Pyrene Probe Research Articles

N-Perfluorooctane versus n-Octane: Pyrene Fluorescence to Compare and Contrast Solute Solvation.

Fluorous solvents may offer distinctly different solvation environments to a solute compared to their hydrocarbon analogues due to the inherently high electronegativity associated with fluorine. Solute solvation within n-perfluorooctane (PFO) is compared with that in n-octane using the well-established polycyclic aromatic hydrocarbon (PAH) fluorescence probe pyrene in the temperature range of 288 to 318 K. Both density (ρ) and dynamic viscosity (η) of PFO are considerably higher than those of n-octane. UV-vis molecular absorbance, fluorescence emission/excitation, and excited-state emission intensity decay reveal the cybotactic region of pyrene to be more nonpolar in PFO than that in n-octane. Bimolecular quenching rate constants (kq) for the pyrene-nitrobenzene fluorophore-quencher pair adhere to the Stokes-Einstein formulation; however, they are considerably higher than the estimated rate constants for the diffusion-controlled process (kdiff). This is due to the high electron affinity of nitrobenzene leading to aromatic π-π interactions between pyrene and nitrobenzene. For a nonaromatic low electron affinity quencher, such as nitromethane, while kq < kdiff in n-octane, kq > kdiff in PFO. This is due to the fact that highly electronegative fluorines on PFO stabilize the partial positive charge (δ+) that develops on excited pyrene during electron/charge transfer to the quencher nitromethane, facilitating quenching in the process. Exciplex formation between pyrene and triethylamine (TEA) is more favored in PFO as opposed to n-octane although ηPFO > ηn-octane. The developing charge on the exciplex is stabilized by the electronegative fluorines of the PFO. The pyrene-TEA exciplex appears to form exclusively in the excited state of pyrene, and the kinetics of exciplex formation is in the subnanosecond regime. On the contrary, the efficiency of exciplex formation between pyrene and N,N-dimethylaniline (DMA) is comparable in PFO and n-octane, and the kinetics is slower in comparison to that of the pyrene-TEA exciplex. Certain ground-state heterogeneity is detected for the pyrene-DMA system in PFO due to the low solubilizing ability of the fluorous solvent. Highly electronegative fluorines on perfluorohydrocarbon solvents are found to offer unusual and unique solvation characteristics.

Structuring of sodium tungstate with sodium dodecyl sulphate in aqueous media and its implications for advanced materials development

This article explores the structuring sodium tungstate with sodium dodecyl sulphate (SDS) in water and characterizing the resulting products post-destabilization with hydrochloric acid and calcination. Utilizing nuclear magnetic resonance (NMR), small-angle X-ray scattering (SAXS), fluorescence spectroscopy with a pyrene probe, conductivity, and pH analyses, the study elucidates the system's structure and interactions. SDS serves as a structuring agent for tungstate anions in water, with sulphate anions interacting with tungsten d-orbitals. The presence of SDS significantly influences final structures after calcination. Higher precursor/structuring agent ratios result in higher proportion of tungsten oxide, alongside Na2W2O7 and Na2W4O13. Varying calcination temperatures yield different crystal structures and morphologies, including flower petals and roses at 500 °C and nanorods at 700 °C. These findings shed light on material structuring processes. The obtained materials exhibit to utilize solar radiation for chemical reactions.

A study of hydrophobic domain formation of polymeric drug precipitation inhibitors in aqueous solution

Despite the widespread use of polymers as precipitation inhibitors in supersaturating drug formulations, the current understanding of their mechanisms of action is still incomplete. Specifically, the role of hydrophobic drug interactions with polymers by considering possible supramolecular conformations in aqueous dispersion is an interesting topic. Accordingly, this study investigated the tendency of polymers to create hydrophobic domains, where lipophilic compounds may nest to support drug solubilisation and supersaturation. Fluorescence spectroscopy with the environment-sensitive probe pyrene was compared with atomistic molecular dynamics simulations of the model drug fenofibrate (FENO). Subsequently, kinetic drug supersaturation and thermodynamic solubility experiments were conducted. As a result, the different polymers showed hydrophobic domain formation to a varying degree and the molecular simulations supported interpretation of fluorescence spectroscopy data. Molecular insights were gained into the conformational structure of how the polymers interacted with FENO in solution phase, which apart from nucleation and crystal growth effects, determined drug concentrations in solution. Notable was that even at the lowest polymer concentration of 0.01 %, w/v, there were polymer-specific solubilisation effects of FENO observed and the resulting reduction in apparent drug supersaturation provided relevant knowledge both from a mechanistic and practical perspective.

