Anticoagulant activity of a synthetic heparinoid in relation to molecular weight and N-sulfate content

Addition of chlorosulfonyl isocyanate to C=C bonds in cis-1,4-polyisoprene and reaction of the adduct with NaOH resulted in the formation of a water-soluble polyelectrolyte with N-sulfate and carboxylate groups. The polyelectrolyte showed anticoagulant activity and it was found, just as with heparin, that the activity was related to molecular weight and N-sulfate content

Investigations on vinylene carbonate. IV. Radiation induced graft copolymerization of vinylene carbonate and N-vinyl-N-methylacetamide onto polyethylene films

Graft copolymerization of binary mixtures of vinylene carbonate (VCA) and N-vinyl-N-methylacetamide (VIMA) onto low density polyethylene (LDPE) films was studied by the mutual γ-irradiation technique. Sufficient amounts of functionally active VCA groups could be grafted onto the surface and the hydrophilicity of the surface was also improved. The grafting of VCA onto polyethylene films in the binary solutions was found to be promoted by the presence of VIMA, thus showing a positive synergism. The VCA content in the graft copolymers was always higher than in the copolymers obtained by homogeneous copolymerization using the same monomer feed composition. The monomer reactivity ratios, as well as a preferential partitioning of the monomers surrounding the polymeric substrate, were considered to explain the grafting reactions in the binary systems

Tetrahydrofuran (co)polymers as potential materials for vascular prostheses

Polyethers were studied as potential materials for vascular prostheses. By crosslinking poly(tetramethylene oxide) (PTMO) with poly(ethylene oxide) (PEO), hydrophilic networks were obtained containing PTMO as well as PEO. Attempts were made to reduce the crystallinity and melting point of PTMO because of the required elastomeric behaviour at body temperature. Compared to non-crosslinked PTMO, crosslinking in the melt resulted in a decrease in the melting point from 43·7 to 38·7°C and a decrease of the crystallinity from 46 to 28%. By copolymerizing tetrahydrofuran with oxetane or dimethyloxetane, melting points below 38°C were obtained, together with crystallinities lower than 20%

Investigations on vinylene carbonate. V. Immobilization of alkaline phosphatase onto LDPE films cografted with vinylene carbonate and N-vinyl-N-methylacetamide

Low-density polyethylene (LDPE) films cografted with vinylene carbonate (VCA) and N-vinyl-N-methylacetamide (VIMA) were studied as a matrix for the immobilization of the enzyme alkaline phosphatase (ALP) either by direct fixation or by inserting spacers. When water-soluble alkyldiamines such as diaminoethylene, diaminobutane, diethylenetriamine, and diaminohexane were used as spacers between the matrix and the enzyme, the surface concentration (SC) of the active ALP coupled on the matrix was increased, whereas the effect of the spacer on the SC was dependent on the length of the spacer. Bovine serum albumin (BSA) was preimmobilized onto the LDPE films to provide a better simulation of the biological environment for the enzyme, and the SC of ALP on the matrix was significantly increased by coupling ALP onto the BSA preimmobilized surfaces. Compared to native ALP, some physicochemical properties of ALP could be improved by the covalent immobilization

Iron(III)-chelating resins X. Iron detoxification of human plasma with iron(III)-chelating resins

Iron detoxification of human blood plasma was studied with resins containing desferrioxamine B (DFO) or 3-hydroxy-2-methyl-4(1H)-pyridinone (HMP) as iron(III)-chelating groups. The behaviour of four resins was investigated: DFO-Sepharose, HMP-Sepharose and crosslinked copolymers of 1-(ß-acrylamidoethyl)-3-hydroxy-2-methyl-4(1H)-pyridinone (AHMP) with 2-hydroxyethyl methacrylate (HEMA) and of AHMP with N,N-dimethylacrylamide (DMAA). The efficiency of iron detoxification of plasma of the resins was mainly dependent on the affinity of the ligands and the hydrophilicity of the resins. The results of a stability study in phosphate-buffered saline at a physiological pH indicated that AHMP-DMAA was the most stable resin, whereas the Sepharose gels had a relatively lower stability. Experiments with the AHMP-DMAA resin showed that the resin was able to remove iron from plasma with different iron contents, and from plasma poisoned with FeCl3, iron(III) citrate or transferrin. A rapid removal from free serum iron was observed, whereas iron from transferrin was removed slowly afterwards. Only the overload iron was removed since in all cases the normal serum iron level of ca. 1 ppm was obtained

Saharan Dust from a Marine Perspective:Transport and Deposition along a Transect in the Atlantic Ocean

Saharan dust is transported in great quantities across the Atlantic Ocean, and a large part is deposited before it reaches the Caribbean. However, little is known about this dust deposition across the entire Atlantic, and the physical characteristics of the particles involved. Therefore, a transect of subsurface sediment traps and dust-collecting buoys was deployed, which provides a unique opportunity to study dust deposition in a spatial and temporal high resolution over multiple years. In this thesis dust deposition fluxes and atmospheric dust concentrations along the transect, particle size of the dust and their downwind trends are described. In addition, evidence that giant mineral dust particles (>75 μm) are blown all the way across the ocean is given, transported over thousands of kilometres, which is explained with a range of possible mechanisms. Also, a possible influence of Amazon River sediments to the western sediment traps by means of geochemical analysis is investigated