Theoretical investigation on the binding specificity of fluorinated sialyldisaccharides Neu5Acα(2–3)Gal and Neu5Acα(2–6)Gal with influenza hemagglutinin H1 – A Molecular Dynamics Study

Structural and binding studies of 2'- and 3-fucosyllactose and its complexes with norovirus capsid protein by molecular dynamics simulations

Human breast milk contains free oligosaccharides (Human Milk Oligosaccharides-HMOs) that help to protect breastfed infants against a variety of infectious diseases and act as decoy receptors. In breast milk, HMOs are the third most abundant compounds after lactose and lipids. Structural and conformational models of HMOs are quite crucial to studying the interaction with proteins and molecular recognition phenomenon. Molecular dynamics simulations for two trisaccharides HMOs (2'-FL and 3-FL) were carried out for 250 ns and the conformational models were subsequently substantiated by three replicate simulations. The conformer models of HMOs 2'-FL and 3-FL were deposited in the 3-Dimensional Structural Database for Sialic acid-containing CARbohydrates (3DSDSCAR) database website (www.3dsdscar.in). HMOs were then docked into the active site of norovirus capsid protein and are simulated for 100 ns duration. Each complex system was stabilized by direct and water-mediated hydrogen bonding interactions. Binding free energy calculations predict two possible binding modes for each complex system. The conformational flexibility and binding stability of the complex systems were calculated. The protein folding/unfolding and compactness seem to be better for the two HMOs. From a general perspective, we found that both 2'-FL and 3-FL exhibited higher binding efficacy towards norovirus capsid protein and according to the structural stability, 3-FL might be used as a preventive inhibitor for norovirus infection.Communicated by Ramaswamy H. Sarma.

Investigation on the Binding Properties of N1 Neuraminidase of H5N1 Influenza Virus in Complex with Fluorinated Sialic Acid Analog Compounds—a Study by Molecular Docking and Molecular Dynamics Simulations

Worldwide, only two types of antiviral inhibitors (M2 ion channel protein inhibitor and Neuraminidase inhibitors) are approved to treat the influenza viral infection. But the mutation of amino acid sequence in the viral membrane proteins creates the viral resistance to existing antiviral drugs or inhibitors. So the corresponding antiviral drugs have to be reformulated to match these antigenic variations. Fluorination on the carbon–based molecule significantly enriches its biological properties. Hence this study is motivated to design the fluorinated sialic acid (SIA) analog inhibitors for the neuraminidase of H5N1 influenza A virus by substituting fluorine atom at different hydroxyls (O2, O4, O7, O8, and O9) of sialic acid. 100 ns molecular dynamics simulations are carried out for each protein–ligand complex system. NAMD pair interaction energy and MM–PBSA binding free energy calculations predict two possible binding modes for N1–SIA_F2, N1–SIA_F4, and N1–SIA_F7 complexes and single binding mode for N1–SIA_F8 and N1–SIA_F9 complexes. RMSD, RMSF, and hydrogen bonding analyses are used to understand the conformational flexibility and structural stability of each complex system. It has been concluded that the fluorinated sialic acid drug candidates SIA_F2 and SIA_F7 have better inhibiting potency against the N1 neuraminidase of H5N1 influenza virus.

Design of fluorinated sialic acid analog inhibitor to H5 hemagglutinin of H5N1 influenza virus through molecular dynamics simulation study

Influenza epidemics and pandemics are caused by influenza A virus. The cell surface protein of hemagglutinin and neuraminidase is responsible for viral infection and release of progeny virus on the host cell membrane. Now 18 hemagglutinin and 11 neuraminidase subtypes are identified. The avian influenza virus of H5N1 is an emergent threat to public health issues. To control the influenza viral infection it is necessary to develop antiviral inhibitors and vaccination. In the present investigation we carried out 50 ns Molecular Dynamics simulation on H5 hemagglutinin of Influenza A virus H5N1 complexed with fluorinated sialic acid by substituting fluorine atoms at any two hydroxyls of sialic acid by considering combinatorial combination. The binding affinity between the protein-ligand complex system is investigated by calculating pair interaction energy and MM-PBSA binding free energy. All the complex structures are stabilized by hydrogen bonding interactions between the H5 protein and the ligand fluorinated sialic acid. It is concluded from all the analyses that the fluorinated complexes enhance the inhibiting potency against H5 hemagglutinin and the order of inhibiting potency is SIA-F9 ≫ SIA-F2 ≈ SIA-F7 ≈ SIA-F2F4 ≈ SIA-F2F9 ≈ SIA-F7F9 > SIA-F7F8 ≈ SIA-F2F8 ≈ SIA-F8F9 > SIA-F4 ≈ SIA-F4F7 ≈ SIA-F4F8 ≈ SIA-F8 ≈ SIA-F2F7 ≈ SIA > SIA-F4F9. This study suggests that one can design the inhibitor by using the mono fluorinated models SIA-F9, SIA-F2 and SIA-F7 and difluorinated models SIA-F2F4, SIA-F2F9 and SIA-F7F9 to inhibit H5 of H5N1 to avoid Influenza A viral infection.Communicated by Ramaswamy H. Sarma.