Browsing by Author "Soliman, M."
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Item Embargo Design rules for de novo self-assembling peptide nanostructures(Springer, 2023-06-13) Khedr, A.; Soliman, M.; Elsawy, M.Self-assembling peptides represent a versatile chemical toolbox for the development of discrete nanostructures that can be tailored for a variety of biomedical applications. Rational design of a peptide building block involves wise selection from the amino acids pool to create a primary sequence capable of adopting a bioinspired secondary structure stabilized by a combination of non-covalent and/or covalent interactions in response to external stimuli. Herein, we focus on the basic molecular design rules for self-assembling peptides as the building units for supramolecular nanomaterials formation through a bioinspired bottom-up design strategy. We look at the physicochemical nature of different amino acids and their proposed sequence arrangements needed to guide the molecular assembly into higher-order structures governed by certain types of intra- and/or intermolecular interactions and to give insights into how the materials’ structural and functional properties can be fine-tuned to satisfy different application needs. We will discuss the structural features of biosynthesized protein nanomaterials (such as collagen, elastin-like, silk-elastin-like, keratin, and resilin) and how they inspired the development of mimetic self-assembling polypeptide analogues of shorter length, while keeping the inherent material properties of the parent designs. In addition, design rules of de novo short peptides which assemble into higher bioinspired structures (β-sheets, β-hairpins, α-helices and amphiphiles assembly), as well as unconventional peptide designs (short aromatic and cyclic peptides), are also explained. This is an introductory chapter that gives a comprehensive overview of the basic design rules for the main classes of self-assembling peptides, which are discussed in more details in the relevant chapter for each class.Item Embargo Peptide and protein emulsifiers(Springer, 2023-06-13) Soliman, M.; Khedr, A.; Elsawy, M.There has recently been a growing attention towards peptide and protein molecules as potential bioemulsifiers for the stabilization of foams and emulsions, thanks to their innate tendency towards interfacial adsorption. Additionally, peptides and proteins are biodegradable and biocompatible, making them less toxic if compared to traditional emulsifiers. This chapter provides a comprehensive overview of the different classes of peptide, protein and mixed protein–polysaccharide emulsifiers and discusses the emulsification mechanisms of these systems. In essence, peptide-mediated emulsification can occur either via traditional surfactant-like mechanism, where amphiphilic molecular peptide chains adsorb at the biphasic interface forming ‘spherical micelles’, or through peptide self-assembly into higher secondary structure (α-helices or β-sheets) with the formation of amphiphilic nanofibrous structures adsorbing at the interface. Moreover, peptides can self-assemble in the continuous aqueous phase forming nanofibrous network of viscous hydrogels that enhance system stability. On the other hand, emulsion stabilization by proteins is mainly achieved through either electrostatic repulsion or steric stabilization. The various characterization techniques for emulsification and interfacial stabilization will be visited throughout this chapter, focusing on structural, mesoscopic and macroscopic characterization of these systems.Item Open Access Unraveling the Atomistic Mechanism of Electrostatic Lateral Association of Peptide 𝜷-Sheet Structures and Its Role in Nanofiber Growth and Hydrogelation(Small, 2025-01-09) Soliman, M.; Khedr, A.; Sahota, T. S.; Armitage, Rachel; Allan, Raymond N.; Laird, Katie; Allcock, N.; Ghuloum, F. I.; Amer, M. H.; Alazragi, R.; Edwards-Gayle, C. J. C.; Wychowaniec, Jacek K.; Vargiu, A. V.; Elsawy, M.Guiding molecular assembly of peptides into rationally engineered nanostructures remains a major hurdle against the development of functional peptide-based nanomaterials. Various non-covalent interactions come into play to drive the formation and stabilization of these assemblies, of which electrostatic interactions are key. Here, the atomistic mechanisms by which electrostatic interactions contribute toward controlling self-assembly and lateral association of ultrashort β-sheet forming peptides are deciphered. Our results show that this is governed by charge distribution and ionic complementarity, both affecting the interaction patterns between charged residues: terminal, core, and/or terminal-to-core attraction/repulsion. Controlling electrostatic interactions enabled fine-tuning nanofiber morphology for the 16 examined peptides, resulting into versatile nanostructures ranging from extended thin fibrils and thick bundles to twisted helical "braids" and short pseudocrystalline nanosheets. This in turn affected the physical appearance and viscoelasticity of the formed materials, varying from turbid colloidal dispersions and viscous solutions to soft and stiff self-supportive hydrogels, as revealed from oscillatory rheology. Atomistic mechanisms of electrostatic interaction patterns were confirmed by molecular dynamic simulations, validating molecular and nanoscopic characterization of the developed materials. In essence, detailed mechanisms of electrostatic interactions emphasizing the impact of charge distribution and ionic complementarity on selfassembly, nanostructure formation, and hydrogelation are reported.