Interaction of a spinach protein factor with bacteriochlorophyll

Abstract

1. The absorption spectrum of colloidal bacteriochlorophyll gradually changes from one with two absorption maxima in the near infrared part of the spectrum into one with a single maximum in this region. This conversion is accelerated by a spinach protein factor. Spinach protein factor also causes a shift of the single remaining absorption maximum to a shorter wavelength. 2. The change in the absorption spectrum, together with results of experiments on dilution of aqueous colloidal bacteriochlorophyll with methanol suggest that colloidal bacteriochlorophyll may exist in two different forms, one with two maxima in its near infrared absorption spectrum (about 790 and 847 nm) and one with a single maximum in this region (775 nm). 3. Light sensitivity of the bacteriochlorophyll-spinach protein factor complex is highest if the colloidal bacteriochlorophyll is completely converted into the form with a single absorption maximum in the far-red part of the spectrum. 4. The light sensitivity of the bacteriochlorophyll-spinach protein factor complex depends on ionic strength and pH. The experimental results indicate that a positively charged site of bacteriochlorophyll combines with negatively charged spinach protein factor. 5. The elution pattern obtained on filtration of spinach protein factor through Sephadex G-100 is dependent on the buffer used.