Hydrophobic Area Research Articles

Surface patches induce nonspecific binding and phase separation of antibodies

Nonspecific interactions are a key challenge in the successful development of therapeutic antibodies. The tendency for nonspecific binding of antibodies is often difficult to reduce by rational design, and instead, it is necessary to rely on comprehensive screening campaigns. To address this issue, we performed a systematic analysis of the impact of surface patch properties on antibody nonspecificity using a designer antibody library as a model system and single-stranded DNA as a nonspecificity ligand. Using an in-solution microfluidic approach, we find that the antibodies tested bind to single-stranded DNA with affinities as high as KD = 1 µM. We show that DNA binding is driven primarily by a hydrophobic patch in the complementarity-determining regions. By quantifying the surface patches across the library, the nonspecific binding affinity is shown to correlate with a trade-off between the hydrophobic and total charged patch areas. Moreover, we show that a change in formulation conditions at low ionic strengths leads to DNA-induced antibody phase separation as a manifestation of nonspecific binding at low micromolar antibody concentrations. We highlight that phase separation is driven by a cooperative electrostatic network assembly mechanism of antibodies with DNA, which correlates with a balance between positive and negative charged patches. Importantly, our study demonstrates that both nonspecific binding and phase separation are controlled by the size of the surface patches. Taken together, these findings highlight the importance of surface patches and their role in conferring antibody nonspecificity and its macroscopic manifestation in phase separation.

Antiviral Mechanisms of N-Phenyl Benzamides on Coxsackie Virus A9.

Enteroviruses are one of the most abundant groups of viruses infecting humans, and yet there are no approved antivirals against them. To find effective antiviral compounds against enterovirus B group viruses, an in-house chemical library was screened. The most effective compounds against Coxsackieviruses B3 (CVB3) and A9 (CVA9) were CL212 and CL213, two N-phenyl benzamides. Both compounds were more effective against CVA9 and CL213 gave a better EC50 value of 1 µM with high a specificity index of 140. Both drugs were most effective when incubated directly with viruses suggesting that they mainly bound to the virions. A real-time uncoating assay showed that the compounds stabilized the virions and radioactive sucrose gradient as well as TEM confirmed that the viruses stayed intact. A docking assay, taking into account larger areas around the 2-and 3-fold axes of CVA9 and CVB3, suggested that the hydrophobic pocket gives the strongest binding to CVA9 but revealed another binding site around the 3-fold axis which could contribute to the binding of the compounds. Together, our data support a direct antiviral mechanism against the virus capsid and suggest that the compounds bind to the hydrophobic pocket and 3-fold axis area resulting in the stabilization of the virion.

Polyhydroxybutyrate (PHB) in nanoparticulate form improves physical and biological performance of scaffolds

Polyhydroxyalkanoates (PHAs) are natural polyesters produced by microorganisms as a source of intracellular energy reserves. Due to their desirable material characteristics, these polymers have been thoroughly investigated for tissue engineering and drug delivery applications. A tissue engineering scaffold serves as a substitute of the native extracellular matrix (ECM) and plays a crucial role in tissue regeneration by providing temporary support for cells during natural ECM formation. In this study, porous, biodegradable scaffolds were prepared using native polyhydroxybutyrate (PHB) and PHB in nanoparticulate form using salt leaching method, to investigate the differences in the physicochemical properties such as crystallinity, hydrophobicity, surface morphology, roughness, and surface area and biological properties of the prepared scaffolds. As per the BET analysis, PHB nanoparticles-based (PHBN) scaffolds presented a significant difference in the surface area as compare to PHB scaffolds. PHBN scaffolds showed decreased crystallinity and improved mechanical strength as compared to PHB scaffolds. Thermogravimetry analysis shows delayed degradation of PHBN scaffolds. An examination of Vero cell lines' cell viability and adhesion over time revealed enhanced performance of PHBN scaffolds. Our research suggests that scaffold made of PHB nanoparticles could serve as a superior material for tissue engineering applications than its native form.

