Studies of Surface Coverage and Orientation of DNA Molecules Immobilized onto Preformed Alkanethiol Self-Assembled Monolayers

Abstract

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)-3ethylcarbodiimide 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.

Electrochemiluminescent hybridization chip with electric field aided mismatch discrimination

“…It can be noticed that the reduction peak is considerably more pronounced compared to the oxidation peak. Previously, RuHex voltammograms have been shown on similarly prepared surface, where the reduction peak of RuHex decreased upon DNA immobilization (Huang et al, 2000). A probable explanation for this difference in our results is that we immobilized DNA strands with their 5 -end, and thus expect them to be in an upright position, whereas in the other case amino groups present in a DNA strand were used to achieve immobilization, resulting in a longitudinal positioning of DNA with respect to the surface.…”

“…However, this process is very tedious because the procedure for the modification of DNA is complicated, and the yield of synthesis of mercaptocontaining DNA is quite low (Ge et al, 2003;Huang et al, 2000). Another common way to immobilize biomolecules on gold is via mercapto-carboxylic acids, which in the presence of carbodiimides can form amide bond with an amino group present in a biomolecule.…”

A Self‐assembly Route for Double Bilayer Lipid Membrane Formation

“…Here we describe a new method to form double bilayer lipid membranes (dBLMs) on solid supports using NHS/EDC [17] chemistry [hydroxy-2,5-dioxopyrrolidine-3-sulfonicacid sodium salt (NHS) and N-Ethyl-N'-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) Figure 1]. In this approach, two biomembranes, one of which contains the amine-functionalised cholesterol derivative 1 and the other which contains the CO 2 H-funtionalised cholesterol derivative 2 are covalently joined together by an NHS/EDC mediated reaction [18,19] as shown schematically in Figure 1. Details of the synthesis and characterization of the cholesterol derivatives 1 and 2 are given in the Supporting Information.…”

4‐Aminothiophenol Self‐Assembled Monolayer for the Development of a DNA Biosensor Aiming the Detection of Cylindrospermopsin Producing Cyanobacteria

“…20 nm), pointing out to the bending of the probe. As it has been reported for proteins [49 -51], or nucleic acids [52,53] the shape of adsorbed biomolecules is strongly affected by the underlying surface properties. In this case, AFM imaging reveals that adsorbed ss-DNA apparently displays a globular shape, as a result of its covalent adsorption onto the 4-ATP SAM, that can be in part influenced by the tip shape [52].…”