The content of protein in the feather and the obtained keratin
were determined by hydrolysis with 6 mol/L HCl solution to produce
amino acids at the reflux temperature of about 105 C during 24 h.
Then the total amino acids were analyzed by amino acid analyzer
(AAA-Direct, DIONEX) and the measuring condition is the same as
that described in the previous paper [26]. The FTIR spectrum of keratin
was measured on an Avater370 FTIR spectrograph (Nicolet Co.,
USA) by KBr method. The molecular weight of extracted keratin was
determined by gel permeation chromatography (GPC) (HP-1100)
system, which consists of a Phenogel mixed column and a RID
(G1362A) detector. THF was used as a mobile phase at a flow rate
of 1.0 mL/min and the injection volume was 20 lL. Calibration of
GPC was carried out with a standard polystyrene sample