Proportion Of Monomers Research Articles

Preparation and application of mixed-mode capillary polymer monolithic column

Based on the diversity of the retention mechanism, mixed-mode capillary monolithic columns have broad application prospect. In this work, a novel capillary polymer monolithic column was prepared with [2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide (SPE) as monomer, ethylene dimethacrylate (EDMA) as crosslinking agent, azobisisobutyronitrile (AIBN) as initiator and butylalcohol/1, 4-butanediol/water as ternary porogens. Under the optimized reaction conditions including the proportion of monomer and porogens, amount of initiator, reaction temperature and polymerization time, the monolithic column showed good mechanical strength up to 10 MPa, high permeability of 2. 17 x 10(-14) m2 and good repeatability. The peak area RSDs of column-to-column and batch-to-batch reproducibility were 1.0% and 4.6%, respectively. Finally, the capillary monolithic column was evaluated with polar and non-polar test mixtures. It showed hydrophilic interaction under high organic phase while hydrophobic interaction under low organic phase, indicating it a mixed-mode monolithic column.

Pathway and Mechanism of pH Dependent Human Hemoglobin Tetramer-Dimer-Monomer Dissociations

Hemoglobin dissociation is of great interest in protein process and clinical medicine as well as in artificial blood research. However, the pathway and mechanisms of pH-dependent human Hb dissociation are not clear, whether Hb would really dissociate into monomers is still a question. Therefore, we have conducted a multi-technique investigation on the structure and function of human Hb versus pH. Here we demonstrate that tetramer hemoglobin can easily dissociate into dimer in abnormal pH and the tetramer → dimer dissociation is reversible if pH returns to normal physiological value. When the environmental pH becomes more acidic (<6.5) or alkaline (>8.0), Hb can further dissociate from dimer to monomer. The proportion of monomers increases while the fraction of dimers decreases as pH declines from 6.2 to 5.4. The dimer → monomer dissociation is accompanied with series changes of protein structure thus it is an irreversible process. The structural changes in the dissociated Hbs result in some loss of their functions. Both the Hb dimer and monomer cannot adequately carry and release oxygen to the tissues in circulation. These findings provide a comprehensive understanding on the pH-dependent protein transitions of human Hb, give guideline to explain complex protein processes and the means to control protein dissociation or re-association reaction. They are also of practical value in clinical medicine, blood preservation and blood substitute development.

Research of Synthesis and Heat Resistance on Lactic Acid-Styrene-Maleic Anhydride Copolymer

The polymerization process and heat resistance of lactic acid-styrene-maleic anhydride copolymer was studied. Lactic acid-polystyrene-maleic anhydride copolymer was prepared with styrene, maleic anhydride and lactic acid by melt copolymerization. Its structure was characterized by Infrared Spectrum (IR), and the thermal properties were tested by Differential Scanning Calorimetry (DSC) and Thermo Gravimetric Analyzer (TGA). The paper research on the effect of the proportion of different monomer and the polymerization process on the heat resistance mainly. The optimum conditions for the synthesis were determined by means of experiment: the content of catalyst was 0.5(wt%), the ratio of styrene-maleic anhydride and lactic was 0.6g/10g, at 170 °C. for 5 h. The results showed that the glass transition temperature (Tg) of the copolymer increased by 26.0°C.and the 5% weight-loss temperature of it increased by 25.0°C compared with pure polylactic acid.

Poly(azobenzene acrylate-co-fluorinated acrylate) Spin-Coated Films: Influence of the Composition on the Photo-Controlled Wettability

The wetting properties of spin-coated films of copolymers based on azobenzene and fluorinated units have been investigated. The copolymers, denoted as poly(Azo-co-AcRf6), have been synthesized by free-radical polymerization of different proportions of acrylate monomers bearing either an azobenzene group or a semifluorinated side chain. The UV-visible spectroscopy analysis of the different spin-coating films through a cycle of UV and visible light irradiation indicates the reversible trans-cis isomerization of azobenzene groups. Simultaneously, atomic force microscopy shows that surface roughness does not exceed 1 nm. Advancing and receding contact angles of water and diiodomethane have been measured before and after UV photoirradiation of the different surfaces. In particular, a decrease in the advancing contact angles has been observed upon trans-cis isomerization of azobenzene groups. Switching variations up to 50° have been evidenced without any introduction of surface nanoroughness. Surface free-energy evaluations have been deduced from these measurements, including dispersive and polar components. The results show that, through surface composition and UV photoirradiation, a large range of surface free-energies can be obtained, from 7 to 46 mN·m(-1).

