A novel polymeric flocculant based on polyacrylamide grafted carboxymethylstarch

Novel functionalized polymeric flocculants based on polyacrylamide grafted carboxymethylstarch (CMS-g-PAM) have been successfully synthesized via conventional method (using ceric ammonium nitrate as free radical initiator, in an inert atmosphere) as well as by using microwave irradiation (‘microwave initiated’ synthesis). Under optimal grafting conditions, 50% grafting has been observed in case of the microwave irradiation based method and 47% grafting has been observed in case of the conventional process. The synthesized graft copolymers have been characterized by elemental analysis, FTIR spectroscopy, intrinsic viscosity measurement, molecular weight determination, ¹³C NMR spectroscopy and scanning electron micrograph (SEM); taking carboxymethylstarch (CMS) as reference. The effects of reaction parameters onto the percentage of grafting have been studied. Further, the applicability of these grafted polymers as flocculants for the treatment of municipal sewage wastewater has also been investigated.     

Synthesis, characterization and aqueous dispersion of dextran-g-poly(1,4-dioxan-2-one) copolymers

A novel biodegradable graft copolymer, dextran-g-poly(1,4-dioxan-2-one) (PODEX), was synthesized through the ring-opening polymerization (ROP) of 1,4-dioxan-2-one (PDO) onto a dextran backbone. Initially, dextran was silylated with 1,1,1,3,3,3-hexamethyldisilazane. The grafting from pathway was conducted with various (30–70) PDO/OH feed ratios to obtain PODEX copolymers with a various PPDO graft structures. Graft copolymers were characterized by FT-IR, ¹H and ¹³C NMR, DSC, TGA, and WAXD. Molecular weights of the PODEX copolymers (M_W: 94,700–117, 300 Da), glass transition temperature (−29 to −17 °C), melting temperature (82–100 °C), and crystallinity (32–40%) were increased with the content of PPDO. AFM observations revealed that polymeric micelles were spherical and uniform in morphology with around 30–58 nm diameter. Critical micelle concentration (CMC) of self-assembled system was significantly decreased from 3.2 to 1.09 mg/L with the increment of PPDO.     

Polyacrylamide grafted Agar: Synthesis and applications of conventional and microwave assisted technique

Polyacrylamide grafted Agar (Ag-g-PAM) has been successfully synthesized by conventional method and microwave assisted method. The former method employs ceric ammonium nitrate (CAN) as the free radical initiator while the latter uses the combination of ceric ammonium nitrate (CAN) and microwave irradiation. The synthesized graft copolymers have been characterized by elemental analysis (C, H, N, O and S), FTIR spectroscopy, intrinsic viscosity measurement and scanning electron micrograph (SEM); taking agar as a reference. Flocculation efficacy of synthesized graft copolymers was studied in kaolin suspension and in waste water through 'Jar test' procedure. In the present investigation, we have observed that polyacrylamide grafted agar synthesized by microwave assisted technique shows superior properties than conventional technique. These properties are reported in terms of intrinsic viscosity, flocculation efficacy and pollutant load reduction of waste water.     

Synthesis and characterization of amphiphilic polyphosphates with hydrophilic graft chains and cholesteryl groups as nanocarriers

Amphiphilic polyphosphate graft copolymers with varied densities of cholesteryl esters and hydrophilic graft chains were prepared, and the solution properties of the graft copolymers were evaluated. Polyphosphates were synthesized as backbones by ring-opening polymerization of 2-isopropyl-2-oxo-1,3,2-dioxaphospholane (IPP), 2-(2-oxo-1,3,2-dioxaphosphoroyloxyethyl-2-bromoisobutyrate) (OPBB), and 2-choresteryl-2-oxo-1,3,2-dioxaphospholane (ChOP) using triisobutylaluminum as an initiator. Three types of polyphosphates (PIBr(x)Ch(y), x = number of OPBB units in a polymer; y = number of ChOP units in a polymer) such as PIBr4, PIBr6Ch1, and PIBr3Ch2 were obtained. The molecular weights of these polymers were 2.4 x 10(4), 2.4 x 10(4), and 2.6 x 10(4) g/mol, respectively. 2-Methacryloyloxyethyl phosphorylcholine (MPC) was grafted from the OPBB sites in PIBr(x)Ch(y) via atom transfer radical polymerization (ATRP) in EtOH. In each polymer system, the molecular weight of the graft polymer was linear with conversion. Furthermore, the polymer radical concentration remained constant during polymerization; that is, the molecular weights of the graft chains were easily controllable with polymerization time. The solution properties of amphiphilic PIBr(x)Ch(y)-g-PMPCs were investigated by the methods of surface tension measurement, light scattering, and fluorescence probe. The transition point (cmc) of the surface tension of the PIBr(x)Ch(y)-g-PMPCs aqueous solution decreased with an increase in the number of ChOP units in a graft polymer. Particularly, PIBr3Ch2-g-PMPC14.9K formed nanosized associates (R(h) = 7.5 nm) with 2.2 molecules above 0.1 wt %. v79 cells were used to evaluate the cytotoxicity of the graft polymers, but no cytotoxicity was observed. The graft polymers containing cholesteryl groups effectively enhanced the solubility of paclitaxel in an aqueous solution.     

