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Thermodynamics of mucopolysaccharide–dye binding. II. Binding constant and cooperativity parameters of acridine orange–dermatan sulfate system
Author(s) -
Menter Julian M.,
Hurst Robert E.,
West Seymour S.
Publication year - 1977
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/bip.1977.360160317
Subject(s) - chemistry , dermatan sulfate , acridine orange , cooperativity , binding constant , sulfate , binding site , stereochemistry , glycosaminoglycan , organic chemistry , chondroitin sulfate , biochemistry , apoptosis
In the acridine orange–dermatan sulfate system, free and bound dye can be distinguished from each other spectroscopically. This permits the use of fluorometric methods to study the binding of acridine orange to the acid mucopolysaccharide dermatan sulfate. Experiments were conducted at 24°C in 10 −3 M citrate/phosphate buffer at pH = 7.0. The binding of the dye is highly cooperative, as evidenced by considerable interaction between adjacent bound dye molecules. Analysis of the data indicates that dermatan sulfate binds 2.3 ± 0.3 mol of acridine orange per dermatan sulfate uronic acid residue with a cooperative binding constant, K q ranging from 4.9 to 6.0 × 10 5 M −1 which corresponds to a free energy of 7.74 ⩽ Δ G ° ⩽ 7.86. The cooperativity parameter q apparently increases with increasing polymer‐to‐dye ratio.