MATERIALS AND METHODS
DATA INTERPRETATION
FitDis! was used to globally fit thermal denaturation curves of the peptides shown in (cf. Appendix, Table A5). The procedure started with the finding of the baseline parameters (θF0, θU0, mF and mU) while ignoring data values in the transition part of the curves. For the baselines of the folded states (θF0, mF), data points from the initial overlapping parts of the transition curves were fitted. For the unfolding of isolated KGW and EGW no initial overlapping parts were found, due to their low KF. Therefore the slope mf was kept constant at 0 during all fits.
The baselines of the unfolded states (θU0, mU) were determined from melting curves of comparable peptides in less stable states (cf. Appendix, Table A5) and kept constant while fitting with different models. These were for the heteromeric complexes (EGW/KGW and WGK + YGrE) one of the binding partners (EGW or YGrE respectively) in the temperature range above 70°C. For CC-Tri-N13 θU and mU were determined from unfolding curves at low monomer concentrations (Supporting Table A5). After convergence, the found solution was tested for robustness. For every dataset several stochiometric models were tested until stable solutions and convergence was reached. For peptides that were expected to be homomerics the tested models were: υ1 = n = 2; 3; …8. For peptides that were expected to be heteromerics the tested models were: υ1 = υ2 = n / 2 for even n and υ1 = (n - 1) / 2; υ2 = υ1 + 1 for odd n, with n = 2; 3; …8. The resulting best fits for every model can be compared by their root mean square error (RMSE) as the number of fitting parameters is equal in all models.40,46
37
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