Avaliação da espécie vegetal Croton cajucara Benth como inibidor de biocorrosão em aço carbono Aisi 1020

Actually in the oil industry biotechnological approaches represent a challenge. In that, attention to metal structures affected by electrochemical corrosive processes, as well as by the interference of microorganisms (biocorrosion) which affect the kinetics of the environment / metal interface. Regarding to economical and environmental impacts reduction let to the use of natural products as an alternative to toxic synthetic inhibitors. This study aims the employment of green chemistry by evaluating the stem bark extracts (EHC, hydroalcoholic extract) and leaves (ECF, chloroform extract) of plant species Croton cajucara Benth as a corrosion inhibitor. In addition the effectiveness of corrosion inhibition of bioactive trans-clerodane dehydrocrotonin (DCTN) isolated from the stem bark of this Croton was also evaluated. For this purpose, carbon steel AISI 1020 was immersed in saline media (3,5 % NaCl) in the presence and absence of a microorganism recovered from a pipeline oil sample. Corrosion inhibition efficiency and its mechanisms were investigated by linear sweep voltammetry and electrochemical impedance. Culture-dependent and molecular biology techniques were used to characterize and identify bacterial species present in oil samples. The tested natural products EHC, ECF and DCTN (DMSO as solvent) in abiotic environment presented respectively, corrosion inhibition efficiencies of 57.6% (500 ppm), 86.1% (500 ppm) and 54.5% (62.5 ppm). Adsorption phenomena showed that EHC best fit Frumkin isotherm and ECF to Temkin isotherm. EHC extract (250 ppm) dissolved in a polar microemulsion system (MES-EHC) showed significant maximum inhibition efficiency (93.8%) fitting Langmuir isotherm. In the presence of the isolated Pseudomonas sp, EHC and ECF were able to form eco-compatible organic films with anti-corrosive properties

Modelagem molecular na caracterização eletrônica de oligopeptídeos e na descrição quântica da interação fármaco-receptor

In this dissertation, the theoretical principles governing the molecular modeling were applied for electronic characterization of oligopeptide α3 and its variants (5Q, 7Q)-α3, as well as in the quantum description of the interaction of the aminoglycoside hygromycin B and the 30S subunit of bacterial ribosome. In the first study, the linear and neutral dipeptides which make up the mentioned oligopeptides were modeled and then optimized for a structure of lower potential energy and appropriate dihedral angles. In this case, three subsequent geometric optimization processes, based on classical Newtonian theory, the semi-empirical and density functional theory (DFT), explore the energy landscape of each dipeptide during the search of ideal minimum energy structures. Finally, great conformers were described about its electrostatic potential, ionization energy (amino acids), and frontier molecular orbitals and hopping term. From the hopping terms described in this study, it was possible in subsequent studies to characterize the charge transport propertie of these peptides models. It envisioned a new biosensor technology capable of diagnosing amyloid diseases, related to an accumulation of misshapen proteins, based on the conductivity displayed by proteins of the patient. In a second step of this dissertation, a study carried out by quantum molecular modeling of the interaction energy of an antibiotic ribosomal aminoglicosídico on your receiver. It is known that the hygromycin B (hygB) is an aminoglycoside antibiotic that affects ribosomal translocation by direct interaction with the small subunit of the bacterial ribosome (30S), specifically with nucleotides in helix 44 of the 16S ribosomal RNA (16S rRNA). Due to strong electrostatic character of this connection, it was proposed an energetic investigation of the binding mechanism of this complex using different values of dielectric constants (ε = 0, 4, 10, 20 and 40), which have been widely used to study the electrostatic properties of biomolecules. For this, increasing radii centered on the hygB centroid were measured from the 30S-hygB crystal structure (1HNZ.pdb), and only the individual interaction energy of each enclosed nucleotide was determined for quantum calculations using molecular fractionation with conjugate caps (MFCC) strategy. It was noticed that the dielectric constants underestimated the energies of individual interactions, allowing the convergence state is achieved quickly. But only for ε = 40, the total binding energy of drug-receptor interaction is stabilized at r = 18A, which provided an appropriate binding pocket because it encompassed the main residues that interact more strongly with the hygB - C1403, C1404, G1405, A1493, G1494, U1495, U1498 and C1496. Thus, the dielectric constant ≈ 40 is ideal for the treatment of systems with many electrical charges. By comparing the individual binding energies of 16S rRNA nucleotides with the experimental tests that determine the minimum inhibitory concentration (MIC) of hygB, it is believed that those residues with high binding values generated bacterial resistance to the drug when mutated. With the same reasoning, since those with low interaction energy do not influence effectively the affinity of the hygB in its binding site, there is no loss of effectiveness if they were replaced.

Filogenia molecular de fungos gasteroides das ordens Phallales e Geastrales (Phallomycetidae)

Gasteroids fungi are characterized by the basidiospores maturation inside the basidioma, from which spores liberation occurs in a passive manner. These fungi were once seen as a well definite class of Basidiomycota, but nowadays they are considered an artificial assemblage, because the organisms have independent evolutionary histories forming a polyphyletic group with a vast morphological variety. Despite their diversity, studies with this group in the tropics are incipient, and the phylogenetic relationships of the species from temperate climate remain unknown. Thus, this work aimed to elucidate the phylogenetic relationships of gasteroids fungi from the Geastrales and Phallales orders, with the inclusion of tropical and temperate species, and with these analyses suggest a systematic position of species like Aseroë floriformis and Phallus roseus, as well as to verify if the lignicolous habit can indicate parental relationship in the Geastrum genus. For this, basidiomata were collected at Atlantic rain forest areas, during the rainy season, and the specimen identification followed specific literature for gasteroid fungi. The phylogenetic analyses were performed with Maximum Parsimony and Bayesian Analysis, making use of RPB2 and 28S nuclear genes and atp6 mitochondrial gene. It could be observed on the Phallales dendogram, that Aseroë floriformis did not cluster with A. rubra, and that it has an anterior divergence from all others species of the family Clathraceae used in this analysis, assuming a basal position in the clade. Phallus roseus, which once was recognized as Itajahya, has previous divergence from the group formed by Phallus species. At the Geastrales dendogram, in the group corresponding to Geastrum genus, it could be observed that species with lignicolous habitat clustered in a clade with high support values. So, the results suggest the creation of a new genus to accommodate A. floriformis, and the revalidation of Itajahya, as well as it can be affirmed that the lignicolous habitat on the Geastrum genus in fact indicates parental relationships, and that it has arised only once at the evolutionary history of the genus