Reconstruction of rod self-aggregates of natural bacteriochlorophylls-c from Chloroflexus aurantiacus

Bacteriochlorophyll(BChl)s-c were extracted, isolated and purified from cultured cells of a green photosynthetic bacterium, Chloroflexus (Cfl.) aurantiacus. Their self-aggregates were prepared from a hydrophobic hexane-based solution and the obtained self-aggregate solids were examined by electronic absorption and circular dichroism (CD) spectroscopy as well as atomic force microscopy (AFM). Visible/near-infrared absorption and CD spectra of the BChl-c self-aggregates were very similar to those in cells of Cfl. aurantiacus. AFM analysis indicated that some self-aggregates had rods with a 5-nm diameter and a 3.5-μm length at longest. The rod diameter was identical to that reported for natural chlorosomal rods of Cfl. aurantiacus. Rod self-aggregates of naturally occurring BChls-c with a 5-nm diameter were first reconstructed here in vitro.