146 Q) +-' ·;;::: Q) "'C "'C C N 4950 JOURNAL OF COSMETIC SCIENCE 4900 4850 4800 4750 Wavenumber/ cm- 1 Figure 5. Second derivaties of the spectra shown in Figure 3 in the 4950-4750 cm- 1 region. Thin solid line: untreated hair. Dotted line: hair treated with MA/BOE/ethanol solution for 20 min. Dashed line: hair treated for 40 min. Thick solid line: hair treated for 60 min. to the higher wavenumber from the center of the protein band. This suggests the existence of other components, having lower wavenumbers in the protein band, which are to be identified in the following asynchronous 2D correlation study. THE ASYNCHRONOUS 2D CORRELATION MAP The asynchronous cross peaks develop only if the basic trends of dynamic spectral variations observed at two different wavenumbers of the cross peaks are dissimilar (12,16). Figure 7 depicts an asynchronous 2D NIR correlation map corresponding to the synchronous map of Figure 6. The wavelength range is limited from 4950 to 4750 cm- 1 for the sake of detailed analysis of the protein band here. From the asynchronous cross

INTERACTION BETWEEN HAIR PROTEIN AND ORGANIC ACID 147 800 900 5000 5100 . ..... .... 5200 L-----�1---........--1,----,------,,---�---,--5300 5300 5200 5100 5000 4900 4800 Wavenumber/ cm-1 T""" I E (.) ..._ L... Q) ..c E ::::J C Q) m s Figure 6. Synchronous 2D NIR correlation spectrum in the 5300-4750 cm- 1 region constructed from treatment-time-dependent spectral changes in hair. Dotted lines through the tops of the cross peaks show which bands correlate with each other. All the correlation peaks are positive. peaks, it can be clearly seen that the protein band, which is apparently one peak, is composed of more than three bands. The three bands, around 4890, 4850, and 4810 cm- 1 are referred to as band A, band B and band C, respectively. The map shows clear correlations between A and B, and A and C. These three bands seem to be different in the strength of their hydrogen bonds with the NH of the protein amides. According to the consideration described before, it can be said that band A is the band having no or the weakest hydrogen bond, band B is in the middle, and band C is the strongest. ASSIGNMENT OF THE DECONVOLUTED PROTEIN BANDS The wavenumber of band A, 4890 cm - l, is the same as that of the band correlating with the water band in the synchronous correlation map (Figure 6). The sign of the cross peaks