Hydrophobic End Research Articles

Molecular diffusion in aqueous methanol solutions: The combined influence of hydrogen bonding and hydrophobic ends.

Although the nonmonotonic variation in the diffusion coefficients of alcohol and water with changing alcohol concentrations in aqueous solutions has been reported for many years, the underlying physical mechanisms remain unclear. Using molecular dynamics simulations, we investigated the molecular diffusion mechanisms in aqueous methanol solutions. Our findings reveal that the molecular diffusion is co-influenced by hydrogen bonding and the hydrophobic ends of methanol molecules. A stronger hydrogen bond (HB) network and a higher concentration of hydrophobic ends of methanol molecules both enhance molecular correlations, thereby slowing molecular diffusion in the solution. As methanol concentration increases, the HB network weakens, facilitating molecular diffusion. However, the increased concentration of hydrophobic ends counteracts this effect. Consequently, the diffusion coefficients of water and methanol molecules exhibit nonmonotonic changes. Previous studies have only focused on the role of HB networks. For the first time, we have identified the impact of the hydrophobic ends of alcohol on molecular diffusion in aqueous alcohol solutions. Our research contributes to a better understanding and manipulation of the properties of aqueous alcohol solutions and even liquids with complex compositions.

Computational exploration of naturally derived peptides inhibitory mechanisms against ACE enzyme, from interactions to structural-dynamics

Naturally derived peptides have gained significant attention because of their potential to reduce blood pressure. These peptides can be derived from various sources, including snake venom, marine organisms, cow’s milk, seahorses, and plants. Investigating the underlying mechanisms of these peptides in lowering blood pressure is crucial for replacing synthetic drugs currently in use. In this regard, we conducted in silico studies, such as molecular docking, classical molecular dynamics (MD) simulations, and QM/MM simulation methods, on two naturally derived peptides (PAGPRGPA and WALKGYK) and Angiotensin II (ANGII) as the enzyme substrates for binding to sACE. The results of 500 ns MD calculations showed that the WALKGYK peptide occupies the ACE binding site, similar to the ANGII and BPPb peptides, two distinguished C-domain-specific inhibitors. Furthermore, QM/MM calculations demonstrated that no peptide bond cleavage was mediated by Zn2+ at the catalytic site of the peptides. However, during the 500 ns MD simulation, the backbone oxygens of LYS4 and GLY5 of the WALKGYK peptides were tightly coordinated to the Zn2+ ion. Free energy calculations also confirmed the higher affinity of the WALKGYK peptides for binding to sACE. In addition, structural analysis correlation showed a different pattern in PAGPRGPA compared to WALKGYK and ANGII. Despite the similarity of the peptide PAGPRGPA to typical ACE peptide inhibitors with hydrophobic ends, the electrostatic composition of the WALKGYK peptide showed a higher tendency towards ACE inhibition. Therefore, peptide residue compositions, such as WALKGYK, can be considered for designing new inhibitors with fewer side effects for sACE C-terminal inhibitors.

Experimental characterization and dual-temperature molecular dynamics simulation on the intervention of tea saponin in starch chain dynamic behavior

In this work, the typical properties of starchy products were innovatively described as six types of chain dynamic behaviors. Dual-temperature molecular dynamic simulations, alongside multi-experimental methods, were employed to tandemly explore the intervention effect and mechanism of tea saponin (TS, 0 %–40 % w/w) on these behaviors. The findings reveal that the hydrophilic and hydrophobic ends of TS provide numerous sites for hydrogen bonding and steric hindrance, respectively, which hinder the formation of hydrogen bonds between starch chains. This interaction mode facilitated the chain unwinding (pasting temperature: 79.8 → 76.4 °C) and movement (viscosity: 267.67 → 38.92 Pa.s), and also retarded chain short/long-term reassociation (elastic modulus: 0.41 → 0.14 Pa/min; hardening rate: 2.72 → 0.07 gf/d) and rearrangement (hardness: 15.50 → 10.00 gf). Notably, a critical TS content was observed between 10 % and 20 % w/w, beyond which textural collapse (hardness: 15.50 → 10.00 gf) occurred. This research offers a new strategy and relevant theoretical backing for the property regulation of starch products.

