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The effect of polyelectrolyte counterion specificity, charge density, and conformation on polyelectrolyte–amphiphile interaction: The carrageenan/furcellaran–amitriptyline system
Author(s) -
Hugerth Andreas,
Sundelöf LarsOlof
Publication year - 2001
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/1097-0282(200102)58:2<186::aid-bip70>3.0.co;2-f
Subject(s) - chemistry , polyelectrolyte , counterion , carrageenan , amphiphile , aqueous solution , charge density , cationic polymerization , crystallography , stereochemistry , ion , organic chemistry , copolymer , polymer , physics , quantum mechanics , biochemistry
The effect of polyelectrolyte cation specificity, charge density, and conformation on the interaction between furcelleran, κ, ι, and λ‐carrageenan, respectively, and amitriptyline, an amphiphilic cationic drug molecule, was studied by means of a dialysis equilibrium technique. The carrageenans used in this study—furcelleran, κ, ι, and λ‐carrageenan—had a charge density corresponding to 0.69, 0.92, 1.53, and 2.07 sulfate groups per disaccharide. In general, the binding isotherms followed the order Li + < Na + < N(CH3) + 4< K + ≤ Cs + ≈ Rb + , i.e., the binding isotherms were shifted to higher concentrations of free amphiphile according to the sequence indicated. This affinity sequence correlates well with that found for the dextran sulfate–amitriptyline system (A. Hugerth and L.‐O. Sundelöf, Langmuir 2000, 16, 313–317). The factor determining the critical aggregation concentration in the presence of Na + compared to K + was found to be as follows: the flexibility (conformation) in the case of the lower charged carrageenans, i.e., furcelleran and κ‐carrageenan, charge density for ι‐carrageenan, and in the λ‐carrageenan case the difference in the ROSO − 3 –alkali ion specificity. © 2001 John Wiley & Sons, Inc. Biopolymers 58: 186–194, 2001