Abstract <p>Low-frequency Raman bands characterizing vibrations of elements of the secondary structure of fibrillar proteins (keratins) are identified. Experiments with unpigmented human hair are performed in two configurations: with excitation radiation focused coaxially on the hair and perpendicular to it. Based on the sensitivity of polarization, the bands at 150 and 221 cm⁻¹ are attributed to vibrations of the α-helical structures of keratins. The spectral interval of 270–340 cm⁻¹ is attributed to vibrations of β-structures.</p>