Structures and Functions of Peptide-metal Co-assemblies Open Access

Abstract

Amyloid-beta (Aβ) peptide is a hallmark of Alzheimer’s disease in forming toxic aggregates or fibers. A hydrophobic sequence of Aβ, LVFFA, is a nucleating core sequence for forming assemblies. Short peptides with this core sequence assemble well-ordered supramolecules with cross-beta sheet secondary structures in nano- fibers, ribbons, or tubes morphologies. Incorporating transition metal ions allows for development of functions of the well-ordered peptide assemblies. In the nucleation steps of peptide assembly, in which metastable structures exist, adding transition metal ions template the assembly of peptide-metal co-assemblies. H-HHQALVFFA-NH2, (K16A), and H-HHQALFFAL-NH2, (K16AL), sequences with the N-terminal histidine residues were utilized for peptide-metal co-assemblies. We found that peptide assemblies with and without metal ions have morphological, optical, and structural differences. Through structural studies, K16A-Cu(II) co-assemblies’ detailed information such as assembly structures and copper complex structures were characterized. Electrochemical properties and applications were also tested, and high reduction potentials (~700 mV) were measured. To modify surface and morphology of the K16A-Cu co-assemblies, K16AL with C-terminal leucine was synthesized. Compared to K16A, K16AL assembly series have different morphologies and because of high hydrophobicity, K16AL self- and co-assemblies with metals shows faster rates of forming assemblies in aqueous solution, by CD and TEM analyses. We also demonstrate that co-assemblies of the peptides and lead(II) ions also form well-ordered structures. The assemblies were tested in DMF solvent systems for applications requiring organic solvents. Among the K16A self- and co-assemblies with metals in DMF solvent systems, K16A-PbI2 co-assemblies in DMF with 20% water shows well-organized fiber structures and distinct UV/Vis absorption range from lead ion arrays. As a proof-of-concept of K16A and K16AL can remove heavy metals from contaminated water. Copper ions were well isolated by both K16A and K16AL, while high concentrations of lead ions were measured after the treatments. Construction of a model for nanotubes of a peptide assembly with Cryo-EM was performed to get detailed structures and isotope-edited infrared (IE-IR) study identified defects in strand conformational fidelity in beta-sheets.

Table of Contents

Chapter 1.

Introduction: Emerging functions of peptide self-assemblies and control of its structures

 

1.1 Self-assemblies in biology

1.2 Structures of peptide self-assemblies

1.3 Functions and applications of peptide self-assemblies

1.4 Control of peptide assembly structures

1.5 Conclusion

1.6 References

 

Chapter 2.

Structural studies of peptide self-assemblies with cryo-EM and IE-IR

 

2.1-1 Introduction - cryo-EM for reconstruction of E22L peptide assembly

2.1-2 Results and discussion

2.1-2.1 Optimization of sample vitrification and a model of E22L nanotubes

2.2-1 Introduction - IR studies of peptide assemblies for detection of defects.

2.2-2 Results and discussion

2.2-2.1 IE-IRs of E22L and IR-simulation with transition dipole coupling

2.3 Conclusion

2.4 Materials and methods

2.5 References

 

Chapter 3.

Copper arrays in peptide-metal co-assemblies

 

3.1 Introduction

3.2 Results and discussion

3.2.1 kinetics and morphologies of K16A-Cu(II)/Cu(I) co-assemblies

3.2.2 Structure studies of the K16A-Cu(II) co-assembly

3.2.3 Catalytic reactivities of K16A-Cu(II)/Cu(I) co-assemblies

3.2.4 K16AL and K16AL-Cu(II)/Cu(I) Co-assemblies and its catalytic reactivities

3.3 Conclusion

3.4 Materials and methods

3.5 References

 

Chapter 4.

New peptide-metal co-assemblies with lead(II)

 

4.1 Introduction

4.2 Results and discussion

4.2.1 K16A-metal co-assemblies in DMF solvent systems

4.2.2 K16A-Pb(II) co-assemblies in aqueous solvent

4.2.3 Isolating heavy metals using peptide-metal co-assemblies

4.3 Conclusion

4.4 Future works

4.5 Materials and methods

4.6 References

About this Dissertation

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School	Laney Graduate School
Department	Chemistry
Degree	Ph.D.
Submission	Dissertation
Language	English
Research Field	Chemistry, Polymer Chemistry, Biochemistry Chemistry, Molecular
Keyword	Peptide assemblies Peptide-metal co-assemblies Peptide
Committee Chair / Thesis Advisor	David Lynn, Emory University
Committee Members	Vincent Conticello, Emory University Laura Finzi, Emory University

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