Shear‐Induced Supramolecular Organization of Calf‐Thymus DNA in Solution: Insights from SAXS Coupled with Rheology

ABSTRACT The investigation of DNA's dynamic and flow properties in solution is crucial for understanding its biological roles. DNA double helix strands interact and, at high concentrations, they form liquid crystalline phases, which are influenced by molecular weight and ionic strength. At rest, Small Angle X‐ray Scattering (SAXS) shows that DNA double helix strands exhibit an electrostatic correlation peak whose intensity decreases in the presence of external salt. In this study, shear‐induced liquid crystalline textures were observed in high molar mass calf‐thymus DNA solutions (CT‐DNA) at concentrations higher than 7 mg/mL using birefringence visualizations and rheology measurements. Then, SAXS, combined with rheology, was used to examine this supramolecular organization under flow, revealing orientations of CT‐DNA with preferential inter‐chain distances. Upon relaxation, a transition from anisotropic to isotropic behavior was observed in those DNA solutions. To summarize, it is shown that CT‐DNA's supramolecular organization at rest is progressively modified under flow and significantly influenced by DNA concentration, shear rate, and ionic strength.