sentences:  HSE-up is defined as the number of Cα atoms in the
  upper half (containing the pseudo-Cβ atom) and analogously HSE-down is defined as the number of Cα atoms
  in the opposite sphere.If only Cα atoms are available (as is the case for many simplified representations of protein structure), a related measure, called HSEα, can be used.HSEα uses a pseudo-Cβ instead of the real Cβ atom for its
  calculation.