Development of Cholinium-Based API Ionic Liquids with Enhanced Drug Solubility: Biological Evaluation and Interfacial Properties.

We report an efficient sustainable two-step anion exchange synthetic procedure for the preparation of choline API ionic liquids (Cho-API-ILs) that contain active pharmaceutical ingredients (APIs) as anions combined with choline-based cations. We have evaluated the in vitro cytotoxicity for the synthesized compounds using three different cells lines, namely, HEK293 (normal kidney cell line), SW480, and HCT 116 (colon carcinoma cells). The solubility of APIs and Cho-API-ILs was evaluated in water/buffer solutions and was found higher for Cho-API-ILs. Further, we have investigated the antimicrobial potential of the pure APIs, ILs, and Cho-API-ILs against clinically relevant microorganisms, and the results demonstrated the promise of Cho-API-ILs as potent antimicrobial agents to treat bacterial infections. Moreover, the aggregation and adsorption properties of the Cho-API-ILs were observed by using a surface tension technique. The aggregation behavior of these Cho-API-ILs was further supported by conductivity and pyrene probe fluorescence. The thermodynamics of aggregation for Cho-API-ILs has been assessed from the temperature dependence of surface tension. The micellar size and their stability have been studied by dynamic light scattering, transmission electron microscopy, and zeta potential. Therefore, the duality in the nature of Cho-API-ILs has been explored with the upgradation of their physical, chemical, and biopharmaceutical properties, which enhance the opportunities for advances in pharmaceutical sciences.

Ratiometric room-temperature phosphorescence platform for visual and spectral analysis of naphthalene

Host-guest doping room-temperature phosphorescence (RTP) materials have showed excellent potential for ultra-sensitive detection due to its bright luminescence in presence of trace guests. However, the inherent signal fluctuation of solid-state sensors restricts their widespread applications. Herein we constructed a simple internal standard method to overcome the signal fluctuation problem in RTP spectral analysis. Ultralong organic RTP can be obtained by using 1,4-dichlorobenzene (DCB) as a host and trace gaseous NL as a guest through the host-guest doping strategy. In this study, a dual-emission ratiometric phosphorescent probe pyrene (Py)/pentachloropyridine (PCP)-DCB was constructed by using the Py/PCP system fabricated via melt-casting as the reference afterglow and using the DCB as the stimuli-responsive unit of gaseous NL. This probe can be used for visual identification and content detection of NL in commercial mothballs. The ratio of phosphorescence intensity (I485/I595) was linearly related to the mass of added NL (mNL) within the range of 0.05–1.45 mg in this ratiometric RTP platform, and had a low detection limit of 0.012 mg. Furthermore, the NL content of five commercially available mothballs with different NL content was detected by this Py/PCP-DCB platform, and it had good performance compared to the gas chromatography (GC) analysis results.

Experimental Investigation of Cationic Gemini Surfactants: Self‐Assembly, Corrosion Inhibition, Foaming and Dye Solubilization Properties

AbstractIn this study, two cationic gemini surfactants 12‐3‐12 and 12‐3(OH)‐12 were synthesized in our labrotory. The critical micelle concentration (CMC) values of synthesized surfactants were determined by conductivity measurements. The aggregation number (Nagg) of micelles was calculated using the pyrene probe fluorescence method. It was been investigated the corrosion effect of cationic gemini surfactants were denoted as 12‐3‐12 and 12‐3(OH)‐12 for carbon steel in 1 M HCl. The inhibition effect was investigated using weight loss, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP) and scanning electron microscopy (SEM) techniques. It has been determined that both surfactants showed the best inhibitory effect at low concentrations. The foaming capacity (FC) and the foam stability (FS) of gemini surfactants were studied by measuring the foam volume for 0.5 % (w/v) surfactant solutions and it was observed that the foaming properties of 12‐3(OH)‐12 gemini surfactant were better. The solubility capability of both surfactants was tested with the water‐insoluble dye Sudan Red B and it was observed that the solubility increased significantly over the CMC value of the cationic gemini surfactants. Finally, the corrosion effect, foam capacity and foam stability and effects on paint solubility of the synthesized surfactants were obtained at very low concentrations.

