Defect Mass in Gravitational Field and Red Shift of Atomic and Nuclear   Radiation Spectra
  It is shown, that radiation spectrum of atoms (or nuclei) in the gravitational field has a red shift since the effective mass of radiating electrons (or nucleons) changes in this field. This red shift is equal to the red shift of radiation spectrum in the gravitational field measured in existence experiments. The same shift must arise when the photon (or $ \gamma $ quantum) is passing through the gravitational field if it participates in gravitational interactions (photon has no rest mass). The absence of the double effect in the experiments, probably, means that photons (or $ \gamma $ quanta) are passing through the gravitational field without interactions. 
Kh.M. Beshtoev