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. 2021 Dec 9;12:765211. doi: 10.3389/fimmu.2021.765211

Figure 2.

Figure 2

Biophysical characterization of mRBD1-3.2 and pRBD3-3.2. (A–D) Characterization of mRBD1-3.2 by (A) SDS-PAGE. SPR assays for binding to (B) ACE2, (C) CR3022, and (D) SEC-MALS to estimate molecular mass. (E–H) Corresponding data for pRBD3-3.2. Comparison of thermal stability of purified (I) mRBD1-3.2 and (J) pRBD3-3.2 estimated using nano-DSF. (K) Extended thermal stability. Lyophilized mRBD1-3.2 and pRBD3-3.2 were stored at 37°C for 1 month, the lyophilized powder was resolubilized in PBS, and the amount of folded protein was estimated by its binding to ACE-2 hFc using SPR. RU is plotted after 200 s of association with ACE-2. (L) Reducing SDS-PAGE analysis of mRBD1-3.2 (i, iii) and mRBD1-3.2-beta (ii, iv) stored at -80°C for over a month and at 4°C for 3 days, respectively.