Prevention of aggregation and renaturation of carbonic anhydrase via weak association with octadecyl- or azobenzene-modified poly(acrylate) derivatives

Immobilized Cellulase on NH2-MIL-88(Fe) and Its Performance as a Biocatalyst

To broaden pH range and improve thermal stability, reusability, storage stability, and organic solvent tolerance of natural enzymes, a magnetic material (NH2-MIL-88(Fe)) was synthesized as a new material to immobilize cellulase. The results showed that the optimal temperature and pH of cellulase immobilized on NH2-MIL-88(Fe) showed a wider range compared to free cellulase, and 74% and 83% of the initial activity could be retained after 10 cycles and storage for 49 days, respectively. Moreover, the tolerance for organic solvents was improved compared with free enzyme. The reducing sugar yields from sodium carboxymethylcellulose (CMC) and corn cob hydrolyzed with cellulase immobilized on NH2-MIL-88(Fe) were higher than observed with the free enzyme, which demonstrated the better biocatalytic performance of cellulase immobilized on NH2-MIL-88(Fe).

Synthetic Sulfated Polymers Control Amyloid Aggregation of Ovine Prion Protein and Decrease Its Toxicity

Amyloid aggregation, including aggregation and propagation of prion protein, is a key factor in numerous human diseases, so-called amyloidosis, with a very poor ability for treatment or prevention. The present work describes the effect of sulfated or sulfonated polymers (sodium dextran sulfate, polystyrene sulfonate, polyanethole sulfonate, and polyvinyl sulfate) on different stages of amyloidogenic conversion and aggregation of the prion protein, which is associated with prionopathies in humans and animals. All tested polymers turned out to induce amyloid conversion of the ovine prion protein. As suggested from molecular dynamics simulations, this effect probably arises from destabilization of the native prion protein structure by the polymers. Short polymers enhanced its further aggregation, whereas addition of high-molecular poly(styrene sulfonate) inhibited amyloid fibrils formation. According to the seeding experiments, the protein–polymer complexes formed after incubation with poly(styrene sulfonate) exhibited significantly lower amyloidogenic capacity compared with the control fibrils of the free prion protein. The cytotoxicity of soluble oligomers was completely inhibited by treatment with poly(styrene sulfonate). To summarize, sulfonated polymers are a promising platform for the formulation of a new class of anti-prion and anti-amyloidosis therapeutics.

Azobenzene-isoxazoline as photopharmacological ligand for optical control of insect GABA receptor and behavior

BACKGROUND

Photopharmacology is a fast-growing photonics-based technology, which realizes the high-resolution regulation of drugs in time and space through light. The purpose of this research was to introduce photochromic groups into the isoxazoline structure to realize the regulation of γ-Aminobutyric acid receptors (GABARs) targeting insect behavior.

RESULTS

Azobenzene-Fluralaner analogs ABF02, ABF03 and ABF04 have been proven to have larvicidal activity against mosquito larvae. Cis-ABF03 had excellent larvicidal activity against mosquito larvae with a median lethal concentration (LC₅₀ ) value of 1.63, which was better than that of trans-ABF03 (LC₅₀  = 3.90). In particular, ABF03 also showed insecticidal activity against Mythimna separata. Further experiments showed that ABF03 (1 μm) induced depolarization of dorsal unpaired median neurons after ultraviolet light irradiation, enhanced affinity to the receptor, and blocked ligand-gated chloride channels of GABARs. ABF03 (1 μm) realized the real-time photoregulation of the behavior of mosquito larvae, which indicated that the synthesized ligand can complete the binding and off-target action of drugs and targets in vivo under the regulation of light.

CONCLUSION

Azobenzene-Isoxazoline as photopharmacological ligand was synthesized and evaluated for optical control of insect GABARs and behavior for the first time. ABF03 completed the differential regulation of cockroach neurons and the real-time reversible regulation of insect behavior. The establishment of photochromic ligands provides a new strategy for basic and convenience-oriented research on GABARs in invertebrates. © 2021 Society of Chemical Industry.