Truncated M13 phage for smart detection of E. coli under dark field

BackgroundThe urgent need for affordable and rapid detection methodologies for foodborne pathogens, particularly Escherichia coli (E. coli), highlights the importance of developing efficient and widely accessible diagnostic systems. Dark field microscopy, although effective, requires specific isolation of the target bacteria which can be hindered by the high cost of producing specialized antibodies. Alternatively, M13 bacteriophage, which naturally targets E. coli, offers a cost-efficient option with well-established techniques for its display and modification. Nevertheless, its filamentous structure with a large length-diameter ratio contributes to nonspecific binding and low separation efficiency, posing significant challenges. Consequently, refining M13 phage methodologies and their integration with advanced microscopy techniques stands as a critical pathway to improve detection specificity and efficiency in food safety diagnostics.MethodsWe employed a dual-plasmid strategy to generate a truncated M13 phage (tM13). This engineered tM13 incorporates two key genetic modifications: a partial mutation at the N-terminus of pIII and biotinylation at the hydrophobic end of pVIII. These alterations enable efficient attachment of tM13 to diverse E. coli strains, facilitating rapid magnetic separation. For detection, we additionally implemented a convolutional neural network (CNN)-based algorithm for precise identification and quantification of bacterial cells using dark field microscopy.ResultsThe results obtained from spike-in and clinical sample analyses demonstrated the accuracy, high sensitivity (with a detection limit of 10 CFU/μL), and time-saving nature (30 min) of our tM13-based immunomagnetic enrichment approach combined with AI-enabled analytics, thereby supporting its potential to facilitate the identification of diverse E. coli strains in complex samples.ConclusionThe study established a rapid and accurate detection strategy for E. coli utilizing truncated M13 phages as capture probes, along with a dark field microscopy detection platform that integrates an image processing model and convolutional neural network.Graphical

Molecular dynamics simulation of wax micro-structure characteristics in the oil-water emulsion

As a key issue in the flow assurance of wax-containing crude oils, the microscopic mechanism of wax deposition in multiphase pipelines is still unclear. Based on macroscopic experimental data, two forms of crystallized wax have been found under an oil-water emulsion, including adsorbed wax on the interface of water droplets and suspended wax in the bulk oil phase, which are the important factors influencing wax deposition. However, the micro-formation mechanism of the adsorbed & suspended wax is not elucidated. In this work, molecular dynamics simulations are used to investigate the micro-structure characteristics of the adsorbed & suspended wax in the oil-water emulsion containing surfactant Span60. A method is proposed to quantitatively calculate the distributions of the adsorbed & suspended wax and the percentage of wax adsorption area at the oil-water interface. The results indicate that surfactant with the hydrophilic end will insert into the water phase and the trailing hydrophobic end stretching will point to the oil phase during co-crystallizing with wax molecules. Meanwhile, the interface tension is further reduced by tilting the adsorbed wax tail chain to enhance the adsorption stability. Based on the complicated influence of surfactants on wax adsorption, the quantitative distribution characteristics of the adsorbed & suspended wax in the oil-water emulsion are complex under different wax carbon numbers and surfactant/wax contents. This microscopic investigation of wax distribution in oil-water emulsion can support the establishment of better strategies for solving the wax deposition problem in multiphase flow.

Silencing MUC1 to regulate intracellular lipid metabolism: Overcoming sunitinib resistance and inhibiting metastasis in renal cell carcinoma