Intramolecular dimer formation reveals anomalous solvation within fluorous solvent perfluorodecalin.

Due to the unusual properties of fluorine, a fluorous solvent obtained by replacing hydrogen atoms with fluorine atoms in a hydrocarbon solvent may afford unusual solute solvation and aggregation. A fluorescent dipyrenyl probe, 1,3-bis(1-pyrenyl)propane (BPP), was utilized to explore intramolecular aggregation within perfluorodecalin (PFD), a prototypical fluorous solvent. Steady-state fluorescence emission and excitation along with excited-state emission intensity decay of BPP were acquired in the temperature range of 293.15 to 333.15 K in fluorous solvent PFD and n-hexane-added PFD. The probe BPP is known to form an intramolecular excimer in common hydrocarbon solvents, which is characterized by a broad structureless low-energy emission band; the formation of intramolecular excimers exclusively in the excited state was confirmed via excitation scans along with the intensity decay of the monomer and excimer, respectively. While intramolecular dimerization of BPP does occur in PFD, emission wavelength-dependent excitation spectra and fits of the intensity decay data reveal that intramolecular aggregation takes place in the ground state as well. This ground-state heterogeneity is reduced as the temperature is increased. In the presence of as small as 0.1 mole fraction of n-hexane, the ground-state aggregation vanishes, and intramolecular dimerization again takes place exclusively in the excited state. The data hint at the poor solvation of BPP in PFD to be responsible for intramolecular ground-state aggregation. In PFD-rich (PFD + n-hexane) mixtures, probe pyrene (Py) was found to be preferentially solvated by n-hexane, further corroborating the above-mentioned proposition. Clear differences in solute solvation within a fluorous solvent as compared to hydrocarbon solvents leading to unexpected solubilization and aggregation in fluorous media are amply demonstrated.

ИНТЕНСИВНОСТЬ СВОБОДНО-РАДИКАЛЬНЫХ ПРОЦЕССОВ И СТРУКТУРНО-ДИНАМИЧЕСКИЕ ПА-РАМЕТРЫ МЕМБРАН ЭРИТРОЦИТОВ БОЛЬНЫХ САХАРНЫМ ДИАБЕТОМ 2 ТИПА

The World Health Organization has recognized diabetes mellitus (DM) as one of the four major noncommunicable diseases that lead to early disability and mortality among the population. Oxidative stress, which contributes to the intensification of free radical processes (FRP), can be considered as a universal nonspecific mechanism of DM2 pathogenesis. De-spite numerous studies, questions about the mechanisms of development of oxidative stress and its influence on the physicochemical state of biological membranes still remain open. The aim of this work is to study the intensity of free radical processes and the structural and dynamic characteristics of blood erythrocyte membranes in patients with type 2 diabetes mellitus (DM2). The study included male patients with type 2 diabetes aged 55 to 70 years who did not have other acute and chronic diseases in the acute stage. The content of glucose, glycated hemoglobin, markers of oxidative stress (MDA and carbonyl groups) was determined in the blood of patients. The structural and dynamic parameters of erythrocyte membranes were determined using fluorescent probe pyrene. It was found that an increase in blood glucose levels in patients with DM2 increases the content of markers of lipid peroxidation (MDA) and oxidative modification of proteins (carbonyl groups). Oxidative damage to lipids and proteins of erythrocyte membranes in decompensated DM2 changes their structural and dynamic properties: they increase the microviscosity of the lipid bilayer and the polarity of its phospholipids, and promote conformational rearrangements in membrane proteins. Close correlations were found between the level of glucose, the content of CRP products in the blood, and the structural and dynamic parameters of erythrocyte membrane

