A double-modification strategy for enhancing charge density of mono-sized beads for facilitated refolding of like-charged protein

Charged Surface Regulates the Molecular Interactions of Electrostatically Repulsive Peptides by Inducing Oriented Alignment

Regulation of molecular orientation of charged dipeptides and involved interactions by electrostatic repulsion from like-charged surfaces were studied using all-atom molecular dynamics simulations. It was found that a charged surface can induce oriented alignment of like-charged peptides, and the oriented alignment leads to enhanced electrostatic repulsion between the peptide molecules. The findings are consistent with previous experimental results about the inhibition of charged protein aggregation using like-charged ion-exchange resin. Furthermore, the simulations provided molecular insights into this process, and demonstrated the distinct regulation effect of like-charged surfaces on the molecular interactions between peptides that possess an electric dipole structure. Both the charged surface and the electric dipole structure of peptides were confirmed to be crucial for the regulation. The research is expected to facilitate the rational design of surfaces or devices to regulate the behavior of amphoteric molecules such as proteins for both in vivo and in vitro applications, which would contribute to the regulation of protein-protein interactions and its application in life science and biotechnology.

Enhanced protein adsorption and facilitated refolding of like-charged protein with highly charged silica nanoparticles fabricated by sequential double modifications

Silica nanoparticles (SNPs) were sequentially modified with poly(ethylenimine) (PEI) and 2-diethylaminoethyl chloride (DEAE) to prepare a series of positively charged SNPs-PEI and SNPs-PEI-DEAE. The sequential double-modification strategy produced a charge density as high as 1740 μmol/g (4524 μmol/mL), which offered a very high adsorption capacity for bovine serum albumin (314 mg/g). Most importantly, the highly charged SNPs-PEI and SNPs-PEI-DEAE could efficiently facilitate the refolding of like-charged protein at extremely low utilization. For instance, in the refolding of 1 mg/mL lysozyme, the refolding yield reached 75% with only 3.3 μL/mL SNPs-PEI-DEAE. The bead consumption was reduced by nearly 96% as compared to that of the charged microspheres used previously to reach a similar yield. The results proved that the polyelectrolyte-modified SNPs were promising for applications in facilitating like-charged protein refolding, and the research opened up a new way for biotechnology applications of highly charged nanoparticles.