Hydroxyl End Research Articles

Cyclization assisted iterative growth method for synthesizing monodisperse polymers

A fast iterative growth method is reported to prepare monodisperse polymers assisted by a cyclization technique. This novel method uses a di-functional and a tri-functional compounds as monomer pairs. The di-functional monomer is designed to have an azide and a hydroxyl end groups, while the tri-functional monomer is designed to have an alkyne and a sym-dibenzo-1,5-cyclooctadiene-3,7-diyne containing two strained alkynes. One iterative cycle of this novel method is composed by four step reactions. First, the self-accelerating double-strain-promoted azide-alkyne click reaction is used to couple two monomers/oligomers having an azide and a hydroxyl end group pairs with one tri-functional monomer by reacting the azide and strained alkyne groups. This coupling reaction increases chain length and produces an elongated oligomers having two hydroxyl end groups and one alkyne group in the middle position of main-chain. Second, the esterification between anhydride and hydroxyl is used to modify the hydroxyl end groups to endow the elongated oligomers with two azide end groups. Third, copper(I)-catalyzed azide-alkyne click reaction is then used to ring-close the elongated oligomers by reacting the middle alkyne and one terminal azide groups to prepare a tadpole-shaped oligomers with one azide end group. Fourth, the 2,3-dichloro-5,6-dicyano-p-benzoquinone oxidized deprotection reaction is used to cleave the preset methoxybenzyl ether bond in the ring of the tadpole-shaped oligomers and rebuild an azide and a hydroxyl end group pairs for the elongated oligomers. The repetition of above iterative cycle can synthesize the monodisperse polymers with a fast chain-growth manner of 2n+1-1.

An ocular insert with zero-order extended delivery: Release kinetics and mathematical models

Ocular inserts (InEye®), were prepared based on two distinct formulations of PCL-PEG-PCL block copolymers – one with 33 % and the other with 24 % of PEG 600. Ring-open-polymerisation was used to link ε-caprolactone monomers to PEG hydroxyl end-groups. Molecular weight, PCL/PEG ratio, mass loss and swelling of different polymeric samples where determined.Based on the previously prepared block copolymers, ophthalmic inserts were assembled. These were prepared with an ellipsoidal shape by dripping melted polymer over a micro-tablet of moxifloxacin, used as drug model for this study, which therefore became entrapped in a central core coated with a polymer layer that functioned as a control-release barrier.The release kinetics of the model drug revealed a strong dependence on the PEG percentage on the polymer. Inserts’ size and the amount of drug immobilized also had an important effect on the drug release profile. All release profiles followed a zero-order pattern, with 95 % of the drug being release at a constant rate.With drug releases varying from 20 to 200 days, and no initial burst, InEye® performance is unique among drug delivery systems and seems to be a very promising new formulation technology for preparing tailor-made ophthalmic inserts for prolonged and constant release of drug, which is needed for chronic diseases such as glaucoma, where compliance to treatment is essential for preventing optic-nerve lesions.

A functionalized ionic liquid as the next‐generation nano‐lubricant

AbstractIonic liquids (ILs) have attracted intensive research interest due to their outstanding physiochemical properties. However, comprehensive design is necessary for targeted applications and has rarely been conducted. As a result, the industry‐scale application of ILs is still very limited. In this academia–industry collaborative research among the University of Pittsburgh, Virginia Tech. University, and Seagate Technology LLC, we report the design, synthesis, molecular dynamics (MD) simulation, and characterization of a nanometer‐thick IL, which contains abundant fluorinated segments and a hydroxyl endgroup, as the next‐generation nano‐lubricant for hard disk drives (HDDs). The lab‐ and industry‐level testing results indicate that the IL lubricant performs significantly better than the state‐of‐the‐art lubricant, that is, perfluoropolyether (PFPE) that has been utilized for three decades in the HDD industry in two key functions: thermal stability and fly clearance. Meanwhile, the IL lubricant also shows excellent lubricity and durability. The outstanding performance of the IL has been attributed to its unique molecular structure on the solid substrate, which is supported by MD simulation results. Our work establishes the IL as a promising candidate among the next‐generation media lubricants in HDD industry. Meanwhile, the finding obtained here has important implications in many other applications involving nano‐lubricants.

