Background and aim Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most common causes of surgical infection, and its resistance to numerous conventional antibiotics makes treatment difficult. Although vancomycin is often an effective agent for the initial therapy of MRSA, clinical failure sometimes occurs. Therefore, there is an urgent need to develop better therapies. Here, we prepared some vancomycin-loaded nanoliposomes coupled with anti-staphylococcal protein (lysostaphin) and evaluated their in vitro and in vivo efficacy as a topical MRSA therapy. Methods Vancomycin was encapsulated in liposomes, and the coupling of lysostaphin with the surface of liposomes was carried out through cyanuric functional groups. The bactericidal efficacies and a full characterization were evaluated. To define different nanoliposomal–bacterium interactions and their bactericidal effect, flow cytometry was employed. Finally, in vivo, the topical antibacterial activity of each formulation was measured against surgical wound MRSA infection in a mouse model. Results High encapsulation and conjugation efficiency were achieved for all formulations. All the formulations showed a significant reduction in bacterial counts ( p< 0.05). The targeted liposomes more effectively suppress bacterial infection in vitro and in vivo relative to equivalent doses of untargeted vancomycin liposome. The flow cytometry results confirmed liposome–bacterium interactions, which increased during the incubation time. The maximum binding rate and the bactericidal effect were significantly higher in targeted liposomes ( p< 0.05) compared with control liposomes. Conclusion Our data suggest a novel nano-vehicle (lysostaphin-conjugated coupled liposomal vancomycin) which could be used as a great topical antimicrobial construct for treatment of MRSA skin infections.

Tyrosinase is a tetrameric enzyme that plays an important role in pigment production. Overproduction of melanin, which may lead to several skin disorders, is a result of tyrosinase activity. Hence, tyrosinase inhibitors are of key importance in the treatment of these disorders. In the present study, four flavonoid inhibitors, namely chrysin, naringin, quercetin, and kaempferol, were evaluated physiochemically, and the inhibitory effects of these compounds on tyrosinase activity were evaluated using the molecular dynamics (MD) simulation method. To create the best conformation of the enzyme-substrate/inhibitor, the docking process for enzyme-substrate, i.e., enzymechrysin, enzyme-quercetin, enzyme-naringin, and enzyme-kaempferol, was performed. The complexes with the best binding energies were selected as the models for the MD simulation process. Furthermore, the structural (RMSD, Rg, RMSF, and Distance) and the thermodynamics properties of the complexes were evaluated. Additionally, the PMF was conducted to calculate the binding free energies. The results showed that chrysin, quercetin and the substrate were at similar distances to the amino acids of the active site, but naringin and kaempferol were closer to the active site of the enzyme than the substrate. Moreover, the analysis of the binding energy revealed that the substrates, chrysin, kaempferol, quercetin, and naringin bound to the enzyme with binding energies of !7.8, !3.1, !7.1, !3.9, and !8.4 kcal/mol, respectively, which confirms that naringin has the highest inhibitory effect on tyrosinase among other inhibitors, which makes it an appropriate candidate as a whitening agent in skin disorders.

The interaction between human serum albumin (HSA) and arachidonic acid (AA) as an unsaturated fatty acid were investigated in the present study using methods including UV-VIS spectrophotometry, fluorescence and circular dichroism (CD) spectroscopy, lifetime measurements, fluorescence anisotropy measurements and visual molecular dynamics (MD). The thermodynamic parameters were assessed from HSA thermal and chemical denaturation in the presence and absence of AA. From the thermal denaturation, the T m and ΔG˚(298K) magnitudes obtained were 327.7 K and 88 kJ/mol, respectively, for HSA alone, and 323.4 K and 85 kJ/mol, respectively, following treatment with a 10 µM AA concentration. The same manner of reduction in Gibbs free energy as a criterion of protein stability was achieved during chemical denaturation by urea in the presence of AA. The present study investigates HSA binding nature through MD approaches, and the results indicated that the binding affinity of AA to the subdomain IIA of HSA is greater compared with that of subdomain IIIA. Although the HSA regular secondary structure evaluation by CD exhibited a minor change following incubation with AA, its tertiary structure revealed an observable fluctuation. Thus, it appears that the interaction between AA and HSA requires minor instability and partial structural changes.

Calprotectin is a heterodimeric protein complex which consists of two subunits including S100A8 and S100A9. This protein has a major role in different inflammatory disease and various types of cancers. In current study we aimed to evaluate the structural and thermodynamic changes of the subunits and the complex in presence of sodium and calcium ions using molecular dynamics (MD) simulation. Therefore, the residue interaction network (RIN) was visualized in Cytoscape program. In next step, to measure the binding free energy, the potential of mean force (PMF) method was performed. Finally, the molecular mechanics Poisson-Boltzmann surface area (MMPBSA) method was applied as an effective tool to calculate the molecular model affinities. The MD simulation results of the subunits represented their structural changes in presence of Ca2+. Moreover, the RIN and Hydrogen bond analysis demonstrated that cluster interactions between Calprotectin subunits in presence of Ca2+ were greater in comparison with Na+. Our findings indicated that the binding free energy of the subunits in presence of Ca2+ was significantly greater than Na+. The results revealed that Ca2+ has the ability to induce structural changes in subunits in comparison with Na+ which lead to create stronger interactions between. Hence, studying the physical characteristics of the human proteins could be considered as a powerful tool in theranostics and drug design purposes.