Structure of transfection-active histone H1/DNA complexes.

Relationships between the structure of transfecting complexes of histone H1 and DNA and their transfection efficiency were studied. Transfection activity proved to be connected to complex aggregates. Low speed centrifugation of the complexes resulted in loss of the transfection activity. The complexes/aggregates were active with high efficiency in a broad range of weight input ratios r(i) (0.1 < r(i) < 30). Using atomic force microscopy (AFM), the complexes were imaged at negative, nearly electroneutral and positive charge conditions. Electroneutral complexes at r(i) = 1 showed a multitude of different complex forms. Fibrillar, network-like and branched structures were frequently present in one complex. Strongly positive charged complexes had a toroidal appearance. All these different forms contributed to the high transfection efficiency. Cellular uptake is supposed to be by phagocytosis.