Histidine Buffer Calculator With Solution

Henderson-Hasselbalch Equation for Histidine:

\[ pH = pKa + \log\left(\frac{[His]}{[His^+]}\right) \]

Calculated pH:

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1. What is the Histidine Buffer System?

The histidine buffer system utilizes the imidazole group of histidine, which has a pKa around 6.0, making it particularly effective for buffering in the physiological pH range. This buffer is crucial in biological systems and laboratory applications.

2. How Does the Calculator Work?

The calculator uses the Henderson-Hasselbalch equation:

\[ pH = pKa + \log\left(\frac{[His]}{[His^+]}\right) \]

Where:

\( pH \) — Calculated pH of the buffer solution
\( pKa \) — Acid dissociation constant of histidine (typically 6.0)
\( [His] \) — Concentration of deprotonated histidine (M)
\( [His^+] \) — Concentration of protonated histidine (M)

Explanation: The equation relates the pH of a buffer solution to the pKa and the ratio of concentrations of the conjugate base and acid forms.

3. Importance of Histidine Buffer

Details: Histidine buffers are essential in biochemical research, protein purification, and maintaining physiological pH in biological systems. The imidazole group's pKa makes it ideal for buffering around neutral pH.

4. Using the Calculator

Tips: Enter the pKa value (default is 6.0), concentrations of both histidine forms in molar units. All concentration values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Why is histidine used as a buffer?
A: Histidine's pKa around 6.0 makes it ideal for buffering in the physiological pH range (6-8), which is crucial for many biological processes.

Q2: What is the typical pKa value for histidine?
A: The imidazole group of histidine has a pKa of approximately 6.0, though this can vary slightly depending on temperature and ionic strength.

Q3: Where is histidine buffer commonly used?
A: Commonly used in protein purification, chromatography, enzyme assays, and maintaining pH in cell culture and biochemical experiments.

Q4: What are the limitations of histidine buffer?
A: May complex with metal ions, and its buffering capacity decreases outside the pH range of pKa ± 1 unit.

Q5: How does temperature affect histidine buffering?
A: Temperature changes can slightly shift the pKa value, with pKa typically decreasing as temperature increases.