  We have carried out a comparative study of the microrheological properties of
silk fibroin solutions formed from a variety of silks indigenous to the Indian
subcontinent. We present the measured viscoelastic moduli of Tasar silk fibroin
solution using both a single and dual optical tweezer at 0.16% and 0.25% (w/v).
The bandwidth of the measurements carried out using optical tweezers is
extended down to the lower frequency regime by a video microscopy measurement.
Further, we have measured the viscoelastic moduli of Eri and Muga varieties of
silk fibroin solutions at a higher concentration (1.00% w/v) limiting the tool
of measurement to video microscopy, as the reduced optical transparencies of
these solutions at higher concentration preclude an optical tweezer based
investigation. The choice of a higher concentration of fibroin solution of the
latter silk varieties is so as to enable a comparison of the shear moduli
obtained from optical methods with their corresponding fibre stiffness obtained
from wide angle X-ray scattering data. We report a correlation between the
microstructure and microrheological parameters of these silk varieties for the
concentration of fibroin solutions studied.
