106 The Biochemistry of Semen 



developed by Schmidt and Thannhauser (1945) and Schneider 

 (1945, 1946) which are based largely on determinations of phos- 

 phorus and involve the removal of (i) the 'acid-soluble phosphorus 

 compounds' (extraction with cold trichloroacetic acid), and (ii) the 

 phospholipids (extraction with ethanol and ether), prior to the 

 analysis of nucleic acid (see also Table 16). 



The basic nuclear proteins, protamines and histones 



The proteins conjugated with deoxyribonucleic acid are of the 

 basic type and have been shown to be either protamines or histones 

 in most instances so far examined. Protamines have been isolated 

 from fish spermatozoa of several species. Of the various protamines, 

 the best known are salmine from salmon and trout sperm, and 

 clupeine from herring sperm. Much less is known about the other 

 protamines, such as scombrine (mackerel), cyclopterine (lump- 

 sucker), esocine (pike), thynnine (tunny fish), percine (perch), 

 cyprinine (carp) and st urine (sturgeon). 



Judging from the molecular weight and amino acid composition, 

 salmine, clupeine and scombrine have a relatively simple structure, 

 there being approximately two molecules of arginine to one molecule 

 of monoamino acid. Thus, for example, the analysis of salmine 

 sulphate prepared from the spermatozoa of the Spring or Chum 

 salmon (Tristram, 1947, 1949) suggests a molecular weight of about 

 8000, with a total of 58 amino acid residues: 40 arginine, 8 isoleu- 

 cine, 2 valine, 4 proline, 3 glycine, 1 alanine and 7 serine; this sal- 

 mine sulphate contains 19-85% sulphuric acid, i.e. 40 equivalents 

 per molecule, sufficient to combine with all arginine residues. 

 Another salmine sulphate, one prepared from the sperm of the 

 Columbia River salmon (Block and Boiling, 1945) is said to con- 

 tain 67 amino acid residues: 47 arginine, 1 isoleucine, 3 valine, 

 6 proline, 4 alanine and 6 serine (see also: Corfield and Robson, 

 1953). 



The results of formol titration indicate that salmine contains one 

 free amino or imino group per molecule of 8000, and the end group 

 assay carried out by means of the dinitrofluorobenzene method 

 (Sanger, 1952) suggests that the N-terminal position is occupied by 

 the imino group of proline. In clupeine, the A^-terminal position is 

 also taken up by proline, whereas at the other end of the amino acid 



