1H15N-HSQC spectra of the Marburg virus GP2 fusion loop (MGP2-FL) and secondary structure propensity (SSP)–based comparison with the Ebola virus (EBOV) GP2 FL. A, Overlay of HSQC spectra of MGP2-FL at pH 4 in 1,2-dimyristoyl-sn-glycero-3-phosphocholine/1,2-dihexanoyl-sn-glycero-3-phosphocholine (DMPC/DHPC) bicelles (blue) and n-dodecylphosphocholine (DPC) micelles (red). B, Overlay of HSQC spectra of MGP2-FL in DMPC/DHPC bicelles at pH 4 (blue) and pH 7 (green). Peaks marked with asterisks belong to the polyhistidine tag region in the construct. C, Comparison of the SSP [30] of MGP2-FL in DMPC/DHPC bicelles at pH 4 (blue) and EBOV GP2 FL in DPC at pH 5.5 (red). SSP values of EBOV GP2 FL were calculated using reported chemical shifts in previous work by Tamm et al [21]. Abbreviation: ppm, parts per million.