Characterisation of end groups of hydroxy-functionalised scl-PHAs prepared by transesterification using ethylene glycol

Polyhydroxyalkanoates (PHAs) are a family of biodegradable polyesters with good potential in applications ranging from packaging to implants. The synthesis of block copolymers based on PHAs is one approach to tailoring these physical properties. This work considers the transesterification and end-group characterisation of hydroxy‑terminated PHAs for the chemical synthesis of PHA-based block copolymers. There is currently incomplete knowledge of the relative amounts of the different end-groups in the as-produced materials. Further, the reported hydroxy‑terminated PHAs have relatively low molecular weights (Mn < 4 kDa); hydroxy‑terminated PHAs of intermediate molecular weights (Mn > 20 kDa) - which are more favourable as building blocks for industrially relevant high molecular weight PHA - have not yet been fully characterised for use in such applications, to our knowledge. Here, a more comprehensive strategy for the preparation and characterisation of hydroxy‑terminated PHAs of intermediate molecular weights was applied. Hydroxy-functionalised PHAs were produced via transesterification of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) of differing 3HV contents and with narrow compositional distribution, followed by purification through solvent processing. The functionalised PHAs and reaction by-products were then characterised using FT-IR, 1H-NMR, 13C-NMR, 31P-NMR, GPC and DSC analyses, allowing the determination of the nature and distribution of the end groups. It was found that transesterification does indeed generate both primary and secondary hydroxyl end-groups, while original PHBV materials (PHBpre-sol) had only secondary hydroxyl end groups present. 41% of hydroxy‑functionalised PHBV (PHBtr-sol-D) were likely terminated with either crotonic groups or carboxylic acids. Further, the analysis showed that a proportion of commercial and laboratory derived PHBVs (PHBpre-sol and PHBVpre-sol) was likely dicarboxylic acid-terminated.

Competition between CO2-philicity and Mixing Entropy Leads to CO2 Solubility Maximum in Polyether Polyols.

In carbon dioxide-blown polymer foams, the solubility of carbon dioxide (CO2) in the polymer profoundly shapes the structure and, consequently, the physical properties of the foam. One such foam is polyurethane—commonly used for thermal insulation, acoustic insulation, and cushioning—which increasingly relies on CO2 to replace environmentally harmful blowing agents. Polyurethane is produced through the reaction of isocyanate and polyol, of which the polyol has the higher capacity for dissolving CO2. While previous studies have suggested the importance of the effect of hydroxyl end groups on CO2 solubility in short polyols (<1000 g/mol), their effect in polyols with higher molecular weight (≥1000 g/mol) and higher functionality (>2 hydroxyls per chain)—as are commonly used in polyurethane foams—has not been reported. Here, we show that the solubility of CO2 in polyether polyols decreases with molecular weight above 1000 g/mol and decreases with functionality using measurements performed by gravimetry-axisymmetric drop-shape analysis. The nonmonotonic effect of molecular weight on CO2 solubility results from the competition between effects that reduce CO2 solubility (lower mixing entropy) and effects that increase CO2 solubility (lower ratio of hydroxyl end groups to ether backbone groups). To generalize our measurements, we modeled the CO2 solubility using a perturbed chain-statistical associating fluid theory (PC-SAFT) model, which we validated by showing that a density functional theory model based on the PC-SAFT free energy accurately predicted the interfacial tension.

A facile route to improve compatibilization of low density polyethylene/poly (ε-caprolactone) blends