Renal cell carcinoma (RCC) has been extensively studied and is a paradigmatic example of a malignancy distinguished by metabolic reprogramming. Reprogramming lipid metabolism is crucial for determining the response and resistance to chemotherapy. To overcome this, we developed a modified nanomicelle delivery system comprising polyethyleneimine (PEI) as a positive charge donor and ibuprofen as the hydrophobic end. The overall system, denoted as SPPI, is PEGylated, conjugated with sialic acid, and plays a targeting role. This system successfully delivered siRNA to cancer cells by overcoming systemic and cellular barriers. The resulting conjugates form uniform, spherical nanomicelles (37.8 ± 0.9 nm; 25.5 ± 1.4 mV) with targeting ability, stability, efficient delivery, and low toxicity. The complicated and indirect way cholesterol affects ATP-binding cassette transporters was investigated. Administering SPPI/siMUC1 resulted in significant suppression of MUC1 expression and a 3.25-fold decrease in cholesterol synthesis compared to the control, and it subsequently reversed resistance to sunitinib by modulating P-GP, ABCG2, and MRP1 activities. Importantly, SPPI/siMUC1 nanomicelles demonstrated outstanding growth inhibition (72.2 %) of sunitinib-resistant 786-O cell xenografts and remarkable inhibitory effects on tumor metastasis (45.0 %) without observable systemic toxicity according to tissue analysis and weight change evaluation. The efficacy and safety of SPPI/siMUC1 in the treatment of ccRCC were demonstrated, especially after drug resistance develops. Thus, this study introduces a novel strategy for addressing drug resistance in metabolically active cancers by targeting the lipid metabolism pathway.

A ZSM-5 zeolite nanosheet with single-unit-cell thickness templated by bi-ammonium surfactants with large-diameter hydrophobic groups

Ultra-thin zeolite nanosheets have received widespread attention due to their superior catalytic performance compared to bulk zeolites. Here, we have designed a new structure-directing agent with a tert-butyl benzene group as the large-diameter hydrophobic end of a bi-ammonium surfactant molecule. Using this novel structure-directing agent, zeolite nanosheets with a thickness of ∼ 2.5 nm were synthesized, which exhibit better catalytic performance than bulky zeolites in the Friedel-Crafts alkylation reaction of trimethylbenzene and benzyl alcohol.

Unravelling Competitive Interactions between Polymer Side Chains and End Groups with β-Cyclodextrin.

This study investigates unexpected competitive host-guest interactions of β-cyclodextrin (β-CD), which can occur with polymers in aqueous solution, using the examples of the two polymers poly(oligo(ethylene glycol) methyl ether methacrylate) and poly(glycerol mono methacrylate). Systematic structural modifications of the polymer provide insight into the host-guest interaction with β-CD and the competition between side chains and end groups such as hydrophobic end groups remaining from reversible addition fragmentation chain transfer polymerization or intentionally implemented molecular recognition units such as arylazopyrazole photoswitches.

Polymers in Drug Delivery: Analyzing Beta-carotene Aggregation in Response to PEG-b-PLA

Synthetic polymers have quickly become ubiquitous in all aspects of modern society, from single-use plastics to medical treatment. This study focuses on the behavior of polymers in the medical context of drug delivery, which requires a highly controlled and targeted release of the therapeutic agent. However, current medical treatments such as anticancer drugs lack precision and lose effectiveness after entering the body. PEG-b-PLA is uniquely structured to have both hydrophilic and hydrophobic ends, which makes it capable of forming polymeric micelles. Beta-carotene, a lipophilic compound, was employed as a surrogate molecule to represent an anticancer drug. This study’s purpose was to study PEG-b-PLA in aqueous solutions with varying concentrations of Beta-carotene and sodium chloride to mimic a human drug delivery procedure. It was hypothesized that PEG-b-PLA would limit the aggregation of Beta-carotene to a constant size, regardless of the outside environment. For that purpose, this study created four mixtures, each with varying concentrations of DI water, Beta-carotene, sodium chloride, and PEG-b-PLA. Qualitative data was collected by using a laser beam to observe the aggregation of Beta-carotene in each mixture, and each mixture was analyzed in a dynamic light scattering (DLS) instrument to determine exact micelle sizes. It was determined that the addition of PEG-b-PLA significantly reduced the aggregation of Beta-carotene in an electrolyte solution, demonstrating the stabilizing role PEG-b-PLA plays in drug delivery. Recent innovations like smart polymers consist of molecules like PEG-b-PLA and have been shown to successfully transport medical drugs, potentially making highly targeted anticancer treatment a reality.

Block Sequence Effects on the Self-Assembly Behaviors of Polypeptide-Based Penta-Block Copolymer Hydrogels.

