SDS-PAGE and western blot analysis of full length SARS CoV-2 N 3′ 6X-HIS, produced in E. coli, purified by affinity chromatography and formulated. Full length SARS CoV-2 N is expressed as a ca. 50 kDa polypeptide. A ca. 28 kDa proteolytically cleaved fragment co-purifies with full length N and is visible in SDS-PAGE (lane 2) and in western blots probed with an anti-6X-HIS antibody reagent (lane 3). SDS-PAGE molecular weight marker (lane 1) and western blot marker (lane 4) are shown for size estimation.