β-Sheet to Random Coil Transition in Self-Assembling Peptide Scaffolds Promotes Proteolytic Degradation (original) (raw)
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Effect of functionalization on the self-assembling propensity of β-sheet forming peptides
Soft Matter, 2009
The mechanism underlying self-assembly of short peptides has not been fully understood despite the fact that a few decades have passed since their serendipitous discovery. RADA16-I (AcN-RADARADARADARADA-CONH 2 ), representative of a class of self-assembling peptides with alternate hydrophobic and hydrophilic residues, self-assembles into b-sheet bilayer filaments. Though a sliding diffusion model for this class of peptides has been developed in previous works, this theory need further improvements, supported by experimental investigations, to explain how RADA16-I functionalization with biological active motifs, added at the C-terminus of the self-assembling core sequence, may influence the self-assembling tendency of new functionalized peptides (FPs). Since FPs recently became a promising class of biomaterials for cell biology and tissue engineering, a better understanding of the phenomenon is necessary to design new scaffolds for nanotechnology applications. In this work we investigated via atomic force microscopy and Raman spectroscopy the assembly of three RADA16-I FPs that have different hydrophobic/hydrophilic profiles and charge distributions. We performed molecular dynamics simulations to provide further insights into the experimental results: functionalizing self-assembling peptides can strongly influence or prevent molecular assembly into nanofibers. We also found certain vibrational molecular modes in Raman spectroscopy to be useful indicators for elucidating the assembly propensity of FPs. Preliminary FP designing strategies should therefore include functional motif sequences with balanced hydrophobicity profiles avoiding hydrophobic patches, causing fast hydrophobic collapses of the FP molecules, or very hydrophilic motifs capable of destabilizing the RADA16-I double layered b-sheet structure. † Electronic supplementary information (ESI) available: Hydrophobicity profiles using the Kyte-Doolittle scale; starting structure of each peptide before the MD simulations; tapping mode image of RADA16-I-ALK at 1% (w/v); and AFM image of monolayer formed by RADA16-I-SDE over mica surface. See
Peptide Self-Assembly and Its Effect on Hydrogel Properties and Plasma Protein Interaction
In order to elucidate design principals for the development of novel materials that are both biofunctional and bioresponsive, we investigate a class of oligopeptides that can ionically self-assemble in salt solutions to form matrices. Plasma protein and biomaterial interaction mechanisms will be investigated for designing improved biomaterials. The goal of this study is to understand peptide self-assembly, hydrogel properties and plasma protein interaction. RADA 4 (Type I), [COCH 3 ]-RADARADARADARADA-[CONH 2 ], has been shown to form antiparellel βsheets, which further self-assemble into nanofibers that then develop into a viscoelastic 3D matrix in aqueous solution. Specifically, amino acids of various physicochemical properties will be added to the self-assembling peptide domain to determine their effect on nanofiber properties and plasma protein interactions, for understanding the host response to biomaterials. Peptide nanofibers will be characterized so as to determine their charge and hydration state. The ultimate goal of this research program is to correlate material properties to protein interactions and activation. The knowledge gained through this project is of fundamental importance to the development of peptide based materials for a plethora of cardiovascular nanomedicine applications.
2018
Arginine-alanine-aspartic acid-alanine) 4 ((RADA) 4) nanoscaffolds are excellent candidates for use as peptide delivery vehicles: they are relatively easy to synthesize with custom bio-functionality, and assemble in situ to allow a focal point of release. This enables (RADA) 4 to be utilized in multiple release strategies by embedding a variety of bioactive molecules in an all-in-one "construct". One novel strategy focuses on the local, on-demand release of peptides triggered via proteolysis of tethered peptide sequences. However, the spatial-temporal morphology of self-assembling nanoscaffolds may greatly influence the ability of enzymes to both diffuse into as well as actively cleave substrates. Fine structure and its impact on the overall effect on peptide release is poorly understood. In addition, fractal networks observed in nanoscaffolds are linked to the fractal nature of diffusion in these systems. Therefore, matrix morphology and fractal dimension of virgin (RADA) 4 and mixtures of (RADA) 4 and matrix metalloproteinase 2 (MMP-2) cleavable substrate modified (RADA) 4 were characterized over time. Sites of high (glycine-proline-glutamine-glycine+isoleucine-alanine-serine-glutamine (GPQG+IASQ), CP1) and low (glycine-proline-glutamine-glycine+proline-alanine-glycine-glutamine (GPQG+PAGQ), CP2) cleavage activity were chosen. Fine structure was visualized using transmission electron microscopy. After 2 h of incubation, nanofiber networks showed an established fractal nature; however, nanofibers continued to bundle in all cases as incubation times increased. It was observed that despite extensive nanofiber bundling after 24 h of incubation time, the CP1 and CP2 nanoscaffolds were susceptible to MMP-2 cleavage. The properties of these engineered nanoscaffolds characterized herein illustrate that they are an excellent candidate as an enzymatically initiated peptide delivery platform.
Toward the Development of Peptide Nanofilaments and Nanoropes As Smart Materials
Proceedings of the …, 2005
Protein design studies using coiled coils have illustrated the potential of engineering simple peptides to self-associate into polymers and networks. Although basic aspects of self-assembly in protein systems have been demonstrated, it remains a major challenge to create materials whose large-scale structures are well determined from design of local protein-protein interactions. Here, we show the design and characterization of a helical peptide, which uses phased hydrophobic interactions to drive assembly into nanofilaments and fibrils (''nanoropes''). Using the hydrophobic effect to drive self-assembly circumvents problems of uncontrolled self-assembly seen in previous approaches that used electrostatics as a mode for self-assembly. The nanostructures designed here are characterized by biophysical methods including analytical ultracentrifugation, dynamic light scattering, and circular dichroism to measure their solution properties, and atomic force microscopy to study their behavior on surfaces. Additionally, the assembly of such structures can be predictably regulated by using various environmental factors, such as pH, salt, other molecular crowding reagents, and specifically designed ''capping'' peptides. This ability to regulate self-assembly is a critical feature in creating smart peptide biomaterials. biomaterial ͉ coiled coil ͉ protein design ͉ circular dichroism ͉ atomic force microscopy Freely available online through the PNAS open access option.
Functionalized Self-Assembling Peptides for Medical Applications
2012
In this study, functionalized self-assembling peptides (SAPs) were designed and developed for the applications of liver bleeding hemostasis and skin wound healing. The physiochemical properties of SAPs were investigated including nanofiber morphology, hydrogel rheology behavior, titration curve and protein secondary structure. The functionalized SAPs have been proven to effectively promote hemostasis efficacy of liver bleeding and skin tissue regeneration process.
Reversible Self-Assembly: A Key Feature for a New Class of Autodelivering Therapeutic Peptides
Molecular Pharmaceutics, 2009
Effective delivery is a critical issue in the use of conventional free drugs. Studies on the structure-function relationship of a therapeutic antibody-derived candidacidal decapeptide (killer peptide, KP) revealed its ability to spontaneously and reversibly self-assemble in an organized network of fibril-like structures. This process is catalyzed by 1,3-beta-glucans. While the self-assembled state may provide protection against proteases and the slow kinetic of dissociation assures a release of the active dimeric form over time, the beta-glucan affinity is responsible for targeted delivery. Thus, KP represents a novel paradigm of targeted autodelivering drugs.