Polyethylene Glycol Molecules Research Articles

Vortex Nanodiscs Functionalization to Overcome Macrophage Recognition for Efficient Theragnosis Applications

Biological barriers prevent nanotherapeutics successful accumulation at target cells, limiting diagnosis and treatment responses. Magnetic nanodiscs with a spin‐vortex ground state have shown great promise for magnetomechanical cancer cells annihilation and for neuronal stimulation, requiring very low concentrations for an effective result. However, the biological barriers that these particles encounter upon intravenous administration remain a challenge. Herein, the synthesis of biocompatible multilayered Au/Fe/Au nanodiscs with a spin‐vortex ground state and their inert surface modification is reported. Two different surface modifications with two distinct polyethylene glycol (PEG) molecules are performed, which successfully reduce macrophage uptake, while maintaining the nanodiscs’ biocompatibility. By effectively preventing nanodisc uptake, innovative design features can be rationally incorporated to create a new generation of specific nanotherapeutics by modifying the PEG surface with specific targeting molecules.

Angular-Inertia Regulated Stable and Nanoscale Sensing of Single Molecules Using Nanopore-In-A-Tube.

Nanopore is commonly used for high-resolution, label-free sensing, and analysis of single molecules. However, controlling the speed and trajectory of molecular translocation in nanopores remains challenging, hampering sensing accuracy. Here, the study proposes a nanopore-in-a-tube (NIAT) device that enables decoupling of the current signal detection from molecular translocation and provides precise angular inertia-kinetic translocation of single molecules through a nanopore, thus ensuring stable signal readout with high signal-to-noise ratio (SNR). Specifically, the funnel-shaped silicon nanopore, fabricated at a 10-nm resolution, is placed into a centrifugal tube. A light-induced photovoltaic effect is utilized to achieve a counter-balanced state of electrokinetic effects in the nanopore. By controlling the inertial angle and centrifugation speed, the angular inertial force is harnessed effectively for regulating the translocation process with high precision. Consequently, the speed and trajectory of the molecules are able to be adjusted in and around the nanopore, enabling controllable and high SNR current signals. Numerical simulation reveals the decisive role of inertial angle in achieving uniform translocation trajectories and enhancing analyte-nanopore interactions. The performance of the device is validated by discriminating rigid Au nanoparticles with a 1.6-nm size difference and differentiating a 1.3-nm size difference and subtle stiffness variations in flexible polyethylene glycol molecules.

Application of Resonant Plasmonic Bowtie Nanoantennas for Optically‐Assisted Diffusiophoretic Trapping of Extracellular Vesicles and Nanoparticles

AbstractPlasmonic antennas leveraging localized surface plasmon resonances (LSPR) hold a significant premise for efficiently trapping nanoscale particles at low power levels. However, their effectiveness is hindered by photothermal effects that arise with metallic nanoparticles, leading to decreased stability of trapped particles. To address this limitation, a hybrid approach that combines depletion attraction and photothermal effects inherent in plasmonic structures is proposed, capitalizing on thermally induced concentration gradients. Through the thermophoretic depletion of polyethylene glycol (PEG) molecules around plasmonic hotspots, sharp concentration gradients are created, enabling precise localization of nanoscopic particles through a synergistic effect with diffusiophoretic forces. Our experiments successfully demonstrate the ability to trap and dynamically manipulate small extracellular vesicles and 100 nm polystyrene beads, showcasing the platform's potential for assembly at the nanoscale. Remarkably, this method maintains stable trapping performance even at a laser power of . The demonstration of stable trapping of small extracellular vesicles showcases the compatibility of this platform with bio species. This study introduces a promising avenue for the precise and efficient manipulation of nanoscale particles, with wide‐ranging implications in nanotechnology, biophysics, and nanomedicine. This research opens new opportunities for advancing nanoscale particle studies and applications, ushering in a new era of nanoscale manipulation techniques.

A Library of Custom PEG-Lipids reveals a Double-PEG-Lipid with Drastically Enhanced Paclitaxel Solubility and Human Cancer Cell Cytotoxicity when used in Fluid Micellar Nanoparticles.

