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DNA Condensed by Protamine: A "Short" or "Long" Polycation Behavior

DNA Condensed by Protamine: A "Short" or "Long" Polycation Behavior

Adriana C Toma, Marta de Frutos, Françoise Livolant, Eric Raspaud

Biomacromolecules. 2009 Aug 10;10(8):2129-34.

PMID: 19572634

Abstract:

Using centrifugation assay and light scattering measurements, we study the condensation of DNA by the salmon protamine, a highly basic protein carrying 21 positive charges out of 30 amino acids, in the presence of a high amount of monovalent salt. The DNA condensation is followed by a macroscopic phase separation. It occurs while a large amount of polycations remains freely diffusing in the bulk. A similar behavior was described before for small multivalent ions in diluted DNA solution in a lower salt range. Sensitivity to the salt is however amplified when increasing the charge of polycations. Indeed, a high power-law dependence is observed here with an exponent 11. This variation agrees with the power-law dependence that characterizes the binding of small polycations to DNA. In other words, we show that protamines behave like small polycations in the diluted DNA-high salt regime, while they behave like other large polycations in the diluted DNA-low salt regime as shown in a previous study. In addition, instead of the classical view where binding of polycations to DNA is supposed to trigger DNA condensation in low and moderate salt conditions, we propose that, under high salt conditions, the potential presence of a DNA dense phase triggers the binding of protamines to DNA.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP53597254	Protamine sulfate salt from salmon		53597-25-4	Price

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