Stacking of nanorings to generate nanotubes for acceleration of protein refolding

Self-assembly and photoisomerization of azobenzene-based amphiphilic molecules produced nanorings with an inner diameter of 25 nm and lengths of <40 nm. The nanorings, which consisted of a single bilayer membrane of the amphiphiles, retained their morphology in the presence of a stacking inhibitor; whereas in the absence of the inhibitor, the nanorings stacked into short nanotubes (<500 nm). When subjected to mild heat treatment, these nanotubes joined end-to-end to form nanotubes with lengths of several tens of micrometers. The nanorings and the short and long nanotubes were able to encapsulate proteins and thereby suppress aggregation induced by thermal denaturation. In addition, the nanotubes accelerated refolding of denatured proteins by encapsulating them and then releasing them into the bulk solution; refolding occurred simultaneously with release. In contrast, the nanorings did not accelerate protein refolding. Refolding efficiency increased with increasing nanotube length, indicating that the re-aggregation of the proteins was strictly inhibited by lowering the concentration of the proteins in the bulk solution as the result of the slow release from the longer nanotubes. The migration of the proteins through the long, narrow nanochannels during the release process will also contribute to refolding.

Interaction of Ionenes with Lipid Membrane: Unusual Impact of Charge Density

Synthetic water-soluble polymers are increasingly used for gene delivery, stabilization, and delivery of proteins, and as prospective antimicrobial and antiviral agents. Therefore, study of their interaction with lipid membranes is of special importance. Herein, we studied interaction of aliphatic cationic ionenes (recently tested for gene delivery efficiency) differed in the length of spacer between charged groups (and therefore in charge density) with anionic lipid membrane. A range of approaches such as measurement of particle size and electrophoretic mobility, liposome integrity, ATR-FTIR spectroscopy, isothermal titration calorimetry as well as atomistic molecular modeling was used. Ionene with a spacer of 10 methylene groups has been shown to be incorporated into membrane and interact with its inner hydrophobic part in contrast to ionenes with shorter spacer, which interacted only with outer polar head groups of lipids staying at the water-membrane interface. It affects membrane integrity and results in a different behavior of the polymer-liposome complexes. These findings are relevant for potential biomedical application of ionenes, including creation of composite polymer-liposome systems for drug delivery.

Visible Light Mediated Bidirectional Control over Carbonic Anhydrase Activity in Cells and in Vivo Using Azobenzenesulfonamides

Two azobenzenesulfonamide molecules with thermally stable cis configurations resulting from fluorination of positions ortho to the azo group are reported that can differentially regulate the activity of carbonic anhydrase in the trans and cis configurations. These fluorinated probes each use two distinct visible wavelengths (520 and 410 or 460 nm) for isomerization with high photoconversion efficiency. Correspondingly, the cis isomer of these systems is highly stable and persistent (as evidenced by structural studies in solid and solution state), permitting regulation of metalloenzyme activity without continuous irradiation. Herein, we use these probes to demonstrate the visible light mediated bidirectional control over the activity of zinc-dependent carbonic anhydrase in solution as an isolated protein, in intact live cells and in vivo in zebrafish during embryo development.

Alpha-Synuclein Amyloid Aggregation Is Inhibited by Sulfated Aromatic Polymers and Pyridinium Polycation

The effect of a range of synthetic charged polymers on alpha-synuclein aggregation and amyloid formation was tested. Sulfated aromatic polymers, poly(styrene sulfonate) and poly(anethole sulfonate), have been found to suppress the fibril formation. In this case, small soluble complexes, which do not bind with thioflavin T, have been formed in contrast to the large stick-type fibrils of free alpha-synuclein. Sulfated polysaccharide (dextran sulfate), as well as sulfated vinylic polymer (poly(vinyl sulfate)) and polycarboxylate (poly(methacrylic acid)), enhanced amyloid aggregation. Conversely, pyridinium polycation, poly(N-ethylvinylpyridinium), switched the mechanism of alpha-synuclein aggregation from amyloidogenic to amorphous, which resulted in the formation of large amorphous aggregates that do not bind with thioflavin T. The obtained results are relevant as a model of charged macromolecules influence on amyloidosis development in humans. In addition, these results may be helpful in searching for new approaches for synucleinopathies treatment with the use of natural polymers.

Reversible control of enzyme-inhibitor interactions with light illumination using a photoresponsive surfactant

The effects of a photoresponsive surfactant and light illumination on the complex formed between ribonuclease A (RNase A) and a protein ribonuclease inhibitor (RI) have been investigated to develop a light-based technique to reactivate an enzyme through surfactant-induced dissociation of the enzyme-inhibitor complex. The photoresponsive surfactant undergoes a photoisomerization from the relatively hydrophobic trans isomer under visible light to the relatively hydrophilic cis isomer upon UV illumination, providing a means to reversibly control protein-inhibitor interactions. In the absence of surfactant, RI binds tightly to RNase A through noncovalent interactions, which inhibits the enzyme activity. Upon addition of the surfactant under visible light, RNase A is reactivated, regaining ~75% of the native activity in the absence of RI. In the presence of the surfactant under UV light, however, the enzyme remains inhibited. Fluorescence spectroscopy, dynamic light scattering, and circular dichroism spectroscopy reveal that RI dramatically unfolds upon addition of the trans form of the surfactant, while RNase A does not undergo noticeable structural changes under the same conditions. This indicates that RNase A reactivation occurs through dissociation of the enzyme-inhibitor complex arising from surfactant-induced unfolding of the inhibitor. As a result, photoresponsive surfactant and light illumination can be used as a novel light-based technique to dissociate enzyme-inhibitor complexes and, thus, reactivate an inhibited enzyme.

