Raman band assignments of powdered lyophilized interleukin-6.

Wavenumber (cm−1)	Band assignment
708	C–S stretching vibration of cysteine residues32
854	Tyrosine, ring breathing vibration32–35
880	Tryptophan, bending ring33,35,37
938	C–C stretching backbone for α-helix conformation32,33,36,37
1003	Phenylalanine, ring breathing vibration32,33,35–37
1033	C–H in-plane bending mode of phenylalanine33–35,40
1066	C–C skeletal stretching for random secondary conformation33,35,37,40
1128	C–N stretching33–35,40
1205	Ring deformation of tyrosine and phenylalanine33,35,37,40
1261	Amide III with α-helix conformation, involves C–N stretching, N–H in-plane bending vibration of the peptide bond and contributions from Cα–C stretching and C O in-plane bending modes32,33,36,37
1342	Cα–H deformation33,36,37
1448	CH2 and CH3 bending vibrations32,33,38,39
1549	Amide II vibration: N–H in-plane bending and C–N stretching of the trans peptide group32–34,38
1607	Aromatic ring vibration of tyrosine and phenylalanine33,34,37
1655	Amide I with α-helix conformation; C O stretching mode, C–N stretching, Cα–C–N bending and N–H in-plane bending of peptide groups32–36,38
2907	Aliphatic C–H stretching33,38,40
2960	Symmetric and asymmetric C–H stretching modes33,38,40
3330	N–H symmetric stretching33,38,40