Calix[4]arene Polyamine Triazoles: Synthesis, Aggregation and DNA Binding

Artificial gene delivery systems are in great demand from both scientific and practical biomedical points of view. In this paper, we present the synthesis of a new click chemistry calix[4]arene precursor with free lower rim and new water-soluble calixarene triazoles with 12 amino-groups on the upper rim (one with free phenol hydroxyl groups and two another containing four butyl or tetradecyl fragments). Aggregation in the series of amino-triazole calixarenes of different lipophilicity (calixarene with free phenol hydroxyl groups or butyl and tetradecyl fragments on the lower rim) was studied using dynamic light scattering and fluorescent pyrene probe. It was found that calix[4]arene with a free lower rim, like alkyl-substituted butyl calix[4]arene, forms stable submicron aggregates 150-200 nm in size, while the more lipophilic tetradecyl -substituted calix[4]arene forms micellar aggregates19 nm in size. Using UV-Vis spectroscopy, fluorimetry and CD, it was shown that amino-triazole calix[4]arenes bind to calf thymus DNA by classical intercalation. According to DLS and TEM data, all studied macrocycles cause significant DNA compaction, forming stable nanoparticles 50-20 nm in size. Among all studied calix[4]arenes the most lipophilic tetradecyl one proved to be the best for both binding and compaction of DNA.

Fluorescence Detection of Endotoxin Using Cadmium Complexed with Dipicolylamine-type Pyrene Probe

Fluorescence Detection of Endotoxin Using Cadmium Complexed with Dipicolylamine-type Pyrene Probe

Solvatochromic fluorescent styryl pyrene probes for the quantitative determination of water content in organic solvents

A series of D-π-A fluorescent styryl pyrene probes were synthesized through the Wittig reaction. The introduction of an electron-withdrawing substituent on the phenyl ring creates a push-pull system that shows solvent-dependent intramolecular charge transfer (ICT) and solvatochromic properties. Among these, the styryl pyrene probes with nitro (Py-NO2) and aldehyde (Py-CHO) substituents exhibited remarkable sensitivity to environment polarity. They show remarkable fluorescence changes from green to red, and blue to orange in nonpolar to polar organic solvents, respectively. The results were explained by the Lippert-Mataga and ET(30) models, which were supported by theoretical calculations by the density functional theory (DFT). Importantly, the fluorescence emission of Py-NO2 in organic solvents is sensitive to the presence of water in the range of 0–34.2% (v/v) in THF, 0–9.1% (v/v) in DMF, and 0–39.7% (v/v) in CH3CN. The limits of detection of water were established as low as 0.007%, 0.033%, and 0.036% (v/v) in THF, DMF, and CH3CN, respectively. Py-CHO showed somewhat higher limits of detection than Py-NO2 for the same solvents but exhibited a broad linear response to water content in EtOH between 3.3 and 63.6% (v/v) water content with the limit of detection at 2.350% (v/v). Thus, it is possibly useful as a sensor for the wide range detection of alcohol content in beverages. These push-pull styryl pyrene probes not only served as a new supersensitive fluorescent sensor for the quantitative detection of low to medium-level water content in organic solvents but may also be useful in a broad range of applications.

MICELLIZATION BEHAVIOUR OF CONVENTIONAL (SDS AND DTAB) AND SYNTHESIZED GEMINI SURFACTANT (12-2-12) IN AQUEOUS SOLUTIONS OF METFORMIN HYDROCHLORIDE AT VARYING TEMPERATURES: A COMPARATIVE STUDY

The micellar properties of two common surfactants, namely sodiumdodecyl sulphate (SDS) which is of anionic character and dodecyltriamonium bromide (DTAB) of cationic type alongwith 12-2-12 gemini surfactant which was produced in aqueous solutions of 0.001, 0.005 and 0.01 mol∙kg-1 aqueous solutions of metformin hydrochloride (Mfm-HCl) (antidiabetic drug) at 25, 35 and 45 degree Celsius has been analyzed through conductometry. The obtained conductivity data has been used to determine one of the most important characteristic of surfactants known critical micelle concentration (CMC); the concentration above which micelles are formed. The variation in CMC with content of metformin hydrochloride has been compensated in terms of hydrophobic interactions. The drug has been found to diminish the CMC of both types of surfactants (conventional and synthesized). In terms of the hydrophilic/hydrophobic interactions existing in the system, the effect of temperature on the micellization behaviour of these discussed surfactants has also been studied. Moreover, energetics of micellization has also been discussed by using phsedo-phase separation model for all the studied systems in terms of thermodynamic parameters viz. standard enthalpy, free energy, and entropy, of micellization and viewed in terms of different interactions that may exist in the system. The influence on the micro polarity of micellar environment has been discussed by pyrene probe fluorescence technique and used to determine CMC which has been discovered to have a strong resemblance to conductivity studies.