Paclitaxel (PTX) is one of the most widely utilized chemotherapeutics globally. However, the extremely poor water solubility of paclitaxel necessitates a mechanism of delivery within blood. Fluid lipid PTX nanocarriers (lipids in the chain-melted state) show promise as PTX delivery vectors, but remain limited by their solubility of PTX within the membrane. To improve pharmacokinetics, membrane surfaces are typically coated with polyethylene glycol (PEG). Recent work has demonstrated the generation of a population of micelles within fluid lipid formulations containing a 2kDa PEG-lipid at a 10 mol% ratio. Driven by the positive curvature of the PEG-lipid (i.e. area of head group > area of tails), micelle-containing formulations were found to exhibit significantly higher uptake in cancer cells, cytotoxicity, and in vivo antitumor efficacy compared to formulations containing solely liposomes. Here, we describe the custom synthesis of a library of high-curvature micelle-inducing PEG-lipids and examine the effects of PEG chain length, chain branching (single- or double-PEG-lipid), and cationic charge on PTX solubility and cytotoxicity. We examined PEG-lipids at standard (10 mol%) and high (100-x mol%, where x=PTX mol%) formulation ratios. Remarkably, all formulations containing the synthesized high-curvature PEG-lipids had improved PTX solubility over unPEGylated formulations and commercially available DOPE-5k. The highest PTX solubility was found within the 100-xPTX mol% PEG-lipid micellar formulations, with particles made from 2k2 (two PEG2k chains) encapsulating 13 mol% PTX for up to 24 h. The pancreatic cancer cell line PC3 exhibited higher sensitivity to formulations containing PEG-lipid at 100-xPTX mol%, the most potent of which being formulations made from 2k2 (IC50 = 14 nM). The work presented here suggests formulations employing high-curvature PEG-lipids, particularly the double-PEG-lipid 2k2, hold great potential as next-generation PTX delivery systems owing to their high PTX solubility, enhanced cell cytotoxicity, and ability for precision targeting by affixation of ligands to the PEG molecules.

Volumetric and ultrasonic studies of molecular interactions in binary mixtures of N,N-dimethylacetamide with some polyethylene glycols at temperatures from 293.15 to 323.15 K

The intermolecular interactions in N,N-dimethylacetamide (DMA) + polyethylene glycol (PEG) mixtures have been examined from the measurements of the densities, ρ and speeds of sound, u of DMA + PEG 200 or PEG 300 or PEG 400 or PEG 600 mixtures over the entire mole fraction range at temperatures, T = (293.15–323.15) K and atmospheric pressure. Various excess parameters, viz., excess molar volume, excess isentropic compressibility, excess intermolecular free length, excess speed of sound, excess molar isentropic compressibility and excess acoustic impedance were evaluated using measured data. These excess properties were correlated with the Redlich–Kister equation. In addition, the partial molar volume and compressibility; excess partial molar volume and compressibility of the components over the entire composition range; and partial molar volume and compressibility and excess partial molar volume and compressibility of the components at infinite dilution have also been calculated. These evaluated parameters have been interpreted by means of prevailing intermolecular interactions in these mixtures. The presence of strong intermolecular interactions among DMA and PEG molecules have been revealed from the evaluated parameters of these mixtures. The speeds of sound were predicted theoretically using scaled particle theory and compared with experimental values. FT-IR spectra of pure DMA, PEG 200 and their equimolar mixtures were also recorded and analysed for better understanding of prevailing intermolecular interaction.

Molecular insights into the interactions between PEG carriers and drug molecules from Celastrus hindsii: a multi-scale simulation study

Efficient drug delivery is crucial for the creation of effective pharmaceutical treatments, and polyethylene glycol (PEG) carriers have been emerged as promising candidates for this purpose due to their bio-compatibility, enhancement of drug solubility, and stability. In this study, we utilized molecular simulations to examine the interactions between PEG carriers and selected drug molecules extracted from Celastrus hindsii: Hindsiilactone A, Hindsiiquinoflavan B, Maytenfolone A, and Celasdin B. The simulations provided detailed insights into the binding affinity, stability, and structural properties of these drug molecules when complexed with PEG carriers. A multi-scale approach combining density functional theory (DFT), extended tight-binding (xTB), and molecular dynamics (MD) simulations was conducted to investigate both unbound and bound states of PEG/drug systems. The results from DFT and xTB calculations revealed that the unbound complex has an unfavorable binding free energy, primarily due to negative contributions of delta solvation free energy and entropy. The MD simulations provided more detailed insights into the interactions between PEG and drug molecules in water solutions. By integrating the findings from the multi-scale simulations, a comprehensive picture of the unbound and bound states of PEG and drug systems were obtained. This information is valuable for understanding the molecular mechanisms governing the binding of drugs in PEG-based delivery platforms, and it contributes to the rational design and optimization of these systems.

