Editing Circular dichroism (section)

=== Fluorescence ===
Fluorescence measurements in CD spectroscopy, recorded at a 90 degree angle to the incident light, often serve as a complementary data channel, providing additional insights into protein stability and conformational changes. By detecting intrinsic fluorescence from aromatic residues such as tryptophan and tyrosine, researchers can assess environmental shifts that accompany structural transitions. Fluorescence data can be acquired alongside CD signals, particularly in temperature ramp experiments, where it helps monitor unfolding events by tracking changes in emission intensity or wavelength shifts. This process could be followed by recording CD spectra at intervals of 1&nbsp;°C, for example, while increasing the temperature continuously at 1&nbsp;°C per minute. The excitation bandwidth required for the fluorescence spectra is usually larger than what would be used as spectral bandwidth for CD measurements, so sometimes the use of different spectral bandwidths for CD and fluorescence measurements is necessary. This dual approach enhances the interpretation of protein behavior under varying conditions, improving confidence in structural and stability assessments.

There are multiple approaches to collecting fluorescence data, including the use of a [[photomultiplier tube]] (PMT) to record total fluorescence, the use of a [[Charge-coupled device|CCD]] fluorometer to record full-spectrum fluorescence, or the use of a scanning emission monochromator (SEM) to allow for scanning the fluorescence spectrum at a fixed excitation wavelength.