Biological buffers are a class of chemical substances that can maintain a relatively stable pH in biochemical experiments or biological systems. They reduce dramatic fluctuations in environmental pH by neutralizing the added acid or base, thus providing a stable reaction environment for biomolecules (such as enzymes, proteins, DNA, etc.) or cells.

Central role

Maintaining pH stability: In biochemical reactions, cell cultures, molecular experiments, etc., the activity of many biomolecules is highly dependent on a specific pH range. The buffer can resist external acid-base interference and keep the pH of the system within the required range.

Protection of biomolecules: Avoid damage caused by pH fluctuations such as protein denaturation, DNA degradation or enzyme inactivation.

Working principle

Biobuffers usually consist of weak acids and their conjugate bases (or weak bases and their conjugate acids), which counteract the applied H + or OH + ⁻ by dynamic equilibrium. For example:

Tris buffer: Tris-HCl buffer pair formed by Tris (weak base) and hydrochloric acid (HCl).

Phosphate buffer (PBS) : NaH₂PO₄ (weak acid) Combination of Na₂HPO₄ (conjugate base).

Key application areas

Cell culture: Maintain the pH of the medium (e.g., HEPES, CO₂/ bicarbonate systems).

Enzyme experiments: Ensure optimal pH for enzyme activity (e.g. Tris for alkaline phosphatase).

Molecular biology: DNA/RNA extraction, PCR, electrophoresis (e.g. TAE/TBE buffers).

Protein purification: Protein stability is maintained during chromatography.

Precautions for choosing a buffer

pH range: The effective range of the buffer should cover the pH required for the experiment.

Ionic strength: High ionic strength may interfere with some reactions (e.g. electrophoresis requires low ionic buffers).

Compatibility: Avoid reactions with experimental components (such as phosphate and calcium ion precipitation in PBS).

Temperature effect: The pH of buffers such as Tris varies significantly with temperature.

Cytotoxicity: Low toxicity buffers (such as HEPES) should be selected in cell experiments.