Changes in the polyelectrolyte-amphiphile interaction due to helix-coil transition induced by specific counterions or variations in temperature.
For the system kappa-carrageenan/amitriptyline it is shown that the degree of binding of amitriptyline is closely related to the carrageenan conformation as regulated by the counterions (Na+ or K+). The adsorption becomes much more pronounced when the carrageenan molecule is in the helix form (counterion K+) than when it has a coil conformation (counterion Na+). Furthermore, for the helical state the adsorption becomes strongly cooperative. It is also shown experimentally that the release from the adsorbed state has a conversion temperature at about 42 degrees C (helix-coil transition). The effect is also related to the linear charge density. For iota-carrageenan with a higher charge density the adsorption is strong and cooperative both in the presence of Na+ and K+ ions.
Caram-Lelham
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N
Uppsala University, Uppsala Biomedical Centre, Sweden.
Sundelöf
L O
LO
D000639:Amitriptyline / Q000737:chemistry; D000929:Antidepressive Agents, Tricyclic / Q000737:chemistry; D001704:Biopolymers / Q000737:chemistry*; D002240:Carbohydrate Sequence; D002351:Carrageenan / Q000737:chemistry; D004573:Electrolytes / Q000737:chemistry; D007477:Ions; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D013696:Temperature
D000929:Antidepressive Agents, Tricyclic; D001704:Biopolymers; D004573:Electrolytes; D007477:Ions; D000639:Amitriptyline; D002351:Carrageenan