Impact of Hydroxypropyl Methylcellulose Acetate Succinate Critical Aggregation Concentration on Celecoxib Supersaturation.

Polymers play an important role in amorphous solid dispersions (ASDs), enhancing stability in the solid state and maintaining supersaturation in aqueous solutions of intrinsically low-water-soluble drug candidates. Hydroxypropyl methylcellulose acetate succinate (HPMCAS) is widely used in ASDs due to its hydrophobic/hydrophilic balance and ionizability of the substituent functionalities. While colloid formation of HPMCAS in solution due to this hydrophobic/hydrophilic balance has been studied, the impact of the polymer conformation (random coil vs aggregated) on drug supersaturation of ASDs is not well understood. To our knowledge, this is the first report where the critical aggregation concentration for three grades of HPMCAS (HF/MF/LF) has been determined via fluorescence spectroscopy using the environment-sensitive probe pyrene. The specific impact of polymer conformation (random coil vs aggregate) on the model drug celecoxib (CLX) has been elucidated with fluorescence quenching and nuclear magnetic resonance (NMR) spectroscopy. A negative deviation of the Stern-Volmer plot indicated that aggregated HPMCAS effectively blocked the quencher's access to CLX. This is further supported by NMR observations, where NMR spectra indicate a larger change of chemical shift of the -NH group of CLX when HPMCAS is above its aggregated concentration, suggesting strong H-bonding interactions between aggregated HPMCAS and CLX. Finally, the supersaturation-precipitation study shows that all three grades of HPMCAS in the aggregated state significantly enhanced CLX supersaturation compared to the nonaggregated state, indicating that polymer aggregation plays a critical role in maintaining drug supersaturation.

Alkyne-Palladium(II)-Catalyzed Living Polymerization of Isocyanides: An Exploration of Diverse Structures and Functions.

Inspired by the perfect helical structures and the resulting exquisite functions of biomacromolecules, helical polymers have attracted increasing attention in recent years. Polyisocyanide is well known for its distinctive rodlike helical structure and various applications in chiral recognition, enantiomer separation, circularly polarized luminescence, liquid crystallization, and other fields. Although various methods and catalysts for isocyanide polymerization have been reported, the precise synthesis of helical polyisocyanides with controlled molecular weight, low dispersity, and high tacticity remains a formidable challenge. Owing to a limited synthesis strategy, the controlled synthesis of topological polyisocyanides has barely been realized. This Accounts highlights our recent endeavors to explore novel catalysts for the living polymerization of isocyanides. Fortunately, we discovered that alkyne-Pd(II) catalysts could initiate the living polymerization of isocyanides, resulting in helical polyisocyanides with controlled structures, high tacticity, and tunable compositions. These catalysts are applicable to various isocyanide monomers, including alkyl isocyanides, aryl isocyanides, and diisocyanobenzene derivatives. Incorporating chiral bidentate phosphine ligands onto alkyne-Pd(II) complexes formed chiral Pd(II) catalysts, which promoted the asymmetric living polymerization of achiral isocyanide, yielding single left- and right-handed helices with highly optical activities.Using alkyne-Pd(II) catalysts, various topological polyisocyanides have been facilely prepared, including hybrid block copolymers, bottlebrush polymers, core cross-linked star polymers, and organic/inorganic nanoparticles. For instance, various hybrid block polyisocyanides were easily produced by coupling alkyne-Pd(II)-catalyzed living isocyanide polymerization with controlled radical polymerization and ring-opening polymerization (ROP). Combining the ring-opening metathesis polymerization (ROMP) of norbornene with Pd(II)-catalyzed isocyanide polymerization, bottlebrush polyisocyanides and core cross-linked star polymers were easily prepared. Pd(II)-catalyzed living polymerization of poly(lactic acid)s with isocyanide termini resulted in densely grafted bottlebrush polyisocyanides with closely packed side chains. Moreover, the surface-initiated living polymerization of isocyanides produced a family of polyisocyanide-grafted organic/inorganic hybrid nanoparticles using nanoparticles with alkyne-Pd(II) catalysts anchored on the surfaces. Surprisingly, the nanoparticles and star polymers with helical polyisocyanide arms performed exceptionally well in terms of chiral recognition and resolution. Incorporated organocatalysts such as proline and prolinol units onto the pendants of optically active helical polyisocyanides, a family of polymer-based chiral organocatalysts, were generated, which showed significantly improved stereoselectivity for the asymmetric Aldol reaction and Michael addition and can be easily recycled.Using a chiral alkyne-Pd(II) catalyst, single-handed helical polyisocyanides bearing naphthalene and pyrene probes were produced from achiral isocyanide monomers. These polymers showed excellent self-sorting properties as revealed using a fluorescence resonance energy transfer (FRET) investigation and were self-assembled into two-dimensional (2D) smectic nanostructures driven by both helicity and chain length. Incorporating helical poly(phenyl isocyanide) (PPI) onto semiconducting poly(3-hexylthiophene) (P3HT) induced the asymmetric assembly of the resulting P3HT-b-PPI copolymers into single-handed cylindrical micelles with controlled dimensions and tunable photoluminescence.

