Electrometric and Other Studies of Cytochrome c 



379 



From one such TCA-treated cytochrome c sample a small residue was ob- 

 tained after dialysis against 0-5% NaCl which dissolved in 0-02 n NH4OH. 

 This material had an increased ascorbic acid oxidase activity and a somewhat 

 altered absorption spectrum (Fig. 7). This result was variable, however, and 

 generally no residue was obtained. There was thus evidence for the production 

 of more than one fraction by this treatment, which is in agreement with the 



€20 



580 560 540 



Wavelength, m/x 



Fig. 7. Comparison of characteristic absorption spectra of reduced cytochrome 



c samples from ox-heart muscle. Curve ^4: resin-treated sample; curve fl: fraction 



soluble in 0-5% NaCl after 2-5% TCA, for 18 hr, 25°C; curve C: residue after 



TCA treatment, soluble in 0-02 N NH4OH. 



observations of Margohash, Frohwirt and Wiener (1959) who have reported 

 a separation of Fraction II into several other fractions with varying properties. 



Although TCA under various conditions can bring about changes in 

 cytochrome c such as increased susceptibility to proteinase digestion, change 

 in chromatographic behaviour and altered E'q, it seems that with mild treat- 

 ment its biological activity is unaltered (see, for example, Keilin and Hartree, 

 1955). In fact the modified material — as judged by its chromatographic 

 behaviour — may show unchanged properties in biological systems (see, for 

 example, Hagihara et al., 1958a; Yamanaka et al, 1959). 



In connexion with the often-quoted autoxidation and combination with CO 

 as criteria of modification, it is noteworthy that Minakami et al. (1958), 

 after acetylation of the e-lysine residues, obtained a product inactive in the 

 succinic oxidase system and autoxidizable but which showed neither ascorbic 



