Effect of temperature on peptide chain aggregation: an EPR study of model peptidyl-resins

The effect of temperature on the dynamics of peptide chains inside resin beads was monitored by electron paramagnetic resonance (EPR) spectroscopy. A two-component spectra was obtained for low and highly peptide-loaded model peptidyl-resins labeled with the paramagnetic aminoacid 2,2,6,6-tetramethyl-piperidine-N-oxyl-4-amino-4-carboxylic acid (TOAC), indicating the presence of strongly and weakly immobilized populations. Increasing levels of chain disaggregation were observed with increasing temperature, leading in some cases to a complete disappearance of the more immobilized population. The present findings demonstrate that EPR spectral parameters are highly sensitive to the solvation properties of labeled sites inside the resin matrix and can be of great value for the understanding of polymer-supported processes or reactions.