DNA‐Templated Introduction of an Aldehyde Handle in Proteins

Many medical and biotechnological applications rely on protein labeling, but a key challenge is the production of homogeneous and site‐specific conjugates. This can rarely be achieved by simple residue‐specific random labeling, but generally requires genetic engineering. Using site‐selective DNA‐templated reductive amination, we created DNA–protein conjugates with control over labeling stoichiometry and without genetic engineering. A guiding DNA strand with a metal‐binding functionality facilitates site‐selectivity by directing the coupling of a second reactive DNA strand in the vicinity of a protein metal‐binding site. We demonstrate DNA‐templated reductive amination for His₆‐tagged proteins and metal‐binding proteins, including IgG1 antibodies. We also used a cleavable linker between the DNA and the protein to remove the DNA and introduce a single aldehyde on the protein. This functions as a handle for further modifications with desired labels. In addition to directing the aldehyde positioning, the DNA provides a straightforward route for purification between reaction steps.     

Synthesis and degradation of agar‐carbomer based hydrogels for tissue engineering applications

Hydrogels studied in this investigation, synthesized starting from agarose and Carbomer 974P, were chosen for their potential use in tissue engineering. The strong ability of hydrogels to mimic living tissues should be complemented with optimized degradation time profiles: a critical property for biomaterials but essential for the integration with target tissue. In this study, chosen hydrogels were characterized both from a rheological and a structural point of view before studying the chemistry of their degradation, which was performed by several analysis: infrared bond response [Fourier transform infrared (FT‐IR)], calorimetry [differential scanning Calorimetry (DSC)], and % mass loss. Degradation behaviors of Agar‐Carbomer hydrogels with different degrees of crosslinkers were evaluated monitoring peak shifts and thermal property changes. It was found that the amount of crosslinks heavily affect the time and the magnitude related to the process. The results indicate that the degradation rates of Agar‐Carbomer hydrogels can be controlled and tuned to adapt the hydrogel degradation kinetics for different cell housing and drug delivery applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Removing paraffin‐based wax coatings from old corrugated containers using supercritical carbon dioxide

Supercritical carbon dioxide (SC‐CO₂) extractions of paraffin‐based wax coatings from saturated and curtain‐coated old corrugated containers (OCC) are reported. Extractions were performed in a 500‐mL reactor (300 bar, 100°C, 50 g CO₂/min and 1 h). Wax removal efficiencies of 98 and 70% for saturated and curtain‐coated OCC, respectively, were obtained. Under similar conditions, extractions in the presence of water resulted in an extraction efficiency of 99% for saturated OCC. Decreasing the operating pressure to 200 bar decreased the extraction efficiency to approximately 50%. Gas chromatography (GC) of the wax coatings on OCC, before and after extraction with SC‐CO₂, showed a slight shift in the molecular weight distribution of the paraffin wax (after SC‐CO₂ extraction) toward higher molecular weights for both saturating wax and curtain‐coating wax. There was no evidence of chemical degradation or modification of the paraffin wax coatings by SC‐CO₂. The packing density, packing arrangement, and dimensions of the curtain‐coated OCC in the extraction apparatus affected the extraction efficiency. Loose packing compared to tight packing, 1 × 1 cm squares versus 1 × 20 cm strips, had higher extraction efficiencies; a random packing arrangement was better than packing with the fluting material in the direction of SC‐CO₂ flow. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2699–2704, 2002     

Chemical modification and synthesizing conditions of nanocomposite hydrogels with high mechanical strength crosslinked by hydrophilic reactive microgels

Series of polyacrylamide hydrogels with high mechanical strength were synthesized using hydrophilic reactive microgels (HRM) with C?C double bonds as crosslinkers. The hydrophilic microgels were prepared by inverse emulsion photopolymerization and then were chemical modified by N‐methylolacrylamide (NMA) to obtain HRM. Chemical‐modifying conditions affecting the HRM double bound content were investigated. The maximum double‐bond content was 1.82% at the optimum conditions of NMA 8 g, hydrochloric acid 0.8 mL, reaction temperature 60°C, and time 4 h. The mechanical properties of the hydrogels were significantly enhanced by using HRM as crosslinkers instead of the conventional crosslinkers. These HRM hydrogels were studied by varying such parameters as HRM content, monomer concentration, HRM double‐bond content, and the initiator dosage. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Effect of crosslinkers on the preparation and properties of ETFE‐based radiation‐grafted polymer electrolyte membranes

