| has gloss | eng: Phi value analysis is an experimental protein engineering method used to study the structure of the folding transition state in small protein domains that fold in a two-state manner. Since the folding transition state is by definition a transient and partially unstructured state, its structure is difficult to determine by traditional methods such as protein NMR or X-ray crystallography. In phi-value analysis, the folding kinetics and conformational folding stability of the wild-type protein are compared with those of one or more point mutants. This comparison yields a phi value (defined below) that seeks to measure the mutated residue's energetic contribution to the folding transition state (and thus the degree of native structure around the mutated residue in the transition state) from the relative free energies of the unfolded state, the folded state and the transition state for the wild-type and mutant proteins. |
