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Engelbrekt C, Nazmutdinov RR, Zinkicheva TT, Glukhov DV, Yan J, Mao B, Ulstrup J, Zhang J. Chemistry of cysteine assembly on Au(100): electrochemistry, in situ STM and molecular modeling. NANOSCALE 2019; 11:17235-17251. [PMID: 31418761 DOI: 10.1039/c9nr02477h] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Cysteine (Cys) is an essential amino acid with a carboxylic acid, an amine and a thiol group. We have studied the surface structure and adsorption dynamics of l-cysteine adlayers on Au(100) from aqueous solution using electrochemistry, high-resolution electrochemical scanning tunnelling microscopy (in situ STM), and molecular modelling. Cys adsorption on this low-index Au-surface has been much less studied than Cys adsorption on Au(111)- and Au(110)-electrode surfaces. Chronopotentiometry was employed to monitor the adsorption dynamics at sub-second resolution and showed that adsorption is completed in 30 minutes at Cys concentrations above 100 μM. Two consecutive steps could be fitted to these data. Two separate reductive desorption peaks of Cys adlayers on Au(100) with a total coverage of 2.52 (±0.15) × 10-10 mol cm-2 were observed. In situ STM showed that the adsorbed Cys is organized in stripes with "fork-like" features which co-exist in (11 × 2)-2Cys and (7 × 2)-2Cys lattices, quite differently from Cys adsorption on Au(111)-electrode surfaces. Stripe structures with bright STM contrast in the center suggest that a second Cys adlayer on top of a first adlayer is formed, supporting the dual-peak reductive desorption of Cys adlayers. In addition, monolayers of both pure l-Cys and pure d-Cys and a 1 : 1 racemic mixture of l- and d-Cys on Au(100) were studied. Virtually identical macroscopic electrochemical features were found, but in situ STM discloses many more defects for the racemic mixture than for the pure enantiomers due to structural mismatch of l- and d-Cys. Density functional theory (DFT) calculations combined with a cluster model for the Au(100) surface were carried out to investigate the adsorption energy and geometry of the adsorbed monomer and dimer Cys species in different orientations, with detailed attention to the chirality effects. Optimized DFT geometries were used to construct model STM images, and kinetic Monte Carlo simulations undertaken to illuminate the growth of adsorbate rows and the mechanism of the adlayer formation as well as the Cys adsorption patterns specific to the Au(100)-electrode surface.
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Affiliation(s)
- Christian Engelbrekt
- Department of Chemistry, Building 207, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark.
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Long B, Tang L, Peng B, Zeng G, Zhou Y, Mo D, Fang S, Ouyang X, Yu J. Voltammetric Biosensor Based on Nitrogen-doped Ordered Mesoporous Carbon for Detection of Organophosphorus Pesticides in Vegetables. CURR ANAL CHEM 2018. [DOI: 10.2174/1573411014666180521090326] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Background:
Pesticides residues in agricultural products have posed a serious threat to food
safety and human health, so it is necessary to develop a rapid and accurate method to detect pesticide in
the environment. N-OMC with excellent electroconductivity, high biocompatibility and the functional
amino group that can be covalently attached to the enzyme can be applied to construct a sensitive and
stable acetylcholinesterase biosensor for rapid and accurate detection of organophosphorus pesticides
with the help of L-cysteine self-assembled monolayer and AuNPs.
Methods:
Transmission electron microscopy, scanning electron microscopy, Fourier transform infrared
spectroscopy and nitrogen adsorption measurements are used to characterize materials. Electrochemical
impedance spectroscopy and cyclic voltammetry are used to study the surface features of modified
electrodes. Differential pulse voltammetric is used to measure the peak current of modified electrodes.
GC-MS is applied to verify the reliability of the prepared biosensor for organophosphorus pesticides
detection.
Results:
N-OMC was synthesized and applied to constructed stable and sensitive acetylcholinesterase
biosensors. The combination of N-OMC, L-cysteine self-assembled monolayer and AuNPs to modify
the electrode surface has greatly improved the conductivity of biosensor and provided a stable platform
for acetylcholinesterase immobilization. The linear detection range of paraoxon was from 3 to 24 nM
with a lower detection limit of 0.02 nM.
Conclusion:
The biosensor exhibited satisfactory reproducibility, repeatability and stability, and was
successfully employed to determine the paraoxon in vegetables as well as tap water samples, providing
a promising tool for rapid and sensitive detection of organophosphorus pesticides in agricultural products.
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Affiliation(s)
- Beiqing Long
- College of Environmental Science and Engineering, Hunan University, Changsha, 410082, China
| | - Lin Tang
- College of Environmental Science and Engineering, Hunan University, Changsha, 410082, China
| | - Bo Peng
- College of Environmental Science and Engineering, Hunan University, Changsha, 410082, China
| | - Guangming Zeng
- College of Environmental Science and Engineering, Hunan University, Changsha, 410082, China
| | - Yaoyu Zhou
- College of Resources and Environment, Hunan Agricultural University, Changsha, 410128, China
| | - Dan Mo
- College of Environmental Science and Engineering, Hunan University, Changsha, 410082, China
| | - Siyuan Fang
- College of Environmental Science and Engineering, Hunan University, Changsha, 410082, China
| | - Xilian Ouyang
- College of Environmental Science and Engineering, Hunan University, Changsha, 410082, China
| | - Jiangfang Yu
- College of Environmental Science and Engineering, Hunan University, Changsha, 410082, China
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Boopathi S, Senthil Kumar S, Narasimha Phani KL. Generation of Active Sites on Gold Nanostructured Surface through Ultrasound-Assisted Direct Electrodeposition and Its Effect on Enzyme-less Glucose Electro-oxidation. ChemElectroChem 2014. [DOI: 10.1002/celc.201402021] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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