Modulation of Self-Assembly Process of Fibroin: An Insight for Regulating the Conformation of Silk Biomaterials

• Published in: Biomacromolecules 2015-12, Vol.16 (12), p.3936-3944
• Main Authors: Dubey, Priyanka, Murab, Sumit, Karmakar, Sandip, Chowdhury, Pramit K, Ghosh, Sourabh
• Format: Article
• Language: English
• Subjects: Animals; Aspartic Acid - chemistry; Bombyx - chemistry; Bombyx - physiology; Calcium - chemistry; Cations, Divalent; Circular Dichroism; Fibroins - chemistry; Fibroins - isolation & purification; Glutamic Acid - chemistry; Molecular Dynamics Simulation; Protein Structure, Secondary; Spectroscopy, Fourier Transform Infrared; Static Electricity
• ISSN: 1525-7797; 1526-4602
• DOI: 10.1021/acs.biomac.5b01258

Controlling the mechanism of self-assembly in proteins has emerged as a potent tool for various biomedical applications. Silk fibroin self-assembly consists of gradual conformational transition from random coil to β-sheet structure. In this work we elucidated the intermediate secondary conformation in the presence of Ca2+ ions during fibroin self-assembly. The interaction of fibroin and calcium ions resulted in a predominantly α-helical intermediate conformation, which was maintained to certain extent even in the final conformation as illustrated by circular dichroism and attenuated total reflectance-Fourier transform infrared spectroscopy. Further, to elucidate the mechanism behind this interaction molecular modeling of the N-terminal region of fibroin with Ca2+ ions was performed. Negatively charged glutamate and aspartate amino acids play a key role in the electrostatic interaction with positively charged calcium ions. Therefore, insights about modulation of self-assembly mechanism of fibroin could potentially be utilized to develop silk-based biomaterials consisting of the desired secondary conformation.