Method of hyaluronidase immobilization to produce an oral dosage form

Hyaluronidase is an enzyme that helps maintain an optimal balance of hyaluronic acid in connective tissue and ensures full tissue regeneration. Currently, hyaluronidase drugs are used in various fields of medicine. Meanwhile, there are no oral preparations based on hyaluronidase on the pharmaceutical market due to its low bioavailability in this method of administration. One of the options to increase enzyme bioavailability is electron-beam pegylation, which involves obtaining drugs with a modified pharmacokinetic profile in the direction of increasing enteral bioavailability, as well as having additional protection from the action of proteolytic enzymes. Aim of the study was using the electron beam pegylation method to obtain a laboratory batch of a preparation based on highly purified hyaluronidase, which can be further used in the development of an oral drug product. Material and methods. Hyaluronidase, which was isolated from bovine testicular hyaluronidase and polyethylene glycols of different molecular weight, was used in the experimental study. Experiments were carried out using a pulsed linear accelerator ILU-10 for enzyme electron beam immobilization on a water-soluble polymer matrix of polyethylene glycol molecules. The formation of hyaluronidase and polyethylene glycols conjugates was confirmed by exclusion chromatography. Results. As a result of accelerated electron irradiation of hyaluronidase and polyethylene glycol of molecular mass 1500 Da conjugates of enzyme and polymer matrix were formed. After electron-beam pegylation, the specific activity of the enzyme was retained. Conclusions. A laboratory batch of prototype pharmaceutical substance based on immobilised hyaluronidase on polyethylene glycol was obtained.

Polyethylene Glycol Impacts Conformation and Dynamics of Escherichia coli Prolyl-tRNA Synthetase Via Crowding and Confinement Effects.

Polyethylene glycol (PEG) is a flexible, nontoxic polymer commonly used in biological and medical research, and it is generally regarded as biologically inert. PEG molecules of variable sizes are also used as crowding agents to mimic intracellular environments. A recent study with PEG crowders revealed decreased catalytic activity of Escherichia coli prolyl-tRNA synthetase (Ec ProRS), where the smaller molecular weight PEGs had the maximum impact. The molecular mechanism of the crowding effects of PEGs is not clearly understood. PEG may impact protein conformation and dynamics, thus its function. In the present study, the effects of PEG molecules of various molecular weights and concentrations on the conformation and dynamics of Ec ProRS were investigated using a combined experimental and computational approach including intrinsic tryptophan fluorescence spectroscopy, atomic force microscopy, and atomistic molecular dynamic simulations. Results of the present study suggest that lower molecular weight PEGs in the dilute regime have modest effects on the conformational dynamics of Ec ProRS but impact the catalytic function primarily via the excluded volume effect; they form large clusters blocking the active site pocket. In contrast, the larger molecular weight PEGs in dilute to semidilute regimes have a significant impact on the protein's conformational dynamics; they wrap on the protein surface through noncovalent interactions. Thus, lower-molecular-weight PEG molecules impact protein dynamics and function via crowding effects, whereas larger PEGs induce confinement effects. These results have implications for the development of inhibitors for protein targets in a crowded cellular environment.

