Limits...
Tunnelling readout of hydrogen-bonding-based recognition.

Chang S, He J, Kibel A, Lee M, Sankey O, Zhang P, Lindsay S - Nat Nanotechnol (2009)

Bottom Line: Junctions that are held together by three hydrogen bonds per base pair (for example, guanine-cytosine interactions) are stiffer than junctions held together by two hydrogen bonds per base pair (for example, adenine-thymine interactions).Similar, but less pronounced effects are observed on the approach of the tunnelling probe, implying that attractive forces that depend on hydrogen bonds also have a role in determining the rise of current.These effects provide new mechanisms for making sensors that transduce a molecular recognition event into an electronic signal.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Arizona State University, Tempe, Arizona 85287, USA.

ABSTRACT
Hydrogen bonding has a ubiquitous role in electron transport and in molecular recognition, with DNA base pairing being the best-known example. Scanning tunnelling microscope images and measurements of the decay of tunnel current as a molecular junction is pulled apart by the scanning tunnelling microscope tip are sensitive to hydrogen-bonded interactions. Here, we show that these tunnel-decay signals can be used to measure the strength of hydrogen bonding in DNA base pairs. Junctions that are held together by three hydrogen bonds per base pair (for example, guanine-cytosine interactions) are stiffer than junctions held together by two hydrogen bonds per base pair (for example, adenine-thymine interactions). Similar, but less pronounced effects are observed on the approach of the tunnelling probe, implying that attractive forces that depend on hydrogen bonds also have a role in determining the rise of current. These effects provide new mechanisms for making sensors that transduce a molecular recognition event into an electronic signal.

Show MeSH

Related in: MedlinePlus

Tunnel-current decay curves. The decay curves were obtained at a bias (V in Fig. 1) of 0.4V as the probe was retracted from a monolayer of nucleosides at a rate of 100 nm/s. a, an 8-mercaptoguanine probe interacting with a deoxycytidine monolayer (G-C); b, 2-amino-8-mercaptoadenine functionalized probe interacting with a thymidine monolayer (2AA-T); c, an 8-mercaptoadenine probe interacting with a thymidine monolayer (A-T); d, a 2-amino-8-mercaptoadenine functionalized probe interacting with a deoxycytidine monolayer (2AA-C). All nucleosides were 5'-thiolated. The initial setpoint currents were 3 nA (green), 2.4 nA (brown), 1.2 nA (purple), 0.8 nA (blue), 0.4 nA (khaki) and 0.1 nA (black). The curves are a combination of repeated measurements on the same point and measurements made at different points on the substrate. The signals from non-hydrogen-bonded controls decay much more rapidly (supporting information). Logarithmic plots are available in the supporting information.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2698135&req=5

Figure 2: Tunnel-current decay curves. The decay curves were obtained at a bias (V in Fig. 1) of 0.4V as the probe was retracted from a monolayer of nucleosides at a rate of 100 nm/s. a, an 8-mercaptoguanine probe interacting with a deoxycytidine monolayer (G-C); b, 2-amino-8-mercaptoadenine functionalized probe interacting with a thymidine monolayer (2AA-T); c, an 8-mercaptoadenine probe interacting with a thymidine monolayer (A-T); d, a 2-amino-8-mercaptoadenine functionalized probe interacting with a deoxycytidine monolayer (2AA-C). All nucleosides were 5'-thiolated. The initial setpoint currents were 3 nA (green), 2.4 nA (brown), 1.2 nA (purple), 0.8 nA (blue), 0.4 nA (khaki) and 0.1 nA (black). The curves are a combination of repeated measurements on the same point and measurements made at different points on the substrate. The signals from non-hydrogen-bonded controls decay much more rapidly (supporting information). Logarithmic plots are available in the supporting information.

Mentions: Electron tunneling through an analyte molecule can yield chemical information.6,7,8 Given that hydrogen bonds enhance electron tunneling rates over vacuum tunneling,9 we have proposed a new approach using self-assembled, hydrogen bonded tunnel junctions to give good contacts10 and chemical selectivity simultaneously.5,11 To demonstrate the feasibility of this approach, we functionalized a gold STM probe with a DNA base that was brought into contact with a monolayer of nucleosides on a gold surface under 1,2,4-trichlorobenzene (Figure 1 and see Methods). A steady tunnel current set-point (ISP ) was established under servo-control, the servo broken, and the current recorded as the probe was pulled away from the surface. Current-decay curves for a number of hydrogen-bond molecular junctions are shown in Figure 2. Clearly, the junctions held together by three hydrogen bonds (gunanine-deoxycytidine, G-C and 2-aminoadenine-thymidine, 2AA-T) give signals that extend farther than those held together by two (adenine-thymidine, A-T and 2 aminoadenine-deoxycytidine, 2AA-C). Curves for other base-pair combinations are given in the supporting information. Current decays even more rapidly in solvent alone or with a non-hydrogen-bonding molecule (thiophenol) attached to the probe (supporting information). The curves shown in Figure 2 are raw, unselected data taken from several regions of the substrate. Remarkably, the identity of the hydrogen-bonded molecules can often be determined from a single curve.


