Influence of alkyl chain substitution of ammonium ionic liquids on the activity and stability of tobacco etch virus protease

Decamethoxin virucidal activity: in vitro and in silico studies

The data on the representative of decamethoxin short-term action on infectious bronchitis virus (IBV) strain H120 used as a human-safe model of SARS-CoV-2 virus are presented. The viral activity was estimated with the use of inverted microscope PrimoVert (Germany) by destructive effect on BHK21 fibroblastic cell line. In vitro results demonstrated that decamethoxin (100 μg/ml) completely inactivated IBV coronavirus strain at exposure of 30 sec and more. At the lowest decamethoxin exposure of 10 sec the antiseptic virucidal activity was 33% and 36% of control at 24 and 48 h of cultivation respectively. Molecular docking analysis indicated the significant similarity of IBV and SARS-CoV-2 main protease (Mpro) structure. Docking studies of decamethoxin interaction with IBV Mpro and SARS-CoV-2 Mpro active centers demonstrated the ligand-protein complexes formation with the estimated binding energy of -8.6, -8.4 kcal/mol and key amino acid residues ASN26, GLY141, GLU187, GLU164, THR24, THR25, ASN142, GLY143, CYS145, HIS164 and GLU166. Keywords: decamethoxin, IBV strain H120, main protease, mole­cular docking, QAC, SARS-COV-2, virucidal activity

An Overview on the Recent Advances in Alternative Solvents as Stabilizers of Proteins and Enzymes

Currently, the use of alternative solvents is increasing, namely ionic liquids (ILs) and deep eutectic solvents (DESs) in diverse fields of knowledge, such as biochemistry, chemistry, chemical engineering, biotechnology and biomedicine. Particularly, when compared to traditional solvents, these alternative solvents have great importance for biomolecules due to the enhanced solubility, structure stability and the biological activity of biomolecules, such as protein and enzymes. Thus, in this review article, the recent developments and efforts on the technological developments carried out with ILs and DESs for the stabilization and activation of proteins and enzymes are provided. The most studied IL- and DES-based formulations for proteins and enzymes are discussed and the molecular mechanisms and interactions related to the increased stability promoted by these alternative solvents are disclosed, while emphasizing their main advantages.

On the Stability and Conformational Dynamics of Cytochrome c in Ammonium Ionic Liquids

Owing to their potential applications in the extraction, purification, and preservation of biomolecules and biocatalysis, ionic liquids (ILs) have gained great attention in biotechnology. Although it is known that the structure and dynamics of proteins in ILs depend on the nature of both proteins and ILs, the biophysical mechanism governing the protein-IL interaction, which determines the stability of proteins or the activity of an enzyme in these nonconventional media, is yet to be understood clearly. Herein, we study the effect of two ammonium ILs, triethylammonium dihydrogen phosphate (TEAP) and tributylammonium dihydrogen phosphate (TBAP), on the stability and conformational dynamics of cytochrome c (Cyt c) in its native and unfolded states, employing primarily the single molecule-based fluorescence correlation spectroscopy (FCS) technique. The results show that the native structure of Cyt c is not significantly altered by TEAP, but the tertiary structure is perturbed to a great extent by TBAP, which comprises a longer alkyl chain. Fluctuations of the fluorescence intensity of Alexa488 dye-labeled Cyt c in FCS measurements reveal conformational dynamics (67 ± 10 μs) in the native state of Cyt c that is accelerated in the presence of both ILs but not affected when Cyt c is in its unfolded state. The present findings demonstrate how the stability of this protein can be modulated by using ammonium ILs of different alkyl chain lengths.