PEG: The Magic Bullet for Biophysical Analysis of Highly Aggregating Small Molecules in Aqueous Solutions.

Biophysical research plays a crucial role in drug discovery, but many druglike molecules are poorly soluble and prone to aggregation, making their analysis challenging and susceptible to artifacts. To address this issue, we propose an approach that uses poly(ethylene glycol) (PEG) as an excipient in aqueous buffers to reduce the propensity of small molecules to aggregate. We show how PEG allows us to measure the thermodynamics of a complex formed by a heterobifunctional Small Molecule (hSM) that brings two proteins together.

Microsecond Motion of the Bacterial Transporter EmrE in Lipid Bilayers.

The bacterial transporter EmrE is a homo-dimeric membrane protein that effluxes cationic polyaromatic substrates against the concentration gradient by coupling to proton transport. As the archetype of the small multidrug resistance family of transporters, EmrE structure and dynamics provide atomic insights into the mechanism of transport by this family of proteins. We recently determined high-resolution structures of EmrE in complex with a cationic substrate, tetra(4-fluorophenyl)phosphonium (F-TPP), using solid-state NMR spectroscopy and an S64V-EmrE mutant.

Mitogen-like Cerium-Based Nanoparticles Protect against Severe Doses of X-rays.

Novel radioprotectors are strongly demanded due to their numerous applications in radiobiology and biomedicine, e.g., for facilitating the remedy after cancer radiotherapy.

The Strong Protective Action of Ce/F Combined Treatment on Tooth Enamel and Epithelial Cells.

We studied the toxic effects of cerium and fluoride species on human dental pulp stem cells and epithelial cells of as a surrogate for the human oral mucosa. The sequential use of CeCl and NHF solutions in equimolar sub-toxic concentrations enabled the possible toxic effects of individual components to be avoided, ensuring the preservation of the metabolic activity of the cells due to the formation of CeF nanoparticles. Cerium fluoride nanoparticles and terbium-doped cerium fluoride nanoparticles exhibited neither cytotoxicity nor genotoxicity to dental pulp stem cells, even at high concentrations (10 M).

Facile Synthesis of Stable Cerium Dioxide Sols in Nonpolar Solvents.

A method is proposed for the preparation of stable sols of nanocrystalline cerium dioxide in nonpolar solvents, based on surface modification of CeO nanoparticles obtained by thermal hydrolysis of concentrated aqueous solutions of ammonium cerium(IV) nitrate with residues of 2-ethylhexanoic and octanoic acids. The synthesis was carried out at temperatures below 100 °C and did not require the use of expensive and toxic reagents. An assessment of the radical-scavenging properties of the obtained sols using the superoxide anion-radical neutralization model revealed that they demonstrate notable antioxidant activity.

High-pH structure of EmrE reveals the mechanism of proton-coupled substrate transport.

The homo-dimeric bacterial membrane protein EmrE effluxes polyaromatic cationic substrates in a proton-coupled manner to cause multidrug resistance. We recently determined the structure of substrate-bound EmrE in phospholipid bilayers by measuring hundreds of protein-ligand H-F distances for a fluorinated substrate, 4-fluoro-tetraphenylphosphonium (F-TPP), using solid-state NMR. This structure was solved at low pH where one of the two proton-binding Glu14 residues is protonated.

From Angstroms to Nanometers: Measuring Interatomic Distances by Solid-State NMR.

Internuclear distances represent one of the main structural constraints in molecular structure determination using solid-state NMR spectroscopy, complementing chemical shifts and orientational restraints. Although a large number of magic-angle-spinning (MAS) NMR techniques have been available for distance measurements, traditional C and N NMR experiments are inherently limited to distances of a few angstroms due to the low gyromagnetic ratios of these nuclei. Recent development of fast MAS triple-resonance F and H NMR probes has stimulated the design of MAS NMR experiments that measure distances in the 1-2 nm range with high sensitivity.

CeO Nanoparticle-Containing Polymers for Biomedical Applications: A Review.

