title: Influence of the electric field on supramolecular structure and properties of amyloid-specific reagent Congo red.
abstract: Among specific amyloid ligands, Congo red and its analogues are often considered potential therapeutic compounds. However, the results of the studies so far have not been univocal because the properties of this dye, derived mostly from its supramolecular nature, are still poorly understood. The supramolecular structure of Congo red, formed by π-π stacking of dye molecules, is susceptible to the influence of the electric field, which may significantly facilitate electron delocalization. Consequently, the electric field may generate altered physico-chemical properties of the dye. Enhanced electron delocalization, induced by the electric field, alters the total charge of Congo red, making the dye more acidic (negatively charged). This is a consequence of withdrawing electrons from polar substituents of aromatic rings-sulfonic and amino groups-thus increasing their tendency to dissociate protons. The electric field-induced charge alteration observed in electrophoresis depends on dye concentration. This concentration-dependent charge alteration effect disappears when the supramolecular structure disintegrates in DMSO. Dipoles formed from supramolecular fibrillar species in the electric field become ordered in the solution, introducing the modified arrangement to liquid crystalline phase. Experimental results and theoretical studies provide evidence confirming predictions that the supramolecular character of Congo red is the main reason for its specific properties and reactivity.
authors.affiliation: Chair of Medical Biochemistry, Jagiellonian University Medical College, Kopernika, Kraków, Poland.
authors.forename: Paweł
authors.initials: P
authors.lastname: Spólnik
authors.forename: Marcin
authors.initials: M
authors.lastname: Król
authors.forename: Barbara
authors.initials: B
authors.lastname: Stopa
authors.forename: Leszek
authors.initials: L
authors.lastname: Konieczny
authors.forename: Barbara
authors.initials: B
authors.lastname: Piekarska
authors.forename: Janina
authors.initials: J
authors.lastname: Rybarska
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Zemanek
authors.forename: Anna
authors.initials: A
authors.lastname: Jagusiak
authors.forename: Piotr
authors.initials: P
authors.lastname: Piwowar
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Szoniec
authors.forename: Irena
authors.initials: I
authors.lastname: Roterman
mesh_terms: D000682:Amyloid / Q000378:metabolism*; D004396:Coloring Agents / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D003224:Congo Red / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D004560:Electricity; D004583:Electrons; D004586:Electrophoresis; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D008958:Models, Molecular; D008968:Molecular Conformation; D012235:Rhodamines / Q000737:chemistry; D013379:Substrate Specificity
chemical_list: D000682:Amyloid; D004396:Coloring Agents; D007202:Indicators and Reagents; D012235:Rhodamines; D003224:Congo Red; C029773:rhodamine B