Conformational transition and liquid crystalline state of regenerated silk fibroin in water

Abstract

The conformational transition of molecular chains of regenerated silk fibroin (SF) aqueous solution is systematically investigated by circular dichroism, Raman, IR, and UV-vis spectroscopies. It is found that an initial random coil conformation of the SF can be readily changed into an ordered beta-sheet structure by optimizing the solution conditions, such as the SF concentration, pH, temperature, or metal-ion content. Circular dichroic spectra quantitatively confirm a steadily decreased content of the random coil conformation but a significantly increased beta-sheet content after an ultrasonic or extruding treatment. Furthermore, the extrusion is more powerful to achieve high beta-sheet content than the ultrasonic. It is interesting that the polarized optical micrographs of the SF aqueous solution extruded by injection illustrate the formation and existence of liquid crystalline state. A study of extrusion in vitro could be used as a model system to understand the natural silk spinning process in silkworm.

Naturally functionalized silk as useful material for photonic applications

“…In particular, it was demonstrated that in typical silk solution the fluorescence spectrum profile can be attributed to tyrosine, tryptophan and crosslinks emission components which are differently weighted according to the conformational states of silk fibroin, and thus to the different silk forms [25,26].…”

Self‐assembly of regenerated silk fibroin from random coil nanostructures to antiparallel β‐sheet nanostructures

“…Ultrapure water measured under the same experimental conditions was subtracted from the data. Ellipticity [ θ ] is expressed in units of deg·cm 2 dmol −1 using the Yang equation: where θ obs is the observed ellipticity value in degrees, the value 78 is the mean residue molecular mass taken from sequence data for SF, l is the optical path length in centimeters, and c is the SF protein concentration in g/mL.…”

Preparation of regenerated silk fibroin/silk sericin fibers by coaxial electrospinning

“…Moreover, the SF/SS fiber had another two characteristic bands at 1085 cm −1 and 1680 cm −1 . The former was assigned to the ␤-sheet conformation [44,45] and the latter was assigned to the intermediate conformation related to the ␤-sheet. By contrast, for the pure SF fiber, these two bands were exhibited weakly as shoulder peaks.…”