Combined use of spectroscopic and energy calculation methods for the determination of peptide conformation in solution

This paper describes the combined use of energy calculations and spectroscopic data for the determination of peptide conformations in solution. The approach involves (i) experimental measurements of spectroscopic parameters for a molecule, (ii) calculation of these parameters for low-energy conformers previously determined with regard to local fluctuations in conformation and (iii) a random search for statistically weighted combinations of conformers which provide a good agreement between the calculated and experimental data. The above approach was used to study the conformation of a spin-labelled angiotensin molecule (SL-AT). It appears that the C-terminal hexapeptide of SL-AT possesses two geometrically different spatial forms of the backbone in aqueous solution, with mean values for the statistical weight of 0.78 and 0.22, respectively. In contrast, the N-terminal part of the molecule is conformationally labile. The data obtained can be used to describe the conformation of angiotensin in solution.