[Chimera-users] Measure angle and effect length

Hi, What is the correct way to measure the angle between the EGF and Lectin domain of L-selectin: 3CFW and also the effective length of those domains? What is the difference between Helical correction and mass weighting? When should I use Helical correction and mass weighting? How is the length of the axis is determined? Is there a way to pick the length of the axis to be the effective length of the domain? Thanks