Note these papers contain the recommendations that in order to prove material banding at 1.16 g/ml is retroviral, it should be subjected to the following assays:
(a) physical‑‑EM for virus count, morphology and purity;
(b) biochemical‑‑RT activity, viral and cellular RNA, total protein, gel analyses of viral and host proteins and nucleic acids;
(c) biological‑‑infectivity in vivo and in vitro.
And there should be "No apparent differences in physical appearances" between the particles seen.
1. Sinoussi F, Mendiola L, Chermann JC. Purification and partial differentiation of the particles of murine sarcoma virus (M. MSV) according to their sedimentation rates in sucrose density gradients. Spectra 1973;4:237-243. View HERE.
2. Toplin I. Tumor Virus Purification using Zonal Rotors. Spectra 1973:225-235. View HERE.