scholarly journals Voltammetry and molecular assembly of G-quadruplex DNAzyme on single-crystal Au(111)-electrode surfaces – hemin as an electrochemical intercalator

2016 ◽  
Vol 193 ◽  
pp. 99-112 ◽  
Author(s):  
Ling Zhang ◽  
Jens Ulstrup ◽  
Jingdong Zhang
Keyword(s):  
Single Crystal ◽  
Single Molecule ◽  
Electrode Surface ◽  
Molecular Assembly ◽  
Electrode Surfaces ◽  
Potential Control ◽  
G Quadruplex ◽  
Tunnelling Microscopy ◽  
Dna Quadruplexes

DNA quadruplexes (qs) are a class of “non-canonical” oligonucleotides (OGNs) composed of stacked guanine (G) quartets stabilized by specific cations. Metal porphyrins selectively bind to G-qs complexes to form what is known as DNAzyme, which can exhibit peroxidase and other catalytic activity similar to heme group metalloenzymes. In the present study we investigate the electrochemical properties and the structure of DNAzyme monolayers on single-crystal Au(111)-electrode surfaces using cyclic voltammetry and scanning tunnelling microscopy under electrochemical potential control (in situ STM). The target DNAzyme is formed from a single-strand OGN with 12 guanines and iron(iii) porphyrin IX (hemin), and assembles on Au(111) through a mercapto alkyl linker. The DNAzyme monolayers exhibit a strong pair of redox peaks at 0.0 V (NHE) at pH 7 in acetate buffer, shifted positively by about 50 mV compared to free hemin weakly physisorbed on the Au(111)-electrode surface. The voltammetric hemin signal of DNAzyme is enhanced 15 times compared with that of hemin adsorbed directly on the Au(111)-electrode surface. This is indicative of both the formation of a close to dense DNAzyme monolayer and that hemin is strongly bound to the immobilized 12G-qs in well-defined orientation favorable for interfacial ET with a rate constant of 6.0 ± 0.4 s−1. This is supported by in situ STM which discloses single-molecule G-quartet structures with a size of 1.6 ± 0.2 nm.

scholarly journals Tuning Single-Molecule Conductance by Controlled Electric Field-Induced trans-to-cis Isomerisation

2021 ◽  
Vol 11 (8) ◽  
pp. 3317
Author(s):  
C.S. Quintans ◽  
Denis Andrienko ◽  
Katrin F. Domke ◽  
Daniel Aravena ◽  
Sangho Koo ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Single Molecule ◽  
Quantum Interference ◽  
Single Molecule Level ◽  
Wet Chemical Synthesis ◽  
Single Molecule Junctions ◽  
Tunnelling Microscopy ◽  
The Difference

External electric fields (EEFs) have proven to be very efficient in catalysing chemical reactions, even those inaccessible via wet-chemical synthesis. At the single-molecule level, oriented EEFs have been successfully used to promote in situ single-molecule reactions in the absence of chemical catalysts. Here, we elucidate the effect of an EEFs on the structure and conductance of a molecular junction. Employing scanning tunnelling microscopy break junction (STM-BJ) experiments, we form and electrically characterize single-molecule junctions of two tetramethyl carotene isomers. Two discrete conductance signatures show up more prominently at low and high applied voltages which are univocally ascribed to the trans and cis isomers of the carotenoid, respectively. The difference in conductance between both cis-/trans- isomers is in concordance with previous predictions considering π-quantum interference due to the presence of a single gauche defect in the trans isomer. Electronic structure calculations suggest that the electric field polarizes the molecule and mixes the excited states. The mixed states have a (spectroscopically) allowed transition and, therefore, can both promote the cis-isomerization of the molecule and participate in electron transport. Our work opens new routes for the in situ control of isomerisation reactions in single-molecule contacts.

Single-molecule transistor fabrication by self-aligned lithography and in situ molecular assembly

2006 ◽  
Vol 83 (4-9) ◽  
pp. 1706-1709 ◽  
Author(s):  
J. Tang ◽  
E.P. De Poortere ◽  
J.E. Klare ◽  
C. Nuckolls ◽  
S.J. Wind
Keyword(s):  
Single Molecule ◽  
Molecular Assembly ◽  
Transistor Fabrication ◽  
Single Molecule Transistor

Developments in Using Scanning Probe Microscopy To Study Molecules on Surfaces — From Thin Films and Single-Molecule Conductivity to Drug–Living Cell Interactions

2006 ◽  
Vol 59 (6) ◽  
pp. 359 ◽  
Author(s):  
Pall Thordarson ◽  
Rob Atkin ◽  
Wouter H. J. Kalle ◽  
Gregory G. Warr ◽  
Filip Braet
Keyword(s):  
Single Molecule ◽  
Scanning Probe Microscopy ◽  
Cell Interactions ◽  
Scanning Probe ◽  
Probe Microscopy ◽  
Force Microscopy ◽  
Atomic Force ◽  
Tunnelling Microscopy ◽  
Molecule Surface

Scanning probe microscopy (SPM) techniques, including atomic force microscopy (AFM) and scanning tunnelling microscopy (STM), have revolutionized our understanding of molecule–surface interactions. The high resolution and versatility of SPM techniques have helped elucidate the morphology of adsorbed surfactant layers, facilitated the study of electronically conductive single molecules and biomolecules connected to metal substrates, and allowed direct observation of real-time processes such as in situ DNA hybridization and drug–cell interactions. These examples illustrate the power that SPM possesses to study (bio)molecules on surfaces and will be discussed in depth in this review.

Voltammetry and in situ scanning tunnelling microscopy of de novo designed heme protein monolayers on Au(111)-electrode surfaces

2006 ◽  
Vol 69 (2) ◽  
pp. 193-200 ◽  
Author(s):  
Tim Albrecht ◽  
Wen-Wu Li ◽  
Wolfgang Haehnel ◽  
Peter Hildebrandt ◽  
Jens Ulstrup
Keyword(s):  
De Novo ◽  
Heme Protein ◽  
Scanning Tunnelling Microscopy ◽  
Electrode Surfaces ◽  
Scanning Tunnelling ◽  
Protein Monolayers ◽  
Tunnelling Microscopy

In situ restoration of atomically well-ordered copper single-crystal electrode surfaces

1989 ◽  
Vol 111 (16) ◽  
pp. 6473-6474 ◽  
Author(s):  
John L. Stickney ◽  
Ignacio Villegas ◽  
Charles B. Ehlers
Keyword(s):  
Single Crystal ◽  
Copper Single Crystal ◽  
Electrode Surfaces ◽  
Single Crystal Electrode

scholarly journals Voltammetry and Single‐Molecule In Situ Scanning Tunnelling Microscopy of the Redox Metalloenzyme Human Sulfite Oxidase

2021 ◽  
Vol 8 (1) ◽  
pp. 164-171 ◽  
Author(s):  
Jiawei Yan ◽  
Emil Egede Frøkjær ◽  
Christian Engelbrekt ◽  
Silke Leimkühler ◽  
Jens Ulstrup ◽  
...  
Keyword(s):  
Single Molecule ◽  
Sulfite Oxidase ◽  
Scanning Tunnelling Microscopy ◽  
Scanning Tunnelling ◽  
Tunnelling Microscopy ◽  
Human Sulfite Oxidase
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