Melissa S. Caetano

Construction and Assessment of Reaction Models of Class I EPSP Synthase: Molecular Docking and Density Functional Theoretical Calculations

Abstract The high frequency of contamination by herbicides suggests the need for more active and selective herbicides. Glyphosate is the active component of one of the top-selling herbicides, which is also a potent EPSP synthase inhibitor. That is a key enzyme in the shikimic acid pathway, which is found only in plants and some microorganisms. Thus, EPSP synthase is regarded as a prime target for herbicides. In this line, molecular modeling studies using molecular dynamics simulations and DFT techniques were performed to understand the interaction of glyphosate and its analogs with the wild type enzyme and Gly96Ala mutant EPSP synthase. In addition, we investigated the reaction mechanism of the natural substrate. Our findings indicate some key points to the design of new selective glyphosate derivates.

Homology modeling of wild-type, D516V, and H526L Mycobacterium tuberculosis RNA polymerase and their molecular docking study with inhibitors.

Abstract Rifamicyns (Rifs) are antibiotic widely used for the treatment of tuberculosis (TB); nevertheless, their efficacy has been limited by a high percentage of mutations, principally in the rpoB gene. In this work, the first three-dimensional molecular model of the hypothetical structures for the wild-type and D516V and H526L mutants of Mycobacterium tuberculosis (mtRNAP) were elucidated by a homology modeling method. In addition, the orientations and binding affinities of some Rifs with those new structures were investigated. Our findings could be helpful for the design of new more potent rifamycin analogs.

Reactivation steps by 2-PAM of tabun-inhibited human acetylcholinesterase: reducing the computational cost in hybrid QM/MM methods

The present work describes a simple integrated Quantum Mechanics/Molecular Mechanics method developed to study the reactivation steps by pralidoxime (2-PAM) of acetylcholinesterase (AChE) inhibited by the neurotoxic agent Tabun. The method was tested on an AChE model and showed to be able to corroborate most of the results obtained before, through a more complex and time-consuming methodology, proving to be suitable to this kind of mechanistic study at a lower computational cost.

Molecular modeling of Mycobacterium tuberculosis dUTpase: docking and catalytic mechanism studies.

Abstract Mycobacterium tuberculosis is a leading cause of infectious disease in the world today. This outlook is aggravated by a growing number of M. tuberculosis infections in individuals who are immunocompromised as a result of HIV infections. Thus, new and more potent anti-TB agents are necessary. Therefore, dUTpase was selected as a target enzyme to combat M. tuberculosis. In this work, molecular modeling methods involving docking and QM/MM calculations were carried out to investigate the binding orientation and predict binding affinities of some potential dUTpase inhibitors. Our results suggest that the best potential inhibitor investigated, among the compounds studied in this work, is the compound dUPNPP. Regarding the reaction mechanism, we concluded that the decisive stage for the reaction is the stage 1. Furthermore, it was also observed that the compounds with a −1 electrostatic charge presented lower activation energy in relation to the compounds with a −2 charge.

Molecular insight into the inhibition mechanism of plant and rat 4-hydroxyphenylpyruvate dioxygenase by molecular docking and DFT calculations

The 4-hydroxyphenylpyruvate dioxygenase (HPPD) is a relevant target protein for therapeutic and agrochemical research. It is an iron-dependent enzyme, and its inhibition has very different effects on plants and animals. In animals, the enzyme has an important role in the catabolism of tyrosine, and in the plant, it operates in the cascade of photosynthesis. Potent HPPD inhibitors have been described, and all contain the 1,3-diketone group in its shape. In this research, we carried out a study of the interaction modes of HPPD enzymes from plant and rat with selective and non-selective herbicides which already available with their structures to identify the molecule groups which are essential to their activity and those that are likely to changes, mediated by molecular computations. In this theoretical investigation, methods of molecular docking, reaction mechanism (QM/MM) and AIM calculations were employed, aiming the search for new more active and selective herbicides. Modifications were performed for DAS 645 and DAS 869 inhibitors. DAS 645 presented a good selectivity for the inhibition of the plant enzyme, and the modifications to the analogs design done increased its activity. For this compound, π–π* stacking interactions seem to be important, and this fact was proven by using AIM calculations. The other prototype compound, DAS 869, a potent inhibitor for both enzymes, had its increased activity in the plant and rat enzyme after added groups capable of performing π–π* stacking interactions.

