Large electrostatic differences in the binding thermodynamics of a cationic peptide to oligomeric and polymeric DNA.

Results presented here demonstrate that the thermodynamics of oligocation binding to polymeric and oligomeric DNA are not equivalent because of long-range electrostatic effects. At physiological cation concentrations (0.1-0.3 M) the binding of an oligolysine octacation KWK6-NH2 (+8 charge) to single-stranded poly(dT) is much stronger per site and significantly more salt concentration dependent than the binding of the same ligand to an oligonucleotide, dT(pdT)10 (-10 charge). These large differences are consistent with Poisson-Boltzmann calculations for a model that characterizes the charge distributions with key preaveraged structural parameters. Therefore, both the experimental and the theoretical results presented here show that the polyelectrolyte character of a polymeric nucleic acid makes a large contribution to both the magnitude and the salt concentration dependence of its binding interactions with simple oligocationic ligands.

Resistance to human immunodeficiency virus type 1 infection conferred by transduction of human peripheral blood lymphocytes with ribozyme, antisense, or polymeric trans-activation response element constructs.

Human peripheral blood lymphocytes (PBLs) were transduced with a number of recombinant retroviruses including RRz2, an LNL6-based virus with a ribozyme targeted to the human immunodeficiency virus (HIV) tat gene transcript inserted within the 3' region of the neomycin-resistance gene; RASH5, and LNHL-based virus containing an antisense sequence to the 5' leader region of HIV-1 downstream of the human cytomegalovirus promoter; and R20TAR, an LXSN-based virus with 20 tandem copies of the HIV-1 trans-activation response element sequence driven by the Moloney murine leukemia virus long terminal repeat. After G418 selection, transduced PBLs were challenged with the HIV-1 laboratory strain IIIB and a primary clinical isolate of HIV-1, 82H. Results showed that PBLs from different donors could be transduced and that this conferred resistance to HIV-1 infection. For each of the constructs, a reduction of approximately 70% in p24 antigen level relative to the corresponding control-vector-transduced PBLs was observed. Molecular analyses showed constitutive expression of all the transduced genes from the retroviral long terminal repeat, but no detectable transcript was seen from the internal human cytomegalovirus transcript was seen from the internal human cytomegalovirus promoter for the antisense construct. Transduction of, and consequent transgene expression in, PBLs did not impact on the surface expression of either CD4+/CD8+ (measured by flow cytometry) or on cell doubling time (examined by [3H]thymidine uptake). These results indicate the potential utility of these anti-HIV-1 gene therapeutic agents and show the preclinical value of this PBL assay system.

Asymmetric aldol reaction with BINAM-sulfonyl polymeric organocatalyst

The BINAM-sulfonyl polymeric organocatalysts was prepared by the AIBN-promoted copolymerization of BINAM-derived sulfonamide, styrene and divinylbenzebe. The polymer catalyzed the asymmetric aldol reaction of aliphatic ketones with aromatic aldehydes to give the aldol products in up to 83% yield and with up to 95% ee. The catalysts could be recovered upt to 6 times with only a slight decrease on its activity.

Evolution of extracellular polymeric substances produced in two submerged membrane bioreactors working at high sludge age

This research paper deals with the evolution of the extracellular polymeric substances (EPS) produced in the mixed liquor of two 25 L bench-scale membrane bioreactors (MBRs), with micro (MF-MBR) and ultrafiltration (UF-MBR) submerged membranes. The conclusion focuses on the relationship between the operation and how EPS respond, demonstrating that significant changes in EPS concentration were commonly observed when abrupt changes in the operational conditions took place. Bound EPS (EPSb) showed moderate positive statistical correlations with sludge age and MLSS for the two MBRs. Soluble EPS (EPSs), on the other hand, showed a moderate negative statistical correlation between EPSs with the two parameters analyzed for MF-MBR and no correlation with the UF-MBR was found. With respect to the composition of EPS, EPSb were mostly made up of proteins (44–46%) whereas in EPSs, the three components (proteins, carbohydrates, and humic substances) appeared in approximately the same proportion. The statistical analysis exhibited strong positive correlations between EPSb and their constituents, however for EPSs, the correlation was strong only with carbohydrates and moderate with humic substances.

High strength, high modulus fibers by pyrolysis of polymeric fibers

Mode of access: Internet.

