Structure with a light touch

Like a blind man tapping around a neighborhood, Svetlana Bahatyrova, Raoul Frese (University of Twente, Enschede, Netherlands), Neil Hunter (University of Sheffield, UK), and colleagues have used atomic force microscopy (AFM) to picture the organization of a photosynthetic membrane. The arrangement explains how light energy is channeled from antenna-like collectors to an energy-transforming reaction center (RC) complex.

When the structure of the RC was solved in 1985 it was the first X-ray structure of a membrane protein. X-ray structures of the other photosynthetic complexes—the light harvesting LH1 and LH2 complexes—followed. But, says Hunter, “it was a bit like a jigsaw—nobody had seen how the pieces were put together.”

Light energy is initially absorbed by LH2 complexes, each of which is a ring of ∼27 chlorophylls and...