Molecular modelling of Mycobacterium tuberculosis acetolactate synthase catalytic subunit and its molecular docking study with inhibitors

Mycobacterium tuberculosis is a leading cause of infectious disease in the world today. This outlook is aggravated by a growing number of M. tuberculosis infections in individuals who are immunocompromised as a result of HIV infections. Thus, new and more potent anti-TB agents are necessary. Therefore, acetolactate synthase (mtALS) was selected as a target enzyme to combat M. tuberculosis. In this work, the three-dimensional molecular model of the hypothetical structure for the ALS catalytic subunit of M. tuberculosis was elucidated by homology modelling. In addition, the orientations and binding affinities of sulfonylurea inhibitors with the new structure was investigated. Our findings could be helpful for the design of new, more potent mtAHAS inhibitors.

Asymmetric biocatalysis of the nerve agent VX by human serum paraoxonase 1: molecular docking and reaction mechanism calculations

Organophosphorus compounds have been employed in agricultural activity for a long time, causing serious public health problems. Due to their toxic properties, these compounds have also been used as chemical weapons. In view of this scenario, the catalytic degradation and the development of bioremediation processes of organophosphorus compounds have been of wide interest. Among several enzymes capable of degrading organophosphorus compounds, the human serum paraoxonase 1 has shown good potential for this purpose. To evaluate the interaction mode between the human serum paraoxonase 1 (wild-type and mutants) enzymes and the VX compound, one of the most toxic organophosphorus compounds known, molecular docking calculations were conducted. In addition, seeking to analyze the reaction pathway and the stereochemistry preference by human serum paraoxonase 1 and the Rp and Sp enantiomers of VX, quantum mechanical/molecular mechanics calculations were performed. Our theoretical findings put in evidence that the wild-type and mutant human serum paraoxonase 1 enzymes strongly interact with VX. Moreover, with the quantum mechanical/molecular mechanics study, we observed that the human serum paraoxonase 1 preferentially degrades one enantiomer in relation to the other. The current results indicate key points for designing new, more efficient mutant human serum paraoxonase 1 enzymes for VX degradation.

99Tc NMR as a promising technique for structural investigation of biomolecules: theoretical studies on the solvent and thermal effects of phenylbenzothiazole complex

The phenylbenzothiazole compounds show antitumor properties and are highly selective. In this paper, the 99Tc chemical shifts based on the (99mTc)(CO)3(NNO) complex conjugated to the antitumor agent 2‐(4′‐aminophenyl)benzothiazole are reported. Thermal and solvent effects were studied computationally by quantum‐chemical methods, using the density functional theory (DFT) (DFT level BPW91/aug‐cc‐pVTZ for the Tc and BPW91/IGLO‐II for the other atoms) to compute the NMR parameters for the complex. We have calculated the 99Tc NMR chemical shifts of the complex in gas phase and solution using different solvation models (polarizable continuum model and explicit solvation). To evaluate the thermal effect, molecular dynamics simulations were carried, using the atom‐centered density matrix propagation method at the DFT level (BP86/LanL2dz). The results highlight that the 99Tc NMR spectroscopy can be a promising technique for structural investigation of biomolecules, at the molecular level, in different environments. Copyright

Targeting inhibition of COX-2: a review of patents, 2002-2006.

The main COX inhibitors are the non-steroidal anti-inflammatory drugs (NSAIDs). NSAIDs exert anti-inflammatory and analgesic effects through the inhibition of prostaglandin synthesis by blocking COX activity. Currently two COX isoenzymes are known, COX-1 and COX-2. Prostaglandins influenced by COX-1 maintain the integrity of the gastric mucosa. On the other hand, prostaglandins influenced by COX-2 mediate the inflammatory process. The common anti-inflammatory drugs (like aspirin, ibuprofen, and naproxen) all act by blocking the action of both the COX-1 and COX-2 enzymes. The COX-2 inhibitors represent a new class of drugs that do not affect COX-1, but selectively block COX-2. This selective action provides the benefits of reducing inflammation without irritating the stomach. This review will focus on the most recent developments published in the field, paying particular attention to promising COX-2 inhibitors, their chemistry and biological evaluation, and to new chemical and pharmaceutical processes. Moreover, we will discuss recent patents of structural analogs of the COX-2 inhibitors celecoxib and valdecoxib, and novel potential pyridazine, triazole, indole, thione derivatives as a future target for the treatment of inflammation, pain and other diseases.

Bonding, Structure, and Stability of Clusters: Some Surprising Results from an Experimental and Theoretical Investigation in Gas Phase

Structure and stability of clusters in the ground state were analyzed at the theoretical and experimental levels. Our experimental and theoretical findings showed that the clusters in gas phase tend to form mainly planar rings of four members. The symmetry and the small dipole moment in these specific configurations suggested that their stability could be associated with an alignment of the water molecules, maximizing attractive electrostatic interactions caused by changes in the charge distribution of the clusters.