Abstract
The application of the new technique of electron resonance to the investigation of large organic molecules containing paramagnetic atoms is outlined in this paper, together with examples of the information that can be obtained. The various derivatives of haemo- and myoglobins have been chosen as an initial study since the electron resonance data can give detailed information about the haem planes which are inaccessible to normal X-ray and infra-red techniques. Two types of data can be obtained from these measurements, one relating to the nature of electronic binding between the central iron atom and the surrounding ligands, and the other relating to the spatial orientation of the heam planes. These two sets of results are discussed in some detail and compared with the data obtained by other methods. It would appear that electron resonance can be used in such cases as these to give much more detailed and accurate measurements concerning the central structure of the haem group than any other technique.