Uv absorption spectra of Lys in the buffer with 3.4, 7.4, and 9.0 were shown in Fig. 1. It can be seen that its inten sity decreases gradually from pH 3.4 to 9.0, and an apparent blue shift of the maximum absorption wavelength from 199 nm (pH 7.4) to 195 nm (pH 3.4) and an apparent red shift from 199 nm (pH 7.4) to 204 nm (pH 9.0) was observed. The literature l14] shows that the peak in the 200 nm region in the difference spectra of proteins is related to changes in the conformation of the peptide backbone associated with the helix-coil transformation (15]. The above results suggest that the conformation of Lys molecule is al tered when the pH is changed from simulating physiological (pH 7.4) to acidic (pH 3.4) or basic (pH 9.0) conditions. Three-dimensional fluorescence spectra have become a popular fluorescence analysis technique in recent years (16l. It is well known that three-dimensional fluorescence spectrum can provide nuore detailed information about the change in the conformation of proteins. Fig. 2 presents the contours of three-dimensional fluores- cence spectra under three different pH conditions (pH 3.4, 7.4, and 9.0) and the corresponding data are shown in Table 1. In Fig. 2, two