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Polymorphism in self-assembly of peptide-based ?-hairpin contributes to network morphology and hydrogel mechanical rigidity.

ABSTRACT: Hydrogels are proving to be an excellent class of materials for biomedical applications. The molecular self-assembly of designed MAX1 ?-hairpin peptides into fibrillar networks has emerged as a novel route to form responsive hydrogels. Herein, computational modeling techniques are used to investigate the relative arrangements of individual hairpins within the fibrils that constitute the gel. The modeling provides insight into the morphology of the fibril network, which defines the gel's mechanical properties. Our study suggests polymorphic arrangements of the hairpins within the fibrils; however, the relative populations and the relative conformational energies of the polymorphic arrangements show a preference toward an arrangement of hairpins where their turn regions are not capable of forming intermolecular interaction. Repulsive intramolecular electrostatic interactions appear to dictate the formation of fibrils with shorter, rather than longer, persistent lengths. These repulsive intramolecular interactions also disfavor the formation of fibril entanglements. Taken together, the modeling predicts that MAX1 forms a network containing a large number of branch points, a network morphology supported by the formation of short fibril segments. We posit that, under static conditions, the preferred branched structures of the MAX1 peptide assembly result in a cross-linked hydrogel organization. At the same time, the shear stress leads to short fibrillar structures, thus fluidic hydrogel states.

SUBMITTER: Miller Y

PROVIDER: S-EPMC4298354 | biostudies-other | 2015 Jan

REPOSITORIES: biostudies-other

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Polymorphism in self-assembly of peptide-based β-hairpin contributes to network morphology and hydrogel mechanical rigidity.

Miller Yifat Y Ma Buyong B Nussinov Ruth R

The journal of physical chemistry. B 20141231 2

Hydrogels are proving to be an excellent class of materials for biomedical applications. The molecular self-assembly of designed MAX1 β-hairpin peptides into fibrillar networks has emerged as a novel route to form responsive hydrogels. Herein, computational modeling techniques are used to investigate the relative arrangements of individual hairpins within the fibrils that constitute the gel. The modeling provides insight into the morphology of the fibril network, which defines the gel's mechanic ...[more]

PMID: 25545881

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Project description:The characterization of self-assembling molecules presents significant experimental challenges, especially when associated with phase separation or precipitation. Transparent window infrared (IR) spectroscopy leverages site-specific probes that absorb in the "transparent window" region of the biomolecular IR spectrum. Carbon-deuterium (C-D) bonds are especially compelling transparent window probes since they are non-perturbative, can be readily introduced site selectively into peptides and proteins, and their stretch frequencies are sensitive to changes in the local molecular environment. Importantly, IR spectroscopy can be applied to a wide range of molecular samples regardless of solubility or physical state, making it an ideal technique for addressing the solubility challenges presented by self-assembling molecules. Here, we present the first continuous observation of transparent window probes following stopped-flow initiation. To demonstrate utility in a self-assembling system, we selected the MAX1 peptide hydrogel, a biocompatible material that has significant promise for use in drug delivery and medical applications. C-D labeled valine was synthetically introduced into five distinct positions of the twenty-residue MAX1 β-hairpin peptide. Consistent with current structural models, steady-state IR absorption frequencies and linewidths of C-D bonds at all labeled positions indicate that these side chains occupy a hydrophobic region of the hydrogel and that the motion of side chains located in the middle of the hairpin is more restricted than those located on the hairpin ends. Following a rapid change in ionic strength to initiate self-assembly, the peptide absorption spectra were monitored as function of time, allowing determination of site-specific time constants. We find that within the experimental resolution, MAX1 self-assembly occurs as a cooperative process. These studies suggest that stopped-flow transparent window FTIR can be extended to other time-resolved applications, such as protein folding and enzyme kinetics.

Dataset Information

Polymorphism in self-assembly of peptide-based ?-hairpin contributes to network morphology and hydrogel mechanical rigidity.

Publications

Polymorphism in self-assembly of peptide-based β-hairpin contributes to network morphology and hydrogel mechanical rigidity.

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