Peptide-based hydrogels have great potential for applications in tissue engineering, drug delivery, and so on. We systematically synthesize, characterize, and investigate the self-assembly behaviors of a series of polypeptide-based penta-block copolymers by varying block sequences and lengths. The copolymers contain hydrophobic blocks of poly(γ-benzyl-l-glutamate) (PBG, Bx) and two kinds of hydrophilic blocks, poly(l-lysine) (PLL, Ky) and poly(ethylene glycol) (PEG, EG34), where x and y are the number of repeating units of each block, where PBG and PLL blocks have unique functions for nerve regeneration and cell adhesion. It shows that a sufficient length of the middle hydrophilic segment capped with hydrophobic end PBG blocks is required. They first self-assemble into flower-like micelles and sequentially form transparent hydrogels (as low as 2.3 wt %) with increased polymer concentration. The hydrogels contain a microscale porous structure, a desired property for tissue engineering to facilitate the access of nutrient flow for cell growth and drug delivery systems with high efficiency of drug storage. We hypothesize that the structure of Bx-Ky-EG34-Ky-Bx agglomerates is beyond micron size (transparent), while that of Ky-Bx-EG34-Bx-Ky is on the submicron scale (opaque). We establish a working strategy to synthesize a polypeptide-based block copolymer with a wide window of sol-gel transition. The study offers insight into rational polypeptide hydrogel design with specific morphology, exploring the novel materials as potential candidates for neural tissue engineering.

Agricultural waste Ipomoea batatas leaves for low-temperature dyeing and functional finishing of polyester fabrics

The increasing focus on eco-friendly textiles and cleaner production manufacturing techniques have made natural pigments for coloring and enhancing the functionality of textiles become a popular trend. This research aimed to extract plant pigment from bio-waste Ipomoea batatas leaves and utilize it for dyeing and functional decoration of polyester fabric at low temperature. The study optimized the parameters for pigment extraction and fabric dyeing and also investigated the stability of the pigment solution. The finding indicated that strong acids and bases, intense light, high temperatures, and oxidants have a greater impact on pigment stability. Observation and analysis using SEM, bio-optical microscope, FTIR, and UV–vis–NIR absorption spectroscopy revealed that chlorophyll pigment entered into the interior of polyester molecular chains through hydrophobic end intercalation and was retained by the physical forces, enabling low-temperature coloring and functional finishing of polyester fabrics. As a result, the polyester fabrics dyed with natural pigment exhibited excellent resistance to rubbing, washing, saliva, and perspiration (rated at level 4 or higher), except for the average light fastness (only grade 4). Additionally, the dyed polyester fabrics demonstrated outstanding UV resistance (UPF of 33.57 for raw polyester and 120.77 for pre-mordant dyed polyester) and antibacterial properties (raw polyester agar plates showed bacterial growth, while the colored polyester agar plates had almost no bacterial growth). Even after 10 wash cycles, the dyed polyester fabrics maintained their UV protection and antibacterial properties. This research is expected to provide a new approach to the valuable utilization of agricultural residues in the textile industry.

The Synergistic Influence of the Hydrophobic and Hydrophilic Ends on the Primary Dielectric Relaxation Rate of Methanol

