1 3
or structural variations of the proteins might be promoting direct electron transfer
(DET) between the electrode and the T1 redox centers of the enzymes, and, therefore, the electroreduction of molecular oxygen to water.
Despite the aforementioned breakthrough, there is a lack of knowledge of the
structural and conformational properties of enzymes at each catalytic step. Therefore, the chemical and structural factors that enable electrochemical activity, as well
as a deep understanding of the electron transfer processes associated with the catalytic reaction, has yet to be completely unraveled experimentally. In this direction,
amplifying the low electrocatalytic signal of enzyme-electrode signals using lowdimensional materials to improve the electronic communication of proteins with
the surface electrodes and, in turn, facilitate the electrochemical investigation of the
catalytic role of enzymes, represents a suitable alternative. Also, a large number of
advanced electrochemical techniques, quartz-crystal microbalance measurements,
and spectroscopic techniques such as resonance Raman and infrared spectroscopy
should be coupled in situ to the resulting nanocomposites to gain insightful advances
in the mechanistic understanding of enzyme-based electrocatalysts [2].
As a first approach, Rafael Luque and coworkers have reported that the partially
unfolded states of laccase molecules mechanochemically immobilized on magnetic
nanoparticles give rise to very low onset potential and outstanding currents towards
the direct bioelectrocatalytic reduction of molecular oxygen [50]. The low content
of α-helix, together with the increase in the number of low-frequency β-sheets, was
associated directly with improved electrocatalytic activity (Fig. 2). This pioneering work sheds light on the nature of the nanometric interaction between proteins
and low-dimensional materials and the impact on their bioelectrocatalytic function.
However, the detailed mechanism of how conformational variations of proteins can
lead to improvements in electrocatalytic activity is still unclear.
Therefore, investigation of the underlying chemistry of protein-based nanocatalysts in the electrocatalytic process is still in its infancy. A lot of research should
be carried out to disentangle the structural variations that proteins attached to lowdimensional materials undergo under electrocatalytic conditions. Molecular dynamics studies of the movement of these proteins during bioelectrocatalysis can be
applied successfully to unravel their dynamic catalytic performances at the molecular scale. Additionally, control of the structure–function properties of nanobiocatalyts using molecular biology approaches such as the replacement of specific amino
acids to greatly improve their electrocatalytic yields constitutes a promising strategy.
Briefly, we envision that this knowledge will open the door towards the development
of a new generation of biomaterials with unbeatable electrocatalytic properties.
4 Protein Based‑Materials as High‑performance Water‑Splitting
Electrocatalysts
Proteins have ultimately inspired the design of powerful nanomaterials towards the
electrochemical reduction of O 2 . Two approaches have delivered impressive outcomes: (1) N-based nanocomposites fabricated using N-containing proteins and (2)
the incorporation of redox-active sites into the nanohybrid structures.
242
Reprinted from the journal
Topics in Current Chemistry (2020) 378:43
or structural variations of the proteins might be promoting direct electron transfer
(DET) between the electrode and the T1 redox centers of the enzymes, and, therefore, the electroreduction of molecular oxygen to water.
Despite the aforementioned breakthrough, there is a lack of knowledge of the
structural and conformational properties of enzymes at each catalytic step. Therefore, the chemical and structural factors that enable electrochemical activity, as well
as a deep understanding of the electron transfer processes associated with the catalytic reaction, has yet to be completely unraveled experimentally. In this direction,
amplifying the low electrocatalytic signal of enzyme-electrode signals using lowdimensional materials to improve the electronic communication of proteins with
the surface electrodes and, in turn, facilitate the electrochemical investigation of the
catalytic role of enzymes, represents a suitable alternative. Also, a large number of
advanced electrochemical techniques, quartz-crystal microbalance measurements,
and spectroscopic techniques such as resonance Raman and infrared spectroscopy
should be coupled in situ to the resulting nanocomposites to gain insightful advances
in the mechanistic understanding of enzyme-based electrocatalysts [2].
As a first approach, Rafael Luque and coworkers have reported that the partially
unfolded states of laccase molecules mechanochemically immobilized on magnetic
nanoparticles give rise to very low onset potential and outstanding currents towards
the direct bioelectrocatalytic reduction of molecular oxygen [50]. The low content
of α-helix, together with the increase in the number of low-frequency β-sheets, was
associated directly with improved electrocatalytic activity (Fig. 2). This pioneering work sheds light on the nature of the nanometric interaction between proteins
and low-dimensional materials and the impact on their bioelectrocatalytic function.
However, the detailed mechanism of how conformational variations of proteins can
lead to improvements in electrocatalytic activity is still unclear.
Therefore, investigation of the underlying chemistry of protein-based nanocatalysts in the electrocatalytic process is still in its infancy. A lot of research should
be carried out to disentangle the structural variations that proteins attached to lowdimensional materials undergo under electrocatalytic conditions. Molecular dynamics studies of the movement of these proteins during bioelectrocatalysis can be
applied successfully to unravel their dynamic catalytic performances at the molecular scale. Additionally, control of the structure–function properties of nanobiocatalyts using molecular biology approaches such as the replacement of specific amino
acids to greatly improve their electrocatalytic yields constitutes a promising strategy.
Briefly, we envision that this knowledge will open the door towards the development
of a new generation of biomaterials with unbeatable electrocatalytic properties.
4 Protein Based‑Materials as High‑performance Water‑Splitting
Electrocatalysts
Proteins have ultimately inspired the design of powerful nanomaterials towards the
electrochemical reduction of O 2 . Two approaches have delivered impressive outcomes: (1) N-based nanocomposites fabricated using N-containing proteins and (2)
the incorporation of redox-active sites into the nanohybrid structures.
242
Reprinted from the journal
Topics in Current Chemistry (2020) 378:43