Editing Protein folding (section)

===Circular dichroism===
{{Main|Circular dichroism}}

[[Circular dichroism]] is one of the most general and basic tools to study protein folding. Circular dichroism spectroscopy measures the absorption of [[circular polarization|circularly polarized light]]. In proteins, structures such as [[alpha helix|alpha helices]] and [[beta sheets]] are chiral, and thus absorb such light. The absorption of this light acts as a marker of the degree of foldedness of the protein ensemble. This technique has been used to measure [[equilibrium unfolding]] of the protein by measuring the change in this absorption as a function of denaturant concentration or [[temperature]]. A denaturant melt measures the [[Thermodynamic free energy|free energy]] of unfolding as well as the protein's m value, or denaturant dependence. A temperature melt measures the [[Denaturation midpoint|denaturation temperature]] (Tm) of the protein.<ref name="pmid=26607240" /> As for fluorescence spectroscopy, circular-dichroism spectroscopy can be combined with fast-mixing devices such as [[stopped flow]] to measure protein folding [[Chemical kinetics|kinetics]] and to generate [[chevron plot]]s.