Arginine structural classification

Histones Small chromosomal proteins (approx 12-20 kD) possessing an open, unfolded structure and attached to the DNA in cell nuclei by ionic linkages. Classification into the various types (designated histone I, histone II, etc.) is based on the relative amounts of arginine and lysine in each. [NIH]... 

At the time these estimates of the basic amino acids seemed a useful contribution to make. A classification of proteins as closely or distantly related is still a desirable goal, but it is fairly certain that proteins having basic amino acid ratios of 1 3 3 and 1 6 15 can be more closely related than two proteins which may both have the same ratio. The efforts did show that the enzyme-resistant protein in the epidermis differed from the similarly resistant protein of the hard keratins in containing relatively much less arginine. They also showed that the ratios for the whole structure did not differ significantly from the ratio for the very small residue left after enzyme treatment. A modern approach would attempt a complete analysis of all amino acids and preferably only on well defined protein species within these structures. 

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