The spectral criterion of a left-handed helix of the poly-L-proline II type was elaborated during the study of a number of synthesized oligopeptides (in a solid state and solution): (Gly-Pro-Pro)1-8, (Gly-Pro)1, (Gly-Pro-Ala)1-4, (Gly-Pro-Gly)1-4, (Gly-Pro-Pro) X (Gly-Pro-Gly)1-2(Gly-Pro-Pro), (Gly-Pro-Pro)n, (Orn3-Gly)n and also rat skin collagen by X-ray diffraction, circular dichroism and infrared spectroscopy methods; the characteristic shape of the left-handed helix CD spectrum was found. The change of spectral characteristics with the change of left-handed helix distortion was established. The linear noncooperative melting process of the left-handed conformation was demonstrated. The data obtained allow to determine qualitatively the presence of the left-handed helix in different polypeptides and proteins.
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