Direct observation of phosphorylase kinase and phosphorylase b by scanning tunneling microscopy

The molecular structures of phosphorylase b and phosphorylase kinase have been visualized by scanning tunneling microscopy (STM). STM is a near field technique that can resolve structures at the nanometer level and thus can image individual molecules. Phosphorylase b can be seen in dimeric and tetrameric forms as well as linear and globular aggregates. The linear arrays consist of side by side dimers with the long axis of the dimer perpendicular to the aggregated chain. Individual molecules of phosphorylase kinase appear to be planar, bilobate structures with a 2-fold axis of symmetry and a central depression.