COMPARING CONFORMATIONS AT LOW-TEMPERATURE AND AT HIGH-VISCOSITY - CONFORMATIONAL STUDY OF SOMATOSTATIN AND 2 OF ITS ANALOGS IN METHANOL AND IN ETHYLENE-GLYCOL

The influence of low temperature and high viscosity on the conformatio n of somatostatin and two of its analogues was investigated by H-1 NMR in solution. The conformation of native somatostatin, a cyclic octape ptide agonist DC13-116 and a linear octapeptide agonist were compared in ethylene glycol at 303 K and in methanol at low temperature. The fi rst goal of this study was to investigate if either low temperature or high viscosity is the more important for the reduction of the conform ational freedom. Secondly we wanted to compare the amount of informati on concerning the conformation present in both solvents. A larger amou nt of NOESY cross-peaks is observed in ethylene glycol at room tempera ture compared to methanol at low temperature. This indicates that the raising of the viscosity is a more important factor in reducing the fl exibility of peptides than the lowering of the temperature. (C) Munksg aard 1994.