Marta Campos - Academia.edu (original) (raw)
Papers by Marta Campos
Biochemistry, 1997
We studied the effects of Mg2+ and of ADP and other nucleoside diphosphates on the dephosphorylat... more We studied the effects of Mg2+ and of ADP and other nucleoside diphosphates on the dephosphorylation of the E1P form of the partially purified pig kidney Na+,K+-ATPase at 20-22 degrees C. We report for the first time the rate of the reversal of ATP phosphorylation. The experiments were done on enzyme subjected to controlled chymotrypsin digestion consisting of a homogenous population of a truncated catalytic subunit. Under this condition the whole cycle is E1 <-- (f1.ATP, b1) --> E1ATP <-- (f2, b2) --> E1P.ADP <-- (fd, bd.ADP) --> E1P-(f3) --> E1. The values of f1, b1, f2, and f3 were independently estimated in the absence of ADP; those of fd, bd, and b2 were obtained from the fit of ADP-dependent dephosphorylation data to the differential equation set. When f2 = 0 or b1 is very large, the model predicts that dephosphorylation by ADP gives a single exponential; in all other cases it predicts a biphasic dephosphorylation in a semilogarithmic plot. The fast phase is governed by b2.ADP and the slow one by b1. This was experimentally verified. Also, ADP stimulates E1P breakdown without release of Pi, thus leading to ATP synthesis. The data indicate that the true substrate for ATP synthesis is free ADP, while Mg2+ inhibits mainly by a reduction in the free [ADP]; in addition, E1P has a very low affinity for MgADP. The nucleotide structure is also very important; all ADP analogues tested were much less effective than ADP due to a reduced affinity for the E1P and a poor capacity to reverse phosphorylation.
Biochimica Et Biophysica Acta-biomembranes, 1992
The aim of the present work s~as to elucidate the role pla~ed by ATP and Mg 2+ ions in the early ... more The aim of the present work s~as to elucidate the role pla~ed by ATP and Mg 2+ ions in the early steps .ff the Na+,K +-ATPase cycle. The approach was to follow pre-steady-state phosphorylation kinetics in Na +-containing K+-frce solutions under variable ATP and MgCI 2 concentrations. The experiments were performed with a rapid mixing apparatus at 20 5: 2°C. The concentrations of free and complexes species of Mg 2+ and ATP were calculated on the basis of a dissociation constant of 0.091 + 0.004 raM, estimated with Arsenazo lll under identical conditions. A simplified scheme were ATP binds to the ENa enzyme, which ix phosphorylated to MgEPNa and consequently dcl~hosphurylated returning to the ENa form, was used. In the absence of ADP and phosphate four rate constants are relevant: k! and k_ t, the on and off rate constants for ATP binding; k2, the transphosphorylation rate constant and k 3, the constant that governs the depbosphorylation rate. The values obtained were: kt ffi 0.025 + 0.003 ttM-i ms-1 for both free ATP and ATPMg; k_ t = 0.038 + 0.004 ms-~ for free ATP and 0.009 + 0.002 ms-t for ATPMg; k 2 ffi 0.199 4-0.005 ms-1; k3 ffi 0.0019 4-0.0002 ms-i. The model that seems best to explain the data is one where (i) the role of true substrate can be played equally well by free ATP or ATPMg, and (ii) free Mg 2+, an essential activator acts by binding to a specific Mg 2+ site on the enzyme mn.~eculc.
Asignatura : Música Curso o nivel: 6° Básico Nombre de la Unidad 1:
Nombre de la Unidad 1: "El entorno sonoro"
Asignatura : Música Curso o nivel: 5° Básico Nombre de la Unidad 1:
Escuchar cualidades del sonido (altura, timbre, intensidad, duración) y elementos del lenguaje mu... more Escuchar cualidades del sonido (altura, timbre, intensidad, duración) y elementos del lenguaje musical (pulsos, acentos, patrones, reiteraciones contrastes, variaciones, dinámica, tempo, preguntas-respuestas, secciones A-AB-ABA), y representarlos de distintas formas. (OA 1) Expresar, mostrando grados crecientes de elaboración, sensaciones, emociones e ideas que les sugiere la música escuchada usando diversos, medios expresivos (verbal, corporal, musical, visual)(OA2) Escuchar música en forma abundante de diversos contextos y culturas poniendo énfasis en: Tradición escrita (docta) Tradición oral (folclor, música de pueblos originarios) Popular (jazz, rock, fusión etcétera) (OA3)* Cantar al unísono y a más voces y tocar instrumentos de percusión, melódicos (metalófono, flauta dulce u otros) y/o armónicos (guitarra, teclado, otros).