Nanoscintillator Coating: A Key Parameter That Strongly Impacts Internalization, Biocompatibility, and Therapeutic Efficacy in Pancreatic Cancer Models

Pancreatic cancer is associated with a poor prognosis despite multimodal treatments. To improve the efficacy of radiotherapy, the use of nanoscintillators is emerging. Made of high‐Z elements, they absorb X‐rays more efficiently than tissues and can locally enhance the radiation dose provided they have accumulated near tumor cells. This study focuses on the role of the coating, a key parameter that controls both in vitro and in vivo properties of nanoparticles, including their internalization, biocompatibility, and therapeutic efficacy. Polyethylene glycol and tripolyphosphate molecules are used to coat lanthanum fluoride nanoscintillators, and their properties are evaluated on pancreatic cancer models. The experiments demonstrate a higher internalization of the nanoparticles when coated with tripolyphosphate, in both 2D and 3D culture models, correlating with greater efficacy under X‐rays, which may be associated with higher radiation dose‐enhancement. The nanoparticles are also injected intravenously in healthy or tumor‐bearing mice in order to study their toxicity, pharmacokinetics, and biodistribution. Despite a strong liver and spleen accumulation, especially for the tripolyphosphate‐coated nanoparticles, no toxicity is observed for either coating. Because they show promising radiation dose‐enhancement in vitro in both culture models and a limited toxicity in vivo, polyethylene glycol‐coated nanoparticles are good candidates for biomedical applications.

Prospective effect of linkers type on the anticancer activity of pemetrexed-monoclonal antibody (atezolizumab) conjugates.

Conventional chemotherapy results in severe toxic side effects due to affecting normal and cancer cells. The conjugation of chemotherapy with mAb will improve the chemotherapy selectivity towards cancer cells and at the same time will potentiate immune system to detect and kill cancer cells. The aim of the study was to prepare atezolizumab-pemetrexed conjugate using two types of linkers (linker conjugated with -NH2 of lysine amino acid in the mAb). This study utilizes (for the first time) the mAb atezolizumab (AtZ) to prepare a new, selective conjugate carrier for pemetrexed (PMX) by using gamma amino butyric acid (GABA) as linker for the first time in comparison to the commonly used linker polyethylene glycol (PEG) using carbodiimide (EDC) / N-hydroxysulfosuccinimide (Sulfo-NHS) zero length cross linker. Stepwise evaluation for PMX-linkers linkage as well as mAb conjugates was evaluated by FTIR, 1HNMR, DSC, LC-MS, gel-electrophoresis as well as the anticancer activity against lung cells A549. The work revealed that two molecules of GABA combined with PMX, which in turn conjugated with an average ratio of 4:1 with mAb, while one molecule of PEG combined with PMX, which in turn conjugated with mAb in the same average ratio. The IC 50 for the prepared PMX-GABA-AtZ conjugate was 0.048 µM, which was much lower than PMX alone, antibody AtZ alone as well as PMX-PEG-AtZ conjugate in a dose and time dependent manner. The potential use of such conjugate that selectively directed to the overexpressed lung cells antigen in a low dose leading to reduction of serious side effects of PMX and the cost of therapeutically AtZ mAb used.

Green, recyclable and high latent heat form-stable phase change composites supported by cellulose nanofibers for thermal energy management

Efficiently addressing the challenge of leakage is crucial in the advancement of solid-liquid phase change thermal storage composite materials; however, numerous existing preparation methods often entail complexity and high energy consumption. Herein, a straightforward blending approach was adopted to fabricate stable phase change nanocomposites capitalizing on the interaction between TEMPO-oxidized cellulose nanofibers (TOCNF) and polyethylene glycol (PEG) molecules. By adjusting the ratio of TOCNF to PEG and the molecular weights of PEG, TOCNF/PEG phase change composites (TPCC) with customizable phase transition temperature (40.3–59.1 °C) and high phase transition latent heat (126.3–172.1 J/g) were obtained. The TPCC of high-loaded PEG (80–95 wt%) ensured a leakage rate of less than 1.7 wt% after 100 heating-cooling cycles. Moreover, TPCC exhibits excellent optical properties with a transmittance of over 90 % at room temperature and up to 96 % after heating. The thermal response analysis of TPCC demonstrates exceptional thermal-induced flexibility and good thermal stability, as well as recyclability and reshaping ability. This study may inspire others to design bio-based phase change composites with potential applications in thermal energy storage and management of smart-energy buildings, photothermal response devices, and waste heat-generating electronics.

