Self-Organization of porphyrin-peptide units by metal-mediated peptide assembly

Abstract

O polipeptídeo H21(30-mer) forma dímeros "coiled-coil" que apresentam dois resíduos histidínicos expostos ao solvente nos lados opostos de sua superfície. Este peptídeo reage com a protoporfirina IX de cobalto, Co(ppIX), para produzir [Co(ppIX){(H21(30-mer)} 2 ], como determinado por espectroscopia UV-Vis. Esta ligação bi-axial disponibiliza um potencial domínio de oligomerização "coiled-coil" em cada face do anel porfirínico de cobalto. Dicroísmo circular e cromatografia líquida de exclusão de alto desempenho forneceram evidências da auto-organização destas unidades porfirina-peptídeo em solução. A evaporação da solução porfirina-peptídeo em uma superfície sólida resultou na formação de longos materiais cilíndricos com milímetros de comprimento e micrometros de diâmetro. A presença do complexo Co(ppIX) nestes materiais foi confirmada por microscopia Raman. Estes materiais, entretanto, foram formados somente com o tampão fosfato, e não com tampões orgânicos ou água pura, indicando que sua formação deve envolver um processo mais complicado do que originalmente antecipado.The polypeptide H21(30-mer) folds into a two-stranded coiled-coil in which two solventexposed histidine residues reside on opposite sides of its surface. This peptide was allowed to react with cobalt(III) protoporphyrin IX, Co(ppIX), to produce [Co(ppIX){(H21(30-mer)} 2 ], as determined by UV-Vis spectroscopy. This bis-axial ligation thus positions a potential coiledcoil oligomerization domain onto each face of the cobalt porphyrin ring. Circular dichroism spectroscopy and high performance size exclusion chromatography provide evidence for the solution-phase self-assembly of these porphyrin-peptide units. Evaporation of the porphyrinpeptide solution on a solid support results in the formation of long rod-like materials having millimeter-scale lengths and micron-scale diameters. The presence of Co(ppIX) in these materials was confirmed by Raman microscopy. However, they were formed only from phosphate buffer, and not from organic buffers or pure water, indicating that their formation might involve a more complicated process than originally anticipated.Keywords: cobalt protoporphyrin IX, peptides, fibers, self-assembly IntroductionMolecular self-assembly has proven to be a valuable approach towards the bottom-up design of synthetic materials. [1][2][3][4][5] Much inspiration for this work comes from biological precedents in which optimal combinations of hydrogen-bond, electrostatic, and hydrophobic interactions are used to assemble polypeptides and nucleic acids into robust structural motifs. 2,4 To further expand the tools for preparing such materials, continuing efforts are being directed towards gaining a better understanding of how various combination of non-covalent interactions can be used to prepare self-assembled materials having predictable and well-defined morphologies. 6,7 Inspired by workers in the field of supramolecular coordination chemistry, we 8-12 and others [13][14][15][16] have been exploring a new route for preparing self-assem...

Nanometer to Millimeter Scale Peptide-Porphyrin Materials

“…Whereas these materials can be seen by the naked eye, closer examination by SEM reveals that they are hierarchical in nature, existing as bundles of smaller rods each having diameters of < 2 microns. These results are thus similar to our preliminary report of rod-like materials formed from the reaction of Co-PPIX with a related histidine-containing polypeptide which is known to form two-stranded coiled-coils 53. As this type of structure can be produced from peptides having different oligomerization motifs, it now appears that their formation is not driven by the self-assembly properties of the peptide.…”

“…These results are thus similar to our preliminary report of rod-like materials formed from the reaction of Co-PPIX with a related histidine-containing polypeptide which is known to form twostranded coiled coils. 53 As this type of structure can be produced from peptides having different oligomerization motifs, it now appears that their formation is not driven by the self-assembly properties of the peptide.…”

De Novo Design of Xeno‐Metallo Coiled Coils

“…Whilst most metallo‐porphyrins contain Fe II/III , there are examples with alternative metals. Four‐stranded CCs were also found to bind Zn II ‐porphyrins in the interior of the scaffold, and one example of a Co II ‐porphyrin sees it binding to the exterior of the assembly. An advancement in the incorporation of porphyrins into peptide scaffolds saw Fairman and co‐workers create a system that allows for different metallated porphyrins to be incorporated by taking advantage of non‐covalent binding between the porphyrin pendant groups and amino acid functional groups .…”

“…[19] The designed transmembrane CC scaffold was again used to position the redox-active cofactors sufficiently closef or electron transfer. [19] Whilst most metallo-porphyrins contain Fe II/III ,t here are examplesw ith alternative metals.F our-stranded CCs were also found to bind Zn II -porphyrins [20] in the interioro ft he scaffold, and one example of aC o II -porphyrin [21] sees it binding to the exterioro ft he assembly.A na dvancement in the incorporation of porphyrins into peptides caffolds saw Fairman and co-workers create as ystem that allows for different metallated porphyrins to be incorporated by taking advantage of non-covalent binding between the porphyrin pendant groups and amino acid functional groups. [22] An anionic porphyrin, mesotetrakis(4-sulfonatophenyl)porphine (TPPS 4 ), was introduced in this way as the conducting material along the CC, through favorable electrostatic interactions between Lyss ide chains and three of the four sulfonate groups on the porphyrin.…”

Peptide-Tetrapyrrole Supramolecular Self-Assemblies: State of the Art

“…Complex 28a self-assembled into rod-like architectures with mm-scale lengths and μm-scale diameters in phosphate buffer [ 80 ]. Carvalho et al highlighted the importance of the solvent and of the peptide–porphyrin synergy in the process, by showing that rods are not formed from the assembly of either component alone, nor from peptide–porphyrin mixtures dissolved in organic buffers or pure water.…”