Search research articles

ABOUT JoVE

Overview Leadership Blog JoVE Help Center

AUTHORS

Publishing Process Editorial Board Scope & Policies Peer Review FAQ Submit

LIBRARIANS

Testimonials Subscriptions Access Resources Library Advisory Board FAQ

RESEARCH

JoVE Journal Methods Collections JoVE Encyclopedia of Experiments Archive

EDUCATION

JoVE Core JoVE Business JoVE Science Education JoVE Lab Manual Faculty Resource Center Faculty Site

Terms & Conditions of Use

Related Concept Videos

Polyprotic Acids

Polyprotic Acids

Acids are classified by the number of protons per molecule that they can give up in a reaction. Acids such as HCl, HNO3, and HCN that contain one ionizable hydrogen atom in each molecule are called monoprotic acids. Their reactions with water are:

Strong Acid and Base Solutions

Strong Acid and Base Solutions

A strong acid is a compound that dissociates completely in an aqueous solution and produces a concentration of hydronium ions equal to the initial concentration of acid. For example, 0.20 M hydrobromic acid will dissociate completely in water and produces 0.20 M of hydronium ions and 0.20 M of bromide ions.

Henderson-Hasselbalch Equation

Henderson-Hasselbalch Equation

The ionization-constant expression for a solution of a weak acid can be written as:

Titration of a Weak Base with a Strong Acid

Titration of a Weak Base with a Strong Acid

The titration curve of a weak base like ammonia with a strong acid like hydrochloric acid is the mirror image of the titration curve of a weak acid with a strong base.
Using the ICE table and substituting the Kb value, we calculate the initial pH of 50 mL of 0.1 M ammonia to be 11.11. Addition of 25 mL of 0.1 M hydrochloric acid to this solution of ammonia results in a buffer with an equal concentration of ammonia and ammonium ions. The pH of this buffer can be calculated by substituting these...

Weak Acid Solutions

Weak Acid Solutions

Few compounds act as strong acids. A far greater number of compounds behave as weak acids and only partially react with water, leaving a large majority of dissolved molecules in their original form and generating a relatively small amount of hydronium ions. Weak acids are commonly encountered in nature, being the substances partly responsible for the tangy taste of citrus fruits, the stinging sensation of insect bites, and the unpleasant smells associated with body odor. A familiar example of a...

Relative Strengths of Conjugate Acid-Base Pairs

Relative Strengths of Conjugate Acid-Base Pairs

Brønsted-Lowry acid-base chemistry is the transfer of protons; thus, logic suggests a relation between the relative strengths of conjugate acid-base pairs. The strength of an acid or base is quantified in its ionization constant, Ka or Kb, which represents the extent of the acid or base ionization reaction. For the conjugate acid-base pair HA / A−, the ionization equilibrium equations and ionization constant expressions are

You might also read

Related Articles

Articles linked to this work by shared authors, journal, and citation graph.

Sort by

Same author

Kinetic advantage of forming respiratory supercomplexes.

Biochimica et biophysica acta. Bioenergetics·2020

Same author

Dynamic and Electronic Polarization Corrections to the Dielectric Constant of Water.

The journal of physical chemistry. A·2018

Same author

Investigating the Many Roles of Internal Water in Cytochrome c Oxidase.

The journal of physical chemistry. B·2018

Same author

Monte Carlo Simulations of Glu-242 in Cytochrome c Oxidase.

The journal of physical chemistry. B·2016

Same author

Tunneling Time and the Breakdown of Born-Oppenheimer Approximation.

The journal of physical chemistry. B·2015

Same author

Docking and migration of carbon monoxide in nitrogenase: the case for gated pockets from infrared spectroscopy and molecular dynamics.

Biochemistry·2015

Search research articles

Related Experiment Video

Updated: May 27, 2026

Sedimentation Equilibrium of a Small Oligomer-forming Membrane Protein: Effect of Histidine Protonation on Pentameric Stability

Sedimentation Equilibrium of a Small Oligomer-forming Membrane Protein: Effect of Histidine Protonation on Pentameric Stability

Published on: April 2, 2015

Histidine in continuum electrostatics protonation state calculations.

Vernon Couch¹, Alexei Stuchebrukhov

¹Department of Chemistry, University of California, Davis, California 95616, USA.

|November 11, 2011

Summary

This study presents a modified continuum electrostatics method to accurately calculate protein pKa values. The new approach effectively separates histidine tautomers, improving predictions for protonation states.

More Related Videos

Determination of the Gas-phase Acidities of Oligopeptides

Determination of the Gas-phase Acidities of Oligopeptides

Published on: June 24, 2013

Vibrational Spectra of a N719-Chromophore/Titania Interface from Empirical-Potential Molecular-Dynamics Simulation, Solvated by a Room Temperature Ionic Liquid

Vibrational Spectra of a N719-Chromophore/Titania Interface from Empirical-Potential Molecular-Dynamics Simulation, Solvated by a Room Temperature Ionic Liquid

Published on: January 25, 2020

Related Experiment Videos

Last Updated: May 27, 2026

Sedimentation Equilibrium of a Small Oligomer-forming Membrane Protein: Effect of Histidine Protonation on Pentameric Stability

Sedimentation Equilibrium of a Small Oligomer-forming Membrane Protein: Effect of Histidine Protonation on Pentameric Stability

Published on: April 2, 2015

Determination of the Gas-phase Acidities of Oligopeptides

Determination of the Gas-phase Acidities of Oligopeptides

Published on: June 24, 2013

Vibrational Spectra of a N719-Chromophore/Titania Interface from Empirical-Potential Molecular-Dynamics Simulation, Solvated by a Room Temperature Ionic Liquid

Vibrational Spectra of a N719-Chromophore/Titania Interface from Empirical-Potential Molecular-Dynamics Simulation, Solvated by a Room Temperature Ionic Liquid

Published on: January 25, 2020

Area of Science:

Biophysical Chemistry
Computational Biology
Protein Biochemistry

Background:

Calculating protein pKa values is crucial for understanding protein function.
Standard continuum electrostatics methods struggle with histidine's complex protonation states.
Histidine's imidazole ring has coupled protonatable sites, complicating electrostatic calculations.

Purpose of the Study:

To develop a modified continuum electrostatics approach for accurate protein pKa calculations.
To enable the decoupling of histidine tautomers within a two-state model.
To incorporate all histidine protonation states into electrostatic calculations.

Main Methods:

Modification of the standard continuum electrostatics approach.
Introduction of a two-state model for histidine tautomers.
Application of a single approximation for interrelations between histidine charge states.

Main Results:

Successfully decoupled histidine tautomers within the two-state model.
Enabled natural separation of the two protonatable sites of the imidazole ring.
Allowed inclusion of all histidine protonation states in the calculation.

Conclusions:

The modified method provides a more accurate way to calculate protein pKa values.
This approach overcomes limitations of standard methods in handling histidine residues.
The findings facilitate better computational modeling of protein behavior and function.