Abstract

A combined resin solvation-peptide chain motion and kinetics of coupling reaction approach was applied to monitor details of the synthesis of TM-34, a 34-residue transmembrane segment of the bradykinin receptor. The dynamics of resin-bound peptide fragments attached to a stable free radical amino acid were examined by EPR spectroscopy. In agreement with an abrupt decrease (from 83 to 43%) in peptide purity occurring in the 12−16 region when DMF was used, a much more strongly immobilized chain population was detected, especially at the 12-mer stage. Conversely, faster couplings and improved synthesis were observed in 20% DMSO/NMP, probably due to the higher chain mobility in this mixed solvent. In addition, findings relating to solvation of peptide resins seemed to corroborate the previously advanced proposition that the 1:1 sum of electron acceptor and electron donor properties of a solvent can be considered to be an alternative and more appropriate parameter for its polarity. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

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