An M protein coiled coil unfurls and exposes its hydrophobic core to capture LL-37

Surface-associated, coiled-coil M proteins of Streptococcus pyogenes (Strep A) disable human immunity through interaction with select proteins. However, coiled coils lack features typical of protein-protein interaction sites, and it is therefore challenging to understand how M proteins achieve specific binding, for example, with the human antimicrobial peptide LL-37, which results in its neutralization. The crystal structure of a complex of LL-37 with M87 protein, an antigenic variant from a strain that is an emerging threat, revealed a novel interaction mode. The M87 coiled coil unfurled and asymmetrically exposed its hydrophobic core to capture LL-37. A single LL-37 molecule bound M87 in the crystal, but in solution recruited additional LL-37 molecules, consistent with a protein trap neutralization mechanism. The interaction mode visualized crystallographically was verified to contribute significantly to LL-37 resistance in an M87 Strep A strain, and was identified to be conserved in a number of other M protein types that are prevalent in human populations. Our results provide specific detail for therapeutic inhibition of LL-37 neutralization by M proteins.

Effect of the enantiomeric structure of hydrophobic polymers on the encapsulation properties of a second near infrared (NIR-II) fluorescent dye for in vivo deep imaging

The enantiomeric structure of PLA affects its affinity for OTN-NIR fluorescent IR-1061 dye and its robustness when forming hydrophobic core micelles.

Selective methane electrosynthesis enabled by a hydrophobic carbon coated copper core–shell architecture

A hydrophobic core–shell architecture was constructed to control local H2O availability on the surface of the copper-based materials, which could provide a maximum generation rate of −434 mA cm−2 towards CH4.

Healthcare Applications of Nanoemulsions

The area of healthcare needs new innovative methods and tools for improvisation and to impart better efficiencies. Nanoemulsions are pharmaceutical formulations containing nanometre-sized particles used for controlled and systemic delivery of bioactive pharmaceuticals. Various advantageous properties of nanoemulsions such as the presence of hydrophobic core region, higher stability, and smaller size have made them useful to a large extent in the biomedical field. They have been employed in transdermal drug delivery, intranasal drug delivery, pulmonary drug delivery, parenteral drug delivery, and improvised delivery of hydrophobic drugs. This chapter aims to discuss various applications of nanoemulsions in healthcare including cosmetics, antimicrobials, vaccine delivery, targeted drug delivery, gene delivery, cancer therapy, and many more in detail.

A Brief Review on Hydrophobic Modifications of Glycol Chitosan into Amphiphilic Nanoparticles for Enhanced Drug Delivery

Glycol chitosan (GC) is the chitosan derivative that is capable of forming amphiphilic nanoparticles upon structure modifications at the reactive functional amine group on the polymer sugar backbone. Owing to the hydrophilic feature of GC and hydrophobic moieties that can be added to the GC structure, modifiable nanosystems were constructed to entrap poorly soluble drugs, mostly chemotherapeutic agents and several anti-inflammatory, anaesthetic, immunosuppressant, and antifungal drugs for more efficient delivery of the payload to the target site and improving the intended therapeutic effects. This review highlights the various hydrophobic molecules used in the chemical modification of GC to create amphiphilic nanoparticles for hydrophobic drug delivery, along with the summary of their physicochemical criteria and successful therapeutic enhancement achieved with the application of the drug-loaded amphiphiles. The biodegradable, GC-based nanoparticles particularly having the inner hydrophobic core and outer hydrophilic shell are an efficient system for drug entrapment, protection and targeting to improve the bioavailability and safety of the drug, in particular for cancer treatment purposes. The significant drug delivery enhancements achieved by these various hydrophobically-modified GC nanoparticles may provide the insights for their further use in nanomedicine.

Random and Diblock Thermoresponsive Oligo(ethylene glycol)-Based Copolymers Synthesized via Photo-Induced RAFT Polymerization

Amphiphilic random and diblock thermoresponsive oligo(ethylene glycol)-based (co)polymers were synthesized via photoiniferter polymerization under visible light using trithiocarbonate as a chain transfer agent. The effect of solvent, light intensity and wavelength on the rate of the process was investigated. It was shown that blue and green LED light could initiate RAFT polymerization of macromonomers without an exogenous initiator at room temperature, giving bottlebrush polymers with low dispersity at sufficiently high conversions achieved in 1–2 h. The pseudo-living mechanism of polymerization and high chain-end fidelity were confirmed by successful chain extension. Thermoresponsive properties of the copolymers in aqueous solutions were studied via turbidimetry and laser light scattering. Random copolymers of methoxy- and alkoxy oligo(ethylene glycol) methacrylates of a specified length formed unimolecular micelles in water with a hydrophobic core consisting of a polymer backbone and alkyl groups and a hydrophilic oligo(ethylene glycol) shell. In contrast, the diblock copolymer formed huge multimolecular micelles.

