Knowledge Bank

Since desoxyribonucleic acid (DNA) is generally recognized as the material from which genes are made, its structure is of great biological interest. The most promising model for the structure of DNA cosists of two spirals wound about a common axis and held together by hydrogen bonds between planar bases normal to this $axis.1$ The infrared spectrum of an oriented film of DNA (Na salt) has been obtained between 4000 and $700cm-1$ using polarized radiation. The results obtained will be discussed in relation to the Crick-Watson model. The dichroism of vibrations in the planes of the bases is found to be perpendicular, in agreement with the model. However, the dichroism of certain other vibrations, which are assigned to the phosphate and sugar residues of the spiral chains appears to be higher than would be anticipated from the Crick-Watson model.