Biotin-avidin technology

Guanaranta and Wilson [111] compared the different methods for immobilization of acetylcholinesterase by direct immobilization on the matrix, introduction of 1,6 diaminohexane as a spacer, and two methods of oriented immobilization via antibody and avidin-biotin linkage. They found that the latter gave the best efficiency, i. e., tenfold higher than direct immobilization on the matrix (which was the lowest) followed by immobilization on the antibody and immobilization using a spacer. Details about the biotin-avidin technology were published by Wilchek and Bayer [112]. 

Chem. Soc., 126, 14411-14418 Skander, M., Malan, C., Ivanova, A. and Ward, TR. (2005) Chemical optimization of artificial metaUoenzymes based on the biotin-avidin technology (S)-selective and solvent-tolerant hydrogenation catalysts via the introduction of chiral amino acid spacers. Chem. Commun., 4815-4817 Ward, TR. (2005) Artificial metallo-enzymes for enantioselective catalysis based on the noncovalent incorporation of organometallic moieties in a host protein. Chem.-Eur. J., 11, 3798-3804 Letondor, C. and Ward, TR. (2006) Artificial metaUoenzymes for enantioselective catalysis Recent advances. Chem. Bio. Chem., 7, 1845-1852. 

Letondor, C., Humbert, N. and Ward, TR. (2005) Artificial metaUoenzymes based on biotin-avidin technology for the enantioselective reduction of ketones by transfer hydrogenation. Proc. Natl. Acad. Sci. U.S.A., 102, 4683-4687 Letondor, C., Pordea, A., Humbert, N., Ivanova, A., Mazurek, S., Novic, M. and Ward, TR. (2006) Artificial transfer hydrogenases based on the biotin-(strept)avidin technology Fine tuning the selectivity by saturation mutagenesis of the host protein. J. Am. Chem. Soc., 128, 8320-8328. 

Thomas CM, Letondor C, Humbert N, Ward TR. Aqueous oxidation of alcohols catalyzed by artificial metalloenzymes based on the biotin-avidin technology. J. Organomet. Chem. 2005 690 4488 491. 

Artificial Metalloenzymes for Enantioselective Catalysis Based on the Biotin-Avidin Technology... 

Key words Allylic alkylation, Artificial metalloenzyme, Biotin-avidin technology, Chemogenetic optimization, Designed evolution, Enantioselective catalysis. Hybrid catalyst. Hydrogenation, Streptavidin, Transfer hydrogenation. 

We reasoned that one could mimic Nature by incorporating cofactors and metal ions to broaden the scope of accessible reactions catalyzed by protein scaffolds. Different approaches for the generation of artificial metalloenzymes have recently been reviewed [2-16]. Herein, we present the developments in the field of artificial metalloenzymes for enantioselective catalysis based on the biotin-avidin technology. The discussion includes a short introduction on the biotin-avidin technology followed by several examples of chemogenetic optimization of the performance of artificial metalloenzymes based on this technology. 

The biotin-avidin technology has found numerous apphcations both in fundamental and in applied research [23, 24]. This widespread technology rehes on the afifmity of biotin towards avidin (K x 10 M ) and the homotetrameric nature of the protein, which allows binding of up to four (different) biotinylated probes. It has been... 

Most applications of the biotin-avidin technology do not rely on the incorporation of the biotinylated probe within the protein environment provided by (strept) avidin. Typically, the introduction of a long spacer (at least five atoms) between the biotin anchor and the probe is recommended (Fig. 1). The biotin-avidin technology can thus be regarded as a molecular velcro that allows the bringing together of up to four biotinylated probes. 

Fig. 1 Basic principle of the biotin-avidin technology. The homotetrameric nature of the protein allows binding of up to four (different) biotinylated probes...

Fig. 2 Biotin-avidin technology Artificial metalloenzymes [M(L )(biotin-ligand)]c(strept)avidin for enantioselective catalysis are based on the anchoring of a catalyticaUy active metal fragment within a host protein via a hgand, a spacer, and biotin. Chemical optimization can be achieved either by varying the spacer or the metal chelate moiety ML ). Saturation mutagenesis at a position close to the metal moiety ( ) can be used for genetic optimization...

Inspired by the visionary paper of Whitesides, we adapted and extended the concept of artificial metalloenzymes (or hybrid catalysts) based on the biotin-avidin technology to enantioselective hydrogenation, transfer hydrogenation, and aUyhc alkylation reactions, which are summarized herein. 

Scheme 1 Artificial metalloenzymes based on the biotin-avidin technology for the hydrogenation of alkenes. Operating conditions used by a Whitesides [34] and b Chan [35]...

In summary, relying on a chemogenetic optimization procedure, we have produced artificial hydrogenases based on the biotin-avidin technology for the enantioselective reduction of N-protected dehydroaminoacids [up to 96% ee (R) and 95% ee (5)] [36, 39]. Next, we outhne our recent findings in artificial aUylic... 

The biotin-avidin technology, often referred to as molecular VcIcto, relies on the very high affinity of biotin for either avidin or streptavidin - (strept)avidin hereafter. The versatility of this technology can be traced back to the following features ... 

As summarized here, artificial metalloenzymes based on the biotin-avidin technology have developed into a versatile approach to enantioselective catalysis. In many cases, selectivities exceeding 92% ee could be obtained, relying on a chemogenetic optimization strategy. Such hybrid catalysts display features which are reminiscent of both homogeneous and enzymatic catalysis. 

C. Letondor, N. Humbert, T. R. Ward, Artificial metalloenzymes based on biotin-avidin technology for the enantioselective reduction of ketones by transfer hydrogenation, Proc. Natl. Acad. Sci. USA, 2005, 102, 4683-4687. 

J. Pierron, C. Malan, M. Creus, J. Gradinaru, I. Hafner, A. Ivanova, A. Sardo, T. R. Ward, Artificial metalloenzymes for asymmetric allylic alkylation on the basis of the biotin-avidin technology, Angew. them. Int. Ed., 2008, 47, 701-705. 

U. E. Rusbandi, C. Lo, M. Skander, A. Ivanova, M. Creus, N. Humbert, T. R. Ward, Second generation artificial hydrogenases based on the biotin-avidin technology improving activity, stability and selectivity by introduction of enantiopure amino acid spacers, Adv. Synth. Catal., 2007, 349, 1923-1930. 

For a review on artificial metalloenzymes based on the biotin-avidin technology T. R. Ward, Acc. Chem. Res., 2011,44, 47. 

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