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Pinacyanol as effective probe of fibrillar β‐amyloid peptide: Comparative study with Congo Red
Author(s) -
Sabaté Raimon,
Estelrich Joan
Publication year - 2003
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.10485
Subject(s) - congo red , chemistry , spectrophotometry , cyanine , centrifugation , amyloid (mycology) , ruthenium red , absorption (acoustics) , biophysics , cationic polymerization , peptide , titration curve , titration , crystallography , chromatography , biochemistry , polymer chemistry , fluorescence , organic chemistry , adsorption , inorganic chemistry , calcium , physics , acoustics , biology , quantum mechanics
The binding of pinacyanol (PIN), a cationic cyanine dye, to β‐amyloid fibrils (Aβ), which are associated with Alzheimer disease, was quantified by absorption spectrophotometry to measure the concentration of PIN bound to Aβ as a function of the Aβ concentration or by means of the separation of free PIN from bound PIN by centrifugation and subsequent analysis of the supernatant by visible‐absorption spectrophotometry. Both methods gave equivalent results. The stoichiometry of PIN binding to Aβ was 1, and the curve representing the concentration effect of Aβ on the concentration of a dye–Aβ complex showed a biphasic curve instead of the hyperbolic curve that is characteristic of weak ligand–macromolecule interactions [e.g., as shown by Congo Red (CR)]). This and the fact that a Scatchard plot could not be fitted to the experimental data suggested that PIN binds tightly to Aβ. A comparison to the interaction of CR with Aβ led us to conclude that PIN is more sensitive than CR. © 2003 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy), 2003