Low density Polyethylene (designated hereafter as “PE”) is known for its inactivity, durability and resistance to degradation. For this reason adding pro-oxidants as additives in PE matrix could be efficient to elaborate a material designated as Ox-PE, exhibiting chemical reactivity. This modification could lead to an enhancement of compatibility between Ox-PE and other functionalized polymers. This approach has been exploited in this report to elaborate blends of Ox-PE with poly (ε-caprolactone) (PCL), a biodegradable polymer. Fourier Transform InfraRed spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and thermal characterization by DSC, TGA were applied to investigate structural and thermal properties of PE/PCL (75/25 wt%/wt%) blends, compatibilized with 1 Phr and 5 Phr of Ethylene-co-Glycidyl MethAcrylate (EGMA) copolymer or with a Ox-PE/PCL mixture.Structural observations of the PE75/PCL25 blend by SEM revealed a phase separated morphology indicating incompatibility between PE and PCL. This was also confirmed by FTIR spectroscopy where no changes were noticed concerning the characteristic bands of either PE or PCL. Incorporating EGMA in the PE75/PCL25 blend resulted in reduced particle sizes of the dispersed PCL phase in the PE matrix confirming the reaction of epoxy groups of EGMA with hydroxyl end-groups of PCL at the interface. Regarding the thermal behavior, all PE/PCL blends exhibited an intermediate response between that of PE and PCL homopolymers. Interestingly, a high degree of compatibility was achieved for the Ox-PE75/PCL25 blend, together with a lower thermal stability compared to PE75/PCL25.

Aqueous Dispersion of Carbon Nanomaterials with Cellulose Nanocrystals: An Investigation of Molecular Interactions.

Dispersing carbon nanomaterials in solvents is effective in transferring their significant mechanical and functional properties to polymers and nanocomposites. However, poor dispersion of carbon nanomaterials impedes exploiting their full potential in nanocomposites. Cellulose nanocrystals (CNCs) are promising for dispersing and stabilizing pristine carbon nanotubes (pCNTs) and graphene nanoplatelets (pGnP) in protic media without functionalization. Here, the underlying mechanisms at the molecular level are investigated between CNC and pCNT/pGnP that stabilize their dispersion in polar solvents. Based on the spectroscopy and microscopy characterization of CNCpCNT/pGnP and density functional theory (DFT) calculations, an additional intermolecular mechanism is proposed between CNC and pCNT/pGnP that forms carbonoxygen covalent bonds between hydroxyl end groups of CNCs and the defected sites of pCNTs/pGnPs preventing re-agglomeration in polar solvents. This work's findings indicate that the CNC-assisted process enables new capabilities in harnessing nanostructures at the molecular level and tailoring the performance of nanocomposites at higher length scales.

MODIFICATION OF ALKYD RESINS WITH FUNCTIONALIZED DIENE LIQUID RUBBERS TO CREATE POLYMER COATINGS WITH IMPROVED PROPERTIES

Modification of existing paints and varnishes based on alkyd and melamine alkyd resins as well as creation of new film formers with the help of functionalized oligomers in order to improve the properties of materials during their operation was carried out. Liquid oligobutadiene rubber with end hydroxyl groups, HTPB trend mark was used . Pentaphthalic varnish PF-060 and melamine-formaldehyde resin K-421-02 was modified by triisocyanate oligobutadiene rubber based on trimethylolpropane and isophorone diisocyanate resin in different ratios. Analysis of the FTIR spectra of the developed paints and varnishes showed that the process of polymerization in a thin film in air forms a spatially crosslinked polymer and passes through the stage of formation of branched soluble polymers, followed by copolymerization of components with oxygen and formation of structured solid polymer. The optimal content of rubber in the modified paints and varnishes was estimated. For alkyd varnish PF-060 it equals 10 wt.% and for melamine-formaldehyde resin K-421-02 is in the range 7-10 wt.%. Addition of triisocyanate accelerates the drying process of coatings on air, high values of surface hardness, adhesion, resistance to bending and water absorption were also received. Developed modified paints and varnishes are characterized by increased viability, shelf life of more than 6 months, homogeneity. Proposed scheme allows to obtain transparent coatings with high physical and mechanical characteristics and can be recommended for practical use in various coating technologies.

