88 The Biochemistry of Semen 



The heads of ram spermatozoa separated by the process of 

 mechanical disintegration can be further freed from hpoprotein 

 and from adhering particles of middle-pieces and tails by repeated 

 washing and differential centrifugation. Preparations obtained in 

 this way consist of sperm-heads only; they were found to contain 

 3 •9-4-3% phosphorus, all of it accounted for by deoxyribonucleic acid, 

 but were free from lipid and acid-soluble phosphorus compounds. 



Protein-bound iron, zinc and copper 



Zittle and Zitin (1942^) found that the total iron content of dried 

 lipid-free bovine epididymal sperm is about 7 mg./lOO g., more iron 

 being present in the middle-pieces and tails than in the heads. Of 

 the total iron, 60% was extractable with pyrophosphate and tri- 

 chloroacetic acid at 100^, and was therefore assumed to be of non- 

 haematin nature; an attempt to identify haematin in the non- 

 extractable portion was unsuccessful. However, with the aid of a 

 spectroscopic method (Mann, 1937, 1938) designed specifically for 



Table 12. Distribution of total iron, zinc and copper in ram semen 

 (Mann, 1945a) 



determination of haematin (as pyridine haemochromogen) in animal 

 and plant tissues, the author was able to detect readily and to deter- 

 mine quantitatively haematin in bull as well as in ram spermatozoa. 

 The distribution in ram semen, of total iron, and also of zinc and 

 copper, is shown in Table 12 (Mann, 1945^). It can be seen that in 

 the ram the concentration of these three elements is much higher 

 in the spermatozoa than in the seminal plasma. With the aid of a 

 Mickle disintegrator, it was possible to separate the heads from the 

 tails and middle-pieces and to obtain sperm-head preparations which 

 contained some iron but were completely free from haematin. On 

 the other hand, the 'homogenates' from disintegrated tails and 