Enhancement of enzymatic saccharification of sugarcane bagasse by liquid hot water pretreatment

Lignocellulosic biomass can be utilized to produce promising biofuels. In this study, liquid hot water pretreatments were performed to break the intricate structure of sugarcane bagasse, which resists the enzyme accessibility to cellulose. The effects of temperatures and times on the hemicellulose degradation (including the yields of pentoses and hexoses, the proportion of monomers and oligosaccharides, as well as limited inhibitors) and cellulose enzymatic digestibility were evaluated. The results indicated that the maximum xylose yields (combined 3.85 g xylose and 13.21 g xylo-oligosaccharides per 100 g raw material) in prehydrolyzate liquid were obtained at 180 °C and 30 min. Due to the effective removal of hemicellulose, the maximum glucose yield in enzyme hydrolyzate reached 37.27 g per 100 g raw material, representing 90.13% of glucose in the sugarcane bagasse. The maximal total sugars yield (combined prehydrolyzate and enzymatic hydrolyzate) were 53.65 g based on 100 g raw material.

PH‐ and Voltage‐Switchable Superhydrophobic Surfaces by Electro‐Copolymerization of EDOT Derivatives Containing Carboxylic Acids and Long Alkyl Chains

In order to produce pH- and voltage-switchable superhydrophobic surfaces, PEDOT derivatives containing various proportions of a EDOT monomer containing carboxylic groups (EDOT-COOH) and EDOT monomer-containing dodecyl chains (EDOT-O-H12) are elaborated. The surface morphology and roughness depend highly on the proportion of the monomers. Superhydrophobic properties are reached for a mol% of EDOT-COOH between 0 and 25%. It is possible to switch from superhydrophobic to hydrophilic (θ(water) until about 45°) by electrochemical reduction at low voltage (-1 V vs SCE) to remove the doping anions, following by treatment with NaOH to change the carboxylic groups into carboxylate. By elaborating smooth surfaces of each polymer, the effect of each treatment is reported. The reversibility of the reactions is also reported.

The combination of catechin and epicatechin callate from Fructus Crataegi potentiates beta-lactam antibiotics against methicillin-resistant staphylococcus aureus (MRSA) in vitro and in vivo.

Fructus crataegi (hawthorn) is the common name of all plant species in the genus Crataegus of the Rosaceae family. In the present study, three monomers of (+)-catechin (C), (−)-epicatechin gallate (ECg) and (−)-epigallocatechin (EGC) were isolated from the hawthorn under the guide of antibacterial sensitization activity. The bioactivity of the composite fraction in enhancing the antibacterial effect of oxacillin against methicillin-resistant Staphylococcus aureus (MRSA) was greater than that of the individual monomer of the hawthorn extract in vitro. Two-fold dilution and checkerboard methods were used to analyze antibacterial activity and screen for the combination and proportion of monomers with the best bioactivity. The result showed that C (128 mg/L) combined with ECg (16 mg/L) had the greatest effect and the combination also reduced the bacterial load in blood of septic mice challenged with a sublethal dose of MRSA, increased daunomycin accumulation within MRSA and down-regulated the mRNA expression of norA, norC and abcA, three important efflux pumps of MRSA. In summary, C and ECg enhanced the antibacterial effect of β-lactam antibiotics against MRSA in vitro and in vivo, which might be related to the increased accumulation of antibiotics within MRSA via suppression of important efflux pumps’ gene expression.

Folic acid-conjugated temperature and pH dual-responsive yolk/shell microspheres as a drug delivery system.