The primary dielectric relaxation process of monoalcohols typically exhibits characteristic Debye behavior, and the factors influencing its rate have become a research focus in recent years. It is generally believed that the hydrophilic end (i.e., the hydroxyl group) of alcohol molecules plays a major role in the primary dielectric relaxation process through hydrogen bonding networks, while the hydrophobic end mainly exerts an indirect effect by influencing the formation of intermolecular hydrogen bonds. This study systematically investigates the factors influencing the primary dielectric relaxation process of methanol using molecular dynamics simulations. As the simplest alcohol molecule, studying methanol can provide insights into the common characteristics of monohydroxy alcohols and even alcohols in general. The well-known "wait-and-switch" model currently emphasizes the impact of hydrogen bond partner concentration on the primary dielectric relaxation rate of the system. In this study, we systematically investigated the factors influencing the primary dielectric relaxation rate of methanol by independently adjusting the O-H bond length (<i>d<sub>oh</sub></i>), the C-O bond length (<i>d<sub>oc</sub></i>), and the methyl diameter (<i>σ<sub>methyl</sub></i>) of methanol molecules, and provided significant extensions to the "wait-and-switch" model:1) By adjusting <i>doh</i>, we found that a stronger total hydrogen bond energy (<i>U<sub>HB</sub></i>) in the system enhances the correlation of molecular motion, slowing down the reorientation rate of molecules and, consequently, the primary dielectric relaxation process of the system. 2) By adjusting <i>d<sub>co</sub></i>, we discovered that a longer hydrophobic end not only slows down the primary dielectric relaxation process by stabilizing the intermolecular hydrogen bond network but also directly reduces the rate of this process. 3) By adjusting <i>σ<sub>methyl</sub></i>, we found that an excessively small <i>σ<sub>methyl</sub></i> is detrimental to the stability of the hydrogen bond network, while an excessively large <i>σ<sub>methyl</sub></i> hinders the formation of hydrogen bonds. Both cases negatively affect the correlation of molecular motion. The primary dielectric relaxation process of the system is slowest when <i>σ<sub>methyl</sub></i> is at a moderate level. It was ultimately found that factors such as <i>U<sub>HB</sub></i> and the volume of the correlated motion (<i>V<sub>CM</sub></i>), along with the concentration of hydrogen bond partners in the system, collectively form the key elements influencing the primary dielectric relaxation rate of the system. Our results can reasonably explain experimental phenomena that the original "wait-and-switch" model could not account for. This study contributes to a deeper understanding of the relaxation processes of alcohol molecules and their physical origins.

Sono-responsive smart nanoliposomes for precise and rapid hemostasis application.

Massive hemorrhage caused by injuries and surgical procedures is a major challenge in emergency medical scenarios. Conventional means of hemostasis often fail to rapidly and efficiently control bleeding, especially in inaccessible locations. Herein, a type of smart nanoliposome with ultrasonic responsiveness, loaded with thrombin (thrombin@liposome, named TNL) was developed to serve as an efficient and rapid hemostatic agent. Firstly, the hydrophilic cavities of the liposomes were loaded onto the sono-sensitive agent protoporphyrin. Secondly, a singlet oxygen-sensitive chemical bond was connected with the hydrophobic and hydrophilic ends of liposomes in a chemical bond manner. Finally, based on the host guest effect between ultrasound and the sono-sensitizer, singlet oxygen is continuously generated, which breaks the hydrophobic and hydrophilic ends of liposome fragments, causing spatial collapse of the TNL structure, swiftly releases thrombin loaded in the hydrophilic capsule cavity, thereby achieving accurate and rapid local hemostasis (resulted in a reduction of approximately 67% in bleeding in the rat hemorrhage model). More importantly, after thorough assessments of biocompatibility and biodegradability, it has been confirmed that TNL possesses excellent biosafety, providing a new avenue for efficient and precise hemostasis.

Ambient stable solution-processed organic field effect transistors from electron deficient planar aromatics: effect of end-groups on ambient stability.

Ambient stable solution processed n-channel organic field effect transistors (OFETs) are essential for next-generation low-cost organic electronic devices. Several molecular features, such as suitable orbital energy levels, easy synthetic steps, etc., must be considered while designing efficient active layer materials. Here, we report a case of improved ambient stability of solution-processed n-type OFETs upon suitable end-groups substitution of the active layer materials. A pair of core-substituted napthalenediimide (NDIFCN2 and EHNDICN2) derivatives with alkyl and perfluorinated end groups are considered. The transistor devices made out of these two derivatives exhibited largely different ambient stability behavior. The superior device stability (more than 25 days under ambient conditions) of one of the derivatives (NDIFCN2) was ascribed to the presence of fluorinated end groups that function as hydrophobic guard units inhibiting moisture infiltration into the active layer, thereby achieving ambient stability under humid conditions (>65% relative atmospheric humidity). Molecular level optical and electrochemical properties, thermal stability, and the solution-processed (spin coat and drop cast active layers) device characteristics are described in detail. Our findings highlight the requirement of hydrophobic end groups or sidechains for ambient stability of active layer materials, along with deep LUMO levels for ambient stability.

