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Formation of Annular Protofibrillar Assembly by Cysteine Tripeptide: Unraveling the Interactions with NMR, FTIR, and Molecular Dynamics

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Title Formation of Annular Protofibrillar Assembly by Cysteine Tripeptide: Unraveling the Interactions with NMR, FTIR, and Molecular Dynamics
 
Creator Banerji, Biswadip
Chatterjee, Moumita
Pal, Uttam
Maiti, Nakul Chandra
 
Subject Chemistry
Structural Biology & Bioinformatics
 
Description Both hydrogen-bonding and hydrophobic interactions play a significant role in molecular assembly,including self-assembly of proteins and peptides. In this study,
we report the formation of annular protofibrillar structure (diameter ∼500 nm) made of a newly synthesized s-benzylprotected cysteine tripeptide, which was primarily stabilized by hydrogen-bonding and hydrophobic interactions. Atomic force microscopy and field emission scanning electron microscopy analyses found small oligomers (diameter ∼60 nm) to bigger annular (outer diameter ∼300 nm; inner diameter, 100 nm) and protofibrillar structures after 1−2 days of incubation.
Rotating-frame Overhauser spectroscopic (ROESY) analysis
revealed the presence of several nonbonded proton−proton
interactions among the residues, such as amide protons with methylene group, aromatic protons with tertiary butyl group, and methylene protons with tertiary butyl group. These added significant stability to bring the peptides closer to form a well-ordered assembled structure. Hydrogen−deuterium exchange NMR measurement further suggested that two individual amide protons among the three amide groups were strongly engaged with the adjacent tripeptide via H-bond interaction. However, the
remaining amide proton was found to be exposed to solvent and remained noninteracting with other tripeptide molecules. In addition to chemical shift values, a significant change in amide bond vibrations of the tripeptide was found due to the formation of the self-assembled structure. The amide I mode of vibrations involving two amide linkages appeared at 1641 and 1695 cm−1 in the solid state. However, in the assembled state, the stretching band at 1695 cm−1 became broad and slightly shifted to ∼1689 cm−1. On the contrary, the band at 1641 cm−1 shifted to 1659 cm−1 and indicated that the −CO bond associated with this vibration became stronger in the assembled state. These changes in Fourier transform infrared spectroscopy frequency clearly
indicated changes in the amide backbone conformation and the associated hydrogen-bonding pattern due to the formation of the assembled structure. In addition to hydrogen bonding, molecular dynamics simulation indicated that the number of π−π interactions also increased with increasing number of tripeptides participated in the self-assembly process. Combined results envisaged a cross β-sheet assembly unit consisting of four intermolecular hydrogen bonds. Such noncovalent peptide assemblies
glued by hydrogen-bonding and other weak forces may be useful in developing nanocapsule and related materials.
 
Publisher American Chemical Society
 
Date 2017-07-06
 
Type Article
PeerReviewed
 
Format application/pdf
 
Identifier http://www.eprints.iicb.res.in/2713/1/The_Journal_of_Physical_Chemistry_B.pdf
Banerji, Biswadip and Chatterjee, Moumita and Pal, Uttam and Maiti, Nakul Chandra (2017) Formation of Annular Protofibrillar Assembly by Cysteine Tripeptide: Unraveling the Interactions with NMR, FTIR, and Molecular Dynamics. The Journal of Physical Chemistry B, 121 (26). pp. 6367-6379.
 
Relation http://dx.doi.org/10.1021/acs.jpcb.7b04373
http://www.eprints.iicb.res.in/2713/