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Posted: Oct 07, 2014

Researchers design 'molecular Pom Poms' from self-assembling peptides

(Nanowerk News) Hierarchical process is a method of organization characteristic of social animals. But this behavior can also be observed in systems whose molecules "communicate" between them, that is, establishing weak interactions transmitting structural information. Starting from a specific type of peptides (amino acid chains) CiQUS (Centro Singular de Investigación en Química Biológica y Materiales Moleculares) researchers have developed a hierarchical system that, under appropriate conditions, self-assembles leading to spherical structures similar to the pom-poms used in some clothing.
molecular pom-pom
A molecular pom-pom.
In this study ("Molecular Pom Poms from Self-Assembling α,γ-Cyclic Peptides") they have designed cyclic peptides with ring shaped that can form pairs, dimers, as a first step of the hierarchical process. Then these dimers are stacked together to form tube-like structures, which finally self-assemble into the spherical shape structure, the molecular pom-poms. The researchers have also succeeded in controlling the dimensions and the outer surface shape of this structure depending on the temperature, the solvent and the concentration of the constituent peptides.
These pom-poms are porous materials that leave holes in which researchers have been able to incorporate other molecules such as fluorescent dyes. Such molecules allowed studying the process of encapsulation and release of the encapsulated molecules. Finally, once formed these structures, the outer surface may also be further modified by the addition of metal ions. These ions, due to the surface characteristics of the pom-poms, stick to them metallizing the surface, and consequently modifying the properties of the pompoms. Therefore, it is envisaged the development of new applications based on these novel materials where, thanks to the mentioned molecular control, it would be possible control not only their size and shape but also their outer and inner properties.
SEM images of molecular pom-poms
SEM images of the molecular pom-poms.
Due to this set of properties and the fact that these structures are comprised of peptides, it could provide a new technology with biomedical applications, e.g. for the transport and release of different types of drugs, although further work is required to exploit the properties of this new material.
Technical note
It has been shown that α,γ-cyclic peptide bearing a nicotinic acid attached to a serine residue through its side chain forms dimers that further self-organize in a hierarchical process to for pom-pom like molecular structures. These spherical structures are porous materials that encapsulate and subsequently liberate small molecules. The encapsulation process was followed by the incorporation of dyes and it was demonstrated that pom-pom formation takes place in the presence of dyes too, without altering the hierarchical process. In addition, the presence of the pyridine moiety allows the interaction with metal ions, and this facilitates metal coating of the sphere surface. This material might have biomedical applications. Further work is required to exploit the properties of this material.
Source: Universidade de Santiago de Compostela
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