title: Temperature dependence of Congo red binding to amyloid β12-28.
abstract: Because Congo red (CR) can bind to critical intermediate structural forms of amyloid beta (Aβ), it has been suggested as a potential therapeutic agent against neurodegenerative disorders such as Alzheimer's disease. In this study, the interaction of CR with Aβ(12-28) was investigated by use of isothermal titration calorimetry (ITC). Studies conducted between 15 and 35 °C show that binding of CR to Aβ(12-28) was strongly dependent on temperature, with a decrease in CR-Aβ(12-28) complexation as temperature increases, presumably because of conformational changes within Aβ(12-28) at the highest temperatures, that conceal the CR binding sites. In fact, no CR binding was observed at 35 °C. The binding of CR to Aβ(12-28) was associated with favorable changes in both enthalpy and entropy that resulted in binding constants (K) of between 10(5) and 10(6) M (-1). An early (and more intense) entropy-driven CR disaggregation phase (K ~10(7)-10(8) M (-1)) was observed before the onset of CR-Aβ(12-28) complexation. Only CR disaggregation was observed at 35 °C. These results may provide further insights into the ability of CR to inhibit Aβ toxicity in neurodegenerative diseases.
authors: Department of Chemistry, State University of New York, College at Geneseo, Geneseo, NY, 14454, USA. mcknight@geneseo.edu
authors: Ruel E
authors: RE
authors: McKnight
authors: Douglas R
authors: DR
authors: Jackson
authors: Kazushige
authors: K
authors: Yokoyama
mesh_terms: D000544:Alzheimer Disease; D016229:Amyloid beta-Peptides / Q000737:chemistry*; D002021:Buffers; D002151:Calorimetry; D002942:Circular Dichroism; D003224:Congo Red / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D010446:Peptide Fragments / Q000737:chemistry*; D011485:Protein Binding; D011487:Protein Conformation; D013696:Temperature
chemical_list: D016229:Amyloid beta-Peptides; D002021:Buffers; D010446:Peptide Fragments; C092395:amyloid beta-protein (12-28); D003224:Congo Red
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