Recombinant Expression, Purification and PEGylation of DNA Ligases

Reagent proteins such as DNA ligases play a central role in the global reagents market. DNA ligases are commonly used and are vital in academic and science research environments. Their major functions include sealing nicks by linking the 5'-phosphorylated end to a 3'-hydroxyl end on the phosphodiester backbone of DNA, utilizing ATP or NADP molecules as an energy source. The current study sought to investigate the role of PEGylation on the biological activity of purified recombinant DNA ligases. We produced two recombinant DNA ligases (Ligsv081 and LigpET30) using E. coli expression system and subsequently purified using affinity chromatography. The produced proteins wereconjugated to site specific PEGylation or non-specific PEGylation. FTIR and UV-VIS spectroscopy were used to analyze secondary structures of the PEG conjugated DNA ligases. Differential scanning fluorimetry was employed to assess the protein stability when subjected to various PEGylation conditions. In this study, both recombinant DNA ligases were successfully expressed and purified as homogenous proteins. Protein PEGylation enhanced ligation activity, increased transformation efficiency by 2-foldfor plasmid ligations and reduced the formation of protein aggregates. Taken together, site-specific PEGylation can potentially be explored to enhance the biological activity and stability of reagent proteins such as ligases.

Obtaining phthalate substituted post-consumer polyethylene terephthalate and its isothermal crystallization

Objects. Due to the polymer waste accumulation, the search for new directions for their utilization is urgent. Chemical recycling methods are of considerable interest, which allow one to obtain the original monomers or change the compositions of the copolymers. From the point of view of building a circular economy, a promising material is polyethylene terephthalate (PET), on the basis of which amorphous copolyesters can be obtained. The study aimed to analyze the simultaneous glycolysis and interchain exchange reactions of PET in the presence of the oligoethylene phthalate modifier with hydroxyl end groups and the study of isothermal crystallization of poly(ethylene phthalate-co-terephthalates) with different phthalate contents obtained in this way.Methods. Oligoethylene phthalate is synthesized by polycondensation. Poly(ethylene phthalateco-terephthalates) were obtained by the interaction of post-consumer PET with oligoethylene phthalate. The composition of the oligomer and copolymers was confirmed using Fourier-transform infrared spectroscopy, thermal characteristics and crystallization half-times were determined by differential scanning calorimetry.Results. In this work, the use of the post-consumer PET chemical recycling process, aimed at obtaining copolyesters under the influence of small modifier amounts was proposed. The process consisted in carrying out the combined interchain exchange and degradation with a complex oligoester different from PET. Poly(ethylene phthalate-co-terephthalate) copolymers were obtained via reaction of post-consumer poly(ethylene terephthalate) flakes and synthesized oligoethylene phthalate resin in the melt phase in the absence of catalyst. The effect of phthalate concentration in polymer on the isothermal crystallization of phthalate substituted poly(ethylene terephthalate) was estimated.Conclusions. The hypothesis about the possibility of using an oligoester modifier to obtain the PET-based copolymer at the high rate and without reducing the molecular weight to values characteristic of a monomer or oligomer has been confirmed. The process can be used to obtain random copolyesters based on post-consumer PET. The phthalate unit concentration increase is followed by decrease in the glass transition temperature, temperature and heat of fusion, and increase in crystallization half-times. Phthalate has a better ability to retard PET crystallization than 2-methyl-1,3-propanediol or furandicarboxylic acid, but is inferior to some of the other modifiers known.

Study of methods for obtaining unsaturated polyester resins based on recycled polyethylene terephthalate

In this work, methods for obtaining unsaturated polyester resins based on the products of chemical recycling of post-consumer polyethylene terephthalate with various agents are compared. A process based on simultaneous glycolysis and interchain exchange of polyethylene terephthalate and oligoethylene phthalate with hydroxyl end groups has been proposed. The advantages of this process are shown, including rapid obtaining polyester resins of high molecular weight and the lesser influence of side reactions and degradation reactions. The unsaturated resin with a weight average molecular weight of 3100 g/mol was obtained.

Making Invisible RNA Visible: Discriminative Sequencing Methods for RNA Molecules with Specific Terminal Formations.

Next generation sequencing of RNA molecules (RNA-seq) has become a common tool to characterize the expression profiles of RNAs and their regulations in normal physiological processes and diseases. Although increasingly accumulating RNA-seq data are widely available through publicly accessible sites, most of the data for short non-coding RNAs (sncRNAs) have been obtained for microRNA (miRNA) analyses by standard RNA-seq, which only capture the sncRNAs with 5′-phosphate (5′-P) and 3′-hydroxyl (3′-OH) ends. The sncRNAs with other terminal formations such as those with a 5′-hydroxyl end (5′-OH), a 3′-phosphate (3′-P) end, or a 2′,3′-cyclic phosphate end (2′,3′-cP) cannot be efficiently amplified and sequenced by standard RNA-seq. Due to the invisibility in standard RNA-seq data, these non-miRNA-sncRNAs have been a hidden component in the transcriptome. However, as the functional significances of these sncRNAs have become increasingly apparent, specific RNA-seq methods compatible with various terminal formations of sncRNAs have been developed and started shedding light on the previously unrecognized sncRNAs that lack 5′-P/3′-OH ends. In this review, we summarize the expanding world of sncRNAs with various terminal formations and the strategic approaches of specific RNA-seq methods to distinctively characterize their expression profiles.