Plant Sterol Clustering Correlates with Membrane Microdomains as Revealed by Optical and Computational Microscopy.

Local inhomogeneities in lipid composition play a crucial role in the regulation of signal transduction and membrane traffic. This is particularly the case for plant plasma membrane, which is enriched in specific lipids, such as free and conjugated forms of phytosterols and typical phytosphingolipids. Nevertheless, most evidence for microdomains in cells remains indirect, and the nature of membrane inhomogeneities has been difficult to characterize. We used a new push–pull pyrene probe and fluorescence lifetime imaging microscopy (FLIM) combined with all-atom multiscale molecular dynamics simulations to provide a detailed view on the interaction between phospholipids and phytosterol and the effect of modulating cellular phytosterols on membrane-associated microdomains and phase separation formation. Our understanding of the organization principles of biomembranes is limited mainly by the challenge to measure distributions and interactions of lipids and proteins within the complex environment of living cells. Comparing phospholipids/phytosterol compositions typical of liquid-disordered (Ld) and liquid-ordered (Lo) domains, we furthermore show that phytosterols play crucial roles in membrane homeostasis. The simulation work highlights how state-of-the-art modeling alleviates some of the prior concerns and how unrefuted discoveries can be made through a computational microscope. Altogether, our results support the role of phytosterols in the lateral structuring of the PM of plant cells and suggest that they are key compounds for the formation of plant PM microdomains and the lipid-ordered phase.

Schiff Base Functionalized 1,2,4-Triazole and Pyrene Derivative for Selective and Sensitive Detection of Cu2+ionin the Mixed Organic- Aqueous Media.

We have prepared Schiff base functionalized 1,2,4-triazole and pyrene derivative for selective, sensitive, and naked eye colorimetric detection of Cu2+ in the mixed organic- aqueous media. Amongst the 18 different metal ions studied for absorption and fluorescence titration, only Cu2+ ion encourages the modification in spectral properties of Schiff base functionalized 1,2,4-Triazole and Pyrene Probe. The stoichiometric ratio of the TP-Cu2+ complex was determined to be 2:1 according to Job's plot. The lower detection limit estimated for Cu2+ is 0.234nM which shows excellent sensitivity and selectivity of the present analytical method towards detection of Cu2+ ion in the mixed organic-aqueous media. The present approach has been successfully utilized for the quantitative determination of Cu2+ ion from environmental aqueous solution.

