Direct Correlation between Molecular Cross-linking and Macroscopic Mechanical Properties for Green Solids of Deoxyribonucleic Acids

Double-stranded deoxyribonucleic acids (DNAs) were intermolecularly cross-linked using 2,5-hexanedione under reductive amination conditions in aqueous phase. Cross-linking points between DNAs were directly observed by atomic force microscopy in conjunction with a conventional gel electrophoresis analysis. While DNA chains near cross-linking points were denatured, DNA chains not near cross-linking points maintained B-form double strands. A transparent and self-supported film of cross-linked DNA (DNA-c) was obtained by a simple solvent-casting method. The tensile properties of DNA-c films were much better than those of non-cross-linked DNA (DNA-n) films due to the presence of the cross-linking portions. Structural analyses based on wide-angle X-ray diffraction measurements revealed that the reorientation of DNA-c was remarkably restricted by the introduction of cross-linking points.