In Situ Photoregulation of Carbonic Anhydrase Activity Using Azobenzenesulfonamides

We report two small molecule azobenzenesulfonamide probes, CAP1 and CAP2, capable of photomodulating the activity of carbonic anhydrase (CA) on demand. In the trans form, CAP azobenzene probes adopt a linear shape, making them suitable for occupying the CA active site and interacting with Zn²⁺, thereby inhibiting enzyme activity. Following irradiation with either 365 or 410 nm light, the CAP probes isomerize to their cis form. Because of the change in steric profile, the probe exits the active site, and the activity of the enzyme is restored. The cis isomer can revert back to the trans isomer through thermal relaxation or via photoirradiation with 460 nm light and thereby inhibit protein activity again. This process can be repeated multiple times without any photodegradation and thus can be used to inhibit or activate the protein reversibly. Importantly, we demonstrate our ability to apply CAP azobenzene probes to regulate CA activity both in an isolated protein solution and in live cells, where the two isomers of CAP1 differentially regulate the intracellular cytosolic pH.

Folding and stabilizing membrane proteins in amphipol A8-35

Membrane proteins (MPs) are important pharmacological targets because of their involvement in many essential cellular processes whose dysfunction can lead to a large variety of diseases. A detailed knowledge of the structure of MPs and the molecular mechanisms of their activity is essential to the design of new therapeutic agents. However, studying MPs in vitro is challenging, because it generally implies their overexpression under a functional form, followed by their extraction from membranes and purification. Targeting an overexpressed MP to a membrane is often toxic and expression yields tend to be limited. One alternative is the formation of inclusion bodies (IBs) in the cytosol of the cell, from which MPs need then to be folded to their native conformation before structural and functional analysis can be contemplated. Folding MPs targeted to IBs is a difficult task. Specially designed amphipathic polymers called 'amphipols' (APols), which have been initially developed with the view of improving the stability of MPs in aqueous solutions compared to detergents, can be used to fold both α-helical and β-barrel MPs. APols represent an interesting novel amphipathic medium, in which high folding yields can be achieved. In this review, the properties of APol A8-35 and of the complexes they form with MPs are summarized. An overview of the most important studies reported so far using A8-35 to fold MPs is presented. Finally, from a practical point of view, a detailed description of the folding and trapping methods is given.

Alumina nanoparticle-assisted enzyme refolding: A versatile methodology for proteins renaturation

We present a high-yield method for the renaturation of negatively charged enzymes. The approach is based on the use of alumina nanoparticles, which after electrostatic interaction with denatured protein molecules, prevent their aggregation and make the process of refolding controllable. The method, demonstrated by the renaturation of several enzymes, is efficient, rapid, employs a minimal amount of reagents and even can be applied to renature mixture of the denatured enzymes.

Selective Uptake and Refolding of Globular Proteins in Coacervate Microdroplets

Intrinsic differences in the molecular sequestration of folded and unfolded proteins within poly(diallyldimethylammonium) (PDDA)/poly(acrylate) (PAA) coacervate microdroplets are exploited to establish membrane-free microcompartments that support protein refolding, facilitate the recovery of secondary structure and enzyme activity, and enable the selective uptake and exclusion of folded and unfolded biomolecules, respectively. Native bovine serum albumin, carbonic anhydrase, and α-chymotrypsin are preferentially sequestered within positively charged coacervate microdroplets, and the unfolding of these proteins in the presence of increasing amounts of urea results in an exponential decrease in the equilibrium partition constants as well as the kinetic release of unfolded molecules from the droplets into the surrounding continuous phase. Slow refolding in the presence of positively charged microdroplets leads to the resequestration of functional proteins and the restoration of enzymatic activity; however, fast refolding results in protein aggregation at the droplet surface. In contrast, slow and fast refolding in the presence of negatively charged PDDA/PAA droplets gives rise to reduced protein aggregation and misfolding by interactions at the droplet surface to give increased levels of protein renaturation. Together, our observations provide new insights into the bottom-up design and construction of self-assembling microcompartments capable of supporting the selective uptake and refolding of globular proteins.