Sekundärstrukturbildung als Triebkraft für die Selbstorganisation reaktiver Polypept(o)ide: Steuerung von Größe, Form und Funktion kernvernetzter Nanostrukturen

Ordered Conformation-Regulated Vesicular Membrane Permeability

In nature, the folding and conformation of proteins can control the cell or organelle membrane permeability and regulate the life activities. Here we report the first example of synthetic polypeptide vesicles that regulate their permeability via ordered transition of secondary conformations, in a manner similar to biological systems.  The polymersomes undergo a β-sheet to α-helix transition in response to reactive oxygen species (ROS), leading to wall thinning without loss of vesicular integrity. The change  of membrane structure increases the vesicular permeability and enables specific transport of payloads with different molecular weights.The change of membrane structure increases the vesicular permeability.  As a proof-of-concept, the polymersomes encapsulating enzymes could serve as nanoreactors and carries for glucose-stimulated insulin secretion in vivo inspired by human glucokinase, resulting in safe and effective treatment of type 1 diabetes mellitus in mouse models. This study will help understand the biology of biomembranes and facilitate the engineering of nanoplatforms for biomimicry, biosensing, and controlled delivery applications.

Allostery-Mimicking Self-assembly of Helical Poly(phenylacetylene) Block Copolymers and the Chirality Transfer

Allostery can regulate protein self-assembly which further affects biological activities, and achieving precise control over the chiral suprastructures during self-assembly remains challenging. Herein, to mimic the allosterical nature of proteins, the poly(phenylacetylene) block copolymers PPA-b-PsmNap with the dynamic helical backbone were synthesized to investigate their conformational-transition-induced self-assembly. As the helical conformation of the block PsmNap spontaneously transforms from cis-transiod to cis-cisoid, the decreasing solubility of PsmNap blocks in THF induced self-assembly of PPA-b-PsmNap. The self-assembly structures of copolymers can sequentially evolve from vesicles to nanobelts to helical strands during the process of conformation transformation. The screw sense of final helical strands was strictly correlated to the helicity of the block PsmNap. This is helpful to understand the mechanism of allostery-modulated self-assembly.

Fabrication of Pascal-triangle Lattice of Proteins by Inducing Ligand Strategy

A protein Pascal triangle has been constructed as new type of supramolecular architecture by using the inducing ligand strategy that we previously developed for protein assemblies. Although mathematical studies on this famous geometry have a long history, no work on such Pascal triangles fabricated from native proteins has been reported so far due to their structural complexity. In this work, by carefully tuning the specific interactions between the native protein building block WGA and the inducing ligand R‐SL, a 2D Pascal‐triangle lattice with three types of triangular voids has been assembled. Moreover, a 3D crystal structure was obtained based on the 2D Pascal triangles. The distinctive carbohydrate binding sites of WGA and the intralayer as well as interlayer dimerization of RhB was the key to facilitate nanofabrication in solution. This strategy may be applied to prepare and explore various sophisticated assemblies based on native proteins.

Combining Orthogonal Reactive Groups in Block Copolymers for Functional Nanoparticle Synthesis in a Single Step

We report on the synthesis of polysarcosine-block-poly(S-alkylsulfonyl)-l-cysteine block copolymers, which combine three orthogonal addressable groups enabling site-specific conversion of all reactive entities in a single step. The polymers are readily obtained by ring-opening polymerization (ROP) of corresponding α-amino acid N-carboxyanhydrides (NCAs) combining azide and amine chain ends, with a thiol-reactive S-alkylsulfonyl cysteine. Functional group interconversion of chain ends using strain-promoted azide-alkyne cycloaddition (SPAAC) and activated ester chemistry with NHS- and DBCO-containing fluorescent dyes could be readily performed without affecting the cross-linking reaction between thiols and S-alkylsulfonyl protective groups. Eventually, all three functionalities can be combined in the formation of multifunctional disulfide core cross-linked nanoparticles bearing spatially separated functionalities. The simultaneous attachment of dyes in core and corona during the formation of core-cross-linked nanostructures with controlled morphology is confirmed by fluorescence cross-correlation spectroscopy (FCCS).