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Supramolecular Catalysis. Part 2: Artificial Enzyme Mimics Matthieu Raynal, Pablo Ballester, Anton Vidal-Ferran, Piet W

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Supramolecular Catalysis. Part 2: Artificial Enzyme Mimics Matthieu Raynal, Pablo Ballester, Anton Vidal-Ferran, Piet W Supramolecular catalysis. Part 2: artificial enzyme mimics Matthieu Raynal, Pablo Ballester, Anton Vidal-Ferran, Piet W. N. M. van Leeuwen To cite this version: Matthieu Raynal, Pablo Ballester, Anton Vidal-Ferran, Piet W. N. M. van Leeuwen. Supramolecular catalysis. Part 2: artificial enzyme mimics. Chemical Society Reviews, Royal Society of Chemistry, 2014, 43 (5), pp.1734-1787. 10.1039/C3CS60037H. hal-01637213 HAL Id: hal-01637213 https://hal.sorbonne-universite.fr/hal-01637213 Submitted on 21 Nov 2017 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Journal Name Dynamic Article Links ► Cite this: DOI: 10.1039/c0xx00000x www.rsc.org/xxxxxx ARTICLE TYPE Supramolecular catalysis: Part 2: Artificial enzyme mimics. Matthieu Raynal,*a,b Pablo Ballester,a,c Anton Vidal-Ferrana,c and Piet W. N. M. van Leeuwena Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX 5 DOI: 10.1039/b000000x The design of artificial catalysts able to compete with the catalytic proficiency of enzymes is an intense subject of research. Non-covalent interactions are thought to be involved in several properties of enzymatic catalysis, notably: i) the confinement of the substrates and the active site within a catalytic pocket, ii) the creation of a hydrophobic pocket in water, iii) self-replication properties and iv) allosteric 10 properties. The origins of the enhanced rates and high catalytic selectivities associated with these properties are still a matter of debate. Stabilisation of the transition state and favourable conformations of the active site and the product(s) are probably part of the answer. We present here artificial catalysts and biomacromolecule hybrid catalysts which constitute good models towards the development of truly competitive artificial enzymes. 15 1. Introduction ____________________________________________________________________ 2 2. Catalysis within a confined environment _____________________________________________ 2 2.1 Binding site in close proximity to a catalytic or a reactive centre ______________________________ 2 2.2 Host-guest catalysis __________________________________________________________________ 9 2.2.1 Covalent hosts ____________________________________________________________________________ 10 20 2.2.2 Non-covalent hosts _________________________________________________________________________ 16 3. Catalysis in water _______________________________________________________________ 20 3.1 Hydrophobic interactions _____________________________________________________________ 20 3.2 Catalysis in micelles and vesicles _______________________________________________________ 20 3.3 Catalysis inside rigid hosts ____________________________________________________________ 23 25 4. Self-replicators _________________________________________________________________ 25 5. Allosteric catalysis ______________________________________________________________ 31 6. Biomacromolecule and peptide hybrids as organic and inorganic catalysts _________________ 34 7. Conclusions ____________________________________________________________________ 40 Notes and references ______________________________________________________________ 40 30 Acknowledgement ________________________________________________________________ 40 References ______________________________________________________________________ 40 [journal], [year], [vol], 00–00 | 1 CREATED USING THE RSC ARTICLE TEMPLATE (VER. 3.0) - SEE WWW.RSC.ORG/ELECTRONICFILES FOR DETAILS ARTICLE TYPE www.rsc.org/xxxxxx | XXXXXXXX to other catalytic aspects such as transition state stabilisation. 1. Introduction However, secondary interactions also played a role in others functions displayed by enzymes. In water, the construction of a A conventional route to produce an effective artificial enzyme is 60 hydrophobic pocket allows for a close proximity between the to reproduce the sometimes elusive structure of the enzyme active reactive centre and the reactants. In self-replication, autocatalysis 1 5 site (model enzymes). An alternative relies on mimicking the is also achieved by facilitating the contact between the reactants. functions of enzymes without copying its structure (enzyme This analogy encourages us to incorporate in this review artificial models or mimics). Following the Pauling principles, non- catalysts mimicking these enzyme functions. The reversibility of covalent