Solubilization and conformation of protamines in reverse micelles

Abstract

Protamines are strong basic nucleoproteins containing approximately 70% L-arginine. In aqueous solution they usually exist as an extended coil as a consequence of the electrostatic repulsion of the positively charged guanidinium side-chain of arginine. Their conformation in the native complex with DNA is, as of yet, unnknown. However, it is suspected to at least partially be an α-helix, due to the electrostatic interactions with the phosphoric acid anions of the DNA and a low degree of hydration. For studying these influences, studies on the conformation of protamines in reverse micelles, e.g., of the system AOT/i-octane/H₂O depending on the H₂O/AOT-ratio (w ₀-value) by circular dichroism (CD)-spectroscopy should be useful. Indeed, at low w ₀-values, α-helix spectra have been obtained, as well as a remarcable dependence of the conformation of the protamines on w ₀. The component YI of clupein shows a significant difference in conformation against YII and Z.