Whey Protein Isolate-Mesona chinensis Polysaccharide Conjugate: Characterization and Its Applications in O/W Emulsions.

Mesona chinensis polysaccharide (MCP), a common thickener, stabilizer and gelling agent in food and pharmaceuticals, also has antioxidant, immunomodulatory and hypoglycemic properties. Whey protein isolate (WPI)-MCP conjugate was prepared and used as a stabilizer for O/W emulsion in this study. FT-IR and surface hydrophobicity results showed there could exist interactions between -COO- in MCP and -NH3+ in WPI, and hydrogen bonding may be involved in the covalent binding process. The red-shifted peaks in the FT-IR spectra suggested the formation of WPI-MCP conjugate, and MCP may be bound to the hydrophobic area of WPI with decreasing surface hydrophobicity. According to chemical bond measurement, hydrophobic interaction, hydrogen bond and disulfide bond played the main role in the formation process of WPI-MCP conjugate. According to morphological analysis, the O/W emulsion formed by WPI-MCP had a larger size than the emulsion formed by WPI. The conjugation of MCP with WPI improved the apparent viscosity and gel structure of emulsions, which was concentration-dependent. The oxidative stability of the WPI-MCP emulsion was higher than that of the WPI emulsion. However, the protection effect of WPI-MCP emulsion on β-carotene still needs to be further improved.

Effect of Hydrophobicity of Fluorescent Carbon Nanoparticles on Transport in Porous Media: Column Experiments and Modeling

AbstractEngineered carbon‐based nanoparticles are increasingly used for environmental, industrial, and medical purposes. Thus, understanding their interaction with and transport through materials is important. We examine the impact of nanoparticle hydrophobicity and porous medium surface area on the transport of carbon nanoparticles through sand‐packed columns under saturated and unsaturated conditions. The fluorescent carbon nanoparticles (FCNs) used in this study, synthesized from citric acid and ethanolamine, exhibit synthesis‐temperature‐dependent hydrophobicity. To quantify the impact of hydrophobicity on retention, we use FCNs synthesized at four temperatures: 190°C (FCN190), 210°C (FCN210), 230°C (FCN230), and 250°C (FCN250). Several observations are noted. First, the more hydrophobic particles (FCN230 and FCN250) attain lower outlet concentrations and mass recovery than more hydrophilic particles (FCN190 and FCN210). For instance, while 77% of the FCN190 was recovered after passing through a fine‐sand‐packed column, only 23% of the FCN250 was recovered. Second, sand surface area significantly impacts FCN recovery. A 17‐fold increase in sand surface area yields a 30% decrease in the recovery of FCN210. Third, no significant difference in the mass recovery of the FCNs was observed between the unsaturated and saturated conditions, which is attributed to the small size of the FCNs relative to the water film thickness surrounding sand grains. Fourth, the particle transport model in HYDRUS‐1D successfully simulated FCN transport, showing approximately a tenfold increase in the attachment coefficient for hydrophobic FCNs. In summary, through experiments and modeling, we show that hydrophobicity is a major factor impacting FCN transport.

Investigation of bubble nucleation on inhomogeneous wettability surfaces

ABSTRACT Surface wettability plays an essential role in bubble nucleation. This paper investigates the phase transition behaviour of argon films placed on inhomogeneous wettability substrates using molecular dynamics simulations. The location of bubble nucleation and initial nucleation time is investigated to reflect the effect of hydrophobic area fraction of inhomogeneous wettability surfaces on bubble nucleation. The results show that the bubbles appear first on the hydrophobic part of the inhomogeneous wettability surface. The relationship between hydrophobic area fraction and initial nucleation time is nonlinear. The initial nucleation time first decreases and then increases as the area of the hydrophobic region increases. In addition, the bubble nucleation process is restricted when the hydrophobic occupation is relatively large on inhomogeneous wettability surfaces. At last, the mechanism of bubble nucleation on inhomogeneous wettability surfaces is discussed in combination with the restrictive relationship between heat absorption and solid–liquid interaction energy. The amount of heat absorption does not directly determine the bubble nucleation. Bubble nucleation can arise in the location with a lower surface energy barrier once the heat absorption can overcome the solid–liquid interaction energy.

