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Issue 12, 2019
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Microenvironment control of porphyrin binding, organization, and function in peptide nanofiber assemblies

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Abstract

To take peptide materials from predominantly structural to functional assemblies, variations in cofactor binding sites must be engineered and controlled. Here, we have employed the peptide sequence c16-AHX3K3-CO2H where X3 represents the aliphatic structural component of the peptide design that dictates β-sheet formation and upon self-assembly yields a change in the overall microenvironment surrounding the Zn protoporphyrin IX ((PPIX)Zn) binding site. All peptides studied yield β-sheet rich nanofibers highlighting the materials’ resiliency to amino acid substitution. We highlight that the (PPIX)Zn binding constants correlate strongly with amino acid side chain volume, where X = L or I yields the lowest dissociation constant values (KD). The resulting microenvironment highlights the materials’ ability to control interchromophore electronic interactions such that slip-stacked cofacial arrangements are observed via exciton splitting in UV/visible and circular dichroism spectroscopy. Steady state and time-resolved photoluminescence suggests that greater interchromophore packing yields larger excimer populations and corresponding longer excimer association lifetimes (τA) which directly translates to shorter exciton diffusion lengths. In comparison to synthetic porphyrin molecular assemblies, this work demonstrates the ability to employ the peptide assembly to modulate the degree of cofactor arrangement, extent of excimer formation, and the exciton hopping rates all while in a platform amenable for producing polymer-like materials.

Graphical abstract: Microenvironment control of porphyrin binding, organization, and function in peptide nanofiber assemblies

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Publication details

The article was received on 26 Nov 2018, accepted on 22 Feb 2019 and first published on 07 Mar 2019


Article type: Paper
DOI: 10.1039/C8NR09556F
Nanoscale, 2019,11, 5412-5421

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    Microenvironment control of porphyrin binding, organization, and function in peptide nanofiber assemblies

    L. A. Solomon, A. R. Wood, M. E. Sykes, B. T. Diroll, G. P. Wiederrecht, R. D. Schaller and H. C. Fry, Nanoscale, 2019, 11, 5412
    DOI: 10.1039/C8NR09556F

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