Ana P. Guimarães

Design of New Chemotherapeutics Against the Deadly Anthrax Disease. Docking and Molecular Dynamics studies of Inhibitors Containing Pyrrolidine and Riboamidrazone Rings on Nucleoside Hydrolase from Bacillus anthracis

Abstract Anthrax is a disease caused by Bacillus anthracis, a dangerous biological warfare agent already used for both military and terrorist purposes. An important selective target for chemotherapy against this disease is nucleoside hydrolase (NH), an enzyme still not found in mammals. Having this in mind we have performed molecular docking studies, aiming to analyze the three-dimensional positioning of six known inhibitors of Trypanosoma vivax NH (TvNH) in the active site of B. anthracis NH (BaNH). We also analyzed the main interactions of these compounds with the active site residues of BaNH and the relevant factors to biological activity. These results, together with further molecular dynamics (MD) simulations, pointed out to the most promising compounds as lead for the design of potential inhibitors of BaNH. Most of the docking and MD results obtained corroborated to each other. Additionally, the docking results also suggested a good correlation with experimental data.

Development of new acetylcholinesterase reactivators: molecular modeling versus in vitro data.

In this work a theoretical methodology for evaluation of the association and kinetic reactivation constants of oximes using the Molegro and Spartan softwares was proposed and validated facing in vitro data previously reported in the literature. Results showed a very good agreement between the theoretical binding free energies of the reactivators and experimental data, suggesting that the proposed methodology could work well in the prediction of kinetic and thermodynamics parameters for oximes that might be helpful for the design and selection of new and more effective oximes.

Docking and molecular dynamics studies of peripheral site ligand–oximes as reactivators of sarin-inhibited human acetylcholinesterase

In the present work, we performed docking and molecular dynamics simulations studies on two groups of long-tailored oximes designed as peripheral site binders of acetylcholinesterase (AChE) and potential penetrators on the blood brain barrier. Our studies permitted to determine how the tails anchor in the peripheral site of sarin-inhibited human AChE, and which aminoacids are important to their stabilization. Also the energy values obtained in the docking studies corroborated quite well with the experimental results obtained before for these oximes.

Association of the anti-tuberculosis drug rifampicin with a PAMAM dendrimer

The association of the anti-tuberculosis drug rifampicin (RIF) with a 4th-generation poly(amidoamine) (G4-PAMAM) dendrimer was investigated by means of molecular dynamics simulations. The RIF load capacity was estimated to be around 20 RIF per G4-PAMAM at neutral pH. The complex formed by 20 RIF molecules and the dendrimer (RIF20-PAMAM) was subjected to 100 ns molecular dynamics (MD) simulations at two different pH conditions (neutral and acidic). The complex was found to be significantly more stable in the simulation at neutral pH compared to the simulation at low pH in which the RIF molecules were rapidly and almost simultaneously expelled to the solvent bulk. The high stability of the RIF-PAMAM complex under physiological pH and the rapid release of RIF molecules under acidic medium provide an interesting switch for drug targeting since the Mycobacterium resides within acidic domains of the macrophage. Altogether, these results suggest that, at least in terms of stability and pH-dependent release, PAMAM-like dendrimers may be considered suitable drug delivery systems for RIF and derivatives.

Analysis of Bacillus anthracis nucleoside hydrolase via in silico docking with inhibitors and molecular dynamics simulation

AbstractAs the enzyme nucleoside hydrolase (NH) is widely found in nature but has not yet been detected in mammals, it is considered an ideal target in the development of chemotherapy against parasitic diseases and bacterial infections like anthrax. Considering the risk that this biological warfare agent represents nowadays, the search for new drugs and new molecular targets in the development of chemotherapy against anthrax is imperative. On this basis, we performed docking studies of six known NH inhibitors at the active site of NH from Bacillus anthracis (BaNH). Subsequently, molecular dynamics (MD) simulations of these compounds inside BaNH were carried out in order to complement the docking studies and select the most promising compounds as leads for the design of potential BaNH inhibitors. Most of the docking and MD results obtained agreed well with each other and showed good correlation with experimental data. FigureInteractions of compound 6 in the active sites of TvNH and BaNH

Applications of docking and molecular dynamic studies on the search for new drugs against the biological warfare agents Bacillus anthracis and Yersinia pestis.

