Secondary and tertiary structural characterisation of the five FOXP constructs
(A) Secondary structural characterisation using far-UV circular dichroism. (B) Secondary structural content analysis of the circular dichroism spectra using DichroWeb [28]. The longer constructs have a higher proportion of helical structure but also more disorder. Statistical significance of the differences in proportion of secondary structural content was determined using an unpaired Student’s t-test (***P<0.001). (C) Normalised tryptophan fluorescence spectra (excitation wavelength 295 nm) of the five FOXP constructs. Maximum fluorescence intensity is observed at ∼330 nm for the longer, leucine-zipper-containing FOXP constructs and ∼336 nm for the forkhead domain variants.