Physicochemical study of dietary fiber methylcellulose and human intestinal bile salt micellar aggregates

The cellulose ether and bile salt mixed systems have a potential to alter the lipid digestion. The basic understanding of the aggregation process, interaction, and physicochemical properties of cellulose ether and bile salt is an essential topic of study. In this work, the interaction between simple dietary fiber methylcellulose (MC) and bile salt sodium deoxycholate (NaDC) has been studied using UV-Vis absorption, steady-state fluorescence intensity, fluorescence quenching, conductivity, light scattering, and zeta potential measurements. Fluorescence properties of hydrophobic probe pyrene were used to find the critical aggregation concentration (CAC), critical micellar concentration (CMC), and aggregation number (Nagg) of the MC/NaDC system. Using conventional conductivity method CAC, CMC, and thermodynamic parameters of micellization i.e. standard Gibbs free energy (∆Gmic0), standard entropy (∆Smic0), and standard enthalpy (∆Hmic0), was calculated to know the information regarding the nature of micellization of MC/NaDC mixed system. The size distribution and zeta potential study give an insight into MC/NaDC interaction before and after the CAC point. The strong hydrophobic interaction between cellulose ether MC and bile salt NaDC shows that this mixed system may have further implications in lipid digestion.

Exchange Counterion in Polycationic Hydrogels: Tunability of Hydrophobicity, Water State, and Floating Capability for a Floating pH Device.

Smart gel materials are capable of controlling and switching swelling, water state, and wettability properties triggered by external stimuli. In this study, we fabricated a series of polyelectrolyte hydrogels bearing a 3-trimethylammoniumpropyl pendant to a methacrylamide-based backbone and examined the switchability with hydrophobic-like counteranions. The exchange between the initial chloride and camphor sulfate (CaS), dodecyl sulfate (DS), and perfluorooctanoate (PFO) counterions was investigated. The kinetics of the exchange showed that the fast exchange (within 4 h) of PFO allowed for a favorable coordination for ion pairing, resulting in a decrease in hydration. The reversibility of the exchange to the Cl− ion was only enabled for the CaS ion due to its bulkiness, while the PFO and DS hydrogels were unable to exchange, even by using tetrabutylammonium chloride, which is a structurally similar reagent, due to aggregation or the coagulates in the collapsed state of the linear tails of the counterions. The hydrogels exhibited a modulable water state and water swelling. Moreover, the hydrogels containing DS and PFO, as counterions, showed surface hydrophobic (contact angle 90°) and high hydrophobic (110°) behavior, respectively. The Raman spectrometry fluorescence with a pyrene probe indicated an increase in strong hydrogen-bonded water molecules, water confinement, and hydrophobic domains in the PFO hydrogel. Moreover, the PFO-modified hydrogel demonstrated a free-floating ability on the water surface, with a strong water repellency, showing that it has the potential to be applied in a floating pH detection device to distinguish between volatile and nonvolatile bases in a controlled manner.

A light-switching pyrene probe to detect phase-separated biomolecules

SummaryBiomolecules may undergo liquid–liquid phase separation (LLPS) to spatiotemporally compartmentalize and regulate diverse biological processes. Because the number of tools to directly probe LLPS is limited (ie. FRAP, FRET, fluorescence microscopy, fluorescence anisotropy, circular dichroism, etc.), the physicochemical traits of phase-separated condensates remain largely elusive. Here, we introduce a light-switching dipyrene probe (Pyr-A) that forms monomers in either hydrophobic or viscous environments, and intramolecular excimers in aqueous solutions. By exploiting their distinct fluorescence emission spectra, we used fluorescent microscopic imaging to study phase-separated condensates formed by in vitro protein droplets and membraneless intracellular organelles (centrosomes). Ratiometric measurement of excimer and monomer fluorescence intensities showed that protein droplets became hydrophobic and viscous as their size increased. Moreover, centrosomes became hydrophobic and viscous during maturation. Our results show that Pyr-A is a valuable tool to characterize LLPS and enhance our understanding of phase separation underlying biological functions.

New Two-Component Pyrene Probes Based on Oligo(2'-O-Methylribonucleotides) for microRNA Detection

New Two-Component Pyrene Probes Based on Oligo(2'-O-Methylribonucleotides) for microRNA Detection