Tracking light-induced electron transfer toward O2 in a hybrid photoredox-laccase system

Abstract

Summary Photobiocatalysis uses light to perform specific chemical transformations in a selective and efficient way. The intention is to couple a photoredox cycle with an enzyme performing multielectronic catalytic activities. Laccase, a robust multicopper oxidase, can be envisioned to use dioxygen as a clean electron sink when coupled to an oxidation photocatalyst. Here, we provide a detailed study of the coupling of a [Ru(bpy) 3 ] 2+ photosensitizer to laccase. We demonstrate that efficient laccase reduction requires an electron relay like methyl viologen. In the presence of dioxygen, electrons transiently stored in superoxide ions are scavenged by laccase to form water instead of H 2 O 2 . The net result is the photo accumulation of highly oxidizing [Ru(bpy) 3 ] 3+ . This study provides ground for the use of laccase in tandem with a light-driven oxidative process and O 2 as one-electron transfer relay and as four-electron substrate to be a sustainable final electron acceptor in a photocatalytic process.

Photocatalytic generation of a non-heme Fe(iii)-hydroperoxo species with O2 in water for the oxygen atom transfer reaction

“…The formation of superoxide radicals via MV˙ + in aqueous solution has been described in a recent study under similar conditions. 61 It should be noted that the fast quenching of the [Ru II (bpy) 3 ] 2+ * excited triplet state by MV 2+ (present at a concentration nearly two orders of magnitude higher than the concentration of O 2 ) minimizes the formation of singlet oxygen via triplet–triplet energy transfer from [Ru II (bpy) 3 ] 2+ * to 3 O 2 . Back electron transfer from O 2 ˙ − to [Ru III (bpy) 3 ] 3+ ( eqn (4) ) occurs with similar kinetics to those between MV˙ + and [Ru III (bpy) 3 ] 3+ in the absence of O 2 (Fig.…”

“…The formation of superoxide radicals via MVc + in aqueous solution has been described in a recent study under similar conditions. 61 It should be noted that the fast quenching of the [Ru II (bpy [Ru III (bpy…”

Controlled Immobilization of a Palladium Complex/Laccase Hybrid into a Macrocellular Siliceous Host

“…As already mentioned, this reflects that routes by which electrons reach the copper centers are not particularly discriminating. Not to mention that in the presence of both dioxygen and a highly reducing metal species (i. e. a Pd(0)), we must also consider the presence of a superoxide potentially playing the role of a redox mediator for the enzyme [34] …”

“…Not to mention that in the presence of both dioxygen and a highly reducing metal species (i. e. a Pd(0)), we must also consider the presence of a superoxide potentially playing the role of a redox mediator for the enzyme. [34] Heterogeneous activity: Veratryl alcohol oxidation was performed with hybrid materials 1�UNIK 71 @NH 2 @Si(HIPE) and 1�UNIK 157 @NH 2 @Si(HIPE) as well as with 1 @NH 2 @Si(HIPE) used as control (Figure 4, S7, S8). Catalysts loads of 0.3, 0.6 and 1.2 × 10 À 6 mol g À 1 for hybrids (and up to 35.2 × 10 À 6 mol g À 1 for complex 1) were tested in continuous flow conditions (50 × 10 À 3 g of foam, 15 × 10 À 3 L of mobile phase).…”

Exolaccase-boosted humification for agricultural applications

“…Phenolic compounds are considered as the main “building blocks” of artificial H-LPs. The oxidation efficiency of exolaccase depends on redox potential of T1-Cu site ( Farran et al., 2021 ). As shown in Figure 2 , the mechanism of humification boosted by exolaccase is that T1-Cu into enzyme molecules oxidizes low-molecular-weight phenolics and humic precursors to obtain multitudinous reactive radical intermediates, accompanied by dissolved O 2 consumption at T2/T3-Cu sites ( Sun et al., 2021b ).…”