Zdravko Kochovski

Precise and Reversible Protein-Microtubule-Like Structure with Helicity Driven by Dual Supramolecular Interactions

Protein microtubule is a significant self-assembled architecture found in nature with crucial biological functions. However, mimicking protein microtubules with precise structure and controllable self-assembly behavior remains highly challenging. In this work, we demonstrate that by using dual supramolecular interactions from a series of well-designed ligands, i.e., protein-sugar interaction and π-π stacking, highly homogeneous protein microtubes were achieved from tetrameric soybean agglutinin without any chemical or biological modification. Using combined cryo-EM single-particle reconstruction and computational modeling, the accurate structure of protein microtube was determined. The helical protein microtube is consisted of three protofilaments, each of which features an array of soybean agglutinin tetramer linked by the designed ligands. Notably, the microtubes resemble the natural microtubules in their structural and dynamic features such as the shape and diameter and the controllable and reversible assembly behavior, among others. Furthermore, the protein microtubes showed an ability to enhance immune response, demonstrating its great potential for biological applications.

Internal Morphology-Controllable Self-Assembly in Poly(Ionic Liquid) Nanoparticles

Precise control of the interior and outer shapes of polymer nanoparticles has found broad interest in nanosciences, for example, in fundamental studies of their physical properties, colloidal behavior, and corresponding applications. Realizing such control below the 50 nm scale (i.e., a size scale close to individual polymer chains) requires accurate manipulation of polymerization techniques and a judicious choice of the chemical structure in monomers and/or polymers. Here, we constructed a series of well-defined sub-50 nm homopolymer nanoparticles with controllable shape and highly ordered, complex internal structures with sub-5 nm domain spacings, starting from 1-vinyl-1,2,4-triazolium-type ionic liquids in a one-pot dispersion polymerization. With cryogenic electron microscopy and tomography, a morphological evolution of particle shape and interior at this extremely small size end, unusual for polymer colloids, was identified and investigated in detail.

General Synthetic Route toward Highly Dispersed Metal Clusters Enabled by Poly(ionic liquid)s

The ability to synthesize a broad spectrum of metal clusters (MCs) with their size controllable on a subnanometer scale presents an enticing prospect for exploring nanosize-dependent properties. Here we report an innovative design of a capping agent from a polytriazolium poly(ionic liquid) (PIL) in a vesicular form in solution that allows for crafting a variety of MCs including transition metals, noble metals, and their bimetallic alloy with precisely controlled sizes (∼1 nm) and record-high catalytic performance. The ultrastrong stabilization power is a result of an unusual synergy between the conventional binding sites in the heterocyclic cations in PIL and an in situ generated polycarbene structure induced simultaneously to the reduction reaction.

One-pot synthesis of double poly(ionic liquid) block copolymers by cobalt-mediated radical polymerization-induced self assembly (CMR-PISA) in water

Amphiphilic double poly(ionic liquid) (PIL) block copolymers are directly prepared by cobalt-mediated radical polymerization induced self-assembly (CMR-PISA) in water of N-vinyl imidazolium monomers carrying distinct alkyl chains. The cobalt-mediated radical polymerization of N-vinyl-3-ethyl imidazolium bromide (VEtImBr) is first carried out until high conversion in water at 30 °C, using an alkyl bis(acetylacetonate)cobalt(III) adduct as initiator and controlling agent. The as-obtained hydrophilic poly(N-vinyl-3-ethyl imidazolium bromide) (PVEtImBr) is then used as a macroinitiator for the CMR-PISA of N-vinyl-3-octyl imidazolium bromide (VOcImBr). Self-assembly of the amphiphilic PVEtImBr-b-PVOcImBr block copolymer, i.e., of PIL-b-PIL-type, rapidly takes place in water, forming polymer nanoparticles consisting of a hydrophilic PVEtImBr corona and a hydrophobic PVOcImBr core. Preliminary investigation into the effect of the size of the hydrophobic block on the dimension of the nanoparticles is also described.

Thermosensitive Cu2O–PNIPAM core–shell nanoreactors with tunable photocatalytic activity

We report a facile and novel method for the fabrication of Cu2O@PNIPAM core-shell nanoreactors using Cu2O nanocubes as the core. The PNIPAM shell not only effectively protects the Cu2O nanocubes from oxidation, but also improves the colloidal stability of the system. The Cu2O@PNIPAM core-shell microgels can work efficiently as photocatalyst for the decomposition of methyl orange under visible light. A significant enhancement in the catalytic activity has been observed for the core-shell microgels compared with the pure Cu2O nanocubes. Most importantly, the photocatalytic activity of the Cu2O nanocubes can be further tuned by the thermosensitive PNIPAM shell, as rationalized by our recent theory.

