides a unique way to carry out spatially controlled, repeatable measurements of single molecules.
机译：金硫醇化学已广泛用于纳米技术中，但由于激光诱导的金烧蚀，尚未在光阱实验中得到利用。我们通过使用金纳米柱阵列（r = 50-250 nm，h大约为20 nm）规避了这个问题，该阵列可以进行定量光阱测定而无需直接照射金。 DNA通过二硫醇亚磷酰胺（DTPA）共价附于金。通过使用三个DTPA，在过量的硫醇化化合物存在下，金-DNA键不会断裂。这种化学稳定性使我们可以通过用甲氧基-（聚乙二醇）-硫醇钝化未反应的金来减少非特异性粘附。我们通常通过单个DNA分子获得固定在纳米柱上的单个珠子。我们测量了DNA的弹性及其过度伸展的转变，证明了使用金硫醇化学方法进行的中，高强度光学诱捕测定。力谱测量与珠子和DNA之间的链霉亲和素-生物素键的断裂一致。这暗示由于强的金-硫醇键，DNA保持锚定在表面上。与这个结论一致，我们反复将捕获的珠子重新附着到同一单个DNA分子上。因此，通过化学和机械稳健键将生物分子表面缀合到金纳米结构阵列上，提供了一种进行空间控制，可重复的单分子测量的独特方法。

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