Plant protein nanogel–based patchy Janus particles with tunable anisotropy for perishable food preservation

AbstractJanus particles with anisotropic surfaces possess considerable potential for biological functionalization. However, little is known about the effect of surface anisotropy of Janus particles on the shelf life of perishable food. Herein, plant protein–based nanogels prepared by acylated rapeseed protein isolate (ARPI) are exploited as novel building blocks to decorate the surface of latex particles for Janus particle synthesis. The surface anisotropy of patchy latex particles can be facilely tailored via the suspension polymerization of the Pickering emulsion using ARPI nanogels as stabilizers. The surface distribution of ARPI nanogel on latex particles can be controlled by varying the aqueous phase conditions, and thus, the tunable hydrophilic–lipophilic balance (viz., Janus balance) varied from 0.78 to 1.76 for resulting patchy latex particles. Patchy latex particles with varied Janus balance were further investigated for the effects of their anti‐perishable coatings on perishable fruit preservation. The anisotropic patchy latex particles can act as a novel type of antibacterial agent to inhibit Ascomycota microorganisms’ growth on the surface of fruits and reduce the dehydration and respiration of fruits, all of which devote to a lengthened shelf life while being safe. Furthermore, it is found that the patchy latex particle with a spatial pattern of a hydrophobic area on its surface occupying 51.3% (Janus balance = 0.95) extends the shelf life of perishable food more effectively than that of other spatial arrangements. Overall, the exploration of anisotropic Janus particles offers an alternative strategy to preserve perishable food without using antimicrobial agents.

Conjugated Microporous Polymer Hybrid Microparticles for Enhanced Applicability in Silica‐Boosted Diclofenac Adsorption

Diclofenac (DCF) is one of the most widespread and consumed analgesics, thereby causing contamination of water bodies on a global scale. A common approach to tackle this pressing issue is the adsorption of DCF exploiting highly hydrophobic polymers. However, controlling the morphology of such polymers is essential. Adsorption capacities of the presented conjugated microporous polymer (CMP) in bulk‐form, for DCF (qsat) are as low as 13.0 mg g−1 despite exhibiting additional nitrogen moieties to specifically target DCF. Herein, an approach to drastically increase the DCF adsorption by increasing the accessible hydrophobic surface area by coating it around mesoporous silica microspheres is shown. These microspheres do not attribute to the adsorption of DCF themselves, but increase the accessibility of the CMP. Simultaneously, the applicability of the hybrid material is enhanced through higher wettability and more facile separation. As a consequence, an effective adsorbent is formed featuring an adsorption of up to 422 mg DCF per 1 × g CMP for the optimized silica/monomer ratio — comparable to expensive state‐of‐art materials. As the approach combines the advantages of the nano‐ and the micro‐dimension and does not depend on the actual adsorbent material, it holds great potential for general adsorption problems requiring highly engineered systems.

Vibrational Sum Frequency Generation Spectra of Water-Vapor Interfaces Covered by Alcohols: Effects of Surface Coverage and Coupling between Oscillators.

The present study deals with the effects of varying coverage of water surface by alcohols on the vibrational sum frequency generation (VSFG) spectrum of interfacial water. We have considered two different alcohols: Tertiary butyl alcohol (TBA) whose alkyl part is fully branched and stearyl alcohol (STA) which has a long linear alkyl chain with larger hydrophobic surface area than that of TBA. With increase of the alcohol concentration, the hydrogen bonded OH stretch region of the VSFG spectrum is found to change following a regular trend for the STA-water system, whereas non-monotonic variation of the VSFG spectrum is observed for the TBA-water system which can be correlated with the presence of very different interactions of TBA molecules at different concentrations. On increasing the concentration of TBA, the hydrophobic groups get more tilted towards the water phase and significant hydrophobic interactions are introduced at higher concentrations. Whereas, for STA, there is a gradual increase in the hydrophilic interaction. Because of stacking interactions between the long chain alkyl groups, the hydrophobic parts stay outward from the water phase at higher concentrations and a regular change in the VSFG spectrum is observed. We have also presented a computationally efficient scheme to calculate the VSFG spectrum of interfacial systems for coupled oscillators which is expected to be beneficial for the treatment of coupling where the interfacial system size is inherently large.

