Spike Protein Cleavage-Activation in the Context of the SARS-CoV-2 P681R Mutation: an Analysis from Its First Appearance in Lineage A.23.1 Identified in Uganda oleh Bailey Lubinski, Laura E. Frazier, My V. T. Phan, Daniel L. Bugembe, Jessie L. Cunningham, Tiffany Tang, Susan Daniel, Matthew Cotten, Javier A. Jaimes, Gary R. Whittaker