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This work presents the construction of a potentiometric system for simple monitoring of enzymatic activity of alpha-amylase using a commom multimeter together with its application em laboratory classes ( higher education or basic education). The results presented here points to 1) novelty and potential method for applying a quantitative teaching about enzymatic kinetics in Biochemistry classes, 2) practical classes with minimal resources and reagents found in local commerce, as well as 3) the facilitation of the concepts learning and data analysis in enzymatic kinetics. In the experiment, a coherent electrochemical system in relation to the enzymatic kinetics of alpha-amylase was accompanied by the disappearance of the color of the anodic cell as well as a reduction of the electrical signal registered by the instrument.

International authorities classify the ricin toxin, present in castor seeds, as a potential agent for use in bioterrorism. Therefore, the detection, identification, and characterization of ricin are considered the first actions for its risk assessment during a suspected exposure, parallel to the development of therapeutic and medical countermeasures. In this study, we report the kinetic analysis of electro-oxidation of adenine released from hsDNA by the catalytic action of ricin by square wave voltammetry. The results suggest that ricin-mediated adenine release exhibited an unusual kinetic profile, with a progress curve controlled by the accumulation of the product and the values of the kinetic constants of 46.6 µM for Km and 2000 min−1 for kcat, leading to a catalytic efficiency of 7.1 × 105 s−1 M−1.

International authorities classify ricin toxin present in castor seed as a potential agent for use in bioterrorism. Therefore, the detection, identification, and characterization of ricin in various sample matrices are considered necessary actions for risk assessment during a suspected exposure. This study reports a portable electrochemical assay for detecting active ricin based on the adenine electro-oxidation released from herring sperm DNA substrate by its catalytic action. Also, kinetic parameters were calculated, and the values were Km of 3.14 µM and Kcat 2107 min−1. A linear response was found in optimized experimental conditions for ricin concentrations ranging from 8 to 120 ng/mL, and with a detection limit of 5.14 ng/mL. This proposed detection strategy emphasizes the possibility of field detection of active ricin in food matrices and can be applied to other endonucleolytic activities.

Objective: To evaluate the pulp tissue of rat molars after pulpotomies with mineral trioxide aggregate (MTA), Biodentine TM (BDT) and calcium hydroxide (CH) mixed with sterile saline solution (24 hours, 72 hours, 7 days and 15 days), through correlating MPO activity with active neutrophils and MMP8 activity with tissue remodeling . Material and Methods: Thirty-eight Wistar rats were randomly distributed into groups (control, I (MTA gray), II (BDT), and III (CH)) and subdivided according to the study period of 24 hours, 72 hours, 7 days or 15 days after pulpotomy. MMP8 activity was assessed through fluorescence technique, and MPO activity was determined using the MPO assay. Results: A gradual decrease of MPO and MM8 activity occurred in the group MTA over the experimental periods (p

A α-amilase e uma enzima chave na producao das cervejas por ser responsavel pela clivagem do amido em acucares fermentaveis. Durante o processo de preparacao do mosto que ocorre de 40 a 80°C, essa enzima pode ser afetada por polifenois presentes na mistura. O objetivo foi avaliar a cinetica e o equilibrio da interacao de α-amilase com polifenois usualmente presentes em cerveja e nas faixas de temperatura empregadas no processo. Para tanto, polifenois comumente encontrados em cerveja (acido clorogenico, acido cafeico, acido ferulico e quercetina) foram incubados com α-amilase em 298, 313 e 323K, a atividade da enzima foi determinada por absorcao molecular pelo metodo de triiodina, e os resultados tratados pela equacao integrada de Michaelis-Menten. O equilibrio quimico da interacao foi abordado por titulacao espectrofluorimetrica em 293, 303, 313, 323 e 333 K. Os resultados apresentaram valores dos parâmetros cineticos de α-amilase a 323K de Km 1,37 ±0,19 mg.mL-¹ e Vmax 0,66 ±0,08 mg.mL-¹.min-¹, e um modelo de inibicao competitiva apresentando Ki entre 2,00x10-5 ±4,50x10-7 mol.L-¹ e 4,52x10-5 ±2,24x10-6 mol.L-¹. Foram encontrados valores de energia de ativacao da enzima para acido clorogenico > acido ferulico > acido cafeico > quercetina. O acido clorogenico foi o que apresentou maior estabilidade na formacao dos complexos, com menor valor de Ki, maior sensibilidade com a temperatura e maior inibicao na temperatura otima da enzima (323K), antagonicamente aos valores apresentados para a quercetina. Os resultados da interacao ligante-enzima revelaram valores de Kb crescente com a temperatura, sugerindo maior estabilidade na formacao do complexo proximo a 323 K, e coincidentes com os resultados de inibicao enzimatica. Os valores para ∆H e ∆S sugerem um mecanismo entropicamente dirigido da associacao. Estudo da relacao estrutura-atividade demonstrou uma correlacao positiva entre a atividade biologica (ligacao e catalise) da α-amilase com os descritores de natureza polar dos polifenois (numero total de doadores e aceptores de ligacoes de hidrogenio, polarizabilidade, TPSA, Pka). Ensaios de interacao da enzima com acido clorogenico em diferentes valores de pH e forca ionica apoiam os dados de estrutura-atividade, e sugerem a participacao do ion carboxilato do ligante na interacao com grupos basicos na vizinhanca do sitio catalitico da enzima.