[Spectrum analysis of blue to purple membrane transition induced by diverse valent cations].

The visible difference spectra, M412 yield and M412 decay lifetime in blue membrane (bM) to purple membrane (pM) transition induced by Na+ , Mg2+ and Tb3+ metal ions were characterized. The transition ability from bM to pM induced by Tb3+ , Mg2+ and Na+ has distinguished difference, their concentration ratio at the midpoint of ion-induced absorbance changes is 1:2.5:650. Meanwhile, the curve of absorbance changes at 540 nm is similar to that of M412 yield changes in bM to pM transition. The M412 decay lifetime of regenerative pM induced by Tb3+ was prolonged remarkably when more Tb3+ was added. However, for the other two ions, additional ions have no effects on its lifetime. These results suggest that diverse valence metal ions exist in different binding ways from pM.