Effect of a nonionic surfactant and anionic polyelectrolyte binary system on the stability of a calcium and magnesium carbonates dispersion

The effect of sodium polyacrylate, polyethylene glycol of various molecular weights, and their mixtures on the dispersion stability of calcium and magnesium carbonates was studied. It was shown that in the presence of a binary system, the light transmission of the dispersion decreases 1.2–1.5 times, the content of fine fraction particles increases by 1.1–1.3 times compared to the individual components. The stability of the dispersion of carbonates depends on the components ratio in the binary system and their molecular weight. The formation of adsorption solvated layers of polyacrylate and polyethylene glycol molecules at the interphase boundary contributes to an increase in the stability of the carbonate dispersion.

Structure of polyethylene glycol/water mixtures as a separation medium of aqueous two-phase extraction systems studied by equilibrium analysis of thiocyanato complexation of Cobalt(II)

Aqueous two-phase systems (ATPS) utilizing polyethylene glycol (PEG) have been successfully used for the separation of various organic and inorganic compounds as an environmentally benign extraction method. However, a fundamental understanding of the role of the hydration structures around PEG chains in solute partitioning in ATPS remains elusive although it has been considered that PEG molecules are involved in separation. In the present work, the equilibria of Co(II) thiocyanate complexation reaction in aqueous PEG solutions were studied by spectrophotometry with varying ethylene oxide chain length and concentration of PEG. From the formation constants of the tetrahedral and octahedral Co(II) thiocyanate complexes obtained, a microheterogeneous structure consisting of pseudo phases formed by hydration of ethylene oxide (EO) chain and terminal hydroxyl (OH) groups in the PEG molecule in addition to the bulk water phase was estimated. It was revealed that the formation of tetrahedral Co(NCS)42− complex proceeds in the EO pseudo phase by the involvement of hydrophobic ethylene groups, while the OH phase and the bulk phase inhibit the progress of the reaction. This indicates that Co(NCS)42− is stable in hydrophobic hydration structure of water around the EO moiety. The EO phase imparts hydrophobicity to aqueous PEG solutions and plays a predominant role in partition of solute molecules in PEG-based ATPS.

Thermophysical properties of polyethylene glycol oligomers via molecular dynamics simulations.

Polyethylene glycol (PEG) is a versatile chemical with numerous applications in various fields, including biomedical research, pharmaceutical development, and industrial manufacturing. Molecular dynamics (MD) is a powerful tool for investigating the thermophysical properties of PEG molecules. In this study, we employ the General AMBER force field (GAFF) to perform MD simulations on various PEG oligomers, focusing on the calculation of density, self-diffusion coefficients, shear viscosity, and thermal conductivity. The results demonstrate excellent agreement with experimental data, where GAFF outperforms other force fields in reproducing thermophysical properties. For a PEG tetramer, the GAFF force field reproduces experimental data within 5% for the density, 5% for the diffusion coefficient, and 10% for the viscosity. In comparison, the OPLS force field displays significant deviations exceeding 80% for the diffusion coefficient and 400% for the viscosity. A detailed analysis of partial charge distributions and dihedral angles reveals that they significantly impact the structural behavior of PEG oligomers. The findings highlight the GAFF force field as one of the most accurate and reliable options for simulating systems with PEGs.

Color adjustable, mechanically robust, flame-retardant and weather-resistant TiO2/MMT/CNF hierarchical nanocomposite coatings toward intelligent fire cyclic warning and protection

Fire safety and protection are very important but still show a critical global challenge. Developing smart fire warning materials with combined passive flame retardancy and active fire alarm response is promising for reducing or avoiding serious fire disasters. Various nano-fillers (e.g., graphene oxide and MXene) based composite coatings have proven to be effective for monitoring critical fire risk of various combustible materials; however, they still show some shortages, for example, high cost, black color, poor weather resistance and complicated fabricating process. Here, we report a green, cost-effective and large-scale strategy for fabricating water-based 3D-titania/2D-montmorillonite/1D-celluose nanofiber (TiO2/MMT/CNF) hierarchical nanocomposite coatings with adjustable color, mechanical robustness, good flame retardancy, long-term weather resistance and sensitive fire cyclic alarming response. The formation of strong chemical bonding and hydrogen bonding interactions among polyethylene glycol molecules and multi-scale nano-fillers together with silane surface modification can produce good mechanical flexibility (folded crane), surface hydrophobicity (water contact angle of 152°) and exceptional flame resistance (good structure integrity after 120 s flame exposure). Notably, the optimized nanocomposite coatings exhibit ultrafast fire alarm response (<3.5 s) and stable fire cyclic alarming capability via the possible band transition of the TiO2 network under flame. Further, such color-adjustable nanocomposite coatings can be easily fabricated for large-scale production, and they show excellent stable flame retardancy and stable fire cyclic warning response even after more than one-year outdoor exposure. This work provides a promising and green fire-warning nanocomposite coatings with combined passive-active functionalities for fire warning and protection.

