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Desenvolvimento de um protocolo de simulação por dinâmica molecular para avaliação estrutural e energética de variantes da l-asparaginase humana

Wed, 01 Jan 2025 00:00:00 GMT

Título: Desenvolvimento de um protocolo de simulação por dinâmica molecular para avaliação estrutural e energética de variantes da l-asparaginase humana Autor(es): Silva, Juliana Meneses de Sena Abstract: L-asparaginase is an enzyme widely employed in the treatment of acute lymphoblastic leukemia (ALL) due to its ability to degrade L-asparagine (Asn), which is essential for the survival of leukemic cells. However, currently available formulations are derived from bacterial sources and are often associated with severe immune reactions. Although the human body possesses a homologous enzyme, hASNase1, its low catalytic activity precludes its direct clinical application. To overcome this limitation, mutations have been proposed to enhance its catalytic efficiency. This study aimed to develop a computational protocol, based on molecular dynamics (MD) simulations and structural analyses, to evaluate the structural and energetic effects of hASNase1 variants and to identify molecular features associated with increased catalytic activity. The systems were built based on the native structure of the enzyme and simulated under physiological conditions. Structural stability was assessed through root mean square deviation (RMSD), while interatomic interaction potentials (PII) and binding free energy calculations were used to analyze the interactions between hASNase1 variants and Asn. MM/PBSA calculations revealed increasing binding affinities in the order D87S < D84N < A186V < D87N, consistent with substrate residence times in the catalytic site. Experimentally, catalytic activity increases of 17× (D87S), 19× (D84N), 50× (A186V), and 52× (D87N) were observed compared to the wild-type enzyme, confirming the effectiveness of the DM + MM/PBSA protocol in identifying high-performance variants. In conclusion, the DM and MM/PBSA protocol elucidated the structural determinants underlying the experimentally observed activity gains in hASNase1 variants, identifying D87N and A186V as promising candidates for an optimized human L-asparaginase. Understanding the relationship between structure and catalytic activity in hASNase1 variants reinforces the use of in silico approaches in the rational development of safer and more effective biopharmaceuticals for the treatment of ALL. Tipo: Dissertação

Avaliação in vitro da atividade antimicrobiana e antibiofilme da quitosana de Ucides cordatus contra bacterias gram-negativas resistentes aos antimicrobianos

Wed, 01 Jan 2025 00:00:00 GMT

Título: Avaliação in vitro da atividade antimicrobiana e antibiofilme da quitosana de Ucides cordatus contra bacterias gram-negativas resistentes aos antimicrobianos Autor(es): Carvalho, Francisco Sérvulo de Oliveira Abstract: Chitosan, derived from the deacetylation of chitin, has gained prominence due to its broad potential for applications in biomedical fields and the development of technologies in the food industry, particularly because of its antimicrobial activity. Traditionally extracted from the exoskeleton of crustaceans, the growing demand for this biopolymer has driven the exploration of the crab Ucides cordatus, found in mangrove ecosystems along the Atlantic coast. Thus, the present study aimed to evaluate the antimicrobial and antibiofilm activities of Ucides cordatus chitosan extracts against antimicrobial-resistant Gram-negative bactéria and to formulate an appropriate coating composition for application on coalho cheese. Antibacterial activity was determined by assessing the minimum inhibitory concentration and minimum bactericidal concentration at concentrations ranging from 5 to 0.009 mg/mL. Antibiofilm activity was evaluated using inhibition and eradication assays, quantified by the crystal violet staining method. To determine the appropriate coating formulation for coalho cheese, the wettability technique was employed through contact angle measurements on the surface. Toxicity assessments were conducted using the extracts and coating solutions in cellular models. With a degree of deacetylation of 92%, Ucides cordatus chitosan demonstrated good antimicrobial properties, showing inhibition of Gram-negative strains at bactericidal concentrations of 0.625 mg/mL, as well as inhibition of biofilm formation by approximately 98% in Pseudomonas aeruginosa and 86% in Escherichia coli resistant strains isolated from coalho cheese. These concentrations were found to be non-toxic. Regarding coating potential, based on the wettability technique on coalho cheese surfaces, the composition containing 2.0% Ucides cordatus chitosan with 0.2% glycerol was identified as the most suitable for coating application. The results obtained were comparable to those of commercially available chitosan, thus highlighting the biotechnological potential of Ucides cordatus chitosan as an antimicrobial agent in the biomedical field and the food industry. Tipo: Dissertação

Aplicação da galactomanana de sementes de Adenanthera pavonina L. como substituta parcial do Ágar em meios para o cultivo in vitro de tecidos e órgãos vegetais