Is Structural Precision of Platonic Micelles Controlled Solely by Close-Packed Head Groups or Also by Hydrophobic Tail Packing? A DFT Exploration

Platonic micelles have been defined as structurally precise amphiphilic aggregates with discrete aggregation numbers corresponding to the close packing of spherical caps (representing head groups) on a sphere (representing hydrophobic core), analogous to the Tammes problem in geometry. Here, we use DFT to explore how an actual molecule behaves compared to the idealized picture based on the Tammes problem by also considering the packing of the tails. We modeled micelles of aggregation numbers 4 to 8 generated from the calix[4]arene amphiphile, PACaL3, with the tails forming a close-packed configuration while the headgroups are arranged as in Platonic solids. The DFT calculations reveal that tail packing overwhelmingly influences the equilibrium aggregation number. While the DFT prediction of a PACaL3 micelle of aggregation number 6 agrees with the scattering experiments of the Sakurai group, DFT calculations also suggest small concentrations of micelles of aggregation number 7. More interestingly, DFT calculations reveal that PACaL3 micelle formation occurs even though less than 20% of the hydrophobic tail surface is removed from contact with water, in contrast to the roughly 80% removal observed for classical surfactant micelles. While the close-packed head groups model predicts higher coverage of the hydrophobic surface for aggregation numbers 4 and 6 compared to 5 and 7, the DFT calculations also accounting for tail packing show that the surface coverage for aggregation numbers 5 and 7 is practically no different than that for aggregation number 4. Finally, although both the close-packed head groups model and the DFT calculations agree that the exposed hydrophobic surface area controls the equilibrium micelle aggregation number, the DFT calculations demonstrate how this exposed hydrophobic area is overwhelmingly determined by the tail group packing and not just by the close packing of head groups.

The effect of side chain variations on quinazoline-pyrimidine G-quadruplex DNA ligands

G-quadruplex (G4) DNA structures are involved in central biological processes such as DNA replication and transcription. These DNA structures are enriched in promotor regions of oncogenes and are thus promising as novel gene silencing therapeutic targets that can be used to regulate expression of oncoproteins and in particular those that has proven hard to drug with conventional strategies. G4 DNA structures in general have a well-defined and hydrophobic binding area that also is very flat and featureless and there are ample examples of G4 ligands but their further progression towards drug development is limited. In this study, we use synthetic organic chemistry to equip a drug-like and low molecular weight central fragment with different side chains and evaluate how this affect the compound's selectivity and ability to bind and stabilize G4 DNA. Furthermore, we study the binding interactions of the compounds and connect the experimental observations with the compound's structural conformations and electrostatic potentials to understand the basis for the observed improvements. Finally, we evaluate the top candidates' ability to selectively reduce cancer cell growth in a 3D co-culture model of pancreatic cancer which show that this is a powerful approach to generate highly active and selective low molecular weight G4 ligands with a promising therapeutic window.