This study concerns a comparative study of three crosslinkers, divinylbenzene (DVB), 1,2‐bis(p,p‐vinylphenyl)ethane (BVPE), and triallyl cyanurate (TAC) crosslinked poly(ethylene‐co‐tetrafluoroethylene) (ETFE)‐based radiation‐grafted membranes, which were prepared by radiation grafting of p‐methylstyrene onto ETFE films and subsequent sulfonation. The effect of the different types and contents of the crosslinkers on the grafting and sulfonation, and the properties such as water uptake, proton conductivity, and thermal/chemical stability of the resulting polymer electrolyte membranes were investigated in detail. Introducing crosslink structure into the radiation‐grafted membranes leads to a decrease in proton conductivity due to the decrease in water uptake. The thermal stability of the crosslinked radiation‐grafted membranes is also somewhat lower than that of the noncrosslinked one. However, the crosslinked radiation‐grafted membranes show significantly higher chemical stability characterized in the 3% H₂O₂ at 50°C. Among the three crosslinkers, the DVB shows a most pronounced efficiency on the crosslinking of the radiation‐grafted membranes, while the TAC has no significant influence; the BVPE is a mild and effective crosslinker, showing the moderate influence between the DVB and TAC crosslinkers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4565–4574, 2006     

Porous Chitosan Scaffolds: A Systematic Study for Choice of Crosslinker and Growth Factor Incorporation

A systematic study was conducted to evaluate the crosslinker and method of incorporation for bovine serum albumin (BSA) into chitosan hybrid scaffolds (CH-ALG) for better cartilage tissue engineering applications. Formaldehyde and sodium tripolyphosphate were used crosslinkers for fabrication of CH-ALG scaffolds using BSA as growth factor by direct incorporation and microencapsulation methods. An in vitro release study of BSA with maximum release (80%) for scaffolds of formaldehyde crosslinked was found. The present findings show that the CH-ALG hybrid scaffolds have been potential use in biomedical applications.     

Development of a Hypersensitive Periodate‐Cleavable Amino Acid that is Methionine‐ and Disulfide‐Compatible and its Application in MHC Exchange Reagents for T Cell Characterisation

Incorporation of cleavable linkers into peptides and proteins is of particular value in the study of biological processes. Here we describe the synthesis of a cleavable linker that is hypersensitive to oxidative cleavage as the result of the periodate reactivity of a vicinal amino alcohol moiety. Two strategies directed towards the synthesis of a building block suitable for solid‐phase peptide synthesis were developed: a chemoenzymatic route, involving L ‐threonine aldolase, and an enantioselective chemical route; these led to α,γ‐diamino‐β‐hydroxybutanoic acids in diastereoisomerically mixed and enantiopure forms, respectively. Incorporation of the 1,2‐amino alcohol linker into the backbone of a peptide generated a conditional peptide that was rapidly cleaved at very low concentrations of sodium periodate. This cleavable peptide ligand was applied in the generation of MHC exchange reagents for the detection of antigen‐specific T cells in peripheral blood cells. The extremely low concentration of periodate required to trigger MHC peptide exchange allowed the co‐oxidation of methionine and disulfide residues to be avoided. Conditional MHC reagents hypersensitive to periodate can now be applied without limitations when UV irradiation is undesired or less practical.     

三氟氯氰菊酯对小鼠肝、肾的影响

[目的]以三氟氯氰菊酯对小鼠的蓄积毒性试验为基础,通过观察三氟氯氰菊酯染毒对肝、肾组织病理学改变及肝组织生化指标等的影响来评价其对小鼠肝、肾的毒性.[方法]肝、肾组织经固定液固定后,常规脱水,石蜡包埋,切片,染色,光镜下观察病理改变.检测肝组织生化指标:酸性磷酸酶(ACP)、碱性磷酸酶(AKP)、乳酸脱氢酶(LDH)、超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GSH-PX)活性测定.以上酶指标均采用南京建成生物工程研究所试剂盒所提供的方法测定.[结果]蓄积毒性试验组中,肝脏切片有崩解现象,为局灶性坏死,其余肝部位无异常;肾脏切片为局灶性坏死程度严重,此种病变多见于肾皮质细胞,髓质细胞无异样变化.试验组小鼠体质量与对照组相比增重减少,且有极显著差异(P＜0.01).AKP无显著差异(P＞0.05),ACP、LDH、SOD存在显著差异(0.01＜P＜0.05),GSH-PX存在极显著差异(P＜0.01),这说明三氟氯氰菊酯对小鼠肝脏有一定的影响.[结论]试验研究表明三氟氯氰菊酯为明显蓄积物质,且对小鼠肝、肾有严重损伤.     

