Mirshafian Razieh, Wei Wei, Israelachvili Jacob N, Waite J Herbert
Marine Science Institute, University of California , Santa Barbara, California 93106, United States.
Department of Chemical Engineering, University of California , Santa Barbara, California 93106, United States.
Biochemistry. 2016 Feb 9;55(5):743-50. doi: 10.1021/acs.biochem.5b01177. Epub 2016 Jan 22.
Dopa (l-3,4-dihydroxyphenylalanine) is a key chemical signature of mussel adhesive proteins, but its susceptibility to oxidation has limited mechanistic investigations as well as practical translation to wet adhesion technology. To investigate peptidyl-Dopa oxidation, the highly diverse chemical environment of Dopa in mussel adhesive proteins was simplified to a peptidyl-Dopa analogue, N-acetyl-Dopa ethyl ester. On the basis of cyclic voltammetry and UV-vis spectroscopy, the Dopa oxidation product at neutral to alkaline pH was shown to be α,β-dehydro-Dopa (ΔD), a vinylcatecholic tautomer of Dopa-quinone. ΔD exhibited an adsorption capacity on TiO2 20-fold higher than that of the Dopa homologue in the quartz crystal microbalance. Cyclic voltammetry confirmed the spontaneity of ΔD formation in mussel foot protein 3F at neutral pH that is coupled to a change in protein secondary structure from random coil to β-sheet. A more complete characterization of ΔD reactivity adds a significant new perspective to mussel adhesive chemistry and the design of synthetic bioinspired adhesives.
多巴（l-3,4-二羟基苯丙氨酸）是贻贝粘附蛋白的关键化学特征，但其易氧化的特性限制了机理研究以及向湿粘附技术的实际转化。为了研究肽基多巴的氧化，贻贝粘附蛋白中多巴高度多样的化学环境被简化为一种肽基多巴类似物，N-乙酰多巴乙酯。基于循环伏安法和紫外-可见光谱，中性至碱性pH条件下的多巴氧化产物被证明是α,β-脱氢多巴（ΔD），一种多巴醌的乙烯基儿茶酚互变异构体。在石英晶体微天平中，ΔD对二氧化钛的吸附能力比多巴同系物高20倍。循环伏安法证实了在中性pH条件下贻贝足蛋白3F中ΔD形成的自发性，这与蛋白质二级结构从无规卷曲向β-折叠的变化相关。对ΔD反应性的更完整表征为贻贝粘附化学和合成仿生粘合剂的设计增添了重要的新视角。
