Development, Evaluation, and Molecular Dynamics Study of Ampicillin-Loaded Chitosan-Hyaluronic Acid Films as a Drug Delivery System.

Periodontitis is an inflammatory periodontal disease defined by the progressive loss of tissues surrounding the tooth. Ampicillin is an antibiotic for managing and treating specific bacterial infections, including periodontitis. Periodontal pockets occur due to periodontal disease progression and act as a natural reservoir that is easily reachable for the insertion of a delivery system, and the amount of drug to be released has a major role in the efficiency of treatment of the disease. Polyelectrolyte complexes (PECs), particularly those based on chitosan and hyaluronic acid combinations, offer a promising avenue to overcome the challenges associated with drug delivery. These complexes are both biodegradable and biocompatible, making them an optimal choice for enabling targeted drug delivery. This study centers on developing and assessing the structure and dynamic attributes of a drug-PEC system encompassing ampicillin and chitosan-hyaluronic acid components, which represents a targeted drug delivery system to better alleviate the periodontitis. To achieve this goal, we conducted experiments including weight and drug content uniformity, swelling index, drug release %, FT-IR and SEM analyses, and atomistic molecular dynamics simulations on the drug PECs loaded with ampicillin with varying amounts of hyaluronic acid. All simulations and the experimental analysis suggested that increased HA amount resulted in an increase in drug release % and swelling index. The simulation outcomes provide insights into the nature of the drug and PEC interactions alongside transport properties such as drug diffusion coefficients. These coefficients offer valuable insights into the molecular behavior of ampicillin-PEC drug delivery systems, particularly in the context of their application in periodontitis treatment.

Structural dynamics and anti-biofilm screening of novel imidazole derivative to explore their anti-biofilm inhibition mechanism against Pseudomonas Aeruginosa.

The biofilm formation is still prevalent mechanism of developing the drug resistance in the Pseudomonas aeruginosa, gram-negative bacteria, known for its major role in nosocomial, ventilator-associated pneumonia (VAP), lung infections and catheter-associated urinary tract infections. As best of our knowledge, current study first time reports the most potent inhibitors of LasR, a transcriptional activator of biofilm and virulence regulating genes in, Pseudomonas aeruginosa LasR, utilizing newly functionalized imidazoles (5a-d), synthesized via 1,3-dipolar cycloaddition using click approach. The synthesized ligands were characterized through Mass Spectrometry and 1H NMR. The binding potency and mode of biding of ligands. Quantum Mechanical(QM) methods were utilized to investigate the electronic basis, HOMO/LUMO and dipole moment of the geometry of the ligands for their binding potency. Dynamics cross correlation matrix (DCCMs) and protein surface analysis were further utilized to explore the structural dynamics of the protein. Free energy of binding of ligands and protein were further estimated using Molecular Mechanical Energies with the Poisson-Boltzmann surface area (MMPBSA) method. Molecular Docking studies revealed significant negative binding energies (5a - 10.33, 5b -10.09, 5c - 10.11, and 5d -8.33 KJ/mol). HOMO/LUMO and potential energy surface map estimation showed the ligands(5a) with lower energy gaps and larger dipole moments had relatively larger binding potency. The significant change in the structural dynamics of LasR protein due to complex formation with newlyfunctionalized imidazoles ligands. Hydrogen bond surface analysis followed by MMPBSA calculations of free energy of binding further complemented the Molecular docking revelations showing the specifically ligand (5a) having the relatively higher energy of binding(-65.22kj/mol).Communicated by Ramaswamy H. Sarma.

Repurposing Amphotericin B: anti-microbial, molecular docking and molecular dynamics simulation studies suggest inhibition potential of Amphotericin B against MRSA.