Fixation of a tetraethylene pentamine dye on cotton and silk by bifunctional crosslinkers

Four crosslinkers were synthesised by the reaction of 1,3,5-trichloro-2,4,6-triazine and polyethylene glycol. Their structures were confirmed by Fourier transform infrared spectra and mass spectra. A tetraethylene pentamine dye was crosslinked to cotton and silk via covalent bonds by the crosslinking dyeing process. The effects of pH, temperature, concentration and the chain length of the crosslinkers on the dye fixation were investigated in detail. The fixation of the dye using the crosslinkers on cotton and silk was >97%, and the infrared spectra of cotton, the dyed cotton and the crosslinked dyed one were compared with each other, which indicated that a covalent bond had been formed between the crosslinking dyes and fibres through the crosslinkers.     

Effect of different crosslinkers on properties of melamine formaldehyde‐furfuryl alcohol copolymer/montmorillonite impregnated softwood (Ficus hispida)

Melamine formaldehyde‐furfuryl alcohol (MFFA) copolymer was prepared and impregnated into softwood Ficus hispida in combination with crosslinking agent and montmorillonite (MMT) under vacuum condition. Different crosslinkers namely n‐methylol acrylamide, (NMA), 2‐hydroxyethyl methacrylate (HEMA) and 1,3‐dimethylol‐4,5‐dihydroxyethyleneurea (DMDHEU) were used for evaluation of properties of the prepared composites. Nuclear magnetic resonance (NMR) and fourier transform infrared spectroscopy (FTIR) studies confirmed the formation of MFFA copolymer, NMA, and DMDHEU crosslinkers. X‐ray diffractometry (XRD) and FTIR studies were used to characterize the nanocomposites. The incorporation of MMT decreased the crystallinity of wood composites as revealed by XRD study. Maximum interaction was found in wood samples treated with MFFA/(NMA+HEMA+DMDHEU)/MMT as shown by FTIR study. The incorporation of MMT into the wood polymer composite was revealed by transmission electron microscopy study. Thermal stability and flammability were checked by thermogravimetric analyzer and limiting oxygen index instrument. Wood treated with MFFA, blended crosslinker and MMT exhibited higher dimensional stability, lower water uptake (%), enhanced chemical resistance, and better mechanical properties (flexural, tensile, and hardness). SEM study indicated the presence of polymer and MMT in the void spaces of wood. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Laboratory scale study on rheological behavior,morphological and structural properties of crosslinked polyacrylamide composite hydrogels embedded with date seed powder

Incorporation of biofillers in polymeric hydrogels has continued to receive great attention in recent times because of their excellent properties. In this study, polyacrylamide (PAM) and polyethyleneimine (PEI) were used to develop novel composite hydrogels filled with date seed powder (DSP) via chemical crosslinking technique. Pristine PAM/PEI hydrogel and PAM/PEI‐DSP hydrogels at various DSP loadings were fabricated and subjected to gelation at 40°C for 24 h. The impact of various DSP loadings on the hydrogel samples developed was investigated using hybrid rheometer, SEM, XRD, and FTIR instruments, respectively. Rheological measurements confirmed the viscoelastic responses of the neat PAM/PEI hydrogel and the PAM/PEI‐DSP hydrogels reinforced with various DSP contents (0.8, 2.4, and 4 wt %). The dynamic strain, dynamic frequency and time sweep tests demonstrated that PAM/PEI‐DSP hydrogels were slightly more elastic than the virgin PAM/PEI hydrogel. The SEM characterization revealed the surface micrographs of the neat PAM/PEI hydrogel and the PAM/PEI‐DSP hydrogels at different DSP loadings to be smooth, homogeneous, and dense. Besides, the SEM micrographs supported the incorporation of DSP in the PAM/PEI‐DSP hydrogel samples. XRD analysis showed that the structures of neat PAM/PEI hydrogel and PAM/PEI‐DSP hydrogels filled with various DSP contents were predominantly amorphous while FTIR results confirmed the functional groups and evidence of crosslinking in the neat PAM/PEI hydrogel and the PAM/PEI‐DSP hydrogels embedded with different DSP contents. It is believed that these new hydrogels have huge development potentials and promising future in wastewater treatment and removal of heavy metal ions in aqueous solutions. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42110.     