Molecular Mechanism of Cyanidin-3-O-Glucoside Disassembling Aβ Fibril In Silico

The deposition of β-amyloid (Aβ) in the brain leads to neurotoxic effects and subsequent Alzheimer's disease (AD). While AD is becoming more and more prevalent in modern society, therapeutic efforts targeting Aβ could be a promising solution. Currently, two natural products are reported to disintegrate preformed Aβ fibril in vitro. Meanwhile, the chemical driving force behind this phenomenon remains unknown. Taking cyanidin-3-O-glucoside (Cy-3G) as an example, here we studied its interaction with different Aβ polymorphs in silico. Negative charges on different Aβ polymorphs draw the interaction with the flavylium cation on Cy-3G. Our results show that Aβ in a single peptide form in solution exposed more hydrophobic solvent accessible surface area than its fibril structure (per protomer), and Cy-3G interacts more intensively with the single peptide form than fibril as indicated by more hydrogen bonding formed and more amino acid residues involved in their hydrophobic interactions. Thus, the single Aβ peptide aggregation into fibril and fibril dissociation into single peptide equilibrium could be disturbed by the preferential binding of Cy-3G to the monomeric Aβ peptide, which leads to the disassembly of the pathogenic Aβ fibril. This study offers a novel perspective of Cy-3G alleviated AD syndrome beyond its dogmatic antioxidant activity.

Effect of attaching hydrophilic oligopeptides to the C-terminus of organic solvent-tolerant metal-free bromoperoxidase BPO-A1 from Streptomyces aureofaciens on organic solvent-stability

Metal-free bromoperoxidase BPO-A1 from Streptomyces aureofacience was selected among several similar enzymes exhibiting brominating activity as the most stable haloperoxidase against 70%(v/v) methanol. A comparison of the BPO-A1 and octahistidine-tagged BPO-A1 at the C-terminus (BPO-A1-His8) revealed that the His-tag enhanced the organic solvent-stability of BPO-A1 with pH- and heat-stabilities. Additionally, the contribution of the hydrophilicity at the C-terminal of BPO-A1 to the organic solvent-stability was confirmed employing several mutants bearing hydrophilic oligopeptides. Fortunately, two excellent mutants, BPO-A1-Lys8 and BPO-A1-Arg8, with high stabilities against various water-miscible organic solvents were obtained. In conclusion, the enhancing effect of the hydrophilic oligopeptides on the organic solvent-stability was associated with a decrease in the hydrophobic surface area near the C-terminus.

A Step Forward for Smart Clothes─Fabric-Based Microfluidic Sensors for Wearable Health Monitoring.

We report the first demonstration of fabric-based microfluidics for wearable sensing. A new technology to develop microfluidics on fabrics, as a part of an undergarment, is described here. Compared to conventional microfluidics from polydimethylsiloxane, fabric-based microfluidics are simple to make, robust, and suitable for efficient sweat delivery. Specifically, acrylonitrile butadiene styrene (ABS) films with precut microfluidic patterns were infused through fabrics to form hydrophobic areas in a specially controlled sandwich structure. Experimental tests and simulations confirmed the sweat delivery efficiency of the microfluidics. Electrodes were screen-printed onto the fabric-based microfluidic. A novel wearable potentiometer based on Arduino was also developed as the transducer and signal readouts, which was low-cost, standardized, open-source, and capable of wireless data transfer. We applied the sensor system as a standalone or as a module of a T-shirt to quantify [Ca2+] in a wearer's sweat, with physiological and accurate results generated. Overall, this work represents a critical step in turning regular undergarments into biochemically smart platforms for health monitoring, which will broadly benefit human healthcare.

Roles of amino acid hydrophobicity on methane-THF hydrates in the context of storage and stability

This report reveals the success of the formation of mixed methane-THF hydrates at room temperature (298.2 K) and a pressure of 9.2 MPa equipped with a hybrid stirring in the presence of amino acids as kinetic promoters. Five different amino acids in increasing order of hydrophobicity: glutamic acid, valine, leucine, methionine, and tryptophan, were used to investigate their effects on methane uptake, formation, and dissociation kinetics. The addition of hydrophobic amino acids (tryptophan, methionine, and leucine) promotes the hydrate formation to completion, which doubly increases the methane uptake compared to that without amino acids and with hydrophilic amino acids (glutamic acid and valine) at the same condition. The results indicate that the hydrophobicity has a positive contribution to the methane uptake by creating a hydrophobic area, enhancing hydrate growth to completion. Moreover, the time taken to complete hydrate by 90 percent has a negative correlation to the molecular weight of the amino acids. The morphological studies demonstrate that the hydrates with hydrophobic amino acids were more consolidated than the addition of hydrophilic amino acids. Lastly, the hydrates with hydrophobic amino acids show excellent stability for 30 days even if they are stored at a temperature higher than their equilibrium temperature at atmospheric pressure. The small amount of gas lost was due to intrinsic loss only. This opens the possibility for cost-reduction for methane hydrate in commercialization.

