Tyrosine radicals are notoriously short-lived/unstable in solution, while they present an impressive degree of stability and versatility in bioenzymes. Herein, we have developed a library of hybrid biomimetic materials (HBMs), which consists of tyrosine-containing oligopeptides covalently grafted on SiO₂ nanoparticles, and studied the formation, lifetime, and redox properties of tyrosyl radicals. Using electron paramagnetic resonance spectroscopy, we have studied the radical-spin distribution as a probe of the local microenvironment of the tyrosyl radicals in the HBMs. We find that the lifetime of the tyrosyl radical can be enhanced by up to 6 times, by adjusting three factors, namely, a proximal histidine, the length of the oligopeptide, and the interface with the SiO₂ nanomatrix. This is shown to be correlated to a significant lowering of E_1/2 from +736 mV, in free tyrosine, to +548 mV in the {12-peptide}@SiO₂ material. Moreover, we show that grafting on SiO₂ lowers the E_1/2 of tyrosine radicals by ∼50 mV in all oligopeptides. Analysis of the spin-distribution by EPR reveals that the positioning of a histidine at a H-bonding distance from the tyrosine further favors tyrosine radical stabilization.

中文翻译：

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{SiO2@Oligopeptide}杂化仿生材料对酪氨酰自由基稳定性的控制

众所周知，酪氨酸自由基在溶液中的寿命短/不稳定，而它们在生物酶中表现出令人印象深刻的稳定性和多功能性。在此，我们开发了一个杂化仿生材料 (HBM) 库，该库由共价接枝在 SiO ₂纳米颗粒上的含酪氨酸寡肽组成，并研究了酪氨酰自由基的形成、寿命和氧化还原特性。使用电子顺磁共振光谱，我们研究了自由基自旋分布，作为 HBM 中酪氨酰自由基局部微环境的探针。_{我们发现，通过调整近端组氨酸、寡肽长度和与 SiO 2}的界面三个因素，酪氨酰自由基的寿命可提高 6 倍。纳米基质。这表明与E _1/2从游离酪氨酸中的 +736 mV显着降低到 {12-肽}@SiO ₂材料中的 +548 mV 相关。此外，我们表明在 SiO ₂上接枝可降低所有寡肽中酪氨酸自由基的E _1/2约 50 mV。EPR 对自旋分布的分析表明，将组氨酸定位在距酪氨酸的氢键距离处进一步有利于酪氨酸自由基的稳定。