α-Helix-Mediated Protein Adhesion

Abstract

Proteins have been adopted by natural living organisms to create robust bioadhesive materials, such as biofilms and amyloid plaques formed in microbes and barnacles. In these cases, β-sheet stacking is recognized as a key feature that is closely related to the interfacial adhesion of proteins. Herein, we challenge this well-known recognition by proposing an α-helix-mediated interfacial adhesion model for proteins. By using bovine serum albumin (BSA) as a model protein, it was discovered that the reduction of disulfide bonds in BSA results in random coils from unfolded BSA dragging α-helices to gather at the solid/liquid interface (SLI). The hydrophobic residues in the α-helix then expose and break through the hydration layer of the SLI, followed by the random deposition of hydrophilic and hydrophobic residues to achieve interfacial adhesion. As a result, the first assembled layer is enriched in the α-helix secondary structure, which is then strengthened by intermolecular disulfide bonds and further initiates stepwise layering protein assembly. In this process, β-sheet stacking is transformed from the α-helix in a gradually evolving manner. This finding thus indicates a valuable clue that β-sheetfeaturing amyloid may form after the interfacial adhesion of proteins. Furthermore, the finding of the α-helix-mediated interfacial adhesion model of proteins affords a unique strategy to prepare protein nanofilms with a well-defined layer number, presenting robust and modulable adhesion on various substrates and exhibiting good resistance to acid, alkali, organic solvent, ultrasonic, and adhesive tape peeling.

Interface-mediated protein aggregation

“…Recently, a novel film material system was built through such amyloid-like aggregation of BSA, 64–66 providing new insight into protein interfacial adhesion. Previous studies on protein adhesion have identified β-sheet stacking as a key feature closely associated with the interfacial adhesion of proteins.…”

Protein-based bioactive coatings: from nanoarchitectonics to applications

“…Likewise, in another instance, barnacles employ their cement to achieve firm adhesion to reef or boat surfaces, employing a composition primarily dominated by amyloid-like components rich in b-sheet motifs. 98 In contrast to earlier reports outlining the surface adhesion of proteins mediated by b-sheet stacking, Zhang and Yang et al 142 proposed an a-helix-mediated interfacial adhesion model of proteins (Fig. 6d).…”

“…In addition, intermolecular disulfide crosslinking within the adsorption layer further contributed to this adhesion phenomenon. 142 In summary, protein adhesion to interfaces involves a nuanced interplay of adsorption, molecular recognition, conformational changes, thermodynamics, and desorption. Biochemists play a central role in unraveling these complex mechanisms and applying their knowledge to diverse applications while addressing the challenges posed by the multifaceted nature of protein–interface interactions.…”

Synthetic Polypeptide Bioadhesive Based on Cation−π Interaction and Secondary Structure

“…For sample K L25 BE L25 , the α-helix content is 55% and the β-sheet content is 45%, whereas for sample K L25 BE D25 , the α-helix content is 30% and the β-sheet content is 70%. A higher α-helix content is correlated with a stronger adhesive strength, potentially attributed to the increased exposure of side groups at the polypeptide surface due to α-helical structure, providing enhanced interfacial adhesion with the substrate (Figure g) . Then the helical content of K L35 BE L15 and K L15 BE L35 was further calculated according to FT-IR spectra (Figure e and f).…”

“…A higher α-helix content is correlated with a stronger adhesive strength, potentially attributed to the increased exposure of side groups at the polypeptide surface due to α-helical structure, providing enhanced interfacial adhesion with the substrate (Figure 3g). 53 Then the helical content of K L35 BE L15 and K L15 BE L35 was further calculated according to FT-IR spectra (Figure 3e and 3f). Among K L35 BE L15 , K L25 BE L25 , and K L15 BE L35 , the helical content increases with the increasing ratio of benzyl glutamate, which can be attributed to the high helical propensity of poly(benzyl glutamate) chains.…”