The keratin extraction from human hair fiberswas prepared according
to the reportedmethods with some modifications [24,25]. Briefly, human
hair was washed with ethanol and external lipids were removed using a
mixture of chloroform/methanol (2:1, v/v) for 24 h. The delipidized
hair (100 g) was mixed with 25 mM Tris–HCl solution (1.5 L, pH 8.5)
containing 2.6 M thiourea, 5 M urea, 75 g SDS and 5% 2-mercap
toethanol at 50 °C for 3 days. After the mixture was filtered and
centrifuged at 15,000 ×g for 20 min at room temperature, the obtained
supernatant was dialyzed against deionized water using cellophane tubing
(molecular weight cutoff of about 10 kDa) and the outer water was
replaced with distilled water twice a day. The extracted keratins
were identified by using sodium dodecyl sulfate-polyacrylamide gel electrophoresis
(SDS-PAGE) and Fourier transform infrared spectroscopy
analyses.