A facile and effective approach was developed to fabricate folic acid-conjugated temperature-sensitive hollow microspheres with movable pH-responsive cores for a targeted drug delivery system (DDS) via two-stage distillation precipitation polymerization. The yolk/shell structure of the microspheres obtained was revealed by transmission electron microscopy (TEM). Their monodisperse poly(methacrylic acid-co-ethyleneglycol dimethacrylate) (P(MAA-co-EGDMA)) microgel cores expressed obvious pH stimulus-response characteristics from Dynamical Light Scattering (DLS) analysis, and their functional crosslinked poly(N-isopropylacrylamide) (PNIPAM) shells exhibited obvious temperature stimulus-responses with diameters related to the degree of crosslinking and monomer proportion. Their independent temperature and pH dual-stimulus controlled release of drug molecules (using a model anti-cancer drug, doxorubicin (DOX)) was also investigated in simulated human body fluids. Meanwhile, the FA conjugated targeting temperature-sensitive hollow microspheres with pH-responsive cores expressed excellent biocompatibility on HepG2 cells. Consequently, the precise molecular targeting properties produced by the surface folic acid groups and the independent temperature and pH dual-stimulus responsive characteristics from the unique yolk/shell structure offers promise for cancer treatment.

Analysis of Flower Cuticular Waxes and Cutin Monomers

Here we describe procedures for the flower cuticular waxes extraction, modification and subsequent qualitative and quantitative analysis by gas-chromotography-mass spectrometry (GC-MS) and gas-chromotography with flame ionization detector (GC-FID), accordingly. To characterize flower cutin monomers two experimental setup are described: (i) analysis of enzymatically isolated cuticles in order to determine the relative proportions of cutin monomers; (ii) analysis of freeze-dried material for quantitative estimation of the cutin content. This report is an adaptation of the earlier published protocols developed for the chemical analysis of the cuticles in vegetative organs (Leide et al., 2007).

Structure, tensile properties and cytotoxicity assessment of sebacic acid based biodegradable polyesters with ricinoleic acid.

A new family of ricinoleic acid based polyesters was synthesized using catalyst free melt-condensation polymerization with sebacic acid, citric acid, mannitol and ricinoleic acid as precursors. The use of FT-IR and NMR characterisation techniques confirms the presence of ester linkages in the as-synthesized polymers. Depending on the precursor combination, their relative amount and the degree of curing, a broad range of elastic modulus (22-327 MPa) and tensile strength (0.7-12.7 MPa) can be obtained in the newly synthesized biopolymers. The polymers show rubbery behaviour at a physiological temperature (37 °C) and the contact angles of the synthesized polymers fall in the range of 42° to 71°, making them ideal substrates to study delivery of drugs through polymer scaffolds. The cytocompatibility assessment of the cured polymers confirmed good cell attachment and growth of smooth muscle cells (C2C12 myoblast cells). Importantly, oriented cell growth was observed after culturing myoblast cells for 3 days. The in vitro degradation in PBS indicates that the mild cured polymers follow a first order reaction kinetics and have degradation rate constants in the range of 0.009-0.038 h-1, depending on the relative proportions of monomers. Overall, the results of our study indicate that the physical properties can be tailored by varying the composition of the monomers and curing conditions in the newly developed polyesters. Hence, they may be used as potential substrates for tissue engineering scaffolds and for localized drug delivery.

Controlled experimental soil organic matter modification for study of organic pollutant interactions in soil

