Fig 1.
Chemical structure of oxalic acid.
Table 1.
The active binding sites of Delta RBD-ACE2 complexes.
Table 2.
The active binding sites of Omicron RBD-ACE2 complexes.
Fig 2.
Effects of OA on the interaction between ACE2 and SARS-CoV-2 Spike RBD from Delta (B.1.617.2) and Omicron (B.1.1529).
Representative inhibitory curves of ACE2 binding to SARS-CoV-2 RBDs of Delta RBD (A), Omicron RBD (B) in the presence of OA determined by ELISA.
Fig 3.
Effect of OA on ACE2h cell viability.
ACE2h cells were pretreated with different doses of OA and incubated for 24 h. Viability of ACE2h cells was detected at OD450nm. The proliferation ration was calculated. The experiments were repeat three times. Data are presented as mean ± SD.
Fig 4.
The effect of OA on the entry of SARS-COV-2 Delta (B.1.617.2) pseudovirus into ACE2h cells.
(A) The entrance of SARS-CoV-2 Delta pseudovirus into ACE2h cells was evaluated by the luciferase activity after treated with ACE2-Fc and different concentrations of OA. (B) Inhibition rate was calculated and showed in curves. (C) Representative images were photographed at × 4 magnification using the fluorescence microscope. Data were presented as mean ± S.D. **p < 0.01, ***p < 0.001, compared with control.
Fig 5.
The effect of OA on the entry of SARS-COV-2 Omicron (B.1.1.529) pseudovirus into ACE2h cells.
(A) The entrance of SARS-CoV-2 Delta pseudovirus into ACE2h cells was evaluated by the luciferase activity after treated with ACE2-Fc and different concentrations of OA. (B) Representative images were photographed at × 4 magnification using the fluorescence microscope. Data are presented as mean ± S.D. *p <0.05, **p < 0.01, ***p < 0.001, compared with control.
Fig 6.
The binding characters of OA on ACE2 and RBDs of Delta and Omicron.
The SPR titration curves of OA interacted with ACE2 protein (A), Delta RBD protein (B) and Omicron RBD protein (C) were shown. The affinity constants of OA to Delta, Omicron and ACE2 protein were calculated and presented (D).
Fig 7.
SARS-CoV-2 Delta or Omicron spike protein in complex with human ACE2.
Delta (A) and Omicron (B) RBD binding to ACE2 interface were marked.
Fig 8.
Molecular docking of OA with RBD-ACE2 binding interfaces.
The predicted binding sites of OA to the complex of ACE2 with Delta (A) or Omicron (B) RBD were shown.
Table 3.
The interaction energy of different conformation of OA interacted with RBD-ACE2 complexes of Delta or Omicron.
Table 4.
The predicted binding sites of OA interacted with ACE2 and RBD of Delta or Omicron complexes.