Refolding of the Four Helical Fragments of Barstar on Gold Nanoparticles.

The correct folding of proteins is a prerequisite for their biological functions, but the secret of protein folding is still not fully understood. Recently, a new theory of protein folding was proposed: the Confined Lowest Energy Fragment (CLEF) hypothesis, which can explain protein folding experiments well. According to the CLEF hypothesis, all proteins can be divided into independent folding units (CLEF fragments), which can even refold into their native conformation via suitable nanoparticle (NP)-peptide interactions. This opens the door to creating artificial proteins by restoring the native conformations and functions of protein fragments on NPs. To verify this prediction, herein, we demonstrate that peptides corresponding to the four helixes of the barstar protein, which are basically in a random coil conformation on their own, can refold into α-helixes on gold NPs (AuNPs) without their original neighboring fragments in barstar. Our results show that the seemingly indispensable long-range interactions within proteins, which are considered indispensable and mysterious, can be replaced by simple interactions with NPs, such as, Au─N bonds between the fragments and AuNPs. This study provides new evidence for the CLEF theory and adds a new tool to the toolbox for creating NP-based artificial proteins.