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Title: Molecular Dynamics Studies of Atomistically Determined Fibrillar Assemblies: Comparison of the Rippled β-Sheet, Pleated β-Sheet, and Herringbone Structures
Award ID(s):
2311117
PAR ID:
10518352
Author(s) / Creator(s):
; ; ; ;
Publisher / Repository:
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
Date Published:
Journal Name:
The Journal of Physical Chemistry Letters
Volume:
15
Issue:
17
ISSN:
1948-7185
Page Range / eLocation ID:
4568 to 4574
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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  1. Peptide self-assembly, wherein molecule A associates with other A molecules to form fibrillar β-sheet structures, is common in nature and widely used to fabricate synthetic biomaterials. Selective coassembly of peptide pairs A and B with complementary partial charges is gaining interest due to its potential for expanding the form and function of biomaterials that can be realized. It has been hypothesized that charge-complementary peptides organize into alternating ABAB-type arrangements within assembled β-sheets, but no direct molecular-level evidence exists to support this interpretation. We report a computational and experimental approach to characterize molecular-level organization of the established peptide pair, CATCH. Discontinuous molecular dynamics simulations predict that CATCH(+) and CATCH(−) peptides coassemble but do not self-assemble. Two-layer β-sheet amyloid structures predominate, but off-pathway β-barrel oligomers are also predicted. At low concentration, transmission electron microscopy and dynamic light scattering identified nonfibrillar ∼20-nm oligomers, while at high concentrations elongated fibers predominated. Thioflavin T fluorimetry estimates rapid and near-stoichiometric coassembly of CATCH(+) and CATCH(−) at concentrations ≥100 μM. Natural abundance13C NMR and isotope-edited Fourier transform infrared spectroscopy indicate that CATCH(+) and CATCH(−) coassemble into two-component nanofibers instead of self-sorting. However,13C–13C dipolar recoupling solid-state NMR measurements also identify nonnegligible AA and BB interactions among a majority of AB pairs. Collectively, these results demonstrate that strictly alternating arrangements of β-strands predominate in coassembled CATCH structures, but deviations from perfect alternation occur. Off-pathway β-barrel oligomers are also suggested to occur in coassembled β-strand peptide systems. 
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  2. null (Ed.)