Rhodamine binds to silk fibroin and inhibits its self-aggregation

• Published in: Biochimica et biophysica acta. Proteins and proteomics 2018-05, Vol.1866 (5-6), p.661-667
• Main Authors: Ragona, Laura, Gasymov, Oktay, Guliyeva, Aytaj J., Aslanov, Rasim B., Zanzoni, Serena, Botta, Chiara, Molinari, Henriette
• Format: Article
• Language: English
• Subjects: Aggregation inhibition; Binding Sites; Fibroins - metabolism; Gelation/fibril formation; Hydrogen-Ion Concentration; Ligand binding; NMR spectroscopy; Nuclear Magnetic Resonance, Biomolecular; Protein Aggregates; Protein Binding; Protein Conformation, alpha-Helical; Protein Conformation, beta-Strand; Protein Multimerization; Protein Stability; Proton Magnetic Resonance Spectroscopy; Rhodamines - metabolism; Self-aggregation; Silk fibroin; Spectrophotometry, Ultraviolet; Structure-Activity Relationship
• ISSN: 1570-9639; 1878-1454
• DOI: 10.1016/j.bbapap.2018.03.009

Amyloid structures are universal structures, widely diffuse in nature. Silk, capable of forming some of the strongest tensile materials on earth represents an important example of formation of functional amyloid fibrils, a process reminiscent of the oligomerization of peptides involved in neurodegenerative diseases. The stability of silk fibroin solutions in different conditions and its transition from α-helix/random coil to β-sheet structures, at the basis of gelation processes and fibril formation, have been here investigated and monitored employing different biophysical approaches. Silk fibroin aggregation state as a function of concentration, pH and aging has been characterized employing NMR ordered diffusion spectroscopy. The change of silk fibroin diffusion coefficient over time, which reflects the progress of oligomerization, has been monitored for silk fibroin alone and in the presence of a polycondensed aromatic dye, namely rhodamine 6G. NMR, UV and DLS measurements indicated that rhodamine specifically binds to silk fibroin with a micromolar KD. The reported data reveal, for the first time, that RHD is capable of inhibiting fibroin self-association, thus controlling β-conformational transition at the basis of fibril formation. The described approach could be extended to further protein systems, allowing better control of the oligomerisation process. [Display omitted] •Oligomerisation state of silk fibroin is successfully monitored by NMR diffusion.•Rhodamine 6G specifically binds silk fibroin with micromolar KD.•Rhodamine is capable of inhibiting silk fibroin self-aggregation.