Tailoring Oligomeric Plasticizers for Polylactide through Structural Control.

Structural variations (oligolactide segments, functionalized end groups, and different plasticizer cores) were utilized to tailor the performances of biobased plasticizers for polylactide (PLA). Six plasticizers were developed starting from 1,4-butanediol and isosorbide as cores: two monomeric (1,4-butanediol levulinate and isosorbide levulinate) and four oligomeric plasticizers with hydroxyl or levulinate ester end groups (1,4-butanediol-based oligolactide, isosorbide-based oligolactide, 1,4-butanediol-based oligomeric levulinate, and isosorbide-based oligomeric levulinate). Structural variations in plasticizer design were reflected in the thermal stability, plasticizing efficiency, and migration resistance. The monomeric plasticizer 1,4-butanediol levulinate decreased the glass-transition temperature of PLA from 59 to 16 °C and increased the strain at break substantially from 6 to 227% with 20 wt % addition. 1,4-Butanediol-based oligomeric levulinate exhibited better thermal stability and migration resistance, though the plasticizing efficiency was slightly lower (glass-transition temperature = 28 °C; strain at break = 202%). Compared to PLA films plasticized by plasticizers with flexible butanediol cores, those plasticized by plasticizers with rigid isosorbide cores exhibited higher Young’s modulus and thermal stability and lower plasticizing efficiency. Furthermore, plasticizers with levulinate ester end groups had improved thermal stability, plasticizing efficiency, and migration resistance compared to the corresponding plasticizers with hydroxyl end groups. Hence, a set of controlled structural variations in plasticizer design were successfully demonstrated as a potent route to tailor the plasticizer performances.

Improved melt strength and processability of impact copolymer polypropylene by introducing long‐chain branching via reactive extrusion with “ene” functionalized dendrimer

AbstractA generation two dendrimer (G2) having eight terminal double bonds has been prepared via esterification reaction from a dendritic precursor having eight hydroxyl end groups (G1). The reactive extrusion of impact co‐polymer polypropylene (ICP) with G1 resulted in improved processability while leading to enhanced melt strength in the case of linear low‐density polyethylene (LLDPE). G2 being an extension of G1, was melt grafted on ICP using a radical initiator to introduce long‐chain branching in the polymer backbone. The prepared samples were analyzed for their molecular weight distribution, thermal, rheological properties, and mechanical properties. Thermogravimetric analysis (TGA) and differential scanning calorimetric (DSC) analysis showed higher thermal stability and slightly higher crystallization temperature with grafting of G2 on ICP. The rheological analysis through melt flow index measurements and parallel plate rheometer indicated higher processability, melt strength, complex viscosity, and zero‐shear viscosity for ICP grafted with an optimized amount of G2. The presence of long‐chain branching was confirmed with an increase in activation energy for ICP modified with G2 as compared to neat ICP. Modified ICP samples retained their bulk mechanical properties as neat ICP.

Cellulose Acetate-g-Polycaprolactone Copolymerization Using Diisocyanate Intermediates and the Effect of Polymer Chain Length on Surface, Thermal, and Antibacterial Properties.

