RESUMEN
The nonspecific interaction between lead ions and bovine serum albumin (BSA) was studied by the calorimetric technique. According to thermodynamic parameters calculated from titration curves, it can be seen that the increase of intermolecular bond energies and decrease of disorder in the system were accompanied by a binding process. This kind of binding is the reaction "driven by enthalpy." Furthermore, the denatured BSA has more binding sites and more changes in enthalpy and entropy than the native BSA because the unfolded chain of denatured BSA could adapt itself to the binding reaction with lead ions more easily.
Asunto(s)
Iones/química , Plomo , Albúmina Sérica Bovina/metabolismo , Animales , Calorimetría , Bovinos , Plomo/química , Plomo/metabolismo , Unión Proteica , Conformación Proteica , Desnaturalización Proteica , Albúmina Sérica Bovina/química , TermodinámicaRESUMEN
The toxic effects of lead(II) have been studied in Escherichia coli cells. Using microcalorimetric analysis, it was shown that E. coli growth was inhibited in the presence of Pb2+ resulting from damage to the cell membrane and that Pb2+ takes part in the metabolism of cells. Treatment with lysozyme confirms damage to the cell's outer membrane. Similarities between the ionic radii and charge/radius ratio cause Pb(II) to replace Ca(II) at the binding sites of lipopolysacharides, leading to rupture of protecting areas on the cell's surface. Consequently, the protection and functionality of outer membrane is lost, thus becoming the basis for the biological effect of Pb2+ on E. coli.
Asunto(s)
Escherichia coli/efectos de los fármacos , Plomo/química , Plomo/toxicidad , Cationes Bivalentes/química , Escherichia coli/metabolismo , Escherichia coli/ultraestructura , Microscopía Electrónica de TransmisiónRESUMEN
In this work, a fundamental regulatory role of formate on thuringiensin production by resting cell of Bacillus thuringiensis YBT-032 was investigated. Nicotinamide adenine dinucleotide (NADH) production and formate dehydrogenase activity increased with formate addition from 0.5 to 2.0 g/L, respectively. However, with the formate addition of 1.5 g/L, the activities of pyruvate kinase and glucose 6-phosphate dehydrogenase reached a peak and increased by 316 and 150% relative to those of the control, respectively. In addition, intracellular production of pyruvate, aspartate, citrate and adenine were significantly enhanced by 75, 66, 32 and 78% as well. An improvement (90%) of thuringiensin production was also successfully obtained. Interestingly to point out, thuringiensin yield was closely correlative with adenine production, and the linear relationship was also observed. The results suggest that appropriate formate addition did act as a modulator and facilitate carbon flux in glycolysis and pentose phosphate pathway to synthesize adenine and thuringiensin via intracellular NADH availability.