| 1. |
- Adal, M, et al.
(författare)
-
Determination of monomer reactivity ratios in the copolymerization of ethylene oxide and propylene oxide
- 1994
-
Ingår i: Tenside Surfactants Detergents. - 0932-3414 .- 2195-8564. ; 31, s. 9-11
-
Tidskriftsartikel (refereegranskat)abstract
- The reactivity ratios r1 (EO) and r2 (PO) for the copolymerization of ethylene oxide (EO) and propylene oxide (PO) have been determined. The reactions were carried out in dry dimethyl formamide at 90°C using the potassium salt of ethylene glycol as initiator. The polymer composition at different EO/PO ratios in the feed was determined by 1H-NMR. Using the Fineman-Ross method to calculate reactivity ratios from the values of polymer composition, rl- and r2-values of 1.8 and 0.3, respectively, were obtained.
|
|
| 2. |
- Brink, C, et al.
(författare)
-
Using poly(ethylene imine) to graft poly(ethylene glycol) or polysaccharide to polystyrene
- 1992
-
Ingår i: Colloids and Surfaces. - 0166-6622 .- 1873-4340. ; 66, s. 149-156
-
Tidskriftsartikel (refereegranskat)abstract
- A novel method of grafting poly(ethylene glycol) (PEG) or polysaccharide to polystyrene has been developed. The non-charged hydrophilic polymer is firstly grafted to poly(ethylene imine). After prior oxidation of the solid surface, the graft copolymer is subsequently adsorbed. Analysis by electron spectroscopy for chemical analysis and ellipsometry indicates a trains-and-loops arrangement of the copolymer on the surface with densely packed PEG or polysaccharide chains oriented towards the bulk water phase. Ellipsometry also shows that whereas the PEG grafting is fast, the polysaccharide grafting is more sluggish. Attachment of both graft copolymers is completely irreversible, as seen also by ellipsometry. The surfaces obtained are highly protein repellent, as shown by enzyme-linked immunosorbent assay using fibrinogen and immunoglobulin G as model proteins.
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
- Holmberg, K, et al.
(författare)
-
Effects on protein adsorption, bacterial adhesion and contact angle of grafting PEG chains to polystyrene
- 1993
-
Ingår i: Journal of Adhesion Science and Technology. - 0169-4243 .- 1568-5616. ; 7, s. 503-517
-
Tidskriftsartikel (refereegranskat)abstract
- Poly(ethylene glycol) (PEG) has been grafted to polystyrene using branched poly(ethylene imine) (PEI) as an anchoring polymer. A dense grafting of PEG chains is obtained if a PEG-PEI adduct is first prepared by treatment of PEI with PEG epoxide and the adduct subsequently adsorbed on an oxidized polystyrene surface. Prepared in this way the PEG-PEI adduct is irreversibly attached to the surface with the PEG chains oriented towards the aqueous phase, as shown by ESCA and ellipsometry. This dense PEG coating is highly effective in preventing adsorption of fibrinogen and IgG, as well as adhesion of the oral bacterium Streptococcus mutans. Somewhat surprisingly, the degree of PEG branching, as well as the PEG molecular weight, did not markedly influence protein rejecting properties. The water contact angle on polystyrene decreased in the order: untreated polystyrene > oxidized > PEI treated > PEG-PEI treated. Block copolymers of poly(ethylene glycol)/poly(propylene glycol) type attached to polystyrene showed temperature dependent protein rejecting properties. At temperatures well below the cloud point of the polymer in water the surface is protein repellant whereas around and above the cloud point protein adsorption occurs to a considerable extent. The block copolymer layer expands and contracts with temperature variations, as can be monitored by ellipsometry.
|
|
| 6. |
- Holmberg, Martin, et al.
(författare)
-
Bacteria classification based on feature extraction from sensor data
- 1998
-
Ingår i: Biotechnology Techniques. - : Kluwer Academic Publishers. - 0951-208X .- 1573-6784. ; 12:4, s. 319-324
-
Tidskriftsartikel (refereegranskat)abstract
- Data evaluation and classification have been made on measurements by an electronic nose on the headspace of samples of different types of bacteria growing on petri dishes. The chosen groups were: Escherichia coli, Enterococcus sp., Proteus mirabilis, Pseudomonas aeruginosa, and Staphylococcus saprophytica. An approximation of the response curve by time was made and the parameters in the curve fit were taken as important features of the data set. A classification tree was used to extract the most important features. These features were then used in an artificial neural network for classification. Using the ‘leave-one-out’ method for validating the model, a classification rate of 76% was obtained
|
|
| 7. |
|
|
| 8. |
- Na, A., et al.
(författare)
-
Synthesis of phosphatidylcholine with (n-3) fatty acids by phospholipase A 2 in microemulsion
- 1990
-
Ingår i: Journal of the American Oil Chemists Society. - 0003-021X .- 1558-9331. ; 67:11, s. 766-770
-
Tidskriftsartikel (refereegranskat)abstract
- Phosphatidylcholine containing a long chain polyunsaturated acyl group at the 2-position has been prepared by phospholipase A 2 catalyzed esterification of lysophosphatidylcholine with polyunsaturated fatty acids EPA (C20:5) or DHA (C22:6). Preliminary studies showed that the other fatty acids, such as lauric acid (C12), palmitic acid (C16), stearic acid (C18) and linoleic acid (C18:2), were also incorporated. To our knowledge, phospholipase A 2 catalyzed condensation reactions have not been reported in the literature before. The reactions were performed in sodium bis(2-ethylhexyl)-sulfosuccinate-based microemulsions containing small amounts of water. Synthesis of the same phospholipid by transesterification of phosphatidylcholine with the polyunsaturated acids in microemulsion failed; however, enzymatic hydrolysis to lysophosphatidylcholine was facile, quantitative conversion from phosphatidylcholine being attained after 16 hr reaction time. An additional observation was that, unlike enzymatic hydrolysis of phospholipids, the condensation reaction catalyzed by phospholipase A 2 was totally independent of the presence of calcium. © 1990 AOCS Press.
|
|
| 9. |
- Österberg, E, et al.
(författare)
-
Comparison of polysaccharide and poly(ethylene glycol) coatings for reduction of protein adsorption on polystyrene surfaces
- 1993
-
Ingår i: Colloids and Surfaces A. - 0927-7757 .- 1873-4359. ; 77, s. 159-169
-
Tidskriftsartikel (refereegranskat)abstract
- There has been much recent interest in the use of poly(ethylene glycol)s (PEGs) for a variety of biotechnical applications. In the present work we have immobilized several cellulose derivatives and dextran on polystyrene surfaces and have measured the extent of fibrinogen adsorption onto the coated surfaces. Immobilization was achieved by adsorption onto clean polystyrene and by covalent linkage of oxidized polysaccharides to polyethylenimine which was ionically bound to polystyrene. Covalently bound polysaccharides. and adsorbed polysaccharides that are strongly held, compare well with poly(ethylene glycol) in preventing fibrinogen adsorption. The same polymers were coupled to polystyrene latex particles to permit examination by analytical microparticle electrophoresis. This investigation suggests that adsorbed polysaccharides form thicker layers than do covalently bound polysaccharides. Despite the polysaccharides being bound at many points along the polymer chain while PEG is bound only at the polymer terminus, the functional equivalence of polysaccharide and PEG coatings is of significance in interpreting the protein-rejecting ability of polymer-modified surfaces.
|
|
