Nanometer to Millimeter Scale Peptide-Porphyrin Materials

Abstract

AQ-Pal14 is a 30-residue polypeptide that was designed to form an α-helical coiled coil which contains a metal-binding 4-pyridylalanine residue on its solvent-exposed surface. However, characterization of this peptide shows that it exists as a three-stranded coiled coil, and not a twostranded one as predicted from its design. Reaction with cobalt(III) protoporphyrin IX (Co-PPIX) produces a six-coordinate Co-PPIX(AQ-Pal14) 2 species which creates two coiled-coil oligomerization domains coordinated to opposite faces of the porphyrin ring. It is found that this species undergoes a buffer-dependent self-assembly process: nanometer-scale globular materials were formed when these components were reacted in unbuffered H 2 O, while millimeter-scale rodlike materials were prepared when the reaction was performed in phosphate buffer (20 mM, pH 7). It is suggested that assembly of the globular material is dictated by the conformational properties of the coiled-coil forming AQ-Pal14 peptide, whereas that of the rod-like material involves interactions between Co-PPIX and phosphate ion.

Metal-binding properties and structural characterization of a self-assembled coiled coil: Formation of a polynuclear Cd–thiolate cluster

“…It is usually expected that the respective placement of isoleucine and leucine residues at the first and the fourth heptad positions of a coiled coil sequence promotes the formation of two-stranded coiled coils [56]. However, recent studies on the closely related AQ-Pal14 [47] and CC-pIL [57] peptides showed that they both unexpectedly formed a three-stranded coiled coil, making us anticipate the analogous behavior of the AQ-C16C19 peptide.…”

“…Buffers contained 0-1000 mM KCl to maintain the desired ionic strength. The instrumentation setup employed for the analysis of eluates is described earlier [47]. The dn/dc value for the metal-free AQ-C16C19 in the phosphate buffer at pH 7 was obtained in the batch analysis of a series of dilutions of the peptide using the Optilab rEX instrument.…”

“…The apparent weight average molar mass M w was calculated using the Zimm fit method with a first-degree polynomial as implemented in the Astra software. Details on light-scattering analysis can be found in the yearly publications [47,49].…”

Solvent‐Tuned Self‐Assembled Nanostructures of Chiral l/d‐Phenylalanine Derivatives of Protoporphyrin IX

“…In nature, elegant arrangements of peptide–porphyrin conjugates are essential in conducting biological processes . This has inspired researchers worldwide to investigate the self‐assembly and supramolecular structures of porphyrin–peptide conjugates mimicking the structure and role of natural porphyrin . In this work, we explore the development and use of l ‐ and d ‐phenylalanine‐substituted protoporphyrin IX derivatives 1 and 2 , respectively, for the solvophobic‐controlled assembly of nanostructures (Figure ).…”

Supramolecular Chemistry of Protoporphyrin IX and Its Derivatives

“…[24] They showed that a polypeptide bearing 4pyridylalanine self-assembles into globular and rod-like morphologies through metal-binding interactions with Co-PP-IX (13) (Figure 2). [24] They showed that a polypeptide bearing 4pyridylalanine self-assembles into globular and rod-like morphologies through metal-binding interactions with Co-PP-IX (13) (Figure 2).…”