Selected pesticidal POPs and metabolites in the soil of five Vietnamese cities: Sources, fate, and health risk implications

Large quantities of organochlorine pesticides (OCPs) have been used in tropical regions. The fate processes and risks of these legacy contaminants in the tropics are poorly understood. Herein, we investigated the occurrence of three classes of widely used OCPs and their metabolites in surface and core soil from five cities across Vietnam with a prevalent tropical monsoon climate and a long history of OCP application. We aimed to elucidate migration potentials, degradation conditions, and transformation pathways and assess current health risks of these contaminants. Generally, the concentrations of OCPs and metabolites in the soil core were slightly lower than those in surface soil except for hexachlorocyclohexane (HCH) isomers. 2,2-bis(4-chlorophenyl)-1,1,1-trichloroethane (p,p’-DDT), 2,2-bis(4-chlorophenyl)-1,1-dichloroethylene (p,p’-DDE), the sum of dicofol and 4,4′-dichlorobenzophenone (p,p’-DBP), and 2,2-bis(4-chlorophenyl)-1,1-dichloroethane (p,p’-DDD) were the most abundant compounds in both surface and core soils. A uniform distribution of HCHs (the sum of α-, β-, γ-, and δ-HCH) at trace levels was found in almost all soils, serving as evidence of the lack of recent use of HCH pesticides. Higher concentrations of DDTs (the sum of DDT, DDD, and DDE) were observed in north-central Vietnamese soil, whereas appreciable concentrations of ENDs (the sum of α- and β-endosulfan and endosulfan sulfate) were only found in southern Vietnamese soils. Empirical diagnostic ratios indicated residuals of DDTs were mainly from technical DDT rather than dicofol, whereas aged HCHs could be explained by the mixture of lindane and technical HCH. Both historical applications and recent input explain DDTs and ENDs in Vietnamese soil. Total organic carbon performs well in preventing vertical migration of more hydrophobic DDTs and ENDs. The dominant transformation pathway of DDT in surface soil followed p,p’-DDE→2,2-bis(4-chlorophenyl)-1-chloroethylene or p,p’-DDMU→1,1-bis(4-chlorophenyl)ethylene or p,p’-DDNU→p,p’-DBP, whereas the amount of p,p’-DDMU converted from p,p’-DDD and p,p’-DDE is similar in soil core. Non-cancer risks of OCPs and metabolites in all soils and cancer risks of those chemicals in core soils were below the safety threshold, whereas a small proportion of surface soil exhibited potential cancer risk after considering the exposure pathway of vegetable intake. This study implied that organic matter in non-rainforest tropical deep soils still could hinder the leaching of hydrophobic organic contaminants as in subtropical and temperate soils. When lands with a history of OCP application are used for agricultural purposes, dietary-related risks need to be carefully assessed.

Molecular dynamics simulation study of the effect of molecular structure of warm mix additive on lubricating properties

Based on tribological theory, molecular dynamics (MD) simulation is used to characterize the lubrication behavior of warm mix additive at the friction interface between asphalt and aggregate from the molecular scale. The base asphalt lubricating film model and the warm mix asphalt lubricating film model were established respectively. The asphalt-mineral interfacial shear friction system was constructed using two types of lubricating film models and SiO2 (001) friction surface. The effects of shear rate, system temperature and the hydrophobic end carbon chain length of the warm mix additive on the lubricating property of the simulated system were investigated, and the mechanism of warm mix additive was further revealed. The results show that the higher the shear rate, the greater the shear stress on the surface of the lubricating film. The shear stress on the surface of the warm mix asphalt lubricating film is significantly smaller than the base asphalt lubricating film. The system temperature has no noticeable effect on the shear stress. Additionally, with increasing hydrophobic end carbon chain length of the warm mix additive, the shear stress of the warm mix asphalt lubricating film decreases. The temperature of the lubricating film gradually rises from the interface to the inside, reaching a maximum value at the film's centre. The temperature inside the base asphalt lubricating film rises with an increasing shear rate. In contrast, the temperature distribution inside the warm mix asphalt lubricating film is relatively constant within a specific range. The cohesive energy of asphalt lubricating film and its adsorption energy on the SiO2 surface both decrease with an increasing shear rate, and the temperature has little effect on the cohesive energy and adsorption energy. With the increase of the hydrophobic end carbon chain length of the warm mix additive, the adsorption energy of warm mix asphalt lubricating film increases and then decreases, the self-diffusion coefficient decreases first and then increases, and the cohesive energy increases gradually. The number density distribution shows a stronger affinity between warm mix additive and SiO2. In conclusion, this paper reveals the lubrication mechanism of surfactant warm mix additive, which can provide reference and guidance for subsequent scholars to further study the warm mixing mechanism by MD method, as well as for the study of asphalt-aggregate interfacial behavior.

