Cross-Linked Artificial Enzyme Crystals as Heterogeneous Catalysts for Oxidation Reactions

Abstract

Designing systems that merge the advantages of heterogeneous catalysis, enzymology, and molecular catalysis represents the next major goal for sustainable chemistry. Cross-linked enzyme crystals display most of these essential assets (well-designed mesoporous support, protein selectivity, and molecular recognition of substrates). Nevertheless, a lack of reaction diversity, particularly in the field of oxidation, remains a constraint for their increased use in the field. Here, thanks to the design of cross-linked artificial nonheme iron oxygenase crystals, we filled this gap by developing biobased heterogeneous catalysts capable of oxidizing carbon-carbon double bonds. First, reductive O activation induces selective oxidative cleavage, revealing the indestructible character of the solid catalyst (at least 30 000 turnover numbers without any loss of activity). Second, the use of 2-electron oxidants allows selective and high-efficiency hydroxychlorination with thousands of turnover numbers. This new technology by far outperforms catalysis using the inorganic complexes alone, or even the artificial enzymes in solution. The combination of easy catalyst synthesis, the improvement of "omic" technologies, and automation of protein crystallization makes this strategy a real opportunity for the future of (bio)catalysis.

High mobility of lattice molecules and defects during the early stage of protein crystallization

“…Our observations provide direct evidence of the true nature of the macromolecular crystalline lattice, which is much more flexible and more dynamic than previously assumed, and expand on current knowledge of the potential use of protein crystals as functional materials, as has been recently reported. [26][27][28] Results and Discussion During the in situ LC-TEM imaging, we observed the dynamics of defect inside orthorhombic and tetragonal crystals of lysozyme, which can be observed under our experimental conditions (see Experimental section). 29 An elongated orthorhombic crystal and a pseudo-hexagonal-shaped tetragonal crystal are shown in the same field of view in Fig.…”

Artificial Metalloproteins: At the Interface between Biology and Chemistry

“…More recently, Ménage and co-workers described how they were able to re-engineer the ArM crystals into heterogeneous catalysts that oxidize exogenous substrates. 40 The active site was modified by redesigning the Fe complex used in the previous study via substituting functional groups at the reactive C–H bonds of the aromatic rings on L to prevent intramolecular hydroxylation ( Figure 4 ). To increase the stability of crystals, they cross-linked the protein molecules within the lattice.…”

LEAFY protein crystals with a honeycomb structure as a platform for selective preparation of outstanding stable bio-hybrid materials

“…Moreover, the presence of the additional ruthenium complex in the crystal could also explain the observed broadening of the band. Then, as described in the method section 47,53 Raman spectroscopy measurements were performed on a powder of NH2-Ru-Cl, on a crystal of native LEAFYK84C, as well as on the biomaterials Ru-16 OH2  LEAFYK84C and Ru-18 OH2  LEAFYK84C formed in a solution containing H2 16 O and H2 18 O respectively. When using an excitation source near the maximum absorption of the MLCT (514 nm) the fluorescence reemitted by samples were observed to be unmanageable and prevented measuring Raman data at the resonance.…”

“…Taking advantage of both the versatility of synthetic materials and the properties of controlled assembly of biomolecules, several biohybrid systems combining either nanoparticles, organic synthetic molecules or metal complexes on or within a protein assembly were reported for applications in various domains such as biocatalysis, nanodevices, medical imaging, drug delivery, diagnosis and therapy. [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] Yet, even if it is a field in full expansion, the variety and the number of proteins used remains poorly exploited despite their high potential. This is particularly true for protein crystals that appear to be promising candidates for the design of functional materials since they offer the following advantageous properties: i) a highly ordered monomers arrangements that form a variety of porous structures, ii) a confined and chiral interior space with solvent-filled channels that allows the diffusion of various small functional molecules, iii) a high catalyst loading capacity can be expected due to high molecular concentrations and finally iv) the possibility to design improved biocatalysts guided by the atomic resolution details of crystal structures.…”