L. E. St-Pierre

Adsorption of Bilirubin with Polypeptide-Coated Resins

Poly-L-lysine, poly-D-lysine and poly-L-ornithine have been coated covalently onto a water-swellable polyamide resin. These sorbents, especially the polylysine coated resins, exhibit high binding affinities for bilirubin in aqueous phosphate buffer solutions at 0 degrees C. The polylysine coated resins have an improved binding affinity for bilirubin over the sorbents with lysine containing oligopeptide pendants and much higher affinity than cholestyramine. The binding capacity is directly proportional to the number of lysine residues on the resin. Replacement of poly-L-lysine with poly-D-lysine does not affect the adsorption capacity.

Effect of silica nucleants on the rates of crystallization of poly(ethylene terephthalate)

Abstract Studies of the crystallization of poly(ethylene terephthalate) (PET) by d.s.c., both isothermally and non-isothermally, show that the addition of silica causes marked increases in rate at loadings

Polymer resins with amino acid containing pendants for sorption of bilirubin. II. Polyamide resins with various basic amino acids.

Short peptides, three to eight amino acids in length, containing various combinations of alanine, arginine, lysine, histidine and tyrosine have been synthesized onto water-swellable polyamide resin by the solid phase peptide synthesis method. The amount of bilirubin adsorbed from aqueous buffer solution (pH = 7.8) by the resins increases with increasing basicity of the amino acids in the pendant. As the number of basic amino acids on the pendant is increased fron one to five a 4.7 fold enhancement in the adsorption capacity is seen for arginine while a 9.3 fold enhancement is obtained for lysine. A corresponding increase in length for the non-basic histidine results in a 6 fold enhancement. With alanine the adsorption capacity is uneffected by an increase in pendant length.

Polymer resins with amino acid containing pendants for sorption of bilirubin. IV. Site binding constants.

Site binding constants, calculated for the adsorption of bilirubin onto various lysine, arginine, or histidine containing oligopeptide-resins assuming either a one or two site binding model, are of the order of 10(4) M-1. Using these data it can be shown that there are positive cooperative effects for lysine-containing pendants, while arginine-containing pendants eventually result in negative cooperative behaviour. This difference in behaviour has been attributed to the difference in the side groups in the arginine and lysine pendants and is discussed in terms of the basicity of the amino acids, accessibility to the sites as a consequence of the flexibility or rigidity of the side group, and in terms of pi-pi electron interactions, where applicable.

Water structure: Anomalies in interfacial tension with temperature for bovine serum albumin

Abstract It is current belief that the structure of water at bio-surfaces is significantly influenced and ordered by the constituent macromolecules. The water, in turn, reciprocates, imposing restrictions on the properties and structure of these surface biopolymers. Recent evidence suggests that water adjacent to interfaces-“vicinal water”-significantly differs from bulk water in undergoing cooperative changes in properties and structure at a number of discrete temperature ranges. It is the purpose of this note to report on studies undertaken to determine the influence of these changes on macromolecules present at interfaces especially the liquid-liquid interface.

Polymeric Sorbents for Bile Acids: II. Oligopeptide-Containing Resins with Quaternary Amine Groups

Abstract Polymeric sorbents for bile acids have been prepared by attaching lysine-containing peptide sequences onto a water-swellable polyamide resin, by solid phase peptide synthesis, and then attaching a terminal N,N-dimethyl glycine residue that was subsequently quaternized. The resins with relatively longer peptide sequences demonstrated a higher binding capacity, on a per active site basis, for bile acids in pH 7.4 aqueous buffer solutions at 20°C than cholestyramine and colestipol when tested under the same in vitro conditions. In solutions of low ionic strength, they also have a degree of specificity for bile acid anions. The resins have a higher binding affinity for cholic acid than for glycocholic acid, which indicates the importance of the hydrophobic interactions in the binding.

Polymer resins with amino acid containing pendants for sorption of bilirubin. I. Comparison of Merrifield and polyamide resins.

Merrifield resins with various amino acid containing pendants and a water swellable polyamide resin with the peptide alanine-alanine-alanine-arginine as the pendant group have been prepared by solid phase peptide synthesis. Merrifield resins with either arginine or lysine pendants are capable of sorbing bilirubin from aqueous solution (pH = 7.8) but those with other amino acid pendants gave no indication of sorption. The polyamide-arginine resin showed, on a functional group basis, a higher capacity for bilirubin than does cholestyramine. It is proposed that the formation of salt linkages causes a strong interaction of bilirubin with arginine and lysine.

The heterogeneous nucleation of crystallization in isotactic polystyrene

Abstract Isothermal crystallization of isotactic polystyrene was studied by differential scanning calorimetry. From the bell-shaped rate versus temperature diagram, a crystallization maximum is observed in the region of 175°C and the results are interpreted in terms of the Turnbull-Fisher equation for nucleation. The effectiveness of virgin silica and chemically treated silica filler, both having similar physical characteristics, as nucleating agents for isotactic polystyrene (i-PS), was examined. Incorporation of silica powder into i-PS increased the rate of crystallization of the polymer. It was also found that varying the polymer-silica interfacial energy by treating a silica surface with trimethylchlorosilane caused a change in its nucleating ability; the greater the interfacial energy the more efficiently the silica nucleates. The treated silica, which has no net interfacial energy with the polymer, appears to act as an inhibitor to the crystallization of isotactic polystyrene.

Phosphonium-Containing Resins as Bile Acid Sorbents: In-Vitro Binding Studies

Abstract Three new phosphonium-containing analogs of cholestyramine (Questran) resins have been synthesized: two styrene-divinylbenzene-vinyl benzyltrimethylphosphonium chloride resins, one (Resin I) of low and one (Resin II) of high ionic content, and a diphosphonium resin (Resin III) prepared by reacting 1,2-bis(dimethylphosphino)ethane with chloromethylated styrene-divinylbenzene. The effects of variation of ionic content of the resin, hence of swellability of the backbone, of added salt in the sorbate, i.e., of increased ionic strength of the buffer on the in-vitro binding of glycocholate (GC−), were determined. Resin I, with low ionic content (<1 mmol Cl−/g resin), was ineffective in binding GC− from Tris-HCl buffer (2.5 mM, pH 7.0), but the extent of binding was markedly increased when the resin was pretreated with an organic solvent (e.g., DMF), thereby causing it to swell and facilitating the diffusion of GC− into the resin. When expressed as moles of GC−/ pendant, the isotherms for the in-vitro b...

Interfacial free energies of binary mixtures of homopolymers on polytetrafluoroethylene and on silanized glass

The adhesion tensions, τ, on polytetrafluoroethylene and on dichlorodimethylsilane-treated glass, were obtained as a function of composition for three binary mixtures of polyethers, a polyether + water solution, and a polydimethylsiloxane + tetralin solution. From these, the solid/liquid interfacial tensions γ SL were deduced and found to be in good agreement with those calculated using the Prigogine theory. It was also concluded that the replacement of the gas phase by a low-energy solid did not result in any substantial reorganization of the polar mixtures at the interface.