The development of advanced composite biomaterials combining the versatility and biodegradability of polymers and the unique characteristics of metal oxide nanoparticles unveils new horizons in emerging biomedical applications, including tissue regeneration, drug delivery and gene therapy, theranostics and medical imaging. Nanocrystalline cerium(IV) oxide, or nanoceria, stands out from a crowd of other metal oxides as being a truly unique material, showing great potential in biomedicine due to its low systemic toxicity and numerous beneficial effects on living systems. The combination of nanoceria with new generations of biomedical polymers, such as PolyHEMA (poly(2-hydroxyethyl methacrylate)-based hydrogels, electrospun nanofibrous polycaprolactone or natural-based chitosan or cellulose, helps to expand the prospective area of applications by facilitating their bioavailability and averting potential negative effects.

Structure and dynamics of the drug-bound bacterial transporter EmrE in lipid bilayers.

The dimeric transporter, EmrE, effluxes polyaromatic cationic drugs in a proton-coupled manner to confer multidrug resistance in bacteria. Although the protein is known to adopt an antiparallel asymmetric topology, its high-resolution drug-bound structure is so far unknown, limiting our understanding of the molecular basis of promiscuous transport. Here we report an experimental structure of drug-bound EmrE in phospholipid bilayers, determined using F and H solid-state NMR and a fluorinated substrate, tetra(4-fluorophenyl) phosphonium (F-TPP).

Structure and drug binding of the SARS-CoV-2 envelope protein transmembrane domain in lipid bilayers.

An essential protein of the SARS-CoV-2 virus, the envelope protein E, forms a homopentameric cation channel that is important for virus pathogenicity. Here we report a 2.1-Å structure and the drug-binding site of E's transmembrane domain (ETM), determined using solid-state NMR spectroscopy.

Structure and Drug Binding of the SARS-CoV-2 Envelope Protein in Phospholipid Bilayers.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of the ongoing COVID-19 pandemic. Successful development of vaccines and antivirals against SARS-CoV-2 requires a comprehensive understanding of the essential proteins of the virus. The envelope (E) protein of SARS-CoV-2 assembles into a cation-selective channel that mediates virus budding, release, and host inflammation response.

Two-dimensional F-C correlation NMR for F resonance assignment of fluorinated proteins.

F solid-state NMR is an excellent approach for measuring long-range distances for structure determination and for studying molecular motion. For multi-fluorinated proteins, assignment of F chemical shifts has been traditionally carried out using mutagenesis. Here we show 2D F-C correlation experiments that allow efficient assignment of the F chemical shifts.

Atomic structures of closed and open influenza B M2 proton channel reveal the conduction mechanism.

The influenza B M2 (BM2) proton channel is activated by acidic pH to mediate virus uncoating. Unlike influenza A M2 (AM2), which conducts protons with strong inward rectification, BM2 conducts protons both inward and outward. Here we report 1.

PVP-stabilized tungsten oxide nanoparticles: pH sensitive anti-cancer platform with high cytotoxicity.

Photochromic tungsten oxide (WO) nanoparticles stabilized by polyvinylpyrrolidone (PVP) were synthesized to evaluate their potential for biomedical applications. PVP-stabilized tungsten oxide nanoparticles demonstrated a highly selective cytotoxic effect on normal and cancer cells in vitro. WO nanoparticles were found to induce substantial cell death in osteosarcoma cells (MNNG/HOS cell line) with a half-maximal inhibitory concentration (IC50) of 5 mg/mL, while producing no, or only minor, toxicity in healthy human mesenchymal stem cells (hMSc).

Long-term impact of fecal transplantation in healthy volunteers.

Background: Fecal microbiota transplantation (FMT) has been recently approved by FDA for the treatment of refractory recurrent clostridial colitis (rCDI). Success of FTM in treatment of rCDI led to a number of studies investigating the effectiveness of its application in the other gastrointestinal diseases. However, in the majority of studies the effects of FMT were evaluated on the patients with initially altered microbiota.

The first inorganic mitogens: Cerium oxide and cerium fluoride nanoparticles stimulate planarian regeneration via neoblastic activation.

