RESUMO
The spatial structure of spin-labeled angiotensin in aqueous solution wa investigated with the combined use of NMR, fluorescence spectroscopy and energy calculation including Monte-Carlo techniques. The calculated mean values of molecular parameters were compared with the experimental ones. The calculated and experimental mean values were regarded as statistically indistinguishable when the corresponding mean values occurred within the 95% confidence limit. The experimental parameters were shown to be adequately described by calculated conformers only with the assumption of the existence of dynamic equilibrium of conformers in solution. The mean values of statistical weights and their limits providing the agreement between the calculated and experimental data were determined. Two geometrically different forms of backbone structure for C-terminal hexapeptide in aqueous solution were revealed using the discussed approach; the N-terminal part of the molecule appeared to be much more conformationally labile. The model of molecule spatial structure is consistent with available literature data upon angiotensin titration experiments, its complexing with heavy metal ions etc.
Assuntos
Angiotensinas , Fenômenos Químicos , Química , Ligantes , Espectroscopia de Ressonância Magnética , Metais , Conformação Proteica , Soluções , ÁguaRESUMO
A statistical ensemble of thyroliberin conformations has been generated using Monte-Carlo techniques. The averaged vicinal coupling constants for the peptide backbone and His side chain, percentage of prolyl cis-isomers and characteristics of possible intramolecular hydrogen bonds have been calculated. The obtained mean values are in good agreement with the experimental results. This fact indicates that the generated statistical ensemble is similar to the true one and evidences against the existence in solution of a single unique structure of thyroliberin.
