456 R, W, ESTABROOK 



SUMMARY 



1. The method of recording spectra of samples of haemoproteins cooled 

 to the temperature of liquid nitrogen has been described. 



2. The application of this method of study of the fine band structure of 

 heart muscle cytochrome c, and the modification of the fine band structure 

 by alteration of the protein, has been described. 



3. The spectral properties of reduced cytochromes c, q, c^, c^ as well as b^, 

 h^, b^ and b^ are presented. 



4. The usefulness of the technique for resolving the complexity of the 

 cytochrome complement is illustrated by studies on heart muscle particles, 

 insect flight muscle sarcosomes, and wheat germ mitochondria. 



5. Speculations on the interpretation of modifications of the fine band 

 structure of cytochrome c are discussed. 



A ckno wledgemen ts 



The author is indebted to Dr. Britton Chance for his advice and guidance 

 during the course of these experimental studies. The generosity of many other 

 investigators in supplying samples and materials for study has made many 

 of the experiments reported possible. The constructive criticism of the 

 manuscript by Dr. Walter Bonner is gratefully acknowledged and the 

 assistance of Mr. Patrick Taylor in the spectral analysis is greatly appreciated. 



This research was supported by a Senior Research Fellowship, SF-206-C, 

 of the U.S. Public Health Service. 



1. Recently Dr. Walter Bonner had modified the cuvette holder permitting a more 

 precise and convenient method for recording difference spectra and for assuring the 

 maintenance of the temperature of the sample at — 190°C. 



2. These spectra have been termed 'apparent absolute absorption spectra' to distinguish 

 them from 'difference spectra'. The former describes spectra obtained with turbid samples 

 when an induced turbidity, such as obtained with glycerol water mixtures, is used as a 

 reference. 



3. The nomenclature introduced to describe these spectra identifies by subscripts the 

 various absorption bands discernible at low temperature — numbering from longer to 

 shorter wavelengths and retaining the conventional distinction of a, /3 and y bands and the 

 general classification of a-, b- or c-type of cytochrome. 



4. The sample of the peptide core of cytochrome c was obtained from Dr. Anders 

 Ehrenberg of the Nobel Institute, Stockholm, Sweden. 



5. It is reassuring to report that Dr. Hagihara has examined his samples of crystaUine 

 cytochromes c from a variety of sources and confirms the observation that the yeast 

 cytochrome c differs from cytochrome c obtained from mammalian sources in the manner 

 described here. 



