Submitted to: Journal of Molecular Structure (Theochem)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/25/2010
Publication Date: 4/22/2010
Citation: Cardamone, J.M. 2010. Investigating the microstructure of keratin extracted from wool: peptide sequence (MALDI-TOF/TOF) and protein conformation (FTIR). Journal of Molecular Structure (Theochem). 969:97-105.
Interpretive Summary: There is new market potential for domestic wool as a source of over 90% pure keratin proteins. Whereas solid-state chemical modification of wool to improve its properties has severe limitations, solution state chemical modification of keratin, as a model for wool, will expand wool science. We found a method to extract keratin from wool without degrading it. Fine grade wool fibers were digested in a controlled reaction system with a reducing agent and assisting reagents that were effective in solubilizing wool while preserving its chemical and structural integrity at the molecular level. We used methods of analysis to show that the molecular weight of the extracted keratin was the same as the untreated keratin of the wool starting material. We applied instrumentation to examine the native wool and the extracted keratin from wool and found that their proteins were identical. We could identify the proteins’ origin as having been extracted from the inner core of the wool fiber which allowed the fiber to break down into smaller protein segments but preserved the same protein composition intact. Further examination involved determining the potential for the extracted keratin to be used in products that require requisite mechanical strength. We used instrumentation to show that the extracted protein has structure similar to the native keratin. Thus the extracted keratin is a suitable starting material for subsequent modification in product development to form mats, scaffolds, gels, etc. for topical and implantable biotechnical applications that require keratin to exhibit molecular orientation for flexibility and strength.
Technical Abstract: Keratin was extracted from wool by reduction with 2-mercaptoethanol. It was isolated as intact keratin and characterized by its similar molecular weight, protein composition, and secondary structure to native keratin. Gel electrophoresis patterns and MALDI-TOF/TOF peptide sequences provided the identity of the intact keratin as protein homologs: Type II microfibrillar component 7C; Type I microfibrillar 48kDa component 8C-1, and Type I microfibrillar 47.6 kDa proteins. Type II microfibrillar, component 7C protein components of native keratin and keratin hydrolysate were high in alanine, glutamine, glutamic acid, leucine, and glycine amino acid. Keratin Type II microfibrillar (fragment) showed highest glutamic acid and leucine. Keratin Type I microfibrillar 48kDa, component 8C-1 and Keratin, Type I microfibrillar 47.6kDa keratins were high in asparagine, valine, proline, alanine, glutamine, glutamic acid, arginine, threonine, and leucine. The compositions of these protein homologs matched those found in native keratin. Relative FTIR absorptions of native keratin and keratin hydrolyzed by reduction in the amide A, B (3300 – 3050 cm-1), amide I (1600-1700 cm-1), amide II (1545- 1450 cm-1), and amide III (1230-1250 cm-1) regions analyzed by peak resolution showed less hydrogen bonding, greater amide I content and higher a-helical and ß-sheet conformations for hydrolyzed keratin. The higher content of a-helical and ß-sheet secondary structure of intact keratin characterized it as viable starting material for flexible and strong novel keratin products of various shapes and forms such as porous foams, sponges, mats, and films in applications as bio-based, adaptable structures.