Abstract
BackgroundDue to their natural tendency to self-assemble, proteins and peptides are important components for organic nanotechnology. One particular class of peptides of recent interest is those that form amyloid fibrils, as this self-assembly results in extremely strong, stable quasi-one-dimensional structures which can be used to organise a wide range of cargo species including proteins and oligonucleotides. However, assembly of peptides already conjugated to proteins is limited to cargo species that do not interfere sterically with the assembly process or misfold under the harsh conditions often used for assembly. Therefore, a general method is needed to conjugate proteins and other molecules to amyloid fibrils after the fibrils have self-assembled.ResultsHere we have designed an amyloidogenic peptide based on the TTR105-115 fragment of transthyretin to form fibrils that display an alkyne functionality, important for bioorthogonal chemical reactions, on their surface. The fibrils were formed and reacted both with an azide-containing amino acid and with an azide-functionalised dye by the Huisgen cycloaddition, one of the class of “click” reactions. Mass spectrometry and total internal reflection fluorescence optical microscopy were used to show that peptides incorporated into the fibrils reacted with the azide while maintaining the structure of the fibril. These click-functionalised amyloid fibrils have a variety of potential uses in materials and as scaffolds for bionanotechnology.DiscussionAlthough previous studies have produced peptides that can both form amyloid fibrils and undergo “click”-type reactions, this is the first example of amyloid fibrils that can undergo such a reaction after they have been formed. Our approach has the advantage that self-assembly takes place before click functionalization rather than pre-functionalised building blocks self-assembling. Therefore, the molecules used to functionalise the fibril do not themselves have to be exposed to harsh, amyloid-forming conditions. This means that a wider range of proteins can be used as ligands in this process. For instance, the fibrils can be functionalised with a green fluorescent protein that retains its fluorescence after it is attached to the fibrils, whereas this protein loses its fluorescence if it is exposed to the conditions used for aggregation.
Highlights
Due to their natural tendency to self-assemble, proteins and peptides are important components for organic nanotechnology
The strategy is highly adaptable with the potential for proteins to be attached to fibrils via a non-natural amino acid inserted at any position in the protein or for the same protein molecule to be attached to multiple fibrils, in contrast with existing methods where the protein can only be attached at one terminus [22]
We showed that an approach that proceeds via click-reactive scaffolds allows a wide variety of molecular species to be used, including ones that are not compatible with the conditions required for self-assembly mediated nanoscale organization
Summary
Due to their natural tendency to self-assemble, proteins and peptides are important components for organic nanotechnology. Introducing chemical functionality to these self-assembled biomaterials has hitherto often required the material to self-assemble from components that already include the functional moiety In this approach, the choice of functionality is limited to species that can survive the conditions of self-assembly with their function intact and that do not themselves disturb it [19]. We address this limitation with a new method, which allows the fibrils to be functionalized after they are formed using mild conditions that tolerate a wide range of substrates We show that this approach allows even sensitive proteins which are not compatible with the selfassembly conditions to be used as the cargo and that this strategy significantly extends the chemical space of available for selecting species that can be organized on the nanoscale through peptide self-assembly. It means that proteins can be conjugated to fibrils at a different position in cases where terminal conjugation would inhibit the function of the protein
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
