Aqueous Self-Assembly within the Homologous Peptide Series A_nK

Abstract

We compare the aqueous self-assembly behavior within the homologous peptide series AnK, where A is alanine, K is lysine, and n = 4, 6, 8, and 10. The aqueous peptide solubility, ϕ(s) (volume fraction), depends strongly on the number of hydrophobic alanine residues and decreases approximately as ϕ(s) ≈ 10(-n). Also the self-assembly structure depends on n. A4K is highly water-soluble and shows no relevant self-assembly. A6K, which has been extensively studied previously, forms hollow nanotubes in water. A8K and A10K self-assembly is characterized here using a combination of small- and wide-angle X-ray scattering, static and dynamic light scattering, cryo transmission electron microscopy, and circular dichroism spectroscopy. They both form similar thin rodlike aggregates with lengths on the order of 100 nm and a biaxial cross-section with dimensions of 4 nm × 8 nm. We show that different sample preparation protocols result in different lengths of the A10K rodlike aggregates. On the basis of these findings, the question of thermodynamic equilibrium of peptide self-assembly is discussed.

Arrested dynamics in a model peptide hydrogel system

“…Sample volume fractions were calculated from mass fractions and previously reported peptide densities. 24…”

“…The synthetic A 8 K and A 10 K peptides, where A is alanine and K is lysine selfassemble into weakly charged twisted ribbon aggregates, consisting of approximately N = 15 laminated b-sheets. 24,25 These aggregates are crystalline, 26 making them highly rigid, and they therefore offer an interesting model system for studying the behavior of weakly charged colloidal rods that also exhibit a short range attractive interaction due to their hydrophobicity. Tuning the electrostatic repulsion by the addition of electrolyte allows for exploring this peptide hydrogel system from a repulsive glassy state at low salt content, to a heterogeneous gel state at a higher salt content where interactions are predominantly attractive.…”

A peptide from human semenogelin I self-assembles into a pH-responsive hydrogel

“…Therefore, C(t) observed for each sample was normalized to between 1.0 and 0.0 with examples of data shown in Fig. 15 Thus, it is possible to estimate a bril length from D k . Below pH 5 and above pH 10, C(t) decays rapidly as expected for a highly mobile system.…”

“…Small amplitude dynamic tests provide information on the linear viscoelastic behavior of materials through the determination of the complex shear modulus. 15 At larger strain, the gel structure is deformed and G 0 decreases dramatically. This allows for stress relaxation and recovery of any reversible microstructural deformation during the loading process.…”

Development of New Smart Materials and Spinning Systems Inspired by Natural Silks and Their Applications

“…A4K could not self-assemble to form nanostructures. On the other hand, A8K and A10K self-assembled to form thin rod-like aggregates, possibly due to the increased hydrophobicity as more alanine amino residues were added (Cenker et al, 2014). The AnK peptides designed by Zhang et al (von Maltzahn et al, 2003) and later by Zhao et al (Qiu et al, 2009;Wang et al, 2009) were capped either at both ends or at the N-terminus.…”