Aqueous Cationic Fluorinated Polyurethane for Application in Novel UV-Curable Cathodic Electrodeposition Coatings.

Aqueous polyurethane is an environmentally friendly, low-cost, high-performance resin with good abrasion resistance and strong adhesion. Cationic aqueous polyurethane is limited in cathodic electrophoretic coatings due to its complicated preparation process and its poor stability and single performance after emulsification and dispersion. The introduction of perfluoropolyether alcohol (PFPE-OH) and light curing technology can effectively improve the stability of aqueous polyurethane emulsions, and thus enhance the functionality of coating films. In this paper, a new UV-curable fluorinated polyurethane-based cathodic electrophoretic coating was prepared using cationic polyurethane as a precursor, introducing PFPE-OH capping, and grafting hydroxyethyl methacrylate (HEMA). The results showed that the presence of perfluoropolyether alcohol in the structure affected the variation of the moisture content of the paint film after flash evaporation. Based on the emulsion particle size and morphology tests, it can be assumed that the fluorinated cationic polyurethane emulsion is a core-shell structure with hydrophobic ends encapsulated in the polymer and hydrophilic ends on the outer surface. After abrasion testing and baking, the fluorine atoms of the coating were found to increase from 8.89% to 27.34%. The static contact angle of the coating to water was 104.6 ± 3°, and the water droplets rolled off without traces, indicating that the coating is hydrophobic. The coating has excellent thermal stability and tensile properties. The coating also passed the tests of impact resistance, flexibility, adhesion, and resistance to chemical corrosion in extreme environments. This study provides a new idea for the construction of a new and efficient cathodic electrophoretic coating system, and also provides more areas for the promotion of cationic polyurethane to practical applications.

Heterocyclic group end-capped polyethylene glycol: Synthesis and used as corrosion inhibitors for mild steel in HCl medium

In this work, two categories of water-soluble polymeric corrosion inhibitors (CIs) are contributed. These CIs are composed by polyethylene glycol (PEG) middle segment and oleic imidazoline (or thiophene) end groups, respectively labeled as OIM-PEG-OIM and Th-PEG-Th. Two facile synthetic strategies involve epoxy-amino reaction and thiol-acrylate Michael addition were employed. Both Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy verified that a series of target products were successfully obtained. The solution transmittance measurements indicated that with the increase of the PEG segment length, the water solubility of CIs enhanced. And these obtained CIs exhibit somewhat surface activity and could reduce the solution surface tensions to a certain extent. The inhibition efficiencies of these CIs for mild steel in HCl medium were evaluated by weight loss measurements, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). It was found that both OIM-PEG-OIM and Th-PEG-Th show an improved corrosion inhibition efficiency as compared to PEG. And as compared to heterocyclic compounds, introduction of PEG segment showed a negligible influence on their performances. Both CIs can form chemisorption on the metal surface, and the adsorption process follow Langmuir adsorption mechanism. OIM-PEG-OIM exhibit superior inhibition performance and stability as compared to Th-PEG-Th, which can be attributed to the fact that OIM-PEG-OIM bearing two long hydrophobic alkyl end groups. Scanning electron microscope (SEM) observations as well as atomic force microscopy (AFM) measurements also confirmed both OIM-PEG-OIM and Th-PEG-Th could serve as water-soluble CIs for mild steel.

Effects of polymer terminal group inside micelle core on paclitaxel loading promoting and burst release suppressing.

