Figure 4

Thermal and chemical stability of cis- and trans isomers. (a) Circular dichroism far-UV spectra reveal lower helical propensities in both the cis- and trans isomers. θ = ellipticity. (b) Differences in thermal unfolding are monitored by ellipticity at 222 nm and show both the cis- and trans isomers are considerably less stable than insulin. (c) Unfolding in the presence of guanidine demonstrates that both isomers are considerably destabilized compared to insulin. ΔG values derived from guanidine denaturation studies are listed.