Surface Modification of Titanate Nanotubes with a Carboxylic Arm for Further Functionalization Intended to Pharmaceutical Applications.

Nanotechnology is playing a significant role in modern life with tremendous potential and promising results in almost every domain, especially the pharmaceutical one. The impressive performance of nanomaterials is shaping the future of science and revolutionizing the traditional concepts of industry and research. Titanate nanotubes (TNTs) are one of these novel entities that became an appropriate choice to apply in several platforms due to their remarkable properties such as preparation simplicity, high stability, good biocompatibility, affordability and low toxicity. Surface modification of these nanotubes is also promoting their superior characters and contributing more to the enhancement of their performance. In this research work, an attempt was made to functionalize the surface of titanate nanotubes with carboxylic groups to increase their surface reactivity and widen the possibility of bonding different molecules that could not be bonded directly. Three carboxylic acids were investigated (trichloroacetic acid, citric acid and acrylic acid), and the prepared composites were examined using FT-IR and Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and dynamic light scattering (DLS). The toxicity of these functionalized TNTs was also investigated using adherent cancer cell lines and fibroblasts to determine their safety profile and to draw the basic lines for their intended future application. Based on the experimental results, acrylic acid could be the suitable choice for permanent surface modification with multiple carboxylic groups due to its possibility to be polymerized, thus presenting the opportunity to link additional molecules of interest such as polyethylene glycol (PEG) and/or other molecules at the same time.

In Vitro and Preclinical Antitumor Evaluation of Doxorubicin Liposomes Coated with a Cholesterol-Based Trimeric β-D-Glucopyranosyltriazole.

The coating of liposomes with polyethyleneglycol (PEG) has been extensively discussed over the years as a strategy for enhancing the in vivo and in vitro stability of nanostructures, including doxorubicin-loaded liposomes. However, studies have shown some important disadvantages of the PEG molecule as a long-circulation agent, including the immunogenic role of PEG, which limits its clinical use in repeated doses. In this context, hydrophilic molecules as carbohydrates have been proposed as an alternative to coating liposomes. Thus, this work studied the cytotoxicity and preclinical antitumor activity of liposomes coated with a glycosyl triazole glucose (GlcL-DOX) derivative as a potential strategy against breast cancer. The glucose-coating of liposomes enhanced the storage stability compared to PEG-coated liposomes, with the suitable retention of DOX encapsulation. The antitumor activity, using a 4T1 breast cancer mouse model, shows that GlcL-DOX controlled the tumor growth in 58.5% versus 35.3% for PEG-coated liposomes (PegL-DOX). Additionally, in the preliminary analysis of the GlcL-DOX systemic toxicity, the glucose-coating liposomes reduced the body weight loss and hepatotoxicity compared to other DOX-treated groups. Therefore, GlcL-DOX could be a promising alternative for treating breast tumors. Further studies are required to elucidate the complete GlcL-DOX safety profile.

