A spectroscopic characterization of a phenolic natural mediator in the laccase biocatalytic reaction

• Spectroscopic study of Coriolopsis gallica laccase in the presence of acetosyringone.
• Detection of acetosyringone radical intermediate produced by laccase.
• Radical species assignment through multifrequency ESR aided by computer simulation.
• Characterization of the final products by NALDI-TOF mass.

Multi-frequency ESR combined with NALDI-TOF MS has been used for the characterization of 3,5-dimethoxy-4-hydroxyacetophenone radical intermediate and by-products formed during the Coriolopsis gallica laccase catalytic reaction. A stable radical species is formed and an intense and well-structured ESR spectrum was detected and fully characterized at S-, X- and W-bands. The presence of by-products generated as the result of by-reactions has been investigated and analyzed through NALDI-TOF MS, performing the experiments versus time. The superior radical stability of such phenoxy radical, due to steric hindrance in ortho to the phenol group and the great delocalization of the unpaired electron on the acetyl substituent, makes acetosyringone particularly interesting for biotechnological applications. This represents a good example for the development of new stable laccase mediator molecules.

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