The fear of biological warfare agents (BWA) use by terrorists is the major concern of the security agencies and health authorities worldwide today. The non-existence of vaccines or drugs against most BWA and the possibility of genetic modified strains has turned the search for new drugs to a state of urgency. Fast in silico techniques are, therefore, perfect tools for this task once they can quickly provide structures of several new lead compounds for further experimental work. Here we try to present a mini-review on docking and molecular dynamics simulations studies applied to the drug design against the BWA Bacillus anthracis and Yersinia pestis.

Applications of molecular modeling in the design of new insect repellents targeting the odorant binding protein of Anopheles gambiae

Mosquitoes are responsible for conveying various diseases caused by viruses, parasites and helminthes. Considering the cost and complexity of the treatment of these diseases, the use of repellents for protection from the mosquito vectors becomes an interesting alternative. In the present work, docking and molecular dynamics (MD) studies were performed on potential ligands to the odorant binding protein of the mosquito Anopheles gambiae (AgOBP1), the main vector of malaria. The binding modes on AgOBP1 of molecules with known attractive activities and the main components of the oil of indian clove (Syzygium aromaticum) with potential repellent activities were compared to the known repellent N,N-diethyl-3-methylbenzamide (DEET). Results suggest the eugenyl acetate as a better repellent than DEET and also reveal the main features of the binding site of AgOBP1 important to the design of new and more efficient repellents.

Docking studies on the binding of quinoline derivatives and hematin to Plasmodium falciparum lactate dehydrogenase

Abstract The literature has reported that ferriprotoporphyrin IX (hematin) intoxicates the malarial parasite through competition with NADH for the active site of the enzyme lactate dehydrogenase (LDH). In order to avoid this, the parasite polymerizes hematin to hemozoin. The quinoline derivatives are believed to form complexes with dimeric hematin, avoiding the formation of hemozoin and still inhibiting LDH. In order to investigate this hypothesis we calculated the docking energies of NADH and some quinoline derivatives (in the free forms and in complex with dimeric hematin) in the active site of the Plasmodium falciparum LDH (PfLDH). Ours results showed better docking score values to the complexes when compared to the free compounds, pointing them as more efficient inhibitors of PfLDH. Further we performed Molecular Dynamics (MD) simulations studies on the best docking conformation of the complex chloroquine-dimeric hematin with PfLDH. Our in silico results corroborate experimental data suggesting a possible action route for the quinoline derivatives in the inhibition of PfLDH.

Virtual screening, docking, and dynamics of potential new inhibitors of dihydrofolate reductase from Yersinia pestis.

In the present work, we propose to design drugs that target the enzyme dihydrofolate redutase (DHFR) as a means of a novel drug therapy against plague. Potential inhibitors of DHFR from Yersinia pestis (YpDHFR) were selected by virtual screening and subjected to docking, molecular dynamics (MD) simulations, and Poisson–Boltzmann surface area method, in order to evaluate their interactions in the active sites of YpDHFR and human DHFR (HssDHFR). The results suggested selectivity for three compounds that were further used to propose the structures of six new potential selective inhibitors for YpDHFR.

Molecular modeling toward selective inhibitors of dihydrofolate reductase from the biological warfare agent Bacillus anthracis

In the present work, we applied docking and molecular dynamics techniques to study 11 compounds inside the enzymes dihydrofolate reductase (DHFR) from the biological warfare agent Bacillus anthracis (BaDHFR) and Homo sapiens sapiens (HssDHFR). Six of these compounds were selected for a study with the mutant BaF96IDHFR. Our results corroborated with experimental data and allowed the proposition of a new molecule with potential activity and better selectivity for BaDHFR.