Tunnelling readout of hydrogen-bonding-based recognition.

Chang S, He J, Kibel A, Lee M, Sankey O, Zhang P, Lindsay S - Nat Nanotechnol (2009)

Tunnel-current decay curves. The decay curves were obtained at a bias (V in Fig. 1) of 0.4V as the probe was retracted from a monolayer of nucleosides at a rate of 100 nm/s. a, an 8-mercaptoguanine probe interacting with a deoxycytidine monolayer (G-C); b, 2-amino-8-mercaptoadenine functionalized probe interacting with a thymidine monolayer (2AA-T); c, an 8-mercaptoadenine probe interacting with a thymidine monolayer (A-T); d, a 2-amino-8-mercaptoadenine functionalized probe interacting with a deoxycytidine monolayer (2AA-C). All nucleosides were 5'-thiolated. The initial setpoint currents were 3 nA (green), 2.4 nA (brown), 1.2 nA (purple), 0.8 nA (blue), 0.4 nA (khaki) and 0.1 nA (black). The curves are a combination of repeated measurements on the same point and measurements made at different points on the substrate. The signals from non-hydrogen-bonded controls decay much more rapidly (supporting information). Logarithmic plots are available in the supporting information.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2698135&req=5

Figure 2: Tunnel-current decay curves. The decay curves were obtained at a bias (V in Fig. 1) of 0.4V as the probe was retracted from a monolayer of nucleosides at a rate of 100 nm/s. a, an 8-mercaptoguanine probe interacting with a deoxycytidine monolayer (G-C); b, 2-amino-8-mercaptoadenine functionalized probe interacting with a thymidine monolayer (2AA-T); c, an 8-mercaptoadenine probe interacting with a thymidine monolayer (A-T); d, a 2-amino-8-mercaptoadenine functionalized probe interacting with a deoxycytidine monolayer (2AA-C). All nucleosides were 5'-thiolated. The initial setpoint currents were 3 nA (green), 2.4 nA (brown), 1.2 nA (purple), 0.8 nA (blue), 0.4 nA (khaki) and 0.1 nA (black). The curves are a combination of repeated measurements on the same point and measurements made at different points on the substrate. The signals from non-hydrogen-bonded controls decay much more rapidly (supporting information). Logarithmic plots are available in the supporting information.
Mentions: Electron tunneling through an analyte molecule can yield chemical information.6,7,8 Given that hydrogen bonds enhance electron tunneling rates over vacuum tunneling,9 we have proposed a new approach using self-assembled, hydrogen bonded tunnel junctions to give good contacts10 and chemical selectivity simultaneously.5,11 To demonstrate the feasibility of this approach, we functionalized a gold STM probe with a DNA base that was brought into contact with a monolayer of nucleosides on a gold surface under 1,2,4-trichlorobenzene (Figure 1 and see Methods). A steady tunnel current set-point (ISP ) was established under servo-control, the servo broken, and the current recorded as the probe was pulled away from the surface. Current-decay curves for a number of hydrogen-bond molecular junctions are shown in Figure 2. Clearly, the junctions held together by three hydrogen bonds (gunanine-deoxycytidine, G-C and 2-aminoadenine-thymidine, 2AA-T) give signals that extend farther than those held together by two (adenine-thymidine, A-T and 2 aminoadenine-deoxycytidine, 2AA-C). Curves for other base-pair combinations are given in the supporting information. Current decays even more rapidly in solvent alone or with a non-hydrogen-bonding molecule (thiophenol) attached to the probe (supporting information). The curves shown in Figure 2 are raw, unselected data taken from several regions of the substrate. Remarkably, the identity of the hydrogen-bonded molecules can often be determined from a single curve.

Bottom Line: Junctions that are held together by three hydrogen bonds per base pair (for example, guanine-cytosine interactions) are stiffer than junctions held together by two hydrogen bonds per base pair (for example, adenine-thymine interactions).Similar, but less pronounced effects are observed on the approach of the tunnelling probe, implying that attractive forces that depend on hydrogen bonds also have a role in determining the rise of current.These effects provide new mechanisms for making sensors that transduce a molecular recognition event into an electronic signal.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Arizona State University, Tempe, Arizona 85287, USA.

ABSTRACT
Hydrogen bonding has a ubiquitous role in electron transport and in molecular recognition, with DNA base pairing being the best-known example. Scanning tunnelling microscope images and measurements of the decay of tunnel current as a molecular junction is pulled apart by the scanning tunnelling microscope tip are sensitive to hydrogen-bonded interactions. Here, we show that these tunnel-decay signals can be used to measure the strength of hydrogen bonding in DNA base pairs. Junctions that are held together by three hydrogen bonds per base pair (for example, guanine-cytosine interactions) are stiffer than junctions held together by two hydrogen bonds per base pair (for example, adenine-thymine interactions). Similar, but less pronounced effects are observed on the approach of the tunnelling probe, implying that attractive forces that depend on hydrogen bonds also have a role in determining the rise of current. These effects provide new mechanisms for making sensors that transduce a molecular recognition event into an electronic signal.

Show MeSH
Related in: MedlinePlus