Table 1 Assignment of the IR bands

Proteins

1780–1480

1635 (Amide I, AmI)

>C=O stretching and C–N bending in amide group of proteins and peptides.

1546 (Amide II, AmII)

N–H bending, C–N stretching of proteins and peptides.

Mixed region

1500–1200

1452

C-H bend in CH₂ and CH₃

1400

>C=O symmetric stretchning of deprotonated COO^- group and C–O bending from COO^-

1234 (nucleic acid, NA)

P=O asymmetric stretching of PO₂^- in phosphodiesters of DNA/RNA

Carbohydrates

1200–900

1169

1121

1080 (polysaccharides, PS)

1057

C–OH stretchning, C–O–C and C–O ring vibrations in polysaccharides and C–P–O stretching