Search

An ability to construct biological matter from the molecule up holds promise for applications ranging from smart materials to integrated biophysical models for synthetic biology. Biomolecular self-assembly is an efficient strategy for biomaterial construction which can be programmed to support desired function. A challenge remains in replicating the strategy synthetically, that is at will, and differentially, that is for a specific function at a given length scale. Here we introduce a self-assembly topology enabling a net-like architectural mimetic of native extracellular matrices capable of differential responses to cell adhesion--enhanced mammalian cell attachment and proliferation, and enhanced resistance to bacterial colonization--at the native sub-millimeter length scales. The biological performance of such protein micro-nets directly correlates with their morphological and chemical properties, offering thus an application model for differential extracellular matrices.

A de novo topology of virus-like assembly is reported. The design is a trifaceted coiled-coil peptide helix, which self-assembles into ultrasmall, monodisperse, anionic virus-like shells that encapsulate and transfer both RNA and DNA into human cells. Unlike existing artificial systems, these shells share the same physical characteristics of viruses being anionic, nonaggregating, abundant, hollow, and uniform in size, while effectively mediating gene silencing and transgene expression. These are the smallest virus-like structures reported to date, both synthetic and native, with the ability to adapt and transfer small and large nucleic acids. The design thus offers a promising solution for engineering bespoke artificial viruses with desired functions.

We describe an approach that utilizes nonlinear peptides to direct the assembly of previously reported Self-Assembling Fibers (SAFs). The SAF system comprises two complementary linear peptides, SAF-p1 and SAF-p2a, which combine to form exclusively linear, nonbranched fibers. The Matrix-Programming (MaP) peptides described herein are based on these peptides: they comprise two or three half-peptide blocks derived from the SAF peptides, which are conjugated via dendritic hubs. Different MaP peptides coassembled with the standard SAF peptides to form specific structures, such as hyperbranched networks, polygonal matrices, and regularly segmented and terminated fibers. The role of each half-peptide block in dictating the different features has been elucidated. This provides a strong basis for designing new peptide-based nanostructured materials from the bottom up.

A general concept for designing self-assembling peptide fibrillar nano- to microstructures is described. The approach relies on the use of straightforward alpha-helical one-heptad (approximately 1 nm) modules without the need for more-specific designs. Various combinations of the modules gave a variety of constructs that were examined by a combination of spectroscopy and microscopy. These show that simple rearrangements and stereochemical conversions of the modules within similar templates lead to different fiber morphologies. The concept opens new strategies for designing fibrous materials with tunable properties at the nanoscale.

The chemical synthesis of polypeptide chains >50 amino acids with prescribed sequences is challenging. In one approach, native chemical ligation (NCL), short, unprotected peptides are connected through peptide bonds to render proteins in water. Here we combine chemical ligation with peptide self-assembly to deliver extremely long polypeptide chains with stipulated, repeated sequences. We use a self-assembling fiber (SAF) system to form structures tens of micrometers long. In these assemblies, tens of thousands of peptides align with their N- and C-termini abutting. This arrangement facilitates chemical ligation without the usual requirement for a catalytic cysteine residue at the reactive N-terminus. We introduced peptides with C-terminal thioester moieties into the SAFs. Subsequent ligation and disassembly of the noncovalent components produced extended chains > or =10 microm long and estimated at > or =3 MDa in mass. These extremely long molecules were characterized by a combination of biophysical, hydrodynamic, and microscopic measurements.

Fiber Recruiting (FiRe) peptides are described. These are derivatives of self-assembling fiber (SAF) forming peptides that are conjugated with small molecules (in our case, biotin or a FLAG-tag octapeptide). The FiRe peptides are co-assembled into fibers and used as bait to recruit folded and functional proteins to the fiber surfaces. This was demonstrated using two molecular recognition models: namely, a protein-ligand interaction (biotin-streptavidin) and an antigen-antibody (FLAG octapeptide-anti-FLAG-antibody) interaction. This concept offers an approach to mimicking in natural fibrillar systems, such as collagen or fibrin, that communicate specifically with their environments via incorporated or decorated active peptide and protein components.