Fri, 01 Jan 2016 00:00:00 GMT

Título: Aplicação da galactomanana de sementes de Adenanthera pavonina L. como substituta parcial do Ágar em meios para o cultivo in vitro de tecidos e órgãos vegetais Autor(es): Feitosa, Vanessa de Abreu Abstract: Plant tissue culture, which has several commercial applications, is the set of methodologies that permit the cultivation of cells, tissues, organs or parts of plant organs (explant) in a nutritious medium. The semi-solid culture medium, beyond various nutrients to the plant, needs a gelling agent, being agar the most used of them, however it’s expensive. Systems formulated by mixtures of polysaccharides (blends) may result in gels of great interest. This study aimed to evaluate the technical and economic feasibility of the use of galactomannan (Gm) of Adenanthera pavonina L. seeds as agar partial substituent in in vitro culture media of plants, using soy-perennial (Glycine wightii) as model. The endosperm (crude gum) were isolated, freeze-dried and crushed for subsequent extraction of Gm's. To evaluate the gelling potential of Gm's, different treatments (T) using blends of Agar+Gm were tested (Control: 1% + 0%; T1: 0% + 1%, T2: 0.9% + 0.1% Q3: 0.7% + 0.3%; Q4: 0.5% + 0.5%; T5: 0.3% + 0.7%). The blends were analyzed according to some qualitative, rheological and diffusion parameter. The effect of the blends in the development of callus coming from micropopagation of hypocotyl and cotyledon explants of G. wightii on MS medium, as well as in vitro germination and seedling development of this species. The yield of crude gum from the seeds of A. pavonina was approximately 87%, and the yield of Gm extracted from the crude gum was 92%. In the qualitative analysis of the medium’s characteristics, T2, T3 and T4 have the best results, with good solidification, and good homogeneity and transparency similar to the control. The study of rheological parameters revealed that the best interactions, in terms of gel strength, occurred in the means T2, T3 and T4, which were similar to the control, demonstrating a synergistic effect due to the strong and efficient interaction between the agar and GM's. T3 and T4 mediums used in the diffusion assay showed that T4 had the highest diffusion, compared to T3 and control. Both cotlyledon and hypocotyl callus of G. wightii grown in the medium T3 showed a growth pattern similar to that of control. T4 medium was superior to T3 and Control, possibly influenced by the greater amount of Gm, which may have been used as a carbon source for the culture. The percentages of seed germination, growth rate and size of G. wightii seedlings in T3 and T4 media were significantly higher than control, indicating that the presence of Gm's in media can influence positively the germination. From an economic point of view, to be easily extracted from a plant widely distributed in the country and provide an excellent yield (~ 90%), the Gm of A. pavonina seeds may be a promising component in the partial replacement of the agar used in the tissue culture mediuns, providing a economy of 50% per kg of used agar. Tipo: Dissertação

Avaliação in silico das interações do transportador de serotonina com fármacos antidepressivos e ácido alfa-lipóico

Wed, 01 Jan 2025 00:00:00 GMT

Título: Avaliação in silico das interações do transportador de serotonina com fármacos antidepressivos e ácido alfa-lipóico Autor(es): Vieira, Karoline Lima Abstract: Depression is a highly prevalent mood disorder, affecting more than 300 million people worldwide and standing as the leading cause of global disability. Among pharmacological approaches, the serotonin transporter (SLC6A4), also known as SERT or 5-HTT, plays a central role by promoting the reuptake of serotonin released into the synaptic cleft, making it a prominent therapeutic target of most currently available antidepressants. Despite the effectiveness of these medications, clinical response is frequently limited due to delayed onset of action and the occurrence of partial or even null responses in many cases, highlighting the need for new therapeutic strategies. In this context, alpha-lipoic acid (LPA), recognized for its antioxidant and anti-inflammatory properties, has emerged as a modulator of systems involved in depression. The aim of this study was to investigate, using computational techniques, the interaction of LPA with SERT’s orthosteric site (S1), comparing its performance to classic ligands such as serotonin, paroxetine, and desvenlafaxine, with the intention of exploring possible alternative mechanisms of antidepressant action. To this end, a model of human SERT was built using homology modeling and ab initio modeling. The ligands had their structures optimized and underwent molecular docking studies to evaluate their binding modes at the transporter’s binding sites. Next, molecular dynamics simulations were performed to analyze the stability of the formed complexes, and binding free energies were calculated using the MM/PBSA method. The results showed that while paroxetine displayed higher affinity for SERT’s S1 site, LPA did not act as a direct competitive inhibitor at this location. The analyses indicate that the antidepressant effects observed for LPA may be related to indirect mechanisms, such as modulation of neuroinflammation and oxidative stress, reinforcing its potential as an adjuvant agent in integrated pharmacological strategies and in drug repurposing. Tipo: Dissertação