The need for biodegradable and biocompatible polymers is growing quickly, particularly in the biomedical and environmental industries. Cellulose acetate, a natural polysaccharide, can be taken from plants and modified with polycaprolactone to improve its characteristics for a number of uses, including biomedical applications and food packaging. Cellulose acetate-g-polycaprolactone was prepared by a three-step reaction: First, polymerization of ε-caprolactone via ring-opening polymerization (ROP) reaction using 2-hydroxyethyl methacrylate (HEMA) and functionalization of polycaprolactone(PCL) by introducing NCO on the hydroxyl end of the HEMA-PCL using hexamethyl lenediisocyanate(HDI) were carried out. Then, the NCO–HEMA-PCL was grafted onto cellulose acetate (using the “grafting to” method). The polycaprolactone grafted cellulose acetate was confirmed by FTIR, the thermal characteristics of the copolymers were investigated by DSC and TGA, and the hydrophobicity was analyzed via water CA measurement. Introducing NCO-PCL to cellulose acetate increased the thermal stability. The contact angle of the unreacted PCL was higher than that of cellulose acetate-g-PCL, and it increased when the chain length increased. The CA-g-PCL50, CA-g-PCL100, and CA-g-PCL200 showed very high inhibition zones for all three bacteria tested (E. coli, S. aureus, and P. aeruginosa).

Substantially Enhanced Stereocomplex Crystallization of Poly(L-lactide)/Poly(D-lactide) Blends by the Formation of Multi-Arm Stereo-Block Copolymers

Stereocomplex-type polylactide (SC-PLA) created by alternate packing of poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA) chains in a crystalline state has emerged as a growingly popular engineering bioplastic that possesses excellent hydrolytic stability and thermomechanical properties. However, it is extremely difficult to acquire high-performance SC-PLA products via melt-processing of high-molecular-weight PLLA/PDLA blends because both SC crystallites and homocrystallites (HCs) are competitively formed in the melt-crystallization. Herein, a facile yet powerful way was employed to boost SC formation by introducing trace amounts of some epoxy-functionalized small-molecule modifiers into the enantiomeric blends during reactive melt-blending. The results show that the SC formation is considerably enhanced with the in situ generation of multi-arm stereo-block PLA copolymers, based on the reaction between epoxy groups of the modifiers and hydroxyl end groups of PLAs. More impressively, it is intriguing to find that the introduction of only 0.5 wt% modifiers can induce exclusive SC formation in the blends upon isothermal and non-isothermal melt-crystallizations. The outstanding SC crystallizability might be attributed to the suppressing effect of such unique copolymers on the separation of the alternately arranged PLLA/PDLA chain segments in molten state as a compatibilizer. Furthermore, the generation of these copolymers does not result in a significant increase in melt viscosity of the blends. These findings suggest new opportunities for the high-throughput processing of SC-PLA materials into useful products.

Application of RtcB ligase to monitor self-cleaving ribozyme activity by RNA-seq.

Self-cleaving ribozymes are catalytic RNAs and can be found in all domains of life. They catalyze a site-specific cleavage that results in a 5' fragment with a 2',3' cyclic phosphate (2',3' cP) and a 3' fragment with a 5' hydroxyl (5' OH) end. Recently, several strategies to enrich self-cleaving ribozymes by targeted biochemical methods have been introduced by us and others. Here, we develop an alternative strategy in which 5' OH RNAs are specifically ligated by RtcB ligase, which first guanylates the 3' phosphate of the adapter and then ligates it directly to RNAs with 5' OH ends. Our results demonstrate that adapter ligation to highly structured ribozyme fragments is much more efficient using the thermostable RtcB ligase from Pyrococcus horikoshii than the broadly applied Escherichia coli enzyme. Moreover, we investigated DNA, RNA and modified RNA adapters for their suitability in RtcB ligation reactions. We used the optimized RtcB-mediated ligation to produce RNA-seq libraries and captured a spiked 3' twister ribozyme fragment from E.coli total RNA. This RNA-seq-based method is applicable to detect ribozyme fragments as well as other cellular RNAs with 5' OH termini from total RNA.