Abstract 15637: Detection and Characterization of Fibrin/Amyloid Microclots in Patients With Post-Acute Sequelae of Covid-19

LongCovid or Post-Acute Sequelae of COVID-19 (PASC) is a diagnosis given to patients who experience a wide range of debilitating chronic symptoms after infection with SARS-CoV-2. The majority of individuals are PCR negative, indicating microbiological recovery. There are currently few LongCovid/PASC blood-based biomarkers. We used fluorescence microcopy to identify unique fibrin/amyloid micro-thrombosis and hyperactivated platelets in individuals with PASC. These fibrin/amyloid microclots may impede blood flow to tissue. Methods: Whole blood was collected in citrate tubes from 30 matched healthy subjects and 30 PASC subjects. Platelet poor plasma (PPP) was prepared by centrifugation and stored at -80 °C. PPP was then exposed to thioflavin T (ThT), a fluorescence marker known to bind to and open hydrophobic areas on damaged amyloidogenic protein. Samples were viewed with fluorescence microscopy using a 63x/1.4 Oil DIC M27 objective (excitation wavelength 450nm-488nm, emission 499nm- 529nm). After a double-trypsin PPP digestion method, proteomic analysis of the PPP samples was performed. Results: Significant microclot load was observed in the PPP of participants with PASC compared to healthy participants (Fig. 1). Proteomic analysis revealed the presence of inflammatory molecules within digested microclots. Conclusion: Preliminary results suggest that the presence of microclots in PPP may be used as a diagnostic biomarker for the PASC. Characterization of inflammatory molecules and antibodies trapped within microclots might provide insight into the pathogenesis of PASC and serve as a basis for novel treatment strategies or preventative medicine. Figure: Representative specimens A) Microclots in healthy plasma. B) Microclots in PASC plasma.

Effects of the molecular weight of hyaluronan on the conformation and release kinetics of self-assembled 5-fluorouracil-loaded lysozyme-hyaluronan colloidal nanoparticles

Lysozyme (LYS) and hyaluronan with low (HA1: 3 kDa), medium (HA2: 120 kDa), and high (HA3: 1200 kDa) molecular weights were used to fabricate lysozyme-hyaluronan colloidal nanoparticles using a green self-assembly method. Fourier transform infrared spectroscopy indicated that hydrogen bonding, hydrophobic and electrostatic interactions promoted the formation of the colloidal nanoparticles. The hydrophobic area of prepared colloidal nanoparticles was quantified using a pyrene fluorescent probe, and the results showed that the LYS-HA3 nanoparticles had the strongest hydrophobic capacity. Furthermore, 5-fluorouracil (5-Fu) was used to evaluate encapsulation performance, demonstrating that the LYS-HA3 nanoparticles had the highest encapsulation ability (>90 %). All prepared 5-Fu-loaded lysozyme-hyaluronan (5-Fu@LYS-HA) colloidal nanoparticles exhibited excellent long-term storage stability at 4 °C for 60 days. Cellular uptake and in vitro release results indicated that the LYS-HA2 nanoparticles exhibited the highest cellular uptake efficiency, and the LYS-HA3 nanoparticles had the best slow-release effect, while the release process was mainly controlled by the combination of Fickian diffusion and structural relaxation, respectively. This study demonstrates the influence of molecular weight on the conformational and structural properties of colloidal nanoparticles, which has implications for the design of insoluble drug self-assembly systems.

