title: Silver ions as em marker of congo red ligation sites in amyloids and amyloid-like aggregates.
abstract: Congo red (CR) is a known selective amyloid ligand. The focus of our work is identification (by EM imaging) of dye binding sites and their distribution in amyloids and amyloid-like aggregates formed in vitro. In order to produce the required contrast, CR has been indirectly combined with metal via including Titan yellow (TY) by intercalation which exhibits a relatively strong affinity for silver ions. The resulting combined ligand retains its ability to bind to proteins (which it owes to CR) and can easily be detected in EM studies thanks to TY. We have found, however, that in protein aggregates where unfolding is stabilized by aggregation and therefore is irreversible, TY alone may serve as both, the ligand and the metal carrier. The formation of ordered structures in amyloids was studied using IgG light chains with amyloidogenic properties, converted into amyloids by shaking. The resulting EM images were subjected to interpretation on the basis of the authors' earlier research on the CR/light chain complexation process. Our results indicate that dimeric light chains, which are the subject of our study, produce amyloids or amyloid-like complexes with chain-like properties and strong helicalization tendencies. Cursory analysis suggests that the edge polypeptide loops belonging to unstable light chains form intermolecular bridges which promote creation of loose gel deposits, or are otherwise engaged in the swapping processes leading to higher structural ordering.
authors.affiliation: Chair of Medical Biochemistry, Medical College - Jagiellonian University, Kraków, Poland.
authors.forename: Janina
authors.initials: J
authors.lastname: Rybarska
authors.affiliation: Chair of Medical Biochemistry, Medical College - Jagiellonian University, Kraków, Poland.
authors.forename: Leszek
authors.initials: L
authors.lastname: Konieczny
authors.affiliation: Chair of Medical Biochemistry, Medical College - Jagiellonian University, Kraków, Poland.
authors.forename: Anna
authors.initials: A
authors.lastname: Jagusiak
authors.affiliation: Chair of Medical Biochemistry, Medical College - Jagiellonian University, Kraków, Poland.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Chłopaś
authors.affiliation: Chair of Medical Biochemistry, Medical College - Jagiellonian University, Kraków, Poland.
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Zemanek
authors.affiliation: Chair of Medical Biochemistry, Medical College - Jagiellonian University, Kraków, Poland.
authors.forename: Barbara
authors.initials: B
authors.lastname: Piekarska
authors.affiliation: Chair of Medical Biochemistry, Medical College - Jagiellonian University, Kraków, Poland.
authors.forename: Barbara
authors.initials: B
authors.lastname: Stopa
authors.affiliation: Department of Measurements and Electronics, AGH University of Science and Technology, Kraków, Poland.
authors.forename: Piotr
authors.initials: P
authors.lastname: Piwowar
authors.affiliation: Department of Cell Biology Imaging, Faculty of Biology, Earth Sciences, Jagiellonian University, Kraków, Poland.
authors.forename: Olga
authors.initials: O
authors.lastname: Woźnicka
authors.affiliation: Department of Bioinformatics and Telemedicine, Medical College - Jagiellonian University, Kraków, Poland.
authors.forename: Irena
authors.initials: I
authors.lastname: Roterman
mesh_terms: D000682:Amyloid / Q000032:analysis* / Q000737:chemistry* / Q000378:metabolism; D058227:Amyloidogenic Proteins / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D003224:Congo Red / Q000378:metabolism; D006801:Humans; D007147:Immunoglobulin Light Chains / Q000378:metabolism; D008854:Microscopy, Electron / Q000379:methods*; D011487:Protein Conformation; D012834:Silver; D014226:Triazenes / Q000737:chemistry
chemical_list: D000682:Amyloid; D058227:Amyloidogenic Proteins; D007147:Immunoglobulin Light Chains; D014226:Triazenes; C044584:titan yellow; D012834:Silver; D003224:Congo Red
keywords: Congo red; Titan yellow; amyloid-like aggregates; amyloids; edge loop; light chain; metal markers; supramolecular dyes