Surfactant bound polypeptides: 1. Conformation in solution and solid state of poly (γ-benzyl-l-glutamate) — Triton X-100

N-carboxyanhydride of γ-benzyl-l-glutamate was polymerized using the potassium salt of the non-ionic surfactant Triton X-100, octylphenoxypolyethoxyethanol, as the initiator. N.m.r. spectra revealed the presence of the initiator moiety in the polymer. The surfactant bound polypeptides with a degree of polymerization of 21 and 26 had excellent solubility in several non-aqueous solvents as compared to the homopolypeptide poly-γ-benzyl-l-glutamate (PBLG). The circular dichroic profiles of the polymers in the helicogenic solvents trifluoroethanol and trimethyl phosphate were helical. I.r. spectra of films of the polymers also indicated α-helical conformation for the peptide block. X-ray diffraction data, on the other hand, showed along with a spacing corresponding to the hexagonal packing of helices, a 22 Å spacing, indicative of a new kind of long range order not observed with the homopoly-γ-benzyl-l-glutamate. Again, the polymers formed with facility mesophases in various solvents at concentrations, unlike PBLG, as low as 5–8% (w/v).     

Synthesis, characterization and thermal sensitivity of chitosan-based graft copolymers

Novel chitosan-based graft copolymers (CECTS-g-PDMA) were synthesized through homogeneous graft copolymerization of (N,N-dimethylamino)ethyl methacrylate (DMA) onto N-carboxyethylchitosan (CECTS) in aqueous solution by using ammonium persulfate (APS) as the initiator. The effect of polymerization variables, including initiator concentration, monomer concentration, reaction time and temperature, on grafting percentage was studied. XRD, FTIR, DSC and TGA were used to characterize the graft copolymers. Surface-tension measurements, turbidity measurements and temperature-variable (1)H NMR analysis were combined to investigate the thermal sensitivity of CECTS-g-PDMAs in aqueous solution.     

High performance polymeric flocculants based on modified polysaccharides—Microwave assisted synthesis

New generation of polymeric flocculants has been developed by optimally grafting polyacrylamide branches on purified polysaccharide backbone in authors’ laboratory. These flocculants are synergistically efficient at low doses, controlled biodegradable, shear resistant, and ecofriendly. Recently it has been observed in the authors’ laboratory that graft copolymers synthesized by microwave initiated and microwave assisted methods provide a better quality of graft copolymer with higher percentage of grafting in comparison with conventional redox grafting method. The synthesized graft copolymers were characterized by variety of material characterization techniques. The microwave assisted synthesized graft copolymers show superior flocculation characteristics when compared with graft copolymers synthesized by conventional and microwave initiated method as well as with commercially available flocculant. The details of material synthesis, mechanism, characterization and applications of these novel materials in the field of flocculation have been reported.     

Microwave assisted synthesis of polyacrylamide grafted agar (Ag-g-PAM) and its application as flocculant for wastewater treatment

Grafting of polyacrylamide (PAM) chains was performed onto the backbone of Agar by microwave assisted method, using microwave radiation in synergism with ceric ammonium nitrate (CAN) as the chemical free radical initiator. The intended grafting of the PAM chains were confirmed through intrinsic viscosity study, FTIR spectroscopy and elemental analysis (C, H, N, O & S). Further characterization of the grafted product was done in form of SEM morphology and TGA study. Flocculation efficacy of the synthesized graft copolymers was studied in kaolin suspension, through ‘Jar test’ procedure. Further, flocculation efficacy of the ‘best grade’ (as determined by ‘jar test’ in kaolin suspension) in wastewater was studied for possible application in reduction of pollutant load of wastewater.     

