What is the primary use of tryptophan fluorescence in protein studies?

The primary use of tryptophan fluorescence in protein studies is to detect changes in protein conformation. Tryptophan is an aromatic amino acid that exhibits fluorescence properties when excited by light. The environment surrounding tryptophan residues in a protein can significantly influence their fluorescence characteristics.

When a protein undergoes conformational changes—such as folding, unfolding, or binding to other molecules—these changes can affect the microenvironment of tryptophan residues. For instance, a tryptophan residue might be buried deep within the hydrophobic core of a protein in its native state, leading to low fluorescence. Conversely, if the protein unfolds and the tryptophan is exposed to a more polar environment, the fluorescence intensity can increase.

By measuring the fluorescence intensity, lifetime, and wavelength shifts, researchers can gain insights into the structural dynamics of proteins, confirming conformational changes induced by factors like pH, temperature, ligands, or other proteins. This property makes tryptophan fluorescence a powerful tool in biochemistry for studying protein behavior and conformational states.

In contrast, identifying protein sequences typically relies on methods such as mass spectrometry or Edman degradation, measuring protein concentration is often performed using UV absorbance or specific