Surfactant-like Properties of an Amphiphilic α-Helical Peptide Leading to Lipid Nanodisc Formation

Abstract

Nanodiscs are self-assembled discoidal nanoparticles composed of amphiphilic α-helical scaffold proteins or peptides that wrap themselves around the circumference of a lipid bilayer in a beltlike manner. In this study, an amphiphilic helical peptide that mimics helix 10 of human apoA-I was newly synthesized by solid phase peptide synthesis using Fmoc chemistry, and its physicochemical properties, including surface tension, self-association, and solubilization abilities, were evaluated and related directly to nanodisc formation. The synthesized peptide having hydrophobic and hydrophilic faces behaves like a general surfactant, affording a critical association concentration (CAC) of 2.7 × 10(-5) M and a γCAC of 51.2 mN m(-1) in aqueous solution. Interestingly, only a peptide solution above its CAC was able to microsolubilize L-α-dimyristoylphosphatidylcholine (DMPC) vesicles, and lipid nanodiscs with an average diameter of 9.5 ± 2.7 nm were observed by dynamic light scattering and negative stain transmission electron microscopy. Moreover, the ζ potentials of the lipid nanodiscs were measured for the first time as a function of pH, and the values changed from positive (20 mV) to negative (-30 mV). In particular, nanodisc solutions at acidic pH 4 (20 mV) or basic pH 9 (-20 mV) were found to be stable for more than 6 months as a result of the electrostatic repulsion between the particles.

Minimum Amino Acid Residues of an α-Helical Peptide Leading to Lipid Nanodisc Formation

“…Although we previously demonstrated that CAC values of peptides are important for nanodisc formation 18 , the minimum number of amino acid resides for effective nanodisc formation was investigated at a constant peptide concentration in this study. Vortexing of the peptides 22-, 18-, or 14-mers possessing more than 14 amino acids rapidly cleared turbid DMPC liposome solutions while solutions remained largely turbid or became slightly transparent when peptides with less than 12 amino acids 12-, 10-, 8-, or 6-mers were used, suggesting nanodisc formation with the former peptides.…”

“…Based on our previous work 18 , 0.3 mM peptide solutions were mixed with various amounts of DMPC liposomes, 2.5:1, peptide : DMPC , to confirm the formation of nanodiscs with phospholipids. Although we previously demonstrated that CAC values of peptides are important for nanodisc formation 18 , the minimum number of amino acid resides for effective nanodisc formation was investigated at a constant peptide concentration in this study.…”

“…The use of surfactants is avoided wherever possible, because they are often reported to denature proteins or peptides and their complete removal is difficult. Recently, we have succeeded in the artificial synthesis of an amphiphilic α-helical 22-mer peptide NH 2 -PVLES-FKASFLSALEEWTKKLN-NH 2 that mimics and modifies helix 10 of the human apoA-I protein residues 220-241 18 .…”

Interfacial and Emulsifying Properties of Soybean Peptides with Different Degrees of Hydrolysis

“…Other interesting features of peptides include their molecular interactions, such as hydrogen bonds, van der Waals forces, electrostatic, aromatic π-π stacking , hydrophobic and hydrophilic interactions 5 . The synthesis of surfactant-like peptides that mimic an amphiphilic helical unit of apolipoprotein A-I apoA-I was successfully executed by the present authors 6 . These peptides exhibit rather high surface activity as well as solubilizing ability toward lipids, and their amphiphilicity is derived from the localization of hydrophobic and hydrophilic amino acids in their α-helical structures.…”

DNA-Encircled Lipid Bilayers

“…[1][2][3][4][5] As in vivo investigations are often very challenging, such functional implications of lipid protein interactions 6 can be more easily studied in vitro with artificial membrane-mimetic systems which provide a native-like lipid environment. For example, planar discoidal nanoscale lipid bilayers surrounded by amphipathic polymers 7 or surfactant-like helical peptides 8 have been described. Discoidal planar bilayers are mostly assembled from dimeric apolipoprotein AI-derived proteins, which encircle a lipid bilayer, thereby sealing its hydrophobic rim.…”