Amphotericin B (AMPH) is an anti-fungal drug and this study, for the first time as best of our knowledge, reports the repurposing of the Amphotericin B. The drug was found to show significant antibacterial potential revealed by antimicrobial screening, molecular docking, and mode of action analysis targeting Penicillin Binding Protein 2a (PBP 2a protein) which is target of ß-lactam drugs and is involved in cell wall synthesis. Mode of action analysis showed the drug to have hydrophobic and hydrophilic interactions with both C-terminal, trans-peptidase and non-penicillin binding domain of the protein. Additionally, to evaluate the impact of ligand binding on the protein's conformational dynamics, molecular dynamics (MD) simulations were used. Comparative Dynamical flexibility (RMSF) and Dynamics Cross Correlation (DCCM) followed by MD simulations revealed the complex formation significantly effecting structural dynamics of the enzyme significantly in the non-penicillin binding domain (327-668) and slightly in trans peptidase domain. Radius of gyration assessment further showed ligand binding also decreasing over all compactness of protein. Secondary structure analysis indicated the complex formation changing the conformational integrity in non-penicillin binding domain. Hydrogen bond analysis and MMPBSA, free energy of calculations followed by MD simulations, also complemented the antimicrobial and molecular docking revelations suggesting Amphotericin B to have substantial antibacterial potential.

Molecular Characterization, Purification, and Mode of Action of Enterocin KAE01 from Lactic Acid Bacteria and Its In Silico Analysis against MDR/ESBL Pseudomonas aeruginosa.

Bacteriocins are gaining immense importance in therapeutics since they show significant antibacterial potential. This study reports the bacteriocin KAE01 from Enterococcus faecium, along with its characterization, molecular modeling, and antibacterial potency, by targeting the matrix protein of Pseudomonas aeruginosa. The bacteriocin was purified by using ammonium sulfate precipitation and fast protein liquid chromatography (FPLC), and its molecular weight was estimated as 55 kDa by means of SDS-PAGE. The bacteriocin was found to show stability in a wide range of pH values (2.0-10.0) and temperatures (100 °C for 1 h and 121 °C for 15 min). Antimicrobial screening of the purified peptide against different strains of P. aeruginosa showed its significant antibacterial potential. Scanning electron microscopy of bacteriocin-induced bacterial cultures revealed significant changes in the cellular morphology of the pathogens. In silico molecular modeling of KAE01, followed by molecular docking of the matrix protein (qSA) of P. aeruginosa and KAE01, supported the antibacterial potency and SEM findings of this study.

Inter-Subunit Dynamics Controls Tunnel Formation During the Oxygenation Process in Hemocyanin Hexamers.

Hemocyanin from horseshoe crab in its active form is a homo-hexameric protein. It exists in open and closed conformations when transitioning between deoxygenated and oxygenated states. Here, we present a detailed dynamic atomistic investigation of the oxygenated and deoxygenated states of the hexameric hemocyanin using explicit solvent molecular dynamics simulations. We focus on the variation in solvent cavities and the formation of tunnels in the two conformational states. By employing principal component analysis and CVAE-based deep learning, we are able to differentiate between the dynamics of the deoxy- and oxygenated states of hemocyanin. Finally, our results identify the deoxygenated open conformation, which adopts a stable, closed conformation after the oxygenation process.

Dynamic Profiling of ß-Coronavirus 3CL Mpro Protease Ligand-Binding Sites.

ß-coronavirus (CoVs) alone has been responsible for three major global outbreaks in the 21st century. The current crisis has led to an urgent requirement to develop therapeutics. Even though a number of vaccines are available, alternative strategies targeting essential viral components are required as a backup against the emergence of lethal viral variants. One such target is the main protease (Mpro) that plays an indispensable role in viral replication. The availability of over 270 Mpro X-ray structures in complex with inhibitors provides unique insights into ligand-protein interactions. Herein, we provide a comprehensive comparison of all nonredundant ligand-binding sites available for SARS-CoV2, SARS-CoV, and MERS-CoV Mpro. Extensive adaptive sampling has been used to investigate structural conservation of ligand-binding sites using Markov state models (MSMs) and compare conformational dynamics employing convolutional variational auto-encoder-based deep learning. Our results indicate that not all ligand-binding sites are dynamically conserved despite high sequence and structural conservation across ß-CoV homologs. This highlights the complexity in targeting all three Mpro enzymes with a single pan inhibitor.

