Self Assembly of Coiled-Coil Peptide-Porphyrin Complexes

Department of Biology, Haverford College, Haverford, Pennsylvania 19041, USA.
Biomacromolecules (Impact Factor: 5.79). 05/2009; 10(6):1454-9. DOI: 10.1021/bm9000553
Source: PubMed

ABSTRACT We are interested in the controlled assembly of photoelectronic materials using peptides as scaffolds and porphyrins as the conducting material. We describe the integration of a peptide-based polymer strategy with the ability of designed basic peptides to bind anionic porphyrins in order to create regulated photoelectronically active biomaterials. We have described our peptide system in earlier work, which demonstrates the ability of a peptide to form filamentous materials made up of self-assembling coiled-coil structures. We have modified this peptide system to include lysine residues appropriately positioned to specifically bind meso-tetrakis(4-sulfonatophenyl)porphine (TPPS(4)), a porphyrin that contains four negatively charged sulfonate groups at neutral pH. We measure the binding of TPPS(4) to our peptide using UV--visible and fluorescence spectroscopies to follow the porphyrin signature. We determine the concomitant acquisition of helical secondary structure in the peptide upon TPPS(4) binding using circular dichroism spectropolarimetry. This binding fosters polymerization of the peptide, as shown by absorbance extinction effects in the peptide CD spectra. The morphologies of the peptide/porphyrin complexes, as imaged by atomic force microscopy, are consistent with the coiled-coil polymers that we had characterized earlier, except that the heights are slightly higher, consistent with porphyrin binding. Evidence for exciton coupling in the copolymers is shown by red-shifting in the UV--visible data, however, the coupling is weak based on a lack of fluorescence quenching in fluorescence experiments.

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    ABSTRACT: This study aims to extend a structural and biophysical understanding of a coiled-coil based peptide model system that serves as a scaffold for the anionic porphyrin, TPPS4. This is part of an ongoing biomaterials effort to create photoelectronically active mesoscale fibrils for surface deposition and characterization of conductivity properties. The goals are twofold: (1) to explore optimal basic side-chain moieties for tight binding to TPPS4; and (2) to test the binding of various metallated TPPS4 derivatives to our peptide model system. The latter goal is to control the electronic and redox properties of the fibrillar biomaterials. A soluble version of the peptide biomaterial was used in order to probe binding and to extract thermodynamically rigorous equilibrium binding constants. UV-visible spectroscopy and circular dichroism spectropolarimtery are used to measure the effects of binding on the Soret band of the porphyrin and the helical signal of the peptide, respectively. For the first study, it was found that lysine, ornithine, and arginine are equally robust at engaging TPPS4 with low micromolar binding affinity. In the case of the metallated porphyrins, submicromolar binding affinity was observed for Cu(II), Ni(II), and Pd(II). The ability of these metallated porphyrins to bind with high affinity is dependent largely on structural perturbations of the porphyrin molecule, rather than on induced electronic effects.
    Biomacromolecules 11/2014; 15(12). DOI:10.1021/bm5013426 · 5.79 Impact Factor
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    ABSTRACT: Long-range structural order and alignment over different scales are of key importance for the regulation of structure and functionality in biology. However, it remains a great challenge to engineer and assemble such complex functional synthetic systems with order over different length scales from simple biologically relevant molecules, such as peptides and porphyrins. Herein we describe the successful introduction of hierarchical long-range order in dipeptide-adjusted porphyrin self-assembly by a thermodynamically driven self-orienting assembly pathway associated with multiple weak interactions. The long-range order and alignment of fiber bundles induced new properties, including anisotropic birefringence, a large Stokes shift, amplified chirality, and excellent photostability as well as sustainable photocatalytic activity. We also demonstrate that the aligned fiber bundles are able to induce the epitaxially oriented growth of Pt nanowires in a photocatalytic reaction.
    Angewandte Chemie International Edition 11/2014; 54(2). DOI:10.1002/anie.201409149 · 11.34 Impact Factor
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    ABSTRACT: The J-aggregation of meso-tetra (4-sulfonatophenyl) porphine (TPPS4) on a plant-esterase-functionalized surface in a 1:1 v/v mixture of 0.05 M HCl/ethanol (pH~1.38) was analyzed in real time using a quartz crystal microbalance with dissipation monitoring (QCM-D). Simultaneous changes in frequency (Δf) and energy dissipation (ΔD) correlated well with mass and structural changes during the sequential phases of slow nucleation, rapid aggregation and equilibration in J-aggregation. The time-dependent mass adsorption could be quantitatively analyzed with a model, which integrated two simple equations obtained when the surface concentration of TPPS4 (ГTPPS4) was below and above the critical aggregation surface concentration (casc). This study provides a new view for the protein-induced J-aggregation process, which may be helpful to understand the interactions of self-assembled nanostructures with biomolecules.
    Langmuir 07/2014; 30(33). DOI:10.1021/la501986e · 4.38 Impact Factor

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