RESOLUTION OF THE FLUORESCENCE-SPECTRA OF PLANT PIGMENT-COMPLEXES USING TRILINEAR MODELS

The intensity of fluorescence from a pigment is separately linear in functions of excitation wavelength, emission wavelength, and any chemical treatment which alters overall fluorescence yield. This multiple linearity permits the use of an extension of principal components analysis to resolve overlapping spectra without the use of any additional information. The method is used to resolve the spectra of pigment complexes in pea thylakoids, using the concentration of Mg2+ as the chemical treatment variable. Two components could be resolved accurately. One has little or no dependence on Mg2+; the other, with an excitation spectrum resembling LHC II, has a dependence on Mg2+ which follows the Hill equation with a binding constant of 0.4-0.6 mM and a Hill coefficient of 2.4-3.1.