Substructures of paired helical filaments from Alzheimer's disease neurofibrillary tangles.

Presented studies reveal that each of the approximately 10 nm filaments forming the paired helical filaments (PHF) is made up of four protofilaments. Each of the protofilaments is a beaded structure, consisting of globules connected by longitudinal bars. A cross-view of PHF shows eight globules linked by transverse bars. The transverse bars are shorter than the longitudinal bars. Comparison between PHF and neurofilament protofilaments indicates structural differences between these profiles, i.e., the globules making the PHF protofilaments are larger and the longitudinal bars are longer than those in the normal neurofilaments. A three-dimensional diagram of PHF structure is presented.