Interactions of organic pollutants with soil organic matter can be studied by adsorption of the pollutants on well-characterized soil samples with constant mineralogy but different organic matter compositions. Therefore, the objectives of the current study are establishing a set of different, well-characterized soil samples by systematic modifications of their organic matter content and molecular composition and prove these modifications by advanced complementary analytical techniques. Modifications were done by off-line pyrolysis and removal/addition of hot-water extracted organic fraction (HWE) from/to the original soil sample. Both pyrolysis-field ionization mass spectrometry (Py-FIMS) and synchrotron-based C- and N- X-ray absorption near-edge structure spectroscopy (XANES) were applied to investigate the composition of the soil organic matter. These complementary analytical methods in addition to elemental analysis agreed in showing the following order of organic matter contents: pyrolyzed soil<soil residue<original soil<soil+3 HWE<soil+6 HWE<HWE. The addition of HWE to the soil sample increases the relative proportions of carbohydrates, N-containing heterocyclic compounds and peptides, and decreases the relative proportions of phenols, lignin monomers and dimers, and lipids. The most abundant organic compound classes in the pyrolyzed sample are aromatics, aliphatic nitriles, aldehydes, five- and six-membered N-containing heterocyclic compounds, and aliphatic carboxylic acids. It can be expected that removal or addition of HWE, that mimic biomass inputs to soil or soil amendments, change the binding capacity for organic pollutants less intensively than heat impact, e.g. from vegetation burning. It will be possible to interpret kinetic data on the pollutants adsorption by these original and modified soil samples on the basis of the bond- and element-specific speciation data through C-XANES and N-XANES and the molecular-level characterization through Py-FIMS. Finally, this combination of analytical techniques can be recommended for similar problems that require characterizing the bulk, non-extracted SOM instead of pre-selected compounds or compound classes.

Engineered synthetic polymer nanoparticles as IgG affinity ligands.

A process for the preparation of an abiotic protein affinity ligand is described. The affinity ligand, a synthetic polymer hydrogel nanoparticle (NP), is formulated with functional groups complementary to the surface presentation of the target protein. An iterative process is used to improve affinity by optimizing the composition and proportion of functional monomers. Since the polymer NPs are formed by a kinetically driven process, the sequence of functional monomers in the polymer chain is not controlled; only the average composition can be adjusted by the stoichiometry of the monomers in the feed. To compensate for this the hydrogel NP is lightly cross-linked resulting in chain flexibility that takes place on a submillisecond time scale allowing the polymer to "map" onto a protein surface with complementary functionality. In this study, we report a lightly cross-linked (2%) N-isopropyl acrylamide (NIPAm) synthetic polymer NP (50-65 nm) incorporating hydrophobic and carboxylate groups that binds with high affinity to the Fc fragment of IgG. The affinity and amount of NP bound to IgG is pH dependent. The hydrogel NP inhibits protein A binding to the Fc domain at pH 5.5, but not at pH 7.3. A computational analysis was used to identify potential NP-protein interaction sites. Candidates include a NP binding domain that overlaps with the protein A-Fc binding domain at pH 5.5. The computational analysis supports the inhibition experimental results and is attributed to the difference in the charged state of histidine residues. Affinity of the NP (3.5-8.5 nM) to the Fc domain at pH 5.5 is comparable to protein A at pH 7. These results establish that engineered synthetic polymer NPs can be formulated with an intrinsic affinity to a specific domain of a large biomacromolecule.

Extractable and non‐extractable proanthocyanidins of Nonpareil, Carmel, and Butte California almonds

Proanthocyanidin content may be underestimated due to the unextractable or “bound” fraction in polyphenol‐rich foods. We characterized the extractable and “bound” proanthocyanidins (PACs) in Nonpareil, Butte, and Carmel California almonds (n =3/genotype). Almonds were extracted and residues were further subjected to acid and base hydrolysis to yield additional PACs. PACs were quantified by normal phase HPLC as proanthocyanidin B2 equivalents. Base hydrolysis contributed 3 to 38% of total PAC content of almonds, mainly as monomers, dimers, and polymers. Acid hydrolysis did not yield additional PAC, but liberated an additional 60% polyphenols by the Folin method. The mean total PAC content of almond genotypes was 59 mg/100 g whole almonds. Nonpareil had the most total PACs, with 111 mg/100 g whole almonds. Butte almonds had the greatest relative proportion of monomers and dimers contributing ~50% to the PAC content. In contrast, trimers and greater oligomers contributed more than 70% of Nonpareil and Carmel PACs. Future analysis should consider the presence of “bound” polyphenols in almonds. Supported by the Almond Board of California.

