Updated publication reference for PubMed record(s): 29950687. Ribosomal purifications of spinach 70S ribosome and human 40S and 60S ribosomal subunits were analyzed with bottom-up LC-MS/MS to identify proteins comprising purified complexes as well as co-purified proteins. In order to assess and quantify proteoforms of ribosomal proteins in ribosomal purifications we employed top-down LC-MS/MS techniques with optimized methods, wherein apart from standard parameters (e.g. collision voltage and dynamic exclusion time) high-resolution and low-resolution were alternately employed in full MS mode.