Polymeric grafting of acrylic acid onto poly(3-hydroxybutyrate-co-3-hydroxyvalerate): Surface functionalization for tissue engineering applications

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) melt processed disks and solvent cast films were modified by graft co-polyinerization with acrylic acid (AAc) in methanol solution at ambient temperature using gamma irradiation (dose rate of 4.5 kGy/h). To assess the presence of carboxylic acid groups on the surface, reaction with pentafluorophenol was performed prior to X-ray photoelectron spectroscopy analysis. The grafting yield for all samples increased with monomer concentration (2-15%), and for the solvent cast films, it also increased with dose (2-9 kGy). However, the grafting yield of the melt processed disks was largely independent of the radiation dose (2-8 kGy). Toluidine blue was used to stain the modified materials facilitating, visual information about the extent of carboxylic acid functionalization and depth penetration of the grafted copolymer. Covalent linking of glucosamine to the functionalized surface was achieved using carbodimide chemistry verifying that the modified substrates are suitable for biomolecule attachment.

Systematic selection of solvents for the fabrication of 3D combined macro- and microporous polymeric scaffolds for soft tissue engineering

In this study, we investigate the fabrication of 3D porous poly(lactic-co-glycolic acid) (PLGA) scaffolds using the thermally-induced phase separation technique. The current study focuses on the selection of alternative solvents for this process using a number of criteria, including predicted solubility. toxicity, removability and processability. Solvents were removed via either vacuum freeze-drying or leaching, depending on their physical properties. The residual solvent was tested using gas chromatography-mass spectrometry. A large range of porous, highly interconnected scaffold architectures with tunable pore size and alignment was obtained, including combined macro- and microporous structures and an entirely novel 'porous-fibre' structure. The morphological features of the most promising poly(lactic-co-glycolic acid) scaffolds were analysed via scanning electron microscopy and X-ray micro-computed tomography in both two and three dimensions. The Young's moduli of the scaffolds under conditions of temperature, pH and ionic strength similar to those found in the body were tested and were found to be highly dependent on the architectures.

Towards a polymeric binding mimic for cytochrome CYP2D6

A series of fluorescent molecularly imprinted polymers has been prepared with a view to generating material capable of mimicking the binding characteristics of the metabolically important cytochrome isoform CYP2D6. Such polymers would have the possibility to form the sensing element in a high-throughput assay for the prediction of CYP2D6 affinity. The imprinted polymers possessed binding-dependent fluorescence. They re-bound their templates and various cross-reactivities were encountered for test compound/drug recognition. One polymer in particular exhibited a rational discrimination amongst the related synthetic templates and was reasonably successful in recognising CYP2D6 substrates from a drug panel. © 2005 Elsevier B.V. All rights reserved.

Characterization and cytotoxicity studies of thiol-modified polystyrene microbeads doped with [(Mo6X8)(NO3)6]2- (X=Cl, Br, I)

Halide octahedral molybdenum clusters [(Mo6X8)L6]n- possess luminescence properties that are highly promising for biological applications. These properties are rather dependent on the nature of both the inner ligands X (i.e. Cl, Br, or I) and the apical organic or inorganic ligands L. Herein, the luminescence properties and the toxicity of thiol-modified polystyrene microbeads (PS-SH) doped with [(Mo6X8)(NO3)6]2- (X=Cl, Br, I) were studied and evaluated using human epidermoid larynx carcinoma (Hep2) cell cultures. According to our data, the photoluminescence quantum yield of (Mo6I8)@PS-SH is significantly higher (0.04) than that of (Mo6Cl8)@PS-SH (6Br8)@PS-SH (6X8)@PS-SH showed that all three types of doped microbeads had no significant effect on the viability and proliferation of the cells.

Synthesis and characterisation of imprinted polymeric receptor mimics

Molecularly imprinted polymers (MIPs) are crosslinked polymers containing bespoke functionalised cavities arising from the inclusion of template molecules in the polymerisation mixture and their later extraction. When the polymers are prepared functional polymerisable monomers are included which become part of the polymer matrix and serve to decorate the cavities with functionality appropriate to the template molecules. Overall, binding sites are created which have a memory for the template both in terms of shape and matching functionality. Fluorescent molecularly imprinted polymers have the benefit of a fluorophore in their cavities that may respond to the presence of bound test compound by a change in their fluorescence output. The work presented falls into three main areas. A series of fluorescent MIPs was prepared with a view to generating material capable of mimicking the binding characteristics of the metabolically important cytochrome isoform CYP2D6. The MIPs re-bound their templates and various cross-reactivities were encountered for test compound/drug recognition. One MIP in particular exhibited a rational discrimination amongst the related synthetic templates and was reasonably successful in recognising CYP2D6 substrates from the drug set tested. In order to give some insights into binding modes in MIPs, attempts were made to produce functional monomers containing two or more fluorophores that could be interrogated independently. A model compound was prepared which fitted the dual-fluorophore criteria and which will be the basis for future incorporation into MIPs. A further strand to this thesis is the deliberate incorporation of hydrophobic moieties into fluorescent functional monomers so that the resulting imprinted cavities might be biomimetic in their impersonation of enzyme active sites. Thus the imprinted cavities had specific hydrophobic regions as well as the usual polar functionality with which to interact with binding test compounds.