Impact of polyethylene glycol molar mass and structural isomer of alcohol on the solubility and dissolution enhancement of mesalazine

This work reports the solubility of mesalazine (5-ASA) in mole fraction terms (x1,T) in mono-solvents of polyethylene glycol (PEG) 400, 1-propanol and 2-propanol along with their binary mixtures in different mass fractions of PEG 400 at 293.15–313.15 K and atmospheric pressure which measured experimentally by a shake-flask technique. The solubility of 5-ASA in these mixtures not only enhances with enhancing temperature, but also raises with raising PEG's mass fraction. Effect of PEG molar mass on the solubility of 5-ASA was also estimated by measuring its solubility in PEG 200 or 600 + 1- or 2-propanol mixtures at 298.15 K. Upon the same temperature and mass fraction of PEGs, the upward trend of 5-ASA mole fractions was: PEG 600 + 1-propanol > PEG 600 + 2-propanol > PEG 400 + 1-propanol > PEG 400 + 2-propanol > PEG 200 + 1-propanol > PEG 200 + 2-propanol indicating, the binary mixtures containing a high molar mass of PEG and 1-propanol with a hydroxyl group attached to carbon number 1 had a more solubilization power. Then, the experimental mole fractions were modelled by some cosolvency and activity coefficient models, and the model parameters were regressed. The back-computed mole fractions of 5-ASA by cosolvency models presented a better agreement with the experimental data than that of activity models and Jouyban-Acree model had the best performance (low overall average percentage deviation of 6.1 %). By means of enthalpy-entropy compensation analysis, non-linear ΔsolH° against ΔsolG° compensation plots with positive and negative slopes were achieved as a consequent of increasing 5-ASA solvation by PEG molecules and the solvent-structure loosing, respectively.

Macromolecular crowding potently stimulates DNA supercoiling activity of Mycobacterium tuberculosis DNA gyrase

Macromolecular crowding, manifested by high concentrations of proteins and nucleic acids in living cells, significantly influences biological processes such as enzymatic reactions. Studying these reactions in vitro, using agents such as polyethylene glycols (PEGs) and polyvinyl alcohols (PVAs) to mimic intracellular crowding conditions, is essential due to the notable differences from enzyme behaviors observed in diluted aqueous solutions. In this article, we studied Mycobacterium tuberculosis (Mtb) DNA gyrase under macromolecular crowding conditions by incorporating PEGs and PVAs into the DNA supercoiling reactions. We discovered that high concentrations of potassium glutamate, glycine betaine, PEGs, and PVA substantially stimulated the DNA supercoiling activity of Mtb DNA gyrase. Steady-state kinetic studies showed that glycine betaine and PEG400 significantly reduced the KM of Mtb DNA gyrase, and simultaneously increased the Vmax or kcat of Mtb DNA gyrase for ATP and the plasmid DNA molecule. Molecular dynamics simulation studies demonstrated that PEG molecules kept the ATP lid of GyrB in a closed or semi-closed conformation, which prevented ATP molecules from leaving the ATP-binding pocket of GyrB. The stimulation of the DNA supercoiling activity of Mtb DNA gyrase by these molecular crowding agents likely results from a decrease in water activity and an increase in excluded volume.

A Simple and Versatile Strategy for Oriented Immobilization of His-Tagged Proteins on Magnetic Nanoparticles.

Oriented and covalent immobilization of proteins on magnetic nanoparticles (MNPs) is particularly challenging as it requires both the functionality of the protein and the colloidal stability of the MNPs to be preserved. Here, we describe a simple, straightforward, and efficient strategy for MNP functionalization with proteins using metal affinity binding. Our method involves a single-step process where MNPs are functionalized using a preformed, ready-to-use nitrilotriacetic acid-divalent metal cation (NTA-M2+) complex and polyethylene glycol (PEG) molecules. As a proof-of-concept, we demonstrate the oriented immobilization of a recombinant cadherin fragment engineered with a hexahistidine tag (6His-tag) onto the MNPs. Our developed methodology is simple and direct, enabling the oriented bioconjugation of His-tagged cadherins to MNPs while preserving protein functionality and the colloidal stability of the MNPs, and could be extended to other proteins expressing a polyhistidine tag. When compared to the traditional method where NTA is first conjugated to the MNPs and afterward free metal ions are added to form the complex, this novel strategy results in a higher functionalization efficiency while avoiding MNP aggregation. Additionally, our method allows for covalent bonding of the cadherin fragments to the MNP surface while preserving functionality, making it highly versatile. Finally, our strategy not only ensures the correct orientation of the protein fragments on the MNPs but also allows for the precise control of their density. This feature enables the selective targeting of E-cadherin-expressing cells only when MNPs are decorated with a high density of cadherin fragments.