Abstract: Application of a functionalized porous membrane to purify nucleic acids, the binding properties of the membrane with respect to nucleic acids being adjustable by controlling the conditions of an ambient medium. The membrane is functionalized by deprotonated groups.

Abstract: A method for the isolation of nucleic acids from a liquid sample, which contains nucleic acids, using a filtering device, which has pores, through which the sample is allowed to flow in the course of the isolation, the nucleic acids, and contained in the sample, being retained selectively in or at the pores, wherein the sample is mixed with a concentration of the precipitating agent for nucleic acids, which is sufficient to condense the nucleic acids and the sample is then allowed to flow through the filtering device, the pores of the filtering device used having inner wall regions with variable surface structures, which are constructed differently depending on the medium passed through the pores and by which the permeability of the pores can be adjusted between a state, in which the condensed nucleic acid molecules are retained, and a state, in which the dissolved nucleic acid molecules can pass through.