Department of Chemical Engineering, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea.
Department of Chemistry, Kangwon National University, Chunchon, 24341, Republic of Korea.
Small. 2018 Dec;14(52):e1803377. doi: 10.1002/smll.201803377. Epub 2018 Nov 20.
Coacervation of mussel adhesive proteins (MAPs) is proposed as a potential strategy that mussels may use during secretion due to their high concentration density, lack of dispersion into seawater, and low interfacial tension. Particularly, coacervations of interfacial MAPs, foot protein type-3 fast variant (fp-3F) and type-5 (fp-5), are important in the initial mussel adhesion process due to the relationship between the easy secretion/surface wetting properties of the coacervate and primer-like surface adhesive role of interfacial MAPs, which directly contact the marine surface. To the best of the authors' knowledge, this is the first report on coacervate formation of major recombinant interfacial MAPs with high charge densities and the highest 3,4-dihydroxyphenylalanine (Dopa) contents. Specifically, salt-induced coacervation of fp-3F is observed at low pH values corresponding to the acidified environment of the distal depression during mussel secretion. In addition, it shows enthalpy driven upper critical solution temperature behavior, possibly relying on bridging interactions between like-charged cationic fp-3Fs including salt-bridge and cation-π/π-π interactions in the presence of specific counterions, supported by Raman spectroscopy. It is believed that this study has broadened the scope of the understanding of coacervation of MAPs and may provide new insight for responsive biomaterial design.
贻贝黏附蛋白（MAPs）凝聚被认为是贻贝在分泌过程中可能采用的一种潜在策略，因为它们具有高浓度密度、缺乏在海水中的分散以及低界面张力。特别是界面 MAPs（足蛋白 3 型快变体（fp-3F）和 5 型（fp-5））的凝聚在初始贻贝黏附过程中非常重要，因为凝聚物易于分泌/表面润湿的特性以及界面 MAPs 的类似底漆的表面黏附作用之间存在关系，界面 MAPs 直接与海洋表面接触。据作者所知，这是首次报道具有高电荷密度和最高 3,4-二羟基苯丙氨酸（Dopa）含量的主要重组界面 MAPs 的凝聚体形成。具体而言，在 fp-3F 的低 pH 值下观察到盐诱导的凝聚，这对应于贻贝分泌过程中远侧凹陷的酸化环境。此外，它显示出焓驱动的上临界溶液温度行为，可能依赖于带相同电荷的阳离子 fp-3Fs 之间的桥接相互作用，包括在存在特定抗衡离子的情况下盐桥和阳离子-π/π-π相互作用，这得到了拉曼光谱的支持。相信这项研究拓宽了对 MAPs 凝聚的理解范围，并可能为响应性生物材料设计提供新的见解。