RAFT Emulsion Polymerization of Styrene Using a Poly((N,N-dimethyl acrylamide)-co-(N-isopropyl acrylamide)) mCTA: Synthesis and Thermosensitivity

Thermoresponsive poly((N,N-dimethyl acrylamide)-co-(N-isopropyl acrylamide)) (P(DMA-co-NIPAM)) copolymers were synthesized via reversible addition−fragmentation chain transfer (RAFT) polymerization. The monomer reactivity ratios were determined by the Kelen–Tüdős method to be rNIPAM = 0.83 and rDMA = 1.10. The thermoresponsive properties of these copo-lymers with varying molecular weights were characterized by visual turbidimetry and dynamic light scattering (DLS). The copolymers showed a lower critical solution temperature (LCST) in water with a dependence on the molar fraction of DMA in the copolymer. Chaotropic and kosmotropic salt anions of the Hofmeister series, known to affect the LCST of thermoresponsive polymers, were used as additives in the aqueous copolymer solutions and their influence on the LCST was demonstrated. Further on, in order to investigate the thermoresponsive behavior of P(DMA-co-NIPAM) in a confined state, P(DMA-co-NIPAM)-b-PS diblock copolymers were prepared via polymerization induced self-assembly (PISA) through surfactant-free RAFT mediated emulsion polymerization of styrene using P(DMA-co-NIPAM) as the macromolecular chain transfer agent (mCTA) of the polymerization. As confirmed by cryogenic transmission electron microscopy (cryoTEM), this approach yielded stabilized spherical micelles in aqueous dispersions where the PS block formed the hydrophobic core and the P(DMA-co-NIPAM) block formed the hydrophilic corona of the spherical micelle. The temperature-dependent behavior of the LCST-type diblock copolymers was further studied by examining the collapse of the P(DMA-co-NIPAM) minor block of the P(DMA-co-NIPAM)-b-PS diblock copolymers as a function of temperature in aqueous solution. The nanospheres were found to be thermosensitive by changing their hydrodynamic radii almost linearly as a function of temperature between 25 °C and 45 °C. The addition of kosmotropic salt anions, as a potentially useful tuning feature of micellar assemblies, was found to increase the hydrodynamic radius of the micelles and resulted in a faster collapse of the micelle corona upon heating.

Chloroplast Ribosomes Interact With the Insertase Alb3 in the Thylakoid Membrane

Members of the Oxa1/YidC/Alb3 protein family are involved in the insertion, folding, and assembly of membrane proteins in mitochondria, bacteria, and chloroplasts. The thylakoid membrane protein Alb3 mediates the chloroplast signal recognition particle (cpSRP)-dependent posttranslational insertion of nuclear-encoded light harvesting chlorophyll a/b-binding proteins and participates in the biogenesis of plastid-encoded subunits of the photosynthetic complexes. These subunits are cotranslationally inserted into the thylakoid membrane, yet very little is known about the molecular mechanisms underlying docking of the ribosome-nascent chain complexes to the chloroplast SecY/Alb3 insertion machinery. Here, we show that nanodisc-embedded Alb3 interacts with ribosomes, while the homolog Alb4, also located in the thylakoid membrane, shows no ribosome binding. Alb3 contacts the ribosome with its C-terminal region and at least one additional binding site within its hydrophobic core region. Within the C-terminal region, two conserved motifs (motifs III and IV) are cooperatively required to enable the ribosome contact. Furthermore, our data suggest that the negatively charged C-terminus of the ribosomal subunit uL4c is involved in Alb3 binding. Phylogenetic analyses of uL4 demonstrate that this region newly evolved in the green lineage during the transition from aquatic to terrestrial life.

Single Amino Acid Change Mutation in the Hydrophobic Core of the N-terminal Domain of P22 TSP affects the Proteins Stability.

The emergence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has significantly shifted the attention of researchers to critically investigate most viruses to understand specific characteristics that impart their virulence. For instance, the SARS-CoV-2 has undergone several mutations, with some variants classified as variants of concern, e.g., the Omicron and Delta variant of SARS-CoV-2 are known for their rapid transmission and antigenicity due to mutation in the Spike protein. P22 bacteriophage is a bacterial virus that has a tailspike protein (TSP) that performs similar functions as the Spike protein of SARS-COV-2. We previously carried out a site-directed mutagenesis of the P22 TSP to bear disruptive mutations in the hydrophobic core of the N-terminal Domain (NTD), then partially characterized the properties of the mutant TSPs. In this process, the valine patch (triple valine residues that formed a hydrophobic core) was replaced with charged amino acids (Asp or lysine) or hydrophobic amino acids (Leucine or isoleucine). Some of the mutant TSPs characterized showed significant differences in migration in both native and SDS-PAGE. Mutants with such disruptive mutation are known to show non-native properties, and as expected, most of these mutants obtained showed significantly different properties from the WT P22 TSP. In this work, we further characterized these mutant species by computational and in vitro assays to demonstrate the validity of our previous inference that the valine patch is a critical player in the stability of the N-terminal domain of the P22 TSP.

On the Dependence of Prion and Amyloid Structure on the Folding Environment

Currently available analyses of amyloid proteins reveal the necessity of the existence of radical structural changes in amyloid transformation processes. The analysis carried out in this paper based on the model called fuzzy oil drop (FOD) and its modified form (FOD-M) allows quantifying the role of the environment, particularly including the aquatic environment. The starting point and basis for the present presentation is the statement about the presence of two fundamentally different methods of organizing polypeptides into ordered conformations—globular proteins and amyloids. The present study shows the source of the differences between these two paths resulting from the specificity of the external force field coming from the environment, including the aquatic and hydrophobic one. The water environment expressed in the fuzzy oil drop model using the 3D Gauss function directs the folding process towards the construction of a micelle-like system with a hydrophobic core in the central part and the exposure of polarity on the surface. The hydrophobicity distribution of membrane proteins has the opposite characteristic: Exposure of hydrophobicity at the surface of the membrane protein with an often polar center (as in the case of ion channels) is expected. The structure of most proteins is influenced by a more or less modified force field generated by water through the appropriate presence of a non-polar (membrane-like) environment. The determination of the proportion of a factor different from polar water enables the assessment of the protein status by indicating factors favoring the structure it represents.