Synthesis and Properties of Copolymer of &lt;i&gt;p&lt;/i&gt;-Hydroxybenzoic Acid and Sulfanilic Acid Using Horseradish Peroxidase

A novel copolymer of p-hydroxybenzoic acid and sulfanilic acid (pHBA-SAA copolymer) was synthesized by free radical copolymerization with horseradish peroxidase (HRP)/HB2BOB2B as initiator. The effects of the proportion of monomers, the amount of catalyst, reaction temperature and time on copolymer performance were investigated. The structure of the copolymer was characterized with FTIR, NMR and GPC. Shrinkage temperature (TBsB) of the leather tanned with the copolymer was 81.5°C. The thickness increment ratio of the retanned leather was 23.23% and meanwhile the retanned leather showed better softness and exceptionally good flexible. The results indicated that the graft copolymer has excellent retanning properties and particularly suited to be served as retannage substitute for chrome and resin retannages in making leather process.

Do membrane proteins cluster without binding between molecules?

Clustering is a basic event for the initiation of immune cell responses, and simulation analyses of clustering of membrane proteins have been performed. It was claimed that a cluster is formed by the self-assembly induced by protein dimerization with a high binding speed (Woolf and Linderman, Biophys. Chem. 104, 217-227, 2003). We examined the cluster formation with Monte Carlo simulation using two algorithms. The first was that simulation processes were divided into two substeps. All proteins were subjected to movement in the first substep, followed by reaction in the second substep. The second algorithm was that proteins were first selected to react and proteins which did not react were subjected to movement. The self-assembly induced by dimerization was simulated only with the second algorithm. In this algorithm, monomers dissociated from dimers do not move because these monomers are not selected for movement, and a large proportion of such monomers are selected to form dimers in the next step. The self-assembly was again simulated with the first algorithm containing the conditions that monomers dissociated from dimers did not move in the next movement substep. This algorithm seems to be far removed from natural conditions. Thus, it is inferred that the self-assembly induced by dimerization is unlikely in situ, and that some interaction between proteins is required for cluster formation. In contrast to algorithms in previous simulations, our results suggest that it is more appropriate that proteins move to the same direction for a while and reflect when the collision occurs.

The role of hydrogels with tethered acetylcholine functionality on the adhesion and viability of hippocampal neurons and glial cells

In neural tissue engineering, designing materials with the right chemical cues is crucial in providing a permissive microenvironment to encourage and guide neuronal cell attachment and differentiation. Modifying synthetic hydrogels with biologically active molecules has become an increasingly important route in this field to provide a successful biomaterial and cell interaction. This study presents a strategy of using the monomer 2-methacryloxyethyl trimethylammonium chloride (MAETAC) to provide tethered neurotransmitter acetylcholine-like functionality with a complete 2-acetoxy-N,N,N-trimethylethanaminium segment, thereby modifying the properties of commonly used, non-adhesive PEG-based hydrogels. The effect of the functional monomer concentration on the physical properties of the hydrogels was systematically studied, and the resulting hydrogels were also evaluated for mice hippocampal neural cell attachment and growth. Results from this study showed that MAETAC in the hydrogels promotes neuronal cell attachment and differentiation in a concentration-dependent manner, different proportions of MAETAC monomer in the reaction mixture produce hydrogels with different porous structures, swollen states, and mechanical strengths. Growth of mice hippocampal cells cultured on the hydrogels showed differences in number, length of processes and exhibited different survival rates. Our results indicate that chemical composition of the biomaterials is a key factor in neural cell attachment and growth, and integration of the appropriate amount of tethered neurotransmitter functionalities can be a simple and effective way to optimize existing biomaterials for neuronal tissue engineering applications.