Determination of Optimum Conditions and the Kinetics of Methanol Oxidation

In this study, the catalytic oxidation of methanol to formaldehyde was investigated in a laboratory‐scale fixed‐bed catalytic reactor, under a large number of different conditions. Iron‐molybdate catalysts supported by silica or alumina with a molybdenium/iron (Mo/Fe) ratio of 1.5, 3 and 5 were studied for the gas phase reaction. In order to obtain the optimum conditions, six different temperatures in the range of 250–375 °C and three different space times of 50.63, 33.75 and 20.25 g/(mol/h) were investigated. After determining the optimum conditions for this reaction, experiments aimed at understanding the reaction kinetics, were carried out. These experiments were performed on the catalyst favoring the formation of formaldehyde, which has a (Mo/Fe) ratio of 5 on a silica support. Seven reaction models derived by the mechanisms cited in the literature were tested to elucidate the kinetics of the reaction and the surface reaction controlling model was found to be the most suitable reaction mechanism.     

Preparation and performance of thermosensitive poly(N‐isopropylacrylamide) hydrogels by frontal photopolymerization

In this study, frontal photopolymerization was applied to the fabrication of thermosensitive poly(N‐isopropylacrylamide) (PNIPAm) hydrogels. The influence of experimental conditions and reactant components on the feature of the polymerization front was investigated. The morphology of the samples indicated the successful preparation of PNIPAm hydrogels. The mechanical properties and thermal stability of the obtained hydrogels are discussed. The results indicated that the performance of the hydrogels is related to their microstructure and the type of crosslinkers. The swelling behavior and drug delivery ability were determined under different temperature conditions. The hydrogels exhibit a classical thermoresponsive behavior, which was also demonstrated by the DSC results. Therefore, frontal photopolymerization can be an alternative method for the preparation of PNIPAm hydrogels under mild conditions. © 2019 Society of Chemical Industry     

Photo-crosslinking: An Emerging Chemical Tool for Investigating Molecular Networks in Live Cells

Studying protein–protein interactions (PPIs) is useful for understanding cellular functions and mechanisms. Evaluating these PPIs under conditions as similar as possible to native conditions can be achieved using photo-crosslinking methods because of their on-demand ability to generate reactive species in situ by irradiation with UV light. Various fusion tag, metabolic incorporation, and amber codon suppression approaches using various crosslinkers containing aryl azide, benzophenone, and diazirines have been applied in live cells. Mass spectrometry and immunological techniques are used to identify crosslinked proteins based on their capture transient and context-dependent interactions. Herein we discuss various incorporation methods and crosslinkers that have been used for interactome mapping in live cells.     

Study on short glass fiber‐reinforced poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate) composites

Biobased non‐fossil polyester poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate) (P3/4HB) containing 4.0 mol % 4‐hydroxybutyrate (4HB) was melt‐mixed with short glass fibers (SGF) via a co‐rotating twin‐screw extruder. The compositing conditions, average glass fiber length and distribution, thermal, crystallization, and mechanical properties of the P3/4HB/SGF composites were investigated. Calcium stearate, two kinds of paraffin wax and modified ethylene bis‐stearamide (TAF) were investigated as lubricants for the P3/4HB/SGF composites. It revealed that TAF is the most efficient lubricant of the P3/4HB/SGF composites. Coupling agents 2,2′‐(1,3‐phenylene)bis‐2‐oxazoline (1,3‐PBO) and pyromellitic dianhydride (PMDA) were used as end‐group crosslinkers to reduce the degradation of P3/4HB and increase the mechanical properties of the P3/4HB/SGF composites. It showed that 1,3‐PBO is the efficient coupling agent. The optimum condition of the P3/4HB/SGF composites is 1.5 phr TAF, 1.0 phr 1,3‐PBO, and 30 wt % glass fiber content. And the maximum of tensile strength, tensile modulus, and impact strength of the composites is 3.7, 6.6, 1.8 times of the neat P3/4HB polymer, respectively. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Non-Dispersive Solvent Extraction and Stripping of Neodymium (III) using a Hollow Fiber Contactor with TODGA as the Extractant

Membrane based non-dispersive solvent extraction (NDSX) of Nd(III) from aqueous nitric acid medium was carried out using a commercial liquid-liquid extraction system consisting of an extra-flow hollow fiber module with about 10,000 microporous hydrophobic polypropylene capillaries with an effective surface area of 1.4 m². The NDSX operation was carried out by pumping about 1 g/L Nd(III) solutions at a fixed nitric acid concentration of 3.57 M through the tube side and organic solvent (tetra-n-octyl-3-oxapentane-diamide (TODGA) in normal paraffin hydrocarbon (NPH)) through the shell side of the hollow fiber capillaries. NDSX studies were performed under different hydrodynamic conditions and the overall mass transfer was evaluated under counter-current flow conditions. Conditions for quantitative extraction and stripping were also identified. Reproducibility of the results from multiple runs was found to be excellent after five different identical runs.     

