Protamine isoelectric point

In the older literature it has already been mentioned that with a weakly alkaline reaction (dilute ammonia) solutions of protamines or histones — which are basic proteins, that is to say, proteins the isoelectric point of which is )> 7 — mixed with solutions of acid proteins" — which are proteins whose isoelectric point is <( 7 — give precipitates which separate out either as flocculi, or as sticky masses or as liquid oil-like" drops... 

Isoelectric point,/ / the pH value of a solution at which the net charge on the dissolved ampholyte is zero, i.e. the sum of the cationic charges is equal to the sum of the anionic charges. The pi of electrolytes, e.g. amino acids, peptides or proteins, may lie in the range from pH 1 ( psin) to pH 11.8 (protamine), and is characteristic for each amphol e. Certain characteristic properties appear at the pi, e.g. a minimal solubility and viscosity. Electrophoretic methods of separation arc based on the differences in the pi of the individual components. The pi. can be determined either electrophoretically at various pH values or by electrofocusing on an ampholine pH adient. 

The isoelectric point of most protamines is about twelve (Miyake, 1927). The values of specific rotation ([ ]d) fot clupeine and salmine are — 83.07° or — 84.0°,... 

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