U.S. Geological Survey standards—II. First compilation of data for the new U.S.G.S. rocks

Cation exchange properties of micas

Lower limits of molecular weights of compounds excluded from sephadex G-25 eluted with aqueous acetone mixtures : Application of the results to the separation of the components of tannic acid

Abstract Congo red (CR) and other self-assembling compounds creating supramolecular structures of rod- or ribbon-like architecture form specific complexes with cellulose and also with many proteins, including antibodies bound to the antigen and amyloids in particular. The mechanism of complexation and structure of these complexes are still poorly recognized despite the importance of the problem for medicine. This work proposes the progress in electron microscopy studies of amyloid-dye complexes by labeling supramolecular ligand CR with silver ions as a marker. Silver ions are introduced to CR carried by the strongly binding silver dye Titan yellow, which in addition form comicellar structures with CR. Silver carried by self-assembled dye molecules forms in the resulting metal nanoparticles, making the specific amyloid ligand CR perceptible in EM studies.

The use of Titan yellow dye as a metal ion binding marker for studies on the formation of specific complexes by supramolecular Congo red

Congo red (CR) which is known to act as selective amyloid ligand may when binds to these protein forms reflect their internal molecular structure. The disclosure by EM of sites binding the dye and their distribution in amyloids and amyloid-like aggregates formed in vitro is the focus of our work. In order to produce the required contrast, CR has been indirectly combined with metal via including by intercalation of Titan yellow (TY) which exhibits 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 less active in penetration to proteins. We have found however that in protein aggregates where unfolding is stabilized by aggregation and therefore irreversible, TY alone may serve as both ligand and metal carrier. The formation of ordered structures in amyloids were studied using IgG light chains with amyloidogenic properties, converted into amyloids through shaking. The resulting EM images were subjected to interpretation on the basis of the authors’ earlier research into the CR/light chain complexation process. 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 edge polypeptide loops belonging to unstable light chains form intermolecular bridges which promote creation of loose gel deposits, or are otherwise engaged in swapping processes leading to higher structural ordering.

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Silver ions as em marker of congo red ligation sites in amyloids and amyloid-like aggregates.

The component of Titan yellow most reactive towards magnesium has been isolated from the acetone-extracted dye by adsorption chromatography on Sephadex G–10. It is so reactive that it can be used at a concentration as small as 0·008 per cent., at which concentration the response is linear between 20 and 150 µg of magnesium.Values found for the magnesium content of silicate minerals agree with those obtained by spectrographic and gravimetric methods.

H. G. C. King

Papers

The component of commercial Titan yellow most reactive towards magnesium: its isolation and use in determining magnesium in silicate minerals