The ethanol-induced conformation transition of regenerated Bombyx mori silk fibroin membrane from a poorly
defined to the well ordered state was monitored by time-resolved Fourier transform infrared spectroscopy FTIR. for
the first time. From the analysis of FTIR difference spectra, taken on time scales as short as 6 s and up to 1 h after
addition of ethanol, intensity vs. time plots of an increasing band at 1618 cmy1 were observed indicating formation of
a b-sheet coincident with the loss of intensity of a band at 1668 cmy1 indicating decreases of random coil andror silk
I structure. Both infrared markers were fitted with identical biphasic exponential decay functions, however, there was
a clear burst phase occurring prior to the onset of the observed transitions. The conformation transition process is
indicated to either proceed sequentially through at least. two intermediate states that contain different levels of
b-sheet structure or to have parallel pathways of initial b-sheet formation followed by a slower ‘perfection’ phase.
The first observed process forms in a burst phase a few seconds after mixing or even faster., prior to the collection
of the first spectrum at 6 s. The second observed process occurs with a time constant of ;0.5 min, the intermediate
present at this stage then continues with a time constant of 5.5 min completing the observed formation of the
b-sheet. The conformation transition of this slower intermediate is not only indicated by an analysis of the kinetics of