Keratinous fibers from various sources had been used for the adsorption studies of metal ions such as Cu, Zn, Pb, Cr, Hg, Ag, and others. These fibers were found to chelate metal ions by introducing chemical treatment to the hair fibers which allows better penetration of the metal ions into the hair fiber, or by disrupting the disulfide bonds in hair which produces free thiol groups. However, there were no quantitative data to explain the improved binding of metal ions to keratinous fibers after chemical treatment. Furthermore, there were no articles that gave a direct correlation between the thiols in keratin to the binding of metal ions. Although it is well known that thiols in cysteine bind well to metal ions, cysteine residues in proteins might have a different characteristic under different conditions. This could be due to the folding of proteins or interference from neighboring groups affecting the reactivity of thiols in cysteine. Therefore, the hypothesis of this project is that thiols in keratin are the main functional group responsible for the binding of metal ions to human hair keratin. The objectives of this project are to find out the functionality of thiol in extracted human hair keratin for the binding of metal ions. Keratin were extracted from human hair fibers using reduction method through thiol disulfide exchange with another thiol compound. Quantification of protein and thiol concentration were done by Bradford and Ellman's assays, respectively. The assays were selected as they are less prone to interference and requires relatively short incubation time below 20 minutes. The extracted keratins were subjected to different pH treatments and it was found that an acidic pH gave the best physical behavior and highest amounts of functional thiol groups, at about 1 mmol/g. Subsequently, keratin in acidic pH were used for the interaction studies with copper (II) ions to find out the relationship between copper and thiol concentrations.