Objetivos de Aprendizaje / Aprendizajes esperados: Escuchar cualidades del sonido (altura, timbre... more Objetivos de Aprendizaje / Aprendizajes esperados: Escuchar cualidades del sonido (altura, timbre, intensidad, duración) y elementos del lenguaje musical (pulsos, acentos, patrones, reiteraciones, contrastes, preguntas-respuestas, secciones A-AB-ABA), y representarlos de distintas formas. (OA 1 Expresar, mostrando grados crecientes de elaboración, sensaciones, emociones e ideas que les sugiere la música escuchada usando diversos medios expresivos (verbal, corporal, musical, (OA2) Escuchar música en forma abundante de diversos contextos y culturas poniendo énfasis en:
Biochemistry, 1997
We studied the effects of Mg2+ and of ADP and other nucleoside diphosphates on the dephosphorylat... more We studied the effects of Mg2+ and of ADP and other nucleoside diphosphates on the dephosphorylation of the E1P form of the partially purified pig kidney Na+,K+-ATPase at 20-22 degrees C. We report for the first time the rate of the reversal of ATP phosphorylation. The experiments were done on enzyme subjected to controlled chymotrypsin digestion consisting of a homogenous population of a truncated catalytic subunit. Under this condition the whole cycle is E1 <-- (f1.ATP, b1) --> E1ATP <-- (f2, b2) --> E1P.ADP <-- (fd, bd.ADP) --> E1P-(f3) --> E1. The values of f1, b1, f2, and f3 were independently estimated in the absence of ADP; those of fd, bd, and b2 were obtained from the fit of ADP-dependent dephosphorylation data to the differential equation set. When f2 = 0 or b1 is very large, the model predicts that dephosphorylation by ADP gives a single exponential; in all other cases it predicts a biphasic dephosphorylation in a semilogarithmic plot. The fast phase is governed by b2.ADP and the slow one by b1. This was experimentally verified. Also, ADP stimulates E1P breakdown without release of Pi, thus leading to ATP synthesis. The data indicate that the true substrate for ATP synthesis is free ADP, while Mg2+ inhibits mainly by a reduction in the free [ADP]; in addition, E1P has a very low affinity for MgADP. The nucleotide structure is also very important; all ADP analogues tested were much less effective than ADP due to a reduced affinity for the E1P and a poor capacity to reverse phosphorylation.
Biochimica Et Biophysica Acta-biomembranes, 1992
The aim of the present work s~as to elucidate the role pla~ed by ATP and Mg 2+ ions in the early ... more The aim of the present work s~as to elucidate the role pla~ed by ATP and Mg 2+ ions in the early steps .ff the Na+,K +-ATPase cycle. The approach was to follow pre-steady-state phosphorylation kinetics in Na +-containing K+-frce solutions under variable ATP and MgCI 2 concentrations. The experiments were performed with a rapid mixing apparatus at 20 5: 2°C. The concentrations of free and complexes species of Mg 2+ and ATP were calculated on the basis of a dissociation constant of 0.091 + 0.004 raM, estimated with Arsenazo lll under identical conditions. A simplified scheme were ATP binds to the ENa enzyme, which ix phosphorylated to MgEPNa and consequently dcl~hosphurylated returning to the ENa form, was used. In the absence of ADP and phosphate four rate constants are relevant: k! and k_ t, the on and off rate constants for ATP binding; k2, the transphosphorylation rate constant and k 3, the constant that governs the depbosphorylation rate. The values obtained were: kt ffi 0.025 + 0.003 ttM-i ms-1 for both free ATP and ATPMg; k_ t = 0.038 + 0.004 ms-~ for free ATP and 0.009 + 0.002 ms-t for ATPMg; k 2 ffi 0.199 4-0.005 ms-1; k3 ffi 0.0019 4-0.0002 ms-i. The model that seems best to explain the data is one where (i) the role of true substrate can be played equally well by free ATP or ATPMg, and (ii) free Mg 2+, an essential activator acts by binding to a specific Mg 2+ site on the enzyme mn.~eculc.
Asignatura : Música Curso o nivel: 6° Básico Nombre de la Unidad 1:
Nombre de la Unidad 1: "El entorno sonoro"
Asignatura : Música Curso o nivel: 5° Básico Nombre de la Unidad 1:
Escuchar cualidades del sonido (altura, timbre, intensidad, duración) y elementos del lenguaje mu... more Escuchar cualidades del sonido (altura, timbre, intensidad, duración) y elementos del lenguaje musical (pulsos, acentos, patrones, reiteraciones contrastes, variaciones, dinámica, tempo, preguntas-respuestas, secciones A-AB-ABA), y representarlos de distintas formas. (OA 1) Expresar, mostrando grados crecientes de elaboración, sensaciones, emociones e ideas que les sugiere la música escuchada usando diversos, medios expresivos (verbal, corporal, musical, visual)(OA2) Escuchar música en forma abundante de diversos contextos y culturas poniendo énfasis en: Tradición escrita (docta) Tradición oral (folclor, música de pueblos originarios) Popular (jazz, rock, fusión etcétera) (OA3)* Cantar al unísono y a más voces y tocar instrumentos de percusión, melódicos (metalófono, flauta dulce u otros) y/o armónicos (guitarra, teclado, otros).
Objetivos de Aprendizaje / Aprendizajes esperados: Escuchar cualidades del sonido (altura, timbre... more Objetivos de Aprendizaje / Aprendizajes esperados: Escuchar cualidades del sonido (altura, timbre, intensidad, duración) y elementos del lenguaje musical (pulsos, acentos, patrones, reiteraciones, contrastes, preguntas-respuestas, secciones A-AB-ABA), y representarlos de distintas formas. (OA 1 Expresar, mostrando grados crecientes de elaboración, sensaciones, emociones e ideas que les sugiere la música escuchada usando diversos medios expresivos (verbal, corporal, musical, (OA2) Escuchar música en forma abundante de diversos contextos y culturas poniendo énfasis en: