ical-assisted depolymerization of plastics so far only works for polyethylene terephthalate, with degradation of a few other relevant synthetic polymer chains being reported. In contrast, by analyzing market data and emerging trends for synthetic fibers in the textile industry, in combination with numbers from used garment collection and sorting plants, it was shown that the use of difficult-to-recycle blended materials is rapidly growing. If the lack of recycling technology and production trend for fiber blends remains, a volume of more than 3400 Mt of waste will have been accumulated by 2030. This work highlights the urgent need to transform the textile industry from a biocatalytic perspective.
In order to estimate the size of the cavity remaining around the heme of the 3A3-microperoxidase 8 (MP8) hemoabzyme, the formation of 3A3-MP8-Fe(II)-nitrosoalkane complexes upon oxidation of N-monosubstituted hydroxylamines was examined. This constituted a new reaction for hemoabzymes and is the first example of fully characterized Fe(II)-metabolite complexes of antibody-porphyrin. Also, via a comparison of the reactions with N-substituted hydroxylamines of various size and hydrophobicity, antibody 3A3 was confirmed to bring about a partial steric hindrance on the distal face of MP8. Subsequently, the influence of the antibody on the stereoselectivity of the S-oxidation of sulfides was examined. Our results showed that MP8 alone and the antibody-MP8 complex catalyze the oxidation of thioanisole by H 2 O 2 and tert-butyl hydroperoxide, following a peroxidase-like two-step oxygen-transfer mechanism involving a radical-cation intermediate. The best system, associating H 2 O 2 as oxidant and 3A3-MP8 as a catalyst, in the presence of 5% tert-butyl alcohol, led to the stereoselective S-oxidation of thioanisole with a 45% enantiomeric excess in favour of the R isomer. This constitutes the highest enantiomeric excess reported to date for the oxidation of sulfides catalyzed by hemoabzymes.Keywords: artificial hemoproteins; abzymes; nitrosoalcanes; microperoxidase 8; S-oxidation.Catalytic antibodies with a metalloporphyrin cofactor, or ÔhemoabzymesÕ, are not as efficient a category of catalysts as their natural hemoprotein counterparts. The hemoabzymes, which display a peroxidase activity, are characterized by k cat /K m values that are three to four orders of magnitude lower than those for natural peroxidases [1]. The relatively low efficiency of these porphyrin-antibody complexes is probably the result, at least in part, of the fact that no proximal ligand of the iron has been induced in these antibodies. To avoid this problem, we decided to use, as a hapten, microperoxidase 8 (MP8), a heme octapeptide where the imidazole side-chain of histidine 18 acts as a proximal ligand of the iron atom. A set of six monoclonal antibodies was thus obtained: the best peroxidase activitythat found with the complex of MP8 and one of those antibodies, 3A3 -was characterized by a k cat /K m value of 2 · 10, the best ever reported for an antibodyporphyrin complex [2]. Active-site topology studies suggested that the binding of MP8 occurred through interactions of its carboxylate substituents with amino acids of the antibody, and that the protein provided a partial steric hindrance of the distal face of the heme [2]. In addition, it was shown recently that 3A3-MP8 was a more efficient catalyst for the nitration of phenol by NO 2 -/H 2 O 2 than MP8 alone, and that the antibody protein not only protected MP8 against oxidative degradations but also induced a regioselectivity of the reaction in favor of the formation of 2-nitrophenol [3]. Consequently, it was tempting to examine whether the hemoabzyme 3A3-MP8 was able to catalyze the selective ...
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