The effect of monomer structures on photopolymerization kinetics and volume shrinkage behavior for plasma display panel barrier rib

AbstractBarrier rib manufactured by the photosensitive paste is the function structure of plasma display panels (PDPs) which is used to maintain the discharge space between two glass plates. As the most promising option for barrier rib preparation, the photosensitive paste contains binder polymer, monomers, photoinitiator, and barrier rib powder etc., all of which influenced the performance of barrier rib. Among all these components, monomers play a very important role in the formation process and resolution of barrier rib during of these components. In this work, double‐bond conversion, curing speed, content, volume shrinkage, and the best mixed proportion of monomers were investigated by Fourier transform infrared spectroscopy, density measurements, analog computation and orthogonal test. It was found that the high aspect ratio barrier rib could be produced based on the optimizing additives of components in the photosensitive paste. The height of barrier rib of about 220 μm could further decline the energy consumption of PDP effectively. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Biodegradable Polyesters and Polyamides From Difunctionalized Lauric and Coconut Fatty Acids

In this work, a major fatty acid from coconut oil was used as starting material in preparing biodegradable polymers. Thus, polyesters and polyamides from varying proportions of monomers, hydroxy- and amino- derivatives of lauric acid were synthesized. Initially, the derivatives were prepared by regioselective chlorination of lauric acid, in the presence of ferrous ions in strong acid medium. Subsequent hydroxylation and amination procedures yielded the hydroxy- and amino- derivatives of lauric acid. These monomers were polymerized in a reaction tube by simple polycondensation method at 220–230 °C for 6–8 h without catalyst. Molecular weight determination using –COOH by end group titration and gel permeation chromatography (GPC) gave an average molar mass of 3,000–5,000 g mol−1 with n = 15–25 monomer units. Thermal properties such as glass transition (Tg) and decomposition (Td) temperatures were obtained using differential scanning calorimetry (DSC). The same processes of synthesis and determinations above were applied to coconut fatty acids, derived from saponification of coconut oil, and resulted to very similar conclusions. A quick biodegradation assay against fungus Aspergillus niger UPCC 4219 showed that the polymers prepared are more biodegradable than conventional plastics such as polypropylene, poly(ethyleneterepthalate) and poly(tetrafluoroethylene) but not as biodegradable as cellulosic (newsprint) paper.

A novel ionic liquid monolithic column and its separation properties in capillary electrochromatography

A novel ionic liquid (IL) monolithic capillary column was successfully prepared by thermal free radical copolymerization of IL (1-vinyl-3-octylimidazolium chloride, ViOcIm +Cl −) together with lauryl methacrylate (LMA) as the binary functional monomers and ethylene dimethacrylate (EDMA) as the cross-linker in binary porogen. The proportion of monomers, porogens and cross-linker in the polymerization mixture was optimized in detail. The resulting IL-monolithic column could not only generate a stable reversed electroosmotic flow (EOF) in a wide pH range (2.0–12.0), but also effectively eliminate the wall adsorption of the basic analytes. The obtained IL-monolithic columns were examined by scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR). These results indicated that the IL-monolithic capillary column possessed good pore properties, mechanical stability and permeability. The column performance was also evaluated by separating different kinds of compounds, such as alkylbenzenes, thiourea and its analogues, and amino acids. The lowest plate height of ∼6.8 μm was obtained, which corresponded to column efficiency (theoretical plates, N) of ∼147,000 plates m −1 for thiourea. ILs, as a new type of functional monomer, present a promising option in the fabrication of the organic polymer-based monolithic columns in CEC.

Modification of carbon nanotubes with well-controlled fluorescent styrene-based polymers using the Diels–Alder reaction

A simple and single-step “grafting to” approach based on the Diels–Alder (DA) reaction is described to functionalize multi-wall carbon nanotubes (MWCNTs) with polystyrene (PSt). Thus, several fluorescent and furfuryl functionalized PSts, synthesized by the atom transfer radical polymerization (ATRP) of styrene, furfuryl methacrylate and low proportion of a fluorescent monomer, were covalently attached onto the pristine nanotubes. Furfuryl (diene) groups allowed the chemical attachment of the PSt polymer onto the as-synthesized MWCNTs by a DA reaction. On the other hand, the incorporation of fluorescent groups in the polymer has two main advantages. It permits to determine the attachment of the polymer onto the nanotubes and, in further applications, it will allow to follow the dispersion of these modified MWCNTs in a matrix. The efficiency of the functionalization was verified by FTIR, Raman spectroscopy, TEM, AFM and fluorescence techniques.