interactions were designed to recreate these properties 65 non-covalent interactions is also used for the design of allosteric 2–4 with artificial systems. catalysts. This field is increasing greatly with the aim of 10 In the 1970s the first supramolecular catalytic examples developing catalysts that can be easily switched and modulated featured under the heading of host-guest chemistry or catalysis, during the catalytic process. and enzymes were the source of inspiration.5–10 The main idea Rebek pioneered the field of enzyme mimics. He studied a pursued was the use of the lock-and-key principle borrowed from 70 variety of supramolecular catalysts which copy different the knowledge on enzymes; a substrate fits nicely in a host functions of enzymes. Probably encouraged by the analogy 15 molecule that also carries a catalytic function thus enhancing the between the various properties of enzymes, he developed rate of reaction, while spatial factors may induce regioselectivity. cavitands for host-guest catalysis, very early examples of self- Alternatively, two substrates may bind into a cavity and undergo replicators,32 and allosteric catalysts.33 for instance a selective Diels–Alder reaction. 75 We wish to incorporate in this review efficient artificial It is not surprising that cyclodextrins constitute the first hosts catalysts which copy different properties of enzymes. Metal or 20 used to reproduce the enzyme hydrophobic pocket at a small organic catalysts will be classified according to the enzyme 11 molecular level. The pioneering works of Breslow and Tabushi properties they copy, but not the nature of the reaction catalysed. inspired subsequent research and highly efficient catalytic Hybrids between a biomacromolecule or a peptide and a metal or systems, working under enzyme conditions (pH, 80 an organic catalyst will also be mentioned in section 6. temperature).12,13 It’s worth mentioning that previous reviews usually focus on 25 Bringing together the reactive site and the substrate(s) is a one property of enzyme mimics. Our aim was to stress how strategy commonly used in classical homogeneous catalysis. For supramolecular interactions can be used to copy the various example, the reactivity of a C–H bond is increased by functions of enzymes.34,35 These catalysts offer innovative incorporating a directing group in the substrate that will 85 approaches toward a better understanding of the enzyme´s mode coordinate the metal centre and bring the targeted bond in close of action but in addition they can be useful for the discovery of 30 proximity to the metal. However, in catalysis involving a host and unprecedented reactivity. We will highlight efficient and recent one or several guests, concentration of the reactants near of the examples but older references will also be provided. reactive centre is not the only advantage. Desolvation of the reactants/transition state, stabilisation of the transition state, 2. Catalysis within a confined environment favourable conformation of the product within the catalytic 35 pocket are other important parameters that occur in enzyme 90 2.1 Binding site in close proximity to a catalytic or a reactive catalysis and that can be used to design artificial catalysts. centre Some systems are simple and the development may have been Enzyme models were designed following the idea that increasing relatively fast, but others are rather complicated and their the concentration of a substrate around its reactive centre should development and synthesis, for example those involving covalent lead to reaction rate enhancement. In enzymatic catalysis and 40 hosts, may have required several years. Cram reported the thirty- 95 biocatalysis, secondary interactions hold the substrate near the step synthesis of a cryptand incorporating a reactive centre as a catalytic centre in a favourable position and as a result rate 14 15 mimic of chymotrypsin! Dendrimers, molecularly imprinted enhancements up to 1010 mol.L-1.s-1 have been observed. 16–19 20 polymers and catalytic antibodies also constituted old Initially, small supramolecular catalysts were considered approaches inspired by the ability of enzymes to stabilise which combined a binding site linked to a reactive centre. 21–23 45 transition states. 100 Likewise, catalysts acting as templates and possessing two or In the last ten years, innovative systems were designed based more binding sites bringing together the two reactants were on the well-defined construction of cages and spheres through investigated.46–49 More recently, host molecules and 24,25 26 ligand-metal interactions. Fujita and Raymond and Bergman supramolecules capable of
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