Combustion characteristics of candles made from hydrogenated soybean oil

Hydrogenated soybean oil, referred to as soywax by candle makers, is a renewable and biodegradable alternative to paraffin wax in candle manufacturing. Soywax was investigated for its tendency to produce soot as well as potentially harmful organic volatiles (acrolein, formaldehyde, and acetaldehyde) during combustion. Beeswax and paraffin candles were used as references. A considerable amount of soot was produced from the combustion of paraffin candles, but little or none was observed from soywax candles. Compared to paraffin candles, soywax candles burned at a significantly slower rate and required less air. Small amounts of formaldehyde were detected and quantified in the fumes of burning paraffin candles. However, formaldehyde, peaks found in the chromatograms of soy- and beeswax candles were similar to or slightly higher than that of the blank. Since soywax candles exhibited burning properties similar to those of beeswax candles, soywax shows promise in candle applications.     

Synthesis and characterization of reinforced acrylic‐based superabsorbents crosslinked with divinylbenzene

A series of superabsorbent polymers were synthesized by an inverse suspension polymerization, with potassium persulfate as the initiator, Span60 as the dispersant, and N,N′‐methylene bisacrylamide (BIS) and divinylbenzene (DVB) as multiple crosslinkers. The synthesis conditions, including the amount of dispersant, concentration of crosslinkers, oil‐to‐water phase ratio (O/W) of the polymerization system, total monomer concentration, and acrylamide (AM) content were studied. The results indicated that there were optima for the following properties: BIS crosslinker concentration (0.075 wt %), O/W (3 : 1), total monomer concentration (37.5 wt %), and AM content (5 wt %). In addition, the particle size had a significant influence on the absorption speed, and the absorption speed increased with decreasing particle size. In comparison with the conventional sample crosslinked only by BIS, the superabsorbent with the same particle size but crosslinked by multiple crosslinkers had the higher absorption rate because of surface crosslinking. It also showed that the salt resistance and antihydrolyzing property of the superabsorbent crosslinked by multiple crosslinkers (BIS and DVB) were enhanced, which was also attributed to surface crosslinking by DVB. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1594–1600, 2006     

Equilibrium and Kinetics of the Extraction of Propionic Acid Using Tri‐n‐Octylphosphineoxide

Organophosphorous compounds have been widely used in inorganic analysis for the extraction and separation of inorganic acids or metal species. Since these compounds can form hydrogen bonds to proton donors, they can also be used for the extraction of acidic organic compounds. Therefore, the reactive extraction of propionic acid using tri‐n‐octylphosphine oxide (TOPO) in hexane was studied. Equilibrium and kinetics experiments were performed. The extraction of propionic acid using n‐heptane, light liquid paraffin, heavy liquid paraffin and hexane was studied and hexane was found to be most suitable diluent. The equilibrium complexation constant for the propionic acid‐TOPO complex was determined to be 0.702 m³/kmol. The extraction was found to be first order in propionic acid and first order in TOPO with the overall rate constant as 46.91 (m³/kmol)²/s.     

Enhancement of Solute Release From Chitosan Scaffold With Embedded Submillimeter Voids

Chitosan scaffold has potential use in the controlled release of drugs, and as 3-D structure for the formation of tissue matrix. This article describes the solute release behavior of chitosan scaffold that bears embedded voids of submillimeter dimensions. Formaldehyde and glyoxal were considered as crosslinkers, and alcohol ethoxylate was used as the surfactant. Nitrogen gas was bubbled in a fluidic arrangement to generate an ensemble of self-aligned bubbles in chitosan, prior to the crosslinking. The crosslinked gel was dried in a vacuum oven, and subsequently, the absorption capacity of the scaffold in PBS buffer was estimated. The type of crosslinker significantly affected the absorption capacity of the scaffold. The dimensions of the voids immediately after the cross-linking of gel, and also after complete drying were obtained using a digital microscope and a scanning electron microscope respectively. Two levels of porosity are evident from these images. The smaller pores were intrinsically provided by the gel matrix. The larger ones were induced by the fluidic arrangement. The porosity of the gel was measured gravimetrically. The uptake of Vitamin B-12 was found significantly higher when formaldehyde was used as crosslinker instead of glyoxal. The release of Vitamin B-12 in PBS buffer on a shaker was studied. For comparison, the experiment was repeated with a scaffold that did not have any embedded void. The enhancements in the release of Vitamin B-12 due to the presence of voids are estimated in this article. The bubbles, placed in more than one layer, enhanced the porosity and the ability to absorb Vitamin B-12 further.