Investigation of the effects of solvent-mismatch and immiscibility in normal-phase × aqueous reversed-phase liquid chromatography

Comprehensive two-dimensional liquid chromatography (LC × LC) is an attractive separation technique that allows achieving high peak capacities and information on chemical correlations. Unfortunately, its application in industrial practice is still not widespread due to limiting factors such as complex method development, tedious method optimization and solvent-incompatibility (such as solvent-strength mismatch or immiscibility experienced during fraction transfer).A severe case of solvent-incompatibility is encountered in the comprehensive coupling of normal-phase LC and reversed-phase LC (NPLC × RPLC). NPLC × RPLC is considered a desirable LC × LC system, especially for the characterization of synthetic polymers, due to the high orthogonality of the two retention mechanisms. However, its experimental realization often suffers from solvent-injection effects in the RPLC dimension, such as peak-deformation, peak-splitting, or even unretained elution (“breakthrough”) of sample components. Such a decrease in performance or loss of retention is highly dependent on the types of solvents used.To explore the boundaries of solvent compatibility, we applied large-volume injections (LVI) of reference analytes (e.g. alkyl benzenes; ethoxylate and propoxylate polymers) dissolved in water-immiscible sample solvents, such as dichloromethane, n-hexane, and isooctane in fast water-based gradient RPLC separations (using methanol or acetonitrile as eluent). It was found that, when using highly aqueous initial gradient conditions, hydrophobic sample diluents were retained and eluted during the applied gradient. Depending on the relative retention of the retained diluent and the sample analytes, good chromatograms for LVI of immiscible solvents were obtained, comparable with injections under ideal conditions. The conclusions from injection experiments in aqueous RPLC were verified by coupling an NPLC system with a gradient from isooctane to tetrahydrofuran and an RPLC system with a gradient from water to acetonitrile in an online comprehensive NPLC × RPLC separation of a mixture of propoxylate polymers. The separation provided separation of the polymers based on their number of hydroxyl end-groups (NPLC) and oligomer chain-length (RPLC), without suffering from significant band-broadening effects due to solvent-mismatch upon injection in the second-dimension RPLC system.

Mycobacterial MMAR_2193 catalyzes O-methylation of diverse polyketide cores.

O-methylation of small molecules is a common modification widely present in most organisms. Type III polyketides undergo O-methylation at hydroxyl end to play a wide spectrum of roles in bacteria, plants, algae, and fungi. Mycobacterium marinum harbours a distinctive genomic cluster with a type III pks gene and genes for several polyketide modifiers including a methyltransferase gene, mmar_2193. This study reports functional analyses of MMAR_2193 and reveals multi-methylating potential of the protein. Comparative sequence analyses revealed conservation of catalytically important motifs in MMAR_2193 protein. Homology-based structure-function and molecular docking studies suggested type III polyketide cores as possible substrates for MMAR_2193 catalysis. In vitro enzymatic characterization revealed the capability of MMAR_2193 protein to utilize diverse polyphenolic substrates to methylate several hydroxyl positions on a single substrate molecule. High-resolution mass spectrometric analyses identified multi-methylations of type III polyketides in cell-free reconstitution assays. Notably, our metabolomics analyses identified some of these methylated molecules in biofilms of wild type Mycobacterium marinum. This study characterizes a novel mycobacterial O-methyltransferase protein with multi-methylating enzymatic ability that could be exploited to generate a palette of structurally distinct bioactive molecules.

A bio-based compatibilizer (ESO-g-S-HPG) to improve the compatibility and mechanical properties of CaCO3/HDPE composites

Compatibilizers allow for the combination of two materials with vastly different polarities. The dosage of most compatibilizers must be more than 5 wt% to be effective—an expensive high dosage level that changes polymer composite properties. Thus, in this study, renewable resource epoxidized soybean oil (ESO) was used as the raw material to synthesize the end-hydroxyl group bio-based compatibilizer ESO-g-S-HPG. The experimental results revealed that composites prepared with ESO-g-S-HPG had better mechanical properties (i.e., tensile strength, impact strength, and energy storage modulus) than those prepared with a commercially available compatibilizer (TA 1618). The addition of 1 wt% of ESO-g-S-HPG significantly enhanced the interfacial compatibility between the HDPE and CaCO3, making it a good candidate for application in the field of HDPE composite filling and reinforcement, as evidenced by the minimal voids revealed by the scanning electron microscopy results. The molecular dynamics simulation results revealed that hyperbranched compatibilizers can eliminate filler aggregation and enhanced filler-matrix interaction, yielding effects that are better than those of linear compatibilizers. The compatibilizer proposed here can be a useful material for the fabrication of the next generation of composites applied in diverse industrial fields.