Abstract: The present invention provides method for isolating DNA molecules having a size above a certain cut-off value from a DNA containing sample, comprising a) contacting the sample with a binding buffer which comprises a chaotropic agent and a buffering agent to provide a binding mixture and binding DNA molecules having a size above the cut-off value to a binding matrix which has a silicon containing surface, wherein the cut-off value is determined by the pH value of the binding mixture; b) separating the bound DNA from the remaining sample; c) optionally washing the bound DNA; and d) optionally eluting the bound DNA from the binding matrix. Said method allows the size selective purification of DNA molecules.

Abstract: The present invention provides a poly(alkylene oxide) polymer based size selective DNA isolation method for isolating DNA molecules having a size above a certain cut-off value from a DNA containing sample, comprising (a) preparing a binding mixture comprising the DNA containing sample, at least one poly(alkylene oxide) polymer and at least one divalent cation, wherein said binding mixture has a pH that lies in the range of 8 to 10 and binding precipitated DNA molecules to a solid phase having an unmodified silicon containing surface, thereby providing a solid phase having bound thereto DNA molecules having a size above the cut-off value, wherein under the used binding conditions DNA molecules having a size which is less than the cut-off value substantially do not bind to the solid phase; (b) separating the bound DNA molecules from the remaining sample; —optionally washing the bound DNA molecules; and —optionally eluting the bound DNA molecules from the solid phase.

Abstract: The present invention provides method for isolating DNA molecules having a size above a certain cut-off value from a DNA containing sample, comprising a) contacting the sample with a binding buffer which comprises a chaotropic agent and a buffering agent to provide a binding mixture and binding DNA molecules having a size above the cut-off value to a binding matrix which has a silicon containing surface, wherein the cut-off value is determined by the pH value of the binding mixture; b) separating the bound DNA from the remaining sample; c) optionally washing the bound DNA; and d) optionally eluting the bound DNA from the binding matrix. Said method allows the size selective purification of DNA molecules.