Contreras David, Rodríguez Jaime, Freer Juanita, Schwederski Brigitte, Kaim Wolfgang
Faculty of Chemical Sciences, University of Concepción, Casilla 160-C, Concepción, Chile.
J Biol Inorg Chem. 2007 Sep;12(7):1055-61. doi: 10.1007/s00775-007-0274-2. Epub 2007 Jul 18.
Brown rot fungi degrade wood, in initial stages, mainly through hydroxyl radicals (.OH) produced by Fenton reactions. These Fenton reactions can be promoted by dihydroxybenzenes (DHBs), which can chelate and reduce Fe(III), increasing the reactivity for different substrates. This mechanism allows the extensive degradation of carbohydrates and the oxidation of lignin during wood biodegradation by brown rot fungi. To understand the enhanced reactivity in these systems, kinetics experiments were carried out, measuring .OH formation by the spin-trapping technique of electron paramagnetic resonance spectroscopy. As models of the fungal DHBs, 1,2-dihydroxybenzene (catechol), 2,3-dihydroxybenzoic acid and 3,4-dihydroxybenzoic acid were utilized as well as 1,2-dihydroxy-3,5-benzenedisulfonate as a non-Fe(III)-reducing substance for comparison. Higher amounts and maintained concentrations of .OH were observed in the driven Fenton reactions versus the unmodified Fenton process. A linear correlation between the logarithms of complex stability constants and the .OH production was observed, suggesting participation of such complexes in the radical production.
褐腐真菌在初始阶段主要通过芬顿反应产生的羟基自由基（·OH）来降解木材。这些芬顿反应可由二羟基苯（DHBs）促进，DHBs能螯合并还原Fe(III)，提高对不同底物的反应活性。这种机制使得在褐腐真菌对木材的生物降解过程中，碳水化合物能被广泛降解，木质素能被氧化。为了理解这些体系中增强的反应活性，开展了动力学实验，通过电子顺磁共振波谱的自旋捕获技术测量·OH的生成。作为真菌DHBs的模型，使用了1,2 - 二羟基苯（儿茶酚）、2,3 - 二羟基苯甲酸和3,4 - 二羟基苯甲酸，以及1,2 - 二羟基 - 3,5 - 苯二磺酸盐作为不还原Fe(III)的物质进行比较。与未改性的芬顿过程相比，在驱动的芬顿反应中观察到了更高的·OH量和维持浓度。观察到络合物稳定常数的对数与·OH生成之间存在线性相关性，表明此类络合物参与了自由基的生成。
