Interpretation of Infrared Dichroism in Fibrous Proteins —the 2μ Region

The assignment of the overtone and combination bands which appear in the infrared spectra of fibrous proteins between 4200 and 5500 cm−1 is discussed on the basis of the normal vibrations of an isolated —CO.NH— group. Equations relating the degree of molecular orientation in a protein fibre with transition moment direction and dichroic ratio are derived and the assignment of the transition moment direction associated with certain vibrations is considered.