Peptides with the selected alanine, phenylalanine, glycine, or leucine having N labels in the backbone (positions shown in Fig. ) were purchased from Peptide Protein Research Ltd (United Kingdom) in a powder form with the purity above 95%. Approximately 0.3 mg of each peptide was weighed in an eppendorf vial using an analytical balance (Precisa, XT 120A). The powder was then dissolved with deuterated sodium dodecyl sulfate (SDS, Sigma Aldrich) to obtain a solution with 0.3 mM peptide in 30 mM SDS and 20 mM sodiumphosphate buffer. 5% D 2 O was added for the lock in the NMR spectrometer. The solvent was prepared dissolving approximately 4.2 mg of SDS with 337.5 µl of milli-Q water, 90 µl sodium-phosphate buffer (pH 7.4, 0.1 M) and 22.5 µl of D 2 O. The samples were transferred into 5 mm NMR tubes and all the NMR measurements were performed at 310 K using on Bruker Avance IIIHD 850 MHz spectrometer equipped with a cryogenically cooled probe head at the Institute of Biotechnology, University of Helsinki.