1.Universit?t Konstanz,Konstanz,Germany;2.Université Louis Pasteur,Strasbourg,France;3.Institut Laue-Langevin,Grenoble,France;4.Universit?t Konstanz,Konstanz,Germany;5.EPSAM/ISTM Research Institutes,Keele University,Staffordshire,UK
Abstract:
We report on the preparation and characterization of wet-spun films of sodium DNA in which intermolecular cross-links were introduced following formaldehyde treatment. Raman scattering shows that the DNA in moderately cross-linked films is mainly in the B conformation. Stretching experiments show a transition from plastic to elastomeric behavior with increasing exposure to the cross-linking agent. Elastomeric DNA films are strongly disordered. X-ray diffraction shows that stretching of moderately cross-linked films under controlled high humidity conditions results in increased molecular orientation as well as the appearance of meridional reflections at 7.4-7.8 and 8.2 A. These reflections are not observed for any of the classical conformations associated with mixed sequence DNA, and may arise from extended base-pair stacking in a stretched DNA structure.