Exploring interfacial dynamics in homodimeric S-ribosylhomocysteine lyase (LuxS) from Vibrio cholerae through molecular dynamics simulations.

To the best of our knowledge, this is the first molecular dynamics simulation study on the dimeric form of the LuxS enzyme from Vibrio cholerae to evaluate its structural and dynamical properties including the dynamics of the interface formed by the two monomeric chains of the enzyme. The dynamics of the interfacial region were investigated in terms of inter-residual contacts and the associated interface area of the enzyme in its ligand-free and ligand-bound states which produced characteristics contrast in the interfacial dynamics. Moreover, the binding patterns of the two inhibitors (RHC and KRI) to the enzyme forming two different enzyme-ligand complexes were analyzed which pointed towards a varying inhibition potential of the inhibitors as also revealed by the free energies of ligand binding. It is shown that KRI is a more potent inhibitor than RHC - a substrate analogue, showing correlation with experimental data. Moreover, the role of a loop in chain B of the enzyme was found to facilitate the binding of RHC similar to that of the substrate, while KRI demonstrates a differing binding pattern. The computation of the free energy of binding for the two ligands was also carried out via thermodynamic integration which ultimately served to correlate the dynamical properties with the inhibition potential of two different ligands against the enzyme. Furthermore, this successful study provides a rational to suggest novel LuxS inhibitors which could become promising candidates to treat the diseases caused by a broad variety of bacterial species.

Solvation of cholesterol in different solvents: a molecular dynamics simulation study.

To the best of our knowledge, molecular dynamics simulations of an isolated cholesterol immersed in four different solvents of varying polarity, such as water, methanol, dimethyl sulfoxide and benzene, were reported for the first time to gain insights into the structural and dynamical properties. The study was mainly focused on the evaluation of solvation of cholesterol with respect to its hydrophilic and hydrophobic structural components in the form of respective functional groups interacting with the solvents. Structural evaluations suggested that both hydrophilic and hydrophobic groups of cholesterol were interacting with the solvents, in particular methanol and dimethyl sulfoxide, which presented both types of interactions that are polar and non-polar. On the other hand, the highly polar water and non-polar benzene demonstrated extreme solvation behavior, since water was involved only in hydrogen bonding to the solute hydroxyl group and non-polar benzene formed strong van der Waals interactions only. Furthermore, the hydrophobic effect of cholesterol was also analyzed mainly in polar solvents, as the effect was more pronounced in the polar environment thereby preventing the solvent mobility in the solvation layer(s). The dynamical properties in terms of lateral diffusion and hydrogen bond dynamics as well as free energies of solvation also corroborated the findings based on the structural data and the hydrophobic character of cholesterol was later quantified by the computation of the averaged solvent accessible surface area. The polarity effect of the solvents on the aggregation property of cholesterol was further investigated, which is of big concern from the clinical point of view due to its major role in cardiovascular ailments. It was another major finding of the present study that aggregation was shown to be facilitated by highly polar solvents like water.

Hydration facilitates oxygenation of hemocyanin: perspectives from molecular dynamics simulations.

Molecular dynamics simulations were applied to deoxy- and oxy-hemocyanins using newly developed force field parameters for the dicopper site to evaluate their structural and dynamical properties. Data obtained from the simulations provided information of the oxygenation effect on the active site and overall topology of the protein that was analyzed by root-mean-square deviations, b-factors, and dicopper coordination geometries. Domain I of the protein was found to demonstrate higher flexibility with respect to domain II because of the interfacial rotation between domain I and II that was further endorsed by computing correlative domain movements for both forms of the protein. The oxygenation effect on the overall structure of the protein or polypeptide subunit was further explored via gyration radii evaluated for the metal-binding domain and for the whole subunit. The evaluation of hydration dynamics was carried out to understand the water mediated role of amino acid residues of the solvent tunnel facilitating the entry of oxygen molecule to the dicopper site of hemocyanin.