Chemosynthesis of poly(ε-lysine)-analogous polymers by microwave-assisted click polymerization

Poly(ε-lysine) (ε-PL)-analogous click polypeptides with not only similar α-amino side groups but also similar main chain to ε-PL were chemically synthesized for the first time through click polymerization from aspartic (or glutamic)-acid-based dialkyne and diazide monomers. With microwave-assisting, the reaction time of click polymerization was compressed into 30 min. The polymers were fully characterized by NMR, ATR-FTIR, and SEC-MALLS analysis. The deprotected click polypeptides had similar pK(a) value (7.5) and relatively low cytotoxicity as ε-PL and could be used as substitutes of ε-PL in biomedical applications, especially in endotoxin selective removal. Poly(ethylene glycol) (PEG)-containing alternating copolymers with α-amino groups were also synthesized and characterized. After deprotection, the polymers could be used as functional gene vector with PEG shadowing system and NCA initiator to get amphiphilic graft polymers.     

Preparation of cellulose graft poly(methyl methacrylate) copolymers by atom transfer radical polymerization in an ionic liquid

Cellulose graft poly(methyl methacrylate) copolymers were prepared by atom transfer radical polymerization (ATRP) in an ionic liquid. Cellulose chloroacetate, as a macroinitiator, was first synthesized by direct acylation of cellulose with chloroacetyl chloride without any catalysts under mild conditions in an ionic liquid, 1-allyl-3-methylimidazolium chloride (BMIMCl). Then, the macroinitiator was used for the ATRP of MMA mediated by the CuBr and 2,2′-bipyridine (bpy) catalysis system. The copolymerization was carried out in BMIMCl without homopolymer byproduct. The polymers were easily separated from the catalyst when the ionic liquid was used as reaction medium. The grafting copolymers were characterized by means of ¹H NMR, AFM and GPC. The results showed that the obtained copolymers had grafted polymer chains with well-controlled molecular weight and polydispersity, and the polymerization was a “living/controlled” system. Further, through AFM observation, it was found that the cellulose graft copolymer in solution could aggregate and self-assembly into sphere-like polymeric structure.     

Creating a unique environment for selecting reactive enzymes with DNA: 'Sticky' binding of oligocation-grafted polymers to DNA

To provide colloidally stable polyplexes formed between pDNA and cationic polymers, cationic polymers have been modified with hydrophilic polymers to form a hydrophilic shell. Block copolymers of cationic and hydrophilic polymers and cationic polymers grafted with hydrophilic polymers are representative designs of such polymers. Here, we report a new design of cationic polymers and oligocationic peptide-grafted polymers. We synthesized 15 kinds of graft copolymers by varying the number of cationic charges of the peptides and their grafting density. We found that graft copolymers with less cationic peptides and less grafting density formed colloidally stable polyplexes. Interestingly, the less cationic graft copolymers bind to excess amounts of pDNA. We also found that the graft copolymers showed selectivity toward reactive enzymes affording the reaction of pDNA with nucleases, while suppressing both the replication of DNA by DNA polymerase and gene expression. The suppression of the replication and expression is considered to result from the high capacity of the graft copolymers for binding with pDNA. The polynucleotides produced by DNA polymerase or RNA polymerase would be captured by the graft copolymers to impede these enzymatic reactions.     

Comb polymers prepared by ATRP from hydroxypropyl cellulose

Hydroxypropyl cellulose (HPC) was used as a core molecule for controlled grafting of monomers by ATRP, the aim being to produce densely grafted comb polymers. HPC was either allowed to react with an ATRP initiator or the first generation initiator-functionalized 2,2-bis(methylol)propionic acid dendron to create macroinitiators having high degrees of functionality. The macroinitiators were then "grafted from" using ATRP of methyl methacrylate (MMA) or hexadecyl methacrylate. Block copolymers were obtained by chain extending PMMA-grafted HPCs via the ATRP of tert-butyl acrylate. Subsequent selective acidolysis of the tert-butyl ester moieties was performed to form a block of poly(acrylic acid) resulting in amphiphilic block copolymer grafts. The graft copolymers were characterized by 1H NMR and FT-IR spectroscopies, DSC, TGA, rheological measurements, DLS, and tapping mode AFM on samples spin coated upon mica. It was found that the comb (co)polymers were in the nanometer size range and that the dendronization had an interesting effect on the rheological properties.     

Prediction of lower critical solution temperature of N-isopropylacrylamide–acrylic acid copolymer by an artificial neural network model

In this paper, we have investigated the lower critical solution temperature (LCST) of N-isopropylacrylamide–acrylic acid (NIPAAm-AAc) copolymer as a function of chain-transfer agent/initiator mole ratio, acrylic acid content of copolymer, concentration, pH and ionic strength of aqueous copolymer solution. Aqueous solutions with the desired properties were prepared from previously purified polymers, synthesized at 65 °C by solution polymerization using ethanol. The effects of each parameter on the LCST were examined experimentally.In addition, an artificial neural network model that is able to predict the lower cretical solution temperature was develeped. The predictions from this model compare well against both training and test data sets with an average error less than 2.53%.Figure Cross plot of predicted and experimental LCST values for the testing data set.     

