THE PRESSURE-INDUCED STRUCTURAL-CHANGE OF BOVINE ALPHA-LACTALBUMIN ASSTUDIED BY A FLUORESCENCE HYDROPHOBIC PROBE

The effect of pressure on bovine a-lactalbumin (LA) has been investiga ted by fluorescence methods. The intrinsic fluorescence spectra of hol e-LA (Ca-II-bound LA) hardly changed in its intensity and maximum wave length on increasing the pressure up to 400 MPa. In the intrinsic fluo rescence spectrum of ape-LA (Ca-II-depleted form) the maximum waveleng th was red-shifted, and the intensity was increased to a large extent by increasing pressure. The fluorescence titrations of both forms of L A were performed with a fluorescent hydrophobic probe 1,1'-bis(4-anili no)naphthalene-5,5'-disulfonate (bis-ANS) at various pressures, and bi nding constants (K-b) of bis-ANS were calculated. The K-b-value for ho le-LA slightly decreased from 0.1 to 100 MPa and increased above 200 M Pa. The K-b value for apo-LA gradually increased with increasing press ure up to 400 MPa. These results were explained by the difference in h ydrophobic characteristics of hole- and apo-LA. (C) 1996 Munksgaard 19 96.