Paclitaxel (PTX) is widely used in the treatment of advanced esophageal and gastric cancer. Polymeric micelles can improve the drug-loading efficiency of PTX. However, the end groups on the amphiphilic blocks affect the drug-loading efficiency and the release kinetics of polymeric micelles. Therefore, there is an urgent need to disclose the tailoring of the core-/shell-forming terminal groups. Different from the conventional block copolymer synthesis in the reversible addition-fragmentation chain-transfer polymerization, which has a hydrophilic end group on the core-forming blocks, an alternative monomer addition method was applied to tune and obtain two block copolymers with symmetrical and similar block length PBMAn-b-PNAMm [PNAM, poly(N-acryloylmorpholine); PBMA, poly(n-butyl methacrylate)] but distinct end groups on the hydrophobic core-forming blocks, that is, HOOC-PBMA-PNAM-Phen and HOOC-PNAM-PBMA-Phen. The chemical structure of the resulting copolymers was elucidated by proton nuclear magnetic resonance spectroscopy and differential scanning calorimetry. The spherical morphology revealed by transmission electron microscopy and the uniform particle size revealed by dynamic light scattering analysis clearly confirmed the successful preparation of a PTX-polymeric micelle complex. The particle sizes of HOOC-PBMA-PNAM-Phen and HOOC-PNAM-PBMA-Phen were about 40 and 235 nm respectively. The PTX loading efficiency of HOOC-PBMA-PNAM-Phen was much lower than that of HOOC-PNAM-PBMA-Phen. The PTX release from HOOC-PBMA-PNAM-Phen was much slower than that of HOOC-PNAM-PBMA-Phen. The polymers had glass transition temperature (Tg) values of 70.24 and 74.22 ℃, which was from the HOOC-PBMA-PNAM-Phen and HOOC-PNAM-PBMA-Phen micelles, respectively. The systematic study on the PTX loading and releasing profile disclosed that, compared with the HOOC-PBMA-PNAM-Phen, the micelles with Phen group on the hydrophobic block (HOOC-PNAM-PBMA-Phen) enhanced drug loading and prolonged drug release but with a larger particle size. The results indicated that the hydrophobic end group Phen on the core-forming blocks can promote hydrophobic drug loading and suppress burst release.

Boosting stability and therapeutic potential of proteolysis-resistant antimicrobial peptides by end-tagging β-naphthylalanine.

Recently, much emphasis has been placed on solvingthe intrinsic defects of antimicrobial peptides (AMPs), especially their susceptibility to protease digestion for the systemic application of antibacterial biomaterials. Although many strategies have increased the protease stability of AMPs, antimicrobial activity was severely compromised, thereby substantially weakening their therapeutic effect. To address this issue, we introduced hydrophobic group modifications at the N-terminus of proteolysis-resistant AMPs D1 (AArIIlrWrFR) through end-tagging with stretches of natural amino acids (W and I), unnatural amino acid (Nal) and fatty acids. Of these peptides, N1 tagged with a Nal at N-terminus showed the highest selectivity index (GMSI=19.59), with a 6.73-fold improvement over D1. In addition to potent broad-spectrum antimicrobial activity, N1 also exhibited high antimicrobial stability toward salts, serum and proteases in vitro and ideal biocompatibility and therapeutic efficacy in vivo. Furthermore, N1 killed bacteria through multiple mechanisms, involving disruption of bacterial membranes and inhibition of bacterial energy metabolism. Indeed, appropriate terminal hydrophobicity modification opens up new avenues for developing and applying high-stability peptide-based antibacterial biomaterials. STATEMENT OF SIGNIFICANCE: To improve the potency and stability of proteolysis-resistant antimicrobial peptides (AMPs) without increasing toxicity, we constructed a convenient and tunable platform based on different compositions and lengths of hydrophobic end modifications. By tagging an Nal at the N-terminal, the obtained target compound N1 exhibited strong antimicrobial activity and desirable stability under multifarious environments in vitro (proteases, salts and serum), and also showed favorable biocompatibility and therapeutic efficacy in vivo. Notably, N1 exerted its bactericidal effect by damaging bacterial cell membranes and inhibiting bacterial energy metabolism in a dual mode. The findings provide a potential method for designing or optimizing proteolysis-resistant AMPs thus promoting the development and application of peptide-based antibacterial biomaterial.