Glycated hemoglobin (GHb) is the indicator of the long‐term glycemic index of an individual. GHb is formed by the irreversible modification of N‐terminal α‐amino group of β globin chain with glucose via Amadori rearrangement. Cation exchange chromatography exploits the difference in surface charges between GHb and native hemoglobin (HbA₀) for their separation and quantification. However, glucose condensation is specific to primary amino groups. Therefore, structural characterization of GHb synthesized in vivo is essential as multiple glycation may interfere with GHb assessment. The stoichiometric composition of different glycated hemoglobin from a 19% GHb sample was deduced using native mass spectrometry. We observed a comparable population of α and β glycated tetramers for mono‐glycated HbA₀. Surprisingly, doubly and triply glycated HbA₀ also showed mono‐glycated α and β globins. Thus, we propose that glycation of hemoglobin (HbA) occurs symmetrically across α and β globins with preference to unmodified globin first. Correlation between conventional and mass spectrometry‐based quantification of GHb showed a reliable estimation of the glycemic index of individuals carrying HbA₀. Mutant HbAs have different retention time than HbA₀ due to the differences in their surface charge. Thus, their glycated analog may elute at different retention time compared to GHb. Consequently, our method would be ideal for assessing the glycemic index of an individual carrying mutant HbA.

The infection caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) resulted in a pandemic with huge death toll and economic consequences. The virus attaches itself to the human epithelial cells through noncovalent bonding of its spike protein with the angiotensin-converting enzyme-2 (ACE2) receptor on the host cell. We hypothesized that perturbing the functionally active conformation of spike protein through reduction of its solvent accessible disulfide bond, thereby disintegrating its structural architecture, may be a feasible strategy to prevent infection. Proteomics data showed that N-acetyl cysteine (NAC), an antioxidant and mucolytic agent been widely in use in clinical medicine, forms covalent conjugates with solvent accessible cysteine residues of spike protein that were disulfide bonded in the native state. In silico analysis indicated that this covalent conjugation perturbed the stereo specific orientations of the interacting key residues of spike protein that resulted in threefold weakening in the binding affinity of spike protein with ACE2 receptor. Antiviral assay using VeroE6 cells showed that NAC caused 54.3% inhibition in SARS-CoV-2 replication. Interestingly, almost all SARS-Cov-2 variants conserved cystine residues in the spike protein. Our observed results open avenues for exploring in vivo pharmaco-preventive and therapeutic potential of NAC for Coronavirus Disease 2019 (COVID-19).