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Researchers Gain Insight into Trace Water in Process of Peptide Self-assembly

Dec 15, 2017

Water environment, especially bond-water molecules around the biomolecules (e.g. proteins/peptides), can stabilize and alter the structures/dynamics of proteins, and trigger life’s functions or induce various diseases. 

However, the detecting of the role of water molecules in the process of proteins/peptide self-assembly, the early stage in particular, still has limitations.  

Recently, researchers led by Prof. YAN Xuehai from the Institute of Process Engineering (IPE) of the Chinese Academy of Sciences (CAS) put forward a strategy to gain insight into the key role of trace water in peptide self-assembly by using ionic liquids (ILs) as a biomimetic medium. ILs can provide a suitable non-aqueous environment to mediate the content of trace water, enabling the researchers follow the dynamic evolution of peptide self-assembly.  

Researchers used diphenylalanine (FF) as a model building block for the formation of stable noncovalent FF nanotubes (NTs), focusing on the early stage of nucleation and interactions between water and FF peptide molecules.  

They found that the whole FF self-assembly process contains three steps: nucleation, aggregation of nuclei, and growth for formation of NTs (Fig. 1), and the assembly rate of FF peptide can be controlled by the content of trace water. 

 

Fig 1. Schematic depiction of the dynamic evolution of FF self-assembly in IL with the increase of water content in IL. (Image by YAN Xuehai et al.) 

Moreover, the molecular dynamic simulation results show that in the early stage of FF nucleation, trace water molecules are essential for the formation of stable noncovalent FF oligomers. As shown in Fig. 2, although peptides themselves present a strong spatial correlation or aggregation trend, water molecules present key pioneers to induce the aggregation of FF oligomers.  

 

Fig. 2. Snapshots of the aggregation process of water molecules and peptide in IL at (a) 90 ns, (b) 470 ns, (c) 560 ns, (d) 3000 ns. Radial distribution functions between (e) peptide and water, (f) peptide and peptide. (Image by YAN Xuehai et al.) 

Their finding provides new perspectives on the important role of trace water molecules in mediating biomolecular self-assembly.  

Their work entitled "Trace Water as Prominent Factor to Induce Peptide Self-Assembly: Dynamic Evolution and Governing Interactions in Ionic Liquids" was published in Small. 

The research team also includes a group led by ZHANG Suojiang from IPE (providing theoretical calculation to this work), and a group led by WANG Yilin from Institute of Chemistry, CAS (providing the ITC measurement to this work). Prof. CHEN Shimou (IPE) was thanked for his help in measuring high-resolution TEM.  

The research was financially supported by the National Natural Science Foundation of China, the Talent Fund of the Recruitment Program of Global Youth Experts, the Key Research Program of Frontier Sciences of Chinese Academy of Sciences, and the CAS President’s International Fellowship Initiative.  

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