Sulphated exopolysaccharides produced by two unicellular strains of cyanobacteria,Synechocystis PCC 6803 and 6714

The exopolysaccharides (EPS) of two unicellular strains of cyanobacteria Synechocystis PCC 6803 and 6714, formed labile, radial structures, uniformly distributed on the cell surface, and stainable by specific dyes for acidic polysaccharides. The two strains produced EPS at similar rates, which depended, along with the duration of the producing phase, on the incubation conditions. The exopolysaccharides from both strains were constituted of at least 11–12 mono-oses, probably forming several types of polymers. They contained about 15–20% (w/w) uronic derivatives and 10–15% (w/w) osamines. Proteins represented 20–40% of total weight. A most interesting feature was the presence of 7–8% (molar ratio) sulphate residues, a characteristic that is otherwise limited to exopolysaccharides produced by eukaryotic algae.Abbreviations EPS exopolysaccharides - KDO 3-deoxy-d-mannooctulosonate - LPS lipopolysaccharides     

Biocontrol of the shore fly Scatella tenuicosta with Hypoaspis miles and H. aculeifer in peat pots

Hypoaspis miles Berlese and H. aculeiferCanestrini (Acari: Laelapidae) were usedagainst Scatella tenuicosta Collin(Diptera: Ephydridae) at the rates of 7, 14and 36 mites per 0.3-l peat pot (1000, 2000 and5000 per net-m² of peat) with mint (Mentha piperita L.) as the crop. The predatorswere applied either one day (preventivecontrol) or nine days after (curative control)exposing the pots to the flies in thegreenhouse. Based on the number of flies thatemerged from the pots, the control efficacy of preventive H. aculeifer treatments at therate of 36 mites per pot was 84–100% and 92–97% (range over four replicate blocks)after two and three weeks, respectively, fromthe application. The control efficacy ofcurative treatments was 93–100% and 83–94% after two and three weeks, respectively,from the application. Preventive treatmentswith H. miles applied at the rate of 36per pot controlled the flies by 92–100% and 68–97% two and three weeks, respectively, afterthe application. Curative treatments with 36H. miles per pot were less effective (–53–68% and –16–65%, respectively). All treatments with lower mite rates with eitherspecies were ineffective. Due to moreconsistent reduction of fly numbers by Hypoaspis aculeifer, the species was concluded to be a better biocontrol agent ofshore flies in short-term greenhouse cropsgrown in peat pots, probably due to its higherpredation capacity in comparison to H. miles.     

Surface eroding, liquid injectable polymers based on 5-ethylene ketal ε-caprolactone

Liquid, injectable hydrophobic polymers are potentially useful as depot systems for localized drug delivery. Low molecular weight polymers of 5-ethylene ketal ε-caprolactone and copolymers of this monomer with D,L-lactide were prepared and their properties assessed with respect to their suitability for this purpose. The polymers were amorphous and of low viscosity, and the viscosity was adjustable by choice of initiator and/or by copolymerizing with D,L-lactide. Lower viscosity polymers were attained by using 350 Da methoxy poly(ethylene glycol) as an initiator in comparison to octan-1-ol, while copolymerization with D,L-lactide increased viscosity. The initiator used had no significant effect on the rate of mass loss in vitro, and copolymers with D,L-lactide (DLLA) degraded faster than 5-ethylene ketal ε-caprolactone (EKC) homopolymers. For the EKC-based polymers, a nearly constant degradation rate was observed. This finding was attributed to the hydrolytic susceptibility of the EKC-EKC ester linkage, which was comparable to that of DLLA-DLLA, coupled with a higher molecular weight of the water-soluble degradation product and the low initial molecular weight of the EKC-based polymers. Cytotoxicity of the hydrolyzed EKC monomer to 3T3 fibroblast cells was comparable to that of ε-caprolactone, suggesting that polymers prepared from EKC may be well tolerated upon in vivo implantation.     

Biomass production by alders on four abandoned agricultural soils in Québec

The production of aboveground tissue of three alder species (Alnus crispa (Ait.) Pursh,A. rugosa (Du Roi) Spreng. andA. glutinosa (L) Gaertn.) on four sites ranged from 0.4 t ha^–1 yr^–1 to 4.0 t ha^–1 yr^–1 after four growing seasons. Large differences were observed among the four sites studied and among species. Soil nutrient levels affected the biomass production and foliar symptoms of P and Mg deficiency occurred withA. crispa andA. rugosa. Because of their poor aboveground biomass production (0.4–1.4 t ha^–1 yr^–1),A. crispa andA. rugosa should be used mainly as nurse trees. For its higher potential for biomass production (up to 4.0 t ha^–1 yr^–1), and its apparent higher ability to use P and Mg on deficient sites,A. glutinosa should be used preferably toA. crispa andA. rugosa for the production of biomass.     

