EUCALYPTUS EXTRACT-INDUCED HAIR CHANGES 495 In order to carry out the area-selective Young's modulus measurement and analysis of the hair structure, we selected the nano-indentation mode of AFM. Previously, nano­ indentation has been used to compare differences between different components of keratin fibers, such as the cortex and cuticle, or between subcomponents, such as the exo­ and endocuticle (25). Until now, measurement of physical properties, such as the bend­ ing elasticity of the cortex, has been achieved after removing cuticle layers from the hair shaft by various preprocessing methods (20). As the presence of the medulla in Japanese hair and its influence on mechanical properties could not be disregarded, the interpre­ tation of the analytical result was difficult. By use of the nano-indentation method, evaluation of the physical properties of each component in the hair, such as medulla, cortex, and cuticle, becomes possible in the intact condition without undergoing re­ duced pressure, as is the case in observation by TEM. For this reason, the nano­ indentation method seems to be a powerful method for not only comparison of me­ chanical properties, such as before- and after-perm processing, but also for the compara­ tive study of the physical properties of hair between different ethnic groups. According to any interpretation of the analytical results of the secondary structure of the protein by IR microscopy, changes in the physical properties of hair with Eucalyptus extract are caused by an increase in the beta structure in the cortex, since the molar fraction of the beta structure in the cortex increases in the new-growth part of the hair treated with Eucalyptus extract scalp lotion. Until recently, it has been thought that an increase or a change in the alpha structure of the proteins that compose IFs plays a major and essential role in the improvement of mechanical properties, such as the improvement in Young's modulus. In recent years, however, it has become clear that the physical and mechanical character (stiffness and flexibility) of a globular protein is affected more by the beta structure than the alpha structure. Analysis by supersonic wave spectroscopy makes clear that the beta structure is a stronger structure in comparison to the alpha structure (28-32). In other words, an increase in the alpha structure, which shows a strong mechanical molecular configuration, generates "distortion for the entire molecule" the deterioration of physi­ cal and mechanical properties will be caused by this distortion. From this viewpoint, it can be considered that the increase in the Young's modulus of the hair fibers in this study originates through an increase in the beta structure. More­ over, in the case of the protein that composes the hair, it is thought that the beta structure exists in/around KAP. It can be said that a new aspect has opened from this study, in that we suggest that the matrix proteins play an essential role in the mechanical and physical properties of hair. Further investigations are necessary to confirm or deny our interpretations of the changes in hair proteins, such as conformations and configu­ rations, since proteins are the main components of hair and have a large influence on hair properties. REFERENCES (1) Biotechnology in Agriculture and Forestry, Y.P.S. Bajaj, Ed. (Springer-Verlag, Berlin), Vol. 4, Medicinal and Aromatic Plants I (1988) Vol. 7, Medicinal and Aromatic Plants II (1989) Vol. 15, Medicinal and Aromatic Plants Ill (1991). (2) E. Wakisaka, et al., 32nd Annual ESDR Meeting, September 19-21, 2002. (3) G. Imokawa, et al.,]. Invest. Dermatol., 96, 523-526 (1991).

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