The protein used for SAXS contains an N-terminal polyhistidine-SUMO tag (Ubiquitin-like protein SMT3 UniProt Q12306, amino acids 3-98; R64T, R71E) that span amino acids 1-111 of the SAXS construct. The bacterial non-heme ferritin protein begins at position 112 of the SAXS construct and spans amino acids 5-167 of the canonical amino acid sequence of the protein with two point mutations N19Q + I59V (numbering relative to UniProt Q9ZLI1).