We report the first experimental evidence for the mitogenic action of cerium(IV) oxide and cerium(III) fluoride nanoparticles (CONs and CFNs) on the regeneration of a whole organism - freshwater flatworms Schmidtea mediterranea (planarian). Both types of cerium-containing nanoparticles are shown to be a highly potent mitogen for planaria. Both CONs and CFNs, in micro- and nanomolar concentrations, markedly accelerate planarian blastema growth, due to the enhancement of cellular proliferation, causing an increase in the mitotic index and in the quantity of blastema cells in regenerating planaria.

Elucidating Relayed Proton Transfer through a His-Trp-His Triad of a Transmembrane Proton Channel by Solid-State NMR.

Proton transfer through membrane-bound ion channels is mediated by both water and polar residues of proteins, but the detailed molecular mechanism is challenging to determine. The tetrameric influenza A and B virus M2 proteins form canonical proton channels that use an HxxxW motif for proton selectivity and gating. The BM2 channel also contains a second histidine (His), H27, equidistant from the gating tryptophan, which leads to a symmetric HxxxWxxxH motif.

High-Sensitivity Detection of Nanometer H-F Distances for Protein Structure Determination by H-Detected Fast MAS NMR.

Protein structure determination by solid-state NMR requires the measurement of many interatomic distances through dipole-dipole couplings. To obtain multiple long-range distance restraints rapidly and with high sensitivity, here we demonstrate a new H-detected fast magic-angle-spinning NMR technique that yields many long distances in a two-dimensional (2D)-resolved fashion. The distances are measured up to ∼15 Å, with an accuracy of better than 10%, between H and F, two nuclear spins that have the highest gyromagnetic ratios.

Rapid measurement of long-range distances in proteins by multidimensional C-F REDOR NMR under fast magic-angle spinning.

The ability to simultaneously measure many long-range distances is critical to efficient and accurate determination of protein structures by solid-state NMR (SSNMR). So far, the most common distance constraints for proteins are C-N distances, which are usually measured using the rotational-echo double-resonance (REDOR) technique. However, these measurements are restricted to distances of up to ~ 5 Å due to the low gyromagnetic ratios of N and C.

Ceria Nanoparticles-Decorated Microcapsules as a Smart Drug Delivery/Protective System: Protection of Encapsulated P. pyralis Luciferase.

The design of novel, effective drug delivery systems is one of the most promising ways to improve the treatment of socially important diseases. This article reports on an innovative approach to the production of composite microcontainers (microcapsules) bearing advanced protective functions. Cerium oxide (CeO) nanoparticles were incorporated into layer-by-layer polyelectrolyte microcapsules as a protective shell for an encapsulated enzyme (luciferase of Photinus pyralis), preventing its oxidation by hydrogen peroxide, the most abundant type of reactive oxygen species (ROS).

Fast Magic-Angle-Spinning F Spin Exchange NMR for Determining Nanometer F-F Distances in Proteins and Pharmaceutical Compounds.

Internuclear distances measured using NMR provide crucial constraints of three-dimensional structures but are often restricted to about 5 Å due to the weakness of nuclear-spin dipolar couplings. For studying macromolecular assemblies in biology and materials science, distance constraints beyond 1 nm will be extremely valuable. Here we present an extensive and quantitative analysis of the feasibility of F spin exchange NMR for precise and robust measurements of interatomic distances up to 1.

Protonation equilibria and pore-opening structure of the dual-histidine influenza B virus M2 transmembrane proton channel from solid-state NMR.

The influenza A and B viruses are the primary cause of seasonal flu epidemics. Common to both viruses is the M2 protein, a homotetrameric transmembrane proton channel that acidifies the virion after endocytosis. Although influenza A M2 (AM2) and B M2 (BM2) are functional analogs, they have little sequence homology, except for a conserved HW motif, which is responsible for proton selectivity and channel gating.

Facile fabrication of luminescent organic dots by thermolysis of citric acid in urea melt, and their use for cell staining and polyelectrolyte microcapsule labelling.

Luminescent organic dots (O-dots) were synthesized via a one-pot, solvent-free thermolysis of citric acid in urea melt. The influence of the ratio of the precursors and the duration of the process on the properties of the O-dots was established and a mechanism of their formation was hypothesized. The multicolour luminescence tunability and toxicity of synthesized O-dots were extensively studied.