Turn and helical peptide spacers: Combined distance and angular dependencies in the exciton‐coupled circular dichroism of intramolecularly interacting bis‐porphyrins

Guryanov, Ivan; Moretto, Alessandro; Campestrini, Sandro; Broxterman, Quirinus B.; Kaptein, Bernard; Peggion, Cristina; Formaggio, Fernando; Toniolo, Claudio

doi:10.1002/bip.20500

Cited by 10 publications

(14 citation statements)

References 46 publications

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“…The visible region of the spectrum indicates a positive Cotton effect for the two PZn chromophores with λ min = 423 nm and λ max = 416 nm. This observation suggests that the two (DPP)Zn chromophores are aligned in a specific rigid conformation along the superhelical axis of the bundle; in the absence of peptide, no (DPP)Zn CD signal is observed 65,66…”

Section: Resultsmentioning

confidence: 99%

Computational Design and Elaboration of a de Novo Heterotetrameric α-Helical Protein That Selectively Binds an Emissive Abiological (Porphinato)zinc Chromophore

et al. 2010

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The first example of a computationally de novo designed protein that binds an emissive abiological chromophore is presented, in which a sophisticated level of cofactor discrimination is pre-engineered. This heterotetrameric, C2-symmetric bundle, AHis:BThr, uniquely binds (5,15-di[(4-carboxymethyleneoxy)phenyl]porphinato)zinc [(DPP)Zn] via histidine coordination and complementary noncovalent interactions. The A2B2 heterotetrameric protein reflects ligand-directed elements of both positive and negative design, including hydrogen-bonds to second-shell ligands. Experimental support for the appropriate formulation of [(DPP)Zn:AHis:BThr]2 is provided by UV/visible and circular dichroism spectroscopies, size exclusion chromatography, and analytical ultracentrifugation. Time-resolved transient absorption and fluorescence spectroscopic data reveal classic excited-state singlet and triplet PZn photophysics for the AHis:BThr:(DPP)Zn protein (kfluorescence = 4 × 108 s−1; τriplet = 5 ms). The A2B2 apoprotein has immeasurably low binding affinities for related [porphinato]metal chromophores that include a (DPP)Fe(III) cofactor and the zinc metal ion hemin derivative [(PPIX)Zn], underscoring the exquisite active site binding discrimination realized in this computationally designed protein. Importantly, elements of design in the AHis:Bthr protein ensure that interactions within the tetra-α-helical bundle are such that only the heterotetramer is stable in solution; corresponding homomeric bundles present unfavorable ligand-binding environments, and thus preclude protein structural rearrangements that could lead to binding of (porphinato)iron cofactors.

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Section: Resultsmentioning

confidence: 99%

Computational Design and Elaboration of a de Novo Heterotetrameric α-Helical Protein That Selectively Binds an Emissive Abiological (Porphinato)zinc Chromophore

et al. 2010

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“…Such a strong signal is indicative of exciton coupling between well-ordered neighboring chromophores. 25,34,35 No observable signal was obtained in the absence of peptide. A temporal component has also been noted in the sample preparation that directly coincides with β-sheet formation.…”

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confidence: 98%

Self-Assembly of Highly Ordered Peptide Amphiphile Metalloporphyrin Arrays

et al. 2012

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Long fibers assembled from peptide amphiphiles capable of binding the metalloporphyrin zinc protoporphyrin IX ((PPIX)Zn) have been synthesized. Rational peptide design was employed to generate a peptide, c16-AHL(3)K(3)-CO(2)H, capable of forming a β-sheet structure that propagates into larger fibrous structures. A porphyrin-binding site, a single histidine, was engineered into the peptide sequence in order to bind (PPIX)Zn to provide photophysical functionality. The resulting system indicates control from the molecular level to the macromolecular level with a high order of porphyrin organization. UV/visible and circular dichroism spectroscopies were employed to detail molecular organization, whereas electron microscopy and atomic force microscopy aided in macromolecular characterization. Preliminary picosecond transient absorption data are also reported. Reduced hemin, (PPIX)Fe(II), was also employed to highlight the material's versatility and tunability.

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“…[Samples without porphyrin do not absorb visible light and are therefore not shown.] At ZnP doping levels (1:6 and 1:10 ZnP:PA) where the porphyrins are packed close together, we observe a splitting of the Soret band into two peaks at 420 and 430 nm (Figures 2A,B and S3A,B) in the UV/vis spectra 25 and a strong Cotton effect in the CD spectra (Figures 2D and S3D). In contrast, nanofibers with lower ZnP doping levels (e.g., 1:120 ZnP:PA) exhibit a single Soret band at 427 nm, similar to that of ZnP coordinated to His in solution (Soret band: 420 nm, Figure 2A,C).…”

Section: Resultsmentioning

confidence: 95%

Tailorable Exciton Transport in Doped Peptide–Amphiphile Assemblies

Solomon

Sykes

et al. 2017

ACS Nano

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Light-harvesting biomaterials are an attractive target in photovoltaics, photocatalysis, and artificial photosynthesis. Through peptide self-assembly, complex nanostructures can be engineered to study the role of chromophore organization during light absorption and energy transport. To this end, we demonstrate the one-dimensional transport of excitons along naturally occurring, light-harvesting, Zn-protoporphyrin IX chromophores within self-assembled peptide-amphiphile nanofibers. The internal structure of the nanofibers induces packing of the porphyrins into linear chains. We find that this peptide assembly can enable long-range exciton diffusion, yet it also induces the formation of excimers between adjacent molecules, which serve as exciton traps. Electronic coupling between neighboring porphyrin molecules is confirmed by various spectroscopic methods. The exciton diffusion process is then probed through transient photoluminescence and absorption measurements and fit to a model for one-dimensional hopping. Because excimer formation impedes exciton hopping, increasing the interchromophore spacing allows for improved diffusivity, which we control through porphyrin doping levels. We show that diffusion lengths of over 60 nm are possible at low porphyrin doping, representing an order of magnitude improvement over the highest doping fractions.

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Turn and helical peptide spacers: Combined distance and angular dependencies in the exciton‐coupled circular dichroism of intramolecularly interacting bis‐porphyrins

Cited by 10 publications

References 46 publications

Computational Design and Elaboration of a de Novo Heterotetrameric α-Helical Protein That Selectively Binds an Emissive Abiological (Porphinato)zinc Chromophore

Computational Design and Elaboration of a de Novo Heterotetrameric α-Helical Protein That Selectively Binds an Emissive Abiological (Porphinato)zinc Chromophore

Self-Assembly of Highly Ordered Peptide Amphiphile Metalloporphyrin Arrays

Tailorable Exciton Transport in Doped Peptide–Amphiphile Assemblies

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