Protamines. VII. Circular Dichroism Study of Salmine A I *

Salmine A I, one of the components of the protamine from salmon, has been purified and characterized. The conformational preferences of salmine A I have been examined as a function of pH, added salts, presence o f helix-supporting solvents, and temperature, using circular dichroism. It has been found that this small basic protein adopts predominantly an unordered conformation in aqueous solution. Addition of counter-ions, in particular perchlorate, and 2-chloroethanol induces to various extents the onset of the right-handed a-helical conformation. The results are discussed in comparison with those previously reported on the three main components of clupeine, the protamine from herring, and with the published conformational predictions by various statistical methods.