In an article published in the journal Analytical Chemistry, researchers utilize carbon nanopipettes to elucidate the electrocatalytic activities of a single redox enzyme. The influence of the carbon nanopipette on the enzyme's activities was also reported.
Study: Nanoconfined Electrochemical Collision and Catalysis of Single Enzyme inside Carbon Nanopipettes. Image Credit: luchschenF/Shutterstock.com
Redox Enzymes and Their Uses
Redox enzymes, which have active sites for catalyzing specific redox reactions, have prominent responsibilities in enzyme kinetics and metabolic functions, as well as in catalytic, energy, and biomedical applications sectors.
Redox enzymes are often fixed at the working electrode to expedite charge transport activities and make desirable current signals. Extra mediating compounds are also utilized to link the hidden active surface area within the enzyme structure.
As a result, the sizes, geometries, and activation centers of redox enzymes must be determined to obtain the basic knowledge of charge transport routes. This helps to enable efficient catalytic and sensor applications based on such activities.
Standard morphological assessment approaches only give aggregated physiochemical properties from enzyme assemblages without obtaining data on individual enzymes.
Methods to Study Redox Enzymes
In this scenario, much effort has been spent in studying redox enzymes at the singular entity stage. In addition to visual approaches, solitary redox potential has been identified as a simple but effective tool for characterizing a wide range of micro-entities.
As specific particles settle on a surface of the electrode, they may block redox mediating flows, catalyze particular redox reactions, and experience inductive charging/discharging or electrolytic activities, revealing physical and chemical data on personal substances from present transient conditions.
Even though a technique for revealing a particular enzyme has been established, accurately detecting the catalytic flow from a particular enzyme remains difficult. A redox enzyme, unlike catalytic nanoparticles, has extremely restricted activity areas and must fall on an electrode with the appropriate alignment to properly catalyze a given process.
To create one pA in 1 ms, for instance, the turnover rate of a single enzyme must be more than 106 s-1, which is substantially greater than the average frequency of most organic enzymes. As a result, a specific amplifying technique must be devised to precisely monitor the catalytic properties of a single enzyme.
Conductive Nanopipette and its Advantages
A conducting nanopipette may be an effective opportunity for revealing the electrocatalytic properties of a particular enzyme. Aside from capturing a few or a limited number of enzymes in a limited container, nanoscale confinement may open up new avenues for electrochemical research.
The nanoconfinement phenomenon is believed to enhance the catalytic activity of enzymes in restricted areas, and a 100-fold boost in catalytic properties has been documented.
Conductive nanopipettes would improve the enzymatic activity and create observable current signals in this situation. However, since conducting nanopipettes feature both pipet shapes and electroactive surfaces, resistant pulsing and electrochemical colliding studies may be readily performed as a single body. Furthermore, their modest dimensions would permit reduced background currents and new uses for in vivo evaluation within individual living cells.
In this study, carbon nanopipettes (CNPs) were employed to investigate the electrocatalytic properties of a single enzyme molecule using both surface blocking and electrocatalytic enhancement methodologies. Using the horseradish peroxidase (HRP) enzymes as an example diminishing current signals were exhibited when a solitary HRP lands on the surface of the catalyst and blocks the oxidative degradation of Fe (CN)6
Highlights of the Study
In this study, by using the nanoscale containment within carbon nanopipettes, the researchers were finally able to effectively unveil the electrochemical catalytic characteristics of a single horseradish peroxidase enzyme through both oxidation/reduction techniques.
Electrochemical oxidation pulses appeared at very small horseradish peroxidase levels, leading to the formation of oxygen, whereas electrocatalytic peaks appeared at sufficiently high levels.
The transition frequency of the particular enzyme was then calculated using the ensuing surges, yielding a 10-100-fold boost in enzymatic activity. It is expected that using carbon nanopipettes will aid in discovering electrocatalytic currents from a wide range of enzymes, particularly those with a low output.
Other enzymes' early collision tests were also attempted, and the distinct peaks provided aid in elucidating the essential enzymatic and catalytic properties of the specific enzymes. Furthermore, the carbon nanopipettes' tiny size and electroactive surfaces made them ideal for in vivo electrochemical sensing and monitoring assessments in single cells.
Reference
Shen, X., Liu, R., & Wang, D. (2022). Nanoconfined Electrochemical Collision and Catalysis of Single Enzyme inside Carbon Nanopipettes. Analytical Chemistry. Available at: https://doi.org/10.1021/acs.analchem.2c01554
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