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Titration of a Polyprotic Acid02:08

Titration of a Polyprotic Acid

A polyprotic acid contains more than one ionizable hydrogen and undergoes a stepwise ionization process. If the acid dissociation constants of the ionizable protons differ sufficiently from each other, then the titration curve for such polyprotic acid generates a distinct equivalence point for each of its ionizable hydrogens. Therefore, titration of a diprotic acid results in the formation of two equivalence points, whereas the titration of a triprotic acid results in the formation of three...
Acid-Base Titration Curves02:23

Acid-Base Titration Curves

A titration curve is a plot of some solution property versus the amount of added titrant. For acid-base titrations, solution pH is a useful property to monitor because it varies predictably with the solution composition and, therefore, may be used to monitor the titration’s progress and detect its endpoint. Acid-base titration can be performed with a strong acid and a strong base, a strong acid and a weak base, or a strong base and a weak acid.
For a titration carried out for 25.00 mL of 0.100...
Solution Composition During Acid/Base Titrations01:17

Solution Composition During Acid/Base Titrations

The titration of a weak acid with a strong base results in the formation of water and the conjugate base of the acid. For instance, titrating acetic acid with sodium hydroxide leads to the formation of water and sodium acetate. A solution of acetic acid and sodium acetate constitutes a buffer whose relative concentration at different stages of the titration is indicated by the α values, which represent percentages of the weak acid and its conjugate base.
The α0 and α1 values represent the...
Titration of Polyprotic Base with a Strong Acid01:18

Titration of Polyprotic Base with a Strong Acid

The titration of a polyprotic base such as sodium carbonate with a strong acid such as hydrochloric acid results in two equivalence points on the titration curve. At the first equivalence point, the carbonate ions in the base are completely converted to bicarbonate ions. The second equivalence point corresponds to the complete conversion of bicarbonate ions to carbonic acid, which dissociates into carbon dioxide and water. The region before the first equivalence point corresponds to the...
Titration of a Weak Acid with a Strong Base01:30

Titration of a Weak Acid with a Strong Base

In titrating a weak acid with a strong base, different calculation methods are applied at various stages. Initially, the pH of a weak acid like acetic acid is calculated using its dissociation constant (Ka) and an ICE table. Upon addition of a strong base such as sodium hydroxide, a buffer forms, and its pH is determined using the Henderson-Hasselbalch equation. As more base is added and the titration reaches the halfway point, the pH becomes equal to the pKa of the acid, indicating equal...
Titration of Polyprotic Acids with a Strong Base01:23

Titration of Polyprotic Acids with a Strong Base

Titration of a polyprotic acid, which contains multiple ionizable protons, involves distinct dissociation steps, each with its own dissociation constant (Ka). Each successive Ka is weaker than the previous one. In the titration of a polyprotic acid like sulfurous acid with a strong base such as sodium hydroxide, the base first neutralizes the initial ionizable proton, forming an intermediate species (e.g., hydrogen sulfite ions). This step's titration curve resembles that of a weak monoprotic...

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Video Experimental Relacionado

Updated: Jul 5, 2026

Development of Sulfidogenic Sludge from Marine Sediments and Trichloroethylene Reduction in an Upflow Anaerobic Sludge Blanket Reactor
15:19

Development of Sulfidogenic Sludge from Marine Sediments and Trichloroethylene Reduction in an Upflow Anaerobic Sludge Blanket Reactor

Published on: October 15, 2015

La fosforilación multisite y la cuenta regresiva para la fase S.

R J Deshaies1, J E Ferrell

  • 1Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA. deshaies@its.caltech.edu

Cell
|January 10, 2002
PubMed
Resumen
Este resumen es generado por máquina.

La ubiquitina ligasa SCF ((Cdc4) se dirige específicamente a Sic1 con seis fosfatos, no con cinco. Este hallazgo revela un mecanismo de conteo molecular, que convierte señales analógicas en salidas digitales para los nanoprocesadores de proteínas.

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Quantification of Site-specific Protein Lysine Acetylation and Succinylation Stoichiometry Using Data-independent Acquisition Mass Spectrometry
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Development of Sulfidogenic Sludge from Marine Sediments and Trichloroethylene Reduction in an Upflow Anaerobic Sludge Blanket Reactor
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Simultaneous Multi-surface Anodizations and Stair-like Reverse Biases Detachment of Anodic Aluminum Oxides in Sulfuric and Oxalic Acid Electrolyte
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12:49

Quantification of Site-specific Protein Lysine Acetylation and Succinylation Stoichiometry Using Data-independent Acquisition Mass Spectrometry

Published on: April 4, 2018

Área de la Ciencia:

  • Biología Molecular Biología Molecular
  • La bioquímica es la bioquímica.
  • Regulación de las comunicaciones celulares.

Sus antecedentes:

  • Sic1 es un inhibidor del ciclo celular regulado por la fosforilación.
  • SCF ((Cdc4) es una ligasa de ubiquitina E3 involucrada en la progresión del ciclo celular.
  • Los niveles de fosforilación a menudo dictan la función y la degradación de las proteínas.

Objetivo del estudio:

  • Para investigar el umbral de fosforilación preciso reconocido por SCF ((Cdc4) para la ubiquitinación de Sic1.
  • Aclarar el mecanismo por el cual SCF ((Cdc4) distingue entre diferentes estados de fosforilación de Sic1.
  • Comprender cómo las señales de fosforilación analógica se convierten en salidas digitales en un contexto biológico.

Principales métodos:

  • Ensayos de unión in vitro utilizando variantes purificadas de SCF ((Cdc4) y Sic1 con estados de fosforilación definidos.
  • Los ensayos de ubiquitinación monitorean la modificación de Sic1 por el SCF (Cdc4).
  • Espectrometría de masas para confirmar los sitios de fosforilación y estequiometría en Sic1.

Principales resultados:

  • SCF ((Cdc4) se une selectivamente y ubiquitinates Sic1 fosforilado en seis sitios, pero no en cinco.
  • Esta ubiquitinación dependiente de la fosforilación desencadena la degradación de Sic1.
  • El estudio demuestra un claro interruptor "digital" basado en una entrada "analógica" (número de fosfatos).

Conclusiones:

  • SCF ((Cdc4) actúa como un contador molecular, utilizando un umbral de fosforilación preciso para el reconocimiento del sustrato.
  • Este mecanismo proporciona una salida digital (ubiquitinación / degradación) de una entrada analógica (varios niveles de fosforilación).
  • Comprender esta arquitectura de nanoprocesador de proteínas ofrece información sobre la regulación celular precisa y la transducción de señales.