title: Single-molecule optical-trapping measurements with DNA anchored to an array of gold nanoposts.
abstract: Gold-thiol chemistry is one of the most successful chemistries for conjugating biomolecules to surfaces, but such chemistry has not been exploited in optical-trapping experiments because of laser-induced ablation of gold. In this work, we describe a method to combine these two separate technologies without undue heating using DNA anchored to gold nanostructures (r = 50-250 nm; h ≈ 20 nm). Moreover, we demonstrate a quantitative and mechanically robust (>100 pN) optical-trapping assay. By using three dithiol phosphoramidites (DTPAs) incorporated into a polymerase chain reaction (PCR) primer, the gold-DNA bond remained stable 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 (mPEG-SH). Overall, this surface conjugation of biomolecules onto an ordered array of gold nanostructures by chemically and mechanically robust bonds provides a unique way to carry out spatially controlled, repeatable measurements of single molecules.
authors.affiliation: JILA, National Institute of Standards and Technology and University of Colorado, Boulder, CO, USA.
authors.forename: D Hern
authors.initials: DH
authors.lastname: Paik
authors.forename: Thomas T
authors.initials: TT
authors.lastname: Perkins
mesh_terms: D004247:DNA / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D049329:Nanostructures / Q000737:chemistry*; D036103:Nanotechnology / Q000379:methods*; D052898:Optical Tweezers; D017655:Silicon Compounds / Q000737:chemistry; D013499:Surface Properties
chemical_list: D017655:Silicon Compounds; D006046:Gold; D004247:DNA; C032734:silicon nitride