The Israel National Skin Bank: Quality Assurance and Graft Performance of Stored Tissues

The Israel National Skin Bank (INSB) was founded jointly by the Israel Defense Forces (IDF) Medical Corps and the Ministry of Health in 1986. The prime purpose of the Skin Bank is to treat burn victims incurred at war or during mass casualty incidences. The INSB Protocol is comprised of international skin bank protocols and our previous and present research results. They provide the framework for selecting optimal guidelines for procurement, processing, preservation, storage and evaluation of transplantation performance of viable skin grafts. For evaluation and direct comparison of graft performance of glycerolized or cryopreserved skin stored for long periods, we have applied a mouse recipient model developed by us. This model assesses graft performance before the rejection process takes place. The in vivo design has inherent clinical relevance, which is especially appealing. Cryopreserved skin performed better than glycerolized skin (p > 0.027), but fresh skin performed significantly better than cryopreserved skin (p > 0.003), as analyzed by the Mann–Whitney non-parametric test. Then graft performance of skin specimens were cryopreserved by programmed or stepwise freezing and stored at -80°C or in liquid nitrogen for 1 and 6–10 months was evaluated. The average score of skin preserved by programmed freezing and stored in liquid nitrogen is the highest for both storage periods. This method has a highly significant advantage (p < 0.007) over the others for 6–10 months storage, evaluated by graft adherence. Several interaction factors determine the quality of cryopreserved skin. Highly significant is the interaction factor/'combined effect' of sample variability with the method of cryopreservation or with the storage period. Finally, the results of paired comparison of selected histology criteria of cryopreserved to fresh skin indicated that storage of skin for up to 5 years did not impair significantly its performance compared to fresh skin, whereas, after six years of storage, there was a highly significant (p < 0.001) impairment in skin quality. We offer a simplified in vivo model and analysis for cryopreserved skin graft performance, suggesting that the evaluation procedures, which are issues of great interest in skin banking, may help future skin banks to make informed choices and decisions regarding quality issues.     

Thermostable malate synthase of<Emphasis Type="Italic"> Streptomyces thermovulgaris</Emphasis>

The gene, encoding malate synthase (MS), aceB, was cloned from the thermophilic bacterium Streptomyces thermovulgaris by homology-based PCR. The 1,626-bp cloned fragment encodes a protein consisting of 541 amino acids. S. thermovulgaris malate synthase (stMS) gene was over-expressed in Escherichia coli using a glutathione-S transferase (GST) fusion vector (pGEX-6P-1), purified by affinity chromatography, and subsequently cleaved from its GST fusion partner. The purified stMS was characterized and compared to a mesophilic malate synthase (scMS) from Streptomyces coelicolor. stMS exhibited higher temperature optima (40–60 °C) than those of scMS (28–37 °C). It was more thermostable and very resistant to the chemical denaturant urea. Amino acid sequence comparison of stMS with four mesophilic streptomycete MSs indicated that they share 70.9–91.4% amino acid identities, with stMS possessing slightly more charged residues (~31%) than its mesophilic counterparts (~28–29%). Seven charged residues (E85, R187, R209, H239, H364, R382 and K520) that were unique to stMS may be selectively and strategically placed to support its peculiar characteristics.     

Effects of kinetin,paclobutrazol and their interactions on the microtuberization of potato stem segments cultured in vitro in the light

Single-nodal cuttings of Solanum tuberosum (four cultivars) and Solanum chacoense were induced to produce in vitro microtubers on Murashige & Skoog (MS) medium supplemented with 8 g l^–1 sucrose and various concentrations of kinetin and paclobutrazol. The cultures were kept 10 days in darkness and then transferred to a 14 h daylength with 100 µE m^–2 sec^–1 light intensity at 21 °C. Kinetin (2.5 mg l^–1) had no significant influence on tuber formation. However, its addition together with paclobutrazol (0.001 mg l^–1) significantly enhanced tuberization. Paclobutrazol alone stimulated early tuber initiation and inhibited stem growth. Despite some genotype × treatment interactions, all genotypes (from very early to late and wild type) formed the maximum proportion of explants bearing microtubers on the media containing both plant growth regulators.