2.7. Determination of SH-Group Content and Protein Leakage from Hair Shaft
The distal pieces of cut hairs were used to analyze the content of thiol groups (SH-groups) in small labile proteins leaking from the hair shaft, as well as the content of leaking proteins themselves. In brief, hair pieces were weighted and 2–3 mg of hairs was placed into 0.75 mL 0.1 M potassium phosphate buffer (pH 7.4), destroyed in a glass homogenizer, and centrifuged to sediment the particles of the destroyed hairs. The supernatants were analyzed for protein and SH-group contents. The supernatants (0.35 mL) were mixed with TRIS buffer (0.65 mL, pH 8.9) and 25 μL of DTNB solution. Then, SH-groups were determined with the HPLC technique on a HPLC Shimadzu SCL-10AV (Shimadzu Europa GmbH, Duisburg, Germany) chromatograph equipped with array photodiode and electrochemical detection, as described previously [The protein content was measured by the Bradford method [