1. Engineering Self-Assembling Peptides
to Tune the Coordination Environment
of Metalloporphyrins
Jacob Kronenberg, Illinois Mathematics and Science Academy
Advisor: Dr. H. Christopher Fry, Argonne National Laboratory
2. Background: c16-AHL3K3-CO2H
A self-assembling metalloporphyrin-binding peptide amphiphiles, developed by
Fry et al. (2012). It uses a monohistidine binding site to coordinate hemes.
4. Focusing Question
How can we design a peptide to control the
coordination environment of a bound porphyrin
and thus tune its electrochemical or catalytic
properties?
6. β-Sheet Formation
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CircularDichroism(deg·cm^2/mmol)
Wavelength (nm)
Circular Dichroism Spectra
c16-AHL3K3-CO2H
c16-H2L3K3-CO2H
c16-MHL3K3-CO2H
Circular dichroism spectra of the three peptides demonstrate β-sheet
formation. All three demonstrate the peaks characteristic of β-sheets, with the
differences in strength believed to be due to variations in bundling.
7. Spectra of Porphyrin-Peptide
Complexes
Fig. 2: Sample Ultraviolet-Visible spectra of the three peptides, each bound to
oxidized hemin. The inset shows the Q-band peaks with greater detail.
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Absorbance
Wavelength (nm)
UV-Vis Spectra
8. Electron Paramagnetic
Resonance
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Signal
Magnetic Field (G)
Electron Paramagnetic Resonance Spectra
c16-AHL3K3-CO2H
c16-H2L3K3-CO2H
c16-MHL3K3-CO2H
High Spin
Low Spin
High Spin
These EPR spectra show that c16-MHL3K3-CO2H shows a characteristic
high-spin pattern, c16-H2L3K3-CO2H shows a low-spin pattern, and c16-
AHL3K3-CO2H exhibits a weaker, but still low-spin pattern.
9. Atomic Force Microscopy
Bundle Network Structure Single Bundle Structure
Photo credit to Dr. Seth Darling and Dr. Adina Luican-M
10. O2 Binding
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Absorbance
Wavelength (nm)
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Fe(III)
Fe(II)
Fe(II) + O2
Fe(II) + N2
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c16-AHL3K3-CO2H c16-H2L3K3-CO2H
The UV/vis spectra for the His and His-His peptides show that chemical
oxidation and reduction change the electron environment and that they can bind
O2.
11. Conclusions
All three peptides, c16-AHL3K3-CO2H, c16-H2L3K3-
CO2H, and c16-MHL3K3-CO2H self-assemble into
high-aspect-ratio fibers.
The His and His-His coordination environments
yield low-spin hemes.
The His-Met environment yields high-spin hemes.
Each peptide does give a unique coordination
environment
Results suggest that c16-H2L3K3-CO2H (his-his
environment) can reversibly bind O2.
12. Discussion
The bishistidine peptide has similar properties to
other natural proteins, including coordination
environment, low-spin state, and reversible O2
binding.
The other two peptides have new properties which
require further testing.
These materials could have applications as
chemotherapeutic agents.
Possible further research includes testing the
interactions of the peptides with cells and further
examining the coordination environments,
particularly with the monohistidine peptide.
13. Selected Bibliography
Cochran, F., Wu, S., Wang, W., Nanda, V., Saven, J., Therien,
M., & DeGrado, W. (2005). Computational de novo
design and characterization of a four-helix bundle protein
that selectively binds a nonbiological cofactor. J. Am.
Chem. Soc., 127, 1346- 1347.
Fry, H., Garcia, J., Medina, M., Ricoy, U., Gosztola, D.,
Nikiforov, M., Palmer, L., & Stupp, S. (2012). Self-
assembly of highly ordered peptide amphiphile
metalloporphyrin arrays. Journal of the American Chemical
Society, 134(26), 14646-9.
Hartgering, J.D., Beniash, E., & Stupp, S. I. (2001). Self
assembly and mineralization of peptide-amphiphile
nanofibers. Science, 294, 1684-1687.
More sources available upon request.
14. Acknowledgments
I would like to thank Dr. Christopher Fry for his help and
guidance with this project; Dr. Tijana Rajh, Dr. Adina
Luican-Mayer, and Dr. Seth Darling for their assistance
with the use of instrumentation; the Argonne National
Laboratory’s Center for Nanoscale Materials, for
allowing use of their facilities; and the SIR team of
IMSA, for making this program possible.