Highly Ordered Self‐Assembly of Native Proteins into 1D, 2D, and 3D Structures Modulated by the Tether Length of Assembly‐Inducing Ligands

In nature, proteins self-assemble into various structures with different dimensions. To construct these nanostructures in laboratories, normally proteins with different symmetries are selected. However, most of these approaches are engineering-intensive and highly dependent on the accuracy of the protein design. Herein, we report that a simple native protein LecA assembles into one-dimensional nanoribbons and nanowires, two-dimensional nanosheets, and three-dimensional layered structures controlled mainly by small-molecule assembly-inducing ligands RnG (n=1, 2, 3, 4, 5) with varying numbers of ethylene oxide repeating units. To understand the formation mechanism of the different morphologies controlled by the small-molecule structure, molecular simulations were performed from microscopic and mesoscopic view, which presented a clear relationship between the molecular structure of the ligands and the assembled patterns. These results introduce an easy strategy to control the assembly structure and dimension, which could shed light on controlled protein assembly.

“Sweet” Architecture-Dependent Uptake of Glycocalyx-Mimicking Nanoparticles Based on Biodegradable Aliphatic Polyesters by Macrophages

Glyconanoparticles made by self-assembled glycopolymers currently are practical and efficient mimics of the glycocalyx on cell surfaces. Considering the complexity of the glycocalyx, glyconanoparticles with different sugars on their coronas, i.e., mixed-shell glycomicelles, could be more valuable compared to homoshell micelles. In this paper, we explore the architectural effect of the glyconanoparticle corona on glyconanoparticle macrophage endocytosis and lectin-binding ability. A series of glyconanoparticles composed of a biodegradable polyester backbone functionalized with galactoside or mannoside pendants were designed and prepared. The different architectures explored were single-component (galactoside or mannoside) coronas, homogeneously mixed coronas (MG) made by galactoside-mannoside copolymer chains, and blend-mixed coronas (M/G) constructed from two homoglycopolymers. Nanoparticles with a mixed shell showed a higher efficiency in cellular uptake and lectin-binding than those with a single sugar component. Meanwhile, unexpectedly, MG presented a significantly higher efficiency than M/G, although they had the same particle size and ratio of mannoside to galactoside. We attributed this apparent architectural effect to the difference in the phase behavior between MG and M/G; i.e., the former having a homogeneous corona allowed more sugar-receptor interactions in the contact region, while the latter having phase separation limited the simultaneous interaction of the two kinds of sugar units with the cell receptors.

Advancing Drug Formulation Additives toward Precision Additives with Release Mediating Peptide Interlayer

Amphiphilic drug formulation additives based on palmitic acid-modified poly(ethylene glycol) (Pal-PEG) are combined with a tailored drug binding peptide that is positioned at the hydrophobic-hydrophilic interface. The peptide originates from combinatorial selection and enables precise modulation of the drug release profiles. While Pal provides a cost-effective reservoir for drug storage, the PEG realizes solubility and shielding. The precision additives reach high payloads close to 1:1, rendering a photosensitizer water-soluble and providing adjustable drug activation kinetics by fine-tuning the peptide interface layer.

Self-assembly of Human Galectin-1 via dual supramolecular interactions and its inhibition of T-cell agglutination and apoptosis

Recently, we proposed a new strategy to construct artificial plant protein assemblies, which were induced by adding a small molecule, based on dual supramolecular interactions. In this paper, we further explored this method by employing Human Galectin-1 (Gal-1) as a building block to form self-assembled microribbons. Two non-covalent interactions, including lactose–lectin binding and dimerization of Rhodamine B (RhB), induced by the small molecule ligand addition, were involved in the crosslinking of the animal protein, resulting in the formation of assemblies. By using transmission electron microscopy (TEM), cryo-electron microscopy (cryo-EM), and three-dimensional (3D) tomographic analysis, we arrived at a possible mechanistic model for the microribbon formation. Furthermore, the morphology of protein assemblies could be fine-tuned by varying the incubation time, the protein/ligand ratio, and the chemical structures of ligands. Interestingly, the formation of protein microribbons successfully inhibited Gal-1 induced T-cell agglutination and apoptosis. This is because the multivalent and dynamic interactions in protein assemblies compete with the binding between Gal-1 and the glycans on cell surfaces, which suppresses the function of Gal-1 in promotion of tumor progression and metastasis.

CO2-switchable response of protein microtubules: behaviour and mechanism

Recently, we proposed a small molecular “inducing ligand” strategy to assemble proteins into highly-ordered structures via dual non-covalent interactions, i.e. carbohydrate–protein interaction and dimerization of Rhodamine B. Using this approach, artificial protein microtubules were successfully constructed. In this study, we find that these microtubules exhibit a perfect CO2 responsiveness; assembly and disassembly of these microtubules were nicely controlled by the alternative passage of CO2 and N2. Upon the injection of CO2, a negative net-charged SBA turns into a neutral or positive net-charged SBA, which elongated, to some extent, the effective distance between SBA and Rhodamine B, resulting in the disassociation of the Rhodamine B dimer. Further experimental and simulation results reveal that the CO2-responsive mechanism differs from that of solubility change of the previously reported CO2-responsive synthetic materials.