High‐Entropy‐Alloy‐Nanoparticles Enabled Wood Evaporator for Efficient Photothermal Conversion and Sustainable Solar Desalination

AbstractHigh‐entropy‐alloy (HEA) nanoparticles with excellent photothermal conversion performances have been proven effective for solar steam generation abilities, but it remains a challenge to fabricate a macroscale evaporator through them. Here, assisting by the unique anisotropic porous structures of balsawood matrixes, a sustainable HEA‐nanoparticles‐balsawood (HEA‐BW) composited evaporator, in which two compositions construct an asymmetric surface wettability that the top surface of HEA nanoparticles acts as a hydrophobic photothermal area, while the bottom hydrophilic surface of balsawood allows for rapid water transportation, is assembled. The most efficient 8‐HEA‐BW realized an average optical absorption greater than 97% over the entire solar spectrum (250–2500 nm) and an excellent evaporation rate of 2.58 kg m−2 h−1 with a surface temperature of 80 °C under one sun irradiation. Surprisingly, a stable solar desalination performance of such composited evaporator can be observed in a 10‐cycles long‐term evaluation of the hypersaline water (20 wt% salinity) with an average evaporation rate of 1.65 kg m−2 h−1.

Experimental and computational studies of polycarboxylate dispersant effect on the properties of low‐rank coal water slurries

AbstractThe disadvantages of low‐rank coal in the preparation of coal water slurry (CWS) are well known, but the synthesis of suitable dispersants is a promising solution. Polycarboxylate dispersant (PC) is expected to be an efficient CWS dispersant due to its flexible and controllable structure. In this study, a series of binary PC dispersants were synthesized by controlling the ratio of acrylic acid (AA) to sodium styrene sulfonate (SSS), initiator fraction, and temperature, and the optimal PC was selected based on the apparent viscosity of 72# CWS at 100 s−1. The properties of 72# CWS were studied: This CWS exhibited shear‐thinning behavior, >14 static stability, and >55 wt% maximum solid loading, indicating the satisfactory performance of the optimal PC. The experimental results (including adsorption tests and zeta potential measurement) and molecular dynamics simulation showed that PC was effectively adsorbed on the surface of the coal particles by a horizontal multipoint adsorption mode, mainly through the interaction between the hydrophobic groups of the PC molecule and the hydrophobic areas of the coal particles. The hydrophilicity of the coal particles was therefore improved and the stability of their hydration layer was also enhanced, which accounted for the good static stability of 72# CWS. The amount of PC adsorption and the improved absolute zeta potential were associated with the decent properties of 72# CWS. This study is significant for promoting the molecular design of CWS dispersants based on their adsorption behavior.

Self-assembly, surface, antibacterial, and solubilization properties of phenylglycine type amino acid-based cationic surfactants

Here, synthesis and characterization of amino acid-based chiral cationic surfactants containing phenylglycine moiety, l-phenylglycine hydrochloride octyl ester (L-PgC8E), and l-phenylglycine hydrochloride decyl ester (L-PgC10E), and their physicochemical properties such as the micellization, surface, and volumetric parameters have been reported. In addition, the structural analyses of the aggregates of these esters were also performed by dynamic light scattering (DLS) and transmission electron microscopy (TEM) techniques. It was found that the presence of a phenyl ring in the head group promoted the micelle formation leading to a smaller critical micelle concentration (CMC) value and enhancing the adsorption efficiency with an increased hydrocarbon chain. Besides, the antibacterial activities of the synthesized surfactants have been explored against three Gram-positive (G+) and seven Gram-negative (G-) bacteria below and above their CMC values by measuring the zone of inhibition diameter. The results showed that L-PgC8E was more active than L-PgC10E against all bacteria; this was explained by the formation of smaller and less stable aggregates that could interact efficiently with the bacterial membrane. Furthermore, the solubilization power (SP) of both surfactants for Methyl Red (MR) was determined, and it was found that L-PgC10E with a longer hydrocarbon chain and forming a large hydrophobic area by its large aggregates showed a more efficient solubilizing power.